Hardening of sol-gel derived hafnia films by photo-irradiation

Abstract

Sol-gel derived hafnia films were hardened by ultra-violet irradiation with a high-pressure mercury lamp. The hafnia sol A was prepared by the hydrolysis of HfCl₄ in ethanol with H₂O and HNO₃, and the sol B was prepared by the hydrolysis of hafnium hydroxide with H₂O and HCOOH. The gel film obtained from the sol A was hardened to 9H by the pencil method of the scratch hardness after the UV-irradiation of 30 min. The irradiation time, however, was shortened to 10 min in the case of the film obtained from the sol B.