Neutron diffraction study of concentration phases transition in the TiC0.50Hy alloy

Abstract

The study belongs to the field of hydrogen materials science. A neutron diffraction study of titanium carbohydride TiC0.50Hy was carried out in the range of hydrogen concentration у = 0.50 ÷ 0.60. It is shown that high-temperature titanium carbohydride TiC0·50H0.50 of equiatomic composition has a face-centered cubic lattice (sp. gr. Fm3¯m), where hydrogen atoms are located in tetrahedral interstices. It has been established that in this alloy in vacuum, the phenomenon of hydrogen thermal emission is observed - complete removal of hydrogen with preservation of the FCC lattice of the TiС0.50 interstitial alloy. For the first time in the Ti–C–H system, a first-order concentration phase transition FCC (sp. gr. Fm3¯m) → HCP (sp. gr. Pm3¯1) in TiC0.50Hy carbohydride at a hydrogen concentration y > 0.50 was discovered without changing the octahedral environment of carbon atoms and tetrahedral the surroundings of hydrogen atoms by Ti atoms. The HCP phase in vacuum is heat-resistant at temperatures T < 600 K. The unit cell volume of the hcp phase is two times smaller than the unit cell volume of the FCC phases TiC0.50Hy and TiH2 of equiatomic composition. The results of studying the fcc phase of the equiatomic composition of TiC0·50H0.50 can be used to prepare a high-temperature hydrogen reservoir in hydrogen energy. The HCP phase can be used as a biological protective material in transport nuclear power plants and on nuclear submarines instead of titanium dihydride TiH2.