Recently, zirconium tungstate is the best isotropic negative thermal expansion compound, and also the typical compound which have attracted great interest from the crystal structure to heat-shrinkable properties in new negative thermal expansion compound. Studies have pointed out that dope the other elements into basal body of can change its properties, and it will have a very broad application prospect. A method that use ammonium paratungstate as raw material to prepare cerium-doped zirconium tungstate negative thermal expansion ceramic powder, steps as follows:

1. Take materials: weight eight water zirconium oxychloride, ammonium paratungstate and cerium ammonium nitrate according to a certain stoichiometry, mix the zirconium oxychloride and cerium ammonium nitrate and dissolved in deionized water; at the same time, ammonium paratungstate also dissolved in deionized water, and make sure the concentration of W equals to the summation of concentration of Ce and Zr;
2. Mix the deionized water and concentrated hydrochloric acid at a certain volume ratio to get the hydrochloric acid solution at a concentration of 6-10mol/L;
3. Dropping the mixed solution of zirconium oxychloride and cerium ammonium nitrate, ammonium paratungstate into deionized water by the double-dropping-method with stirring, and control the temperature between 60-80℃, continually stirring for 4-8 hours;
4. Raising the temperature to 80-90°C, dropping the hydrochloric acid solution into the mixture under constant stirring conditions, until the H + concentration in the final solution is 1.5-3mol/L, and then stirring was continued for 16 to 24 hours ;
5. Translating the mixture obtained in step 3 into a teflon-lined autoclave, and heated for 12-72 hours at temperature of 165-220℃, then suction, dried at 60-85℃, so the precursor generated;
6. Placed the precursor in a muffle furnace and heated to 600-700℃, and incubated for 6-12 hours to give a final product--zirconium tungstate cerium-doped ceramic powder.

Trace element and other additives are also the common method for improving wear resistance of tungsten carbide buttons. People add some elements with specific additives and excellent performance to change the composition and properties of carbide itself to adapt to different requirements of works More common additives such as grain growth inhibitor (refined grains, inhibit grain growth), corrosion of some components (to improve corrosion resistance), some of the rare earth element or refractory metals (carbide corresponding optimization performance). The principles of influencing factors of additives on wear resistance of tungsten carbide buttons are different, some uniforms the structure by grain refined, some improves the binding strength of interface by improving the wettability of cobalt (Co) on tungsten carbide (WC).

Finally, we introduce the effects of chemical treatment on wear resistance of tungsten carbide button. Theoretically, heat treatment of tooth carbide ball can change the organizational structure of the matrix corresponding compound distribution and coordination, so as to give full play to the composite materials’ advantage. Therefore, the relevant domestic and foreign scholars and researchers have carried out extensive research on the mechanism of heat treatment on tungsten carbide button, and draw different conclusions.

At present, there are two explanations of tungsten carbide buttons heat treatment mechanism: one is thought tungsten (W) supplementary heat treatment was dissolved in Co binder phase, the contiguity of WC grain size decreased, while the WC and Co contiguity rise, thus wear resistance of tungsten carbide buttons is improved; another is thought heat treatment changes the stress state phase structure and internal Cu alloy phase, which can keep the face-centered cubic structure (fcc) a-Co binder phase at high temperatures to a large extent, reduce HCP (hexagonal closepacked structure) e-Co. The former is a plastic material, and the latter is a brittle material, thus tungsten carbide button abrasion resistance corresponding increases. In addition, there are carburizing, boron, lanthanum and other chemical heat treatment and laser treatment, ion injection, etc.

Take tungsten carbide (WC-Co) as a example, it has high hardness, high density, high strength and excellent chemical stability, but its wear resistance is poor. Related researchers have conducted extensive research, which includes three influencing factors on the wear resistance of tungsten carbide buttons, such as the grain size of solid phase (WC), trace element or additives and chemical heat treatment, etc.

According to the principle that material micro-structure determines the surface property, the researcher propose the granularity of solid phase (WC) in tungsten carbide has a great impact on the wear resistance and they do o lot of extensive researches. The experimental data shows that when the cemented carbide (WC-Co) in the hard phase (WC) grain size is reduced to sub-micron or less, to the material hardness, strength, toughness and wear resistance have been improved to some extent. The relationship of wear rate and WC grain size given as follow:

From the figure we can clearly see in the lower hardness, the hard phase tungsten carbide (WC) hardness plays a major role, while at higher hardness values, the toughness of the material take effects. With the increasing size of the WC particles, accelerated wear, wear rate did rise, but can not be considered biased nano-scale tungsten carbide (WC) particles and wear properties will certainly be advantageous for the wear mechanism and conditions are mutually reinforcing. Generally, the finer the crystal grain size that is smaller defect, the binder phase of cobalt (Co) smaller average freedom, corresponding high hardness and bending strength. With increasing hardness of tungsten carbide, WC grain size and relative sizes of the abrasive is close, no significant correlation between the wear volume losses with the hardness of the alloy.

Cesium is a golden yellow metal, low melting point active metal, easily oxidized in air and can react violently with water to produce hydrogen and even explode. There is no elemental form of cesium in nature, cesium minimal distribution in the ocean in the form of cesium salt. Cesium tungsten bronze is widely used because of its low resistance, excellent visible light transmittance, near-infrared shielding properties. Also it is widely used in preparing conductive thin film, since being the glass transparent insulation coating as insulating agent, it has excellent properties like low resistance, excellent visible light transmittance and near-infrared shielding performance. The article provides a method that using ammonium paratungstate and cesium nitrate as raw materials to produce Cesium-tungsten oxide ultrafine powder, the specific steps are as follows:



1. Weighing the cesium nitrate, ammonium paratungstate by the molar ratio of Cs/W being 1: (1.5 to 2.8), and adding chelating agent and alcohol reagent, reacting at 170°C for 3 hours;
2. Loading the mixture obtained in step 1 in a pressure vessel shells, raising the temperature to 260~270°C for reacting for 5 to 8 hours;
3. The reaction obtained in step 2 is carried out alcohol washing, centrifugation; then dried in the conditions of 80°C in vacuum, thus to generate complete crystalline cesium-tungsten powder.

Using this method to prepare cesium-tungsten oxide ultrafine powder has many advantages, such as: saving the materials, thus to save costs; shorten the preparation period, make it advantaged for industrial production; products prepared are ultrafine powders with a very low resistance.