Nano Zirconium Tungstate Powder Preparation by Coprecipitation Method

In recent years, in the application of automobile, energy and other fields, materials need to have the properties of corrosion resistance, high temperature resistance, heat conduction and so on. Special ceramics are needed to meet the development of its application. Zirconium tungstate material has negative expansion. It has strong isotropic negative thermal expansion effect in the temperature range of 0.3-1050K. Its negative thermal expansion coefficient (NTE) is -9*10-6K^-1, which is one of the hotspots in the research of negative expansion materials.

However, ZrW₂O₈ is thermodynamically stable only in a very narrow temperature range of 1105-1231 ℃. Above this temperature, an amorphous glass state of ZrO₂-WO₃ will be formed, and below this temperature, ZrO₂ and WO₃ will be decomposed into ZrO₂ and WO₃ at 780-1105 ℃. Therefore, in order to maintain the thermodynamic stability of ZrW₂O₈ material, the product must be quenched and quickly jumped over the decomposition zone. Therefore, the preparation process of ZrW₂O₈ material is very complex.

In order to solve many technical problems of nano zirconium tungstate powder prepared by existing methods, some scholars have prepared nano zirconium tungstate powder by coprecipitation method. The contents of nano zirconium tungstate powder include:

1.Weighing raw materials zirconium oxychloride and ammonium tungstate in zirconia crucible, sintering in air for 5 hours in a box furnace at 800 ℃. The contents of Zr₄⁺ and W₆⁺ in raw materials are calibrated according to the residual ZrO₂ and WO₃. According to the molar ratio, certain quality raw materials are dissolved in distilled water, and the solutions with Zr₄⁺ concentration of 0.02mol/L and W₆⁺ concentration of 0.04mol/L are prepared.

2.Adding dispersant to the solution with W₆⁺ concentration of 0.04 mol/L and adjusting the pH value to 6, the solution a is obtained.

3.Add the solution of Zr₄⁺ concentration of 0.02mol/L to solution a, stir rapidly, adjust the pH value to 1.5-4, mix for 1 hour, rest for 12-24 hours, carry on ageing treatment, remove supernatant, vacuum drain and filter the precipitate. The product is dried in a drying box at 100 ~℃, grinded fine, and reacted in a box oven at 600 ~2 hours, then reacted at 1140~1200 ~2 hours, and discharged. Zirconium tungstate powder was obtained by water quenching and dry grinding.

The powder prepared by coprecipitation method has the advantages of simple process, high purity and low production cost. The prepared zirconium tungstate material has great prospects in the application of high precision electronic equipment or optical microscope, precision optical mirror, dental filling material and substrate material.

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