Applied Mechanics and Materials Vol. 590

Abstract: Y is used as a dopant for the first time in preparing conductive powders to improve its performance. Y and Sb doped SnO₂ conductive particles are prepared by the complexation-coprecipi-tation method with Sn, Sb₂O₃ and Y₂O₃ as the raw materials. The crystal phase and structure of the prepared conductive particles are characterized by FTIR and XRD techniques respectively. The resistivity of the prepared conductive powders are measured with four-point measurement method. The resistivity of Y and Sb doped SnO₂ conductive particles is 0.22 Ωcm. FTIR spectrum of Y and Sb doped SnO₂ conductive particles shows that the vibration peak are wide peak in 570 cm^-1 ~ 400 cm^-1, and have intense absorption in 4000 cm^-1 ~ 2500 cm^-1, respectively.Y and Sb doped SnO₂ conductive powders have a structure of tetragonal rutile. The complex doping is achieved well by complexation-coprecipitation method and is recognized as replacement doping or caulking doping.

Abstract: Eu, Sb doped SnO₂ and quartz compound conductive powders are prepared by the coprecipitation method with SnCl₄·5H₂O, SbCl_3, Eu₂O₃ and quartz powders as the raw materials. The crystal phase and structure of the prepared conductive particles are characterized by FTIR and XRD techniques respectively. The resistivity of the prepared conductive powders are measured with four-point measurement method. The resistivity of Eu, Sb doped SnO₂ and quartz compound condu-ctive powders is 0.37 Ωcm. FTIR spectrum of Eu, Sb doped SnO₂ and quartz compound conductive powders shows that there are the vibration peaks in 546.14 cm^-1, 489.95 cm^-1, 466.71 cm^-1, 430.34 cm^-1 and 418.92 cm^-1 respectively, and have intense absorption in 4000 cm^-1 ~ 1100 cm^-1. Eu, Sb doped SnO₂ conductive powders have a structure of tetragonal rutile. The complex doping is achieved well by coprecipitation method and is recognized as replacement doping or caulking doping. The composition of compound conductive powders are Eu, Sb doped SnO₂ conductive powders and quartz powders.

Abstract: A theoretical study on the electrostatic interaction between the dissimilarly charged membranes in a salt-free solution has been presented in this paper. The results show that the electric double-layer force is always repulsive for positively charged planar surfaces regardless of surface charge density (or potential) and separation; however, a long-range attraction is observed between surfaces with unequally opposite charge densities. Such attractive force also exists and is independent of the separation when both surfaces carry unequally opposite potential.

Abstract: We fabricated and studied the electrical characteristics of thin-film transistors with an amorphous zinc-tin–oxide (a-ZTO) channel, which was deposited by radio frequency magnetron co-sputtering under different oxygen partial pressures. The effect of varying the oxygen concentration on the electrical properties and device performance of the a-ZTO TFTs was investigated. A positive shift observed in the threshold voltage with increasing oxygen suggests that the number of oxygen vacancies in the a-ZTO film decreased. With an oxygen flow rate of 4 %, a threshold voltage of 2.25 V, an on-off current ratio of 2.1 × 10³, and a subthreshold slope of 0.8 V·dec⁻¹ were obtained.

Abstract: Since their first introduction to the world, both heat pipe and nanofluid have caught the interest of many researchers. Heat pipe with its unique and exceptional capability in transferring heat passively and effectively, was studied intensively and developed extensively for many applications. While nanofluid with its higher thermal conductivity and some other upgraded properties compared to conventional fluid rose as appealing research subject especially on fluid and thermal research area. This study analyzes the utilization of CuO-water nanofluid on biomaterial wick heat pipe. Laboratory-developed CuO-water nanofluid was used as working fluid for vertically straight-shaped biomaterial wick heat pipe. From the experiment, it was shown that the application of CuO-water nanofluid reduced the heat pipe thermal resistance up to 83%. It was figured out that this enhancement is due to the combination of higher thermal conductivity and better wettability of the fluid. It was also found that the heat pipe with nanofluid did not show significant degradation though being inactivated for several weeks. However, it was figured out that unlike the application of low concentration nanofluid, application of high concentration nanofluid was insignificant in improving thermal performance of the heat pipe.

Abstract: This article aims to show the effects of the Micro-EDM process that influences the hole taper by comparing the parameters values during micro-drilling hole on the inconel 718 material. The condition of Micro-EDM drilling spark on the surface workpiece was 300 μm of depth and 200 μm of diameter tungsten carbide electrode. The experiment was carried out under the cover of hydrocarbon, using fluid dielectric cooling. The experiment parameters included on-time duty factor, off-time, voltage, frequency, and current, respectively. The experiment, it was found that the hole taper an immense effect on the machinability of drilling the workpieces, cause melting and recasting in the spark area, making a decrease in the ability of debris removal. Moreover, the experiment result, the tapered workpiece showed a minimized is 16.87 s, when using parameters at current 32 mA, frequency 150 Hz, and voltage 110 v, respectively. The optimal parameters to affected minimum hole taper is 0.195 degree, when using parameters at current 32 mA, frequency 130 Hz, and voltage 110 v, respectively.

Abstract: This research aimed to study the machining efficiency of AISI P20 steel by Electrical Discharge Machining (EDM) using rod copper electrode to machining material by 50 mm depth of machining was mainly assessed from Materials Removal Rate (MRR) and Electrode Wear Ratio (EWR). From the experiment designed to use Taguchi technique of data analysis and suitable parameter prediction, the highest MRR was at on-time of 150 μs, off-time of 2 μs and electric current level was at 15 A or 0.25 A/mm². Predicted value was at 19.2395 mm³/min which was equal to real experiment, showing Materials Removal Rate of 19.647 mm³/min (with error of 2.12 percent) .Moreover, it was found that gap would increase with the size of electrode and depth of machining caused by movement of particles removed from side surface of electrode, which cause micro sparks at the side of the material workpiece.

Abstract: The joint of 2219-T6 aluminum alloy plate was obtained by friction stir welding, and the microstructures and mechanical properties of the joint were investigated. The causes of the weakened joint strength in friction stir welding were analyzed and summarized correspondingly. The tensile properties show that the transverse tensile strength of the joint can reach about 70% of the base metal and the elongation can reach about 7%. The main reason of the weakened strength is due to the plastic damage of metal, followed by the defects generated in the nugget zone and the growth of θ phase in the heat affected zone.

Abstract: This paper introduced the preparation technology and properties of Ag-MoS₂, silver-graphite and AgPd/BZn series silver based brush materials, the existing problems on materials and preparation technology were also analyzed and studied. Materials with the best performance were filtered out through selection of added elements. Influence of added elements and the material properties were analyzed, and the brush material suitable for different application requirements were summarized by analysis the experimental data; so new ideas for the further development of silver matrix brush materials with excellent properties were propounded.

Abstract: In this paper, the fuel-air dispersion and explosion experimental system was designed and experimental simulation on fuel-air mixture spreading and exploding in long-narrow underground fuel depot was carried out. The special phenomena of fuel-air mixture dispersion and explosion process, the characteristic feature of the pressure curve and mechanism were analyzed. The explosion process can be divided into three stages: flame accelerating section, oscillating reaction section and wave dissipating section. And under the same initial conditions, if the ignition time advanced, there is a significant intermittent and large fluctuations phenomenon.