共查询到20条相似文献,搜索用时 15 毫秒
1.
Jianren Zeng Yoshinari Miyamoto Osamu Yamada 《Journal of the American Ceramic Society》1991,74(9):2197-2200
Fine Si3 N4 -SiC composite powders were synthesized in various SiC compositions to 46 vol% by nitriding combustion of silicon and carbon. The powders were composed of α-Si3 N4 , β-Si3 N4 , and β-SiC. The reaction analysis suggested that the SiC formation is assisted by the high reaction heat of Si nitridation. The sintered bodies consisted of uniformly dispersed grains of β-Si3 N4 , β-SiC, and a few Si2 N2 O. 相似文献
2.
F. F. LANGE 《Journal of the American Ceramic Society》1973,56(10):518-522
A fracture mechanics approach was used to investigate the high strength of hot-pressed Si3 N4 . Room-temperature flexural strengths, fracture energies, and elastic moduli were determined for material fabricated from α- and β-phase Si3 N4 powders. When the proper powder preparation technique was used, α-phase powder resulted in a high fracture energy (69,000 ergs/cm2 ), a high flexural strength (95,000 psi), and an elongated (fiberlike) grain morphology, whereas β-phase powder produced a low fracture energy (16,000 ergs/cm2 ), a relatively low strength (55,000 psi), and an equiaxed grain morphology. It was hypothesized that the high strength of Si3 N4 hot-pressed from α-phase powder results from its high fracture energy, which is attributed to the elongated grains. High-strength Si3 N4 has directional properties caused, in part, by the elongated grain structure, which is oriented preferentially with respect to the hot-pressing direction. 相似文献
3.
Jun-Qi Li Fa Luo Dong-Mei Zhu Wan-Cheng Zhou 《Journal of the American Ceramic Society》2007,90(6):1950-1952
The influence of phase formation on the dielectric properties of silicon nitride (Si3 N4 ) ceramics, which were produced by pressureless sintering with additives in MgO–Al2 O3 –SiO2 system, was investigated. It seems that the difference in the dielectric properties of Si3 N4 ceramics sintered at different temperatures was mainly due to the difference of the relative content of α-Si3 N4 , β-Si3 N4 , and the intermediate product (Si2 N2 O) in the samples. Compared with α-Si3 N4 and Si2 N2 O, β-Si3 N4 is believed to be a major factor influencing the dielectric constant. The high-dielectric constant of β-Si3 N4 could be attributed to the ionic relaxation polarization. 相似文献
4.
The densification behavior of Si3 N4 containing MgO was studied in detail. It was concluded that MgO forms a liquid phase (most likely a magnesium silicate). This liquid wets and allows atomic transfer of Si3 N4 . Evidence of a second-phase material between the Si3 N4 grains was obtained through etching studies. Transformation of α- to β-Si3 N4 during hot-pressing is not necessary for densification. 相似文献
5.
Advanced sintering techniques for consolidation of Si3 N4 powders in the presence of an oxygen-rich liquid phase(s) require high temperatures and usually high nitrogen pressures. A stability diagram is constructed for Si3 N4 as a function of the partial pressures of nitrogen (PN2 ) and silicon (PSi ). High PN2 (20 to 100 atm) increases the stability of Si3 N4 and the oxygen-rich liquid phase by reducing the PSi and PSi0 , respectively. The region of high sinterability is outlined for submicrometer Si3 N4 powders containing 7 wt% BeSiN2 and 7 wt% SiO2 as densification aids . 相似文献
6.
D. Amutha Rani Y. Yoshizawa M. I. Jones H. Hyuga K. Hirao Y. Yamauchi 《Journal of the American Ceramic Society》2005,88(6):1655-1658
We report here the study on tribological behavior of α-Sialon in aqueous medium. The results derived from a wide range of test conditions are briefly discussed. A reduction in friction coefficient from 0.7 to 0.03 and a decrease in wear rate by two orders of magnitude were achieved under low load (9.8 N) and high speed (>0.54 m/s) conditions. The tribological behavior of α-Sialon/Si3 N4 ceramics was then compared with Si3 N4 /Si3 N4 tribopairs. 相似文献
7.
Jiang-Tao Li Lin Mei Yun Yang Zhi-Ming Lin 《Journal of the American Ceramic Society》2009,92(3):636-640
Silicon nitride (Si3 N4 ) was synthesized by a selective combustion reaction of silicon powder with nitrogen in air. The α/β-Si3 N4 ratio of the interior product could be tailored by adjusting the Si3 N4 -diluent content in the reactant mixtures. The synthetic β-Si3 N4 showed a well-crystallized rod-like morphology. Mechanical activation greatly enhanced the reactivity of silicon powder, and the slow oxidation of silicon at the sample surface promoted the combustion reaction in air. The formation mechanism of Si3 N4 was analyzed based on a proposed N2 /O2 diffusion kinetic model, and the calculated result is in good agreement with the experimental phenomenon. 相似文献
8.
KOHJI NOBUGAI SHIGEKI YABE FUMIKAZU KANAMARU 《Journal of the American Ceramic Society》1984,67(7):146-C
Thin films of amorphous Si3 N4 were prepared by the rf-sputtering method, and the effects of titanium and chlorine additives on its crystallization were examined. When Ti-doped amorphous Si3 N4 was heated, TiN precipitated at >1100°C; the TiN precipitates promoted the conversion of amorphous Si3 N4 to β-Si3 N4 . Chlorine led to preferential conversion of amorphous Si3 N4 to α-Si3 N4 . 相似文献
9.
The phase relations in the Si3 N4 -rich portion of the Si3 N4 –AlN–Y2 O3 rystem were investigated using hot-pressed bodies. The one-phase fields of β3 and α, the twophase fields of β+α, β+M (M=melilite), and α+M, and the three-phase fields of β+α+M were observed in the Si3 N4 -rich portion. The α- and β-sialons are not two different compounds but an allotropic transformation phase of the Si–Al–O–N system, and an α solid solution expands and stabilizes with increasing Y2 O3 content. Therefore, the formulas of the two sialons should be the same. 相似文献
10.
Chaitanya K. Narula Brian G. Demczyk Paul Czubarow Dietmar Seyferth 《Journal of the American Ceramic Society》1995,78(5):1247-1251
[(Trimethylsilyl)amino]titanium trichloride, (CH3 )3 -SiNHTiClj, was isolated as a red-orange crystalline solid in 58% yield from the reaction of TiCl4 with [(CH3 )3 Si]2 NH in 1:1 molar ratio in dichloromethane at —78°C. Pyrolysis of (CH3 )3 SiNHTiCl3 at 600°C furnished titanium nitride. This precursor is suitable for the preparation of composites and was employed to prepare Si3 N4 -TiN and Ti-TiN powders by adding Si3 N4 particles or titanium powders to a solution of (CH3 ), SiNHTiCl3 in dichloromethane, drying and pyrolyzing the resulting solid. This precursor also has been used as a binder to prepare Si3 N4 -TiN and Ti-TiN bodies. High-resolution transmission electron microscopic studies of the Si3 N4 -TiN composite showed that titanium nitride is concentrated on the surface of the Si3 N4 particles. 相似文献
11.
Klyoshi Hlrao Yoshinari Miyamoto Mltsue Koizumi 《Journal of the American Ceramic Society》1986,69(4):60-C-
Fine Si3 N4 powders were prepared by the combustion reaction of an Si powder compact undez 10 MPa nitrogen pressure. Addition of Si3 N4 powder to the starting Si promoted conversion of the reactants to homogeneous Si3 N4 particles. Submicrometer SisN4 powders with a uniform size distribution around 0.5 μm were obtained from a 1.8Si-0.4Si3 N4 mixture (molar ratio); they were free of residual Si. 相似文献
12.
Cha-Yang Chu Jitendra P. Singh Jules L. Routbort 《Journal of the American Ceramic Society》1993,76(5):1349-1353
The high-temperature flexural strength of hot-pressed silicon nitride (Si3 N4 ) and Si3 N4 -whisker-reinforced Si3 N4 -matrix composites has been measured at a crosshead speed of 1.27 mm/min and temperatures up to 1400°C in a nitrogen atmosphere. Load–displacement curves for whisker-reinforced composites showed nonelastic fracture behavior at 1400°C. In contrast, such behavior was not observed for monolithic Si3 N4 . Microstructures of both materials have been examined by scanning and transmission electron microscopy. The results indicate that grain-boundary sliding could be responsible for strength degradation in both monolithic Si3 N4 and its whisker composites. The origin of the nonelastic failure behavior of Si3 N4 -whisker composite at 1400°C was not positively identified but several possibilities are discussed. 相似文献
13.
Zhaohui Wang Egil Skybakmoen Tor Grande 《Journal of the American Ceramic Society》2009,92(6):1296-1302
A thorough analysis of a silicon nitride (Si3 N4 )-bonded SiC sidelining material from a Hall-Heroult electrolysis cell is reported. Phase composition before and after chemical degradation of the material is obtained by quantitative analysis using Rietveld refinement of X-ray diffraction data and chemical analysis. The main degradation products as a result of the oxidation of Si3 N4 binder phase are Si2 ON2 in the upper part and Na2 SiO3 in the lower part of the sidelining. The microstructure of α-Si3 N4 (needle) and β-Si3 N4 (shell) as well as the degradation products Si2 ON2 (fiber) and Na2 SiO3 (flake) were revealed by electron microprobe analysis. Chemical reactions and degradation mechanisms are proposed based on the presented findings. The degradation in the lower part is more severe than that in the upper part because Na diffusion from the cathode enhances the oxidation of Si3 N4 . The degradation changes the physical properties of Si3 N4 -bonded SiC such as density and porosity. 相似文献
14.
C. Greskovich 《Journal of the American Ceramic Society》1981,64(2):31-C-
The development of microstructure in hot-pressed Sia N4 was studiehd for a typical Si3 N4 powder with and without BeSiN2 as a densification aid. The effect of hot-pressing temperature on density, α- to β-Si3 N4 conversion and specific surface area showed that BeSiN2 appears to increase the mobility of the system by enhancing densification, α- to β-Si3 N4 transformation, and grain growth at temperatures between 1450° and 1800°. These processes appear to occur in the presence of a liquid phase. 相似文献
15.
Jae Young Choi Chong Hee Kim Do Kyung Kim 《Journal of the American Ceramic Society》1999,82(10):2665-2671
The synthesis and structure of a monodispersed spherical Si3 N4 /SiC nanocomposite powder have been studied. The Si3 N4 /SiC nanocomposite powder was synthesized by heating under argon a spherical Si3 N4 /C powder. The spherical Si3 N4 /C powder was prepared by heating a spherical organosilica powder in a nitrogen atmosphere and was composed of a mixture of nanosized Si3 N4 and free carbon particles. During the heat treatment at 1450°C, the Si3 N4 /C powder became a Si3 N4 /SiC composite powder and finally a SiC powder after 8 h, while retaining its spherical shape. The composition of the Si3 N4 /SiC composite powder changed with the duration of the heat treatment. The results of TEM, SEM, and selected area electron diffraction showed that the Si3 N4 /SiC composite powder was composed of homogeneously distributed nanosized Si3 N4 and SiC particles. 相似文献
16.
Jow-Lay Huang Hung-Liang Chiu Ming-Tung Lee 《Journal of the American Ceramic Society》1994,77(3):705-710
The effects of TiC addition to Si3 N4 on microstructure and the chemical aspects of Si3 N4 –TiC interphase reaction were investigated in samples hot-pressed at 1800°C in Ar and N2 . Composition of a TiC1–x Nx solid solution was predicted based on thermodynamic calculation, with titanium carbonitride taken to be an ideal solid solution. The predicted value of x = 0.7 is slightly higher than that derived from the measured lattice parameter and Vegard's law (x = 0.67). Four distinguishable areas were observed in samples hot-pressed in nitrogen atmosphere. They were identified as β-Si3 N4 , mixtures of TiC and titanium carbonitride solid solution, SiC with twins, and iron silicide. As the duration of hot-pressing increased, more titanium carbonitride was formed, while less TiC phase remained. Thermodymanic calculations indicate one source of nitrogen gas came from the decomposition of Si3 N4 . The TiC particles also became more irregular, and reactants were found inside or between TiC as the hot-pressing time was extended. Silicon carbide was not detected in samples which were hot-pressed in argon atmosphere; however, numerous pores were found around TiC. 相似文献
17.
Sintering kinetics of the system Si3 N4-Y2O3 -Al2 O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si3 N4 were studied with additions of 4 to 17 wt% Y2 O3 and 4 wt% A12 O3 . Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si3 N4 and glass or β '-Si3 N4 , α '-Si3 N4 , and glass. The compositions and amounts of the residual glassy phases are estimated. 相似文献
18.
Dariusz Kata Kenshiro Shirai Manshi Ohyanagi Zuhair A. Munir 《Journal of the American Ceramic Society》2001,84(4):726-732
The synthesis of solid solutions of AlN–SiC was investigated through the combustion reaction between Si3 N4 , aluminum, and carbon powders and nitrogen gas at pressures ranging from 0.1 to 6.0 MPa. The combustion reaction was initiated locally and then the wave front propagated spontaneously, passing through the cylindrical bed containing the loose powder. In the presence of Si3 N4 as a reactant, it was feasible to synthesize solid solutions at an ambient pressure (0.1 MPa). The relationship between nitrogen pressure and full-width at half-maximum of the (110) peak of the product showed that lower pressures produced more-homogeneous solid solutions. Some aspects of formation of the AlN–SiC solid solutions were discussed with special emphasis on the influence of nitrogen pressure and reactant stoichiometry. 相似文献
19.
The rate of dissolution of β-Si3 N4 into an Mg-Si-O-N glass was measured by working with a composition in the ternary system Si3 N4 -SiO2 -MgO such that Si2 N2 O rather than β-Si3 N4 was the equilibrium phase. Dissolution was driven by the chemical reaction Si3 N4 (c)+SiO2 ( l )→Si2 N2 O(c). Analysis of the kinetic data, in view of the morphology of the dissolving phase (Si3 N4 ) and the precipitating phase (Si2 N2 O), led to the conclusion that the dissolution rate was controlled by reaction at the crystal/glass interface of the Si3 N4 , crystals. The process appears to have a fairly constant activation energy, equal to 621 ±40 kJ-mol−1 , at T=1573 to 1723 K. This large activation energy is believed to reflect the sum of two quantities: the heat of solution of β-Si3 N4 hi the glass and the activation enthalpy for jumps of the slower-moving species across the crystal/glass interface. The data reported should be useful for interpreting creep and densification experiments with MgO-fluxed Si3 N4 . 相似文献
20.
Subsolidus Phase Relationships in Part of the System Si,Al,Y/N,O: The System Si3 N4 ─AIN─YN─Al2 O3 ─Y2 O3
Wei-Ying Sun Tseng-Ying Tien Tung-Sheng Yen 《Journal of the American Ceramic Society》1991,74(11):2753-2758
The subsolidus phase relationships in the system Si,Al,Y/N,O were determined. Thirty-nine compatibility tetrahedra were established in the region Si3 N4 ─AIN─Al2 O3 ─Y2 O3 . The subsolidus phase relationships in the region Si3 N4 ─AIN─YN─Y2 O3 have also been studied. Only one compound, 2YN:Si3 N4 , was confirmed in the binary system Si3 N4 ─YN. The solubility limits of the α'─SiAION on the Si3 N4 ─YN:3AIN join were determined to range from m = 1.3 to m = 2.4 in the formula Y m /3 Si12- m Al m N16 . No quinary compound was found. Seven compatibility tetrahedra were established in the region Si3 N4 ─AIN─YN─Y2 O3 . 相似文献