共查询到20条相似文献,搜索用时 15 毫秒
1.
Daniel P. Riley Erich H. Kisi Thomas C. Hansen Alan W. Hewat 《Journal of the American Ceramic Society》2002,85(10):2417-2424
In situ neutron diffraction at 0.9 s time resolution was used to reveal the reaction mechanism during the self-propagating high-temperature synthesis (SHS) of Ti3 SiC2 from furnace-ignited stoichiometric 3Ti + SiC + C mixtures. The diffraction patterns indicate that the SHS proceeded in five stages: (i) preheating of the reactants, (ii) the α→β phase transformation in Ti, (iii) preignition reactions, (iv) the formation of a single solid intermediate phase in <0.9 s, and (v) the rapid nucleation and growth of the product phase Ti3 SiC2 . No amorphous contribution to the diffraction patterns from a liquid phase was detected and, as such, it is unlikely that a liquid phase plays a major role in this SHS reaction. The intermediate phase is believed to be a solid solution of Si in TiC such that the overall stoichiometry is ∼3Ti:1Si:2C. Lattice parameters and known thermal expansion data were used to estimate the ignition temperature at 923 ± 10°C (supported by the α→β phase transformation in Ti) and the combustion temperature at 2320 ± 50°C. 相似文献
2.
José M. Córdoba María J. Sayagués María D. Alcalá Francisco J. Gotor 《Journal of the American Ceramic Society》2007,90(3):825-830
Titanium silicon carbide (Ti3 SiC2 ) and Ti3 SiC2 -based composite powders were synthesized by isothermal treatment in an inert atmosphere as a function of initial compositions (mixtures). A high content of TiC was obtained in the final product when the initial mixtures contained free carbon. The use of TiC as a reagent was unsuccessful in obtaining Ti3 SiC2 . High Ti3 SiC2 conversion was found for the initial mixtures containing SiC as the main source for silicon and carbon. An initial mixture with a large excess of silicon, 3Ti/1.5SiC/0.5C, was needed to obtain high-purity Ti3 SiC2 . A reaction mechanism, where Ti3 SiC2 nucleates on Ti5 Si3 C crystals and grows by long-range diffusion of Ti and C, is proposed. The reaction mechanism was proposed to be based on silicon loss during the formation of Ti3 SiC2 . 相似文献
3.
Erdong Wu Erich H. Kisi Daniel P. Riley Ronald I. Smith 《Journal of the American Ceramic Society》2002,85(12):3084-3086
The reactive sintering of 3Ti/SiC/C to form the layered ternary carbide Ti3 SiC2 was studied in situ by time-resolved neutron powder diffraction. A number of intermediate processes occur during the synthesis beginning with the α-β transition in Ti. Concurrent with the α-β transition, two intermediate phases, TiC x and Ti5 Si3 C x ( x ≤ 1), form. These phases account for almost the entire sample in the range 1500–1600°C beyond which they react with each other and a small amount of free C to form the product phase Ti3 SiC2 . 相似文献
4.
Fred Goesmann Roland Wenzel Rainer Schmid-Fetzer 《Journal of the American Ceramic Society》1998,81(11):3025-3028
This paper describes a novel way to prepare the ternary phase Ti3 SiC2 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. 相似文献
5.
Jing-Feng Li Toshiro Matsuki Ryuzo Watanabe 《Journal of the American Ceramic Society》2002,85(4):1004-1006
Mechanical alloying (MA) has been used to synthesize Ti3 SiC2 powder from the elemental Ti, Si, and C powders. The MA formation conditions of Ti3 SiC2 were strongly affected by the ball size for the conditions used. MA using large balls (20.6 mm in diameter) enhanced the formation of Ti3 SiC2 , probably via an MA-triggered combustion reaction, but the Ti3 SiC2 phase was not synthesized only by the MA process using small balls (12.7 mm in diameter). Fine powders containing 95.8 vol% Ti3 SiC2 can be obtained by annealing the mechanically alloyed powder at relatively low temperatures. 相似文献
6.
Chunfeng Hu Yanchun Zhou Yiwang Bao Detian Wan 《Journal of the American Ceramic Society》2006,89(11):3456-3461
Tribological properties of Ti3 SiC2 and Al2 O3 -reinforced Ti3 SiC2 composites (10 and 20 vol% Al2 O3 ) were investigated by using an AISI-52100 bearing steel ball dryly sliding on a linear reciprocating athletic specimen. The friction coefficients were found varying only in a range of 0.1 under the applied loads (2.5, 5, and 10 N), and the wear rates of the composites decreased with increasing Al2 O3 content. The enhanced wear resistance is mainly attributed to the hard Al2 O3 particles nail the surrounding soft matrix and decentrale the shear stresses under the sliding ball to reduce the wear losses. 相似文献
7.
Tamer El-Raghy Antonios Zavaliangos Michel W. Barsoum Surya R. Kalidindi 《Journal of the American Ceramic Society》1997,80(2):513-516
Microstructural observations of damage around indentations in Ti3 SiC2 are presented. The Vickers hardness decreased with increasing load and asymptotically approached 4 GPa at the highest loads. No indentation cracks were observed even at loads as high as 300 N. Preliminary strength versus indentation plots indicate that, at least for the large-grained material (is approximately100 μm) studied here, Ti3 SiC2 is a damage-tolerant material able to contain the extent of microdamage to a small area around the indent. The following multiple energy-absorbing mechanisms have been identified from scanning electron micrographs of areas in the vicinity of the indentation: diffuse microcracking, delamination, crack deflection, grain push-out, grain pull-out, and the buckling of individual grains. 相似文献
8.
D. Sarkar B. Basu S. J. Cho M. C. Chu S. S. Hwang S. W. Park 《Journal of the American Ceramic Society》2005,88(11):3245-3248
The present contribution reports the unlubricated friction and wear properties of Ti3 SiC2 against steel. The fretting experiments were performed under varying load (1–10 N) and the detailed wear mechanism is studied using SEM-EDS, Raman spectroscopy, and atomic force microscopy. Under the selected fretting conditions, Ti3 SiC2 /steel tribocouple exhibits a transition in friction as well as wear behavior with coefficient of friction varying between 0.5 and 0.6 and wear rate in the order of 10−5 mm3 ·(N·m)−1 . Raman analysis reveals that the fretting wear is accompanied by the triboxidation with the formation of TiO2 , SiO2 , and Fe2 O3 . A plausible explanation for the transition in friction and wear with load is proposed. 相似文献
9.
Polycrystalline bulk samples of Ti3 SiC2 were fabricated by reactively hot-pressing Ti, graphite, and SiC powders at 40 MPa and 1600°C for 4 h. This compound has remarkable properties. Its compressive strength, measured at room temperature, was 600 MPa, and dropped to 260 MPa at 1300°C in air. Although the room-temperature failure was brittle, the high-temperature load-displacement curve shows significant plastic behavior. The oxidation is parabolic and at 1000° and 1400°C the parabolic rate constants were, respectively, 2 × 10−8 and 2 × 10−5 kg2 -m−4 .s−1 . The activation energy for oxidation is thus =300 kJ/mol. The room-temperature electrical conductivity is 4.5 × 106 Ω−1 .m−1 , roughly twice that of pure Ti. The thermal expansion coefficient in the temperature range 25° to 1000°C, the room-temperature thermal conductivity, and the heat capacity are respectively, 10 × 10−6 °C−1 , 43 W/(m.K), and 588 J/(kgK). With a hardness of 4 GPa and a Young's modulus of 320 GPa, it is relatively soft, but reasonably stiff. Furthermore, Ti3 SiC2 does not appear to be susceptible to thermal shock; quenching from 1400°C into water does not affect the postquench bend strength. As significantly, this compound is as readily machinable as graphite. Scanning electron microscopy of polished and fractured surfaces leaves little doubt as to its layered nature. 相似文献
10.
Leonid Farber Michel W. Barsoum Antonios Zavaliangos Tamer El-Raghy Igor Levin 《Journal of the American Ceramic Society》1998,81(6):1677-1681
The ternary carbide Ti3 SIC2 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. 相似文献
11.
Sui Lin Shi Wei Pan Ming Hao Fang Zhen Yi Fang 《Journal of the American Ceramic Society》2006,89(2):743-745
Ti3 SiC2 /HAp composites with different Ti3 SiC2 volume fractions were fabricated by spark plasma sintering (SPS) at 1200°C. The effects of Ti3 SiC2 addition on the mechanical properties and microstructures of the composites were investigated. The bending strength and fracture toughness of the composites increased with increasing of Ti3 SiC2 content, whereas the Vickers hardness decreased. The bending strength and fracture toughness reached 252±10 MPa and 3.9±0.1 MPa·m1/2 , respectively, with the addition of 50 vol% Ti3 SiC2 . The increases in the mechanical properties were attributed to the matrix strengthening and interactions between cracks and the Ti3 SiC2 platelets. 相似文献
12.
P. Mogilevsky Tai-Il Mah T. A. Parthasarathy C. M. Cooke 《Journal of the American Ceramic Society》2006,89(2):633-637
Composites in the SiC–TiC–Ti3 SiC2 system were synthesized using reactive hot pressing at 1600°C. The results indicate that addition of Ti3 SiC2 to SiC leads to improved fracture toughness. In addition, high microhardness can be retained if TiC is added to the material. The best combination of properties obtained in this study is K I c =8.3 MPa·m1/2 and H v =17.6 GPa. The composition can be tailored in situ using the decomposition of Ti3 SiC2 . Ti3 SiC2 decomposed rapidly at temperatures above 1800°C, but the decomposition could be conducted in a controlled manner at 1750°C. This can be used for synthesis of fully dense composites with improved properties by first consolidating to full density a softer Ti3 SiC2 -rich initial composition, and then using controlled decomposition of Ti3 SiC2 to achieve the desired combination of microhardness and fracture toughness. 相似文献
13.
In this article, the first part of a two-part study, we report the reaction path and microstructure evolution during the reactive hot isostatic pressing of Ti3 SiC2 , starting with titanium, SiC, and graphite powders. A series of interrupted hot isostatic press runs have been conducted as a function of temperature (1200°–1600°C) and time (0–24 h). Based on X-ray diffractometry and scanning electron microscopy, at 1200°C, the intermediate phases are TiC x and Ti5 Si3 C x . Fully dense, essentially single-phase samples are fabricated in the 1450°–1700°C temperature range. The time-temperature processing envelope for fabricating microstructures with small (3–5 μm), large (∼200 μm), and duplex grains, in which large (100–200 μm) Ti3 SiC2 grains are embedded in a much finer matrix, is delineated. The microstructure evolution is, to a large extent, determined by (i) the presence of unreacted phases, mainly TiC x , which inhibits grain growth; (ii) a large anisotropy in growth rates along the c and a directions (at 1450°C, growth normal to the basal planes is about an order of magnitude smaller than that parallel to these planes; at 1600°C, the ratio is 4); and (iii) the impingement of grains. Ti3 SiC2 is thermally stable under vacuum and argon atmosphere at temperatures as high as 1600°C for as long as 24 h. The influence of grain size on the mechanical properties is discussed in the second part of this study. 相似文献
14.
Adrish Ganguly Michel W. Barsoum Roger D. Doherty 《Journal of the American Ceramic Society》2007,90(7):2200-2204
In this work, we report on the interdiffusion of Ge and Si in Ti3 SiC2 and Ti3 GeC2 , as well as that of Nb and Ti in Ti2 AlC and Nb2 AlC. The interdiffusion coefficient, D int , measured by analyzing the diffusion profiles of Si and Ge obtained when Ti3 SiC2 –Ti3 GeC2 diffusion couples are annealed in the 1473–1773 K temperature range at the Matano interface composition (≈Ti3 Ge0.5 Si0.5 C2 ), was found to be given by
Dint increased with increasing Ge composition. At the highest temperatures, diffusion was halted after a short time, apparently by the formation of a diffusion barrier of TiC. Similarly, the interdiffusion of Ti and Nb in Ti2 AlC–Nb2 AlC couples was measured in the 1723–1873 K temperature range. The D int for the Matano interface composition, viz. ≈(Ti0.5 ,Nb0.5 )2 AlC, was found to be given by
At 1773 K, the diffusivity of the transition metal atoms was ≈7 times smaller than those of the Si and Ge atoms, suggesting that the former are better bound in the structure than the latter. 相似文献
D
At 1773 K, the diffusivity of the transition metal atoms was ≈7 times smaller than those of the Si and Ge atoms, suggesting that the former are better bound in the structure than the latter. 相似文献
15.
Formation of titanium silicon carbide (Ti3 SiC2 ) by mechanical alloying (MA) of Ti, Si, and C powders at room temperature was experimentally investigated. A large amount of granules less than 5 mm in size, consisting of Ti3 SiC2 , smaller TiC particles, and other silicides, have been obtained after ball milling for only 1.5 h. The effect of excess Si in the starting powders on the formation of Ti3 SiC2 was studied. The formation mechanism of Ti3 SiC2 was analyzed. It is believed that a mechanically induced self-propagating reaction is ignited during the MA process. A possible reaction mechanism was proposed to explain the formation of the final products. 相似文献
16.
In this paper, we report a machinable Ti3 SiC2 /hydroxyapatite (HAp) composite prepared by spark plasma sintering. The experimental results of a drilling test demonstrated that the composites exhibit excellent machinability when the Ti3 SiC2 content is higher than 20 vol%, which can be attributed to the improvement in the mechanical and machinable properties of the composites by addition of Ti3 SiC2 phase, which possessess unique mechanical and machinable properties and energy-absorbing mechanisms. The superior mechanical and machinable properties of Ti3 SiC2 /HAp composites suggest that the composite system could be attractive for practical applications of novel biomaterials. 相似文献
17.
Jing-Feng Li Toshiro Matsuki Ryuzo Watanabe 《Journal of the American Ceramic Society》2005,88(5):1318-1320
Mechanical alloying (MA) synthesis of Ti3 SiC2 from a stoichiometric elemental powder mixture of Ti, Si, and C was conducted by using a planetary mill with a specially designed MA jar, which enables the real-time measurement of temperature and gas pressure during the MA process. Sudden gas pressure and temperature rises were detected when the mixed powders were mechanically alloyed for a certain period, and consequently a large amount of Ti3 SiC2 particles was synthesized. Using the Ti–Si–C system as an example, the present study confirmed the combustion reaction triggered by the ball-milling process for the first time. 相似文献
18.
19.
The effect of vacuum annealing on the thermal stability and phase transition of Ti3 SiC2 has been investigated by X-ray diffraction (XRD), neutron diffraction, synchrotron radiation diffraction, and secondary ion mass spectroscopy (SIMS). In the presence of vacuum or a controlled atmosphere of low oxygen partial pressure, Ti3 SiC2 undergoes a surface dissociation to form nonstoichiometric TiC and/or Ti5 Si3 C x that commences at ∼1200°C and becomes very pronounced at ≥1500°C. Composition depth profiling at the near surface of vacuum-annealed Ti3 SiC2 by XRD and SIMS revealed a distinct gradation in the phase distribution of TiC and Ti5 Si3 C x with depth. 相似文献