Preparation And Properties Of Zr₂P₂WO₁₂/Ni Composite Materials

Zr2P2WO12(ZWP) is one of the materials with negative thermal expansion coefficient. It has excellent chemical stability, thermal stability, mechanical stability in the wide tempreture span(25℃-800℃), and it has important application prospect.Ni is an important industrial material with large positive thermal expansion coefficient. It is important to adjust the coefficient of thermal expansion when the metal Ni is used in some precise instruments, such as satelite antenna and other materials that are sensitive to thermal expansion. We prepared the composite materials ZWP/Ni and studied their properties in this paper.Cermets and alloys composite materials were prepared by sintering of biscuits in traditional method, and the biscuits were suppressed by cermets and alloys powders that have been prepared respectively, and they were mixture uniformily in ball grinding mill. But this method has some disadvantages: First, it could mingle other materials in grinding mill process; Second, the powders could be aggregate after grinding mill process, and the grain size is the level of micrometer; Third, the component of the composite materials don’t distribute uniformly. The controlled thermal expansion composites ZWP/Ni powders was prepared by sol-gel and chemical co-precipitation method in one-step, respectively. The chemical reaction was proceed in liquid phase environment, and it made the components of the material precursor mixture uniformly in molecule level.The main work has the several parts as follows in this paper:(1) The ceramics ZWP and composites ZWP/Ni powders were prepared using sol-gel method. And the gel experienced the process of soften, decompose of orgnics,discharge of gas, the oxidation of carbon, the reaction of ceramics ZWP.(2) The composites ZWP/Ni powders were prepared using co-precipitation method, and The metal Ni was restored by the citric acid in the sintering process. The ceramic particles size is 100-200 nm, while the metal particles size is 50-100 nm. The component of the composite materials distribute uniformly because of that the chemical reaction was proceed in liquid phase environment.(3)The testsamples were prepared by two methods of the cold pressing and the hot pressing. The powders were pressed into the blocks using the oil press,then the samples were heated in a vacuum tube furnace under the static N2 environment in cold pressing; The testsamples were prepared by SPS technical in hot pressing. As the comparison between the SPS technique and the cold pressing, the sample prepared by the former has larger relative density.(4)Results show that the thermal expansion property of the ceramic metals can be well controlled or tuned by mixing different mass ratios of ZWP and Ni.