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稀土草酸盐先驱体法制备LaPO_4:Ce,Tb绿色荧光粉 总被引:1,自引:0,他引:1
采用稀土草酸盐先驱体法制各了LaPO4:Ce,Tb绿色荧光粉.借助X射线衍射(XRD)、扫描电镜(SEM)、比表面仪及荧光分光光度计研究了荧光粉的制备过程,并对其晶体结构、表观形貌、粒径、比表面积、孔径分布、发光特性等进行分析和表征.结果表明:先驱体在900℃还原气氛下煅烧,制备的产物属于正磷酸盐的单斜晶系,独居石结构.颗粒形状接近球形,粒径分布在lOo~150nm.比表面积为7.3 m2/g,孔径分布较宽.同时,在286 nm紫外光激发下发绿光,发射主峰位于543 nm,对应于Tb3+的5D4→7F5跃迁发射. 相似文献
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三维形貌ZnO一维纳米结构的微波水热合成、机理及性能研究 总被引:1,自引:0,他引:1
以Zn(NO3)2·6H2O和NaOH为原料,采用微波水热法成功合成了具有三维形貌的单晶ZnO一维纳米结构。采用XRD、SEM及紫外-可见光谱分析等手段对ZnO纳米结构及性能进行了表征;探讨了ZnO复杂纳米结构的形成机理。结果表明:在不同工艺条件下可分别合成ZnO纳米棒、纳米线、纳米推进器、纳米蒲公英及纳米纺锤等结构;微波在合成复杂ZnO纳米结构中起非常重要的作用;纳米ZnO紫外-可见光谱吸收带边出现红移现象。该法没有引入任何金属催化剂、模板或者表面活性剂,从而避免了去除残余添加剂的后续复杂工序。另外,与传统水热法相比,该法可以显著减少反应时间和降低反应温度。 相似文献
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电磁搅拌技术是最早应用于制备半固态坯料的方法之一,然而集肤效应限制了该技术的进一步发展。提出环缝式电磁搅拌技术旨在破解这一难题。与普通电磁搅拌相比,环缝能避开磁场较低的部分,在环缝内形成的均匀旋转磁场,可以获得均匀的温度场和均匀凝固的细小组织。环缝式电磁搅拌连铸坯组织呈蔷薇状,在铸坯中分布均匀。与普通电磁搅拌相比,环缝式电磁搅拌技术能明显降低宏观偏析和显微偏析。 相似文献
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长期处于户外的输电杆塔容易遭受锈蚀而受损,传统的涂料涂覆处理无法起到同时除锈和防腐的作用,因此亟须探索一种适合输电杆塔的绿色磷化处理工艺。基于电化学与响应面分析法,以磷酸与氧化锌为基础磷化液,研究植酸、复合钝化剂BM1、硝酸锰三种促进剂的浓度对锌系磷化膜成膜质量的影响,以硫酸铜点滴时间评判其耐蚀性。采用扫描电子显微镜观察添加不同促进剂的磷化液所形成磷化膜的表面形貌。通过响应面分析法对磷化液的成膜耐腐蚀效果进行优化,得到硫酸铜点滴时间的二次响应方程。各因素影响次序为硝酸锌>复合钝化剂(BM1)>植酸>硝酸锰,通过优化获得硫酸铜点滴时间为101 s的磷化液配方,即氧化锌15 g/L、磷酸100 g/L、复合钝化剂BM1 1.7 g/L、植酸11.7 mL/L、硝酸锌52.4 g/L、硝酸锰5.9 g/L、OP-10乳化剂适量。通过响应面优化参数得到的磷化液配方在具有除锈功能的同时能有效提高Q235低碳钢的耐腐蚀性能,可为磷化液新配方的性能预测和浓度优化提供方法与理论指导。 相似文献
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Composite coatings containing Cu, Co, Ni, and samaria-doped ceria (SDC) have been fabricated using a novel hybrid atmospheric plasma spraying technique, in which a multi-component aqueous suspension of CuO, Co3O4, and NiO was injected axially simultaneously with SDC injected radially in a dry powder form. Coatings were characterized for their microstructure, permeability, porosity, and composition over a range of plasma spray conditions. Deposition efficiency of the metal oxides and SDC was also estimated. Depending on the conditions, coatings displayed either layering or high levels of mixing between the SDC and metal phases. The deposition efficiencies of both feedstock types were strongly dependent on the nozzle diameter. Plasma-sprayed metal-supported solid oxide fuel cells utilizing anodes fabricated with this technique demonstrated power densities at 0.7 V as high as 366 and 113 mW/cm2 in humidified hydrogen and methane, respectively, at 800 °C. 相似文献
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采用升华硫与多壁碳纳米管在一定条件下合成了一种新型纳米含硫复合材料。通过扫描电子显微镜(SEM)和BET比表面积等分析测试手段对复合材料的物理化学性能进行表征,利用循环伏安、交流阻抗和电池充放电对材料的电化学性能进行了测试。结果表明:此复合材料表现出了很好的电化学性能,其初始放电比容量达700mAh/g,在室温下经过60次循环之后电池放电比容量仍稳定在464mAh/g,容量保持率大于66%。 相似文献
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合成了两种咪唑啉型双子表面活性剂二(2-十一(十七)烷基-1-甲酰胺乙基咪唑啉)己二胺季铵盐(SUAEIHDI、SHAEIHDI),并进行了红外表征;然后以Zn(Ac)2-2H20为锌源,硒粉为硒源,水合肼为还原剂,SUAEIHDI为表面修饰剂,采用水热法于150℃反应24h,制得球形ZnSe纳米材料,用TEM、SEM、IR、UV-vis和XRD等手段对ZnSe纳米材料进行了表征,并对球形ZnSe的形成机理进行了初步探讨。结果表明:该咪唑啉型双子表面活性剂对于纳米材料具有良好的形貌控制作用和表面修饰作用。 相似文献
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Application of Thermodynamic Models for Better Understanding and Optimizing the Hall–Heroult Process
Pascal Coursol Gilles Dufour Jules Coté Patrice Chartrand Phillip Mackey 《JOM Journal of the Minerals, Metals and Materials Society》2012,64(11):1326-1333
During the last decade, important improvements have been made in the application of thermodynamic models for studying the molten cryolite system used in the Hall?CHeroult process. This approach allows a better understanding and paves the way for furthering developments in bath chemistry and molten metal processing. In this article, thermodynamic modeling is used to explore the operating windows in the reduction of alumina in molten cryolite. The impact of a range of concentrations of AlF3, CaF2, and Al2O3 in conventional or ??lithium-free?? baths is also discussed. Subsequently, the model was also used to evaluate the impact of additions of lithium fluoride to the bath. Conditions allowing an operation at lower cell voltages and lower bath temperatures were identified. The modeling approach described in this article is considered as an important innovation to revisit fundamentals, to constantly re-examine paradigms, and to identify potential modifications?in bath chemistry for improving energy efficiency and productivity of modern prebaked Hall?CHeroult cells. 相似文献