排序方式: 共有62条查询结果,搜索用时 203 毫秒
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高质量AlPO4-5分子筛大单晶的合成与表征 总被引:2,自引:0,他引:2
以拟薄水铝石作为铝源,正磷酸为磷源,正三丙胺(TPA)作模板剂,采用水热法合成了AlPO4 5分子筛.在不同的反应物配比、温度以及晶化时间条件下,得到了不同尺寸的AlPO4 5分子筛单晶.实验表明,反应物质的摩尔比为Al2O3∶P2O5∶TPA∶C2H5OH∶H2O∶HF=1∶1. 2∶2. 66∶80∶1000∶0. 7,反应温度为457K,晶化时间48h是生成六方AlPO4 5分子筛大单晶较适宜的条件;在该反应条件下合成出纵向尺度最大达到2. 0mm、具有完整六方棱柱形态的AlPO4 5分子筛单晶;部分晶体的横向尺度达到0. 31mm.用扫描电镜观察晶体的形貌;AlPO4 5分子筛晶体结构通过SMART1000单晶衍射仪鉴定. 相似文献
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临界电流密度Jc是超导薄膜的一个重要参量,它可以衡量超导薄膜的功率承载能力。大面积高温超导薄膜制成后,其Jc需要被无损精确测量。文中提出了一种新的交流磁场下的高温超导薄膜临界态模型:(1)基于此模型对薄膜的临界电流密度进行了精确无损测量;(2)并将实验测量的三次谐波电压曲线进行拟合研究。首先,根据麦克斯韦方程和伦敦方程,计算外加直流磁场超导薄膜Meissner态下电流和磁场在薄膜内的分布;然后分析薄膜进入临界态后内部电流的变化,在考虑顶扎力作用的情况下,提出了临界态电流和磁场非均匀分布模型;最后根据其模型,推导出三次谐波电压的表达式。为了验证该理论,分别对四片超导薄膜在不同频率下进行了三次谐波和临界电流密度测量。实验结果表明:三次谐波电压的理论与实验曲线一致;与四点传输法的测量结果相比较,该方法测量超导薄膜临界电流密度的误差在5%左右,具有高精度、无损伤、方便快捷等优点。 相似文献
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以拟薄水铝石作为铝源,正磷酸为磷源,正三丙胺(TPA)作模板剂,采用水热法合成了AIPO4-5分子筛.在不同的反应物配比、温度以及晶化时间条件下,得到了不同尺寸的AIPO4-5分子筛单晶.实验表明,反应物质的摩尔比为Al2O3:P2O5:TPA:C2H5OH:H2O:HF=1:1.2:2.66:80:1000:0.7,反应温度为457K,晶化时间48h是生成六方AIPO4-5分子筛大单晶较适宜的条件;在该反应条件下合成出纵向尺度最大达到2.0mm、具有完整六方棱柱形态的MPO4-5分子筛单晶;部分晶体的横向尺度达到0.31mm.用扫描电镜观察晶体的形貌:AlPO4-5分子筛晶体结构通过SMART1000单晶衍射仪鉴定. 相似文献
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Self-assembly of lamella-forming diblock copolymers confined in nanochannels: Effect of confinement geometry 下载免费PDF全文
The self-assembly of symmetric diblock copolymers confined in the channels of variously shaped cross sections(regular triangles, squares, and ellipses) is investigated using a simulated annealing technique. In the bulk, the studied symmetric diblock copolymers form a lamellar structure with period LL. The geometry and surface property of the confining channels have a large effect on the self-assembled structures and the orientation of the lamellar structures. Stacked perpendicular lamellae with period LLare observed for neutral surfaces regardless of the channel shape and size, but each lamella is in the shape of the corresponding channel’s cross section. In the case of triangle-shaped cross sections, stacked parallel lamellae are the majority morphologies for weakly selective surfaces, while morphologies including a triangular-prism-shaped B-cylinder and multiple tridentate lamellae are obtained for strongly selective surfaces. In the cases of square-shaped and ellipse-shaped cross sections, concentric lamellae are the signature morphology for strongly selective surfaces, whereas for weakly selective surfaces, stacked parallel lamellae, and several types of folding lamellae are obtained in the case of square-shaped cross sections, and stacked parallel lamellae are the majority morphologies in the case of ellipse-shaped cross sections when the length of the minor axis is commensurate with the bulk lamellar period. The mean-square endto-end distance, the average contact number between different species and the surface concentration of the A-monomers are computed to elucidate the mechanisms of the formation of the different morphologies. It is found that the resulting morphology is a consequence of competition among the chain stretching, interfacial energy, and surface energy. Our results suggest that the self-assembled morphology and the orientation of lamellae can be manipulated by the shape, the size, and the surface property of the confining channels. 相似文献
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采用三维键涨落模型(BFM)的Monte Carlo计算机模拟方法,模拟了两种分别具有高取向和低取向链微观结构的拉伸取向聚合物2H NMR谱. 讨论了排除体积效应与链的均方末端距分布对2H NMR谱线的影响. 结果表明,排除体积效应对高取向和低取向聚合物2H谱劈裂的影响是不同的,较小均方末端距的链决定2H谱劈裂,而较大均方末端距的链使2H谱产生长的拖尾. 采用BFM计算机模拟与2H NMR实验的结合是研究拉伸取向聚合物网络微观结构的有力手段. 相似文献
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胶体颗粒在聚电解质多层膜表面的可控组装 总被引:2,自引:1,他引:1
利用原子力显微镜和扫描电子显微镜研究了磺化聚苯乙烯胶体颗粒在由聚二甲基二烯丙基氯化铵和聚苯乙烯磺酸钠层状自组装而成的多层膜表面的组装.该组装受表面性质影响,通过对多层膜的最外层的组装条件或利用盐溶液对多层膜进行后处理可以控制胶体颗粒在膜表面的组装密度. 相似文献
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