Electrochemical synthesis of hafnium carbide powder in molten chloride bath and its densification

Authors: Abdelkader, A.M. and Fray, D.J.

Journal: Journal of the European Ceramic Society

Volume: 32

Issue: 16

Pages: 4481-4487

ISSN: 0955-2219

DOI: 10.1016/j.jeurceramsoc.2012.07.010

Abstract:

Nanocrystalline powder of hafnium-rich-HfC has been successfully synthesised by the electro-deoxidation of HfO 2-carbon precursors in molten chloride. The progress of the solid state reduction was monitored ex situ by analysing partially reduced samples using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It has been shown that the reduction started by converting HfO 2 to CaHfO 3 and an oxycarbide phase of the form HfC xO 2(1-x). The CaHfO 3 phase then also reduced to give HfC xO 2(1-x), which subsequently reduced to HfC by ionising oxygen. The morphological analysis indicated almost no growth in the grain size occurred during the course of the electro-deoxidation. This investigation showed some loss of carbon during the electro-deoxidation resulted in metallic rich HfC. The synthesised powder exhibited better sinterability than the commercial HfC powder. Using the synthesised powder, fully dense monolithic HfC ceramics were produced by pressureless sintering at 1973K with average grain size of about 3μm. © 2012 Elsevier Ltd.

Source: Scopus