关键词： 低维材料   碳纳米管   填充   包敷   介孔复合体   微观结构  

摘要： 该文在综述了纳米材料,特别是两类典型的低维材料——碳纳米管及介孔复合材料研究进展的基础上,以这两类材料作为该研究的对象,对碳纳米管的填充体系、碳纳米管的包敷体系以及Au(Ru)-SiO<,2>介孔复合体系的制备及微观结构进行了深入研究,内容包括:1、以Co/硅胶为催化剂,苯为碳源气体,采用化学催化法制备了金属Co填充的碳纳米管,与以往的化学催化法不同,该研究中催化剂无需预先还原,催化剂的还原和碳纳米管的填充可一步完成,从而进一步简化了制备工艺,降低了成本.2、开创性地首次采用化学镀方法在碳纳米管表面包敷贵金属金和钌,研究了工艺过程对金属包敷层质量的影响,并用高分辨透射电镜和纳米束能谱等现代手段对金属包敷碳纳米管的形态、微结构和成分进行了表征.3、用溶胶-凝胶法制备了Au(Ru)/SiO<,2>介孔微纳复合颗粒材料,并采用高分辨透射电镜、电子探针和X-射线衍射等手段对其精细结构进行了研究.

关键词： transmission electron microscopy   Ba(Mg1/3Ta2/3)O-3   defect analysis  

摘要： Microstructures of Ba(Mg1/3Ta2/3)O-3 (BMT) materials were examined using high resolution and conventional transmission electron microscopy (TEM) as well as electron diffraction and microstructural characteristics were correlated with microwave dielectric properties of materials. TEM investigations exhibit different types of defects observed at large grains in over-sintered specimens, including dislocations, planar defects and three-dimensional defects. Trace analysis and displacement vector determination imply that stacking faults lying on {1 1 1} planes with a displacement vector of [1 1 0] type may form in the materials. The stacking fault is probably induced by diffusion discrepancy during ordering development of BMT materials which exhibit a concentration wave composition fluctuation at the initial stage. The defects may account for the degradation of over-fired BMT materials. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词： microstructural characteristics   (Pb1-xCax)TiO3 materials   HRTEM  

摘要： Microstructural characteristics including ferroelectric domain boundaries, atomic ordering and TiO6 octahedron tilting of Pb1-xCaxTiO3 (x = 0.3, 0.4, 0.5) were studied and correlated to microwave properties. Using transmission electron microscopy, Pb0.5Ca0.5TiO3 specimens reveal 1/2(l 0 0), 1/2(l 10) and 1/2(l 11) extra reflections regularly in electron diffraction patterns. Dark-field images show two different wavy boundaries using different extra reflections, and their contrast characteristics were discussed. High-resolution transmission electron microscopic (HRTEM) images exhibit ordering characteristics with 1/2(l 11) reflections. However, some regions showing no ordering characteristics also exhibit 1/2(l 0 0) and 1/2(l 10) reflections. An octahedron tilting model combined with atomic ordering was constructed to interpret diffraction behavior in Ph1-xCaxTiO3 materials and the relation between microstructures and microwave properties was also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词： 纳米多孔无机材料   显微结构   结构设计   纳米技术  

摘要： 综述了近年来在制备纳米多孔无机材料时对材料显微结构设计的一些主要思路,并结合近年来纳米多孔无机材料在能源、光电子、材料、化工等领域的实际应用,讨论了此类材料目前面临的问题和今后研究发展的方向。众多研究显示,充分发挥纳米尺寸孔的结构优势和无机材料本身优良的化学性能是此类材料开发的核心思路。对材料纳米结构的控制、梯度孔径的控制、表面修饰技术、制备工艺的优化可改善材料性能,拓展其应用领域;新型纳米多孔无机材料将朝着多种材料复合,多级结构并存的方向发展。

关键词： 原子力显微镜   纳米粒子   聚四氟乙烯材料   超微结构  

摘要： 本文报道了用原子力显微镜 (AFM)研究多种纳米微粒填充的聚四氟乙烯 (PTFE)材料的结构组成 ,观察了在纳米颗粒填充的PTFE中 ,纳米微粒的分散不均匀性以及纳米粉末在与PTFE混合、压制后发生的团聚现象。

关键词： nanocomposites   soft magnets   HITPERM   NANOPERM   FINEMET  

摘要： This paper presents experimental observations of the nanocrystallization process in materials having Fe-Si (FIN-EMET), alpha-Fe (NANOPERM), and alpha'-FeCo (HITPERM) nanocrystals coupled through an amorphous phase. Crystallization kinetics and chemical partitioning during crystallization are described. Isothermal nanocrystallization is discussed in the framework of the Johnson-Mehl-Avrami-Kolmogorov model and constant heating rate experiments analyzed in the context of the Kissinger model. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

关键词： 金属材料   纳米复合材料   添加元素   微结构   永磁性能  

摘要： 利用差热(扫描)分析、X射线、透射电镜、振动作品磁强计研究了添加Co、Dy对Fe_3B/Nd_2Fe_(14)B纳米复合永磁材料的微结构和性能的影响。结果表明:添加适当的微量元素可以提高Nd_(4.5)Fe_(77)B_(18.5)纳米复合永磁材料的内禀磁性,改进微结构,从而提高材料的永磁性能。在Nd_(4.5)Fe_(77)B_(18.5)中添加1％～3％(原子分数)的Co、Dy明显地降低材料的晶化温度和最佳热处理温度、提高了2:14:1相的居里温度、改善了纳米复合永磁材料的微观结构,从而提高材料的永磁性能与Nd_(4.5)Fe_(77)B_(18.5)相比,Nd_(3.5)Fe_(74)Co_3Dy_1B_(18.5)的永磁性能为:Br=1.06T,_jH_c=328kA/m,(BH)_(max)=108.9kJ/m^3,分别提高了26％,17％和104％。

关键词： 无机非金属材料   铬酸镧   高分辨   结构调幅   稀土  

摘要： 用高分辨电子显微镜对铬酸镧的晶体结构及晶界、位错等晶体缺陷进行了观察与分析。高分辨电镜的观察发现了铬酸镧晶体中存在结构调幅,并构建了长程有序结构的模型。对观察到的铬酸镧倾斜晶界进行了分析。电子衍射的结果表铬酸镧在室温上为正交晶系,并发现晶体中存在畴结构。

关键词： 二级界面   复合微粉   显微结构  

摘要： 　介绍了粉煤灰、硅灰、纳米SiO2与水泥水化反应产物的早期界面显微结构,探讨了三种微粉与水泥水化反应的机理及对改善界面结构的作用,并提出了"二级界面"的概念。研究表明,三种微粉对界面的改善呈递增趋势,单一微粉中纳米SiO2的水化产物结构最致密、均匀,微粉复合有效改善二级界面显微结构,有效提高水泥基材料性能。

关键词： 纳米薄膜   二氧化钛   溶胶-凝胶法  

摘要： 通过有机酸修饰的水基sol-gel法,分别制备了由层状、针形和球形纳米粒子构成的纳米二氧化钛薄膜,采用SEM、XRD、红外光谱进行了表征。研究发现,调节水解过程中钛酸四丁酯:醋酸的摩尔比,可以控制薄膜的微结构,并对其机理进行了分析。该方法可以应用于sol-gel法制备其他纳米薄膜过程中的材料微结构控制。