双金属催化剂Ni-Co/SiO2空心球的可控制备及催化性能

以二氧化硅为模板, 采用牺牲模板/界面反应法制备具有介孔结构的碱式硅酸镍钴空心球。采用透射电子显微镜(TEM)、X 射线衍射(XRD)、氮气吸脱附曲线(BET)和程序升温还原(TPR)等方法, 对样品的结构和形貌进行了表征, 探索了碱式硅酸镍钴空心球还原规律, 并研究了双金属催化剂Ni-Co/SiO₂的催化性能。研究发现, 140℃下反应6 h, 产物为核壳结构, 反应12 h时变为空心球结构; 在氢气气氛中800℃下反应5 h, 碱式硅酸镍钴被完全还原为Ni-Co/SiO₂, 还原前后形貌基本不变, 但比表面积有所减小, 孔径增大。Ni-Co/SiO₂空心球用于催化硝基苯加氢反应1 h后, 硝基苯的转化率为67%, 比商用Raney Ni 提高约28%。     

Oxidation of silicon nitride sintered with ceria and alumina

Abstract

Sinter-hipped silicon nitride with additions of ceria and alumina has been subjected to oxidation for up to 72 h at various temperatures. Within the experimental temperature range (1250–1425°C), a parabolic weight gain was observed with an activation energy of 350 kJ mol^?1 for the process. On oxidation there formed an oxide scale whose morphology depended on temperature and cooling rate, and a subscale, at the interface between the substrate and the oxide scale, consisting of β3-Si₃MN₄ grains, a Ce-rich silicate glass, and Si₂N₂0. The morphology and phase content of the oxide products were characterised by X-ray diffractometry and electron microscopy. Detailed analyses by SEM showed that the oxide scales were not homogeneous, but exhibited several layers with important microstructural and compositional variations through their thickness.

MST/1107     

Effects of initial oxide on microstructural and mechanical properties of friction stir welded AA2219 alloy

Effects of various initial surface oxide films on microstructural and mechanical properties of friction stir welded (FSW) joints have been studied in the present paper. Anodizing was adopted to produce oxidation on AA2219-T62 surface. A series of friction stir welded joints were produced with various initial surface oxidations to study the effects on microstructural and mechanical properties of the joints. X-ray radiography inspection was conducted to determine the existence of welding defects. Optical microscopy (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize stir zone features and microstructure. Tensile test was employed to obtain FSW joint mechanical properties. Results show that initial surface oxide film has pronounced effect on the joint line remnant (JLR) distribution, microcosmic appearance and mechanical properties. Further analysis of the JLR particles suggests that the dispersed particles are Al₂O₃ oxide with the characteristics of polycrystalline structure because of the effect of the thermo-mechanical cycles. In addition, tensile strength of FSW joints with JLR inside the stir zone only reached about 60% of a sound FSW joint. Fractography analysis of broken tensile specimens exposed a series of severe “scalloping” correlated with JLR flaw, while sound weld exhibits fine dimples on the fracture surface.     

Facile Synthesis of Nanocrystal Tin Oxide Hollow Microspheres by Microwave-Assisted Spray Pyrolysis Method

Tin oxide(SnO_2) hollow microspheres with narrow size distribution were prepared by a facile one-pot microwave-assisted spray pyrolysis method. The effect of temperature on microstructural and optical properties was investigated by X-ray diffraction(XRD), scanning electron microscope(SEM), high resolution transmission electron microscope(HRTEM), and UV-Vis spectrophotometer(UV-Vis), respectively.The SnO_2 particles obtained at and above 700?C are tetragonal rutile structure with high purity and smooth surface morphology, which consist of well-interconnected SnO_2 nanocrystallines and the shell thickness was about 26 nm. UV-Vis absorption values were quite low in visible light region and high in ultraviolet region, indicating the possible utilization for optical purpose of the as-prepared SnO_2. The band gaps were 3.88 and 4.07 e V for SnO_2 synthesized at 700 and 800?C, respectively. As compared to traditional electrical heating or flame modes, microwave heating introduced here demonstrates a highefficiency, environmentally benign, and time-and energy-saving technology to synthesize advanced powders.     

Carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate

The carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate was studied using a thermogravimetric analysis system (TGA), an X-ray diffractometer (XRD), an atomic absorption spectrometer (AAS), a carbon and sulfur determinator (CSD), an elemental analyzer (EA), a scanning electron microscope (SEM) and a surface area analyzer (SAA). Experimental results revealed that the reaction rate was significantly enhanced by the lithium carbonate catalyst. The results of TGA, AAS, CSD and EA were found to be comparable. A reaction mechanism was proposed to interpret the overall reaction.     

超声波-共沉淀法制备ZrO_2-MgO超细粉

以ZrOCl2·8H2O为原料,用乙醇和聚乙二醇两种有机溶液处理,在化学共沉淀阶段使用超声波辐照制备MgO稳定ZrO2超细粉,通过X射线衍射(XRD)、激光粒度分析、扫描电子显微镜(SEM)和差热分析(DSC)等手段对试样的微观结构进行表征。试验结果表明,用超声波辐照制备合成MgO稳定ZrO2超细粉,其结晶温度低,粉料的分散性好,不易团聚。     

液相制备石墨烯/硫复合材料及其在锂硫电池正极中的应用

采用氧化石墨烯(grapheneoxide,GO)作为制备石墨烯的前驱体,通过液相还原自组装过程与硫纳米颗粒进行复合,获得了高性能的还原氧化石墨烯/硫(r GO/S)复合正极材料。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、拉曼光谱、X射线光电子能谱分析(XPS)等对材料微观形貌与结构进行表征。结果表明:硫纳米颗粒均匀分布在石墨烯片层间,并且硫纳米颗粒被石墨烯片层有效地封装,硫在35-r GO/S复合物中的质量分数高达83.6%。该35-r GO/S复合正极在0.2C电流密度下初始放电容量可达1197.3mAh·g^-1,经过200次循环后容量仍保持在730mAh·g^-1左右,表现出优异的循环性能。     

磺化石墨烯及其导电炭薄膜的制备与性能

以石墨为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 通过低温真空剥离预还原、磺化反应、葡萄糖二次还原, 合成了高质量的磺化石墨烯(S-GNS), 有效避免了在此过程中石墨烯大量团聚的现象. 采用傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)、热重分析仪(TG)、X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和原子力显微镜(AFM)等分析手段对磺化石墨烯样品进行了表征. 实验结果表明: 对氨基苯磺酸成功地接枝到了石墨烯上, 磺化石墨烯还原彻底, 热稳定性能高; 石墨烯表面平整, 缺陷少; 单层磺化石墨烯厚度约为1.2 nm. 水溶性、分散性实验结果表明: 磺化石墨烯拥有高水溶性和高分散性. BET比表面积及电性能测试表明: 磺化石墨烯的比表面积高达806.4 m²/g, 薄膜材料的导电率为1150 S/m.     

硅灰石表面无机改性及其在聚丙烯中的应用

采用非均匀成核法,通过在硅灰石表面包覆硅酸铝对硅灰石进行了无机改性。扫描电镜（SEM）和X射线衍射（XRD）等测试表明,无机改性硅灰石颗粒表面粗糙,包覆着许多纳米硅酸铝粒子;通过BET比表面积分析仪测定,比表面积提高200%以上;红外光谱（FT-IR）测试表明,无机改性后硅灰石表面羟基增多;白度测试表明,无机改性硅灰石...     

低温剥离法制备高性能石墨烯/ZnO复合材料

采用氧化石墨和七水合硫酸锌作为初始反应物, 在低温下(80℃)合成了氧化石墨/ZnO, 然后通过低温剥离法制备了高质量石墨烯/ZnO (GNS/ZnO)复合材料. 采用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、热重分析仪(TG)、X射线光电子能谱(XPS)、拉曼光谱(RS)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等分析手段对石墨烯/ZnO样品进行了表征. 结果表明: 氧化石墨还原彻底, 纳米ZnO成功地负载到了石墨烯上, 有效地减少了石墨烯片层间的团聚现象. 通过对ZnO和石墨烯/ZnO荧光性能测试, 结果表明: 石墨烯/ZnO发生了荧光淬灭现象, 在光电子领域拥有广阔的应用前景.     

Influence of silicon content on the microstructure and hardness of CrN coatings deposited by reactive magnetron sputtering

CrN and CrSiN films were deposited on the stainless steel and silicon substrates by DC magnetron sputtering and their microstructural features were investigated by X-ray diffraction (XRD), scanning electron microscope (FE-SEM/EDS), and atomic force microscopy (AFM). The influence of Si content along with process parameters such as power on the microstructural characteristics of Cr–Si–N and CrN films were investigated and compared between each other. The power and increasing Si contents strongly influence the microstructural and hardness of the deposited films. XRD analysis of the coatings indicates a grain refinement with increase in Si content during deposition of coatings, which is tandem with AFM and SEM results. Also, the surface roughness and particle size are decreasing with addition of Si in the films. The hardness of CrN and CrSiN was measured by microhardness tester and found that introduction of Si content in the CrN system increases its hardness from 1839 Hv to 2570 Hv.     

Differing Effects of Mn and Mg Oxide Sintering Aids on Sialon Creep and Fracture

This study is based on two sialon ceramics hot-pressed with small amounts of two different sintering additives, MgO and Mn₃O₄. The grain boundary interfaces were characterized by high resolution electron microscopy and Auger electron spectroscopy.The major microstructural difference between the two ceramics was the occurrence of microscopic regions of triple junction silicate glass in the Mn containing ceramic. High temperature creep studies of this ceramic showed cavitation induced deformation. In contrast there was no detectable interfacial silicate phase in the Mg containing ceramic and no cavitation was observed during high temperature deformation.Furthermore, microstructural observations revealed that long duration heat-treatment of the Mn containing ceramic resulted in reduction of triple junction glass beyond detection. This desegregation of impurities led to non-cavitating deformation and hence resulted in marked improvement in creep and slow fracture resistance.     

Characterization of electroplated FeSe thin films

Thin films of iron selenide (FeSe) were electrodeposited on tin oxide coated conducting glass substrates at various bath temperatures, deposition potential and solution pH values. The deposited films were characterized by X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy and optical absorption techniques, respectively. The structure was found to be hexagonal with preferential orientation along {002} plane. X-ray line profile analysis technique by the method of variance has been used to evaluate the microstructural parameters. The variation of microstructural parameters with bath temperature, deposition potential and solution pH values were studied. The observed results are discussed in detail.     

Compressive strength and microstructural analysis of fly ash/palm oil fuel ash based geopolymer mortar

This paper presents the effects and adaptability of palm oil fuel ash (POFA) as a replacement material in fly ash (FA) based geopolymer mortar from the aspect of microstructural and compressive strength. The geopolymers developed were synthesized with a combination of sodium hydroxide and sodium silicate as activator and POFA and FA as high silica–alumina resources. The development of compressive strength of POFA/FA based geopolymers was investigated using X-ray florescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field emission scanning electron microscopy (FESEM). It was observed that the particle shapes and surface area of POFA and FA as well as chemical composition affects the density and compressive strength of the mortars. The increment in the percentages of POFA increased the silica/alumina (SiO₂/Al₂O₃) ratio and that resulted in reduction of the early compressive strength of the geopolymer and delayed the geopolymerization process.     

Strength and hydration products of reactive MgO–silica pastes

The reaction between MgO and microsilica has been studied by many researchers, who confirmed the formation of magnesium silicate hydrate. The blend was reported to have the potential as a novel material for construction and environment purposes. However, the characteristics of MgO vary significantly, e.g., reactivity and purity, which would have an effect on the hydration process of MgO–silica blend. This paper investigated the strength and hydration products of reactive MgO and silica blend at room temperature up to 90 days. The existence of magnesium silicate hydrate after 7 days’ curing was confirmed with the help of infrared spectroscopy, thermogravimetric analysis and X-ray diffraction. The microstructural and elemental analysis of the resulting magnesium silicate hydrate was conducted using scanning electron microscopy and energy dispersive spectroscopy. In addition, the effect of characteristics of MgO on the hydration process was discussed. It was found that the synthesis of magnesium silicate hydrate was highly dependent on the reactivity of the precursors. MgO and silica with higher reactivity resulted in higher formation rate of magnesium silicate hydrate. In addition, the impurity in the MgO affects the pH value of the blends, which in turn determines the solubility of silica and the formation of magnesium silicate hydrate.     

Optical properties of NiO thin films fabricated by electron beam evaporation

Nickel oxide (NiO) thin films were deposited onto quartz substrates by the electron beam deposition technique, and obtained high crystal quality after annealing at 1173 K. The structural and microstructural properties of the films were studied by X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. We focus on the optical characterization of the films, indicating the enhancement of the crystal quality, which was confirmed by the photoluminescence and Raman spectrum. Furthermore, PL studies exhibited room temperature emission at 377 nm, and also shown high ultraviolet/visible rejection ratio (>100).     

介孔硅酸锰镁可充镁电池正极材料的制备及其电化学性能研究

采用介孔二氧化硅MCM-41作模板和硅源, 合成了具有介孔结构的可充镁电池正极材料硅酸锰镁. 分别用XRD、SEM、TEM和氮气吸脱附测试研究了合成材料的介孔结构, 并通过循环伏安、恒电流充放电测试比较了介孔与无孔硅酸锰镁材料的电化学性能. 由于介孔材料活性表面较大, 可增加电解液与活性材料的接触, 使材料具有较多的电化学反应位. 因而, 与相应的无孔材料相比, 具有介孔结构的硅酸锰镁材料呈现出较低的充放电极化、较大的放电容量和较高的放电电压平台. 在0.25 mol/L Mg(AlCl₂EtBu)₂/THF 电解液中, 0.2 C(约62.8 mA/g)充放电速率下, 介孔硅酸锰镁材料首次放电容量可达到241.8 mAh/g, 放电平台为1.65 V ( vs Mg/Mg²⁺). 设计具有介孔结构的材料为提高可充镁电池正极的电化学性能提供了一条有效的途径.     

TC4钛合金表面氧化亚铜掺杂微弧氧化层的结构和性能

在电解液中添加不同浓度的氧化亚铜微粒,然后在TC4钛合金表面制备掺杂铜氧化物的微弧氧化层。在模拟海水中进行微弧氧化层的摩擦磨损和抗菌实验,并使用扫描电镜(SEM)、X射线衍射仪(XRD)、X光电子能谱仪(XPS)和显微硬度仪等手段对比研究了掺杂氧化亚铜的微弧氧化层的微观结构和性能。结果表明：掺杂氧化亚铜的微弧氧化层表面呈多孔形貌特征,但是微孔的数量较少和孔径尺寸较小,氧化亚铜微粒在膜层中以氧化铜和氧化亚铜两种形式存在;与未掺杂氧化亚铜的微弧氧化层相比,添加不同浓度氧化亚铜的微弧氧化层在模拟海水中的抗磨损性能和抗菌性能显著提高,但是微弧氧化层中的铜元素使其耐蚀性有所降低。     

Effects of grain refinement and disorder on the electronic properties of nanocrystalline NiO

Nanocrystalline NiO thin films have been grown on different substrates by RF magnetron sputtering with mixed O₂?Ar plasma composition. The oxygen content of the plasma was varied between 0 and 100 %. The films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS). SEM results reveal a grain refinement when oxygen is added to the plasma. This effect can also be observed by XRD, where an analysis of the peak width confirms this decrease in the grain size. The analysis of EXAFS data shows that the presence of O₂ in the plasma induces lattice disorder, as evidenced by the observed increase of the Debye–Waller factor. These microstructural changes modify the electronic structure of the NiO thin films. The spectral line shape in Ni 2p XPS spectra shows clear differences between samples grown with and without O₂ in the plasma. These differences can be explained in terms of the observed structural changes.     

Synthesis of graphene soluble in organic solvents by simultaneous ether-functionalization with octadecane groups and reduction

Octadecane-functionalized graphene (OD-G) soluble in organic solvents was produced by combining the Hummers process for graphite oxidation and a simultaneous ether-functionalization and reduction approach with 1-bromooctadecane in pyridine and dimethylformamide (DMF). The exfoliated OD-Gs were testified to be monolayer sheets by transmission electron microscope (TEM) and atomic force microscopy (AFM). The functionalization with octadecane (OD) groups and the effective deoxygenation of graphene oxide (GO) were confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). It is proved that the effective reduction and functionalization of GO could be simultaneously completed during the refluxing process. The functionalization with OD groups can effectively prevent the aggregation of GO during the reduction.