CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The subject matter of Canadian Patent Application Serial Number 2,787,584 entitled "METHOD FOR CONTINUOUS PREPARATION OF INDIUM-TIN

COPRECIPITATES AND INDIUM-TIN-OXIDE NANOPOWDERS WITH

SUBSTANTIALLY HOMOGENEOUS INDIUM/TIN COMPOSITION,

CONTROLLABLE SHAPE AND PARTICLE SIZE," filed August 22, 2012, is incorporated herein by reference including the materials originally submitted to the Canadian Intellectual Property Office. The entire subject matter of US application 13/671,150, filed November 7, 2012, entitled METHOD FOR CONTINUOUS

PREPARATION OF INDIUM-TIN COPRECIPITATES AND INDIUM-TIN-OXIDE NANOPOWDERS WITH SUBSTANTIALLY HOMOGENEOUS INDIUMATN COMPOSITION, CONTROLLABLE SHAPE AND PARTICLE SIZE, is incorporated herein by reference, including the materials originally submitted to the United States Patent Office. The entire subject matter of US application 61/939,817, filed February 14, 2014, entitled PROCESSES FOR PRODUCING PRECIPITATED PRECURSOR METAL OXIDE NANOPARTICLES, PARTICULATE METAL OXIDE SOLIDS AND USES THEREFOR, is incorporated herein by reference, including the materials originally submitted to the United States Patent Office.

FIELD

[0002] The present disclosure relates to a process for preparing precipitated precursor metal oxide nanoparticle and nano-scale particulate metal oxide solids and uses therefor. SUMMARY

[0003] The disclosure provides a process for producing nano-scale metal oxide particulate solids (nanoparticles] where the produced metal oxide nanoparticles have a constant uniformity of metal oxides ratio. Furthermore, the disclosure provides coating dispersions having said metal oxide particulate solids added thereto which are curable to a substrate, forming a cured layer, where the cured layered confers a physical property. The coating dispersion cured to the substrate, which may be glass, can be used for providing the substrate with opto-electrical properties and/or for enhancing the infrared and near infrared light wavelength transmittance blocking properties of a substrate through which infrared and near infrared light wavelength may otherwise transmit.

[0004] The following presents a simplified summary of various embodiments and aspects of the general inventive concept. This summary is not intended to restrict key or critical elements of the invention or to delineate the scope of the invention which is explicitly or implicitly described in the following description and claims.

[0005] In one aspect, there is a provided a continuous process for preparing precipitated precursor metal oxide nanoparticles having a constant uniformity of desired metal oxide ratio. Accordingly, the process comprises:

a] preparing a seeding solution comprising at a least first metal salt and at a least second metal salt, said metals being provided in a

predetermined ratio and belonging to Groups IIIA, IVA and VA; at least one solubility modifier; and at least one first base in solvent, wherein said at least first metal salt and said at least second metal salt are solubilized;

b) simultaneously and continuously mixing said seeding solution with a second base solution; one with the other to effect precipitation of said precipitated precursor metal oxide nanoparticles in a dispersion having said precursor nanoparticles having uniformity of said desired ratio, size range and shape; and

c] continuously collecting said precipitated precursor metal oxide

nanoparticles from said dispersion.

[0006] In preferred embodiments, the seeding solution has a pH of from about 0 to about 3 and the at least first metal and the at least second metal salt are solubilized to near the onset of precipitation.

[0007] In another aspect, the continuous process includes an additional step, comprising d] drying and calcining said collected precipitated precursor metal oxide nanoparticles so as to obtain a plurality of nano-scale particulate metal oxide solids of constant uniformity of metal oxide ratio having a size range of from about 5 nm to about 200 nm and a general formula of A _x B _y O _z where A and B are said metals, 0 is oxygen and x, y and z represent the respective composition stoichiometry.

[0008] The metal of the at least first metal salt is selected from gallium, indium, antimony and thallium as represented by A and the metal of the at least second metal salt, represented by B is selected from tin, lead and bismuth. In a preferred embodiment, the at least first metal salt is an indium salt and the at least second metal salt is a tin salt. In a second preferred embodiment, the least first metal salt is an antimony salt and the at least second metal salt is a tin salt.

[0009] In preferred embodiments, the at least one solubility modifier is provided in a molar ratio of about 0.75 moles to 2.0 moles per mole of tin in said second metal salt. Furthermore, the at least one first base is provided in a molar ratio of about 0.5 moles to 3.0 moles per mole of tin in said second metal salt

[00010] In preferred embodiments, in the production of precipitated precursor indium tin nanoparticles and nano-scale indium tin oxide particulate metal solids, the tin salt is provided in a ratio about 5% to about 15% to the indium salt.

Furthermore, in preferred embodiments, the precipitated precursor metal oxide nano particles and the plurality of nano-scale particulate metal oxide solids, particularly nano-scale indium tin oxide nanoparticles, have a ratio of indium to tin of about 90:10.

[00011] In another aspect, the temperature and pH is maintained within a predetermined range during said continuous mixing. In a preferred embodiment, during continuous mixing the pH of the dispersion is maintained from about 9 to , about 13 and temperature is maintained at about 20°C to about 50°C and more preferably the pH is maintained at about 12 and the temperature is maintained at about from 20°C to about 24°C so as to produce the plurality of nano-scale particulate metal oxide solids comprised of spherically-shaped nanoparticles having a size range of about 8 nm to about 70 nm. In another preferred embodiment, during the continuous mixing the pH of the dispersion is maintained from about 3 to about 6 and temperature is maintained at about 40°C to about 60°C and more preferably the pH is maintained at about 3.5 and the temperature is maintained at about 50°C so as to produce the plurality of nano-scale particulate metal oxide solids comprised of plate-like-shaped nanoparticles having an average plate dimension of about 60 nm to about 200 nm.

[00012] In another aspect, there is provided a plurality of nano-scale particulate metal oxide solids which have a constant uniformity of desired metal oxide ratio, a particle size range of from about 5 nm to about 200 nm and a general formula of AxByOz where A and B are said metals, 0 is oxygen and x, y and z represent the respective composition stoichiometry.

[00013] In another aspect, there is provided a coating dispersion comprising a plurality of nano-scale particulate metal oxide solids produced in accordance with processes according to the invention described herein, with an acceptable curable compound in an acceptable carrier, the metal oxide particulate solids having a size range of from about 5 nm to about 100 nm. In yet another aspect, there is provided a coating dispersion comprising a plurality of metal oxide particulate solids with an acceptable curable compound in an acceptable carrier, the metal oxide particulate solids having a predetermined constant uniformity of metal oxides ratio, a size range of from about 5 nm to about lOOnm and a general formula of A _x B _y O _z where A and B are said metals in said predetermined ratio, 0 is oxygen and x, y and z represent the respective composition stoichiometry. In preferred embodiments, the metal oxide particulate solids size range is from about 10 nm to about 80 nm and more preferably om about 20 nm to about 50 nm. Additionally, about at least 90% of the metal particulate solids are within the abovementioned size distribution ranges and more preferably at least 99% of the metal particulate solids are within the abovementioned size range.

[00014] With respect to the coating dispersion, the at least first metal salt and the at least second metal are selected where A is selected from gallium, indium, antimony and thallium and B is selected from tin, lead and bismuth. Preferably, an indium salt and a tin salt are used, in one embodiment such that particulate metal solids are indium tin oxide. In another embodiment, an antimony salt and a tin salt are used such that the particulate metal solids are antimony tin oxide.

[00015] The curable compound is a preferably a lacquer and more preferably a urethane or water-based urethane. Most preferably, the curable compound is an acrylic water-based urethane employing non-isocyante cross-linkers. Furthermore, the coating dispersion has a viscosity of from about 18 seconds to about 25 seconds on a #2 Zahn cup measurement and may include ethylene glycol to improve the knitting characteristics of the dispersion when applied to a substrate and allowed to cure. In some embodiments, dispersion agent may also be included to aid in uniformity of dispersing of the particulate metal solids throughout the coating dispersion. Additionally, the coating dispersion may include a defoaming agent, such as for example an emulsion of organo-modified polysiloxanes. [00016] The coating dispersion is curable to a cured layer thickness of from about 5 μΜ to about 20 μΜ. Preferably, the cured layer has a thickness of from about 7 μΜ to about 15 μΜ and more preferably from about 8 μΜ to about 12 μΜ.

[00017] In another aspect, there is provided a process of providing a layer of a cured compound on a substrate to provide enhanced infrared and near infrared light wavelength transmittance blocking properties, the process comprising:

i) applying a coating dispersion as described herein on said substrate; and ii) curing said acceptable curable compound to provide said cured layer on said substrate.

[00018] In yet another aspect, there is provided a coated substrate having a cured layer adhered thereto. The coated substrate has enhanced infrared and near infrared light wavelength transmittance blocking properties. The cured layer comprises a plurality of nano-scale particulate metal oxide solids entrained therein where the particulate metal oxide solids have a predetermined constant uniformity of metal oxides ratio and a general formula of A _x B _y O _z where A and B are said metals in the predetermined ratio, 0 is oxygen and x, y and z represent the respective composition stoichiometry and the nano-scale particulate metal oxide solids have a size distribution of from about 5 nm to about 100 nm and said cured layer having a thickness about 5 μΜ to about 20 μΜ .

[00019] In some embodiments, the cured layer thickness of from about 5 μΜ to about 20 μΜ. Preferably, the cured layer has a thickness of from about 7 μΜ to about 15 μΜ and more preferably from about 8 μΜ to about 12 μΜ. In preferred embodiments, cured layer is able to withstand a 2H pencil hardness test.

[00020] In preferred embodiments, the process of providing a layer of the cured compound on the substrate comprises electrostatic deposition of said coating dispersion on said substrate. Furthermore, in some embodiments, the substrate is glass or other substrate through which light may transmit. The glass or other substrate through which light may transmit may be installed in a window frame. The process, in such embodiments comprises

i) releasing the dispersion from an electrostatic spraying apparatus as a turbulent flow sufficient to cause a cloud having droplets of the coating dispersion of a desired size range migratable to said substrate so as to provide a curable layer; and

if) curing the curable layer on the substrate as the cured layer.

In some embodiments, the process also includes providing successive clouds of the coating dispersion released from the electrostatic spraying apparatus so as to form successiye local regions of the coating dispersion on the substrate in a wet edge to wet edge process to form said cured layer.

[00021] In yet another aspect, there is provided a coated substrate having a cured layer adhered thereto. In some embodiments, the coated substrate is glass other substrate through which light may transmit. The cured layer has infrared and near infrared light wavelength transmittance blocking properties. The cured layer includes a plurality of nano-scale particulate metal oxide solids, as described herein, entrained therein. In some embodiments the cured layer includes a plurality of nano-scale particulate metal oxide solids entrained therein where the particulate metal oxide solids have a predetermined constant uniformity of metal oxides ratio and a general formula of A _x By0 ₂ where A and B are said metals in said

predetermined ratio, 0 is oxygen and x, y and z represent the respective

composition stoichiometry. The nano-scale particulate metal oxide solids have a size distribution of from about 5 nm to about 100 nm and the cured layer has a thickness about 5 μΜ to about 20 μΜ. Preferably, the cured layer has a thickness of from about 7 μΜ to about 15 μΜ and more preferably from about 8 μΜ to about 12 μΜ. Preferably, the plurality of nano-scale particulate metal oxide solids are indium tin oxide nanoparticles in one embodiment and in another embodiment, the plurality of nano-scale particulate metal oxide solids are antimony tin oxide nanoparticles.

[00022] In preferred embodiments the nano-scale particulate metal oxide solids have a particle size distribution of from about 10 nm to about 80 nm. More preferably, the nano-scale particulate metal oxide solids have a particle size distribution of from about from about 20 nm to about 50 nm. Additionally, in preferred embodiments, about at least 90% of the nano-scale particulate metal oxide solids are within the abovementioned size distribution ranges and more preferably at least 99% of the nano-scale particulate metal oxide solids are within the abovementioned size range. The coated substrate, in preferred embodiments, has as a solar heat gain coefficient of from about 0.5 to about 0.8, a visible light transmittance of from about 70% to about 90%, a solar light reflectance of from about 5.5% to about 9% and/or is able to withstand a 2H pencil hardness test.

[00023] In some embodiments, the cured layer is applied to the substrate to form the coated substrate as liquid coating dispersion including urethane or a water-based urethane.

[00024] In another aspect, indium tin oxide precipitated precursor

nanoparticles produced by the continuous process as described herein is provided, wherein at least 70% of said precipitated indium tin oxide precursor nanoparticles have the same ratio of indium to tin as in said seeding solution. Furthermore, there is also provided indium tin oxide particulate solids produced by the continuous process as described herein wherein at least 70% of said precipitated indium tin oxide particulate solids have a common indium to tin ratio. Preferably, about 90% to about 99% of the indium tin oxide precipitated precursor nanoparticles or indium tin oxide nano-scale particulate solids have a common indium to tin ratio. In preferred embodiments, the ratio of indium to tin is about 90:10. Additionally the indium tin oxide particulate solids have a particle shape selected from spherically- shaped particles and plate-like-shaped particles.

[00025] In some embodiments, the nano-scale indium tin oxide particulate solids, which when entrained in a cured layer on a glass substrate or other substrate through which light may transmit, block at least 50% of near infrared light wavelengths of 1100 nm or greater. Furthermore, the nano-scale indium tin oxide particulate solids, which when entrained in a cured layer on a glass substrate or other substrate through which light may transmit, block at least 90% of near infrared light wavelengths of 1400 nm or greater. In a preferred embodiment the nano-scale indium tin oxide particulate solids are provided in the cured layer at concentration about 6% (weight/weight) and the cured layer has a thickness about 6 microns.

[00026] In another aspect, there are provided ςοηίίηυο^Γ/ produced indium tin oxide particulate solids produced according to the process as described herein, characterized in that at least 90% of the indium tin oxide particulate solids have a common indium to tin ratio within a measurement error of +/- 10%.

BRIEF DESCRIPTION OF THE FIGURES

[00027] In order that the invention may be better understood, aspects and preferred embodiments, will now be described, by way of example only, with references to the accompanying figures wherein:

[00028] Figure 1 is a schematic representation of an exemplary apparatus for continuously producing precipitated precursor metal oxide nanoparticles having a desired constant uniformity of metal oxide ratio;

[00029] Figure 2 is a representative X-ray Diffraction plot of nanoparticles of ITO produced according to conditions described in Examples 1 to 7;

[00030] Figure 3 is a SEM image of plate-like shaped indium tin oxide nanoparticles synthesized according to the conditions described in Example 2;

[00031] Figure 4 is a SEM image of spherically-shaped indium tin oxide nanoparticles synthesized according to the process described in Example 1; [00032] Figure 5 is an percent transmission versus light wavelength plot of a cured layer on glass having indium tin oxide nanoparticles synthesized using the continuous process described in Example 1 having a predetermined constant uniformity of metal oxide ratio entrained therein;

[00033] Figures 6a and 6b are plots of the percentage of tin doping levels versus time of nanoparticles synthesis according to the continuous process and the conventional process, respectively, as described in Example 8;

[00034] Figures 7 to 14 are plots of spectral properties of glass substrates having the coating dispersion cured thereto of Samples 1 to 8 corresponding to Example 9;

[00035] Figure 15 is an overlay X-ray Diffraction plot of batches 5 to 9 of a coating dispersion cured to a glass substrate corresponding to Example 10, having indium tin oxide nanoparticles;

[00036] Figure 16 are Scanning Electron Microscope photographs (SEM) of batches 5 to 9 showing indium tin oxide nanoparticle dispersions cured to glass to form a coated substrate corresponding to Example 11.

[00037] Figure 17 is a schematic representation of an exemplary on-site electrostatic coating apparatus;

[00038] Figure 18 is schematic flow diagram of an exemplary on-site method for electrostatically applying a coating dispersion to a surface; and

[00039] Figure 19 is schematic representation of an exemplary embodiment of the coating dispersion being applied via a coating dispersion cloud to target surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS [00040] In an exemplary embodiment, a continuous process for preparing precipitated precursor metal oxide nanoparticles is provided where said

nanoparticles have a constant uniformity of desired metal oxide ratio. The precipitated precursor metal oxide nanoparticles in another aspect of the invention may be separated from the solvent used in the continuous process and dried and calcined to obtain a plurality of precipitated metal oxide solids having the desired predetermined metal oxide ratio. Such metal oxides in another aspect are included in a coating dispersion which is curable, for instance on a substrate. The coating dispersion includes a plurality of the rnetal oxide particulate solids having a constant uniformity of metal oxides ratio with an acceptable curable compound in an acceptable carrier. The particulate metal oxide solids can also be produced according to the process to have a desired particle size range and shape. Such metal oxide particulate solids have improved optical and electrical properties owing to improved consistency and reliably with regard to the metal oxide ratio in the final product as discussed below.

[00041] Briefly, the process described herein comprises preparing a seeding solution including at least first metal salt, at least second metal salt, at least one solubility modifier and at least one first base in a required amount of a solvent such as, for example, water so as to form intermediate metal compounds. The at least first metal salt and the at second metal salt are provided in a predetermined ratio and the metals of the salts belong to Groups IIIA, IVA and VA. In the seeding solution, the metal salts have a general formula which may be expressed as

[M(OH) Cy], where M is a metal ion of the first or second metal salt, and C is the cationic part of the at least first metal salt or the least one second metal salt, x is a number greater than 0 and y=[M*valance-x]/C* valance.

[00042] The metals comprising the at least first metal and the at least one second metal salt, as noted above, are selected from Group IIIA, IVA and VA.

Suitable metals for the first metal salt are thus gallium, indium, antimony and thallium. Suitable metals for the second metal salt are thus tin, lead and bismuth. In preferred embodiments, the at least first metal is provided as a salt of indium or antimony and the at least second metal salt is provided as a salt of tin. Once the precipitated precursor metal oxide nanoparticles are dried and calcined, to form the nano-scale particulate metal oxide solids, such metal oxide solid have a general formula of A _x B _y O _z where A and B are said metals, 0 is oxygen and x, y and z represent the respective composition stoichiometry. The particulate metal oxide solids have size range from about 5 nm to about 200 nm.

[00043] The seeding solution is provided as an optically clear solution with no visible opacity so as to ensure that the metals of the now hydrolyzed metal salts remain in the seeding solution as unprecipitated compounds and that the precipitation only occurs in the reaction vessel when the metal intermediate compounds react with additional base. The at least one solubility modifier is provided such that the pH of the seeding solution can be adjusted and maintained to near the onset of precipitation for both the at least first metal and the at least second metal and so that one of the metals does not precipitate prior to the other owing to the at least one first base in the seeding solution. Solubility modifying agents or solubility modifiers suitable for use in producing the seeding solution may, for example, be compounds containing carboxylic acid, hydroxyl -acid, amine, amide or mixtures thereof or any other compounds which may enhance the solubility of the metals in presence of the at least one first base. In some

embodiments the solubility modifying agent compounds may be do-decyl amine, decylamine, tartaric acid, citric acid, β-alanine, methyl amine, ethyl amine, n- and i- propyl amine, butyl amine and poly-ethylene amine. In preferred embodiments the solubility modifier is provided as caprolactam and/or nonanolactam.

[00044] In preferred embodiments, as noted above, when the at least first metal is indium or antimony and the at least second metal is tin, the solubility modifier is provided as caprolactam and/or nonanolactam and at a concentration of from about 0.75 moles to about 2.0 moles per mole of tin. Furthermore, the molar ratio of the at one first base to tin in the seeding solution is from about 0.5 to about 3.0

[00045] In preferred embodiments, the seeding solution is prepared at temperature of from about 20°C to about 60°C and then aged for a time period of from about 0.5 hours to about 24 hours. The seeding solution, in preferred embodiments, is prepared from indium and tin salts in water, one or more solubility modifiers and the at one first base. Furthermore, in preferred embodiments, the seeding solution has a pH of from about 0 to about 3. However, other solvents, aside from water, such as for example alcohols, may be used as would be readily apparent

« 4 to a person of ordinary skill in the art

[00046] The seeding solution is then simultaneously and continuously introduced into a reactor vessel and mixed with a second base solution, one with the other to effect precipitation of the precursor metal oxide nanoparticles in a dispersion. The second base solution is continuously introduced into the reaction vessel such that the intermediate metal compounds, that is the metals complexed with the solubility modifiers co-precipitate. Thus in a preferred embodiment, the indium and tin metal oxide precursors co-precipitate in a dispersion and are collected therefrom. The introduction of the second base solution and the seeding solution into the reactor vessel is controlled at an adjustable rate, such that the pH of the resultant reaction mixture in the reaction vessel is maintained at greater than 3, and that the ratio of unprecipitated or unreacted intermediate indium and tin compounds is maintained substantially constant.

[00047] Turning now to the preferred embodiment of producing precipitated precursor indium and tin nanoparticles, the seeding solution and the second base solution are simultaneously and continuously introduced and mixed, one with the other in the reaction vessel under substantially constant reaction conditions. In the reaction vessel, the temperature and pH as well as the ratio of reacting indium-to-tin compounds are held substantially constant. The seeding solution and the second base solution are introduced in the reaction vessel via inlet feeds. Additionally the reaction vessel is a stirred tank reactor equipped with mechanical stirrer. In some embodiments, a thermal jacket is provided to control the temperature of the contents of the reaction vessel.

[00048] Indium compounds suitable for use in producing the seeding solution may, for example, be indium chloride; indium iodide; indium nitrate; indium acetate; indium sulfate; indium alkoxides, such as indium methoxide, ethoxide or mixtures of thereof, where the indium is present in the +3 oxidation state or, in the instances of chloride and iodide, in the +1 oxidation state. Tin compounds suitable for use in producing the seeding solution may, for example, be tin chloride; tin sulfate; tin nitrate; tin alkoxides, such as tin methoxide and tin ethoxide or mixtures of thereof, where tin is present in the +4 or +2 oxidation states.

[00049] In preferred embodiments, the indium and tin compounds for making the seeding solution are indium trichloride [InCh] and tin (IV] chloride.

[00050] The at least one first base and the second base solution may be selected from sodium hydroxide; potassium hydroxide; ammonium hydroxide;

tetramethylammonium hydroxide; ammonia; and/or primary, secondary and tertiary aliphatic and/or aromatic amines and/or mixtures thereof. In preferred embodiments, the base for making base solution is ammonium hydroxide and prepared and kept at a substantially constant temperature of from about 20°C to about 60°C. Furthermore, the pH of the base solution may be provided at a pH of from about 10 to about 14.

[00051] The produced nano-scale indium tin oxide particulate solids comprise about more than 99%, for example from about 99% to about 99.99%, pure indium tin oxide having a substantially homogenous composition in terms of the particle size range, particle shape and indium-to-tin ratio with less than 1%, for example from about 1.0% to 0.001% of impurities.

[00052] The seeding solution and the second base solution, feeding

continuously into the reaction vessel, have a substantially constant pH, and are provided at a substantially constant temperature, which is also maintained in the reaction vessel as the reaction proceeds. Furthermore, the ratio of indium to tin compounds is maintained substantially constant throughout the reaction time owing to the continuous feeding into the reaction vessel of reacting components. The amount of seeding solution and the second base solution are simultaneously fed into the reaction vessel, such that they may replace depleting reacting compounds, thus keeping the reactant concentrations constant throughout reaction, such that the ratio of indium to tin in the resultant precipitated precursor indium- tin nanoparticles is consistent, unlike that in batch processes, as is shown below in the examples, with particular reference to Example 8. The residence .time of the precipitation, for a given particle, for example, in the reactor vessel may be from about 15 minutes to about 300 minutes. In preferred embodiments, the residence time in the reaction vessel for the precipitated precursor metal oxide particulate solids is from about 30 minutes to about 120 minutes. Furthermore, the same selected base as used in the second base solution may be used to maintain pH substantially constant during the residence time, if required.

[00053] During mixing of the seeding solution with the second base solution to reaction solution, to from the dispersion, the reaction solution is kept in the mixing reactor vessel at a stirring rate of 200 rpm to about 700 rpm. The temperature of reaction solution furthermore is maintained in the range of from about 20°C to about 60°C and at a desired, but substantially constant, pH. For example the pH of the reaction solution may be kept at about greater than 3 units. Additionally, the seeding solution and the second base solution, as added to the reaction vessel and react to form precipitated precursor indium-tin nanoparticles may have a residence time in the reaction vessel of from about 15 minutes to about 300 minutes and in preferred embodiments from about 30 minutes to about 120 minutes, so as to allow the precipitation reaction to proceed with the required degree of mixing.

[00054] The resulting dispersion is then collected in a collecting tank for additional treatment and pH adjustment, if required. In the collecting tank, the pH is kept substantially constant from about pH 10 to about pH 14 and the temperature is maintained in the range of from about 20°C to about 60°C. Furthermore, the pH of the dispersion in the collecting tank may be adjusted as desired using a base such as ammonium hydroxide.

[00055] In some embodiments, the contents of the collecting tank may be stirred at a rate of from about 200 rpm to about 700 rpm and for a time period of from about 30 minutes to about 24 hours.

[00056] The resultant precipitated precursor indium-tin nanoparticles, having a substantially consistent indium-to-tin ratio throughout the continuous reaction process, are useful in the production of indium tin oxide particulate solids. Such particulate solids, also termed nanoparticles or powders herein, that have a substantially consistent indium-to-tin ratio which is predetermined by the ratio of the metals in the first metal salt to the second metal salt as provided in the seeding solution. For example, such nanoparticles may be used for making suspensions, dispersions and powders therefrom. As a result of the consistent ratio of indium to tin in the produced indium-tin nanoparticle precursor precipitate, indium tin oxide suspensions, dispersions and powders containing the nano-scale particles may show improved, or more consistent optical and electrical performance since the particles have a substantially consistent ratio of indium-to-tin, unlike in

conventional processes where the ratio of indium-to-tin in the resultant particles varies from those produced from when the reaction is commenced to those produced from just before the reaction is completed. A comparison of the ratio of indium-to-tin versus time with regard to the continuous process of the instant disclosure and a conventional process is shown in Table 1 of Example 8, below and in Figures 6a and 6b respectively.

[00057] The formed precipitated indium tin oxide precursor nanoparticles are washed and dried. The solid content, that being the so-formed precipitated precursor indium-tin particulate solids in dispersion may be from about 10% to about 50%. Precipitated precursor indium tin oxide nanoparticles can be separated from the solvent by means of filtration, evaporation, centrifugation, freeze drying, or spray drying at a required temperature.

[00058] The cleaned nanoparticles are heat-treated and/or calcinated in the air and/or followed by heat-treatment under reducing conditions produce the desired ITO nanopowders having a substantially consistent predetermined indium-to-tin composition ratio. Following washing and drying, the solids content, that being the indium-tin nanoparticles, may be dried under air at temperatures of from about 120°C and to about 200°C, under vacuum. The resultant indium-tin dried nanoparticles may then be later heat-treated under air at temperatures of at least 250°C and less than about 800°C to produce yellow indium tin oxide.

[00059] The above heat treatment of the indium-tin precipitated nanoparticles at the aforementioned temperatures may be performed over a time period of from about 0.5 hours to about 8 hours. In some embodiments the time period is from about 0.5 hours to about 3 hours, wherein preferred embodiments, the time period is about 45 minutes.

[00060] In some embodiments the heat treatment or calcination of the precipitated indium tin oxide precursor is performed under reducing conditions where the temperature is from about 250°C to about 400°C and over a time period of about 0.5 hours to about 8 hours to produce blue indium tin oxide nanoparticles. In preferred embodiments, the time period for the heat treatment under reducing conditions is from about 4 hours to about 6 hours and in further still preferred embodiments about 3 hours. Furthermore, for example, the reducing conditions may be provided through the use of a 3% to 10% H ₂ /Ar gas blanket, with a gas flow rate of from about 300 mL/min to about 500 mL/min.

[00061] The indium tin oxide, in addition to having a substantially consistent indium-to-tin ratio, may also have a desired predetermined particle size range and particle shape, as discussed below.

[00062] In an aspect, the process may be tuned or adjusted for preparing a powder of indium tin oxide wherein the metal oxide particulate solids have a spherical particle shape or a plate-like particle shape. Therefore according to an embodiment, the reaction dispersion conditions are adjustable such that the resultant indium tin oxide nanoparticles have a desired particle size range, particle shape and substantially consistent indium-to-tin ratio. For example, the indium tin oxide nanoparticles may be spherical, oblong, or plate-like wherein the average particle size range is from 10 nm to 200 nm.

[00063] According to an embodiment of the process described herein, plate-type nanoparticles may be produced where the pH of reaction dispersion is kept substantially constant in the range of from about 3 to about 6 and in some embodiments, from about 3.5 to about 5.5, and the temperature is maintained in the range of from about 40°C to about 60°C and in some embodiments, at about 50°C. The pH of mixture in the collecting tank is maintained in the range of from about 9 to about 10. In a preferred embodiment for producing plate-like-shaped indium tin oxide particulate metal solids, the pH is maintained at about 3.5 and the

temperature is maintained at about 50°C.

[00064] According to exemplary processes described herein, spherical nanoparticles may be produced where the pH of reaction dispersion is kept substantially constant in the range of from about 9 to about 13 and in some embodiments, from about 9.5 to about 12 and the temperature is maintained at from about 20°C to about 50°C and in some embodiments at room temperature (from about 20°C to about 24°C]. The pH of the mixture in the collecting tank is maintained at from about 9 to about 13. In a preferred embodiment for producing spherically-shaped indium tin oxide particulate metal solids, the pH is maintained at about 12 and the temperature is maintained at about 20°C to 24°C.

[00065] Therefore, as is shown, for example in Examples 1 to 7 below, the particle shape and size range may be selected dependent on the solubility modifier chosen for the seeding solution and the pH of the precipitation reaction and the reaction temperature. The indium tin oxide particulate solids, produced as disclosed herein, have a crystalline phase where in a majority fraction is crystalline in the form of cubic indium tin oxide.

[00066] Dependent on the reaction conditions used in the process as disclosed herein, the desired shape and particle size range of the obtained nanopowders of indium tin oxide include, as at a least major portion, cubic crystalline formed indium tin oxide nanoparticles with a particle size ranging from about 15 nm to about 26 nm. The reactions may be further characterized in that, independent of the precipitation conditions, the precipitated precursor indium-tin nanoparticles at a given moment in the reaction vessel, that being in the mixture, have a substantially homogenous indium-to-tin ratio substantially equal to the molar contents in the original seeding solution. For example, at a given point throughout the reaction process the precipitated precursor indium-tin nanoparticles have a substantially homogenous composition, as verified by EDX analysis, as is shown in Figure 2, for example, and discussed in Examples 1 to 7, equal to the molar ratios present in the seeding solution. In particular preferred embodiment, the tin-to-indium ratio, based on the weight of indium and tin in the seeding solution, may be from about 0.09 to about 0.11 as shown in Table 1 of Example 8, for example. However other ratios are possible depending on the ratios in the seeding solution, for example X percent tin by weight, where X is chosen from a number of between greater 0 to less than 100 percent tin in the seeding solution. For example, the proportion of tin, based on the sum of indium and tin in the seeding solution may be, from about 2% to about 20%, by weight and likewise the proportion of indium, based on the sum of indium and tin in the composition, may be, for example, from about 80% to about 98%, by weight. In some instances the proportion of indium to tin may be from about 88% to about 95%, by weight with the proportion of tin correspondingly being from about 5% to about 12%, by weight. Furthermore, the sum of the indium and tin portions may be at least 99.99%, by weight, of the mass of the resultant ITO.

[00067] With reference to Figure 1, an exemplary schematic embodiment is shown representing an exemplary continuous process apparatus for the continuous precipitation so as to obtain precipitated precursor indium-tin nanoparticles in a dispersion having a constant uniformity of metal oxide ratio. First feed tank 10 provides a variable continuous flow rate, via a first flow controller 20, of a seeding solution prepared as discussed above. The seeding solution is fed to the reaction vessel 12 via a tube in fluid communication therewith. Similarly a second feed tank 14 provides the second base solution at a continuous variable flow rate, via second flow controller 22, to the reaction vessel 12 via tubing in fluid communication with the reaction vessel. The second base solution is provided, as noted above, for adjusting the pH of the reactant mixture as desired, and for initiating the

precipitation reaction. The dispersion is continuously stirred by, for example, a mechanical stirrer 11 so as assist the seeding solution, including the intermediate metal compounds, and the second base solution to react so as to form, by way of precipitation, the precipitated precursor metal oxide particulate solids in

dispersion. As noted above, the feed rates of adding the seeding solution and the second base solution to reactor are adjusted so that the precipitate may have a residence time in the reaction vessel of from about 15 minutes to about 300 minutes so as to allow the precipitation materials to proceed with the desired level of mixing. As the seeding solution and the second base solution enter reactor they react, one with the other, substantially immediately to form the precipitated precursor metal oxide nanoparticles. Given that the process is a continuous process, as more of the seeding solution and second base solution are added to the reaction vessel 12 and precipitated precursor metal oxide nanoparticles in the dispersion are produced, the collecting tank 16 is located to receive overflow 13 of the precipitate-containing dispersion. The collected precipitated precursor metal oxide nanoparticles are then, as desired, removed from the collecting tank 16, washed and dried prior to the heat treatment steps. The reaction vessel 12 is also equipped with a heating/cooling jacket 18 to allow control of the temperature of the mixture in the reaction vessel 12, as required.

[00068] Nano-scale particulate metal oxide solids having constant uniformity of metal oxide ratio resultant from calcination of the precipitated precursor metal oxide nanoparticles, the may then be further prepared in a dispersing unit having added thereto liquid constituents or solvents to break-up any agglomerations of the nanoparticles. In some embodiments the solvent may be optionally removed in order to obtain a metal oxide nanopowder with desired milled characteristics.

[00069] Dispersing apparati suitable for use in the process may include mills, kneaders, roll mills, and/or high energy mills in which two or more dispersing streams collide with one another at pressures of from about 1000 bar to about 4000 bar. In particular, planetary ball mills, stirred ball mills, mortar mills and/or three roll mills may be desirable. Additionally, dispersion by means of ultrasound is likewise suitable.

[00070] As noted above, the preparation in the dispersing unit may be carried out with addition of one or more liquid constituents or solvents. Suitable liquid constituents may be: water; alcohols, for example, methanol ethanol, n- and isopropanol and butanol; glycols and glycol esters, for example ethylene glycol, propylene glycol, or butylene glycol, the corresponding di-, tri-, tetra-, penta-, or hexamers and the corresponding mono- or diethers, where one or both hydroxyl groups are replaced by, for example, a methoxy, ethoxy, propoxy, or butoxy group; ketones for example acetone and butanone; esters, for example ethyl acetate; ethers, for example diethyl ether, tetrahydrofuran, and tetrahydropyran; amides, for example dimethylacetamide and dimethylformamide; sulphoxides and sulphones, for example sulpholane and dimethyl sulphoxide; aliphatic hydrocarbons for example pentane, hexane and cyclohexanone; polyols, for example 2-methyl-2,4- pentanediol; polyethylene glycols and ethers thereof, such as diethylene glycol, diethylene glycol, tetraethylene glycol, diethylene glycol diethyl ether, tetraethylene glycol dimethyl ether or diethylene glycol mono butyl ether; ethylene glycol;

diethylene glycol; diethylene glycol mono butyl ether; 3,6,9-trioxadecanoic acid; beta-alanine; polyoxyethylene(20); Tego 752W; Disperbik 192; sorbitan

monooleate; caprolactam; citric acid; glycolic acid and/or malic acid. Furthermore, in some exemplary embodiments, mixtures of solvents, such as those noted above, may be used.

[00071] In some embodiments, a well-dispersed indium tin oxide paste is prepared in the dispersing unit and may further include adding a mixture of surfactant agents and/or other additives. The indium tin oxide paste as disclosed herein comprises a viscose dispersion of indium tin oxide having, on a

weight/weight (w/w) basis, an indium tin oxide nano-scale particulate solids concentration of from about 10% to about 80%. The one or more surfactants, and/or agents acting in a similar fashion is provided in a concentration range of from about 2% to about 40% w/w relative to the total mass of the ITO nano-scale particulate solids. Preferred surfactants include water-soluble small molecules, cationic surfactants, anionic surfactants, non-ionic surfactants, amphoteric surfactants, oligomers and/or polymers having acid, base, ether, amine, ester and other water soluble functional groups and/or a mixture of these and other functional groups. Furthermore, suitable surfactants may, for example, be cationic, anionic, non-ionic and amphoteric surfactants, polyethylene oxide derivatives where such derivatives may be saturated or unsaturated (mono) carboxylic acids, for example, with the carboxylic acids having more than 7 carbon atoms, preferably more than 11 carbon atoms, for example polyethylene oxide derivatives with stearic acid, palmitic acid or oleic acid. Other polyethylene oxide derivatives may have sorbitan esters, in which case useful carboxylic acids may include, for example, those mentioned above. In addition, it may be possible to use polyethylene oxide (mono)alkyl ethers, for example with alcohols having more than 7 carbon atoms, and in some instances, more than 11 carbon atoms. In some embodiments, for example, organic carboxylic acids, anhydrides or acids amides may be desirable and/or the use of copolymers of ethylene glycol-maleic acid as a surfactant.

Therefore, in some exemplary embodiments, there is provided a dispersion comprising a surfactant and indium tin oxide nanopowder formed into a paste. [00072] In another aspect, the well-dispersed indium tin oxide paste, as noted above, may be incorporated into coating dispersions to provide infrared and near infrared wavelength blocking properties to substrates when cured on a substrate. Also, the particulate metal solids may be incorporated into a coating dispersion independent of first being first formed into a paste.

[00073] The coating dispersions comprise a plurality of metal oxide particulate solids with an acceptable curable compound in and acceptable carrier, for example a lacquer. The metal oxide particulate solids have a constant uniformity of metal oxides ratio stemming, for example, from the above-disclosed process, with a size range of from about 5 nm to about 100 nm. In preferred embodiments the metal oxide particulate solids size range is from about 10 nm to about 80 nm and most preferably from about 20 nm to about 50 nm. Furthermore, in preferred

embodiments, the metal oxide particulate solids are indium tin oxide or antimony tin oxide or mixtures thereof.

[00074] When cured on a substrate, the coating dispersions cure to a durable clear, substantially transparent finish and provide the substrate with infrared and near infrared light wavelength blocking properties. Therefore forming a cured layer.

[00075] In preferred embodiments, metal oxide particulate solids are mixed with a dispersion agent, with or without a defoaming agent, to form an intermediate solution or, in some instances, an intermediate slurry or paste, which is added to the acceptable curable compound in an acceptable carrier. Preferably, the acceptable curable compound is urethane and most preferably an acrylic water-based polyurethane and is polymerizable to a cross-linked polyurethane composition. Therefore the coating dispersion is prepared by forming a slurry or paste containing a plurality of metal oxide particulate solids and adding the paste to the acceptable curable compound in an acceptable carrier to form a final w/w of about 5% to about 25% content paste in the coating dispersion. In a preferred embodiment, about 5% w/w of the metal oxide particulate solids/dispersion agent slurry is formed in the curable coating dispersion. In some embodiments from about 0.4% w/w to about 1.5% w/w defoaming agent is optionally added to the metal oxide particulate solids/dispersion agent slurry and then thoroughly mixed with the acrylic water- based urethane to form the coating dispersion. In this case, the metal oxide particulates solids, such as ATO or ITO may be provided in a number of forms suitable for forming a cured layer on a substrate. For instance, the ATO or ITO or other particulate metal oxide solids are be provided as nano-scale particles wherein, for example, about 90% of the nano-scale ITO or ATO particles provided have a size range of from about 5 nm to about 100 nm, preferably from about 20 nm to about 50 nm. In preferred embodiments, about 99% of the nano-scale ITO or ATO particles are within the aforesaid size ranges. An isocyanate or a non-isocyanate cross-linking agent constituent is added to the coating dispersion in order to react with the urethane to form cross-linked polyurethane, if desired, to speed-up the rate of curing of the applied water-based coating, in preferred embodiments. However, in preferred embodiments, an acrylic water-based urethane is used as the acceptable curable compound, along with water-borne non-isocyanate cross-linkers having from about 10% to about 25% propylene glycol content. Other water-based, non-isocyante containing cross-linkers may also be suitable, thus resulting in an isocyanate-free coating dispersion formable to a cured layer. Therefore a nano- particulated indium tin oxide or antimony-tin-oxide nanopowder-containing water- based coating dispersion is provided for use in the coating of glass or other substrates so as to provide solar heat-shielding properties to the glass by way of reflection and absorption of infrared and near infrared light wavelengths. Such coating of the glass substrate may be accomplished using a variety of coating techniques and methods for applying the coating dispersion to the glass.

[00076] With regard to the abovementioned dispersion agent, several suitable dispersion agents may be used in the formation of the slurry or paste. For example suitable dispersion agents may be a solution including one or more of a modified polyacrylate in dipropylene glycol and water also having about a 4.4% l-butoxy-2- propanol component, a solution of non-ionic fatty acids, modified vegetable oils, a solution of a modified polyacrylate in dipropylene glycol ether and water also having a greater than about a 10% l-(2-methoxymethylethoxy propanol

component, a solution of a modified polyacrylate in dipropylene glycol ether and water also having a greater than about a 10% 2-(2-methoxymethylethoxy propanol component, an aqueous polymer solution, an aqueous polymer solution with pigment affinitive groups, an aqueous carboxylic acid-co-polymer salt solution, an aqueous modified polymer solution, an aqueous modified polymer solution with pigment affinitive groups and/or an aqueous preparation of surface active polymers.

[00077] With regard to the abovementioned defoaming agent, several suitable defoaming agents may be used in the formation of the slurry or paste. For example suitable defoaming agents may include one or more of an emulsion of organo- modified polysiloxanes, an emulsion of organo-modified polysiloxanes having from about a 1% to about 5% a-octadecyl-w-hydroxy-poly(oxy-l,2-ethanediyl component, an emulsion of polyether and polyethersiloxane (having a component including less than about 0.0001% 2,6-bis(l,l-dimethyenthyl]-4-methyl phenol, less than about 0.05% 2-amino-ethanol, less than about 0.0001% cyclohexane, less than about 0.0001% ethanol, and from about 1% to about 5% a-octadecyl-w-hydroxy- poly(oxy-l,2-ethanediyl ), or an emulsion of organo-modified polysiloxanes (having a component including less than about 0.000% 2,6-bis l,l-dimethylethyl)-4-methyl- phenol, from about 1% to about 5% a-octadecyl-w-hydroxy-poly(oxy-l,2- ethanediylj, less than about 0.01% 2-amino-ethanol, less than about 0.0001% cyclohexane and less than about 0.0001% ethanol]). In preferred embodiments, the defoaming agent is an emulsion of organo-modified polysiloxanes.

[00078] Furthermore, in some exemplary embodiments, the slurry or paste may also contain ethylene glycol in order to enhance the flow characteristics of the coating dispersion as well as the knitting characteristics of the nano-scale metal oxide particulate solids once applied to the target surface, for example, glass, such that a substantially uniform cured layer is achieved on the target surface. Without wishing to be bound by theory, the ethylene glycol dilutes the dispersion agent and, as compared to water has a very slow rate of evaporation. Thus the resulting slow rate of evaporation is believed to improve the flow of the coating dispersion and also allow for an increased curing time such that nano-scale metal oxide particulate solids have sufficient time to knit prior to drying and curing.

[00079] In some embodiments, the slurry, as described herein, is first prepared by mixing, on a weight/weight (w/w) basis, from about 15 % to about 25% nano- scale metal oxide particulate solids, about 2% to about 6% dispersion agent, about 0.4% to about 1.5% defoaming agent, about 0% to about 7% ethylene glycol and about 60.5% to about 82.6% water. In preferred embodiment, the slurry is prepared by mixing, on a w/w basis, from about 17.5 % to about 22.5% nano-scale metal oxide particulate solids, about 3.5% to about 4.5% dispersion agent, about 0.6% to about 1.0% defoaming agent, about 4.5% to about 6.5% ethylene glycol and about 65.5% to about 73.9% water. In a more preferred embodiment, from about 19.85% nano-scale metal oxide particulate solids, about 3.96% dispersion agent, about 0.8% defoaming agent, about 5.95% ethylene glycol and about 69.44% water are mixed to form the slurry. Indium tin oxide and/or antimony tin oxide particulate solids are the preferred nano-scale metal oxide particulate solids. For example, in a preferred embodiment, the slurry includes an admixture of about lOg nano-scale indium tin oxide or antimony tin oxide particulate solids , as described above, about 2.0g of dispersion agent, about 0.4g of defoaming agent, about 3.0 g of ethylene glycol and about 35.0g of water. Preferably, the indium tin oxide or antimony tin oxide particulate solids are provided with an average size distribution of from about 20 nm to about 50 nm with at least 90%, and more preferably 99%, of the particulate solids being provided within the abovementioned size distributions. Furthermore, the water may be provided as distilled water, double-distilled water, reverse osmosis water and/or reverse osmosis double distilled water, although tap water may also be used.

[00080] With regard to the coating dispersion, it may be desirable, in some exemplary embodiments, to also add one or more cross-linkers to the coating dispersion along with the slurry. Suitable cross-linkers are preferably water-borne non-isocyanate cross-linkers having from about 10% to about 25% propylene glycol content.

[00081] The resultant slurry, as described above is then added to an acceptable curable compound in the acceptable carrier. On a w/w basis, from about 10% to about 30% of the slurry and from about 70% to about 90% of the acceptable curable compound in the acceptable carrier is mixed to form the coating dispersion. In preferred embodiments, the acceptable curable compound in the acceptable carrier is a urethane and more preferably a water-based urethane. In some instances, one or more cross-linkers may also be incorporated in the coating dispersion. In such cases, from about 1% to about 4% cross-linkers may be added with a corresponding reduction in the amount of the acceptable curable compound in an acceptable carrier. In preferred embodiments, on a w/w basis, from about 15% to about 25% of the slurry, from about 2.5% to about 3.5% cross-linkers and from about 71.5% to about 82.5% of the acceptable curable compound in the acceptable carrier are mixed to form coating dispersion. In a most preferred embodiment, about 19.5% slurry, and about 80.5% urethane (having one or more cross-linkers contained therein in a suitable amount] on a w/w basis are mixed to form the coating dispersion. In another embodiment, about 19.5% intermediate solution, about 0.8% of a first cross-linker, about 2.3% of a second cross-linker and about 77.4% urethane on a w/w basis are mixed to form the coating dispersion. In terms of mass with regard to the last abovementioned embodiment, about 50.4 g of the slurry, about 2.0 g of the first cross-linker, about 6.0 g of the second cross-linker and about 200g of urethane are mixed to form the coating dispersion.

[00082] In embodiments where the nano-scale particulate metal oxide solids is first formed in a paste, as noted above, the paste is formed, on a w/w basis with quantities of the components as follows: about 50% to about 70% nano-scale particulate metal oxide solids (preferably indium tin oxide or antimony tin oxide), about 10% to about 25% ethylene glycol, and about 10% to about 25% of a dispersion agent. In a preferred embodiment, the paste is composed of about 58.8% nano-scale particulate metal oxide solids powder, about 20.6% of ethylene glycol and about 20.6% of a dispersion agent. The aforesaid components are then thoroughly mixed so as to form the paste having the nano-scale particulate metal oxide solids well dispersed therein. The paste is then mixed and dispersed in an acceptable curable compound with an acceptable carrier, as noted above. In some embodiments, about 5% to about 25%, on a w/w basis of the paste is added to about 60% to about 80% of the acceptable curable compound with the acceptable carrier along with from about 10% to about 15% of one or more cross-linkers and thoroughly mixed therein so as to well-disperse the particulate metal solids and form the coating dispersion. In preferred embodiments, about 74% the acceptable curable compound with the acceptable carrier, about 14% of one or more cross- linkers and about 12% of the paste are mixed to form the coating dispersion, thus resulting in a final coating dispersion having, on a w/w basis, about 74% of the acceptable curable compound with the acceptable carrier, about 14% of one or more cross-linkers, about 6% metal oxide particulate solids, about 1.5% of ethylene glycol and about 1.5% of a dispersion agent.

[00083] Also, the coating dispersions may have a longer shelf life and furthermore allow for the recycling of non-solidified coating dispersions in a flow coating or other application processes owing the particulate solid size ranges noted above since the particulate solids are well-dispersed and tend to stay in suspension in the coating dispersion longer.

[00084] The coating dispersion is applied on a substrate to form a cured layer. The cured layer is provided on the substrate with a substantially uniform thickness, substantially free from defects, of from about 5 μιη to about 20 μτη once cured.

[00085] Coated substrates having a cured layer with the nano-scale metal oxide particulate solids entrained therein of such a size distribution as described above exhibit minimal haze formation. In preferred embodiments, the nano-scale metal oxide particulate solids are indium tin oxide and/or antimony tin oxides and the coated substrate is glass. In one aspect, the minimal haze formation is achieved by the nano-scale metal oxide particulate solids having a size range distribution of about 5 nm to 100 nm, with about 90% of said particles within said range.

Furthermore, the nano-scale metal oxide particulate solids are substantially uniformly dispersed in the coating dispersion and thus the cured layer. In preferred embodiments, about 99% of the particles are within the aforesaid particle size distribution range. In still more preferred embodiments, the nano-scale metal oxide particulate solids size range distribution is from about 20 nm to about 50 nm. Therefore such a nano-size particle size range distribution and uniform distribution in the coating dispersion, and thus the cured layer on a substrate provides good visual clarity (as noted, for example, in the exemplary data provided below) to glass having the cured layer with enhanced infrared and near infrared light wavelength blocking properties. Furthermore, the coating dispersions form highly durable cured layers when applied to glass and other substrates.

[00086] When the cured layer is on a glass substrate, the transparency of the cured layer may be defined by visible light transference. Utilizing the coating dispersion to form the cured layer as herein described about at least 70% visible light transference is observed in some embodiments. Preferably about 85% visible light transference is observed. Therefore a glass substrate having infrared and near infrared-reflective and -absorptive properties, and thus solar heat-shielding properties is provided with good visual clarity and visual light transmittance. The coating dispersions, as described herein, when formed into a cured layer confer infrared and near infrared light wavelength blocking properties.

[00087] In some exemplary embodiments, urethane-containing coating dispersions, and thus cured layers also possess various additional durability and adhesion qualities as cured on glass substrates. For example, such coating dispersions, when cured to a glass substrate may meet ASTM 4541 adhesion requirements, meet the standards for the 2H Pencil hardness test, and pass a 50 Windex Rub Test. Such tests are known to persons in the art. Furthermore, the coating dispersions of the compositions disclosed herein may show a lifetime use of longevity of 10 or more years.

[00088] In some exemplary embodiments, a glass substrate having the visible light transmission properties as noted above, when coated with the ITO or ATO- containing coating dispersions as described herein may have a Solar Heat Gain Coefficient (SHGC) of from about 0.5 to about 0.8. The SHGC is a measure of the amount of heat transfer through a pane of glass. The measurement is dependent on the directly transmitted solar gain and the absorbed solar gain. In practical terms, the lower the SHGC, the lower the amount of heat that is transferred through the glass pane.

[00089] The cured layer, in some exemplary embodiments, has a thickness of from about 8 μπι to about 12 μπι. Furthermore, in keeping with the aim of a suitable level of clarity [and/or light transference], the coating dispersion is applied in a wet edge to wet edge technique so as to substantially avoid the formation of overlapping layers which may reduce the clarity of the cured layer.

[00090] In some embodiments, it may be desirable to have the coating dispersion form the cured layer on a glass substrate at a rate faster than by normal evaporation of the water component and polymerization curable compound.

Therefore, as an optional step infrared, near infrared and or UV light may also be directed to the coating dispersion once applied to the glass substrate in order to assist in the drying and curing process. In some instances the coating dispersion forms the cured layer and is dry to the touch after 1 hour, with the coating dispersion being dry through in 8 hours. Glass being coated with the coating dispersions described herein is stackable within 24 hours and the cured layer being fully cured within 21 days from the time of the coating dispersion being applied.

[00091] Utilizing the coating dispersions described herein to form the cured layer on a substrate, for example glass, a clear, durable, solar heat-shielding cured layer is provided. In preferred embodiments, the compositions are isocyanate-free and therefore may be applied indoors (or outdoors) with minimal disruption to daily operation in such spaces.

[00092] With respect to the examples presented below, characteristics of cured layers resulting form the coating dispersion as described hereinabove are provided.

[00093] Although the coating dispersion may be applied to a substrate in a variety of ways, in preferred embodiments it is applied by an electrostatic spray coating method. In general electrostatic coating processes involve using an apparatus which feeds the coating dispersion through a spraying or atomizing apparatus where the coating dispersion is given a negative charge as it exits the spraying apparatus. The surface that is to be coated is given a positive charge or ground relative the negatively charged coating dispersion, generally through grounding. The resultant charge differential causes the coating dispersion to be preferentially attracted to the desired surface.

[00094] With reference to Figure 17, an exemplary embodiment of an on-site electrostatic coating apparatus 100 is provided. An electrostatic spray gun 112 is provided which sprays an atomized coating dispersion 114 to be directed at a desired or target surface 133 on a substrate 134. As noted above, in preferred embodiments, the substrate is glass. The electrostatic spray gun 112, for example, may be purchased under the name Ransburg Vector AA90™ Air Assisted Airless Electrostatic Spray Gun from ITWRansburg, Illinois Tool Works. In the exemplary embodiment of Figure 17, an air compressor 116 is in communication with the electrostatic spray gun 112 via air hose 120a. In this case, the air compressor not only pressurizes the flow of coating dispersion 114 to the spray gun 112 but also provides one or more air outlets at the nozzle of the spray gun to further enhance the atomization and thus assist in reducing the particle size of the sprayed of the coating dispersion. The air compressor 116, in communication with the

electrostatic spray gun 112, assists to produce a finer mist or fog (atomization) 114a of the coating dispersion 114 , as shown in Figure 19, as opposed to an electrostatic spray gun without air assist and also serves to move the atomized droplets of the coating dispersion towards the target surface 133. A suitable air compressor, for example, may be a 3-gallon compressor supplied by Powerbuilt All trade Tools LLC. The coating dispersion 114 is maintained in tank 118 and fed through the coating hose 120b to the charging portion 122 of the electrostatic spray gun 112. The tank 118 may be, for example, provided as an AquaTank Waterborne Isolation Chamber™ from ITWRansburg, Illinois Tool Works. A ground is provided at 124 so as to connect to the target surface 133 and thus complete the electrostatic circuit such that the negatively charged coating particles 114 are attracted to the target surface 133. A control unit 126 provides the required negative charge that is fed though a low voltage cable 120c to the electrostatic spray gun 112 to negatively charge the coating dispersion atomized droplets 114. The low voltage cable may be, for example, a 10M low voltage cable. Electrical power for the apparatus 100 providing power to the control unit 126 and the air compressor 116 is supplied via plug 128 when connected to a standard 110V or 220V power supply (not shown). In order to improve the on-site capabilities of the abovementioned apparatus, the equipment may also be provided with a cart 130 having the air compressor 116, the tank 118 and the control unit 126 being coupled or mounted thereto.

[00095] As noted above, the coating dispersion is applied to produce a cured layer, with the aim of a suitable level of clarity (and/or light transference).

Transparency may be defined by light transference. Therefore, using an electrostatic spray apparatus, the coating dispersion may be applied using a wet edge to wet edge technique so as to substantially avoid the formation of overlapping layers which may reduce the clarity of the cured layer. As described below, successive local regions of the coating dispersion is thus applied with overlapping wet edges. The degree to which the edges overlap may be variable depending on a given

application. For example, in some cases, it may be desirable to have minimal overlap of the wet edges. This overlap allows the nano-scale metal oxide particulate solids to knit together to produce the substantially uniform thickness cured layer with the desired clarity characteristics. A 90% visible light transference may be obtained with a process as described herein and in preferred embodiments, 95% visible light transference is obtained.

[00096] In practice, the method comprises connecting the ground 124 to the surface desired, the target surface 133. In preferred embodiments, the water-based urethane ITO-containing coating dispersion 114 is placed in the tank 118, the power supply is connected via plug 128 to provide electrical power and the control unit 126 is turned on so as to provide power to the system and allow the coating dispersion 114 to be applied to the surface via the electrostatic coating spray gun 112. In some exemplary and preferred embodiments, the air compressor 116 is also employed to assist in directing the coating dispersion 114 at the target surface 133 as well as to assist in producing a finer mist or fog 114a of the coating dispersion droplets as it exits the electrostatic spray coating gun 112. In other words, the method may also include providing an air flow at the spray gun sufficient to promote a migration of the coating dispersion toward the target surface and/or reduce a particle size of the coating dispersion leaving the spray gun. Thus the air- assisted spray via air compressor 116 improves the atomization of the coating dispersion 114 and produces a turbulent flow sufficient to cause a cloud of droplets of the coating dispersion of a desired size range which are migratable to the substrate so as form a coating curable to the cured layer. The coating dispersion is then directed at the target surface 1 3.

[00097] Figure 18 outlines an exemplified on-site method of application the coating dispersion 114. The surface is prepared so as to thoroughly clean the target surface 133 on substrate 134. The target surface 133 is prepared by cleaning and in some cases scraped to remove debris from the surface which may result in an undesirable finish with reduced clarity once the transparent coating dispersion 114 cures. Care should be taken to avoid the use of ammonia and NH ³⁺ -containing cleaning products as this may affect the curing of the coating. However in cases where NH ³⁺ -containing cleaning products are desirable to be used during the cleaning process, the target surface should be further cleaning with an alcohol- based cleaning liquid. For example, the surface preparation includes manual cleaning of the surface substrate (window] through the use of, preferably, alcohol- based cleaning liquids wherein the alcohol component is provided from a stock of 95% or less alcohol or otherwise substantially free from organic solvents as a result of the distillation process, the removal of surface particles using, for example a razor blade scraper and optionally the deionization of the glass. The step of deionization is useful in some applications so as to reduce the likelihood of dust and other airborne contaminants being attracted to the glass substrate 134 between the surface preparation step and the time when the coating dispersion is applied. Although a concern, the attraction of air-borne contaminants to the glass after the coating dispersion is applied may not result in a significant reduction in the clarity of the final cured finish, however, care should taken to reduce air circulation during the process. Therefore, HVAC systems should be turned off during the execution of the method of the instant disclosure. The coating dispersion in the tank 118 is then charged with a negative charge using the high-voltage control unit 126 connected to the electrostatic spray gun 112 at 136.

[00098] The tank 118, from ITWRansburg Illinois Tool Works, AquaTank Waterborne Isolation Chamber™, may be used since the AquaTank Waterborne Isolation Chamber™ isolates the nonflammable coating dispersion 114 from the ground, thereby allowing the coating dispersion 114 to be electrostatically charged and deposited on the target surface 133. In this set-up, no isolation cage is required as is conventionally required, since the AquaTank Waterborne Isolation Chamber™ contains the voltage within the tank 118. Furthermore agitators within the tank keep the nanoscale metal oxide particulate solids in suspension and the coating dispersion can be added via a bung adaptor. The tank 118 also employs a filter/separator to prevent dirt and other contaminants from entering the coating dispersion and damaging the finish of the coated surface. Briefly, the tank 118 is filled with the coating dispersion 114 through a fine mesh screen to remove foreign matter that may clog fluid passage of the spray equipment. The tank is then sealed and the tank is grounded via a minimum of a 12-gauge ground wire connected to the pressure tank ground stud on the tank 118 and the other end of the ground wire 124 to a true earth ground. The coating dispersion hose 120b is then connected to the electrostatic spray gun 112. The air hose 120a is also connected to the electrostatic spray gun 112.

[00099] In an preferred embodiment, the air compressor 116 is charged to an operational air hose 120a pressure of from about 15 psig to about 20 psig above the tank 118 pressure. The coating dispersion 114 is then sprayed at the target surface 133 as shown at 138 in a manner so as to produce a substantially uniform cloud 114a or fog of the coating dispersion 114 as shown at 140 adjacent the glass 133 or other target surface 133 substrate. The coating dispersion 114, being released from the electrostatic spray gun 112 in a cloud 114a or fog pattern allows the negatively charged coating dispersion 114 to be attracted to and migrate substantially uniformly in a turbulent flow, as shown schematically in Figure 19, under the charge differential to the target surface 133, as shown at 142 in Figure 18 and 115 in Figure 19, for settling on the target surface in a substantially uniform thickness

substantially free from overlapping regions as shown at 150. In some cases, if more than one pass of the coating dispersion 114 is made and applied in a row-like or similar pattern directly to the target surface, as performed in prior processes, and not a substantially uniform cloud of coating dispersion droplets being provided adjacent the glass 133, then overlapping regions may occur which result in thicker and thinner regions of coating dispersion being applied to the glass 133. This results in an undesirable non-uniform coating with variations in final thickness over the coated area which may reduce clarity of the cured transparent coating on the window or other surface and cause undesirable distortion.

[000100] When forming the cloud of coating dispersion droplets 114a under turbulent flow near the target surface 133, a distance of at least 2.54 cm for each lOkV of power should be maintained between the atomizer or nozzle 132 and the target surface 133. In preferred embodiments, the cloud 114a is produced approximately 30 cm from the target surface 133, although other distances may be desirable in certain applications. Use of the method noted herein may result in greater than 90% of the coating dispersion droplets settling the target surface and curing thereto. Therefore, a minimal amount of the coating dispersion is wasted or diffused as overspray. In certain applications it may be desirable to mask regions where the coating is not intended to be deposited.

[000101] As noted above, infrared, near infrared and/or UV light may optionally be directed at the target surface to cause curing of the applied coating dispersion to the cured layer on the substrate at a rate faster than by normal evaporation of the water component and polymerization acceptable curable compound.

[000102] In order to achieve an applied and desired final average coating thickness of about 8 μπι to about 20 μπι and preferably of substantially from about 10 μπι to aboutl2 μιη certain other considerations should be taken into account. The coating dispersion is provided to the tank 118 with a viscosity of from about 18 seconds to about 25 seconds on a #2 Zahn cup measurement so as to allow the coating dispersion to flow as desired and produce the cured layer of the

abovementioned desired thickness.

[000103] Generally installed glass has a given moisture content owing to the condensive properties of humidity from the surrounding air settling on the glass as a result of temperature differentials from one side of the glass to the other. The moisture content provides the ground across the otherwise substantially non- conductive glass substrate. Of course, the glass substrate may in some cases be provided with an additive during formation to provide a conductive path to establish a substantially uniform ground. Additionally with respect to the glass, the coating dispersion should be applied to the glass at a glass and ambient temperature of from about 5°C to about 40°C. If the temperature of the glass is greater than about 40°C, the coating dispersion tends to begin to dry and cure such that the nano-scale particulate metal oxide solids are not provided with sufficient time to knit and distribute to a substantially uniform thickness prior to the curing of the acceptable curable compound. When glass and ambient temperatures are below 5°C, the glass may be too cold to produce the desired one-coat finish. Additionally, condensate may form on the glass, thus tarnishing or otherwise adversely affecting the cured layer finish when applied at lower temperatures and the coating dispersion has an undesirable lengthened curing time which may also adversely affect the final finish. Furthermore, when the coating dispersion is applied at temperatures of less than 5°C, the coating dispersion, once applied on the glass tends to sag and run such the desired clarity of the cured layer is not obtained.

[000104] In some embodiments, a colour component may also be added to the coating dispersion so as to provide a tinting to the coating dispersion. For example in regions of high sunlight, a dark tint, such as a transparent grey or black colouring may be desired. In regions of predominating cloud cover, an amber or rose tint may be desirable.

[000105] Thus, exemplified embodiments provide a process for applying a coating dispersion having therein nano-scale metal oxide particulate solids on-site to building structures, including interior and exterior glass windows and other on- site surfaces such as window frames, walls, ceilings, roofs, HVAC systems, furniture, fixtures, and infrastructure such as electrical transformers, pipelines and solar panels. Exemplified processes thus enable in some cases, a high-quality finish akin to a factory baked finish on surfaces, but that have in fact have been coated "on-site", rather than coating surfaces in factories and then shipping coated structural components to building locations for installation. The electrostatic processes herein may thus provide greater than 90% transfer efficiency of coating dispersions to targeted surfaces such as windows and frames, resulting in minimized over-spray to unwanted surfaces and product waste. The processes also enables interior coating of surface structures, such as skylights, that could not otherwise be coated and have cured thereto a water-based coating dispersion having nano-particulated metal oxide solids to form a cured layer.

[000106] The preferred embodiments may make it possible to ameliorate various application problems and to obtain on-site coated surfaces using water-based coating dispersions with nano-scale metal oxide particulate solids with a very high- quality coated finish.

EXAMPLES

[000107] Nanoparticles of indium-tin precipitate produced by the continuous precipitation process as disclosed above are discussed below with respect to the following examples wherein the indium tin oxide nanoparticles have a substantially consistent indium-to-tin ratio composition with optical and electronic properties for use in, for example, coatings and other applications.

Example 1

[000108] A seeding solution was prepared at 50°C by dissolving 118.8 g indium (III) chloride, 14.19g of tin (IV) chloride, 3.6 g of caprolactam as a solubility modifying agent, in 900 raL of water and 7.5 mL ammonia (the first base). The seeding solution was determined to have a pH after mixing of <1 pH units. The seeding solution was placed in the first feed tank 10 and kept at a substantially constant room temperature and a pH of 0.5. The seeding solution had a tin to indium ratio of 10.6% or about a ratio of 10:90. The second base solution was provided as 129 mL of concentrated ammonium hydroxide with a pH of 12 and was placed in the second feed tank 14. The temperature of the second base solution was kept at a substantially constant room temperature, along with a substantially constant pH of 12. The seeding solution and the second base solution were fed concomitantly into stirred reaction vessel 12, one with the other, having therein 300 mL of concentrated ammonium hydroxide with a pH 12 and kept at substantially constant room temperature and substantially constant pH of 12. The continuous reaction was performed at room temperature with the seeding solution and the second base solution added to the reaction vessel 12, each at a rate of 10 mL/min at the outset of the continuous process. The rate of addition for the second base solution was adjusted so as to maintain the pH of the mixture substantially constant at 12 pH units. The mixture in the reaction vessel 12 was mixed at a rate of 700 rpm. During the reaction, samples were taken for compositional analysis. The results showed precipitated precursor nanoparticles having a consistent uniform tin to indium ratio of about 10.6% (a ratio of about 10:90] throughout reaction at the various time points. After 200 ml of mixture, having therein indium tin nano-scale precipitated precursor solids, was collected in the collecting tank 16, the reaction was terminated. The content of collecting tank was mixed for 1 hr. Subsequently the solids portion in the collection tank 16 was separated by centrifugation and washed several times with Millipore™ water until no chloride was detected in the wash water. The nanoparticles were then dried. The resultant particles had average particle size of about 20 nm in diameter. The dried resultant precipitated precursor indium tin oxide nanoparticles were further heat-treated at 700°C for 30 minutes until a yellow powder of indium tin oxide was obtained and then further treated at 350°C for 3 hours under an H ₂ /Ar gas blanket (10%v/v). A blue coloured powder of substantially spherically-shaped ITO nanoparticles was obtained having a substantially constant uniformity of tin to indium ratio of 10.6% corresponding to a indium weight percent of 90.38 and a tin weight percent of 9.62 and average particle size of 19.6 nm with a particle size distribution in range of 10 nm to 40 nm. A SEM image of the nanopowder is shown in Figure 4. X-Ray diffraction analysis (Figure 2) of the blue powder showed the product of this reaction is an indium doped tin oxide.

[000109] 12 g of the blue coloured nanopowder of ITO was mixed with 4.2 g of ethylene glycol and 4.2 g of copoly(acrylic acid/maleic anhydride) as surfactants and sonicated for 45 minutes. The powder easily dispersed creating a high viscosity dark blue liquid, thus forming an indium tin oxide paste.

[000110] A measured amount of the paste was dispersed in a waterborne polyurethane resin dispersion (50%w/w) and mixed for 20 minutes using a homogenizer to create a 6% w/w coating dispersion. The liquid was cast onto 3 mm clear glass slides using a #12 bar. The dry film thickness was about 6 microns. The UV-Vis-NIR light transmission characteristics of the coating dispersion, when cured to a glass substrate, indicates an optically clear coating with no visible defects and infrared (IR) shielding properties with shielding of over 90% of near infrared (NIR) at wavelengths higher than 1700 nm as is shown in Figure 5.

Example 2

[000111] A seeding solution was prepared at 50°C by dissolving 118.8 g Indium [III) chloride, 14.19g of tin (IV) chloride, 3.6 g of caprolactam as a solubility modifying agent, in 900 mL of water and 12.6 mL ammonia (the first base). The seeding solution was determined to have a pH after mixing of <1 pH units. The seeding solution was placed in the first feed tank 10 at a substantially constant room temperature and a pH of 0.5. The tin to indium ratio in the seeding solution was 10.6% (10:90). The second base solution was provided as 267 mL ammonium hydroxide diluted with 450mL of water, and placed in the second feed tank 14. The temperature of the second base solution was kept at a substantially constant room temperature and at a substantially constant pH of 10. The first and second flow controllers 20 and 22 were opened for the simultaneous addition of the seeding solution and the second base solution into the reaction vessel 12 containing 900 mL of water at 50°C and continuous mixing. The reaction taking place in the reaction vessel 12 was kept at 50°C and at a substantially constant pH of 3.5. The rate of addition for the second base solution was adjusted, as required and maintained such that in the reaction vessel 12, the pH was maintained substantially constant at 3.5 pH units. The mixture was mixed at the rate of 650 rpm in the reaction vessel.

During the reaction samples were taken for compositional analysis. The results showed production of precipitated precursor metal oxide nanoparticles having a constant uniformity of tin to indium in a ratio of about 10.6% (10:90) throughout reaction. After 200 ml of the mixture, having therein precipitated precursor indium tin nanoparticles was produced and collected in the collecting tank, the reaction was terminated. Closing the inlets 20 and 22 stopped the reaction. Subsequently, the pH of the contents of the collecting tank was adjusted to a pH of 10 by adding the required amount of concentrated ammonium hydroxide and mixed for additional 1 hour at room temperature. The precipitated precursor indium tin nanoparticles were separated by centrifugation and washed several times with Millipore™ water until no chloride was detected in the wash water. The nanoparticles were then dried. The nanoparticles obtained were shown to have a plate-like shape by SEM imaging with an X-Ray diffraction pattern showing a crystalline mixture of indium and tin nanoparticles. SEM imaging of the produced nanoparticles indicated that ITO nanoparticles with plate dimensions of about 60 nm X 200 nm where produced, as shown in Figure 3. The dried powders were further heat treated in air at 700°C for 30 minutes until a yellow powder of indium tin oxide was obtained and then further treated at 350°C for 3 hours under an H ₂ /Ar gas blanket (10.%v/v). An indium tin oxide nanopowder having plate-like shaped nanoparticles of the indium tin oxide was obtained having a substantially constant uniformity of indium to tin in a ratio of 10.5% (a ratio of about 10:90) corresponding to an indium weight percent of 90.4 and a tin weight percent of 9.6.

Examples 3a and 3b

[000112] Example 3a is a repetition of Example 1 however a different solubility- modifying agent was used. The 3.6 g of caprolactam in the seeding solution of Example 1 was replaced with 2.12 g of decylamine. The remainder of materials and process conditions were identical to those disclosed in Example 1. The obtained precipitate precursor metal oxide nanoparticles, indium tin nanoparticles, were processed following the procedure described in Example 1. A spherically-shaped, light blue colour, nanoparticle powder was obtained having a substantially constant indium-to-tin ratio of 10.6% corresponding to a indium weight percent of 90.38 and a tin weight percent of 9.62 with an average crystal size of about 30 nm. X-Ray diffraction data for this sample was the same as Example 1, which is consistent with a cubic phase indium tin oxide.

[000113] Example 3b is a repetition of Example 3a however a different solubility-modifying agent was used. The 2.12 g decylamine in the seeding solution of Example 3a was replaced with 3.2 g of dodecylamine. The remainder of materials and process conditions were identical to those disclosed in Example 3a. The obtained precipitate precursor metal oxide nanoparticles, indium tin nanoparticles, were processed following procedure described in Example 1. A spherically-shaped, light blue colour, nanoparticle powder was obtained having a substantially constant indium-to-tin ratio of 10.6% corresponding to a indium weight percent of 90.4 and a tin weight percent of 9.6 with an average crystal size of about 30 nm. X-Ray diffraction data for this sample was the same as Example 1, which is consistent with a cubic phase indium tin oxide.

Examples 4 and 5

[000114] The process described in Example 1 was repeated, however the solubility-modifying agent of caprolactam was replaced with tartaric acid or citric acid. The amount of tartaric acid or citric acid was 1:1 mole based on the tin content in seeding solution. The obtained precipitate of indium-tin nanoparticles was processed following the procedure described in Example 1. A spherically-shaped, light blue coloured nanoparticle powder was obtained having a substantially constant indium-to-tin ratio of 10.6% corresponding to an indium weight percent of 90.38 and a tin weight percent of 9.62 with an average crystal size of about 23 nm for tartaric acid and about 26 nm for citric acid. The X-Ray diffraction data from both samples was shown to be the same as that in Example 1, which is consistent with a cubic phase indium tin oxide.

Example 6

[000115] Example 6 is a repetition of Example 1, however the seeding solution was aged for 24 hours. A spherically-shaped blue coloured powder of ITO nanoparticles was obtained having a substantially constant tin to indium ratio of 10.6% corresponding to an indium weight percent of 90.35 and a tin weight percent of 9.65; with an average particle size of 16 nm and a particle size distribution in the range of 8 nm to 35 nm.

Example 7 [000116] A seeding solution was prepared at 50°C by dissolving 118.8 g indium (III) chloride, 14.19g of tin (IV) chloride, 3.6 g of caprolactam as a solubility modifying agent in 900 mL of Millipore™ and 7.5 mL ammonia (the first base). The seeding solution in this example was determined to have a pH, after mixing, of <1 pH units. The seeding solution was placed in feed tank 10 and kept at room

temperature. The second base solution was comprised of 228 mL concentrated ammonium hydroxide and was placed in feed tank 14 and kept at room

temperature. The seeding solution and the second base solution were fed concurrently, one with the other, into stirred tank reaction vessel 12, so as to effect precipitation of the precursor metal oxide nanoparticles, having therein a solution of 900 mL of water and 120 mL concentrated ammonium hydroxide at a pH of 10 and temperature of 50°C. The continuous reaction was kept at 50°C while the seeding solution and the second base solution were added at rate of 10 ml/min. The rate of addition for the second base solution was adjusted to maintain the pH of the mixture substantially constant at pH of 10 units. During the reaction samples were taken for composition analysis. The results showed production of nanoparticles having a consistent tin to indium ratio of about 10.5% (10:90) throughout reaction. After 200 ml of mixture, having therein indium-tin hydroxyl hydrate nanoparticles, was collected in the collecting tank 16, the reaction was stopped. The content of collecting tank 16 was further mixed for 1 hr. Subsequently the solids in the collection tank 16 were separated by centrifugation and washed several times with Millipore™ water until no chloride was detected in the wash water. The

nanoparticles were then dried. The indium tin oxide precursor precipitated nanoparticles obtained were shown to have a spherical shape with an X-Ray diffraction pattern showing a mostly amorphous mixture of indium and tin hydroxide. SEM imaging showed particles having an average particle size of 40 nm in diameter. The dried powders were further processed or calcinated at 700°C for 30 minutes until a yellow powder of indium tin oxide was obtained and then further treated at 350°C for 3 hours under an H ₂ /Ar gas blanket (10%v/v). A blue coloured powder of substantially spherically-shaped ITO nanoparticles was obtained having a substantially constant uniformity of indium-to-tin ratio of 10.5% with an average particle size of 40 nm and a particle size distribution in the range of 20 nm to 70 nm.

Example 8 (comparative example)

[000117] In this comparative example between the instantly disclosed

continuous method for producing indium tin oxide nanopowders and a conventional method, the resulting indium tin oxide nanopowder of Example 1 was compared to an ITO produced by a conventional process is shown. The following method for a conventional process was used, in which 140g of indium [III) chloride, 18g tin (IV) chloride penta hydrate and 5.6 g of caprolactam were introduced into 1400mL of water and stirred. After a clear solution was formed, it was heated to 50°C. After this temperature had been reached, 105mL of ammonium hydroxide solution (25% strength) was added drop-wise with vigorous stirring. The suspension was stirred at a temperature of 50°C for a further 24 hours. For complete precipitation, a further 280 mL of ammonium hydroxide was subsequently added to the mixture. Samples of the formed nanoparticles were tested for indium-to-tin composition during the reaction time. The composition of nanoparticles formed during reaction is compared, below, with those obtained by the continuous process of the instant disclosure as described in Example 1. The comparison is shown in Table 1 and can also be seen in accompanying Figures 6a and 6b. As shown in Table 1, the

composition or ratio of indium to tin in the formed nanoparticles of the

conventional process changes according to the various time points in the

progression of the reaction. In sharp contrast, in the case of the instant continuous method, the ratio (or composition) of indium to tin in the formed nanoparticles remains substantially consistent throughout the reaction time. This provides a final indium tin oxide nanopowder having a more consistent and constant uniformity of the ratio of indium to tin, based on the initial concentrations thereof in the seeding solution, the predetermined desired ratio.

[000118] It is also worth noting that when conventionally calculating the ratio of indium to tin for nanoparticles emerging from the conventional process, it is necessary to determine the average ratio across the entire reaction time in conventional processes, that being from samples taken at the beginning, middle and end of the reaction period and as shown in Table 1, for example. In conventional processes this ratio changes depending how long the reaction has been proceeding, thus in a given batch of precipitated precursor indium tin oxide nanoparticles, there may be a significant portion of particles which do not have the desired indium-to-tin ratio. Even so, in the calculations, on the average ratio of indium to tin, these initially formed nanoparticles are "averaged out" of the total, while the particles still remain in the sample. Furthermore, in some instances, the precipitated precursor indium tin oxide nanoparticles formed early in the conventional process may not bestow the desired electrical and optical properties for a given application which may otherwise be present in the nanoparticles formed later in the conventional process.

[000119] In the continuous method where the seeding solution and the second base solution are simultaneously and continuous mixed and introduced to the reaction vessel one with the other to effect precipitation as disclosed herein, and as per the results shown in Table 1, the ratio of indium to tin in the formed

nanoparticles remains substantially consistent according to the predetermined ratio of indium to tin in the seeding solution as compared to conventional processes across the reaction period.

Table 1: Composition (ratio) of tin to indium in nanoparticles at different times of precipitation for the herein disclosed continuous process and a conventional process

2 90.0 10.0 0.106 - - -

6 91 9.0 0.096 - - -

10 91.0 9.0 0.099 - - -

30 90.0 10.0 0.106 99.52 0.483 0.005

70 90.0 10.0 0.106 99.02 0.978 0.010

300 ( 99.38 0.619 0.006

Reaction completed

1440 91.75 8.254 0.090

[000120] Samples taken as a function of reaction time show resulting

nanoparticles using the continuous process of the instant disclosure are

substantially homogenous (left hand section of Table 1 and Figure 6a) in

composition (for example, an average Sn/In ratio 0.106) throughout the reaction time with ratios staying within a measurement error of +/-10% from one sampling to the next, or along a theoretical line or threshold shown at A of Figure 6a, corresponding to the raw material input composition in the seeding solution. Thus, in an exemplary embodiment as shown in Figure 6a it is graphically shown that the resulting indium tin oxide nanoparticles from the continuous process of the instant disclosure have a substantially consistent ratio of indium to tin during the reaction time as evaluated using percentage tin doping levels that may be within a measurement error of +/-10%.

[000121] Whereas, in the case of the conventional process, shown at solid line B in Figure 6b, for comparison, and also in Table 1, the ratio of indium to tin changed significantly over the various time points resulting in a mixture of particles having various ratios of tin to indium, in the range of 0.001 to 0.09 which, as can be noted is a variation of almost 90% from the smallest ratio to the largest ratio. Furthermore, the resultant particles have various ratios of indium-to-tin that are different from the indium-to-tin ratio in the starting materials of about 12.9%, ranging from the 1.0% to 9.0%, as noted above. With respect to Figure 6b, the hash-dotted line C indicates the time period corresponding the reaction time of line A in Figure 6a and hashed line AA represents a theoretical extrapolation of line A from Figure 6a corresponding to further time points should the continuous reaction of Figure 6a be run longer. The extrapolated line AA is a theoretical determination based on the data obtained for line A of Figure 6a.

[000122] Turning again to the comparative example, the white precipitate of precursor indium tin oxide formed by the conventional process was centrifuged and washed. The precursor indium tin oxide using the conventional process was processed in the same way as described above. In order to comparatively illustrate the performance of the indium tin oxide as produced in accordance with the instant disclosure to that as produced with a conventional process the following is provided. The indium tin oxide, having a more consistent indium-to-tin ratio composition, was formed into a coating dispersion using the heat-treat blue- coloured ITO. The indium tin oxide was then added to a urethane coating dispersion to form the coating dispersion and the coated onto a clear 3mm glass slide using a # 12 bar and left to air dry before characterization. A coating was similarly prepared using resultant indium tin oxide nanoparticles from the conventional method. The indium tin oxide content of the two liquid coatings was 6% w/w. The cured indium tin oxide coating dispersions were determined to have a film thickness of 6 microns, in both cases. The cured coating dispersion, having the indium tin oxide made according to the conventional batch process entrained therein, showed less UV-Vis- NIR spectrum-shielding properties as compared the coating having the indium tin oxide entrained therein made according to the instant continuous method. The cured dispersion on the glass with indium tin oxide particles made according to the conventional process of the instant example thus showed inferior IR and NIR shielding characteristics compared to the cured coating dispersion having the indium tin oxide nanoparticles of continuous process of the instant disclosure. Table 2: IR shielding properties of coated films of ITO made from an exemplary continuous process and compared with a conventional process. Dispersion and coating conditions for both ITO are the same.

[000123] Table 2, with particular reference to the last two rows, shows that the continuous process of the instant disclosure for producing indium tin oxide nanoparticles having a substantially homogeneous composition, provides improved optical performance, particularly with regard to IR and NIR light wavelength blocking properties. Without wishing to be bound by theory, evidence indicates that indium tin oxide nanoparticles having a substantially constant uniformity of the ratio of indium to tin among the nanoparticles, which when entrained in coating dispersion, blocks infrared and near infrared light at lower wavelengths as compared to particles produced by known batch conventional processes in the same given coating.

Coating Dispersions and Coated Substrates

[000124] With respect to the examples presented below, characteristics of a coated glass substrate resulting from coating dispersions herein described cured to the substrate are provided.

Example 9

[000125] Six glass substrate samples (samples A to F) were tested whferein the final concentration of indium tin oxide in the coating dispersion and cured to the glass was as follows:

Sample A: 4% (w/w) nano-particulated indium tin oxide;

Sample B: 3% (w/w) nano-particulated indium tin oxide;

Sample C: 6% (w/w) nano-particulated indium tin oxide;

Sample D: 4% (w/w) nano-particulated indium tin oxide;

Sample E: 0% (w/w) nano-particulated indium tin oxide (clear polyurethane coating only); and

Sample F: clear glass with no coating applied.

[000126] With respect to the recorded characteristics conferred to the glass, Table 3 is presented so as to show, in exemplary embodiments, the following: Solar Transmission (ST), Solar Absorption (SA), Visible Light Transmission (VLT), Solar Heat Gain Coefficient (SHGC), Solar Reflectance (SR).

Table 3: Coated substrate light transmission and Solar Heat Gain Characteristics

Sample ID ST% SA% VLT% SHGC SR%

A 64 29 85.6 0.68 6.5

B 72.2 20.7 88.2 0.7 6.6 c 58.9 34.6 83.6 0.65 6.4

D 65.1 28.5 86.6 0.69 6.5

E 82.8 9.7 89.9 0.71 7.0

F 82.9 9.7 89.9 0.75 7.8

Example 10

[000127] Example 10 outlines testing procedures and results for glass slides coated with exemplary embodiments of the coating dispersion as disclosed herein.

Procedure, Methodology and Equipment

[000128] Solar and Photometric measurements were made using a Varian Cary 5000 UV (ultraviolet) /VIS (visible)/NIR (near infrared) Spectrophotometer. The UV/VIS/NIR Spectrophotometer is a double beam, direct ratio recording, rapid scanning high performance spectrophotometer with exceptional scan rate, resolution, and repeatability characteristics. This device has an extended spectral range allowing it to scan between 0.17 and 3.30 micrometers. For the analysis presented herein, an integrating sphere attachment was used. The attachment allows for the measurement of the total, diffuse-only, and specular-only directional- hemispherical reflection between 250 and 2500 nm at a resolution of 0.05 nm. All measurements are spectral (as a function of wavelength).

[000129] The equipment was up-to-date in service and was calibrated before each use. Complete details and specifications on the equipment can be found at www.varianinc.com.

Samples

[000130] Both sides of eight glass samples were examined. No information was provided to the testers about the samples except that they were coated on one side, and that Sample 8 was uncoated. Therefore the testers where blinded to the compositions applied to the glass substrate samples. The results of the spectral testing are presented below as Tables 4 to 6 and also in Figures 7 to 14.

Procedure

[000131] Solar and Photometric tests and data analysis were performed in accordance with ASTM Standard E903 Test Method for Solar Absorptance,

Reflectance, and Transmittance of Materials Using Integrating Spheres. The reader is referred to that standard for complete details on the theory and methods used to perform the analysis.

• «

[000132] Zero/Baseline correction was performed using a calibration standard

(Labsphere SRS-99-010; Serial No: ODllC-5349; NIST Traceable to SRS-99-020-WS-

3, Nov 14, 2008) as per Section 8.2.1 of ASTM E903. Zero/Baseline measurements were performed on start-up and after 4 hours of operation. The correction was applied by the Cary 5000 Operating Software.

[000133] Calculation of the solar reflectivity was done using a 50-point selected ordinate method as specified in Sections 8.3.1 and 8.3.4 of ASTM E903. By that method, the solar irradiance distribution for a 1.5 air mass spectrum is divided into 50 sections containing l/50th of the total energy in the spectrum. The solar reflectivity/transmissivity is the average of spectral reflectivity/transmissivity taken at the centroids of those 50 sections.

[000134] ASTM E891 (It is noted that ASTM E891 has been replaced by ASTM G159. The change is editorial in nature only, and the information contained in the original standard has not been changed.) Standard tables for Terrestrial Direct Normal Solar Irradiance for Air Mass 1.5 were used to determine the wavelengths.

[000135] For opaque samples, the solar absorptance is calculated by subtracting the solar reflectance from 100%.

[000136] The SOC 400T reflectometer measures reflectance for room

temperature thermal radiation. The reflectivity of a sample is calculated by comparing it to a polished gold film with a constant (spectral reflectivity) of 98%. [000137] For opaque samples, the NIR absorptance (equal to emittance) is calculated by subtracting the infrared reflectance from 100%. A correction for the difference between hemispheric-normal and hemispheric-hemispheric reflectance has been made to the spectrally averages results.

[000138] Measurements of total reflectivity and transmissivity were performed in the UV/VIS/NIR ranges. Total reflectivity was also measured in the NIR.

[000139] Window Performance was evaluated using the WINDOW6.3 (LBNL) _• software. The measured optical properties, of each samples were used to create new glazings in the WINDOW6.3 glazing data base. These glazings were then used in representative windows and simulated using NFRC 100 (NFRC) conditions.

• The construct was a single glazing. The glazing was oriented such that the coating faced the indoor side.

[000140] Only Centre-Glass values are reported.

Precision

[000141] The precision of the Spectrophotometer measurements taken are good to approximately +/- 0.1%. It is noted, however, that this error changes depending on the sensor and light source being used. Shortwave measurements for example, were taken using a Silicon sensor below 800 nm

[000142] ASTM E903 notes that there are errors associated with the

measurements, computation method, and spectral irradiation distribution. As these errors are difficult to quantify, the standard suggests that +/- 2% error be assigned to the solar transmission and reflection. To account for differences in the solar spectrum, an error of +/- 3% is suggested. A complete discussion of those errors is given in ASTM E903.

[000143] The SOC 400T measurements are accurate to +/-!%. [000144] It is noted that there is a discontinuity in the results at 2500 microns. This is due to a number of factors. At this point, measurement methods and calibration standards have changed. More importantly, it is assumed that the transmission of the sample is zero at wavelengths greater than 2500 microns because it was notable to be measured. In reality, it is likely 2 to 3% of full scale at 2500 microns, and goes to zero as wavelength increases.

Results

[000145] The test results are summarized in the following Tables 4 to 6. Spectral plots of the data are provided as Figures 7 to 14.

Table 4: Spectrally Averaged Solar Properties

Table 5: Spectrally Averaged Visible Properties

Table 6: Centre-Glass Window Performance Window Sample SHGC ^{a d}

Single Glazing ^b Sample 1 0.73 r-15.1%]

Sample 2 0.71 f-17.4%]

Sample 3 0.78 f-9.3%

Sample 4 0.62 f-27.9%]

Sample 5 0.70 f-18.6%1

Sample 6 0.74 f-14.0%]

Sample 7 0.86 fO.0%1

Sample 8 ^C 0.86

a All models run using WINDOW6.3 at NFRC 100 weather conditions.

b Modeled as 6, glazing with coating dispersion facing indoor side.

c Sample 8 has no coating. This window is the baseline performance.

d Bracketed terms are percent difference from baseline window.

Comments

In the shortwave:

• The coating has no significant impact on the visible properties of the glass, unless thickly applied (as per sample 4).

• In the NIR the coating dispersion makes the glass highly absorbing. This

would reduce the Solar Heat Gain Coefficient (SHGC] of the window. The degree to which this occurs would also depend on the details of the window construction.

• These two results combined show that the coating dispersion cured to glass has application as a highly transparent solar control coating.

Example 11

[000146] With reference to Figures 15 and 16, an X-ray Diffraction plot and SEM photographs of the coating dispersions, respectively, applied to glass are shown with respect to exemplary batches 5 to 9 of the coating dispersions disclosed herein. The indium tin oxide nanoparticles shown have an average size distribution of from about 10 nm to about 100 nm. In some embodiments, 90% of the particles are within the size range, and preferably 99% of the indium tin oxide particles are within the abovementioned size distribution range. In the preferred embodiments, the particles have a size range of 20 nm to 50 nm.

[000147] The breakdown of percent composition of the indium and tin oxides as well as ratios thereof in the batches 5 to 9 are noted in Table 7 below.

Table 7: Ratio of Indium to Tin oxide in Batches 5 to 9 in produced in accordance with the process for preparing precipitated precursor metal oxide nanoparticles and subsequent constant uniformity of metal oxide ratio of nano-scale metal oxide particulate solids.

[000148] Figures 15 and 16 and Table 7 show that the nano-particulated indium tin oxide produced in accordance with the process and coating dispersions of the disclosure are well-dispersed in the coating dispersions. Furthermore, the coating dispersion cured to glass to form the cured layer has good clarity and minimal hazing owing to at least 90% of the particles being within the abovementioned size ranges and having constant uniformity in the ratios of metal oxides. Therefore the cured layer formed on a glass substrate provides good clarity and visual

characteristics to glass once cured thereto.

[000149] Furthermore coating dispersions, having the particles as noted above, show an increased shelf-life owing to the relatively uniform size distribution of the nano-particles as suspended in the urethane coating dispersions. This also enables the ability to recycle the coating dispersion collected as "run-off from techniques such as flow coating since the particles tend to remain in suspension as compared to other indium tin oxide suspensions.

[000150] Those of skill in the art will recognize certain modifications,

permutations, additions and sub-combinations of the materials, components, process and steps noted herein. While a process for preparing nano-scale precipitated precursor metal oxide solids, metal oxide solids, curable coating dispersions containing nano-scale metal oxide particulate solids, substrates having a cured layer containing nano-scale metal oxide particulate solids and methods of application said coating dispersions have been described for what are presently considered preferred and exemplary embodiments, the invention is not so limited. To the contrary, the invention is intended to cover various modifications and equivalent materials included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent materials and functions .thereof.