液相烧结碳化硅晶界内氮化反应的研究

碳化硅 ( Si C)由于其高度的共价键结合特性而具有高硬度、耐磨性和高化学稳定性等优异性能而成为热机、高温环境和化学化工等领域的研究应用对象 .碳化硅材料的无压烧结最早是由 Prochazka[1] 实现的 .2 0世纪 80年代初期 ,Omori[2 ] 通过采用氧化物 ( Al2 O3,Y2 O3和稀土氧化物等 )添加剂的手段大大降低了无压烧结的温度 .这些氧化物具有较低的共熔点 ,在高温下易形成液相 ,从而促进了碳化硅的晶粒重排和晶体生长 .2 0世纪 90年代以来 ,氮化物和氧化物的混合添加剂 (如 Al N- Y2 O3) [3]被广泛应用于碳化硅的液相烧结 .这是因为氮在…     

超低膨胀微晶玻璃应用及发展现状

超低膨胀微晶玻璃是由非晶态无机材料经过严格的受控晶化而得到的以β-石英固溶体为主晶相的一种新型功能材料,具有优异的光学、热学、电学、力学性能,在国民经济各个领域得到广泛应用。本文综述了其应用及发展现状。     

多孔堇青石的制备

以MgO-Al2O3-SiO2系玻璃为前驱体,合成了枝晶形态的堇青石晶体,并通过酸处理成功制备了多孔堇青石.利用DSC分析(Differential Scanning calorimeter, DSC)、X射线衍射分析(X-ray Diffraction Analysis, XRD)、扫描电子显微镜(Scanning Electron Microscope, SEM)、比表面积及孔径分析等测试方法,研究了形核温度对玻璃析晶性能及晶体形貌的影响,同时探讨了氢氟酸刻蚀时间对多孔堇青石比表面积及孔径的影响.结果表明:768 ℃为形成理想枝晶形貌最适合的形核温度;在947～966 ℃晶化处理均可得到高纯度的堇青石晶体;使用5vol;的氢氟酸刻蚀微晶玻璃40 min,获得的多孔堇青石比表面积达到59.4 m2/g,平均孔径10.9 nm.     

Fe2O3对MgO-Al2O3-SiO2系微晶玻璃介电性能的影响

以化学纯试剂为原料采用高温熔融法制备MgO-Al2O3-SiO2 (MAS)系微晶玻璃,利用差热分析仪(DSC)、X射线衍射(XRD)、电子扫描显微镜(SEM)以及介电检测等手段对Fe2O3在MAS系微晶玻璃中介电性能的影响进行探究.结果表明:Fe2O3有降低微晶玻璃核化和晶化温度的作用;随着Fe2O3的加入,试样的主晶相由堇青石向镁铝尖晶石转变,试样的介电常数和介电损耗逐渐减小并且电阻率增高;当Fe2O3的添加量大于6;时,微晶玻璃的介电性能变化不大,趋于稳定.     

硫系发光微晶玻璃研究进展

回顾了近年来关于稀土或过渡金属离子掺杂的硫系发光微晶玻璃的研究进展.深入讨论了稀土离子在硫系微晶玻璃中的微观分布对其发光性能的影响,以及不同稀土离子与晶体场之间相互作用的机制.总结和分析了近两年提出的一种新型硫系微晶玻璃——过渡金属离子激活的硫系微晶玻璃.通过可控晶化和晶体场调控,已经在硫系微晶玻璃实现了较强的Cr2+:1.8～2.8μm以及Co2+:2.5～4.5μm中红外超宽带输出.梳理了影响和制约硫系微晶玻璃在中红外光子器件功能化方面的关键问题,为今后此类研究提供一种思路.     

Controllable synthesis of fullerene nano/microcrystals and their structural transformation induced by high pressure

Fullerene molecules are interesting materials because of their unique structures and properties in mechanical, electrical, magnetic, and optical aspects. Current research is focusing on the construction of well-defined fullerene nano/microcrystals that possess desirable structures and morphologies. Further tuning the intermolecular interaction of the fullerene nano/microcrystals by use of pressure is an efficient way to modify their structures and properties, such as creation of nanoscale polymer structures and new hybrid materials, which expands the potential of such nanoscale materials for di- rect device components. In this paper, we review our recent progress in the construction of fullerene nanostructures and their structural transformation induced by high pressure. Fullerene nano/microcrystals with controllable size, morphology and structure have been synthesized through the self-assembly of fullerene molecules by a solvent-assisted method. By virtue of high pressure, the structures, components, and intermolecular interactions of the assemblied fullerene nano/microcrystals can be finely tuned, thereby modifying the optical and electronic properties of the nanostructures. Several examples on high pressure induced novel structural phase transition in typical fullerene nanocrystals with C60 or C70 cage serving as build- ing blocks are presented, including high pressure induced amorphization of the nanocrystals and their bulk moduli, high pressure and high temperature （HPHT） induced polymerization in C60 nanocrystals, pressure tuned reversible polymeriza- tion in ferrocene-doped C60/C70 single crystal, as well as unique long-range ordered crystal with amorphous nanoclusters serving as building blocks in solvated C60 crystals, which brings new physical insight into the understanding of order and disorder concept and new approaches to the design of superhard carbon materials. The nanosize and morphology effects on the transformations of fullerene nanocrystals have also been discussed. These results provide the foundation for the fabrication of pre-designed and controllable geometries, which is critical in fullerenes and relevant materials for designing nanometer-scale electronic, optical, and other devices.     

微晶三苯甲烷分离富集和测定痕量镉

镉是一种广泛分布于环境中并严重危及生物体健康的有毒重金属元素之一[1].但由于环境水样中Cd(II)的含量低而难于直接测定.浊点萃取法[2]、液膜法[3]及固相萃取法[4]等被用来分离富集Cd(II).但这些方法不能直接用于大体积(如1L)水样中痕量金属离子的分离与富集,且萃取相 (浊点相[2],有机膜相[3],固相萃取剂[4])的制备程序较为复杂.本文建立了负载氯化十四烷基二甲基苄基铵(Zeph)的微晶三苯甲烷分离富集痕量Cd(II)的新方法.     

S/Cd物质的量比对微波水热制备CdS微晶的形貌影响及光学性能研究

采用微波水热法,以CdCl2·H2O和Na2S2O3·5H2O为镉源和硫源,在不同的S/Cd物质的量比条件下合成了CdS微晶。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、场发射扫描电子显微镜(FE-SEM)、EDS、透射电子显微镜(TEM)等对样品的物相、形貌和元素组分进行了分析。结果表明:随着S/Cd物质的量比的增大,产物CdS的形貌发生规律性变化,由四面体结构逐渐转变为准球形结构;准球形结构具有分级结构,是由更小的纳米晶组装而成;光致发光性质研究结果表明,所得的CdS微晶具有较好的蓝光发射性能。     

含磷酸盐Fe（Ⅲ）水溶液的水解动力学研究

本文研究了Ｆｅ（ＮＯ３）３－ＮａＨ２ＰＯ４体系水解合成纺锤形α－Ｆｅ２Ｏ３⒕У亩ρЧ獭?