Study On The Phases Of Zirconium Hydride And The Position Of Hydrogen Isotope Atoms

Zirconium is candidate material for hydrogen isotope gases storage with lower equilibrium pressure,it also can be used as functional materials in nuclear reactor for its excellent nuclear quality,but there is isotopic effect in zirconium-hydrogen system.Moreover,because of superior biocompatibility property,corrosion resistant property at high temperature and so on,zirconium films prepared by physical vapor deposition are used as corrosion resistant coating,fisrt mirror reflectivity device in fusion reactor,furthermore,zirconium tritide films,which deposited on molybdenum,copper or stainless steel substrate,are used in nuclear technology application.It is important to research phase composition and structure of zirconium hydride and deuteride in zirconium-hydrogen system for zirconium application in tritium process and nuclear technology.When zirconium films are used as functional material,film structure is closely related with depositon condition,different film structure will lead to property difference.Therefore,investigating the effect of depositon process and substrate orientation to film structure,it is important to zirconium film preparation by physical vapor deposition and application.Phase compositon of zirconium hydrides(deuterides)with different hydrogen isotope content were investigated systematic by X-ray and high resolution neutron diffraction,the relationship was established between crystal and phase structure and hydrogen isotope content,moreover,the lattice parameters of zirconium hydride(deuterides)and the occupation of hydrogen isotope atoms in lattice were obtained.Zirconium film deposition process was simulated,the effect of substrate orientation to film structure was also investigated.After zirconium films deuterated and tritiated,their structures were analyzed by XRD.Ziconium hydrides(deuterides)were prepared between the 0-2.0 H(D)/Zr atom ratio range,phase transformation occurred with hydrogen(deuterium)content increasing,the whole phase transformation process was as below:a phase(hcp structure)?? phase(hcp structure)+? phase(fct structure)+? phase(fcc structure)?? phase(fcc structure)?? phase(fct structure).Among the several phase structure in zirconium hydrides(deuterides),y phase of fct structure was steady at room teperature,but it exist with ? and ? phase,not alone while hydrogen(deuterium)content was lower.a phase of hcp structure in zirconium hydride(deuteride)was a mixture of zirconium hydrogen(deuterium)solid solution and non-stoichiometric zirconium oxide.Due to the non-stoichiometric zirconium oxide in zirconium hydride(deuteride),the H(D)/Zr atom ratio when ? to ? phase transformation went to lower,but after fitted the high resolution neutron diffraction data,the actual H(D)/Zr atom ratio was between 1.50 to 1.70 when ? to ? phase transformation occurred in zirconium hydride(deuteride).Hydrogen isotope atom occupations were obtained by fitting the high resolution neutron diffraction data in the lattice of ?,?,? and ? phase.In a phase zirconium deuteride solid solution of hcp structure.zirconium atoms formed hexagonal close-packed structure,deuterium atoms occupied tetrahedral interstice.In ? phase zirconium deuteride of fcc structure,deuterium atoms occupied tetrahedral interstice with coordinate(0.25,0.25,0.25).In y phase zirconium deuteride of fct structure,deuterium atoms occupied 2a site with coordinate(0.25,0.25,0.25)and 2b site with coordinate(0.25,0.25,0.75)in tetragonal lattice.While in ? phase zirconium deuteride of fct structure,deuterium atoms occupied 4d site with coordinate(0,0.5,0.25)in tetragonal lattice.Deuterium displaced ? phase of fcc structure and ? phase of fct structure zirconium hydrogen deuterides were prepared by different hydrogen isotope gases absorption order(hydrogen absorbed firstly,deuterium absorbed firstly or HD absorbed directly).The lattice parameters were almost the same in zirconium hydride,deuteride and hydrogen deuteride with the same total H/Zr atom ratio,but due to the displacement of hydrogen atoms by deuterium atoms,the lattice parameters of zirconium hydrogen deuterides was larger than that of zirconium deuteride,while the lattice parameters of zirconium hydride was the largest.Zirconium film deposition process was simulated by phase field theory.It was indicated that deposite rate was closely related to zirconium film density.The columnar crystal growth parallelled to deposition direction competed with that of perpendiculared to deposition direction.When the depositon rate was lower,the columnar crystal growth perpendiculared to deposition direction was dominant.spaces between columnar crystals were esy to filled,and zirconium film with dense structure was formed,also the orientation of columnar crystal tended to consistent.The growth rate of columnar crystals parallelled to deposition direction increased with deposition rate increasing,the columnar crystal amount exhibited an increasing tendency,and more voids were formed in the deposited area.When the deposite rate was 5nm/s,10nm/s and 20nm/s respectively,the growth rate of columnar crystal parallel and perpendicular to deposition direction was equivalent.When deposite rate was 40nm/s,the columnar crystal growth parallelled to deposition direction was dominant,the amount of columnar crystal increased,and their growth rate was close,the void between columnar crystals was homogeneous.Zirconium film growed with obviously preffered orientation when deposited on preffered orientation substrate.Zirconium films were single crystal with different preferred orientation when deposited on single crystal molybdenum substrate,moreover,zirconium films were a phase of hcp structure and ? phase of bcc structure,and it was almost a big grain.Zirconium films were polycrystal when they deposited on polycrystal molybdenum substrate.After deuterated and tritiated,zirconium deuteride and tritide films were ? phase of fct structure when D(T)/Zr>1.60.