Spray deposited Nb2O5 thin film electrodes for fabrication of dye sensitized solar cells

Nb₂O₅ thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis technique. XRD analysis reveals tetragonal phase of the film. Reticulated micro-fibrous surface morphology has been observed by scanning electron microscopy and atomic force microscopy indicates closely packed crystallites. Film thickness found using a stylus profilometer is around 26 nm. Transmittance spectra show the film to be 70–80% transparent in the visible region. Direct, indirect band gap and phonon energy are also estimated. Cyclic voltammetry measurement indicate distinct anodic peak during negative potential of the scan due to Li extraction. A reversible colour change from transparent to grey has been observed. The photo-electrochemical characteristic of the dye sensitized solar cell is studied by recording the I-V characteristics of the unsealed type cell under illumination of 40 mW/cm² using a solar simulator.     

Synthesis of gadolinium aluminate thin film by ion beam sputtering sequential deposition

Sequentially deposited by thin film synthesis consisted of multilayer precursor film deposition and thermal treatment. It is especially useful in complex-ingredient or precise stoichoimetric controlling thin film synthesis. Gadolinium aluminate,a new good candidate system for many luminescence usages other than laser crystals,scintillation crystals,phosphors,contains many phases,such as Gd4Al2O9(GAM) ,GdAlO3(GAP) ,Gd3Al5O12(GAG) ,so precise stoichoimetry of the amorphous ingredient layers is very important to the final single phase film synthesis. In our work,Gd2O3 and Al amorphous layers(ingredients for gadolinium aluminate film) were deposited in a certain sequence on MgO(100) and Si(100) substrate by IM100(an ion beam sputtering instrument) . The multi-amorphous-layered precursor was annealed with two-step thermal treatment(diffusion at a low temperature and then crystallization at a high temperature) . The XRD(X-ray diffraction pattern) ,SEM(scanning electron microscope second electron image) and AES(Auger electron spectroscopy depth profiles) analyses were used to detect the film microstructures and properties. The analyses results showed that ion beam sputtering deposition could control ingredient stoichoimetric ratio by an in site depositing thickness measurement. During the two-step thermal treatment,diffusion at a low temperature would cost a rather long time to make the amorphous precursor film uniform(more than 120 h) ,and the suitable diffusion temperature should be around 400 oC. The crystallization temperature should be decided by the gadolinium aluminate phase types and cost rather less time(about 4 h) . The stable phases GAP and GAM should be annealed at 1300 oC or higher temperatures,but the metastable phase GAG should just be annealed at around 1100 °C.     

On Microscopic Origin of Photovoltaic Effect in La0.8Sr0.2MnO3 Films

Theperovskitemanganitehavebeeninvestigated becauseoftheirinterestingpropertiesfullofvariety,includingferromagnetism,antiferromagnetism,metal insulatortransition,highTCsuperconductivity,colos salmagnetoresistanceandsoon,dependingonthe carrierconcentrationd…     

带钢氧化膜受压断裂实验及数值分析

为了研究拉矫破鳞过程中,压应力对氧化膜剥落的作用,建立了氧化膜的薄板模型,推导出氧化膜长度与临界荷载之间的关系,利用差分法理论计算出失稳条件下的临界荷载公式。模型中的材料参数氧化膜弹性模量由纳米压痕实验测得为145GPa,基体与氧化膜的结合力系数由拉伸实验测得为18.2MPa/m;利用拉矫破鳞机对带钢施加100、150、200MPa的压应力作用,通过金相实验观察统计出断裂后的残余长度,并与理论计算的残余长度进行对比,验证得到拉矫破鳞实验得出的断裂长度与差分法理论计算出的残余长度的结果相差小于12%。研究表明氧化膜受压断裂,理论推导出的临界残余氧化膜长度与实际受压断裂氧化膜长度相近;临界荷载公式表明压应力与残余氧化膜最大长度呈平方反比关系。     

氮化过程中Ti薄膜的电子结构分析

建立不同类型的原子团簇模型,利用电荷自洽离散变分法计算了Ti薄膜中不同晶体结构的原子间化学键键能,分析了薄膜中晶体的局域态密度和全态密度,探讨了其电子结构和Ti-N原子间的交互作用变化.结果表明,N原子占据八面体间隙中心位置后,强Ti-N键的形成和原有Ti-Ti键的弱化,促使hcp-Ti中(00.1)面上的Ti原子沿着<01.0>方向发生迁移,成为hcp-fcc相变中fcc-Ti亚晶格形成的根源.随着进入hcp-Ti晶格中N原子数的增多,Ti-N结合键数目增加,N 2p/Ti 3d-4p杂化价电带的电子密度也随之增大,Ti的外层电子平均能量降低,保证了fcc-TiNy的稳定生长.     

Growth and configurational stability of circular,buckling-driven film delaminations

A study is presented of delamination at the interface between a thin elastic film bonded to a substrate under conditions in which the film is subject to equi-biaxial compression. The focus is on initially circular delaminations. When the initial delamination is sufficiently large it buckles away from the substrate producing a blister which in turn induces a driving force on the interface crack tip. A two-part theoretical analysis of the coupled buckling/fracture problem is conducted: the axisymmetric growth of the circular blister, and the stability of the circular blister to nonaxisymmetric perturbations of the interface crack front. A simple criterion is identified which excludes the possibility of wide-spread delamination. Experiments are reported for a model film/substrate system (mica bonded to aluminum) chosen to allow visualization of the interface and to permit compressive stresses in the film to be generated over the full range of interest by exploiting the large thermal expansion mismatch of the system. The experiments bear out the theoretical prediction of a regime of axisymmetric growth which gives way to nonaxisymmetric blisters after a blister becomes sufficiently large. The study suggests that the wavy-circular and worm-like blister morphologies which are usually observed for delaminated films are a manifestation of the configurational instability of the interface crack front.     

Synthesis of gadolinium aluminate thin film by ion beam sputtering sequential deposition

Sequentially deposited by thin film synthesis consisted of multilayer precursor film deposition and thermal treatment. It is especially useful in complex-ingredient or precise stoichoimetric controlling thin film synthesis. Gadolinium aluminate, a new good candidate system for many luminescence usages other than laser crystals, scintillation crystals, phosphors, contains many phases, such as Gd₄Al₂O₉(GAM), GdAlO₃(GAP), Gd₃Al₅O₁₂(GAG), so precise stoichoimetry of the amorphous ingredient layers is very important to the final single phase film synthesis. In our work, Gd₂O₃ and Al amorphous layers (ingredients for gadolinium aluminate film) were deposited in a certain sequence on MgO (100) and Si (100) substrate by IM100 (an ion beam sputtering instrument). The multi-amorphous-layered precursor was annealed with two-step thermal treatment (diffusion at a low temperature and then crystallization at a high temperature). The XRD (X-ray diffraction pattern), SEM (scanning electron microscope second electron image) and AES (Auger electron spectroscopy depth profiles) analyses were used to detect the film microstructures and properties. The analyses results showed that ion beam sputtering deposition could control ingredient stoichoimetric ratio by an in site depositing thickness measurement. During the two-step thermal treatment, diffusion at a low temperature would cost a rather long time to make the amorphous precursor film uniform (more than 120 h), and the suitable diffusion temperature should be around 400 °C. The crystallization temperature should be decided by the gadolinium aluminate phase types and cost rather less time (about 4 h). The stable phases GAP and GAM should be annealed at 1300 °C or higher temperatures, but the metastable phase GAG should just be annealed at around 1100 °C.     

Mechanical measurements of passive film fracture on an austenitic stainless steel

The initiation of fracture in passive films formed on a 304 stainless steel has been measured using a nanoindentation technique as well as bulk circumferentially notched tensile bars (CNTBs). The nanoindentation method was coupled with scanning probe microscopy to isolate individual grains that were free of any observable inclusions, so as to probe only the properties of the film upon the base alloy. The mechanical response of the film was measured while being anodically polarized in 0.1 M sulfuric acid with various halide concentrations, as well as with respect to the applied potential. The passive film strengthened as the applied potential increased in the passive regime, possibly due to film-thickness changes. In both the bulk and nanoscale tests, the passive film-fracture strength was found to decrease with increasing salt concentration in solution, which cannot be attributed to the uniform thinning of the passive film. The correlation between the bulk and nanoscale tests demonstrates that both methods are viable options of measuring the fracture of passive films on metals. Nanoindentation results are used to estimate the applied tensile stress at film fracture between 1 and 2 GPa for an anodically grown passive film on 304 stainless steel at 0 V vs that on Ag/AgCl in 0.1 pct NaCl-0.1 M sulfuric acid.     

High quality thin film phosphors of Y2O3:Eu3+ deposited via chemical bath deposition

High transparency in visible region was required for red-light-emitting Y2O3:Eu3+ thin film phosphors. Such films were obtained via chemical bath deposition on bare SiO2 glass substrates through heterogeneous nucleation with further heat treatment. Thin amorphous yttrium basic carbonate films could be completely transformed to crystalline Y2O3 at 650 °C. X-ray diffraction and field-emission scanning electron microscopy were used to characterize these products. The deposition temperature and the post-anneali...     

Surface-alloy formation in film–substrate melting by intense pulsed electron beam. Part 2

The elemental and phase composition and defect structure of the surface layer on 5140 steel is considered after alloying by melting of a film–substrate (5140 steel) system under irradiation by intense pulsed electron beam; the film consists of aluminum or titanium. Treatment of the titanium–5140 steel system results in alloying to the depth of the molten layer (about 15 μm); polycrystalline structure (with submicron grains) based on α-phase hardened by titanium-carbide nanoparticles is formed. For the aluminum–5140 steel system, only a thin surface layer (about 2 μm) is alloyed, on account of the evaporation of aluminum from the steel surface. Martensit structure hardened by iron-aluminide nanoparticles is formed.     

微区电化学技术在薄液膜大气腐蚀中的应用

薄液膜大气腐蚀的本质是吸附于金属基体表面的水汽形成薄电解质液膜引起的金属腐蚀现象.由于液膜很薄,无法满足常规的三电极溶液测试体系要求,使得微区电化学技术在该领域得到广泛的应用.本文对比分析了用于薄液膜大气腐蚀的电化学测试技术,着重介绍了扫描Kelvin探针、丝束电极、微液滴电极等测试方法在薄液膜大气腐蚀研究中的应用,并通过总结测试中涉及的关键参数揭示了薄液膜/液滴尺寸与腐蚀动力学过程的关系.最后提出了微区电化学方法在该领域应用目前存在的问题以及今后可进一步提升的可能.      

Metallographic aspects of thick film technology

?Thick film technology” traces its ancestry to three sources: the preparation of decorative ceramic glazes, the fabrication of ceramic-to-metal seals, and the development of evaporated or sputtered “thin films” for electronic applications. Today, “thick films” are often the most reliable and also the cheapest route for satisfying numerous requirements in the functional packaging of semiconductor devices, and in related areas in microelectronics. The technology of thick film developments is heavily oriented toward problems related to multiphase structures and to interfaces. Typical thick films are essentially glass/metal composites, similar to the “cermets” which were so popular about a decade ago in attempts to develop structural materials for high temperatures. Micrographs and electron microprobe tracings will be shown to illustrate typical structures, and the defects occurring in them. Soldering, brazing, thermocompression bonding, ultrasonic bonding, eutectic die bonding, and several variations of these techniques are used for attaching devices and/or input-output connections to ceramic substrates via thick films. The interface problems associated with the sequential bonds generated in such processes are of great interest in the development of thick film compositions.     

Immunoelectrodes in protein detection: comparison between glassy carbon and a semimetallic Ni/P thin film as binding support. Biological applications

Though immunoelectrodes can allow direct detection of very low protein amounts (about 0.1 pmol) in vitro and in vivo, they are not yet widely used because they need quality improvement. Based on a few works devoted to the basic electrochemical phenomenon occurring when antibodies are linked onto a solid support and during antigen/antibody complex formation, we have coated two different supports with antibodies: the classical glassy carbon fiber or an epoxy plate covered with an amorphous semimetallic (nickel/phosphorus) thin film obtained by means of an electrochemical deposit. The antibody/antigen complex formation induces direct and/or indirect ionic movements and a current flow through the conductive support toward a very low-noise and high-sensitivity preamplifier stage in an I/V configuration. The proposed electrochemical treatment (hydrophilization), applied to both carbon and Ni/P electrodes, improves antibody binding and reliability of the response to antigens. The Ni/P probes present several advantages when compared to carbon fiber: better conductivity, possibility of surface quality control, and semimetallic nature, making them unbreakable. Several applications were proposed: somatostatin-14 detection with both carbon fiber and Ni/P plate electrodes, and histamine detection in simple and complex fluid media. Dose-response curves and analysis of the results lead us to conclude that the obtained currents are directly related to the quantity of antigen.     

Rate effects in metal-ceramic interface sliding from the periodic film cracking technique

The periodic film cracking technique [Agrawal and Raj, Acta metall.37, 1265 (1989)] was used to characterize sliding mechanisms at the copper-silica interface of silica films on a copper substrate at temperatures up to 550°C and at strain-rates ranging from 1.7 × 10⁻³ to 1.6 × 10⁻⁵s⁻¹. Two regimes of behavior were observed. The sliding was strongly rate sensitive in the high temperature/low strain-rate regime, with a power law stress component of n = 1.00 ± 0.04. At low temperatures and/or high strain-rates, the crack-spacing was strain-rate independent. These results, when analyzed in terms of the global mechanisms of deformation in crystalline materials, lead to the following interesting ideas: (a) the diffusional accomodation mechanism of sliding which assumes that diffusional transport can be applied to sliding at a wavy metal-ceramic interface shape, is consistent with the phenomenology of the strain-rate sensitive regime; (b) the non-linear power law creep mechanism (n ≈ 4.5) is not observed for deformation near the interface, presumably because the width of the deformation zone near the interface is smaller than the characteristic subgrain size required in power law creep; (c) in the low temperature regime, interface sliding occurs by dislocation slip in the metal at or near the interface. We extend the concept of “deformation mechanism map” first introduced for bulk crystalline materials by Ashby [Acta metall.20, 887 (1972)] to sliding at metal-ceramic interfaces.     

Magnetic and magnetostrictive properties of amorphous TbFe/FeAl multilayer thin film

Exchange coupling multilayer thin films, which combined giant magnetostriction and soft magnetic properties, were of growing interest for applications. The TbFe/FeAl multilayer thin films were prepared by dc magnetron sputtering onto glass substrates. The microstructure, magnetic, and magnetostrictive properties of TbFe/FeAl multilayer thin film was investigated at different annealing temperatures. The results indicated that the soft magnetic and magnetostrictive properties for TbFe/FeAl multilayer thin film compared with TbFe single layer film were obviously improved. In comparison with the intrinsic coercivity JHc of 59.2 kA/m for TbFe single layer film, the intrinsic coercivity JHc for TbFe/FeAl multilayer thin films rapidly dropped to 29.6 kA/m. After optimal annealing (350 ℃×60 min), magnetic properties of Hs=96 kA/m and JHc=16 kA/m were obtained, and magnetostrictive coefficient could reach to 574×10-6 under an external magnetic field of 400 kA·m-1 for the TbFe/FeAl multilayer thin film.     

生产低碳钢管在穿孔顶头表面形成氧化膜的方法

在小型穿孔机组上生产热轧无缝钢管时,穿孔顶头会因塌鼻、黏钢、缺肉、开裂等四种原因失效。在高温弱氧化气氛下,通过生产少量低碳钢可以在穿孔顶头表面生成一层主要成分为FeO、Fe3O4的氧化薄膜。由于氧化膜具有低导热系数及在高温下软化的特性,因而可以起到隔热、润滑的作用,从而降低顶头表面温度,提高基体强度,并阻止热焊合。这将延缓黏钢、缺肉失效的发生,从而能够有效提高穿孔顶头的使用寿命。该技术已运用于宝钢股份精密钢管厂,可完全利用现有的设备,成本低廉,容易推广使用。     

Behavior of oxide film at the interface between particles in sintered Al powders by pulse electric-current sintering

The microstructure of the bonding interfaces between particles in aluminum (Al) powder sintered specimens by the pulse electric-current sintering (PECS) process was observed, using conventional transmission electron microscopy (CTEM) and high-resolution transmission electron microscopy (HRTEM). The behavior of oxide film at the interface between Al particles and its effect on properties of the sintered specimens were investigated. The results showed there were two kinds of bonding interfaces in the sintered specimens, namely, the direct metal/metal bonding and the metal/oxide film layer/metal bonding interface. By increasing the fraction of the direct metal/metal bonding interfaces, the tensile strength of the sintered specimens increased, and the electrical resistivity decreased. By increasing the loading pressure at higher sintering temperatures or increasing the sintering temperature under loading pressure, the breakdown of oxide film was promoted. The broken oxide film debris was dispersed in aluminum metal near the bonding interfaces between particles.     

化学溶液沉积法制备Ca_3Co_4O_9热电薄膜材料研究

本次实验制备了不同的前驱液,分别利用旋涂法及超声雾化法成功地在SiO2/Si衬底上生长出了Ca3Co4O9热电薄膜.利用XRD检测技术对薄膜样品进行了物相分析,用金相显微分析技术分析了薄膜的表观相貌.实验结果表明,在SiO2/Si衬底生长出的Ca3Co4O9薄膜具有一定的择优取向,雾化法制备的薄膜样品具有较好的表观质量.     

超级电容器用羧基氧化钌薄膜的充放电性能

以RuCl3.3H2O异丙醇溶液为前驱体,分别加热到250、270、300和400℃制备超级电容器用羧基氧化钌薄膜。借助红外光谱仪、扫描电镜、透射电镜和电化学分析仪等手段,研究薄膜的物相结构、微观形貌和电容性能。结果表明:经270℃保温2 h处理后,薄膜的成分为羧基氧化钌。随热处理温度升高,薄膜的比电容逐渐降低,快速充放电性能提高。薄膜的比表面积为88 m2/g;薄膜的比电容达到859 F/g,附着力为20.13 MPa,16 000次循环充放电后比电容保持在充放电循环前的99.7%。     

Synthesis of nanocomposite thin films based on the Mo-Si-C ternary system and compositional tailoring through controlled ion bombardment

A major advantage of sputtering processes compared to evaporation processes is the possibility of synthesizing films that replicate the composition of the source (target) material,particularly in the case of alloy targets. This is related to the unique feature of sputtering, viz, formation of an “altered layer” which facilitates reproduction of the target composition in the thin film. An exciting and novel area of research deals with the synthesis of nanocomposite thin films by sputtering composite targets. In this article, the feasibility of depositing a composite thin film based on the Mo-Si-C temary system through RF magnetron sputtering of a MoSi₂+XSiC target, and the possibility of modifying the film composition by controlled ion bombardment (i.e., “ion plating” or “bias sputtering”), will be discussed. In this context, the role of the sputter yields for Mo, Si, and C will be examined with respect to the ability to vary the composition of as-deposited films. In addition, the modifications which were required to sputter a 58.4-mm-diameter composite target (produced inhouse, by different synthesis reactions) using a 127×381-mm Vac Tec cathode will be discussed. Details of Auger electron spectroscopy (AES) scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses of the as-deposited films will be presented.