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镍增强钨丝的晶粒长大机制
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作者 Moon.,IH 钟培全 《钨钼材料》 1994年第3期53-60,共8页
关键词 钨丝 晶粒长大机制 烧结 灯泡
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亚微米球形镍粉的两步法可控制备与表征 被引量:1
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作者 邹俭鹏 杨洪志 刘如铁 《稀有金属材料与工程》 SCIE EI CAS CSCD 北大核心 2018年第9期2847-2851,共5页
以H_2C_2O_4·2H_2O为沉淀剂,NiSO_4·6H_2O为镍源,第1步通过共沉淀法制得NiC2O4前驱体粉末;然后在H_2气氛、中温条件下(250~500℃)煅烧还原,第2步制得高规则度的亚微米球形镍粉。采用扫描电子显微镜、X射线衍射、激光粒度分析... 以H_2C_2O_4·2H_2O为沉淀剂,NiSO_4·6H_2O为镍源,第1步通过共沉淀法制得NiC2O4前驱体粉末;然后在H_2气氛、中温条件下(250~500℃)煅烧还原,第2步制得高规则度的亚微米球形镍粉。采用扫描电子显微镜、X射线衍射、激光粒度分析等检测手段对所制备的样品形貌、显微结构进行表征。结果表明:亚微米球形镍粉纯度高,二次颗粒粒径约为40μm,由大量大小均匀、分散性好的粒径0.5μm左右的一次颗粒团聚而成,这种结构保证了镍粉具有良好的成形性和烧结活性。随煅烧温度的升高,结晶度逐渐升高;亚微米球形镍粉的最佳制备工艺参数为:镍离子浓度0.7mol·L^(-1),反应温度40℃和煅烧温度500℃。镍粉的晶粒长大活化能为26.9kJ·mol^(-1),其晶粒长大机制为界面扩散控制机制。 展开更多
关键词 两步法 显微结构 亚微米 球形镍粉 晶粒长大机制
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Microstructural evolution and mechanism of grain growth in magnesia ceramics prepared by high pressure and temperature with ultra-high heating rate 被引量:3
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作者 LIU JiangHao FU ZhengYi +5 位作者 WANG WeiMin ZHANG JinYong WANG Hao WANG YuCheng LEE SooWohn NIIHARA Koichi 《Science China(Technological Sciences)》 SCIE EI CAS 2014年第6期1085-1092,共8页
The fast densification method of combustion reaction plus quick pressing was adopted to prepare nanocrystalline ceramics.The densification process of magnesia compact with a particle size of 100 nm was investigated,un... The fast densification method of combustion reaction plus quick pressing was adopted to prepare nanocrystalline ceramics.The densification process of magnesia compact with a particle size of 100 nm was investigated,under the applied pressure of up to 170 MPa,and the temperature range of 1740–2080 K with ultra-high heating rate(above 1700 K/min).High-purity magnesia ceramics with a relative density of 98.8%and an average grain size of 120 nm was obtained at 1740 K,and the grain growth during the densification process was effectively restrained.The characteristic morphology of evaporation-condensation was observed in the compact prepared at 2080 K,which revealed the actual process of mass transfer by gas diffusion.Moreover,the investigation on the microstructure evolution and mechanism of grain growth was carried out,on the basis of as-preserved nanocrystalline ceramics.The result indicated that the grain growth of the nanocrystalline MgO was controlled by the mechanism of evaporation-condensation rather than surface diffusion.Furthermore,the pressure had an influence of restraining the grain growth based on solid diffusion and strengthening the effect of gas diffusion with the increasing temperature.Under the particular conditions,there existed an appropriate temperature for the densification of nanocrystalline magnesia,while the excessive temperature would exaggerate grain growth and impede densification. 展开更多
关键词 grain growth DENSIFICATION heating rate evaporation-condensation surface diffusion nanocrystalline ceramics
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