Boron-Based Ceramics and Composites for Nuclear and Space Applications: Synthesis and Consolidation: Handbook of Advanced Ceramics and Composites

Boron is one of the few elements to possess nuclear properties, which warrant its consideration as neutron absorber material due to its high neutron absorption cross section of 3838 barns (for thermal neutrons, 0.025 ev) for 10B isotope. Boron-based ceramics are used as a control/shutoff rod, neutron shielding for the nuclear reactor as well as spent fuel storage bays, neutron sensors for measuring the neutron flux in a nuclear reactor, and space applications. Refractory and rare earth metal borides possess superior thermophysical properties, which enables to use for high-temperature structural/functional applications. These borides are potential for high-temperature nuclear reactors of Generation IV as neutron absorbers, second-generation solar (receiver materials of concentrated solar power), and space applications such as rocket and hypersonic vehicle components, nozzles, leading edges, and engine components [81, 97, 109, 115]. Refractory metal borides are suitable for space application due to attractive combination of properties such as high melting point (>3000 °C), thermal conductivity, low thermal expansion coefficient, retention of strength at high temperatures, good thermal shock, oxidation, and erosion resistance [61, 81, 105, 118]. Various boron-based ceramics such as B4C, TiB2, ZrB2, HfB2, NbB2, CrB2, LaB6, CeB6, NdB6, SmB6, YbB6, PrB6, GdB4, and EuB6 and its composites were synthesized and consolidated by various methods which are cited in the literature. This chapter reviews the work carried out on synthesis, consolidation, properties, and applications of important transition/refractory/rare earth metal borides.