共查询到19条相似文献,搜索用时 171 毫秒
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纳米SiC—Si3N4复合粉体的制备及研究 总被引:5,自引:0,他引:5
本文以炭黑和气凝氧化硅为原料,采用碳热还原氮化的方法制备纳米SiC-Si3N4复合粉体;复合粉中SiC的含量由起始粉中C:SiO2的摩尔比控制。在复合粉体的表征中用XRD线宽法测量SiC粒径大小。TEM照片显示Si3N4粒径在100 ̄200nm;SiC为纳米级。文中还对生成复合粉体的反应机理进行了探讨。同时利用这一工艺制备出单相的Si3N4粉和SiC粉。 相似文献
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SiO2—C—N2系统中气相对相稳定的影响 总被引:2,自引:0,他引:2
研究了SiO2-C-N2系统中一定N2分压下,温度与O2、SiO、CO气体分压对相稳定性的影响,绘制了平衡状态下的相稳定性关系图,并以此指导碳热还原氮化法合成高纯Si3N4粉的工艺制备条件。 相似文献
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化学气相淀积制备Si3N4超细粉末 总被引:3,自引:0,他引:3
本文研究了SiCl4-NH3-N2-H2系统平衡热力学,确定了Si3N4合成的最佳热力学条件。采用电阻炉化学气相淀积法制备了Si3N4超细粉末,并考察了工艺条件对颗粒形貌的影响。 相似文献
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多孔氮化硅表面封孔增强涂层研究 总被引:5,自引:0,他引:5
以CaO-SiO2-B2O3体系作为α-Si3N4的结合剂和助烧剂,采用溶胶-凝胶法在多孔氮化硅表面制备了防潮增强涂层.采用X射线衍射(XRD)方法对涂层进行了相结构分析;用扫描电子显微镜(SEM)观察了涂层的微观形貌;用阿基米德法测量了封孔前后基体的密度、吸水率和显气孔率;分别在SANS电子式材料实验机和1MHz LCR测试仪上测量了封孔前后材料的抗弯强度、介电常数和介电损耗.结果表明:封孔防潮处理使基体吸水率下降了90.99%~96.97%,强度提高了9%~22%,而对多孔体的密度、介电常数和介电损耗影响很小. 相似文献
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Large-scale ear-like Si3N4 dendrites were prepared by the reaction of SiO2/Fe composites and Si powders in N2 atmosphere. The product was characterized by field emission scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The results reveal that the product mainly consists of ear-like Si3N4 dendrites with crystal structures, which have a length of several microns and a diameter of 100-200 nm. Nanosized ladder-like Si3N4 was also obtained when changing the Fe content in the SiO2/Fe composites. The Si3N4 nanoladders have a length of hundreds nanometers to several microns and a width of 100-300 nm. The ear-like Si3N4 dendrites are formed from a two-step growth process, the formation of inner stem structures followed by the epitaxial growth of secondary branches. 相似文献
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A wet chemical technique was used to prepare Na1+xZr2SixP3?xO12. The precursor was prepared using a finely divided silica sol and a fine zirconia slurry mixed with a solution of sodium carbonate and ammonium dihydrogen phosphate. The mixture was dried by flash evaporation and then calcined at 750°C. The effect of sintering conditions and atmosphere on density and phase formation in the system was examined. Single phase material was obtained by controlling the soda loss during processing. 相似文献
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Porous silicon nitride/silicon oxynitride composite ceramics were fabricated by silica sol infiltration of aqueous gelcasting prefabricated Si3N4 green compact. Silica was introduced by infiltration to increase the green density of specimens, so suitable properties with low shrinkage of ceramics were achieved during sintering at low temperature. Si2N2O was formed through reaction between Si3N4 and silica sol at a temperature above 1550 °C. Si3N4/Si2N2O composite ceramics with a low linear shrinkage of 1.3–5.7%, a superior strength of 95–180 MPa and a moderate dielectric constant of 4.0–5.0 (at 21–39 GHz) were obtained by varying infiltration cycle and sintering temperature. 相似文献
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J. Zhang X.M. Zhang Y. Zhou M. Naka Atroshenko Svetlana 《Materials Science and Engineering: A》2008,495(1-2):271
In this study, Si3N4 ceramic was jointed by a brazing technique with a Cu–Zn–Ti filler alloy. The interfacial microstructure between Si3N4 ceramic and filler alloy in the Si3N4/Si3N4 joint was observed and analyzed by using electron-probe microanalysis, X-ray diffraction and transmission electron microscopy. The results indicate that there are two reaction layers at the ceramic/filler interface in the joint, which was obtained by brazing at a temperature and holding time of 1223 K and 15 min, respectively. The layer nearby the Si3N4 ceramic is a TiN layer with an average grain size of 100 nm, and the layer nearby the filler alloy is a Ti5Si3Nx layer with an average grain size of 1–2 μm. Thickness of the TiN and Ti5Si3Nx layers is about 1 μm and 10 μm, respectively. The formation mechanism of the reaction layers was discussed. A model showing the microstructure from Si3N4 ceramic to filler alloy in the Si3N4/Si3N4 joint was provided as: Si3N4 ceramic/TiN reaction layer/Ti5Si3Nx reaction layer/Cu–Zn solution. 相似文献