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2001 | PATENTS
| INTERNET
| Cui
X. X., Zhang N., Kanno A., Morozumi S. Mechanical
Properties of Silicon Carbide Joints Bonded with Titanium Foil
// Nippon Kinzoku Gakkaishi - 1992. - 56(12). - 1463-1469. (Japanese). Pressureless-sintered SiC joints, bonded at various temps. with thin Ti foils were examd. for bend strength at room and high temps., thermal shock resistance, oxidn. resistance of interfacial reaction layer, and microstructure by optical microscopy and SEM with electron probe microanal. The optimum joining temp. range is 1773-1873 K. The bend strength at room temp. is maintained to .apprx.1473 K. The thermal shock resistance of the interfacial reaction layer is higher than that of the bulk SiC. The interfacial reaction layer is Ti3SiC2 which is (Si, Ti)O2 at the exposed surface when the joint is kept at high temps. in ambient oxidizing atm. This oxidn., however, results in strengthening of the layer by exposure at .apprx.1473 K and then in deterioration of the layer at >1673 K where the oxidn. of the layer proceeds rapidly. |
| Gadalla
A., Elmasry M., Kongkachuichay P. High Temperature
Reactions within SiC - Al2O3
Composites
// J. Mater. Res. - 1992. - 7(9). - 2585-2592. Composites of SiC-Al2O3 and SiC-mullite are unstable at high temperatures. The reactions occurring within the composites between 1700 and 1850 °C in stagnant inert atmospheres were characterized. Gaseous products cause excessive weight losses which cannot be attributed to passive oxidation. These losses can be successfully retarded by processing under high pressures. Compatible phases were determined by X-ray analysis for mixtures lying in the section SiC-Al4C3-Al2O3-SiO2. The reactions produced condensed phases of Al2OC and Al4O4C as well as gaseous SiO and CO. The condensed phases have high vapor pressures above 1700 °C. The effect of these reactions on densification of composites by firing at different temperatures for various periods under different pressures was studied. Dence materials prepared under high pressures at 1825 °C were tested at 1700 °C under normal pressure in argon, where active oxidation is expected, and weight losses were insignificant. |
| Hall
I. W., Lirn J. L., Lepetitcorps Y., Bilba K. Microstructural
Analysis of Isothermally Exposed Titanium / Silicon Carbide
// J. Mater. Sci. - 1992. - 27(14). - 3835-3842. [no abstract] |
| Lis J., Pampuch R., Stobierski L. Reactions during
SHS in a Ti-Si-C System // Int. J. Self-Propag. High-Temp.
Synth. - 1992. - 1(3). - 401-408. The reactions and phase transitions in a Ti-Si-C system under self-propagating high-temp. synthesis (SHS) conditions were elucidated. The exptl. detd. phase compn. of SHS solid products was compared with that predicted to occur at equil. The adiabatic temp. for the initial chem. compn. of the reactants was calcd. This temp. served as a qual. measure of the actual temp. and thus of the probability of liq. phase formation. The SHS phase compn. from reactive mixts. of various compn. can be explained by (i) formation of large amts. of liq. phase with chem. compn. similar to that of the initial mixts. for samples with a high (2900-3050 K) adiabatic temp. and (ii) depletion of Ti and C in the liq. phase which forms in the late stages of SHS due to the TiC solid-state reaction in the early stages of SHS for samples with moderate (1980-2250 K) adiabatic temps. |
| Oscroft
R. J., Thompson D. P. Influence of Oxygen on
the Formation of Aluminum Silicon Carbide // J. Am. Ceram.
Soc. - 1992. - 75(1). - 224-226. X-ray diffraction studies have been used to follow the formation of Al4SiC4 from Al4C3 and SiC and the role played by impurity oxigen. The phase Al2OC forms in the early stages of reaction and reacts with SiC at ~1700 °C to produce Al4SiC4 plus a small amount of an aluminosilicate liquid. This liquid dissociates at higher temperatures, the resulting evolution of masses hindering complete densification. Higher densities are obtained on hot-pressing. |
| Oscroft
R. J., Thompson D. P. High-Temperature Reactions
in the Boron-Aluminum-Silicon-Nitrogen-Carbon System / Int.
Symp. Ceram. Mater. Compon. Engines, 4th. - Elsevier: London, 1992.
- 172-179. The incorporation of nitrogen into boron carbide was investigated. At temperatures in the range 800-1100 °C , the soly. is ~3.8%. At these and higher temps., there is a competing reaction whereby the B4C structure is broken down and an amorphous B-N-C product is formed. This resists crystn. even at temperatures as high as 1500 °C. Oxygen is always present as a surface layer on carbide and nitride powders used in high-temperature reactions. Its role in the densification of nitrogen ceramics is well known; the present work describes its role in the formation and densification of Al4SiC4 ceramics. |
| Sambasivan S., Petuskey W. T. Phase Relationship in the
Ti-Si-C System at high Pressures // J. Mater. Res. - 1992.
- 7(6). - 1473-1479. The compatibility of phases in the Ti–Si–C system was studied for pressures from 10 to 20 kbars (1 to 2 GPa) and temperatures from 1200 °C to 1500 °C via an interfacial reaction between titanium and silicon carbide. The interface was characterized by backscattered electron imaging and electron probe microanalysis. Ti3Si was stabilized at high pressures exhibiting an appreciable solubility for carbon (up to 9 at. %). At higher temperatures and lower pressures, it decomposed to Ti5Si3, Ti(Si,C), and TiCx according to the relation Ti3Si(Cz) = (0.70588)TiCx + (0.32437)Ti5Si3 + (0.67227)Ti(Si,C), where the mathematical coefficients were calculated using z = 0.4 and x = 0.5. No detectable quantities of carbon dissolved in Ti5Si3 under these conditions. A clapeyron slope of 0.08 ( 60.01) kbar/K was measured for this reaction. The microstructure of the reaction zone and other general thermodynamic and kinetic characteristics are discussed for different experimental conditions. |
| Yano
T., Kato S., Iseki T. High-Resolution Electron
Microscopy of the Silicon Carbide / Aluminum Carbide Interface
// J. Am. Ceram. Soc. - 1992. - 75(3). - 580 - 586. The interface of single-crystal SiC and Al brazed at 1273 K is investigated by high-resolution electron microscopy. The orientation relationship of SiC to the Al4C3 reaction layer that forms between the SiC and the Al can be expressed as (0001)SiC || (0001)Al4C3 and [1-100]SiC || [1-100]Al4C3. Furthermore, a very thin (two tetrahedral layers thick) transition phase and misfit dislocations are observed between the SiC and Al4C3 lattices. The structure of the transition phase is discussed based on the high-resolution electron microscopy, the stacking of the (Al, Si)C4 tetrahedral layers, and the charge balance. The same reaction product, with the same orientation relationships, is observed at the interface of a polycrystalline SiC and Al brazed joint. |
