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2001 | PATENTS
| INTERNET
| Amer
M., Barsoum M. W., El-Raghy T., Wiess I., LeClair S., Liptak D. Raman
Spectrum of Ti3SiC2
// J. Appl. Phys. - 1998. - 84(10). - 5817-5819. In this letter, the Raman spectrum of Ti3SiC2 is reported and compared with that of TiC0.67. All the TiC0.67 first order Raman disorder-induced modes are active, but shifted, in Ti3SiC2. Two additional peaks at 150 and 372 cm-1 are observed in Ti3SiC2. The former is ascribed to a shear mode between the Si and Ti planes; the origin of the latter is unknown. No second order Raman bands are detected. Micro-Raman spectroscopy also reveal the presence of divide; 50 * graphite crystallites in samples hot pressed in graphite dies - these crystallites are not detected in samples processed by hot isostatic pressing in molten glass containers. |
| El-Raghy T., Barsoum M. W. Diffusion Kinetics of the
Carburization and Silicidation of Ti3SiC2
// J. Appl. Phys. - 1998. - 83. - 112-119. The ternary carbide Ti3SiC2 possesses a unique set of properties that could render it a material of considerable technological impact. The motivation for this work was to enhance the hardness and oxidation resistance of Ti3SiC2 by altering its surface chemistry. Reaction of Ti3SiC2 with single crystal Si wafers resulted in the formation of a dense surface layer composed of a two phase mixture of TiSi2 and SiC. This layer grows in two distinct morphologies; an outer layer with fine (1-5 mm) SiC particles and an inner coarser (10-15 mm) one. The overall growth rates of the layers were parabolic. Comparison with previously published results supports the conclusion that diffusion of Si through TiSi2 is rate limiting. In the 1400-1600 °C temperature range, reaction of Ti3SiC2 with graphite foils resulted in the formation of a 15 vol. % porous surface layer of TiCx (where x > 0.8). It is shown that the carburization kinetics are rate limited by the diffusion of C through TiCx. Both carburization and silicidation increased surface hardness; the latter also enhanced the oxidation resistance by about three orders of magnitude. |
| Farber
L., Barsoum M. W., Zavaliangos A., El-Raghy T., Levin I. Dislocations
and Stacking Faults in Ti3SiC2
// J. Amer. Cer. Soc. - 1998. - 81. - 1677-1681. The ternary carbide Ti3SIC2 fabricated by a reactive hot-press route is investigated by transmission electron microscopy. The material consists mainly of large elongated grains with planar boundaries, and is characterized by a low defect density. Dislocations are observed in the grains and at grain boundaries. Perfect dislocations with b = 1/3<1120> lying in (0001) basal planes are present. These basal plane dislocations are mobile and multiply as a result of room-temperature deformation. All of the stacking faults observed lie in the basal planes. |
| Gao
N., Miyamoto Y., Tanihata K. Synthesis and Characterization
of High-Density Ti3SiC2
by Hot Isostatic Pressing // Zairyo - 1998.
- 47(10). - 994-999. (Japanese). [no abstract] |
| Goesmann
F., Wenzel R., Schmid-Fetzer R. Metalization
Studies on Ti3SiC2-based
Contacts on 6H-SiC // J. Mater. Sci.: Mater.
Electron. - 1998. - 9(2). - 103-107. [no abstract] |
| Goesmann
F., Wenzel R., Schmid-Fetzer R. Preparation
of Ti3SiC2
by Electron-Beam-Ignited Solid-State Reaction
// J. Amer. Cer. Soc. - 1998. - 81(11). - 3025-3028. This paper describes a novel way to prepare the ternary phase Ti3SiC2 in a single-step procedure that we call electron-beam-ignited solid-state reaction (EBI-SSR). The preparation route is discussed by means of an isothermal section of the Ti-Si-C phase diagram. Properties such as the Vickers hardness and the electrical resistivity of the resulting samples are presented. Our property data compare well to those that have been published. The main advantages of this preparation method are the controllability of process parameters such as heating rates, temperatures, and times, as well as the short duration of the overall sample preparation. However, a disadvantage is the presence of second phases (typically in amounts of <8%) that must be reduced via further optimization of the process. |
| Grigoryan H. E., Rogachev A. S., Ponomarev V. I., Levashev E. A. Structure
Formation during Gasless Combustion in the Ti-Si-C System //
International Journal of SHS. - 1998. - 7(4). - 507-556. [no abstract] |
| Kisi
E. H., Crossley J. A. A., Myhra S.,
Barsoum M. W. Structure and Crystal
Chemistry of Ti3SiC2
// J. Phys. Chem. Sol.. - 1998. - 59. - 1437-1443. The carbide-derived layered Ti3SiC2 has an unusual combination of electrical, thermal and mechanical properties. The structure of Ti3SiC2 has been refined from Rietveld analysis of neutron diffraction patterns. The c-axis stacking sequence includes double layers of distorted edge sharing CTi6 octahedra, reminiscent of the TiC structure. The double layers are separated by square-planar Si sheets. Bond-lengths and angles were measured to greater accuracy than in previous studies. The refined structure is used in conjunction with data from X-ray photoelectron spectroscopy (XPS) to hypothesize that the origin of the observed high electrical conductivity is with the Ti-C blocks. The XPS analysis shows that both Ti and C species are exceptionally well-screened, even comparison with other carbides. As well, surface-specific compositional analysis by XPS shows that freshly prepared fracture faces exhibit relatively high Ti abundance while the Si abundance is low, in comparison with expected bulk stoichiometry. [PDF-289kb] |
| Lee
S. K. Effect of Grain Size on Plasticity of
Ti3SiC2
// Yoop Hakhoechi - 1998. - 35(8). - 807-812. (Korean). [no abstract] |
| Lee
S. K. Mechanical Properties and Contact Damage
Behavior of Ti3SiC2
// Yoop Hakhoechi - 1998. - 35(4). - 333-338. (Korean). [no abstract] |
| Lis J., Rudnik T., Pampuch R. Controlled Reactions
in SHS-derived Ti–Si–C Materials // International
Journal of Self-Propagating High-Temperature Synthesis. - 1998. -
7(2). - 189 – 199. [no abstract] |
| Low
I. M. Vickers Contact Damage of Micro-layered
Ti3SiC2
// J. Eur. Ceram. Soc. - 1998. - 18(6). - 709-713. The nature, evolution, and degree of deformation-microfracture damage around and beneath Vickers contacts in monophase Ti3SiC2 (312) are studied. The 312 material exhibits a pronounced shear deformation during indentation, indicating microscale plasticity which can be associated with intragrainmultiple basal-plane slip between micro-lamellae, intergrain sliding, lamellae or grain push-out, and microfailures at the ends of the constrained shear-slips. No contact-induced cracks are observed and the micro-damage is widely distributed within the shear-compression zone around and below the contacts. The damage process is stochastic which results from a complex interplay of statistical variation in both relative size and crystallographic orientation of individual grains. The ability of 312 to absorb energy from the loading system and to distribute damage is somewhat akin to that of ceramics with either coarse-grained or heterogeneous microstructures, and perhaps geological structures. |
| Low
I. M., Lee S. K., Lawn B. R., Barsoum M. W. Contact
Damage Accumulation in Ti3SiC2
// J. Amer. Cer. Soc. - 1998. - 81. - 225-228. The evolution of deformation-microfracture damage below Hertzian contacts in a coarse-grain Ti3SiC2 is studied. The Hertzian indentation stress-strain response deviates strongly from linearity beyond a well-defined maximum, with pronounced strain-softening, indicating exceptional deformability in this otherwise (elastically) stiff ceramic. Surface and subsurface ceramographic observations reveal extensive quasi-plastic microdamage zones at the contact sites. These damage zones are made up of multiple intragrain slip and intergrain shear failures, with attendant microfracture at high strains. No ring cracks or other macroscopic cracks are observed on or below the indented surfaces. The results suggest that Ti3SiC2 may be ideally suited to contact applications where high strains and energy absorption prior to failure are required. |
| Pickering
E., Lackey W. J, Crain S. Thermodynamic Modeling
of the Ti-Si-C-H-Cl-Ar System to Determine Optimum Conditions for
Chemical Vapor Deposition of Ti3SiC2 // Ceram. Eng. Sci. Proc.
- 1998. - 19(4). - 541-552. Thermodn. modeling of the Ti-Si-C-H-Cl-Ar system is presented in order to better understand the conditions surrounding chem. vapor deposition of Ti3SiC2. This ternary compd. is classified as a soft, mech. tough ceramic, and as such, is a strong candidate as a matrix material or fiber-matrix interface coating in fiber reinforced composites synthesized using forced flow-thermal gradient chem. vapor infiltration. The computer program SOLGASMIX was used to calc. deposition diagrams for the TiCl4-SiCl4-CCl4-H2 reagent system. The effects of hydrogen to reagent concn., temp., and pressure were explored with a "box" type study, surrounding a middle condition of 1300 K, 760 torr, and hydrogen to reagent concn. ratio of 20:1. Results suggest that Ti3SiC2 prefers to deposit at lower hydrogen to reagent concns., and lower temps. but higher pressures. |
| Shigehiro
K., Nobuyuki S., Fumitaka I., Michihiko N., Tatsushi O., Kei A. Microstructure
and High-Temperature Tensile Properties of TiC/Ti5Si3/Ti3SiC2
Fine Composites Prepared by Mechanical Alloying
// J. Japan Inst. Metals - 1998. - 62(1). - 30-36. Microstructure and tensile properties at elevated temps. of fine composites prepd. by mech. alloying of Ti and SiC powders have been investigated. Mixts. of elemental Ti and SiC powders in the compn. of Ti-24 mass% SiC are milled under an Ar atm. using an attritor ball mill. After milling for 36 ks, formation of TiC and Ti5Si3 is obsd. and further milling in the presence of added n-heptane for 3.6 ks makes the powder particles finer. Milled powders are consolidated by hot pressing at 1773 K for 10.8 ks under 70 MPa and hot isostatic pressing at 1773 K for 10.8 ks under 196 MPa. The compact consists of mostly equi-axed TiC and Ti5Si3 grains of an av. diam. of 0.86 .mu.m partially mixed with plate-like phase of Ti3SiC2. The compact shows elongation of 130% at tensile test at 1773 K with an initial strain rate of 4.0 .times. 10-4 s-1 with the strain rate sensitivity exponent of 0.38. Most grains remain equi-axed after tensile test, while random orientations of plate-like phases of Ti3SiC2 turn parallel along the tensile axis. The large elongation obsd. above 1773 K is likely due to the superplasticity, while rotation of the plate-like phase accompanies deformation of the surrounding matrix. |
| Zhou Y., Sun Z., Chen S., Yi Z. In-situ Hot Pressing
/ Solid-Liquid Reaction Synthesis of Dense Titanium Silicon Carbide
Bulk Ceramics // Mater. Res. Innovations - 1998. - 2(3). -
142-146. An in-situ hot pressing/solid-liquid reaction process was developed for the synthesis of dense polycrystalline Ti3SiC2 ceramics using Ti, Si, and graphite powders as starting materials. The present work demonstrated that this process was one of the most effective and simple methods for the preparation of dense bulk Ti3SiC2 materials. Lattice constants of a=3.068 and c=17.645 are calculated for Ti3SiC2 made through this process. The synthesis temperature influenced the phase composition, microstructure and mechanical properties of Ti3SiC2 prepared at different temperatures. And bulk materials with flexural strength of 480 MPa and fracture toughness of 7.88 MPa.m1/2 were obtained at 1600°C. The high fracture toughness and strength are discussed based on microstructure analysis. |
