Formation of mixed oxide powders in flames: Part I. TiO sub 2 --SiO sub 2
- Department of Chemical Engineering, The Johns Hopkins University, Baltimore, Maryland 21218 (United States)
Mixed oxide powders, e.g., Al{sub 2}O{sub 3}--TiO{sub 2}, SiO{sub 2}--GeO{sub 2}, and TiO{sub 2}--SiO{sub 2}, are used in industry to produce ceramics, optical fibers, catalysts, and paint opacifiers. The properties of these products depend upon the morphology of the powders. Ceramics and optical fibers are produced using either a uniform mixture of multicomponent particles or a uniform solution. The desired morphology for catalysts is a high surface area and many active sites. TiO{sub 2} coated with a layer of SiO{sub 2} is the desired structure for use as a paint opacifier. In this paper, TiO{sub 2}--SiO{sub 2} mixed oxide powders were synthesized using a counterflow diffusion flame burner. TiCl{sub 4} and SiCl{sub 4} were used as source materials for the formation of oxide particles in hydrogen-oxygen flames. In-situ particle sizes were determined using dynamic light scattering. A thermophoretic sampling method also was used to collect particles directly onto carbon coated grids, and their size, morphology, and crystalline form examined using a transmission electron microscope. A photomultiplier at 90{degree} to the argon ion laser beam was used to measure the light-scattering intensity. The effect of temperature and of Si to Ti concentration ratio on particle morphology was investigated. Strong temperature dependence was observed. At high temperatures, TiO{sub 2} particles were covered with discrete SiO{sub 2} particles. At low temperatures, the structure changes to TiO{sub 2} particles encapsulated by SiO{sub 2}. TEM diffraction pattern measurements showed that the TiO{sub 2} is rutile and the SiO{sub 2} is amorphous silica. At high Si to Ti ratios, SiO{sub 2}-encapsulated TiO{sub 2} particles form. At low Si to Ti ratios, one obtains TiO{sub 2} particles covered with discrete SiO{sub 2} particles.
- DOE Contract Number:
- FG02-88ER45356
- OSTI ID:
- 7266839
- Journal Information:
- Journal of Materials Research; (United States), Journal Name: Journal of Materials Research; (United States) Vol. 7:7; ISSN JMREE; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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Formation of mixed oxide powders in flames: Part II. SiO sub 2 --GeO sub 2 and Al sub 2 O sub 3 --TiO sub 2
Related Subjects
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
CHALCOGENIDES
CHEMICAL COATING
CHEMICAL VAPOR DEPOSITION
DEPOSITION
DISPERSIONS
ELECTRON MICROSCOPY
FLAMES
LIGHT SCATTERING
MICROSCOPY
MIXTURES
MORPHOLOGY
OXIDES
OXYGEN COMPOUNDS
PARTICLE SIZE
POWDERS
QUANTITY RATIO
SCATTERING
SILICON COMPOUNDS
SILICON OXIDES
SIZE
SURFACE COATING
SYNTHESIS
TEMPERATURE DEPENDENCE
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY