Advanced Materials Research Vols. 189-193

Abstract: This paper presents a novel bonding-free process for fabricating integrated microfluidic devices with embedded electrodes utilizing low-cost UV curable resins. Commercial available UV glue is sandwiched between two substrates and is used for both the structure material and bonding adhesive. The pattern of micro-fluidic channels is defined using a standard lithography process while two substrates are bonded simultaneously during the exposure procedure. Once the pattern is defined, the un-cured UV glue was removed by vacuum suction to form the sealed microfluidic channel. With this simple approach, conventional bonding processes can be excluded for fabricating sealed microfluidic structures such that the developed method is essential for fabricating microchip devices with embedded electrodes. The thickness of the formed structures can be up to millimeter range and the smallest channel width is around 80 um (aspect ratio = 2). The overall process to fabricate sealed microchip device is less than 10 min since no time-consuming etching and bonding process in the developed process. An innovative micro-reactor integrated with in-channel micro-plasma generator for real-time chemical reaction analysis is fabricated using the developed process. On-line mass-spectrum (MS) detection of an esterfication reaction is successfully demonstrated, resulting a fast, label-free, preparation-free analysis of chemical samples. The developed process has shown its potentials for rapid and low-cost microdevice manufacturing.

Abstract: Based on the finite element analysis software ABAQUS, a sequentially coupled fillet welding thermal-stress calculation program was developed to simulate the plate close welding structure. The welding temperature fields and the stress/strain distributions of plate sealing joint of the hydrogenation heat exchanger were obtained. The simulation results showed that there existed higher stress near the fillet weld sealing joint zone and the maximum stress at the start welding point, the plastic strain of the weld joint was lager and a strain mutation occurred on the weld overlay .The analysis of the calculation result provides theory references for controlling the welding residual stress and it’s of great significance to improve the reliability and safety of hydrogenation heat exchanger.

Abstract: Taking pipe - hollow spherical node as the object, and using ANSYS finite element analysis software, established five kinds of finite element model to analyze the stress concentration at the weld connection of the different connections of steel structures - hollow ball under the uniaxial tension. Obtained this node’s stress concentration factor, stress distribution, by changing the hollow spherical diameter and wall thickness, pipe’s diameter and wall thickness, obtained the trend of the stress concentration factor under different control ball matches. Take static tests on typical structures of two specifications 6 hollow sphere nodes, get the measured stress concentration factor, and stress distribution of this node. Through comparative analysis of theoretical analysis and experimental results, show that the two rules are consistent. The research results can provide basis for improving the pipe - hollow spherical joints connecting structural.

Abstract: A low-temperature controllable chemical bath deposition (CBD) method was demonstrated to prepare ZnO nanorod arrays. Our deposition technique includes the seeding and subsequent main CBD growth. The uniform growth ZnO nanorod arrays on the condensed ZnO seeding layer could be controlled by changing the processing parameters. Experiment results reveal that the ZnO nanorod arrays prepared under 0.03-0.05 M concentration with reaction temperature of 95 °C demonstrate the well-aligned orientation and optimum optical properties with high aspect ratio of ~21. The n-ZnO/p-NiO heterojunction electrode shows excellent rectifying behavior with extremely low leakage current. After the sensitization with N719, it is found that the degree of orientation and aspect ratio value play critical roles in the photovoltaic properties of solid-state dye-sensitized solar cells (SS-DSSCs).

Abstract: Thermal anchor is one of the key components in ITER magnet supports to maintain the low temperature for superconductor coils. The sufficient attachment of the cooling pipe to the support plates is needed to minimize the risk of helium leakage. Brazing is one of the best choices. Three kinds of special brazing filler, including SnPb brazing filler, Ag-based and Cu-based brazing filler, were developed, which have good thermal conductivity, and toughness for brazing connection of SS 316LN at both room temperature and 77K environment. Some brazing technologies, including induction brazing, vaccum brazing, fire brazing, and arc brazing, have being investigated.

Abstract: Polymer-based anisotropic conductive film has become widely used in many electronic packaging interconnect applications. In this study, thermosonic flip chip bonding technology for anisotropic conductive film (ACF) joints of chip-on-glass (COG) assembly is investigated. The effects of ultrasonic power on the curing degree and bonding strength of anisotropic conductive film joints are discussed. The results show that (1) The bonding strength of the ACF joints firstly increases and then fast decreases when the ultrasonic power is continuously increased; (2) The curing degree of ACF material increases with the increase of the ultrasonic power. When the ultrasonic power is 3.52W, the curing degree of ACF material can reach 94.1%; (3) The optimized value of ultrasonic power is 3.5W for the studied assembly.

Abstract: Butt laser welding experiments of Q235 sheets in different parameter conditions are conducted, and residual deformation values of the samples are measured. To predict welding deformation, heat transfer analysis is first done by FEM to obtain corresponding quasi-steady temperature data; then an equivalent model is constructed based on temperature and inherent strain theory, and bending moment values are reversely calculated through specific measured deformation values by static analysis, which are verified by a series of process experiments. In the end, the established equivalent model is applied to predict welding angular deformation of the I-beam structure. It is shown that the proposed method has a high accuracy and efficiency.

Abstract: Commercial catalyst of CuO/ZnO/Al₂O₃ was used as feedstock to coating fabrication for hydrogen production through fuel reforming on aluminum plate. Microstructure and micro-region composition of the coatings were analyzed by SEM and EDX. It was found that the composition of feedstock and coating was basically the same; Bonding between the particles in the coating and the bonding between the coating and substrate was mainly belonged to mechanical bite and physical bonding; At low heating temperature in spraying, the coating presented applanation loosen cascade state of porous structure; Morphology of the coating influenced by heating temperature and fracture character of the particles; Methanol steam reforming reaction on the coating confirmed that cold spray technology can be successfully applied to fabrication of catalytic coating material.

Abstract: Air diving are widely used in many shallow water areas, if applicable welding technology adaptive to such a condition developed, then operation cost of offshore structure repairs can be largely saved. In order to meet such a special requirement, an automatic GTAW welding process under high air pressures was researched. Firstly, the hyperbaric welding test chamber was designed and constructed in laboratory, and the welding machine was manufactured. Secondly, experiments under 1-7 bar air pressures were studied including linear welds and pipe butt welds, and high weld quality was obtained. Lastly, the hyperbaric welding sea-trial was carried out, and perfect 5G girth weld of sub-sea pipelines was produced.

Abstract: A new style of emergency welding, named manual SHS welding ,was introduced. By this technique, metal materials could be welded on the condition of no electricity, no gas and no equipments. In this paper, the mechanism of manual SHS welding has been illustrated, the effect of thermit on welding and the microstructure of the welded joint have been studied, and the mechanical properties have been tested. Results showed that the combustion velocity of the combustion welding rod became higher when the content of (CuO+Al) thermit increased. The suitable (CuO+Al) content is 60%wt ~80%wt. The tested 45 steel plates were one-side welded with back formation. Microstructure analysis indicated that there are three zones in the welded joint, which are heat affected zone, fusion zone and weld metal. The weld metal and the 45 steel plates were combined metallurgically. The weld metal was copper based alloy. EDS patterns showed that there was diffusion of Cu, Fe and Ni in the three zones. The fracture of the weld joint is a typical ductile fracture. The tensile strength of the joints reached 400MPa and the impact absorbed energy was about 35J, which meet the requirement of mechanical properties for emergency welding. Manual SHS welding is an effective welding method for emergency maintenance in battlefield and outside field.