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2001 | PATENTS
| INTERNET
| Chen
J., Tian Q., Virkar A. V. Effect of Coherency
Strains on Phase Separation in the AlN - Al2OC
Pseudobinary System // J. Am. Ceram. Soc.
- 1993. - 76(10). - 2419-2432. AlN and Al2OC, both of 2H structure, form a homogeneous solid solution at elevated temperatures. Annealing at lower temperatures leads to the formation of two solid solutions, one AlN-rich and other Al2OC-rich. Samples of near equimolar composition form disk-shaped precipitates upon annealing at temperatures below ~1900°C. In the present work, samples of several compositions were fabricated by hot-pressing mixtures of AlN, Al4C3 and Al2O3. Lattice parameters of the resulting solid solutions were measured by X-ray diffraction. Samples of an equimolar composition were annealed at 1500°C for various periods of time up to a maximum of 512 h. Disk-shaped precipitates with their axes along the [0001] direction were initially coherent. In the coherent stage, the a lattice parameters of the precipitate and the matrix were identical because of coherent fitting of lattice planes. The shape of the precipitates and their orientation were in accord with predictions based on theoretical calculations of coherency strain energy. Using the experimentally measured values of the aspect ratios, the precipitate / matrix interfacial energy for coherent precipitates was estimated to be on the order of a few mJ/m2. Longterm annealing led to the loss of coherency as manifested by the formation of interface dislocations. |
| Klemm
H., Tanihata K., Miyamoto Y. Gas Pressure Combustion
Sintering and Hot Isostatic Pressing in the Titanium-Silicon-Carbon
System // J. Mater. Sci. - 1993. - 28(6). - 1557-1562. The processing of materials in the Ti-Si-C system produced by gas-pressure combustion sintering (GPCS) and hot isostatic pressing (HIP) was studied. By variation of the raw material compn. it was possible to produce different materials contg. Ti5Si3, Ti3SiC2, TiSi2, TiC, SiC, and titanium. The different phase compns. of samples with the same reactants obtained by GPCS and HIP are due to the duration of each of the processes; in GPCS the equil. state was not achieved. The properties of the specimen are strongly related to their chem. behavior during processing at high temps. Not all phases built up at the high temps. during the GPCS and HIP processes are stable at lower temps., and some reactions occur during cooling, which influence densification, microstructure, and properties of the bodies finally obtained. |
| Lis J., Pampuch R., Piekarczyk J., Stobierski L. New
Ceramics Based on Titanium Silicide Carbide (Ti3SiC2)
// Ceram. Int. - 1993. - 19(4). - 219-222. Dense polycryst. Ti3SiC2-based materials in the form of large shapes were obtained by ceramic processing starting with SHS-derived Ti3SiC2-based powders. Their high Young's and shear moduli and chem. resistance classified them as a covalent ceramic material. However, their relatively low hardness and ratio of high Young's modulus to hardness are close to those of ductile metals. |
| Maline
M., Ducarroir M., Teyssandier F., Hillel R., Berjoan R., Van Loo F.
J. J., Wakelkamp W. Auger Electron Spectroscopy
of Compounds in the Silicon-Titanium-Carbon System. Characterization
of Silicon-Titanium-Carbon Multiphased Materials Obtained by CVD
// Surf. Sci. - 1993. - 286(1-2). - 82-91. Auger peak-position and line-shape analyses of the Si LVV, Si KLL, C KVV, and Ti LMM transitions for the ref. compds. Ti, Si, SiC, TiC, TiC0.72, TiSi2, Ti5Si3(C), and Ti3SiC2, belonging to the ternary Si-Ti-C system have been performed. The results show that there are sufficient differences in Auger peak positions and line shapes to allow identification of the compds. The Auger line shapes of the C KVV transitions for Ti3SiC2 and Ti0.57Si0.33C0.1 (C solid soln. in Ti5Si3) were found to be characteristic of C bonded to Ti. The Ti L3M23M45 transition was found to be very sensitive to changes in the nature of the compds. The spectra recorded for the ref. compds. were used to characterize Si-Ti-C multiphased materials obtained by CVD. SiC-X (X = TiSi2,Ti3SiC2, or TiC + C) mixts. were identified. |
| Pampuch
R., Lis J., Piekarczyk J., Stobierski L. Ti3SiC2-based
Materials Produced by Self-Propagating High-Temperature Synthesis
(SHS) and Ceramic Processing // J. Mater.
Synth. Process. - 1993. - 1(2). - 93-100. Prepn. and characterization of a new ceramic material composed mainly of Ti3SiC2 and contg. a few percentage TiC1-x are reported. The exptl. procedure consisted of SHS from titanium-silicon-carbon powder mixts., grinding of the solid porous product into powder form, and densification of the resulting powder by hot-pressing or pressureless sintering. Dense shapes of polycryst. Ti3SiC2-based materials were obtained for the first time by such processing. Indentation testing and ultrasonic measurements of elastic were made on the material. The high Young's and shear moduli of the material classify it as a covalent ceramic. The low hardness and the high Young's modulus-to-hardness ratio of the material suggests its properties to be close to those of ductile metals. Perspectives for applications of the new material are also discussed. |
