Surfactant-aided hydrothermal preparation of La（2-x）SrxCuO4 single crystallites and their catalytic performance on methane combustion

Perovskite-like oxide La2-xSrxCuO4 (x = 0, 1) single crystallites with microrod-like morphologies and tetragonal crystal structures were prepared hydrothermally at 240°C with poly(ethylene glycol) (PEG) or hexadecyltrimethyl ammonium bromide (CTAB) as a surfactant and after calcination at 850°C. The physicochemical properties of the materials were characterized by means of XRD, BET, SEM, TEM/SAED (selected-area electron diffraction), XPS and H2-TPR techniques. It is found that doping Sr2+ to La2CuO4 lattice enhanced the catalytic activity for methane combustion and the LaSrCuO4 catalyst derived from PEG is the best among the tested ones. It is concluded that factors, such as adsorbed oxygen species concentration, reducibility and surface area, determined the catalytic performance of such single-crystalline materials.     

Synthesis of composite TiN/Ni3N/a-Si3N4 thin films using the plasma focus device

Composite films of TiN/Ni₃N/a-Si₃N₄ were synthesized using the Mather-type plasma focus device with varying numbers of focus deposition shots (5, 15, and 25) at 0° and 10° angular positions. The composition and structural analysis of these films were analyzed by using Rutherford backscattering (RBS) and X-ray diffraction (XRD). Scanning electron microscope and atomic force microscope were used to study the surface morphology of films. XRD patterns confirm the formation of composite TiN/Ni₃N/a-Si₃N₄ films. The crystallite size of TiN (200) plane is 11 and 22 nm, respectively, at 0° and 10° angular positions for same 25 focus deposition shots. Impurity levels and thickness were measured using RBS. Scanning electron microscopy results show the formation of net-like structures for multiple focus shots (5, 15, and 25) at angular positions of 0° and 10°. The average surface roughness of the deposited films increases with increasing focus shots. The roughness of the film decreases at higher angle 10° and the films obtained are smoother as compared with the films deposited at 0° angular positions.     

Mechanically Strain-Induced Modification of Selenium Powders in the Amorphization Process

For the fabrication of particles designed in the nanoscale structure, or the nanostructural modification of particles using mechanical grinding process, selenium powders ground by a planetary ball mill at various rotational speeds have been investigated. Structural analyses, such as particle size distributions, crystallite sizes, lattice strains and nearest neighbour distances were performed using X-ray diffraction, scanning electron microscopy and dynamical light scattering.By grinding powder particles became spherical composites consisting of nanocrystalline and amorphous phase, and had a distribution with the average size of 2.7 m. Integral intensities of diffraction peaks of annealed crystal selenium decreased with increasing grinding time, and these peaks broadened due to lattice strains and reducing crystallite size during the grinding. The ground powder at 200 rpm did not have the lattice strain and showed amorphization for the present grinding periods. It indicates that the amorphization of Se by grinding accompanies the lattice strain, and the lattice strain arises from a larger energy concerning intermolecular interaction. In this process, the impact energy is spent on thermal and structural changes according to energy accumulation in macroscopic (the particle size distribution) and microscopic (the crystallite size and the lattice strain) range.     

Influence of crystallite structure of nanometer TiO_2 catalysts on photocatalyst reaction

25 samples of nanometer TiO2 were prepared through modifying the preparation conditions including the concentrations of Ti(SO4)2 and NH4HCO3, the pH value at the end of precipitation operation, and sintering temperature and time by methods of orthogonal design. The relationships between their catalytic activities of photocatalytic degradation of sodium dodecyl benzene sulfonate (SDBS) and the normal crystallite size, lattice-strain and X-ray diffraction intensity of 10 crystal faces were analyzed. It was discovered that the photocatalytic degradation reaction of SDBS follows first-order kinetics. Crystal faces of catalysts' (101) have greater influence than other crystal faces on the reaction. The photocatalytic reaction needs more perfect (101) crystal faces with less lattice-strain. Smaller normal crystallite size and greater specific surface area of (101) crystal face are better for increasing reaction rate. The photocatalytic reaction is mainly proceeded on the (101) crystal face, comparatively, amor     

溶剂热合成法制备(Zn,Hg)S微晶和薄膜

近年来，由于Ⅱ～Ⅵ族半导体纳米材料的特殊物理、化学性质及其在半导体、光学器件、激光二极管、IR探测器等方面的广泛应用，它们的制备和表征引起了人们越来越大的兴趣犤１～１１犦。现在（Zn，Hg）S微晶正被广泛而深入的研究和应用。例如：一种发蓝光的激光二极管已经设计成功，它包含一夹在两衬层间的活性层，无论是在衬层还是在活性层中都包含有（Zn，Hg）S犤５犦。Sugao也曾报道过一种以（Zn，Hg）S为基础的半导体激光器件犤６犦。Parkin曾用MCl２（M＝Zn，Cd，Hg）和Li２E（E＝O，S，Se，Te）混合热解法制备ME或MxM'yS…     

不同金属离子层状双氢氧化物制备及表征

本文采用恒定pH值共沉淀法制备六种层板金属离子不同的层状双氢氧化物(LDH).通过傅立叶变换红外光谱仪(FT-IR)、X-射线衍射仪(XRD)和扫描电子显微镜(SEM)对LDH进行了表征,并利用热重分析(TG)研究了LDH的热分解行为.研究表明,不同金属离子对LDH的层间距、晶粒尺寸等参数有一定影响,团聚程度也有较大的差异.     

Crystallization of poly(ethylene terephthalate–co–isophthalate)

Melt crystallization behaviors of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate‐co‐isophthalate) (PETI) containing 2 and 12 mol % of noncrystallizable isophthalate components were investigated. Differential scanning calorimetry (DSC) isothermal results revealed that the introduction of 2 mol % isophthalate into PET caused a change of the crystal growth process from a two‐dimensional to a three‐dimensional spherulitic growth. The addition of more isophthalate up to 12 mol % into the PET structure induced a change in the crystal growth from a three‐dimensional to a two‐dimensional crystal growth. DSC heating scans after completion of isothermal crystallization at various T_c's showed three melting endotherms for PET and four melting endotherms for PETI‐2 and PETI‐12. The presence of an additional melting endotherm is attributed to the melting of copolyester crystallite composed of ethylene glycol, tere‐phthalate, and isophthalate (IPA) or the melting of molecular chains near IPA formed by melting the secondary crystallite T_m (I) and then recrystallizing during heating. Analyses of both Avrami and Lauritzen‐Hoffman equations revealed that PETI containing 2 mol % of isophthalate had the highest Avrami exponent n, growth rate constant G_o, and product of lateral and end surface free energies σσ_e. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2515–2524, 2000     

煤快速热解焦的微观结构对其气化活性的影响

在滴管炉内对中国三种不同煤阶的典型煤种在800~1 400 ℃进行快速热解实验,利用XRD和氮气气体吸附法对所得煤焦进行微晶结构和孔隙特征分析,在热重分析仪上进行CO₂气化反应活性的测定,研究不同热解温度煤焦结构特性与气化活性之间的关系。结果表明,随着热解温度的升高,内蒙古褐煤焦和神府烟煤焦的比表面积在1 200 ℃达到极大值,但气化活性却相对较低;遵义无烟煤焦在800~1 200 ℃气化活性逐渐提高,但比表面积在900 ℃达到极大值,表明煤焦比表面积与气化活性不存在严格关联。煤焦碳微晶结构变化所反映出煤焦石墨化进程与煤焦气化活性随热解温度的变化具有一致的变化趋势,表明快速热解煤焦的碳微晶结构变化对煤焦气化活性的影响更大。     

Investigation of the effect of forming gas annealing on front silver electrodes of c‐Si solar cells

Forming gas annealing (FGA) is an effective process to repair low efficiency crystalline silicon (c‐Si) solar cells with overfired screen‐printed paste electrodes. An experimental study was performed to investigate the effect and mechanism of FGA treatment on front silver electrodes of c‐Si cells. To facilitate the FGA mechanistic study, special simulation samples were prepared to magnify the FGA effects on glass frit and overfired electrodes. The micro‐morphology (from cross‐sectional X‐SEM) and elemental composition (from energy‐dispersive X‐ray spectroscopy) data revealed few Ag crystallites in the paste/Si interface because of the thick glass layer from the paste overfiring. The FGA treatment induced phase crystallization (from X‐ray diffraction) in the paste and increased the glass wettability on both Si and Ag substrates, thus resulting in a thinner glass layer, which expedited the precipitation of more pyramidal Ag crystallites at the Ag/Si interface. The wetting angle data of glass samples measured before and after FGA confirmed the mechanism of FGA and concluded that the improvement of glass wettability benefited to reduce the glass layer thickness. As a result, more Ag crystallites diffused toward and precipitated at the Si interface contributing to a lower contact resistance between the paste electrode and the Si matrix and thus improved electrical properties for overfired c‐Si cells. Copyright © 2012 John Wiley & Sons, Ltd.