Abstract: In this paper, the deposition and the electrical characterization of hydrogenated amorphous silicon germanium (a-SixGey:H) thin films were performed by plasma enhanced chemical vapour deposition (PECVD) at low temperature with different flow ratios of SiH4/GeH4. The temperature coefficient of resistance (TCR) and temperature dependence of conductivity were measured to study the influence of deposition parameter. The resistance uniformity were also investigated. The result showed that the film presented high TCR values of around 3.5%K-1 and moderate conductivity value of 1.47×10-3 (Ω•cm)-1 respectively at room temperature, while the non-uniformity below 5% which indicated the high resistance uniformity in films.
Abstract: Vertically aligned carbon nanotubes (VACNTs or CNTs) were synthetized by thermal chemical vapor deposition method on the Si/SiO2 substrates, using Al/Fe as catalyst. In the present study, the influence of the annealing duration and synthesis time on the length, grow rate and quality of the VACNTs according to 9 different regimes was investigated. The outcomes of the study was observed using scanning electron microscope, atomic force microscopy and Raman spectroscopy analysis was utilized in order to evaluate the quality of the obtained nanotubes. Results have shown that the length of the VACNTs increases with the rise of annealing time, however only to a certain degree, after which the deterioration of the nanotubes occurs and the reduction of their length is noticeable.
Abstract: Photogenerated electron/hole recombination greatly limits the catalytic efficiency of TiO2, and recently modification with graphene substance has been regarded as an effective way to enhance the photocatalytic performance of TiO2. When referring to the fabrication of graphene based materials, the reduction process of graphene oxide has been demonstrated to be a key step. Therefore, it is highly required to develop an efficient and simple route for the GO reduction and the formation of TiO2-reduced graphene oxide (RGO) nanocomposites. In this study, TiO2-RGO nanocomposites were prepared by a facile and efficient one-step hydrothermal method using titanium (IV) butoxide (TBT) and graphene oxide (GO) without reducing agents. This method shows several unique features, including no requirement of harsh chemicals and high temperature involved, one-step hydrothermal reaction for mild reduction of GO and crystallization of TiO2 running in parallel, and the production of TiO2-RGO nanocomposites in a green and efficient synthetic route. In addition, the photocatalytic activities of the synthesized composites were systematically evaluated by degrading methylene blue (MB) under sun light irradiation. The TiO2-RGO nanocomposites show a superior photocatalytic activity to the synthesized pure TiO2. It is also found that the concentration of RGO in the nanocomposites plays a key role in the photocatalytic activity. Specifically, the composite with 1 wt % RGO shows the best photocatalytic activity, probably due to the reduction of the electron-hole recombination rate.
Abstract: Graphene, whose structure is composed of a single-atom-thick sheet of sp2-hybridized carbon atom, provides large specific surface area, excellent mechanical and chemical properties. In this paper, reduced graphene oxide/carbon nanotube (rGO/CNT) composite, which had superior electrochemical performance, was synthesized via a facile, handy and cheap method. Electrochemical tests showed that rGO/CNT composite that the weight ratio of graphene oxide (GO) to CNTs is 7.5 to 1 exhibited the specific capacitance was 346.84 F/g at the current density of 2 A/g in 1 M H2SO4. The good performance of rGO/CNT composite was ascribed to huge surface area of rGO and homogeneous distribution of CNT, which prevented the aggregation of rGO sheets, increased the path of electron circulation and speeded up the electrolyte penetrating into the materials. Therefore, rGO/CNT composite had great potential on supercapacitors.
Abstract: In the field of Engineering and Technology, Gear is one of the most significant and essential component in mechanical power transmission system. General devices have major applications in various fields like automotives, industrial rotational machines, lifting devices, etc. Gears are usually subjected to fluctuating loads while in action. Gear tooth mainly fails due to excessive bending stress and excessive contact stress. Thus while designing the gear it is very necessary and vital to analyze the stresses induced in the gear for its safe operation. Weight reduction of gear is also one of the main design criteria as it has a great role in improving the efficiency of the entire system. Nowadays engineering components made up of composite materials and plastics find increasing applications. The components made by the composite materials provide reasonable mechanical properties with minimum weight. The objective of this research is to develop the spur gear and pinion assembly model using engineering simulation PTC Creo and imported to 3-D design software ANSYS workbench 16.0 for working on the static structural analysis. The analysis was carried out by considering different materials for gears like structural steel, polycarbonate and 20%AlSiC. From the observed results it was found that, 20%AlSiC composite material has mass reduction of about 45%, hence it is suitable for light weight applications.
Abstract: In the current scenario, there is a continuous need for increasing the efficiency of the aerodynamics of wind turbine blades through research studies. Vibration in a wind turbine blade has lot to do on its performance. An effective approach is required by wind mill including to control the vibration to achieve better results. The objective of this research is to investigate the vibration characteristics of the prototype horizontal axis wind turbine blade developed by using 3D modelling software. Shape memory alloys with their variable material properties offer an alternative adaptive mechanism hence it is used as a damping material. A prototype blade with S1223 profile was manufactured and the natural frequency was found over the surface of the blade. Similarly, results were studied by increasing the number of alloys wires over the blade up to three. Results showed that the embedment of shape memory alloys over the blade’s surface increases the natural frequency and reduce the amplitude of vibration because of super elastic nature of alloys. Also it was observed that the natural frequency increased by 6% and reduced the amplitude by about 93% where three wires of 0.5mm diameter were kept for the length of 720mm.
Abstract: In order to provide a theoretical basis for reasonable material selection in oil and gas field, according to the actual situation of a water source well, materials N80, 3Cr, H13, 13Cr and super 13Cr were selected as the research objects. The microstructure and hardness of N80, 3Cr, H13, 13Cr and super 13Cr were studied by metallographic observation and hardness test. By simulating the actual corrosion environment of the water source well, the experiment of autoclave hanging sheet and detection of corrosion products by X ray diffraction and the CO2 corrosion resistance of N80, 3Cr, H13, 13Cr and super 13Cr were analyzed. Besides, some suggestions for material selection of oil and gas wells were put forward. It is found that super 13Cr has higher hardness and CO2 corrosion resistance, 13Cr and 3Cr are second. When selecting oil and gas field water well material, it is recommended to choose super 13Cr first, then 13Cr and 3Cr.
Abstract: Utilizing submerged arc welding under heat input 50 kJ/cm on 60 mm thick marine engineering structure plate F550, the effect of preheating and post welding heat treatment on the microstructure and impact toughness of coarse-grained heat-affected zone (CGHAZ) has been investigated. The original microstructure of the steel plate is tempered martensite. The yield and tensile strength is 610 and 660 MPa, respectively. The impact absorbed energy at low temperature (-60 °C) at transverse direction reaches about 230~270 J. Welding results show that the preheating at 100 °C did not have obvious influence on the microstructure and toughness; whereas the tempering at 600 °C for 2.5 h after welding could significantly reduce the amount of M-A components in the coarse-grained heat-affected zone and thus improved the low temperature impact toughness.
Abstract: Flexible-bending is an advanced bending method, especially suitable for small batch production of tubes. The shape of forming parts is mainly related to the offset of the bend die instead of the geometry of it. Based on flexible-bending technology, 3D bending of tubes was carried out by finite element method and the effects of primary parameters on the bending results were studied. The analysis results showed that3D continuous bending of tubes can be obtained by flexible-bending process; die offset, offset speed and feeding speed of tube have a great influence on the bending effect. Bending experiments of 3D tube were carried out by flexible-bending equipment and bending radii of the forming part were measured, the results were very close to that of simulations which proved the effectiveness of simulation.