N-乙基咔唑席夫碱EDA-NECD的合成及其对Cu~（2＋）的识别研究

由N-乙基咔唑-3-甲醛（NECD）与乙二胺（EDA）合成N-乙基咔唑席夫碱化合物EDA-NECD,用IR、1 H NMR等手段表征其结构;研究各种金属离子对其荧光性能的影响,结果表明Cu2＋能显著地猝灭其荧光,而余者则几无影响;其紫外吸收峰值随着Cu2＋浓度的增加而增加,表明二者存在着化学反应。EDA-NECD有望作为重金属离子Cu2＋的荧光探针。     

Cr/Cu/Ag/Cu/Cr新型银基复合薄膜电极的防氧化性能研究

采用直流磁控溅射技术和光刻工艺制备了Cr/Cu/Ag/Cu/Cr复合薄膜及其电极,研究不同温度热处理对复合薄膜和电极结构、表面形貌和电性能的影响。Ag层与最外层的Cr层之间的Cu层不仅增强了Cr和Ag之间的粘附力,而且起到了牺牲层和氧气阻挡层的作用;Cr和Cu对Ag的双重保护使得薄膜电极在温度小于500℃时电阻率保持较为稳定,约为3.0×10-8~4.2×10-8Ω·m之间。然而由于电极表面氧化和边沿氧化的共同作用,薄膜电极的电阻率在热处理温度超过575℃出现了显著的上升。尽管如此,Cr/Cu/Ag/Cu/Cr薄膜电极仍然是一种能够承受高温热处理并且保持较低电阻率的新型电极,满足场发射平板显示器封接过程中的热处理要求。     

Influence of an additional carbon layer at the back contact-absorber interface in Cu(In,Ga)Se2 thin film solar cells

For paste-coated Cu(In,Ga)Se₂ (CIGS) absorber layers used for thin film solar cells one often gets a residual carbon layer between back contact and absorber layer. We investigate the influence of this layer on the solar cells’ performance with co-evaporated CIGS absorbers and find a beneficial effect. The power conversion efficiencies of thin chalcopyrite absorber layers are often limited by the influence of back contact recombination. It is assumed that the carbon layer between the back contact and the absorber layer helps lower this recombination and allows higher open circuit voltages and thus higher conversion efficiencies.     

Generation of electrical defects in ion beam assisted deposition of Cu(In,Ga)Se2 thin film solar cells

Thin films of Cu(In,Ga)Se₂ (CIGS) absorber layers for thin film solar cells have been manufactured on polyimide foil in a low temperature, ion beam assisted co-evaporation process.In the present work a set of CIGS thin films was produced with varying selenium ion energy. Solar cell devices have been manufactured from the films and characterized via admittance spectroscopy and capacitance-voltage profiling to determine the influence of the selenium ion energy on the electric parameters of the solar cells. It is shown that the impact of energetic selenium ions in the CIGS deposition process leads to a change in the activation energy and defect density and also in the spatial distribution of electrically active defects.For the interpretation of the results two defect models are taken into account.     

Effect of copper-deficiency on multi-stage co-evaporated Cu(In,Ga)S2 absorber layers and solar cells

Solar cell absorber films of Cu(In,Ga)S₂ have been fabricated by multi-stage co-evaporation resulting in compositional ratios [Cu]/([In] + [Ga]) = 0.93-0.99 and [Ga]/([In] + [Ga]) = 0.15. Intentional doping is provided by sodium supplied from NaF precursor layers of different thicknesses. Phases, structure and morphology of the resulting films are investigated by X-ray diffraction (XRD) and scanning electron microscopy. The XRD patterns show CuIn₅S₈ thiospinel formation predominantly at the surface in order to accommodate decreasing Cu content. Correlated with the CuIn₅S₈ formation, a Ga-enrichment of the chalcopyrite phase is seen at the surface. Since no CuS layer is present on the as-deposited films, functioning solar cells with CdS buffer and ZnO window layers were fabricated without KCN etch. The open-circuit voltage of solar cells correlates with the copper content and with the amount of sodium supplied. The highest efficiency cell (open-circuit voltage 738 mV, short-circuit current 19.3 mA/cm², fill factor 65%, efficiency 9.3%) is based on the absorber with the least Cu deficiency, [Cu]/([In] + [Ga]) = 0.99. The activation energy of the diode saturation current density of such a cell is extracted from temperature- and illumination-dependent current-voltage measurements. A value of 1.04 eV, less than the band gap, suggests the heterojunction interface as the dominant recombination zone, just as in cells based on Cu-rich grown Cu(In,Ga)S₂.     

Alternative sodium sources for Cu(In,Ga)Se2 thin-film solar cells on flexible substrates

Sodium (Na) is an important doping element for Cu(In,Ga)Se₂ (CIGS) solar cells. However, when using Na-free flexible substrates like steel foil or polyimide film, it is necessary to ensure an efficient supply of sodium to achieve high cell efficiencies. The common incorporation methods for Na on these Na-free substrates are either to deposit a Na-containing precursor layer (e.g. NaF) onto the molybdenum (Mo) back contact prior to CIGS growth or to coevaporate a Na compound during CIGS growth. Another way is to incorporate sodium after CIGS growth by a post-deposition treatment with NaF. In this work, we tested two alternative Na doping methods which are well suited for a production line due to their easy controllability. One approach is to dope the molybdenum target with Na. With Na-doped Mo layers (Mo:Na) as the back contact, we could achieve efficiencies of 13.1% both on titanium (Ti) and stainless Cr steel foil using a single-stage inline CIGS process. With a low-temperature single-stage CIGS process on polyimide (PI) we reached an efficiency of 11.2% using a Mo:Na back contact. Another doping method involves sol-gel-deposited silicon oxide layers which contain Na (SiO_x:Na). We have successfully deposited these sol-gel layers onto stainless steel foil by a roll-to-roll (R2R) method with short annealing times as needed in production. With these SiO_x:Na layers we could achieve efficiencies of 13.7% on stainless steel foil and 11.5% on mild steel sheet using a single-stage inline CIGS process.     

Failure analysis of threaded connections in large-scale steel tie rods

Steel tie rods are very important load-carrying components in applications where high levels of pre-stresses are required. The bearing capacity of a steel tie rod is determined not only by the strength of the rod body, but also by the strength of the threaded connection that resists force. Analysis of the strength of the threaded connection and determining the optimal number of turns of thread engagement is critical to ensure structural safety. This paper reports the results of full-scale tensile rupture experiments on two categories of large-scale steel tie rods provided by China JULI Corporation: (i) LG75-00 steel tie rods with triangle threaded connection, and (ii) LG100-00 steel tie rods with trapezoidal threaded connection. The full-scale tensile rupture experiments were carried out to test the maximum allowable axial working load under different numbers of turns of engaged threads. The results of these experiments suggest strong guidelines on the minimum number of turns of thread engagement for preventing the failure of thread teeth of steel tie rods in practical shear and bending applications.     

Interface between Sn-Sb-Cu solder and copper substrate

Influence of antimony and copper in Sn-Sb-Cu solder on the melting and solidification temperatures and on the microstructure of the interface between the solder and copper substrate after wetting the substrate at 623 K for 1800 s were studied. Microstructure of the interface between the solder and copper substrates in Cu-solder-Cu joints prepared at the same temperature for 1800 s was observed and shear strength of the joints was measured. Influence of the atmosphere - air with the flux and deoxidising N₂ + 10H₂ gas - was taken into account. Thermal stability and microstructure were studied by differential scanning calorimetry (DSC), light microscopy, scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD). Melting and solidification temperatures of the solders were determined. An interfacial transition zone was formed by diffusion reaction between solid copper and liquid solder. At the interface Cu₃Sn and Cu₆Sn₅ phases arise. Cu₃Sn is adjacent to the Cu substrate and its thickness decreases with increasing the amount of copper in solder. Scallop Cu₆Sn₅ phase is formed also inside the solder drop. The solid solution Sn(Sb) and SbSn phase compose the interior of the solder drop. Shear strength of the joints measured by push-off method decreases with increasing Sb concentration. Copper in the solder shows even bigger negative effect on the strength.     

Sulfur Versus Non-Sulfur Containing Polyimide Adhesives for Bonding Steel

Due to their superior thermal and chemical stability, polyimides are often used as adhesives in harsh environments. This study examines the effect on bond strength of thioether sulfur in the polyimide backbone. Bonds were made using steel that was believed to catalyze the oxidation of sulfur. In addition, non-sulfur containing polyimides with similar T_g were also studied for comparison. The polymer/metal interface was studied using both the T-peel and wedge tests. No apparent effect was observed in the T-peel test with steel where the T-peel strengths of non-sulfur and sulfur containing polyimides were similar. In the wedge test, however, the sulfur-containing BDSDA/ODA bonded to steel had the smallest initial crack length of 34 mm. However, the BTDA/APB bonds tested in a dry environment had the smallest crack growth. The sulfur-containing BTDA/ASD performed best of the bonds tested in a wet environment. Metal-catalyzed oxidation of sulfur was observed to take place in the steel case, but not to an extent to have a noticeable effect on peel strength.     

Cathodic disbonding of a thick polyurethane coating from steel in sodium chloride solution

The cathodic disbonding of a thick, pigmented polyurethane coating from steel in 3.5 wt.% NaCl solution was studied by using an electrochemical AC impedance technique. Double-cylinder electrolyte cells were designed to separate the measurements of cathodic disbonding process from the influence of the impedance of an artificial defect. It was found that for a thick, pigmented polyurethane coating, the more important transport pathway of the reactive species is along the coating/steel interface rather than through the coating. There existed a delay time for the cathodic disbonding process, and cathodic polarization was not a predominant factor in determining the cathodic disbonding behavior in the early stages. The thick polyurethane coating, which was applied on a well sand-blasted steel surface, had excellent resistance to cathodic disbonding.