A crack- and pinhole-free composite membrane consisting of an α-alumina support and a modified γ-alumina top layer which is thermally stable up to 1100°C was prepared by the sol–gel method. The supported thermally stable top layer was made by dipcoating the support with a boehmite sol doped with lanthanum nitrate. The temperature effects on the microstructure of the (supported and unsupported) La-doped top layers were compared with those of a common γ-alumina membrane (without doping with lanthanum), using the gas permeability and nitrogen adsorption porosimetry data. After sintering at 1100°C for 30 h, the average pore diameter of the La-doped alumina top layer was 17 nm, compared to 109 nm for the common alumina top layer. Addition of poly(vinyl alcohol) to the colloid boehmite precursor solution prevented formation of defects in the γ-alumina top layer. After sintering at temperatures higher than 900°C, the common alumina top layer with addition of poly(vinyl alcohol) exhibits a bimodal pore distribution. The La-doped alumina top layer (also with addition of poly(vinyl alcohol)) retains a monopore distribution after sintering at 1200°C.
[1]
A. Burggraaf,et al.
Ceramic nanostructure materials, membranes and composite layers
,
1989
.
[2]
J. Fabre,et al.
New Inorganic Ultrafiltration Membranes: Titania and Zirconia Membranes
,
1989
.
[3]
J. Fabre,et al.
Inorganic membranes obtained by sol-gel techniques
,
1988
.
[4]
A. Burggraaf,et al.
Gas separation mechanisms in microporous modified γ-al2o3 membranes
,
1988
.
[5]
J. Fabre,et al.
Microporous Layers from Sol-Gel Techniques
,
1986
.
[6]
A. Burggraaf,et al.
The preparation and characterization of alumina membranes with ultra-fine pores
,
1984
.
[7]
A. Youssef,et al.
Studies on the mixed oxide catalyst Al2O3-Cr2O3 I. Surface properties
,
1979
.
[8]
R. M. Levy,et al.
The effect of foreign ions on the stability of activated alumina
,
1967
.
[9]
K. A. Krieger,et al.
The Surface Area and Catalytic Activity of Aluminum Oxide
,
1949
.