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1.
Jean-Bernard Veyret Marcel Van de Voorde Michel Billy 《Journal of the American Ceramic Society》1992,75(12):3289-3292
The oxidation behavior of the silicon yttrium oxynitride Y10 Si7 O23 N4 , so-called H-phase, in the temperature range 700–1400°C has been investigated. A nitrogen retention phenomenon in the oxidation product Y4.67 (SiO4 )3 O (O-apatite) is discussed. The H-phase is one of the four quaternary compounds identified in hot-pressed Si3 N4 materials fabricated within the Si3 N4 –SiO2 –Y2 O3 pseudoternary system. 相似文献
2.
Processing, Mechanical Properties, and Oxidation Behavior of Silicon Oxynitride Ceramics 总被引:2,自引:0,他引:2
Masayoshi Ohashi Shuzo Kanzaki Hideyo Tabata 《Journal of the American Ceramic Society》1991,74(1):109-114
Silicon oxynitride ceramics were prepared by hot-pressing an equimolar Si3 N4 + SiO2 mixture with 3 mol% CeO2 . The Ce2 O3 /SiO2 ratio of intergranular phase (liquid phase) increased as the formation of Si2 N2 O proceeded. The intergranular liquid remained as a glass on cooling until the Ce2 O3 /SiO2 ratio exceeded a certain value, at which point the liquid crystallized. There were great differences in thermal and mechanical properties and oxideation behavior between the specimen containing intergranular glassy phase and the one containing intergranular crystalline phase (Ce5 (SiO4 )3 N–Ce4.67 (SiO4 )3 O). The specimen containing the intergranular glassy phase showed excellent hightemperature strength and oxidation resistance. 相似文献
3.
Oxidation Behavior of Oxynitride Glasses 总被引:1,自引:0,他引:1
R. R. Wusirika 《Journal of the American Ceramic Society》1985,68(11):294-C
Oxynitride glasses begin to oxidize in air when they are heated above 800°C. The oxidation starts with bubble formation on the surface. Continued oxidation leads to a white oxide layer on the surface. Magnesia- and lithia-containing glasses formed crystalline layers, whereas soda- and baria-containing glasses formed bubbly glass layers. The lithia-, beryllia-, and magnesia-containing glasses have good oxidation resistance 相似文献
4.
Brian W. Sheldon 《Journal of the American Ceramic Society》1996,79(11):2993-2996
The oxidation kinetics of Si3 N4 were modeled by describing the simultaneous diffusion and reaction of interstitial oxygen that is believed to occur inside of the silicon oxynitride interlayer. The oxynitride was assumed to have a variable composition, and oxidation was described as a reaction where interstitial oxygen is incorporated into the network structure of the oxynitride and nitrogen is removed. It was assumed that both the diffusion coefficient and the solubility of interstitial oxygen decrease as the nitrogen content of the network structure increases. The results accurately describe both the formation of an oxynitride layer during oxidation, and the relatively slow oxidation kinetics of Si3 N4 (compared to Si and SiC). 相似文献
5.
Oxidation Behavior of Silicon Carbide 总被引:4,自引:0,他引:4
The oxidation of purified green silicon carbide in controlled atmospheres was studied by weight-gain measurement and by observation of the surface reaction products, including optical measurement of the thickness of the oxide surface film. The rate of oxidation was much greater for silicon carbide in contact with fluid silicate glasses than for silicon carbide alone. In a vacuum of 0.1 mm., oxidation proceeded with loss of weight, because of the formation of volatile SiO2 , and at a greater rate than at atmospheric pressure. It is postulated that the rate-controlling process in the normal oxidation of silicon carbide is the formation of solid SiO2 on the surface. 相似文献
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The Thermodynamic Properties of Silicon Oxynitride 总被引:1,自引:0,他引:1
A critical assessment of thermal and equilibrium data for silicon oxynitride (Si2 N2 O) is presented. Selected values for the heat of formation of Si2 N2 O from the elements and the absolute entropy of Si2 N2 O at 298.15 K are ΔH0 f,298 =−947.7 ± 5.4 kJ/mol and S0 298 = 45.35 ± 0.4 J/mol·K, respectively. A table of thermodynamic functions for Si2 N2 Ofrom 298 to 2500 K, which has been calculated from the analysis of the literature data, is also presented. 相似文献
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9.
Priya Mukundhan Jianqing Wu Henry H. Du 《Journal of the American Ceramic Society》1999,82(8):2260-2262
The oxidation behavior of NBD 200 Si3 N4 containing 1 wt% MgO sintering aid was investigated in oxygen at 900°-1300°C. The oxide growth followed a parabolic rate law with an apparent activation energy of 260 kJ/mol. The oxide layers were enriched with sodium and magnesium because of outward diffusion of intergranular Na+ and Mg2+ cations in the ceramics. The 2-4 orders of magnitude higher oxidation rate for NBD 200 Si3 N4 than for other Si3 N4 ceramics with a similar amount of MgO could be attributed to the presence of sodium. The oxidation process was most likely rate limited by grain-boundary diffusion of Mg2+ . 相似文献
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分别在500 ℃、700 ℃、900 ℃及1 100 ℃空气条件下,对石墨及渗硅石墨进行氧化实验,以分析熔融渗硅对等静压石墨氧化行为的影响。采用扫描电镜(SEM)分析了样品表面及内部形貌,通过压汞法表征了样品的孔隙结构,并对材料的力学性能进行了测试分析。结果表明:500 ℃条件下,石墨和渗硅石墨均未发生明显的氧化失重现象;温度为700 ℃时,石墨的氧化失重率随时间延长明显增加,而该温度下渗硅石墨的氧化失重率变化较小。而且,渗硅石墨在700 ℃时仍能保持较好的强度,而此温度下,石墨随氧化时间的延长,强度明显降低,甚至被氧化成粉末状。因此,熔融渗硅在提高材料抗氧化性能的同时能够显著提升材料的强度。 相似文献
12.
Michael K. Cinibulk Gareth Thomas Sylvia M. Johnson 《Journal of the American Ceramic Society》1992,75(8):2044-2049
The oxidation behavior and microstructure of the oxidized surfaces of RE2 Si2 O7 –Si3 N4 ceramics were investigated. The high oxidation resistance of these materials at 1400°C is attributed to the minimization of amorphous phases via devitrification to disilicates that are in equilibrium with SiO2 , the oxidation product of Si3 N4 . Crystals of RE2 Si2 O7 grew out of the surface silicate in prefered orientations that were dictated by crystal structure. The morphology of the microstructure of the oxidized surfaces was shown to be partially dependent on the concentration of impurities; the presence of Ca was found to coincide with the growth of Gd2 Si2 O7 and Dy2 Si2 O7 crystals with high aspect ratios. 相似文献
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Microstructure and Oxidation Behavior of Silicon Carbide Fibers Derived from Polycarbosilane 总被引:2,自引:0,他引:2
Michio Takeda Akira Urano Jun-ichi Sakamoto Yoshikazu Imai 《Journal of the American Ceramic Society》2000,83(5):1171-1176
Polycarbosilane-derived SiC fibers (CG Nicalon, Hi-Nicalon, and Hi-Nicalon type S) were exposed for 1–100 h at 1273–1673 K in air. Oxide layer growth and changes in tensile strength for these fibers were examined after exposure. The three types of SiC fibers decreased in strength as the oxide layer thickness increased. Fracture origins were located near the oxide layer–fiber interface. The Hi-Nicalon type S showed better oxidation resistance than the other polycarbosilane-derived SiC fibers after exposure in air at 1673 K for 10 h. This result was attributed to the nature of the silicon oxide layer on the surface of the SiC fibers. 相似文献
15.
Wai Lin Jenn-Ming Yang Su-Jen Ting re Ezis C. James Shih 《Journal of the American Ceramic Society》1992,75(11):2945-2952
The development of a novel TiN-reinforced silicon nitride/silicon oxynitride composite using an innovative in situ TiN-forming technique was investigated. Silicon powder compacts containing various amounts of TiO2 (anatase structure) and sintering additives were nitrided under N2 atmosphere and then further densified by hot pressing. The microstructure of the resultant composite was analyzed by X-ray diffraction, scanning electron microscopy, and solid-state nuclear magnetic resonance spectroscopy. The results of this study show that TiO2 can be successfully converted to TiN during the nitridation of Si + TiO2 mixture. The TiO2 content affects not only the microstructure of the matrix but also the composition of the intergranular phase. The type and amount of sintering additives also show a significant effect on the microstructural development of the composite. 相似文献
16.
以微米硅(Si)和纳米碳黑(Cp)粉体为主要原料,采用经机械化学法合成的碳化硅(SiC)和15%和25%的纳米碳颗粒与碳化硅(Cp-SiC)的复合粉体,并经无压烧结得到了Cp/SiC陶瓷基复合材料,分析了在不同温度条件下Cp/SiC烧结体的氧化行为。结果表明:当温度小于700℃时,Cp/SiC复合陶瓷在空气中的氧化受C—O2反应控制,致使其为均匀氧化;700℃时,氧化后的复合材料显气孔率最大,弯曲强度达极小值;大于700℃,氧化过程受O2的气相扩散控制,呈非均匀氧化;700~900℃之间,O2通过微裂纹的扩散控制着Cp/SiC的氧化过程;900~1 100℃之间,O2通过SiC缺陷的扩散控制着Cp/SiC的氧化过程,并在1 000℃时的最初的2 h内,复合材料弯曲强度增大,且达到了极大值。同时表明,纳米碳含量是影响复合材料强度及氧化行为的关键因素,添加纳米碳质量分数为15%的Cp/SiC复合陶瓷可以作为一种抗氧化性能优良的玻璃夹具材料。 相似文献
17.
LI Shibin RU Hongying GAO Jiqiang JIN Zhihao 《中国耐火材料》2006,15(2):22-26
1IntroductionThere are strong interests in identifying approa-ches to protect silicon carbide ceramics from high tem-perature oxidative environments and prolong their serv-ice lives.One method is to apply a refractory coating.The advantage of coating tech… 相似文献
18.
Kiyoshi Okada Koyo Fukuyama Yoshikazu Kameshima 《Journal of the American Ceramic Society》1995,78(8):2021-2026
Surface-oxidized phases on α-silicon nitride, β-silicon nitride, and silicon oxynitride powders were investigated by X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy (XAES). The spectra of Si2 p XPS and Si( KLL ) XAES were measured precisely and were deconvoluted into some separate peaks, which correspond to each parent phase, a SiO x N y , oxidized phase, a nonstoichiometric SiN x . nitride phase, and a satellite peak of the parent phase, by the least-squares method. The Auger parameter (AP) was calculated for each phase using the Si2 p XPS and Si( KLL ) XAES data, and the average chemical compositions of the oxidized phases in each sample were evaluated from the AP data. The chemical compositions of these phases were between those of silica and silicon oxynitride and varied among the samples, but were usually close to SiO2 . Average thicknesses of the surface-oxidized phases were estimated to be 0.1–0.8 nm from the peak area ratio of the oxidized phase against the parent phase of the XAES spectra, assuming a continuous surface layer model. 相似文献
19.
Oxidation Behavior of a Fully Dense Polymer-Derived Amorphous Silicon Carbonitride Ceramic 总被引:1,自引:0,他引:1
Lavanya Bharadwaj Yi Fan Ligong Zhang Dapeng Jiang Linan An § 《Journal of the American Ceramic Society》2004,87(3):483-486
The oxidation behavior of a polymer-derived amorphous silicon carbonitride (SiCN) ceramic was studied at temperature range of 900°–1200°C using fully dense samples, which were obtained using a novel pressure-assisted pyrolysis technique. The oxidation kinetics was investigated by measuring the thickness of oxide layers. The data were found to fit a typical parabolic kinetics. The measured oxidation rate constant and activation energy of the SiCN are close to those of CVD and single-crystal SiC. The results suggest that the oxidation mechanism of the SiCN is the same as that of SiC: oxygen diffusion through a silica layer. 相似文献
20.
Several oxynitride glasses were synthesized with and without the addition of a few weight percent of free silicon. For Mg-Si-0-N and Si-Al-0-N glass compositions, the severe frothing (or "bubbling") which was observed during melting could be eliminated completely by the addition of silicon. In a Y-Si-Al-0-N composition, frothing was not observed, even when no silicon was added. The results are used to explain why A1N is superior to Si3 N4 for synthesizing transparent oxynitride glasses. 相似文献