Photoelectrochemical characteristics of AB_5-type hydrogen storage alloy modified with SrTiO_3 photocatalyst

Perovskite-type SrTiO3 powders were prepared by using strontium acetate, tetrabutyl titanate and sodium hydroxide via direct hydrolysis-precipitation process. AB5-type hydrogen storage alloy（HSA） electrodes modified with SrTiO3 powders were prepared and the photoelectrochemical characteristics of the as-prepared electrodes were investigated. The results of cyclic voltammograph show that the current of reduction peak increases remarkably under the light irradiation. The obvious photochargeable properties are obtained for the hydrogen storage alloys modified with Perovskite-type SrTiO3 powders. During photocharging process, the potential of the electrode shifts quickly to negative direction and a potential plateau occurs. HSA electrode modified with SrTiO3 powders prepared by direct hydrolysis-precipitation process gives the higher potential of about -0.90V（vs Hg/HgO） under the light irradiation. SEM observation discloses that a large amount of microcracks occur on the surface of the electrode after photocharging process, which is caused by the formation of hydride in the bulk of electrode.

Bridgman growth of LiYF_4 single crystal in nonvacuum atmosphere

Using LiF and YF3 as starting materials,we prepare feed material from fluorides according to the molar ratio of LiF：YF3=51.5：48.5.The anhydrous LiYF4 polycrystalline material is synthesized via the fluoridation process with a dried HF flow at elevated temperature.By charging the feed material and adding a small amount of active carbon powder in a sealed platinum crucible,the crystal can be grown via the vertical Bridgman method in a nonvacuum atmosphere.This is possible because the oxidization and volatilization of the melt is avoided.Using optimum conditions,that is,a growth rate of 0.5-0.6 mm/h and a temperature gradient of 25-30℃/cm across the solid-liquid interface under a furnace temperature of 920-930℃,the colorless crystal LiYF 4 with the size of φ25 × 50 （mm） is successfully grown.The optical transmittance of the crystal is as high as 85% above the absorption edge at 190 nm.The induced absorption bands are observed below 700 nm in the transmission spectrum after the crystal is subjected to a high dose of γ-ray irradiation.