Processing of alumina and zirconia nano-powders and compacts

Magnesia–doped alumina and yttria–doped zirconia nano-powders were synthesized using sucrose as a chelating agent and template material from the aqueous solutions of aluminium nitrate, magnesium nitrate, ytrrium nitrate and zirconyl nitrate, respectively. Synthesis parameters were optimized with varying sucrose to metal ion ratio, calcinations time, and temperature to produce these nano-powders. As-synthesized powders were characterized by room temperature X-ray diffraction, BET surface area analyzer and transmission electron microscopy. Y₂O₃–ZrO₂ nano-powders had particle size in the range of 80–200 nm with specific average surface area of 119 m²/g and for MgO–Al₂O₃ powders, particle sizes were 30–200 nm with the specific average surface area of 250 m²/g. Our results indicate that this synthesis method is a versatile one and can be applied to a variety of oxide-based materials to form nano-powders. Nano-powders were compacted uniaxially and densified in a muffle furnace. Sintered discs were used for hardness testing and density measurements, as well as for microstructural characterization.     

纳米镍粉的形貌与磁性能

采用多元醇液相还原法,在乙二醇中还原制备出了球形、刺球形、线形、花状4种形貌的镍纳米材料.通过XRD和FESEM对镍粉的结构、形貌进行了分析,并用振动样品磁强计对不同形貌的纳米镍粉进行了磁性能分析.结果表明所制备的纳米镍粉为面心立方的单晶结构,晶粒尺寸在10～30nm之间,颗粒直径在200～300nm之间,主要为球形、刺球形、线形、花状4种形貌.线形纳米镍粉的矫顽力最高,刺球形和花状次之,球形的矫顽力最小.     

Effect of Sulfate Ions on YAG Powders Synthesized by Microwave Homogeneous Precipitation

Using Al(NO3)3·9H2O, NH4Al(SO4)2·12H2O, Y(NO3)3 as mother salts, and urea as precipitant, YAG nano-powders were synthesized by microwave homogeneous precipitation. The composition, morphology, and phase transformation of precursor were analyzed by IR, XRD and TEM. The size distribution of YAG powders was characterized using laser diffraction method. The results show that sulfate ions influence the dispersion, composition and morphology of the YAG precursors. The addition of moderate sulfate ions can produce YAG powders with nano size and excellent dispersion at 1100 ℃.     

Research on preparation optimization of nano CeB6 powder and its high temperature stability

High temperature self-propagating synthesis (SHS) process is very rapid, the reaction process becomes un-controlled after the SHS reaction is ignited. So the initial reaction conditions will have great effects on phase compositions and microstructures of reaction products. In this paper, the effects of the proportioning amount of Mg on the yield ratio and particle sizes of CeB6 were studied. The SHS reaction products and leached products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the SHS products consisted of MgO, CeB6 and little Mg3B2O6. The single CeB6 phase was contained after the SHS reaction products were leached. The purity of CeB6 was higher than 99.0 mass%, and the minimum particle sizes of CeB6 were within 30-70 nm. When the proportioning amount of Mg was 25% more than the theoretic amount, the yield of CeB?6 was 68.68%. The antioxidant ability of CeB6 was rather stronger, which was oxidized step by step, and the initial oxidation temperature was 750 oC, which indicated that it had good high temperature stability. The apparent activation energies of oxidation reactions of CeB6 were 200.09 and 312.10 kJ/mol, respectively, and reaction orders were 0.69 and 0.40, respectively.     

掺杂镧BaTiO_3基超细微粉的制备及表征

以钛酸四丁脂、醋酸钡、醋酸镧为原料 ,采用溶胶 -凝胶法制备了掺杂镧BaTiO3 基超细微粉 ,利用DTA、XRD、SEM等测试手段对超细微粉进行了表征。根据Scherrer计算可知 ,超细微粉的粒径在40nm左右     

反相微乳液碳吸附耦合法制备氧化钇稳定四方氧化锆纳米粉体及表征

采用反相微乳液和碳吸附法制备了氧化钇稳定四方氧化锆纳米粉体,探讨了碳黑的加入量对粉体比表面积的影响,得到最佳的碳黑量。分别采用XRD、TEM、BET和TG分析了不同温度下煅烧所得粉体的物相、颗粒度和比表面积以及前驱体热分解特性。实验结果表明,经700℃焙烧后制得了分散性好的四方相ZrO2纳米粉体,比表面积为97.4m2/g,平均粒径为9nm。     

改性纳米SiC粉体强韧化ZGMn13组织及性能的研究

在生产条件下采用冲入法制备了改性纳米SiC粉体强韧化ZGMn13耐磨材料,研究了SiC粉体对ZGMn13显微组织和力学性能的影响。结果表明：经表面活性处理的纳米SiC粉体能够明显改善高锰钢凝固组织。经水韧处理后,组织更加细小,碳化物基本固溶到基体中。在本实验研究范围内,随着SiC加入量增加,力学性能也不断提高,其强化机理主要是细晶强化和第二相粒子弥散强化的综合作用。当纳米SiC粉体加入量为0.1%时,抗拉强度、硬度和韧性最优,分别提高了8.2%、19%和22%。     

燃烧法制备ZnO纳米粉体及Pr系ZnO压敏陶瓷

以Zn（NO32）和NH2CONH2为原料,通过燃烧法合成纳米ZnO粉体。用X射线衍射、扫描电镜、比表面积分析手段对所制备粉体的性能进行了表征。结果表明,制备的纳米氧化锌为纯相六角纤锌矿结构。在三种反应模式中,当φ=0.85（贫燃比,SCS）时,晶粒尺寸为41.5nm,其比表面积为0.849m2/g;当φ=1.67（化学计量比,VCS）时,晶粒尺寸为36.6nm,其比表面积为0.516m2/g;当φ=2.8（富燃比,SHS）时,晶粒尺寸为30.5nm,其比表面积为4.068m2/g。燃烧法制备的Pr系ZnO压敏陶瓷在1250℃烧结2h后,其电性能优异,晶粒尺寸约为3.5μm,压敏电压（VlmA     

反应条件对共沉淀法制备纳米钛酸钡粉体的影响

以钛酸四丁酯、草酸、草酸钠和醋酸钡为原料,采用共沉淀法制备了纳米钛酸钡粉体。通过XRD、IR和TG等检测手段,研究pH值和煅烧温度对粉体纯度的影响。结果表明,制备的前驱体为钛钡混合草酸盐沉淀。pH在3~6的范围内,随着pH值的提高,粉体的纯度下降,粒径减小。随着煅烧温度的升高,粉体的纯度提高。煅烧温度太高,钛酸钡易从立方相转变为四方相。最佳实验条件为pH=3.14,煅烧温度900℃。在此实验条件下,成功制备出均匀的粒径尺寸为37.2nm的纯相纳米钛酸钡粉体。     

化学共沉淀法制备纳米铋掺杂氧化锡的影响因素研究

以SnCl4.5H2O和Bi(NO3)3.5H2O为原料,氨水为沉淀剂,采用化学共沉淀法制备了铋掺杂氧化锡（BTO）纳米粉体,研究了反应温度、滴定终点pH值、铋掺杂量,煅烧温度和分散剂PEG-600对所得的纳米BTO粉体物相、晶粒度和形貌的影响,对粉末的前驱体进行综合热分析（TG-DTA）,用X-射线衍射（XRD）,扫描电镜(SEM)对产物的结构和形貌进行表征,得到共沉淀法制备纳米BTO粉体的最佳条件：反应温度60℃,滴定终点pH值为3,煅烧温度600℃;该条件下制得BTO粉体的电阻率最小为3.48Ω•cm。