Condensation route of evolution of nanodispersed substances

Numerous experimental data indicate that nanosystems develop by stages. The evolution route of closed nanosystems includes stages of nanoparticle nucleation, growth, ripening, and agglomeration, and texture and composition ordering. In closed systems, nanodispersed substances occur in the nano-state for a limited period of time, which can be changed by varying the supersaturation of the medium with respect to nanoparticles. Nanoparticles in open systems tend to degrade due to chemical transformations, dissolution, or evaporation and the lifetime of open systems can be estimated. At every stage of development of nanosystems, the rates of variation of the state parameters of nanoparticles fluctuate over a scale much exceeding the molecular scale. The behavior of the set of nanoparticles is described by a Fokker—Planck type equation, which may underlie the formulation of the principal equation of physicochemical evolution of nanosystem.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 17–31, January, 2005.     

Agglomeration control during the selective epitaxial growth of Si raised sources and drains on ultra-thin silicon-on-insulator substrates

We have studied the impact of several Si selective epitaxial growth (SEG) process on the agglomeration of ultra-thin, patterned silicon-on-insulator (SOI) layers. Through a careful analysis of the effects of the in situ H₂ bake temperature (that followed an ex situ “HF-last” wet cleaning) and of the silicon growth temperature on the SOI film quality, we have been able to develop a low-temperature SEG process that allows the growth of Si on patterned SOI layers as thin as 3.4 nm without any agglomeration or Si moat recess at the Si window/shallow trench isolation edges. This process consists of an in situ H₂ bake at 650 °C for 2 min, followed by a ramping-up of the temperature to 750 °C, then some SEG of Si at 750 °C using a chlorinated chemistry (i.e. SiH₂Cl₂+HCl).     

我国纺织业集聚分布格局及其影响因素的空间面板数据分析

在我国,关于区域产业集聚的理论研究进展迅速,但基于空间计量经济模型的实证研究仍需完善。本文采用中国2004-2007省际面板数据,验证纺织业集聚的空间依赖性存在,并分别对空间滞后模型和空间误差模型进行估计,得出以下结论:近些年纺织业集聚的省际分布格局主要呈现"东高西低"的两极化特征,总体变化不大;根据全局Moran I指数和LISA集聚图,纺织业集聚存在空间维度的依赖性和异质性,东部沿海纺织业的扩散作用没有充分发挥,区域发展很不平衡;原料供给量、平均规模水平、交通运输条件等因素都对纺织业集聚产生不同程度的正向影响,而地方保护阻碍产业跨区迁移与形成集聚;与理论假设不同,低廉的劳动力成本对纺织业集聚没有产生明显的促进作用,主要是受到基础设施状况和运输条件的限制;制定相关政策的同时,注意从以上这些要素入手,还必须充分考虑空间作用机制对纺织业省域集聚的差异化作用。     

煤的油团聚的表面热力学理论

本文试图用过程的自由能改变来预言油团聚的热力学稳定性，对具有最低自由能的状态被认为是最稳定状态。本文导出了油团聚过程的自由能，（ｄＦ）Ｔ，ｐ＝４πｒ１＾２γ＾２３「（１－ｃｏｓψ）√２（１－ｃｏｓψ）－ｃｏｓθ（１－ψ－ｎ＾２）。由此可见，自由能的降低是由油滴对煤粒大小的比值，三相接触角和油水之间的表面张力来确定。     

Fischer-Tropsch synthesis over Ru/Al2O3 catalysts

Fischer-Tropsch syntheses (FTS) were carried out in a slurry phase over Ru/Al₂O₃ catalysts using hexadecane as a solvent. The outcome of the FTS was dependent on the oxide support, calcination temperature, synthesis gas composition and sulfur content. The addition of Mn/Na to Ru/Al₂O₃ was effective in raising the initial activity and C5+ selectivity, but after 20 hours, the performance of the modified catalyst was similar to that of the unmodified catalyst. An additional investigation involving the use of fresh vs used catalysts demonstrated that an agglomeration of the metallic Ru, at least in part, does occur during the reaction.     

利用多孔阳极氧化铝研究载体孔洞尺寸对负载银粒子团聚的影响

 利用阳极氧化方法制备了具有规整的可控孔洞尺寸的多孔Al2O3 膜,并以此模拟实际的催化剂载体制备了负载银催化剂. 采用扫描电镜、能量分散谱、透射电镜、X射线衍射和X射线光电子能谱等手段,研究了多孔阳极氧化铝的孔洞大小对负载的银粒子团聚的影响. 结果表明,载体孔洞尺寸对银粒子团聚可能起到限制作用,而且这种限制作用随载体孔洞尺寸增大而减小. 当载体的孔洞尺寸约为50 nm时,随温度升高银粒子的团聚和生长都不明显; 当载体的孔洞尺寸约为200 nm时,随温度升高银粒子发生一定程度的团聚和生长,但孔洞尺寸的限制作用仍存在. 这种载体尺寸的限制作用可以有效地阻止催化剂活性组分的团聚.     

Synthesis of Nanocrystalline Ceria Particles for High Temperature Oxidation Resistant Coating

Cerium oxide has been investigated to be an effective coating material for high temperature applications for various alumina- and chromia-forming alloys. The present study investigates the use of microemulsion method to obtain monodispersed, non-agglomerated nanocrystalline ceria particles in the range of 5nm using sodium bis(2-ethylhexyl) sulphosuccinate (AOT) as a surfactant. Furthermore, the use of non-agglomerated nanocrystalline ceria particles to develop improved high temperature oxidation resistant coatings on AISI 304-grade stainless steel was investigated. It was found that non-agglomerated nanocrystalline ceria particles were more effective in improving the oxidation resistance than the agglomerated nanocrystalline particles.     

熔盐法合成NiO纳米微晶

纳米科技的基础是纳米结构材料的合成．它是纳米科技在分散与包覆、高比表面材料、功能纳米器件、强化材料等方面实现突破的起点。纳米颗粒（1-100nm）本身具有宏观量子隧道效应、量子尺寸效应、表面效应许多独特的性能．其制备研究日益得到广泛关注和重视．     

液相中超细Al(OH)3粒子的生长团聚机理

采用碳化法制得到超细Ａｌ(ＯＨ)3溶胶[1],在后处理工序中,液相中的Ａｌ(ＯＨ)3粒子容易发生团聚而失去许多优越的特性,影响其作为阻燃添加剂的效果。研究液相中Ａｌ(ＯＨ)3粒子团聚的机理,为固液分离和干燥过程防止超细Ａｌ(ＯＨ)3粒子的再团聚提供理论依据。1　实验将刚从旋转填料床中制备的Ａｌ(ＯＨ)3溶胶置于恒温釜中,保持温度不变。调节碱度值、改变搅拌速率和添加表面活性剂等条件,每隔一定时间取样在电镜下观察粒子团聚情况;用日本理学机电公司Ｄ/ｍａｘ-γＢＸ型Ｘ射线衍射仪对粉末样品的物相组成、晶形进行分析;利用日立公司…     

声波团聚技术发展现状及在火灾消烟应用前景*

声波团聚技术在细颗粒物排放控制领域具有很好的应用前景,最近衍生发展为一种全新的火灾烟雾控制手段。该文对声波团聚技术发展现状进行全面总结,介绍近年的实验和理论研究进展。随后,阐述了声波团聚消烟的基本原理,并以火灾烟雾中占比较大的电缆燃烧烟雾为实验对象,发现声波团聚技术在一分钟后就实现对电缆燃烧烟雾的完全消除,即存在突出团聚效果。该结果验证了该技术在火灾烟雾控制领域的可行性。最后,依托我国城市发展现状,探讨了声波团聚技术在火灾消烟的发展前景。