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二氧化钛/钛酸盐纳米材料的晶型、尺寸、形貌和微结构等特征对物理化学性能有着至关重要的影响。晶体生长过程包括晶型转变和形貌演化等行为。本文综述了近年来在二氧化钛/钛酸盐纳米粉体材料晶型与形貌的控制合成工作中, 材料晶型转变和形貌演化行为方面的研究进展。对奥斯特瓦尔德规则、奥斯特瓦尔德熟化机制、柯肯达尔效应和定向附着生长模式等重要的机理进行了阐述, 并将晶体生长机理应用于二氧化钛/钛酸盐纳米粉体材料的合成过程中。不仅利用上述晶体生长机理解释了不同晶型、不同形貌二氧化钛/钛酸盐纳米粉体材料的生成原因, 并且利用晶体生长机理指导二氧化钛/钛酸盐纳米粉体材料晶型与形貌的控制合成工作。 相似文献
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以海藻酸钠为晶体生长调节剂, 在水热条件下制备了形貌均匀、高长径比的羟基磷灰石(Hydroxyapatite, HA)单晶纳米棒。通过X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、场发射扫描电镜(FE-SEM)、透射电镜(TEM)以及同步热分析(TG/DSC)等测试方法对合成产物进行了表征, 探索了反应温度和时间对产物的结晶度、组成以及形貌的影响, 并提出了HA纳米棒的合理生长机理。研究表明, 80℃水热条件, 反应24 h, 对于均匀、低有机吸附量的HA单晶纳米棒合成较有利。对纳米棒的不同生长阶段的微结构分析表明: 晶体生长经历了成核、表面调控、继续生长和取向搭接四个阶段。 相似文献
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采用一种新的合成技术,在固熔的复合氢氧化物中,200℃、24h的生长条件下制备了立方相的CaF2、KCrF3纳米颗粒和六方相PbF2纳米片.用X射线衍射(XRD)、扫描电子显微镜(SEM)和UV-vis分光光度计对合成纳米晶的粒径、形貌和光学性质进行了表征.结果表明,使用复合氢氧化物固熔法合成的氟化物纳米晶体结晶良好且尺寸均匀,通过UV-vis吸收谱发现,所合成的氟化物纳米晶在紫外或深紫外区域具有强烈吸收.基于结晶学、结晶化学和现代溶液理论对氟化物纳米晶的生长机理进行了分析. 相似文献
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本文通过对水热产物AlOOH的形貌及晶粒度测试,了解了由提高水热温度和延长水热时间导致的颗粒形态的变异以及多种形貌共生的现象。运用临界成核理论及颗粒成长理论给予了合理的解释。此外还结合晶体成长阶段性理论,阐述了第Ⅰ类聚集和第Ⅱ类聚集生长的机理。揭示了水热过程中产物形貌发生变异和多种形貌混杂的深层原因,得出了水热过程中普... 相似文献
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简述了利用水热/溶剂热法合成铜基微纳米晶体颗粒材料的最新研究进展。介绍了氧化亚铜、碱式碳酸铜、碱式钼酸铜、碱式氯化铜、碱式磷酸铜等铜基微纳米材料的合成方法。对铜基微纳米晶体颗粒材料生长机理和形貌控制合成进行了分析,获得了对铜基微纳米晶体颗粒材料生长规律的一般性认识,实现了在水热/溶剂热条件下对铜基微纳米晶体颗粒材料生长的形貌控制合成。 相似文献
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在1400℃,用Ti,Si,C,Al,NaCl原料,氩气保护下无压烧结合成出纯净的、层状的Ti3SiC2陶瓷。用X射线衍射、扫描电子显微镜,透射电子显微镜对Ti3SiC2陶瓷的物相、表面形貌、微观结构进行表征。对合成出的Ti3SiC2陶瓷的微观形貌进行观察,发现Ti3SiC2晶体中有规整的六方形状的层状晶体,提出了Ti3SiC2晶体的自由生长的机理。Ti3SiC2晶体的生长机理由二维成核理论控制,台阶状晶体生长的形貌表明(002)晶面的生长要经过两个独立的过程。添加NaCl,有助于生成高纯度的层状Ti3SiC2陶瓷。 相似文献
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VO_2是一种具有极大应用价值的功能材料,其潜在的应用产品有智能窗、热敏电阻、锂离子电池电极等,但纳米VO_2的大批量制备技术成了制约其应用的关键因素。水热合成法反应条件温和、对环境的污染小、能耗低、价格便宜;易控制化学价态、晶相、产物纯度较高;反应无需煅烧晶化,可以减少煅烧过程中产生的团聚,可获得通常条件下难以得到的纳米粉体,粉体粒径分布较窄、晶型和形貌可控,有望用于VO_2纳米结构的大量合成。聚焦于水热合成法制备纳米VO_2及其相变机理的研究进展,着重介绍了不同形貌与物相的纳米VO_2的水热合成制备方法、物相转换及机理、水热过程中VO_2的生长机制。最后,指出了水热法制备VO_2所面临的一些问题,并展望了未来的发展方向。 相似文献
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纳米分子筛具有短的孔道和较开放的晶穴,不仅在催化、离子交换、复合材料方面显示优异性能,而且在分子组装、光电磁功能纳米材料制备上是一种优良的载体材料或宿主材料.同时,对纳米分子筛的研究利于从深层次了解分子筛的核化和生长机理.介绍了纳米晶分子筛的合成、晶化特征及应用进展,进一步对新成分和结构分子筛、分子筛及纳米晶组装体系的新成果做了概述,指出了纳米分子筛研究的几个主要方向. 相似文献
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Tao‐Tao Zhuang Pan Yu Feng‐Jia Fan Liang Wu Xiao‐Jing Liu Shu‐Hong Yu 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(7):1394-1402
Colloidal synthesis of kinked ultrathin ZnS nanorods/nanowires with mixed phases using tiny Ag2S nanocrystals as catalysts is reported. It is found that chloride ions can induce the controlled morphology transition from straight to kinking. The synthetic parameters modulating the growth of kinked ZnS nanorods/nanowires are systematically investigated. Chloride ions introduced in the reaction can generate more proportion of wurtzite phase by slowing the nucleation and growth rates during the growth of one‐dimensional (1D) ZnS nanorods/nanowires. The formation of kinked morphology is responsible for the increased domains of mixed stacking and twinning in single 1D nanostructures. The present recipe on controlled synthesis of 1D kinked nanorods/nanowires provides a model of crystal growth control, and these unique 1D nanostructures may also offer new opportunities to fabricate nanodevices with special functions. 相似文献
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《Zeolites》1994,14(7):568-575
The method of chronomal analyses (dimensionless time analyses) according to Nielsen has been applied to the growth of discrete colloidal particles (particle sizes of less than 100 nm) of TPA-silicalite-1 to gain information on the crystal growth mechanism. The increase in particle size in the range 30–95 nm was monitored by dynamic light scattering and yielded the result that the increase in crystal size is a linear function of synthesis time. The linear growth rate of the almost spherical particles at 100°C is 3.79 nm/h — a low value that is ascribed to the synthesis conditions employed. Furthermore, the particle number concentration was shown to be constant, indicating that no secondary nucleation event occurs during the growth process. The crystallization kinetics recorded in the temperature interval 80–100°C correlate with a first-order surface reaction controlled growth mechanism in which the corresponding apparent energy of activation is 42 kJ/mol. A diffusional mechanism as well as a compound growth mechanism in which both surface reaction and diffusion compete for rate control can be ruled out as being operative. 相似文献
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Zhong-Hui Xue Shu-Xi Dai Bin-Bin Hu Zu-Liang Du 《Materials science & engineering. C, Materials for biological applications》2009,29(6):1998-2002
Bovine serum albumin (BSA) Langmuir monolayer, as a model of biomineralization-associated proteins, was used to study its effect on regulated biomineralization of calcium carbonate. The effects of the BSA Langmuir monolayer and the concentration of the subphase solution on the nucleation and growth processes and morphology of the calcium carbonate crystal were investigated. The morphology and polymorphic phase of the resulting calcium carbonate crystals were characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Moreover, the interaction mechanisms of the subphase solution with the BSA Langmuir monolayer were discussed. It was found that BSA Langmuir monolayer could be used as a template to successfully manipulate the polymorphic phase and crystal morphology of calcium carbonate and had obvious influence on the oriented crystallization and growth. The final morphology or aggregation mode of the calcite crystal was closely dependent on the concentration of calcium bicarbonate solution. It is expected that this research would help to better understand the mechanism of biomineralization by revealing the interactions between protein matrices and crystallization of calcium carbonate crystal. 相似文献
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沉淀碳酸钙(PCC)的发展及应用 总被引:1,自引:0,他引:1
简述碳酸钙的分类、用途、工业现状、国内外在碳酸钙多相合成体系流变学及转递行为、碳酸钙形成机理和形态控制技术以及结晶生长成核理论的研究成果 ,并讨论了碳酸钙粉末表面处理的方法、机理。对高档卷烟纸专用碳酸钙的性能要求进行了探讨 相似文献
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When colloidal crystal films are deposited onto nanocrystalline porous substrates by the commonly used colloidal crystallization method of vertical deposition self-assembly, the colloidal crystal tends to be poorly adhered to the porous film. Herein, we present a fabrication of large-area, three-dimensional (3D) colloidal crystal thin films on nanocrystalline porous substrates by a room temperature floating self-assembly method that has recently been developed for colloidal crystal deposition. Firstly, colloidal suspensions were prepared by dispersing monodisperse colloidal microspheres at high volume fraction in a mixture of ethanol and water. At room temperature, these suspensions were spread onto nanocrystalline porous TiO2 films. The colloidal particles assembled into 3D ordered structures at the air−liquid interface of the suspensions as a result of rapid evaporation of the solvents. After the solvents (water and ethanol) had evaporated completely, the colloidal crystals were directly deposited on the nanocrystalline porous TiO2 films. Scanning electron microscopy images and normal-incidence transmission spectra of the samples showed that the colloidal crystal films deposited on the nanocrystalline porous TiO2 substrates by this method had very high crystalline quality. In addition, the effect of the degree of surface roughness of the nanocrystalline porous substrate on the crystalline quality of the colloidal crystals has been studied. 相似文献
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Meiguang ZHANG) Haiyan YAN) Fang PENG) ) 《材料科学技术学报》2008,24(5):809-812
Synthesizing diamond single crystal by diamond seed particles which were electroplated with nickel film as catalyst under high pressure and high temperature (HPHT) was described. The microstructure of nickel film after synthesis and morphology of grown diamond were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The phase structure in nickel film were graphite, NiC, Ni, and diamond structure hadn't been found. A lot of recrystallized graphite pits appear in interface between the inner surface of nickel film and the surface diamond. It is shown that the new-grown diamond was developed epitaxially on the crystal planes of seeds. Also, the new-grown diamond grew by two-dimensional nucleation and by a layer growth mechanism. The growth process of crystal was microaggregate→step→expansion→new crystal layers, and the flat growth interface transformed into a cellular interface at the same time. 相似文献
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Fiona C. Meldrum Cedrick O'Shaughnessy 《Advanced materials (Deerfield Beach, Fla.)》2020,32(31):2001068
Many crystallization processes of great importance, including frost heave, biomineralization, the synthesis of nanomaterials, and scale formation, occur in small volumes rather than bulk solution. Here, the influence of confinement on crystallization processes is described, drawing together information from fields as diverse as bioinspired mineralization, templating, pharmaceuticals, colloidal crystallization, and geochemistry. Experiments are principally conducted within confining systems that offer well-defined environments, varying from droplets in microfluidic devices, to cylindrical pores in filtration membranes, to nanoporous glasses and carbon nanotubes. Dramatic effects are observed, including a stabilization of metastable polymorphs, a depression of freezing points, and the formation of crystals with preferred orientations, modified morphologies, and even structures not seen in bulk. Confinement is also shown to influence crystallization processes over length scales ranging from the atomic to hundreds of micrometers, and to originate from a wide range of mechanisms. The development of an enhanced understanding of the influence of confinement on crystal nucleation and growth will not only provide superior insight into crystallization processes in many real-world environments, but will also enable this phenomenon to be used to control crystallization in applications including nanomaterial synthesis, heavy metal remediation, and the prevention of weathering. 相似文献