Preparation of Tubular Silica‐Glass Membranes with Thin Silica Layers by Sputtering, Using the Novel Sputtering Apparatus for Tubular Supports

Abstract

Tubular SiO2‐glass membranes with thin, dense SiO2layers on porous glass supports were prepared via sputtering, using the novel sputtering apparatus for tubular supports. This apparatus had a holder for tubular supports and a rotation mechanism. The sputtering conditions of the membranes were investigated. A support temperature of 573 K was determined to be the best among the temperatures that were selected in our experiments. Scanning electron microscopy observations showed that the membrane surfaces became smooth as the sputtering time increased and had no cracks. The permeances of helium, nitrogen, and CO2were measured at a temperature of 373 K. The permeances for the membranes were on the order of 10‐9 molm‐2s‐1Pa‐1 (10‐5 cm3(STP)cm‐2s‐1(cm Hg)‐1). The ratio of the permeances of helium to nitrogen was similar to the theoretical Knudsen value. These values were much lower than the values that were expected from the dense SiO2glass. This phenomenon was considered to be attributable to the presence of microcracks during the sputtering deposition.