Preparation And Properties Of FeNi And Al₂O₃composites Filled With Zr₂WP₂O₁₂ With Negative Thermal Expansion

Thermal expansion of Materials is wide spread in nature and difficult to be eliminated. In many cases, it may affect the application of materials. Negative thermal expansion or nearly zero expansion materials can improve the influences generated by the thermal expansion of the materias. Negative thermal expansion material is a kind of material whose volume shrinks with the temperature increasing.Among the negative thermal expansion materials, Zr₂WP₂O₁₂（ZWP） has excellent negative thermal expansion properties in the temperature of 293-873 k. ZWP also has other excellent properties, such as excellent chemical and thermal stability, good performance under large press and no phase transition in large remperature range. It is an effective method to improve the thermal expansion coefficient of other materials by incorporating negative thermal expansion material.ZWP powder with nanoparticles was prepared by hydrothermal method in this paper. ZWP ceramics and its Al₂O₃-based composites were prepared by cold pressing sintering method. ZWP/FeNi composites were prepared by Spark Plasma Sintering（SPS）. The properties of ZWP and its composites were analyzed by XRD, SEM,thermal analyzer, vickers hardness tester, impendence tester and thermal expansion instrument. The influences of different ZWP content on the properties of its FeNi and Al₂O₃ composites were studied. The results are as follows:1. ZWP powder with nanoparticls was prepared by hydrothermal method with optimized preparation technology. Thermal and electrical properties of ZWP were studied. The optimized preparation technology is PH=7⁹, T=303K, t=48h. The sintering temperature is 1173 K and holding time is 4h.2. ZWP/FeNi composites with different ZWP content were prepared by SPS technique. With ZWP content increasing in the composites, the thermal expansion coefficient of the composites decrease and hardness increase. When ZWP content in the composite is 30%, the hardness can be enhanced by 116%.3. ZWP/ Al₂O₃ composites with different ZWP content were prepared by the method of cold pressing sintering. With ZWP content increasing in the composites,both the thermal expansion coefficient and dielectric constant of the composite decrease. The dielectric loss keep stable. Average linear thermal expansion coefficient decreased from 7.78 ×l0-6K-1 to 4.80 ×l0-6K-1 in temperature range of 293-873 k.