Thermal stabilization of anatase (TiO[sub 2]) membranes

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7017619

Bischoff, B L

Applications involving separation of gasses at high temperature require fabricating membranes having both the desired pore size and also a high thermal stability. Titanium dioxide membranes contain mesopores only when fired to temperatures below 500[degrees]C. The loss of pore structure at higher temperatures coincides with the transformation of anatase to rutile. In the preparation of anatase membranes by sol-gel processing, the effect of peptization conditions on the properties of the TiO[sub 2] gel were examined. It was found that fast hydrolysis of titanium ethoxide leads to a supersaturation of hydroxylated titanium and amorphous TiO[sub 2]. Room temperature peptization with nitric acid yields a gel comprised of a mixture of anatase and rutile, while peptization over 80[degrees] yields an anatase gel. Gels comprised of small anatase were obtained after only 15 minutes of peptization with continued peptization resulting in a growth of the anatase. Anatase gels also resulted from peptization with hydrochloric acid and a low concentration of sulfuric acid. Vanadium was added to TiO[sub 2] in order to inhibit the transformation to rutile. Vanadium added as an alkoxide to the titanium alkoxide precursor inhibits the transformation to rutile and resulting membranes are still mesoporous when heated to 600[degrees]C. It was found that doping of as little as 1% vanadium gave the maximum increase in thermal stabilization. Titanium dioxide membranes were doped with transition metal cations order to investigate if a relationship exists between the valence state of the cation and its ability to inhibit transformation of anatase to rutile. All of the cations in this study were found to inhibit the transformation to rutile. However, only yttrium, tungsten and vanadium slowed the coarsening of the anatase enough to significantly stabilize the pore size of the membrane. Membranes doped with as little as 2% yttrium or tungsten are still mesoporous after firing to 700[degrees]C.

• Research Organization: Wisconsin Univ., Madison, WI (United States)
• OSTI ID: 7017619
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360601* -- Other Materials-- Preparation & Manufacture
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALLOYS
CHALCOGENIDES
CHEMICAL PREPARATION
DOPED MATERIALS
MATERIALS
MEMBRANES
MICROSTRUCTURE
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PORE STRUCTURE
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RUTILE
SOL-GEL PROCESS
STABILIZATION
SYNTHESIS
TEMPERATURE DEPENDENCE
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VANADIUM ADDITIONS
VANADIUM ALLOYS