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以稻壳为原料的国产BP-SiCw的生长机理为一维的VLS生长。BP-SiCw的直径变化规律遵守晶体一维VLS生长的直径变化规律。即:炉子加热功率的波动越大,晶段表面的粗糙现象越严重。保护气的热容量越大,和炉体进行的热交换量越多,生产出的BP-SiCw的直径也越粗。氢气氛下生产的BP-SiCw表面光洁度优于氩气氛下生产的BP-SiCw产品。 相似文献
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以稻壳为原料的国产BP-SiCw的生长机理为一维的VLS生长。BP-SiCw的直径变化规律遵守晶体一维VLD生长的直径变化规律。即:炉子加热功率的波动越大,晶须表面的粗糙现象越严重。保护气的热容量越大,和炉体进行的热交换量越多,生产出的BP-SiCw的直径也越粗。氢气氛下生产的BP-SiCw表面光洁度优于氩气氛下生产的BP-SiCw产品。 相似文献
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SiO2/C体系在氮气气氛下1573~1973K温度范围内反应所得的产物为α、β-SiC。高的反应温度、高的升温速率以及原料碳的过量均有利于SiC的生成。反应过程可分为三个阶段,产物分别为SiO气体,Si3N4和SiC,表现活化能分别为470kJ/mol,467kJ/mol和484kJ/mol。以非等温热重分析为主要实验方法,对SiO2/C体系在流动的氮气中的反应机理进行了研究,探讨了体系固相反应所经历的步骤,确定了控速环节和动力学参数。 相似文献
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通过SEM观察和EDXA分析对Al2O3/SiC和SiCw/SiC陶瓷的耐磨粒磨损性进行了比较研究。在低应力下,Al2O3/SiC陶瓷的耐磨性优于SiCw/SiC陶瓷,而在较高应力下则相反。 相似文献
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稻壳SiC晶须生长工艺和机理研究 总被引:2,自引:0,他引:2
在以稻壳为原料,氧化物类作催化剂反应生成SiC晶须的过程中,催化剂的主要作用是形成液相,晶须生长方式以VLS为主,同时料内有少量VS方式生长的晶须,料表面有少量CVD方式生长的晶须。 相似文献
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SiC(w)/TZP+mullite陶瓷复合材料界面和组成设计与力学性能 总被引:2,自引:1,他引:1
本文从理论上分析了SiC(w)TZP+mullite(p)复合材料界面残余热应力及其在基质内的分布规律。提出在SiC(w)表面涂复Al2O3和在PZT中加入mullite(p)联合作用来降低晶须/基质界面残余热应力的界面设计方案,导出SiC(w)和mullite(p)协同补强PZT的匹配条件。制备了SiC(w)/TZP+mullite(p)复合材料并了SiC(w)表面涂层Al2O3厚度和SiC(w 相似文献
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SiC晶须增韧Al2O3及ZrO2(Y2O3)基陶瓷复合材料的抗热震行为 总被引:3,自引:0,他引:3
采用三点弯曲及扫描电镜等方法研究了SiCw/Al2O3,SiCw/ZrO2)及SiCw/Al2O3+ZrO2(Y2O3)陶瓷复合材料的抗热震性。结果表明SiCw的加入使Al2O3,ZrO2(Y2O3)以及Al2O3+ZrO2(Y2O3)基体的抗热震性显著提高,Al2O3陶瓷基复合材料的抗热震性明显优于ZrO2(Y2O3)陶瓷基复合材料。同时发现在Al2O3+SiCw材料基础上再加入少量ZrO292 相似文献
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采用三点弯曲及扫描电镜等方法研究了SiCw/Al2O3、SiCw/ZrO3(Y2O3)及SiCw/Al2O3+ZrO2(Y2O3)陶瓷复合材料的抗热震性.结果表现SiCw的加入使Al2O3、ZrO2(Y2O3)以及Al2O3+ZrO2(Y2O3)基体的抗热震性显著提高,Al2O3陶瓷基复合材料的抗热震性明显优于ZrO2(Y2O3)陶瓷基复复合材料.同时发现在Al2O3十SiCw材料基础上再加入少量ZrO2(2Y)颗粒(10Vo1%),也可进一步提高Al2O3+SiCw材料的抗热震性. 相似文献
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介绍了SiC晶须增韧陶瓷基复合材料的烧结合成方法,将各动力学因素(晶须含量、混合工艺和烧结温度)对热压烧结法制备SiC晶须增韧陶瓷基复合材料的影响进行了详细阐述,叙述并讨论了SiC晶须增韧的不同机理,并展望了该领域的研究方向。 相似文献
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以无机硅溶胶和炭黑为原料,采用溶胶-凝胶方法和碳热还原反应进行了合成碳化硅晶须的试验.通过对溶胶-凝胶处理过程采用不同的工艺方法,比较了不同颗粒直径和堆积密度的反应粉末对合成产物中碳化硅晶须形貌和产率的影响.结果表明:采用氨解硅溶胶方法制得的原料粉末比直接溶胶-凝胶方法制得的粉末颗粒直径细小,团聚松散,堆积密度小.在同样合成条件下前者反应获得的碳化硅的转化率高,晶须含量高,质量好. 相似文献
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《Advanced Powder Technology》2014,25(2):654-658
Rice hulls were used as raw material to produce Si3N4 by conventional and microwave carbothermal reduction and nitridation. The precursor was made by the digestion of rice hulls with 12 M HNO3, followed by pyrolisis of digested hulls to reduce the organic carbon. The precursor was then pelletized and reacted in conventional and microwave furnaces. The intimate of SiO2 and carbon mixture favored the complete formation of Si3N4 in conventional reaction. However, SiC residual phase was present in the product of microwave reaction probably owing to the rapid temperature increasing of the reaction, caused by the thermal runaway effect of alumina pipe reactor. 相似文献
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实验以高含氢硅油(H-PSO)为原料, 在石墨材料表面制备SiC晶须, 利用“正交试验法”以结晶率为指标, 研究热处理温度(T)、保温时间(t)、保护性气氛流量(f)和基体孔隙率(P)这四个因素对SiC晶须生成的影响。通过扫描电镜、透射电镜、拉曼光谱及X射线衍射等测试手段, 分析了SiC晶须形貌及结构特点。实验结果表明, 热处理温度是影响SiC晶须生成最重要的因素, 其影响程度远远大于其他参数, 其次是气流量、孔隙率和保温时间。安全流量范围内, 较高的气流量使SiC晶须生成反应充分进行; 较小的孔隙率有利于SiC晶核的长大; 高的热处理温度及长的保温时间能促进SiC晶须的继续生长。SiC晶须是以SiC晶相为核, 以硅的氧化物为壳的核壳结构。 相似文献
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The synthesis of SiC (both powder and whiskers) was carried out from rice husks with and without the use of catalysts (iron, cobalt and nickel). The introduction of the catalyst increased the reaction rate, the yield becoming up to three times that for the uncatalysed reaction, and increased the proportion of -phase from 95% to 99%. The general behaviour of the three catalysts was very similar, although nickel was the most effective from the point of view of reaction rate, and cobalt in producing larger crystal size. Analysis of the evolution of reaction rate, morphology of the whisker formed, evolution of gases during reaction, crystal size and intermetallic phases, led to a reaction mechanism based on the formation of an M-Si-C liquid phase which is essential for the nucleation and growth of the SiC whiskers. 相似文献
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Studies have been made on the conversion of burnt rice husks to SiC over a wide temperature range. Four distinct processes (crystallization of silica and carbon, formation of SiC whiskers and particles) have been identified as occurring during the pyrolysis of burnt rice husks. The dependence of relative rates of these four reactions on the temperature has been ascertained through detailed X-ray diffraction, scanning electron microscopy, chemical analysis and macro structural study. It was also revealed that a multistep pyrolysis to 1310°C yields a higher SiC(w) than the single step pyrolysis. The yield of SiC(w) from burnt rice husks has been found to be lower than that from raw rice husks. A correlation between the amount of SiC(w) formed and the appearance of pyrolysed rice husks has been identified. 相似文献