TEMPERATURE TREATMENT OF DIAMONDS

FIELD OF DISCLOSURE

[0001] The present disclosure relates to the field of diamonds industry. More particularly, the present disclosure relates to a device for improving color of a diamond.

BACKGROUND OF THE DISCLOSURE

[0002] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0004] Diamonds are well known. A diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic, other well-known solid form of carbon at room temperature and pressure being graphite. A diamond has the highest hardness and thermal conductivity of any natural material, properties that are utilized in major industrial applications such as cutting and polishing tools.

[0005] Another major application of diamond is in jewelry and diamonds for such purposes are highly priced, sometimes at millions of dollars. Superior quality gemstone with rarest natural color like blue, yellow, green, red and pink command very high prices. Even a colorless diamond is considered rare and hence commands similar price.

[0006] Diamonds are conventionally divided into four main categories which are designated as Type la, Type lb, Type Ila, and Type lib. In reality, there is a smooth change in impurity concentration/arrangement between the four types and so, intermediate varieties also exist.

[0007] Type I diamonds, the most common class, contain nitrogen atoms as their main impurity, commonly at a concentration of 0.1%. Type I diamonds absorb in both the infrared and ultraviolet region, from 320 nm. They also have a characteristic fluorescence and visible absorption spectrum.

[0008] Type la diamonds make up about 98% of all natural diamonds. The nitrogen impurities, up to 0.3% (3000 ppm), are clustered within the carbon lattice, and are relatively widespread. The absorption spectrum of the nitrogen clusters can cause the diamond to absorb blue light, making it appear pale yellow or almost colorless. Most la diamonds are a mixture of IaA and IaB material; these diamonds belong to the Cape series, named after the diamond-rich region formerly known as Cape Province in South Africa, whose deposits are largely Type la. Type lb make up about 0.1% of all natural diamonds. They contain up to 0.05% (500 ppm) of nitrogen, but the impurities are more diffuse and the atoms are dispersed throughout the crystal in isolated sites. Type lb diamonds absorb green light in addition to blue, and have a more intense or darker yellow or brown color than Type la diamonds. The stones have an intense yellow or occasionally brown tint; the rare canary diamonds belong to this type, which represents only 0.1% of known natural diamonds. The visible absorption spectrum is gradual, without sharp absorption bands.

[0009] Type II diamonds have no measurable nitrogen impurities. Type II diamonds absorb in a different region of the infrared, and transmit in the ultraviolet below 225 nm, unlike Type I diamonds. They also have differing fluorescence characteristics, but no discernible visible absorption spectrum. The crystals as found tend to be large and irregular in shape. Type II diamonds were formed under extremely high pressure for longer time periods.

[00010] Type Ila diamonds make up 1-2% of all natural diamonds (1.8% of gem diamonds). These diamonds are almost or entirely devoid of impurities, and consequently are usually colorless and have the highest thermal conductivity. They are very transparent in ultraviolet, down to 230 nm. Occasionally, while Type Ila diamonds are being extruded towards the surface of the Earth, the pressure and tension can cause structural anomalies arising through plastic deformation during the growth of the tetrahedral crystal structure, leading to imperfections. These imperfections can confer a yellow, brown, orange, pink, red, or purple color to the gem. Type Ila diamonds can have their structural deformations "repaired" via a high- pressure high-temperature (HPHT) process as further elaborated, removing much or all of the diamond's color. [00011] Type lib diamonds make up about 0.1% of all natural diamonds, making them one of the rarest natural diamonds and very valuable. In addition to having very low levels of nitrogen impurities comparable to Type Ila diamonds, Type lib diamonds contain significant boron impurities. The absorption spectrum of boron causes these gems to absorb red, orange, and yellow light, lending Type lib diamonds a light blue or grey color, though examples with low levels of boron impurities can also be colorless.

[00012] As described, Type I diamonds contain nitrogen as the major impurity whereas type Ila diamonds contain undetectable nitrogen or boron as major impurity. In type la category nitrogen atoms are held either in pairs called A centers, or as a cluster of fours called B center. A single atom of Nitrogen may as well exist and is identified as a C defect and the diamond designated as lb. Some diamonds also contain clusters of three nitrogen atoms called N3 Centers. More than 97% of diamonds in the world can be classified as Type la diamonds. Diamonds with C defect (Type lb) constitute about 0.8% of natural diamonds. Type la diamonds also contain planar defects known as platelets, which are small flat inclusions a few atoms thick and about 400 atoms across, that may contain some nitrogen in an unspecified form. While this description helps to identify defects in diamonds there could be other defects as well.

[00013] Diamonds in the normal color range are colorless through light yellow and are described using the industry’s D-to-Z color- grading scale. Fancy color diamonds, on the other hand, are yellow and brown diamonds that exhibit color beyond the Z range, or diamonds that exhibit any other color face-up. These rare specimens come in every color of the spectrum, including, most importantly, blue, green, pink, and red.

[00014] Because of high value commanded by colorless or colored diamonds as elaborated above, techniques exist to alter a naturally colored diamond to a‘fancy’ color, or make it colorless. These techniques include High Pressure High Temperature (HPHT) technique, electron bombarding and annealing process and are carried out in combination or individually as appropriate. Identification of suitable diamonds for such processes is done by infrared absorption spectroscopy, photoluminescence or other chemical analysis. Identification of diamonds for HPHT treatment is art which cannot be possessed without deep experience and study of color center as described above. Only perfect type 2A diamond can be perfect colorless as per Gemological Institute of America (GIA) certification. [00015] In 1954, Francis P. Bundy, H.M. Strong, Howard Tracy Hall and others working at General Electric proved that diamond can be made in laboratory. Success in production of man-made diamonds further gave a strong push to HPHT treatment for altering color and properties of both natural diamonds as well as lab grown diamonds.

[00016] Essentially, present HPHT processes involve subjecting diamonds to pressures varying from 5 GPa (gigapascal) to 11 GPa and temperatures from 1100 Degrees Centigrade to 3500 Degrees Centigrade, Various designs of presses used in HPHT treatment include cubic press, bars press, belt press, toroidal press etc. For good results of HPHT treatment, correct development and maintenance of right amount of pressure and temperature in a diamond undergoing HPHT treatment is very important.

[00017] All HPHT techniques aim to hold a diamond under very high constant pressure, generation of an elevated temperature and concentration of that elevated temperature in the diamond. For the purpose, a diamond is placed into a diamond holding device (interchangeably termed as a diamond container or a diamond cell herein) that can include a material with semi fluid properties at HPHT conditions. The diamond cell is in turn mounted between two faces of a die, such faces being made of appropriate materials (for example, tungsten carbide) that can withstand the high pressure and temperature of the process. The diamond container with the die is next mounted between anvils of a high pressure apparatus such as a toroidal press.

[00018] Design of current diamond holding devices leads to a very high rate of damage to diamonds undergoing HPHT treatment. Quality and color of diamonds after such treatment in existing devices also needs improvement. Hence, there is a need in the art for a better such devices.

[00019] In some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[00020] As used in the description herein and throughout the claims that follow, the meaning of “a,”“an,” and“the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of“in” includes“in” and“on” unless the context clearly dictates otherwise.

[00021] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g.“such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[00022] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

OBJECTS OF THE PRESENT DISCLOSURE

[00023] Some of the objects of the present disclosure, which at least one embodiment herein satisfies are as listed herein below.

[00024] It is an object of the present disclosure to provide for a diamond holding device that reduces damage to diamonds undergoing HPHT treatment.

[00025] It is an object of the present disclosure to provide for a diamond holding device that improves quality and color of the diamonds after HPHT treatment. SUMMARY

[00026] The present disclosure relates to a device for improving color of a diamond. In particular, present disclosure pertains to a diamond holding device to hold one/more diamonds while performing HPHT treatment on them.

[00027] This summary is provided to introduce simplified concepts of a diamond holding device for high pressure high temperature (HPHT) treatment of diamonds. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended for use in determining/limiting the scope of the claimed subject matter.

[00028] In an aspect, present disclosure elaborates upon a diamond holding device for high pressure high temperature (HPHT) treatment of at least one diamond. The device can include: an outer body with a hole; a pair of second plates adapted to be received within the hole oriented perpendicular to longitudinal axis of the hole; an assembly comprising a heat generating mechanism backed by a heat refracting ring, the assembly adapted to be located between the second plates along longitudinal axis of the hole, wherein the heat generating mechanism can have an inner cavity configured to be filled with a pressure and heat transmitting (PHT) medium, the pressure and heat transmitting medium configured to hold the at least one diamond; a pair of first plates configured to hold the PHT medium within inner surface of the first plates;a pair of rings inserted in the hole and configured to retain the pair of second plates within the hole; anda pair of third plates, each of the third plates adapted for insertion in an inner hallow space of the corresponding ring of the pair of ring, wherein the pair of third plates can be configured to transmit pressure put on them via the set of second plates and the set of first plates to the PHT medium while the PHT medium can be heated using the heat generating mechanism and the heat refracting ring can assist assists in retaining heat within the PHT medium, thereby performing HPHT treatment on the at least one diamond.

[00029] In another aspect, the heat generating mechanism can include a ring having any or a mixture of a salt, graphite and any form of chloride, bromide or iodide of sodium or cesium or potassium or zirconia or mixture thereof.

[00030] In yet another aspect, the heat refracting ring can carry any or a mixture of stabilized zirconia, cesium chloride, sodium and graphite. [00031] In an aspect, the pair of first plates can be made of any or a combination of heat refractory stabilized zirconia , cesium chloride, and sodium and graphite mixture

[00032] In another aspect, the pair of second plates can include graphite chips.

[00033] In yet another aspect, the pair of rings can be made of graphite.

[00034] In an aspect, the pair of third plates can be made of big chips of any or a combination of zircon, cesium chloride, sodium and graphite.

[00035] In another aspect, the outer body can be made of pyrophyllite or limestone or another form of calcium carbonate.

[00036] In yet another aspect, to heat the at least one diamond electricity can be passed through the pair of rings, the pair of second plates and the heat generating mechanism.

[00037] In an aspect, the pair of third plates can be configured to have a convex outer surface.

[00038] In another aspect, the PHT medium can be made at least of graphite.

[00039] In yet another aspect, the device can be used with a toroidal press die.

[00040] Using constructional features and materials as elaborated above leads to a diamond holding container in which diamonds can be subjected to appropriate pressures and temperatures to perform HPHT treatment on them, with lesser damage to the diamonds and better quality and color after HPHT treatment.

[00041] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like features.

[00042] Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF DRAWINGS

[00043] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[00044] The diagrams are for illustration only, which thus is not a limitation of the present disclosure, and wherein:

[00045] FIG. A illustrates a diamond holding device that can hold diamond(s) to be subjected to HPHT treatment, in accordance with an exemplary embodiment of the present disclosure.

[00046] FIG. B illustrates a toroidal die assembly to hold diamond holding device as described in FIG. A in accordance with an exemplary embodiment of the present disclosure.

[00047] FIGs. C and D illustrate various configurations of a diamond holing device holding matrix in accordance with an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

[00048] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[00049] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.

[00050] If the specification states a component or feature“may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[00051] As used in the description herein and throughout the claims that follow, the meaning of “a,”“an,” and“the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of“in” includes“in” and“on” unless the context clearly dictates otherwise. [00052] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[00053] In some embodiments, the numbers expressing quantities or dimensions of items, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term“about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[00054] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.

[00055] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[00056] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. These exemplary embodiments are provided only for illustrative purposes and so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. The invention disclosed may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Various modifications will be readily apparent to persons skilled in the art. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention.

[00057] Thus, for example, it will be appreciated by those of ordinary skill in the art that the diagrams, schematics, illustrations, and the like represent conceptual views or processes illustrating systems and methods embodying this invention.

[00058] In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as“above,”“below,”“upper,”“lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.

[00059] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[00060] The use of any and all examples, or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[00061] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[00062] The present disclosure relates to a device for improving color of a diamond. In particular, present disclosure pertains to a diamond holding device to hold one/more diamonds while performing HPHT treatment on them.

[00063] In an aspect, present disclosure elaborates upon a diamond holding device for high pressure high temperature (HPHT) treatment of at least one diamond. The device can include: an outer body with a hole; a pair of second plates adapted to be received within the hole oriented perpendicular to longitudinal axis of the hole; an assembly comprising a heat generating mechanism backed by a heat refracting ring, the assembly adapted to be located between the second plates along longitudinal axis of the hole, wherein the heat generating mechanism can have an inner cavity configured to be filled with a pressure and heat transmitting (PHT) medium, the pressure and heat transmitting medium configured to hold the at least one diamond; a pair of first plates configured to hold the PHT medium within inner surface of the first plates; a pair of rings inserted in the hole and configured to retain the pair of second plates within the hole; and a pair of third plates, each of the third plates adapted for insertion in an inner hallow space of the corresponding ring of the pair of ring, wherein the pair of third plates can be configured to transmit pressure put on them via the set of second plates and the set of first plates to the PHT medium while the PHT medium can be heated using the heat generating mechanism and the heat refracting ring can assist assists in retaining heat within the PHT medium, thereby performing HPHT treatment on the at least one diamond. [00064] In another aspect, the heat generating mechanism can include a ring having any or a mixture of a salt, graphite and any form of chloride, bromide or iodide of sodium or cesium or potassium or zirconia or mixture thereof.

[00065] In yet another aspect, the heat refracting ring can carry any or a mixture of stabilized zirconia, cesium chloride, sodium and graphite.

[00066] In an aspect, the pair of first plates can be made of any or a combination of heat refractory stabilized zirconia , cesium chloride, and sodium and graphite mixture

[00067] In another aspect, the pair of second plates can include graphite chips.

[00068] In yet another aspect, the pair of rings can be made of graphite.

[00069] In an aspect, the pair of third plates can be made of big chips of any or a combination of zircon, cesium chloride, sodium and graphite.

[00070] In another aspect, the outer body can be made of pyrophyllite or limestone or another form of calcium carbonate.

[00071] In yet another aspect, to heat the at least one diamond electricity can be passed through the pair of rings, the pair of second plates and the heat generating mechanism.

[00072] In an aspect, the pair of third plates can be configured to have a convex outer surface.

[00073] In another aspect, the PHT medium can be made at least of graphite.

[00074] In yet another aspect, the device can be used with a toroidal press die.

[00075] Using constructional features and materials as elaborated above leads to a diamond holding container in which diamonds can be subjected to appropriate pressures and temperatures to perform HPHT treatment on them, with lesser damage to the diamonds and better quality and color after HPHT treatment.

[00076] The present disclosure relates to the field of diamonds industry. More particularly, the present disclosure relates to a device for improving color of a diamond.

[00077] FIG. A illustrates a diamond holding device that can hold diamond(s) to be subjected to HPHT treatment, in accordance with an exemplary embodiment of the present disclosure. [00078] In an aspect, present disclosure elaborates upon a novel construction of a diamond holding device (interchangeably termed as diamond container or diamond cell herein) that holds the diamond in an HPHT process.

[00079] As illustrated in FIG. A, the disclosed diamond holding device 100 can be so configured as to have at its center a graphite block shown as (1) in FIG. A. Graphite block (1) can hold diamond (or a plurality of diamonds illustrated as (9). The graphite block can serve as a pressure and heat transmitting (PHT medium and transfer pressure and heat to the diamond(s) held in it in order to perform the HPHT procedure.

[00080] The graphite block (1) can be surrounded/enclosed/held in in appropriate heat generating mechanism. In an exemplary embodiment, as shown, a heater ring (3) can be placed next to graphite block (1). Ring (3) can have a mixture of any salt and graphite. For instance, sodium chloride and graphite can be used. Also any form of chloride, bromide or iodide of sodium or cesium or potassium or zirconia or mixture of thereof can be used.

[00081] Ring (3) can in turn be enclosed in a ring (4) that can be termed as a heat refracting ring. Ring 4 can carry / be made of a mixture of stabilized zirconia or cesium chloride or sodium and graphite. Ring (3) and ring (4) can easily be put together (for instance, ring 3 can slide into ring 4) and considered as a single assembly.

[00082] On its upper and lower sides, the graphite block (1) can be held in a pair of plates 2 (shown as plate 2(a) on upper side and plate 2(b) on lower side. Plates (2) can be made of heat refractory stabilized zirconia or cesium chloride or sodium and graphite mixture.

[00083] Plates (2), ring (3) and ring (4) can in turn be held between a pair of plates (5) on their upper and lower sides. Plates 5 are illustrated as 5a on the upper side and 5b on the lower side and can comprise of graphite chips.

[00084] This whole assembly (Plate (2), ring (3) , ring (4) and plate (5) as elaborated above ) can in turn be covered on upper and lower side by another pair of plates (7) ( shown as 7(a) and 7(b)).Plates (7) can be made of big chips of zircon or cesium chloride or sodium and graphite. Plates (7) can be surrounded by a graphite ring (6) and graphite ring (6) can be in turn surrounded by outer body (8) that can be made of any soft stone like pyrophyllite or limestone.

[00085] In order to perform HPHT treatment, one or more diaomonds may be embedded in the PHT medium and then the diamond holding device can be held in a press in such a manner that appropriate pressure is imparted to third plates, while at the same time the PHT medium can be heated using heat generating mechanism (3). For such heating, electricity can be made to pass through graphite ring (6), plate (5), and ring (3). Plate (2) made of heat refractory stabilized zirconia and graphite mixture helps maintain a pre-determined temperature at the graphite block.

[00086] The pressure can be transferred to the PHT medium being heated and in this manner, the diamond(s) held in the PHT medium can undergo HPHT treatment.

[00087] As can be appreciated, size of diamond holding device /container 100 can be varied according to size and quantity of the diamond(s) to be held.

[00088] In this manner, present disclosure elaborates upon a diamond holding device that can be used with appropriate presses /dies such as a toroidalpress die to alter of color of natural diamonds/lab grown diamonds by performing HPHT treatment on them.

[00089] The diamond holding device can include:an outer body (8) with a hole; a pair of second plates (5) adapted to be received within the hole oriented perpendicular to longitudinal axis of the hole; an assembly comprising a heat generating mechanism (3) backed by a heat refracting ring(4), the assembly adapted to be located between the second plates (5) along longitudinal axis of the hole, wherein the heat generating mechanism (3) can have an inner cavity configured to be filled with a pressure and heat transmitting (PHT) medium ( 1 ) , the pressure and heat transmitting medium (1) configured to hold the at least one diamond (9) ; a pair of first plates (2) configured to hold the PHT medium (1) within inner surface of the first plates (2); a pair of rings (6) inserted in the hole and configured to retain the pair of second plates (5) within the hole; and a pair of third plates (7), each of the third plates adapted for insertion in an inner hallow space of the corresponding ring of the pair of rings (6), wherein the pair of third plates (7) can be configured to transmit pressure put on them via the set of second plates (5) and the set of first plates (2) to the PHT medium ( 1 ) while the PHT medium ( 1 )can be heated using the heat generating mechanism (3) and the heat refracting ring (4) can assist assists in retaining heat within the PHT medium (1), thereby performing HPHT treatment on the at least one diamond

(9).

[00090] The PHT medium (1) can be a graphite block. The heat generating mechanism (3) can be a ring having a mixture of a salt and graphite. The ring (3) can, in turn, be enclosed by a heat refracting ring (4) that can carry a mixture of stabilized zirconia and graphite. The graphite block(l) can be held in-between two plates (that can be termed as first plates, shown as 2a and 2b, collectively termed as 2, wherein one of them can be the upper plate and the other can be a lower plate). The first plates (2) can be made of heat refractory stabilized zirconia and graphite mixture.The first plates (2), ring (3) and heat refracting ring (4) can, in turn, be held between two other plates (that can be termed as second plates, shown as 5a and 5b, collectively termed as 5) on their upper and lower sides. This whole assembly (plates 2, heater ring 3 , heat refracting ring 4, and plates 5) can, in turn, be covered on its upper and lower side by third plates shown as 7a and 7b, collectively termed as 7) made of big chips of zircon and graphite. A plate 7 can be held in place by inserting it into an inner hallow space of a corresponding ring of a pair of rings (6). The heat refracting ring (4) can be surrounded by an outer body (8) that can be made of any soft stone like pyrophyllite or limestone. It can be readily understood that the outer body (8), ring 4 and ring 3 can form concentric rings.

[00091] While above construction is explained using rings and plates, any other suitable shapes can be likewise devised. For instance, rings can be substituted by cylinders or concentric spheres holding/ comprising various materials as elaborated above, or concentric cubes can be made of various materials as elaborated above, or a combination of spheres and cubes can be used. All such embodiments and shapes are fully a part of the present disclosure.

[00092] Diamond container/holding device 100 as elaborated in FIG. 1 has several novel features and advantages. Outer body (8) made of soft stone such as pyrophyllite is used in the diamond cell proposed. It serves to reduce blast and diamond graphitization at HPHT condition. Diamond container disclosed helps focus generation of temperature/ heat in the pressure and heat transmission medium (1) using heater ring(3) that surrounds the PHT medium. Construction of the diamond container as elaborated above helps achieve a hemispherical shell type shape of the diamond container due to which pressure distribution in the diamond holding device/container elaborated is even. Heat refractory material used in plates 7a and 7b help protect the tungsten carbide (TC) die matrix ( that holds the diamond cell during HPHT treatment, as further elaborated) at high temperature, thereby increasing the life span of the TC matrix by about three times.

[00093] FIG. B illustrates a toroidal die assembly to hold diamond holding device as described in FIG. A in accordance with an exemplary embodiment of the present disclosure.

[00094] As illustrated in FIG. B, diamond cell /diamond holding device 100 as described above can be held in toroidal die assembly comprising two identical faces configured to be opposite to each other, using which diamond cell 100 (and so, diamond 9 held in it) can be subject to appropriate pressure. Each face can in turn be made of a number of sub -components /matrices that are further described. In FIG. B the parts are identically labelled, adding‘a’ for such a component on one face, and‘b’ for a similar component configured on the opposite face.

[00095] Toroidal die assembly can have a block (that can be interchangeably termed as matrix or block matrix) shown as (X) in turn having a block/matrix (20) via which high pressure can be transmitted from the toroidal die assembly to the diamond cell. Matrix 20 can be surrounded by concentric rings shown as internal ring (19), intermediate ring (18) and outside ring(17) made of mild steel that can serve as support to matrix 20 due to their high tensile strength. Matrix 20 can be made of tungsten carbide (TC) and its construction is important for maintaining proper pressure on the diamond cell. The construction of matrix 20 is elaborated in FIGs. C and D.

[00096] Block matrix X can be held/attached (on both sides of the toroidal die assembly) on a support plate (shown as Y) that can transfer pressure and also remove unwanted heat from the block matrix X. Support plate Y can have an insert (16) for transferring high pressure to block matrix X. Insert 16 can be surrounded by fastening ring (15) that can in turn be surrounded by external ring (14). These rings can serve as support to insert 16 due to their high tensile strength. A refrigerating coil (13) can be mounted around ring 14 to remove unwanted heat from block matrix X. The rings can be made of mild steel.

[00097] Support plate Y can in turn be held/attached (on both sides of the toroidal die) to a backing plate (shown as Z) that can enable pressure transfer to support plate Y. Backing plate Z can have insert (shown as 12) for transferring high pressure to support plate Y. Body (11) can hold/support insert 12 due to its high tensile strength.

[00098] Backing plate Z can in turn be held/attached (on both sides of the toroidal die) to a base plate (shown as 10) that can be used for transferring and holding pressure on to backing plate Z.

[00099] As can be readily understood, blocks, matrices, inserts etc. as elaborated above can be made of any suitable material to fulfil their purpose, and can be shaped accordingly. Some of such components (for instance inserts) may not be needed if their function may as well be done by the blocks in which they are configured. Rings can as well be of cylindrical or any other suitable shape. [000100] As illustrated , diamond cell 100 can be held in appropriate space ( shown as 24 in FIGs. C and D further elaborated) configured in matrix 20, and surrounded by one/more toroid rings (toroidal belts) held in grooves configured in matrix 20. One such ring is shown as 21 in FIG. B. The rings can enclose those surfaces of diamond cell 100 not directly receiving pressure from block matrix X and so can help retain pressure in the diamond cell 100.

[000101] FIGs. C and D illustrate various configurations of a diamond holding device holding matrix in accordance with an exemplary embodiment of the present disclosure.

[000102] As already said above, matrix 20 (20a being on one face of the die, the opposite face having 20b) is used for transferring high pressure to diamond cell 100. Hence its construction is important and elaborated as under.

[000103] In an exemplary embodiment, matrix 20 can be of single toroid type having only one toroidal groove (shown as 25 in FIG. D) and one center portion (shown as 24 in FIG.D). A toroidal ring (such as ring 21 shown in FIG. B) can be held in toroidal groove 25, while diamond container (as elaborated in FIG. A) can be held in center portion 24. The toroidal ring/belt helps to hold pressure and make equivalent balance between upper and lower TC die matrix.

[000104] In another exemplary embodiment, a double toroidal matrix as shown in FIG.C can be designed for ultra-high pressure holding of diamond containerlOO. In such a matrix, shown as 20 (20a being one side and 20b the opposite) in FIG. C, two toroidal grooves shown as 22 and 23 can be configured around a center portion shown as 24. As before, grooves 22 and 23 can each contain toroidal rings/belts while center portion 24 can hold diamond holding device /diamond container 100.

[000105] Since the diamond cell is held in a die assembly as described above using a matrix (matrix 20) that can be thought of as holding one/more belts of toroidal shape, the whole configuration can as well be termed as toroidal die assembly or toroidal belt die/toroidal belt die assembly.

[000106] Each component of the die assembly described serves to transmit pressure to the diamond container as described in FIG.A. A ring with toroidal shape called toroid ring (as illustrated in FIG. C and FIG. D) is placed around the diamond container (in corresponding groove in the TC matrix) and serves to hold the pressure in/ around the diamond container.

[000107] Matrix 20 may be made of tungsten carbide and helps hold critical pressure and temperature parameters in the diamond cell. [000108] Center portion in the toroidal die assembly (Zone 24 in FIG. C and Zone 24 in FIG. D) serves to hold the diamond container in the die assembly described. Dimensions of this portion can vary from 15 mm to 50mm depending upon size of the diamonds and design of the diamond container. In an exemplary embodiment, height of the TC die matrix can vary +/-20% of usual current height of 40 mm of existing TC die matrices.

[000109] In an exemplary embodiments, some types of diamonds may require ultra-high pressure like lOGPa to 12GPa. In these cases, diamond container and toroid ring as described above may relieve pressure during process which could create partial or full graphitization of diamond. For safety of most valuable gemstones it is more practical to use double toroidal die matrix as described in FIG.C. The double toroidal matrix has first toroidal groove (22) next to center portion which primarily help to convey pressure from container, and a second toroidal groove (23) is added next to first toroidal groove.

[000110] In operating conditions, a diamond is placed inside the diamond cell with material having semi fluid liquid at HPHT condition around the diamond. All materials used in construction of diamond cell must be thermally and chemically stable, and it must not react with diamond. For instance, such material could be salt such as fulfill above quality or carbons like graphite (as used in graphite block, for instance). Heater ring (shown as 3 in FIG.A) is placed around the diamond cell for generation of proper heat from electricity. The heater ring can be made from sodium chloride or any form of chloride, iodide, and bromide of materials like potassium, sodium, or calcium or mixture of it.

[000111] During HPHT treatment of a diamond, electricity is passed through heater ring(3) and graphite block(l) and due to various materials’ higher resistance to electricity, temperature is generated around diamond held in diamond cell. The temperature is held constant inside the diamond cell for a pre-determined time. For the purpose, heat refracting ring (shown as 4 in FIG. A) made of refractory materials such alumina, magnesite, zirconia or chromite can be configured around heater ring 3.

[000112] The diamond container as described above (FIG. A) can be placed inside toroidal die assembly (FIG. B) and surrounded by toroidal ring (FIG. C and FIG. D). The diamond container supported by tungsten carbide die can be exposed to high pressure. Pressure of 5 GPa to 11 GPa and temperature of 1200 degrees centigrade (Deg C or C) to 3500 C is created. The temperature should be below graphitization line according to relative pressure from Simon- Berman line of diamond stable region. Such high pressure high temperature (HPHT) treatment is given to diamond held in the diamond container for adequate time to improve the diamond. Process parameter can be selected from the above range or any other range depending upon nature of defect in the diamond, as required to change or remove the color of the diamond. Skills and experience can help identify such parameters without excessive experimentation.

[000113] Most natural diamond contain brownish color, some of the natural diamonds hold a fancy color. Every natural diamond has a hidden color beneath its original color and the hidden color can be revealed by appropriate HPHT process.

[000114] For instance, a Type Ila diamond may be rendered colorless by HPHT procedure whereas a type IIB diamond can have a blue color after HPHT treatment. Some type Ila diamonds can also develop pink color consequent to HPHT treatment.

[000115] In an exemplary embodiment, HPHT treatment can be done upon a natural brown diamond using equipment and process as described above. The diamond cell (1) can be made of pure graphite or any salt or sodium chloride. Diamond cell (1) can be placed inside a mixture of any salt (such as sodium chloride, calcium chloride etc.) and graphite ring (3) and together this assembly can be held within ring of mixture of stabilized zirconia and graphite (4), and fitted with end discs (2a, 2b) made from mixture of stabilized zirconia as major percentage and minor percentage of graphite. Graphite discs (5a, 5b) and graphite rings (6a, 6b) can be further provided for a stable electrical path. The diamond cell /container can be covered by big chips of refractory material of stabilized zirconia and graphite mixture and then put inside a container of soft rock like pyrophyllite or limestone.

[000116] Container as made above can be placed inside the toroidal die assembly or toroidal belt die assembly as described. A pressure 100 % of a pre -determined pressure can be achieved and kept constant for a pre-determined time. During this time initially 60-80% of a target /pre-determined temperature can be achieved and maintained for 2 to 5 minutes in a first stage, and then maintained constant for next 10 seconds to one hour (preferably 20 seconds to 5 minutes, for instance). After completion of the first pre-determined time, pressure can be slowly brought to atmospheric pressure in 4 to 8 minutes. During this period of 10 seconds to one hour, electricity is passed through the diamond container thereby generating temperature in the diamond container and annealing the diamond held therein. [000117] Thereafter, the HPHT treated diamond container can be removed from the toroidal die assembly and diamond recovered by removing surrounding rings etc. by hammering on them. A diamond after HPHT treatment can have etch marks carrying graphite on its surface. Such marks can be removed by digesting the diamond into a high temperature mix of sulphuric and nitric acid.

[000118] In an exemplary embodiment, a 1.69ct natural stone type Ila of original color light brown br2 or as per GIA Q to R was taken. Diamond and graphite were compacted into diamond cell by press machine, height and diameter of diamond cell being respectively 7.5mm (millimeter) and 12mm respectively. Diamond was annealed for 1 minute and 30 seconds at around 2400 C and 8.6GPa. The resultant diamond was fancy light pink.

[000119] In another exemplary embodiment, a 1.72ct natural type lib stone of initial color light brown grade br2 or as per GIA Q to R was taken. It was placed inside diamond cell of height and diameter of 8.5mm and 15mm respectively. Annealing of diamond was done for two minutes at around 2550 Deg C and 8.6GPa. The diamond became faint blue as a result of HPHT process.

[000120] In yet another exemplary embodiment, an 8.55ct natural stone type Ila of original color very light brown brla or as per GIA M to P was taken. It was placed inside the diamond cell height and diameter of 9.5mm and 15mm respectively, and annealed for 2 minutes at around 2600 C and 8.6GPa pressure. After HPHT treatment diamond possessed D-E color as per GIA colorless grading.

[000121] In an exemplary embodiment, a 12.59ct natural stone type Ila of initial color very light brown brla or as per GIA M to P and clarity of VVS was placed inside a diamond cell height and diameter of 10.5mm and 18mm respectively. Diamond was annealed for 2m i mites 30sec at around 2500 C and 8.3GPa. As result diamond became D to E colorless as per GIA grading.

[000122] In another exemplary embodiment, a 12.65ct natural stone type Ila of initial color very light brown brla or as per GIA M to P and clarity of VVS was placed inside a diamond cell height and diameter of 10.5mm and 18mm respectively. Diamond was annealed for 2 minutes at around 2600 C and 8.6GPa. Diamond has obtained colorless grade of GIA having D-E grade.

[000123] In yet another exemplary embodiment, a 2.37ct CVD stone initial color light brown and clarity of VVS was placed inside the diamond cell of height and diameter of 8.5mm and 15mm respectively. Diamond was annealed for 40 seconds at around 2000 C and 8GPa pressure. After HPHT treatment diamond obtained near colorless G to H grade of GIA.

[000124] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

[000125] As used herein, and unless the context dictates otherwise, the term“coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other or in contact with each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms“coupled to” and“coupled with” are used synonymously.

[000126] Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms“comprises” and“comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C ... .and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.

[000127] While some embodiments of the present disclosure have been illustrated and described, those are completely exemplary in nature. The disclosure is not limited to the embodiments as elaborated herein only and it would be apparent to those skilled in the art that numerous modifications besides those already described are possible without departing from the inventive concepts herein. All such modifications, changes, variations, substitutions, and equivalents are completely within the scope of the present disclosure. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. ADVANTAGES OF THE INVENTION

[000128] The present disclosure provides for a diamond holding device that reduces damage to diamonds undergoing HPHT treatment.

[000129] The present disclosure provides for a diamond holding device that improves quality and color of the diamonds after HPHT treatment.

[000130] The present disclosure provides for a diamond holding device that has an outer body made of soft stone to reduce blast and diamond graphitization at HPHT condition.

[000131] The present disclosure provides for a diamond holding device that is configured to focus generation of heat in its pressure and heat transmitting (PHT) medium using a heat generating mechanism that surrounds the PHT medium.

[000132] The present disclosure provides for a diamond holding device that has a hemispherical shell type shape due to which pressure distribution in the device is even.

[000133] The present disclosure provides for a diamond holding device that uses appropriate refractory materials in its outer plates to help protect tungsten carbide (TC) die matrix that holds the device during HPHT treatment at high temperature thereby increasing the life span of the TC matrix by about three times