非水解溶胶-凝胶过程制备锡/硅复合氧化物

以无水四氯化锡和正硅酸乙酯为前驱物、环己烷为溶剂,在无氧无水条件下采用非水解溶胶-凝胶过程制备了锡/硅复合氧化物,并对其进行了表征分析。结果表明,在原料Sn/Si摩尔比为1∶2、反应温度为30℃、焙烧温度为500℃时,所得复合氧化物的产率为31.3%,Sn/Si摩尔比为7.4∶1,粒径10nm左右,比表面积22.58cm2.g-1,平均孔径14.3nm,比孔容0.047cm3.g-1,主要为颗粒堆积孔;复合氧化物的主要组成为无定形氧化硅和氧化锡晶体,在焙烧温度达到500～600℃时仍有Sn-O-Si杂键存在。     

Growth of Nickel Oxide Single Crystals and Bicrystals via hemical Vapor Transport

A chemical vapor transport (CVT) method was successfully used to grow NiO single crystals and bicrystals heteroepitaxially on single-crystal MgO substrates. The most favorable growth conditions were obtained at 1400 K using 250 torr (∼3.33 × 10⁴ Pa) of HCl( g ) as the transport agent. Average growth rates greater than 100 μm/h were easily achieved under these conditions. The CVT-grown NiO single crystals and bicrystals usually displayed highly reflective facets along the growth direction that suggest high mechanical quality. The grain boundaries in the bicrystals were observed to be perpendicular to the (001) growth surface. The epitaxial NiO crystals were easily separated from the MgO substrate by dissolving away the latter in 85% H₃PO₄ at 190°C. The crystallinity and purity of the deposits were checked using these free-standing NiO crystals. The concentration of cation impurities and the Cl content in the CVT-grown crystals were investigated by inductively coupled plasma (ICP) mass-spectrometric analysis and neutron activation analysis, respectively. High-resolution transmission electron microscopy of a Σ13 (510) boundary revealed a structure at the atomic scale that provided no evidence for segregated phases.     

Co掺杂对化学气相输运法合成ZnO形貌影响

采用化学气相输运法,研究了在蓝宝石基片上大比例掺杂Co生成的ZnO晶体形貌.分别选用Co2O3与ZnO的质量比3%、5%、7%、15%、20%5种不同含量的样品,通过电子显微镜发现得到的晶体呈六棱结构,一般显露柱面m{1010}、正锥面p{1011}、负极面c{0001}和正极面c{0001},随着Co掺入量的增加得到的Zn1-xCoO晶体表面趋于光滑,晶体六棱结构趋于不对称,锥面面积减小,极性生长特性减弱.Zn1-xCoxO晶体的X射线能谱图显示Co的掺入量与原料配比中Co的量几乎成正比,Co可以大比例掺入ZnO晶体中.     

氟碳铈矿-独居石混合精矿分离提取稀土元素

以气态配合物LnAlnCl3n+3(Ln=稀土元素)为载体,研究了从氟碳铈矿-独居石混合精矿中提取分离稀土元素的分步氯化-化学气相传输反应. 精矿经第一步氯化反应分离回收非稀土元素P, Fe和Th后,生成的稀土氯化物在1000℃与配体反应生成气态配合物,并化学传输分离6 h, CaCl2和BaCl2留在残渣中. 研究发现,递减温度场和波浪温度场中的化学传输反应的分离效果不同,在波浪型温度场中的波谷附近稀土沉积量高且分离系数大.     

炭载镁铝复合氧化物的制备及催化性能研究

采用简单的浸渍法制备了负载型镁铝复合氧化物催化剂,并考察了催化剂在碳酸二甲酯与碳酸二乙酯酯交换反应上的催化性能。系统地研究了载体种类、Mg/Al比、焙烧温度对材料催化性能的影响。研究表明:采用炭材料NC-2为载体的催化剂活性最好,反应过程中无活性组分流失,反应后的催化剂经简单焙烧处理后可多次循环利用。     

环加成反应制备电活性的富勒烯衍生物

系统地介绍了利用「４＋２」、「３＋２」和「２＋１」环加成反应制备电活性富勒烯衍生物的方法。     

Mixed Quantum/Classical Molecular Dynamics Simulations of Chemical Reactions in Clusters and in Solids

An overview is given of a recent method for dynamical simulations of many-atom systems, which incorporates also important quantum effects. The method treats a few pertinent degrees of freedom (e.g., a light atom) by time-dependent wavepackets and all the other coordinates by classical trajectories. The classical and quantum subsystems are coupled in this approach by a hybrid quantum/classical Time-Dependent Self-Consistent Field (TDSCF) approximation. The properties, validity, range, and limitations of this method are discussed, and numerical tests of its accuracy are presented for simple model systems. The method is illustrated by applications to photodissociation of HI molecules in solid Xe and in Xe clusters of different sizes. The scope of potential applications, open problems, and possible directions of extending the method are discussed.     

The Role of Acetic Acid in Magnesium Oxide Preparation via Chemical Precipitation

The role of acetic acid in magnesium oxide (MgO) preparation through a chemical precipitation process was investigated in this work. The as-synthesized precursors and MgO powders were characterized by X-ray powder diffraction, Fourier-transformed infrared spectroscopy, and differential thermal analysis. Compared with the samples without using acetic acid, the addition of acetic acid as a chemical modifier can enhance the crystal growth of the precursor Mg(OH)₂ in (001) orientation, and significantly lower the transition temperature from Mg(OH)₂ to MgO, which could be due to the formation of a bidentate coordination compound of carboxyl groups with magnesium hydroxide.     

Preparation of Zinc Oxide Nanofibers by Electrospinning

Ultra-thin fibers of zinc oxide (ZnO) were prepared by sol–gel processing and the electrospinning technique using poly(vinyl acetate) and zinc acetate as precursors. The fibers were characterized by thermogravimetric analysis, scanning electron microscopy, Fourier-transfer infrared, and X-ray diffraction, respectively. The results showed that the diameter of the precursor fibers increased with increasing zinc acetate content, and the size of the inorganic ZnO nanofibers decreased obviously as the calcining time increased.     

Reactions During Milling of Aluminum Oxide

Exothermic reactions are observed at ∼400°C in alumina powders ball-milled in isopropanol. These are believed to be due to the oxidation of an Al₂O₃-alcohol reaction product formed during milling.     

Nucleation of Solid-State Reactions between Nickel Oxide and Aluminium Oxide

The initial stages of the solid-state reaction between high-quality thin films of nickel oxide and single-crystal aluminum oxide have been investigated. Thin films were grown on specially cleaned and annealed basal-plane (0001) alumina substrates by pulsed-laser deposition. The thin-film reaction couples were then heat-treated in air at 1080° and 1100°C for different times in order to induce the formation of the nickel aluminate spinel. The reaction couples were characterized in cross section by high-resolution scanning electron microscopy and conventional transmission electron microscopy. The films of nickel oxide consisted of two twin variants with a common {111} plane, parallel to the basal plane of alumina, but rotated by 60° or 180° about the 〈111〉 direction normal to that plane. The spinel nucleated where the twin boundaries in the nickel oxide film met the alumina substrate and contained the same twin variants as the original NiO film.     

Point Defects in Electron-Irradiated Oxide Single Crystals

Point defects have been produced in CaO, MgO, and α-Al₂O₃ single crystals by electron irradiation, and thresholds for atomic displacement have been measured using timeresolved luminescence spectroscopy. Oxygen displacement energies of approximately 50 eV have been determined; however, a temperature-dependent threshold observed for an emission band in MgO may arise from a magnesium displacement. A 300-nm emission in α-Al₂O₃ may be due to an F-center transition. Studies of radiative recombination kinetics are consistent with an electron-detrapping model.     

光子晶体及SiO2光子晶体的制备技术

光子晶体是一种具有光子带隙的周期性电介质结构,落在光子带隙中的光将不能传播。由于其独特的调节光子传播状态的功能,成为实现光通讯和光子计算机的基础。SiO2胶体球作为胶体光子晶体的组成基元,具有广阔的应用前景。本文介绍了光子晶体的概念、特征与应用领域,以及SiO2光子晶体的制备技术。     

利用太阳能进行化学反应

太阳能是人类最大的能源。利用太阳最关键的问题是如何有效地收集、贮存和转化。详细介绍为实现将太阳能转有的化学合成而答的天然叶绿素的模拟研究，并简要说明太阳能在处理废水中稠环芳烃与多氯联苯方面的直接利用。     

Internal Reactions in Oxide Solid Solutions

Oxidation of wustite-type solid solutions (A, B)0 and reduction of sesquioxide solid solutions (A, B)₂0₃ can lead to the precipitation of a spinel phase (A, B)₃0₄ at an inner reaction front. A representation of the reaction scheme and kinetics for each of the two cases will be given. Observations on the macroscopic morphology of the spinel precipitates and on the structure of the precipitate/matrix interphase boundary are discussed.