Polycrystalline and Monocrystalline Pore Arrays with Large Interpore Distance in Anodic Alumina

Abstract

Silica, titania, and alumina monolithic ceramic chips were prepared via sol‐gel processes. All chips were mesoporous, with average pore sizes of 3.5, 7.7, and for , , and , respectively. Proton conductivity varied linearly with relative humidity in , whereas a steep increase was observed for and between 58 and 81% relative humidity. The variation was linear with temperature for , and exponential for and . At high relative humidity and temperature, conductivities of and were measured for and , respectively. These values are less than one order of magnitude lower than that of Nafion, a polymeric material, and because our membranes can be prepared 100 times thinner than Nafion, they are possible candidates for application as electrolytes in fuel cells. ©1999 The Electrochemical Society