Title of Invention: METHOD OF INCREASING THE POROSITY

OF CERAMIC JUNCTION BRIDGE

Technical Field

Technical Field

[1] The present invention relates to a method of increasing the porosity of ceramic

junction bridge.

Background Art

Background Art

[2] In potentiometric measurement, a reference electrode is equally as important as the working electrode. It completes the electrochemical cell and provides a stable reference voltage. A low-leaking porous plug is needed in conventional double- junction reference electrode to allow contact between internal reference electrolyte and the external solution, and between the external solution and the analyte. In single- junction reference electrode, the reference electrolyte is in contact with the analyte through a porous junction bridge.

[3] The porosity of the junction bridge is one of the most critical parameters in reference electrode because it controls the flow of ions in order to complete the flow of current but prevents excessive loss of reference electrolyte. The inherent pore sizes in nano- porous ceramic are often too small to allow sufficient movement of ions and to achieve stable electrochemical signal. Apparently the problem is more critical in single- junction reference electrode wherein the internal electrolyte leaks directly to the analyte or vice versa, the analyte contaminates the reference electrolyte. To overcome the above problem, the present invention provides a method of increasing the porosity of ceramic junction bridges in reference electrodes.

Disclosure of Invention

Technical Problem

[4]

Technical Solution

[5]

Summary

[6] It is an object of the present invention to provide a method of increasing the porosity of ceramic junction bridge.

[7] It is another object of the present invention to provide the method is used for

preparation of reference electrodes are selected from the list of single, double-junction silver-silver chloride or silver-silver iodide and single, double-junction calomel. [8] These and other object of the present invention is provided by a method for increasing porosity of ceramic junction bridge comprising the steps of:

[9] a) cutting a ceramic rod,

[10] b) cleaning in polar and non-polar solvents,

[11] c) further cleaning with further polar solvents and non-polar solvent,

[12] d) treating with hydrochloric acid,

[13] e) washing with dionized water, and

[14] f) drying.

Description of Drawings

[15] BRIEF DESCRIPTION OF THE DRAWINGS

[16] For a fuller understanding of the nature of the present invention, reference should be made to the following detailed description taken in connection with the accompanying drawings in which:

[17] FIG. 1: illustrates diagram of the method for increasing the porosity of ceramic rod.

[18] FIG. 2: illustrates the image from Scanning Electron Microscope (SEM) of ceramic rod Type A before refluxing process.

[19] FIG.3: illustrates the image from Scanning Electron Microscope (SEM) of ceramic rod Type A after refluxing process.

[20] FIG.4: illustrates the graph of response data for Nitrate Standard Nico for reference electrode with raw ceramic and ceramic refluxed for ceramic Type A.

[21] FIG.5: illustrates the graph of response data for Potassium Standard Nico for

reference electrode with raw ceramic and ceramic refluxed for ceramic Type A.

[22] FIG.6: illustrates the graph of response data for Nitrate Standard Nico for reference electrode with raw ceramic and ceramic refluxed for ceramic Type B.

[23] FIG.7: illustrates the graph of response data for Potassium Standard Nico for

reference electrode with raw ceramic and ceramic refluxed for ceramic Type B.

[24]

[25] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[26] The present invention relates to a method of increasing the porosity of rod ceramic materials used as junction bridges in reference electrodes . The ceramic materials are supplied as sticks having 10 to 50 cm lengths and 1 to 1.8 mm diameters, mainly made of alumina material and having nano-range pore sizes. The inherent pore sizes in nano- porous ceramic are often too small to allow sufficient movement of ions and to achieve stable electrochemical signal. The method of cleaning the commercial rod nano-porous ceramic and increasing the pore size is conducted for certain application such as junction bridges in double-junction silver-silver chloride or silver-silver iodide reference electrodes, junction bridge in single-junction silver-silver chloride or silver- silver iodide reference electrodes, junction bridges in double-junction calomel reference electrodes and junction bridge in single-junction calomel reference electrodes.

[27] Chemical treatment of the ceramic material presumably attacks the grain boundary of the structure, removes grains of materials and increases the pore size. Turning now to FIG. 1, the diagram shows a method for increasing the porosity of ceramic rod. In order to increase the effectiveness of the process, first the ceramic sticks are cut into I -cm rod pieces so that the chemicals can attack the grain boundary from larger surface area. Second, measure the total weight of ceramic pieces. Third, cleaning in polar and non-polar organic solvents to make the surface more susceptible to acid or alkali reagents. Fourth, treating with 3M hydrochloric acid for 15 hours. Fifth, washing with dionized water for 1 hour. Sixth, drying in oven for 30 minutes. Seventh, weighing the ceramic pieces and the average loss of weight per piece is calculated. Weighing the cut pieces before and after the chemical treatment gives the weight of material lost during the process. The material loss is significant, usually visible as lump of powder material at the bottom of the refluxing round bottom flask, and thus needs to be controlled in order to avoid excessive leakage of electrolyte.

[28] In one embodiment of the present invention, FIG.2 shows the image of ceramic rod Type A using Scanning Electron Microscope (SEM) before refluxing process and FIG.3 shows the image of ceramic rod Type A using SEM after refluxing process which is the pores are bigger than before. FIG.4 illustrates the graph of response data for Nitrate Standard Nico for reference electrode with raw ceramic and ceramic refluxed for ceramic Type A while FIG.5 illustrates the graph of response data for Potassium Standard Nico for reference electrode with raw ceramic and ceramic refluxed for ceramic Type A. FIG.4 and FIG.5 shows the improvement of reference electrode with refluxed ceramic, with the slope value of -50 +5 mV and 50 ±5 mV for nitrate and potassium commercial sensor response respectively.

[29] In another embodiment of the present invention, FIG.6 illustrates the graph of

response data for Nitrate Standard Nico for reference electrode with raw ceramic and ceramic refluxed for ceramic Type B while FIG.7 illustrates the graph of response data for Potassium Standard Nico for reference electrode with raw ceramic and ceramic refluxed for ceramic Type B. These two figures clearly showed an improvement of reference electrode working performance with refluxed ceramic.

[30] The present invention will be explained in more detail through the examples below.

The examples is presented only to illustrate the preferred embodiments of the present invention and not intended in any way to limit the scope of the present invention.

[31] Examples

[32] Example 1

[33] Methodology [34] First, cleaning the nano-porous ceramic rods, pre-cut to pieces of 0.2- cm to 2-cm long, with solvents mixture of hexanes, benzene and dichloromethane in 1 : 1 :1 ratio, under refluxing condition for 0.5 to 40 hours. Second, cleaning the nano-porous ceramic rods with solvents mixture of diethyl ether, tetrahydrofuran and ethanol in 1 : 1 : 1 ratio, under refluxing condition for 0.5 to 40 hours. Third, treating the ceramic rods in 0.1 to 3M hydrochloric acid (HC1) for 0.5 to 40 hours. Fourth, washing the nano-porous ceramic rods with deionized water under refluxing condition for 0.5 to 40 hour. Fifth, drying the ceramic rods in oven at 50°C to 200°C for 0.5 to 40 hours.

[35] Example 2

[36] Application on Commercial Ceramic Rod

[37] Type A (Commercial Ceramic Rod from Anderman )

[38] First, the ceramic rod was cut into small pieces of 1 centimeter length and the total weight of 5 pieces ceramic were measured with the result of 399.12mg. For Example

1, the type of ceramic refers as Type A with diameter of 1.8mm. The apparatus for reflux process were prepared with lOOmL 3M HC1 solution. Next, the pieces of ceramic and magnetic stirrer were put into the round neck bottom flask. Start the reflux process and maintain the temperature of 110°C throughout the 14-15 hours reaction. After 14-15 hours, the reflux process was discontinued and the allowed to cool down to room temperature. Then, the solution was transferred into a beaker and the ceramics were collected. After that, the ceramic needed to be reflux again with l OOmL DI water for about an hour. After an hour, the reflux process was discontinued and the ceramics were washed few times before placed into an oven for 30 minutes for drying purpose. Later, the ceramics were measured again for it weight to allow loss of weight calculation. In this sample process, the average loss of weight was 1.4mg per piece. Once the ceramic was done with the reflux process, it then will be assemble into a small rubber plug as the bottom part of the reference electrode. Based on the guideline of preparation of ceramic reference electrode, few measurements or tests need to be done in order to qualify the reference electrode. As shown in Table 1 below, the vital test was the chloride ion response with required to be less than 12mV. In this test, the ceramic reference electrode was measured with commercial Ag/AgCl double junction reference electrode. From the results in Table 1 , the performance of reference electrode with ceramic being reflux was better compared to the one with raw ceramic rod. The improvement of reference electrode with refluxed ceramic also can be seen as in Table

2, which the slope value of -50 ±5 mV and 50 ±5 mV for nitrate and potassium commercial sensor response respectively. [Table 1 ]

[Table ]

[39] Table 1: Chloride ion response data of reference electrode with raw ceramic and ceramic refluxed (Ceramic Type A)

[40] [Table 2]

[Table ]

[41] Table 2: Response data of Nitrate and Potassium Standard Nico for reference

electrode with raw ceramic and ceramic refluxed (Ceramic Type A)

[42]

[43] Example 3

[44] Type B (Commercial Ceramic Rod from W. Haldenwanger )

[45] The type of ceramic refers as Type B is coming raw ceramic rod from another

supplier. This type of ceramic has a diameter of 1.6mm with length of 13mm. The few pieces of ceramic were refluxed with 3M HCl for 14 hours followed by 5 hours in 3M KCl. Both raw ceramic Type B and refluxed ceramic Type B were assembled into reference electrodes with 3M KCl electrolyte- AgCl saturated. As followed requirement mentioned in Example 1, Table 3 and 4 clearly shown an improvement of reference electrode working performance with refluxed ceramic. [Table 3]

[Table ]

Table 3: Chloride ion response data of reference electrode with raw ceramic ceramic refluxed (Ceramic Type B)

[Table 4]

[Table ]

[47] Table 4: Response data of Nitrate and Potassium Standard Nico for reference

electrode with raw ceramic and ceramic refluxed (Ceramic Type B)

[48]

[49] Although the invention has been described with reference to particular embodiment, it is to be understood that the embodiment is merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiment that other arrangements may be devised without departing from the scope of the present invention as defined by the appended claims.

Best Mode

[50]

Mode for Invention [51]

Industrial Applicability

[52]

Sequence List Text

[53]