Preparation and properties of composite hydrogen permeation barrier on ZrH1.8 by sol-gel technique

A composite hydrogen permeation barrier has been prepared on zirconium hydride (ZrH1.8) by sol-gel coating and subsequent heat treatment under an oxidizing atmosphere. Phosphoric acid modified silica sol-gel coating was fabricated on the surface of ZrH1.8 substrate by sol-gel dip-coating technique. Scanning electron microscopy (SEM) analysis showed that the sol-gel coating fabricated on ZrH1.8 substrate was free of cracks after sintering at 600 °C. The sol-gel coating could retard the oxidation of the ZrH1.8 substrate. This allowed a defect-free oxide transition layer formed between the ZrH1.8 substrate and the sol-gel coating. The thickness of the oxide transition layer was related to the temperature of the heat treatment for the coated ZrH1.8. X-ray diffraction (XRD) analysis showed that the major phase of the oxide layer in this work was similar to the oxide layer prepared by in-situ oxidation method. It was inferred that the oxide transition layer combined with the sol-gel coating comprises a composite hydrogen permeation barrier according to the X-ray photoelectron spectroscopy (XPS) analysis. In the vacuum system at 600 °C, the performance of the composite hydrogen permeation barrier was better than that of the in-situ oxide layer. Average hydrogen outgassing rate (J) and outgassing reduction factor (D) of ZrH1.8 with in-situ zirconia layer could be enhanced to 1.74 × 10−5 mol·m−2·s−1 and 2.08, respectively. By contrast, J and D value of ZrH1.8 with composite hydrogen permeation barrier could be enhanced to 1.22 × 10−6 mol·m−2·s−1 and 29.70, respectively.