Properties Research Of Zr-Al Oxide Coatings On The Surface Of Zirconium Hydride Prepared By Sol-Gel

Zirconium hydride is the preferred moderator materials in nuclear reactors due to its high hydrogen density,low neutron capture cross-section and negative temperature coefficient.However,zirconium hydride has a tendency to lose hydrogen at high working temperature,which leads to reduce to moderate efficiency and service life of zirconium hydride.In order to ensure normal work of the moderator,an effective way to prevent hydrogen loss which has attracted much attention is to prepare hydrogen permeation barrier on the surface of the zirconium hydride.Thus,anti-hydrogen permeation barrier coatings are prepared on the surface of ZrH_1.8 to reduce hydrogen loss without affecting moderating ability of zirconium hydride by modification technology.The development of excellent hydrogen barrier coating is of great importance for the successful application of zirconium hydride and the structural design of space nuclear reactor.Zr-Al oxide coatings prepared by inorganic zirconium salt and isopropanol aluminum precursor were fabricated on the surface of zirconium hydride by sol-gel technique.The influence of Al₂O₃/ZrO₂ molar ratio,inorganic zirconium salt precursor and precursor concentration was studied on Zr-Al composite oxide coatings properties.Thickness,morphologies and phase structure of the composite oxide coatings were characterized by field emission scanning election microscopy?FE-SEM?,confocal laser scanning microscope?CLSM?and X-ray diffraction?XRD?,respectively.Vacuum dehydrogenation experiment was employed to test the anti-permeation effects of the composite oxide coatings.The main conclusions of the research are as followed:Binding force between Zr-Al oxide coatings and zirconium hydride varies from 35.69N to 49.55 N,thickness of the coatings varies from 6.5?m to 19.2?m and permeation reduction factor?PRF?varies from 6.7 to 15.9,which all increase first and then decline with decreasing Al₂O₃/ZrO₂ molar ratio.The molar ratio of Al₂O₃/ZrO₂ is 1:1¹:3,and the composite gels exist in an amorphous structure.When the molar ratio of Al₂O₃/ZrO₂ is 1:4and 1:5,the composite gels transform from amorphous zirconia to C-ZrO₂.The maximum binding force is 49.55 N,the maximum thickness is 19.2?m and the maximum PRF is15.9 when molar ratio of Al₂O₃/ZrO₂ is 1:4,which is more compact,continuous and uniform than others.Zr-Al oxide coatings were prepared by zirconium oxychloride,zirconyl nitrate and zirconium nitrate as inorganic zirconium salt precursors and aluminum isopropoxide as aluminum source when the molar ratio of Al₂O₃/ZrO₂ is 1:4.The results show that the stability of the composite sol with zirconium nitrate as the precursor is poor,and it is difficult to form continuous and complete composite coating on the surface of zirconium hydride.Composite oxide coatings with zirconyl nitrate as precursor have poor compactness.The composite sol obtained zirconium oxychloride as precursor is stable,the composite oxide coating is more smooth,continuous and compact on the surface of zirconium hydride.Binding force between coatings and substrate and PRF value with zirconium oxychloride as precursor are significantly higher than those composite coatings with zirconium nitrate and zirconyl nitrate as precursors.Different inorganic zirconium salts have no significant effect on the phase structure of composite gels.The composite gels transform from amorphous zirconia to C-ZrO₂.When aluminum isopropoxide concentration is in the range of 0.2⁰.8 mol/L,thickness of the coatings varies from 5.6?m to 19.2?m and permeation reduction factor?PRF?varies from 4.1 to 15.9,which PRF values increase first and then decline with increasing precursor concentration.The composite gels transform from amorphous zirconia to C-ZrO₂.The continuous composite oxide coatings couldn't be formed when concentration is below 0.2 mol/L.Denseness coatings is poor when the precursor concentration is above 0.6 mol/L.The maximum thickness is 19.2?m and the maximum PRF is 15.9 when concentration is 0.4 mol/L,which is more compact,continuous and uniform than others.