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Low temperature synthesis of monolithic transparent Ta2O5 gels from hydrolysis of metal alkoxideTantalum oxide gels in the form of transparent monoliths and powder were prepared from hydrolysis of tantalum pentaethoxide under controlled conditions using different mole ratios of Ta(OC2H5)5:C2H50H:H20:HCl. Alcohol acts as the mutual solvent and HCl as the deflocculating agent. For a fixed alkoxide:water:HCl ratio, time of gel formation increased with the alcohol to alkoxide mole ratio. Thermal evolution of the physical and structural changes in the gel was monitored by differential thermal analysis, thermogravimetric analysis, x-ray diffraction, and infrared spectroscopy. On heating to approximately 400 C, the amorphous gel crystallized into the low temperature orthorhombic phase Beta-Ta2O5, which transformed into the high temperature tetragonal phase Alpha-Ta2O5 when further heated to approximately 1450 C. The volume fraction of the crystalline phase increased with the firing temperature. The Alpha-Ta205 converted back into the low temperature phase, Beta-Ta2O5, on slow cooling through the transformation temperature of 1360 C indicating a slow but reversible transformation.
Document ID
19940006732
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Bansal, Narottam P. (NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1993
Subject Category
Nonmetallic Materials
Report/Patent Number
E-7966
NAS 1.15:106246
NASA-TM-106246
Report Number: E-7966
Report Number: NAS 1.15:106246
Report Number: NASA-TM-106246
Accession Number
94N11204
Funding Number(s)
PROJECT: RTOP 510-01-50
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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