Interface microstructure and diffusion kinetics in diffusion bonded Mg/Al joint

The interface microstructure, formation of diffusion bonded joint and regulation of atom diffusion were studied by means of scanning electron microscope (SEM), energy dispersion spectroscopy (EDS) and electron probe microanalyser (EPMA). The experimental results indicated that an obvious interfacial transition zone was formed between Mg and Al, and there are three intermetallic layers Mg₁₇Al₁₂, MgAl and Mg₂Al₃ in this zone. Diffusion activation energy of Mg and Al in the above layers was lower than that in the Mg and Al base metals. The thickness (x) of each layer can be expressed as x ² = 4.14exp(−28780/RT)(t−t ₀), x ² = 31.4exp(−25550/RT)(t−t ₀) and x ² = 0.6exp(−22600/RT)(t−t ₀) corresponding to Mg₁₇Al₁₂, MgAl and Mg₂Al₃ with heating temperature (T) and holding time (t).     

Comparison of depth resolution from a microscopically modulated Rh/C film after sputter profiling by SIMS and SNMS

Sputter depth profiles of an Rh/C microscopically modulated thin film (double layer thickness 7 nm) were obtained by low energy SIMS and SNMS. The depth resolution was obtained using the linear superposition of error functions at the interfaces. In optimal cases the depth resolution was shown to be of the order of 1–2 nm for both techniques.     

Optimum parameters in the SNMS high-frequency-mode for the quantitative analysis of thick, non-conducting layers

The parameter optimisation in the sputtering mode of HF-plasma SNMS for the depth-profiling of non-conducting surfaces is described. It is shown that the parameters found on a representative enamel layer are transferable to other non-conducting surfaces such as metal oxides or plastic-coated materials. The sputter rates in general amount to about 25% of the sputter rates measured on steel under the same conditions. Reducing the sputtered area by using a mask, the bombardment voltage and thus the sputter rate can be increased, resulting in an increased detection sensitivity.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Inter‐diffusion effects in as‐deposited Al/Ni polycrystalline multi‐layers

Al/Ni multi‐layers, deposited by magnetron sputtering at room temperature have been studied by complementary techniques; XPS, sputter depth profiling, electron‐induced X‐ray emission spectroscopy (XES) and X‐ray diffraction (XRD). XPS depth profile technique evidenced an atomic diffusion dominated by Ni atoms. Moreover, the Ni diffusion results in the formation of an amorphous phase with a stoichiometry close to the Al₃Ni aluminide. Copyright © 2008 John Wiley & Sons, Ltd.     

Depth profiling with SNMS and SIMS of Zn(O,S) buffer layers for Cu(In,Ga)Se2 thin‐film solar cells

Zn(O,S) is a promising candidate to replace the commonly used CdS buffer layer for Cu(In,Ga)Se₂ (CIGS) thin‐film solar cells due to its non‐toxicity and its potential to enhance the conversion efficiency of the CIGS solar cell. The composition of chemical bath deposited (CBD) and sputtered Zn(O,S) layers with thicknesses well below 100 nm was determined by sputtered neutral and secondary ion mass spectrometry (SNMS and SIMS). Despite numerous mass interferences of double‐charged atoms and dimers with single Zn, O and S isotopes, we developed an evaluation algorithm for quantification of SNMS depth profiles of Zn(O,S) layers. In particular, the superposition of double‐charged S and Zn atoms with O and S isotopes is accounted for numerically in the quantification procedure. For sputtered Zn(O,S) layers, the S/(S + O) atomic ratio and the vertical composition profile can be controlled by the O₂ content in the gas flow and the substrate temperature during sputtering whereas for CBD Zn(O,S) the S/(S + O) ratio is constant around 0.7–0.8. A Cu‐depleted layer of about 5 nm on the CIGS surface after buffer deposition was observed for both preparation methods. With negative SIMS, we found more hydroxides and carbon residues in CBD Zn(O,S) as compared to sputtered layers. Best cell performance with sputtered Zn(O,S) layers was achieved for S/(S + O) ratios of 0.25–0.40, yielding efficiencies up to 13%. Our solar cells with CBD Zn(O,S) buffers exhibit higher efficiencies due to an improved open‐circuit voltage. Copyright © 2013 John Wiley & Sons, Ltd.     

Microstructure and composition of annealed Al/Ti-metallization layers

Al/Ti multilayers with columnar grains were deposited by electron-beam evaporation on piezoelectric LiNbO₃ substrates. After annealing in air and under vacuum conditions dissolution of the Ti interlayer was observed for all samples. The original Ti interlayer dissolved completely and globular Al₃Ti grains were formed within an Al matrix. All samples had an oxidized adhesive Ti bottom layer and a 10 nm thin Al layer below this adhesive Ti bottom layer, which remains intact after the applied heat treatment. This resistance against dissolution by interdiffusion could be caused by the oxidation. These changes in the microstructure and in the chemical composition were investigated by conventional and analytical TEM.     

Analysis of composition and growth mechanisms of oxide scales on high temperature alloys by SNMS,SIMS, and RBS

Composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-5Al and an yttria containing ODS alloy with the same base composition were investigated. The alloys were oxidized in a twostage oxidation process at 1000 °C in air and air containing¹⁸O-tracer. By using secondary neutrals and secondary ion mass spectrometry in combination with RBS, the in-depth concentration of main and minor alloying elements as well as the oxygen isotope distribution in the alumina scale could be determined. It is shown, that the difficulties in deriving the exact growth processes of the scales from the oxygen tracer profiles can be overcome by using the time dependance of the iron and chromium distribution in the alumina. From these results it could be derived that growth of the oxide scales formed on the ODS and the conventional alloy mainly differ in the relative contribution of aluminium diffusion. The mechanisms which lead to these differences in scale growth phenomena will be discussed.     

Quantitative SIMS depth profiling of Al in AlGaN/AlN/GaN HEMT structures with nanometer‐thin layers

The possibilities of quantitative secondary ion mass spectrometry (SIMS) depth profiling of Al in AlxGa1 ? xN/AlN/GaN transistor heterostructures are shown. Using a series of test structures for a TOF.SIMS‐5 time‐of‐flight mass spectrometer, we obtained a refined linear calibration dependence of the secondary‐ion yield on the composition ×, namely, Y(CsAl+)/Y(CsGa+) = K × x/(1 ? x), with a high linear correlation coefficient, Rl = 0.9996, which permits quantitative SIMS analysis of relatively thick AlGaN barrier layers. The method of profile reconstruction with allowance for the main artifacts of ion sputtering has been first applied for the analysis of GaN/AlGaN/AlN/GaN high electron mobility transistor structure. This method permits to perform quantitative analysis of the thickness and composition of a nanometer‐thin AlN sublayer and to estimate the measurement error. For the structure being studied, the AlN sublayer is 1.2 ± 0.2 nm thick. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface characterization and depth profiling of biological molecules by electrospray droplet impact/SIMS

Electrospray droplet impact (EDI) was applied to the analysis of peptides. The etching rate of bradykinin was estimated to be ~2 nm/min. This value is about one order of magnitude greater than the etching rate for SiO₂ (0.2 nm/min). Considering that the etching rate of argon cluster ions Ar₇₀₀⁺ for organic compounds is more than two orders of magnitude larger than that for inorganic materials, the rather small difference in etching rates of EDI for organic and inorganic materials is unique. When water/ethanol (1/1, vol%) solution of gramicidin S and arginine was dried in air, [gramicidin S + H]⁺ was observed as a predominant signal with little [Arg + H]⁺ right after the EDI irradiation, indicating that EDI is capable of detecting the analytes enriched on the sample surface. Copyright © 2011 John Wiley & Sons, Ltd.     

室温液相还原法制备纳米Pt/Al2O3催化剂及其催化性能的研究

在室温条件下利用甲醛还原法，制备了Pt粒径可控纳米颗粒并担载于γ-Al2O3载体上的Pt／γ-Al2O3催化剂．利用甲醇重整反应为探针反应．考察了Pt粒径与催化反应性能之间的关系，发现催化反应的性能与担载贵金属粒径之间存在明显的相关性．结合透射电镜(TEM)表征结果与甲醇水蒸气重整(SRM)性能．发现纳米Pt的粒径大小不但影响甲醇重整反应的活性．同时也影响反应的选择性，即催化剂的性质与担载贵金属粒径之间存在明显的尺度效应．     

Pt/Al2O3和Pt-Cu/Al2O3催化CCl4氢化脱氯反应

制备了Al2O3负载Pt单金属催化剂和负载Pt-Cu双金属催化剂,比较了二者不同还原温度对其催化CCl4氢化脱氯反应性能的影响。 单金属Pt催化剂上主要生成CHCl3,而双金属Pt-Cu催化剂上产物随催化剂制备时的还原温度不同而异,当催化剂经400 ℃用H2还原后产物主要为CHCl3,而当催化剂经800 ℃用H2还原后产物主要为CCl2CCl2。 由于CCl4氢化反应是强放热反应,催化剂表面局部过热使得在反应中生成的C2等产物聚合结焦,覆盖了催化剂的活性中心,导致催化剂失活。 因此,通过加入甲醇作为稀释剂以带走部分反应热可提高催化剂的稳定性。 同时也降低了CHCl3的选择性,提高了CCl2CCl2的选择性。     

Activity Enhancement of Pt/Ba/Al2O3 Mixed with Mn/Ba/Al2O3 for NOx Storage-reduction by Hydrogen

The storage and reduction of nitrogen oxides has attracted much attention as an efficient way to reduce NOx emission of lean-burn gasoline and diesel engines1-5. At present, NOx storage and reduction (NSR) catalysts based on Pt and Ba have been extensivel…     

TPD study of NH3 adsorption/desorption on the surface of V/Ti, V/Al based catalysts for selective catalytic reduction of Nox by ammonia 2. TPD test of commercial V/W/Ti, V/Al, Pd/V/Al catalysts

The effect of temperature on the adsorption/desorption of ammonia from the air mixture on the surface of commercial binary V/Al and ternary Pd/V/Al, V(0.65 wt.%) /W(6.73 wt.%) /Ti and V(1.8 wt.%) /W(7.3 wt.%) /Ti de-NO_x catalysts has been investigated by temperature-programmed desorption (TPD) method. The ability of the commercial catalysts to adsorb ammonia in the most stable surface species was shown to correlate well with their suppression of the NH₃ oxidation.     

Comparative study on electrochemical degradation of 4-chlorophenol by different Pd/C gas diffusion electrodes

Pd/C catalyst used for the Pd/C gas diffusion cathodes was prepared by hydrogen reduction method and formaldehyde reduction method, and characterized by X-ray diffraction (XRD), transmission elec- trode microcopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) tech- niques. The electrochemical degradation of 4-chlorophenol was investigated in the diaphragm elec- trolysis system, aerating firstly with hydrogen gas then with air, using three different kinds of gas dif- fusion cathode. The results indicated that the self-made Pd/C gas diffusion cathode can not only re- ductively dechlorinate 4-chlorophenols by aerating hydrogen gas, but also accelerate the two-electron reduction of O2 to hydrogen peroxide (H2O2) by aerating air. Therefore, the removal efficiency of 4-chlorophenol by using Pd/C gas diffusion cathode is better than that of the C/PTFE gas diffusion cathode (no catalyst). The catalytic activity of Pd/C catalyst prepared by hydrogen reduction method is higher than that prepared by formaldehyde reduction method. The stability of the Pd/C gas diffusion cathodes is good. Therefore, both the removal efficiency and the dechlorination degree of 4-chlorophenol reached about 100% after 60 min, and the removal efficiency of 4-chlorophenol in terms of chemical oxygen demand (COD) in the cathodic compartment reached 87.4% after 120 min.     

KF/Al2O3催化下取代水杨醛与达米酮的反应

取代水杨醛与5,5-二甲基-1,3-环己二酮(达米酮)在KF/Al2O3催化下反应生成一系列苯并吡喃的衍生物.产物的结构通过红外光谱、核磁共振氢谱和元素分析进行表征,并通过X单晶衍射分析进一步证实产物的结构.     

Characterization of oxide layers on Ti6Al4V and titanium by streaming potential and streaming current measurements

Titanium and titanium alloys (e.g. Ti6Al4V) are increasingly used as medical implant materials in a wide variety of applications. So far, many surface properties of the passive layer considered to explain interactions with biological tissues are deduced from those of the crystalline phases of titanium dioxide (anatase, rutile, brookite), but do not necessarily correspond to those of naturally formed amorphous passive layers. We report on streaming potential and streaming current measurements on oxide layers on Ti6Al4V and Ti, carried out using a microslit electrokinetic set-up (MES) and a commercial electrokinetic analyzer (EKA, PAAR). Passive and anodic oxide layers on Ti6Al4V, as well as passive layers on titanium sputtered on glass, were investigated in this study. Isoelectric points (IEP) of ≈4.4 were found for all oxide layers. The IEP of the air-formed passive layer on Ti6Al4V did not depend on the KCl concentration. Hence, it was concluded that IEP is here identical to the point of zero charge (pzc). Controversially, the charge formation process seems to depend on the chloride ion concentration in the neutral and basic pH region.     

Li-KCl熔融界面上离子扩散的分子动力学研究

采用分子动力学(MD)方法研究了熔融Li(电极)-KCl(电解质)界面上离子的扩散行为。熔融界面上离子的扩散动力学通过离子质心的均方位移(MSD)和速度自相关函数(VACF)进行研究,扩散系数由MSD(t)函数线性区间的斜率和VACF(t)函数积分得到。模拟结果表明,在熔融的Li-KCl界面上,Li+离子在浓度梯度的驱动下穿过界面发生定向迁移,导致双电层的形成和外电路上电流的输出。Li+离子的扩散系数比K+和Cl-离子的大7～8倍,说明在界面上Li+离子是主要的载荷子,热电池的电荷传输机制主要与Li+离子的扩散运动有关。由Nernst-Einstein公式对电导率进行估算,由扩散到KCl层中的Li+离子产生的电导率约为0.4 S.cm-2,对应的电流密度估算值为3.27×105A.cm-2。     

微波辐射I2／Al2O3催化合成腈类化合物

微波辐射下,I2/Al2O3催化芳香醛和盐酸羟氨的无溶剂反应.一锅法合成了腈类化合物,产率80%～99%.     

碳酸二甲酯在锌铝复合氧化物上分解行为的红外研究

采用尿素热分解法制备锌铝水滑石,1 073 K下煅烧得到相应的锌铝复合氧化物催化剂。通过XRD谱图确定锌铝复合氧化物ZAO-3(1 073 K)催化剂的组分为ZnO相和ZnAl2O4尖晶石相。NH3(CO2)-TPD结果表明,当向ZnO中引入Al后,催化剂的酸碱性位和酸碱性强度都发生改变。采用原位红外(in-situ FT-IR)手段,研究了碳酸二甲酯(DMC)分别在ZAO-3(1 073 K)、ZnAl2O4、ZnO上随着温度变化的分解行为。结果表明,ZAO-3(1 073 K)催化剂上大量的弱酸碱性位协同稳定DMC,抑制DMC的分解。     

三乙醇胺改性Cu/Zn/Al类水滑石衍生氧化物催化合成气制备低碳醇

采用共沉淀法制备Cu/Zn/Al类水滑石前驱体,并用配体三乙醇胺(TEA)对其进行改性。前驱体经焙烧后成功获得TEA改性的Cu/Zn/Al催化剂。借助XRD、FTIR、H2-TPR、CO-TPD及SEM等方法对催化剂进行表征,并将其应用于合成气制备异丁醇的活性评价反应中。结果表明,TEA的加入能够改变催化剂形貌,使催化剂表面呈松散絮状结构。TEA可使类水滑石前驱体的结构发生膨胀,其焙烧获得的催化剂中有明显的晶格扭曲和晶格缺陷。TEA对催化剂结构的改变有利于Cu/Zn/Al催化剂中CuO组分的氢还原和CO在催化剂表面的化学吸附,从而促进异丁醇的合成。当TEA的添加比例为nTEA/nZn=0.5时,TEA改性的Cu/Zn/Al催化剂的催化效果达到最佳。