ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The thermal stability of unsupported alumina membrane top-layers was studied by determining the pore structure (mainly pore size) change of alumina gels, prepared by sol-gel methods, after sintering at different temperatures ranging from 450 to 1200 °C. The average pore size of the pure alumina membranes and PVA-added membranes increased sharply after sintering at temperatures higher than 1000 °C. Addition of 3% lanthanum, either by mixing lanthanum nitrate in the alumina sol or impregnating lanthanum nitrate into calcined alumina gel, followed by a second heat treatment, can considerably stabilize the pore structure of the alumina membrane top-layers. The pore diameter for the lanthanum-doped membranes was stabilized within 25 nm after sintering at 1200 °C for 30 h, about one-sixth of that for the pure alumina membranes after sintering at 1200 °C for 30 h. The substantial increase in the pore size for the pure alumina membranes at the sintering temperature of 1000 to 1200 °C was accompanied by the phase transformation from γ-to α-alumina. The addition of lanthanum can raise this phase transformation temperature by about 200 °C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00588309
Permalink
