GB960720A - Refractory metal compounds - Google Patents

Abstract

A refractory compound having an hydrogen dissociation pressure comprises a metal, a non-metal comprising nitrogen, oxygen, or carbon, and hydrogen in an amount not less than 0.25 atoms of hydrogen per atom of metal, the non-metal being combined with the metal to form a crystal lattice, and the hydrogen being chemically bound in the lattice and being displaceable as free hydrogen without disrupting the lattice. The metal is preferably zirconium, titanium, or a rare earth metal, including yttrium; these metals may be present together with calcium, or with lithium or plutonium in an amount up to 20% of the total metal ions. The compounds may be prepared by heating a metal hydride with a refractory metal oxide, carbide, or nitride in the presence of hydrogen to form a single phase product; reaction normally takes place at above 1000 DEG C. but in the case of lithium compounds may be as low as 500 DEG C. Compounds containing sulphur, carbon, or nitrogen in addition to oxygen are prepared by heating a metal hydride with a refractory metal oxide and a metal sulphide, carbide, or nitride in the presence of hydrogen. Metal compounds (e.g. lithium hydroxide) which produce the desired oxide &c. at reaction temperature may be used. In examples (1)-(3) cerium oxide and cerium hydride are heated in hydrogen at 1250 DEG C. to form CeO0.75H1.5; (4) zirconium nitride is heated with zirconium metal powder at 1500 DEG C. in hydrogen to form ZrN 1/3 H1.2; (5) a mixture of zirconium metal powder and graphite is heated in hydrogen to 1600 DEG C. forming ZrC 2/3 H\ba1/4 ; (6) a mixture of cerium hydride, cerium monosulphide, and cerium oxide is heated in hydrogen to 1200 DEG C. forming Ce2OSH2; (7) lithium hydroxide, lithium hydride, and zirconium metal powder are heated in hydrogen to 700 DEG C. to form LiZr0,2O0.5H 2/3 ; (8) calcium hydride and zirconium oxide are heated in hydrogen at 1500 DEG C. yielding CaZrO2H1,0; (9) zirconium oxide, zirconium metal, and graphite are heated in hydrogen at 1600 DEG C. yielding ZrO0.6C0.2H0.8; (10) a mixture of alumina and cerium hydride heated in hydrogen at 1250 DEG C. yields cerium aluminium hydro-oxide; (11) a mixture of zirconium disulphide, zirconium oxide, and zirconium metal is heated in hydrogen at 1300 DEG C. forming Zr2OSH; (12) a mixture of cerium sulphide, cerium hydride, and lithium hydroxide heated at 1250 DEG C. in hydrogen forms cerium lithium hydro-oxysulphide; (13) lithium hydroxide and titanium anhydride heated at 900 DEG C. in hydrogen form lithium titanium hydro-oxide; (14) titanium dioxide and titanium dihydride heated to 1200 DEG C. in hydrogen from titanium hydro-oxide. The materials formed are useful as solid moderators in high temperature nuclear reactors; their neutronic properties may be altered by adding a small quantity of uranium or by isotopic replacement of hydrogen. The third Provisional Specification refers to the preparation of ceramic materials containing beryllium or uranium.