Formation of Metallic and Carbide Phases via Codecomposition of [NiEn3]WO4 and Lithium Hydride in the Range 410–1060°C

Abstract

The formation of metallic and carbide phases during the thermal decomposition of a mixture of the coordination compound [NiEn₃]WO₄ (En = ethylenediamine) and LiH in a He atmosphere has been studied by X-ray diffraction. The results demonstrate that heat treatment of the mixture at 410°C for 10 min leads to the formation of a Ni(C_x) interstitial solid solution based on the HCP Ni lattice and a W_{1 –x}Ni_x substitutional solid solution based on the BCC W lattice. Starting at 510°C, a Ni_{1 –x}W_x solid solution based on the FCC Ni lattice is also formed. The double carbide Ni₂W₄C_x appears at 660°C, and Ni₆W₆C_x forms at 860°C. Under similar conditions (700°C, He), the thermal decomposition of a mixture of NiWO₄ and LiH leads to the formation of W and an FCC Ni_{1 –x}W_x (x ~ 0.12) solid solution.