High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report No. 7, March 1, 1993--June 1, 1993
Corrosion kinetics of SiC were investigated from 950 to 1100C at 0.63 vol% alkali vapor concentration. Corrosion rate in alkali is 10{sup 4} to 10{sup 5} times faster than oxidation rate of SiC in air. Activation energy of the alkali corrosion is 406 kj/mol, indicating a high sensitivity to temperature changes. Overall reaction appears to be controlled by the oxidation of SiC. The alkali corrosion kinetics of Si{sub 3}N{sub 4} from 950 to 1050{degrees}C were also examined in the same atmosphere (0.63 vol% alkali vapors). Reaction thickness of Si{sub 3}N{sub 4} appears to vary linearly with reaction time from 950 to 1050C, suggesting that the alkali corrosion process is controlled by the oxidation of Si{sub 3}N{sub 4}. At 1050{degrees}C, the alkali-enhanced oxidation of Si{sub 3}N{sub 4} is approximately 10{sup 7} times faster than the oxidation of Si{sub 3}N{sub 4} in dry oxygen. Compared to SiC corroded in the same alkali atmosphere, Si{sub 3}N{sub 4} seems to be less alkali-resistant than SiC. Phase relations of the Na{sub 2}O-Al{sub 2}TiO{sub 5} vertical section from 5--40 wt% Na{sub 2}O and 840-1100C were studied. Phase analysis indicates that this section is not a true binary system. A tentative phase diagram for the Na{sub 2}O-Al{sub 2}O{sub 3}-TiO{sub 2} system was constructed.
- Research Organization:
- Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Center for Advanced Ceramic Materials
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-91PC91309
- OSTI ID:
- 10171441
- Report Number(s):
- DOE/PC/91309-T8; ON: DE93018889
- Resource Relation:
- Other Information: PBD: 25 May 1993
- Country of Publication:
- United States
- Language:
- English
Similar Records
High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report No. 6, December 1, 1992--February 28, 1993
High temperature alkali corrosion of ceramics in coal gas