Hydrogen reduction behavior of W/Y2O3 powder synthesized by ultrasonic spray pyrolysis

Abstract

In this study, hydrogen reduction behavior of W/Y2O3 powder was investigated. Phase transformation of WO3/Y2O3 powder was observed during the hydrogen reduction process in the temperature range of 400–800 °C for up to 5 h. The reduction behavior was investigated by the morphology images and the x-ray diffraction (XRD) patterns of the reduced powders at each step. The reduction of WO3/Y2O3 powder was started from the outer region of powder, and the crack was occurred at outer region due to the transformation, which was able to be explained by crackling core model. The particle size of W/Y2O3 decreased due to the addition of Y2O3 particle compared to that of W powder. The activation energy of WO3/Y2O3 powder was calculated via temperature programmed reduction (TPR) analysis, and WO3/Y2O3 and WO3 powder had a difference in activation energy calculated from first peaks in TPR analysis. The addition of Y2O3 particle affected the reduction behavior, especially reduction of WO3 phase to WOx (2 ≤ x < 3) phases.