Hafnium carbides and nitrides have received much less attention than their zirconium counterparts due to the higher neutron absorption of hafnium. However, they have shown potential for advanced solar energy-related applications such as partially oxidized hafnium carbide coatings that can increase the spectral selectivity of photovoltaic cells [1] and hafnium nitride as a refractory material for hot carrier solar fuel cell electrodes [2]. In addition, the atomic bonding in hafnium carbonitrides is less strongly influenced by oxygen and nitrogen, making them more suited to non-nuclear applications compared with zirconium carbides.
Despite this, many of the fundamental aspects of hafnium carbides and nitrides remain to be fully understood. For example, despite the high melting temperature of hafnium carbonitride, its phase diagram has not yet been fully mapped experimentally or computationally. In particular, the oxygen solubility of rocksalt-type hafnium carbonitride remains a subject of conflicting experimental results and unresolved theoretical predictions based on various thermodynamic parameters.
A variety of preparation routes have been employed for bulk hafnium carbides and nitrides including reactive spark plasma sintering (RSP) of powder mixtures, direct reaction of metal hydride precursors with graphite or nitrogen, or carbothermal reduction from oxides [3]. These processes suffer from low solid-state diffusion rates that require long processing times to obtain single-phase samples.
Moreover, it is difficult to determine lattice parameter compositions for non-stoichiometric hafnium carbonitrides by conventional methods because of the high atomic number and bridging oxygen content of these compounds. The present invention aims to develop a new method for the preparation of multilayer tungsten mesh toughened hafnium carbonitride-based cermet with excellent thermal shock and ablation resistance. To do so, the invention firstly prepares mixed powder by ball milling a hafnium carbide and nitride powder with the ratio of ball-to-material of 3-10: 1; then, the mixed powder is uniformly and alternately placed into a graphite die to form six layers of tungsten nets; followed by sintering at 1900°C for 20 minutes under 40 MPa pressure to obtain the sintered body of multilayer tungsten mesh toughened carbon-nitride-hafnium ceramics.