Effect of water vapor partial pressure on the structure of blue tungsten reduction products in hydrogen

This study investigates the structural evolution of blue tungsten reduction products when exposed to hydrogen under controlled water vapor partial pressures. The reduction of WO₂.₉ was achieved through hydrogen atom diffusion at 1050 °C. The Results indicate that, at low water vapor partial pressure, the reduction process of blue tungsten initiates on the surface and progresses inward, creating surface cracks on the clusters. These cracks enable water vapor to interact with the reduced tungsten (W) at their base, leading to the formation of needle-like WO₂.₇₂ phases that grow outward. Under high water vapor partial pressure, the morphology of the acicular WO 2.72 phase changes to a stacked structure. Additionally, W-OH bonds were identified in the reduction products, with the WO₂.₇₂ growth angles observed at approximately 12° relative to the tungsten particles, closely matching the interfacial model prediction of 13.41°. The results of this paper will provide theoretical support for the structural evolution of intermediate products during hydrogen reduction of blue tungsten.