Preparation and thermal expansion properties of Y₂W₃O₁₂/Ni composites

In order to investigate the thermology properties of Ni-based Y₂W₃O₁₂ composites, negative thermal expansion material Y₂W₃O₁₂ was prepared by secondary solid-state method firstly. Then, Y₂W₃O₁₂ was mixed with metal Ni, and by hot pressing sintering under the conditions of 1 200 ℃ and 50 MPa, 40vol% Y₂W₃O₁₂/Ni composites were obtained. Finally, the compositions and thermal expansion properties of composites were investigated. The results indicate that during the hot pressing sintering process, comparing with the complex chemical reactions occurring in contrast sample 40vol% Y₂W₃O₁₂/Cr composite, there is no reaction occurred between the two phases of 40vol% Y₂W₃O₁₂/Ni composites, for the reducibility of Ni is weaker than that of W, which makes 40vol% Y₂W₃O₁₂/Ni composite keeps the lower coefficient of thermal expansion. After several cycle annealing to release the thermal stress and remove the crystal water of Y₂W₃O₁₂ phase, the coefficient of thermal expansion of 40vol% Y₂W₃O₁₂/Ni composite in the temperature range of 170-800 ℃ tends to be stable, which is about 3.4×10^-6 K^-1 and close to the theoretical design value of 4.0×10^-6 K^-1.