Electrochemical synthesis of hafnium carbide powder in molten chloride bath and its densification |
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| Authors: | Amr M. Abdelkader Derek J. Fray |
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| Affiliation: | 1. School of Materials, University of Manchester, Grosvenor Street, Manchester M1 7HS, UK;2. Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK;1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China;2. School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an 710072, China;1. College of Chemical Engineering, Hebei United University, Tangshan, Hebei 063009, PR China;2. Hebei Province Key Laboratory of Inorganic and Non-Metal Materials, Tangshan, Hebei 063009, PR China |
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| Abstract: | Nanocrystalline powder of hafnium-rich-HfC has been successfully synthesised by the electro-deoxidation of HfO2–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 HfO2 to CaHfO3 and an oxycarbide phase of the form HfCxO2(1?x). The CaHfO3 phase then also reduced to give HfCxO2(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 1973 K with average grain size of about 3 μm. |
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