Applied Mechanics and Materials Vols. 479-480

Abstract: In this study, nano-titanium films of different thickness were deposited. By adjusting it is found that when the thickness of the titanium films was in the nano-scale, the electric resistivity of the titanium films decreased. Furthermore, the deposited titanium was transformed into titanium oxide by maintain an oxygen atmosphere and using a rapid annealing furnace during sputtering. When oxidized nano titanium film is sputtered on a low-electric-resistive metal thin film, the photo-electronic properties of Nano-thin film will be enhanced.

Abstract: As an important performance parameter of nitrile-butadiene rubber（NBR）sealing ring, the compression set is a main factor influencing rubber's life. Using the compression set amount as its degradation measurement and the temperature as accelerating stress, we perform the design and actual implementation of a set of accelerated degradation test of NBR considering step-stress. Then we evaluate the results using accelerated degradation model based on the drift theory of Brownian motion. Finally we get the estimation of reliable life of sealing ring under normal temperature. The research in this paper can also offer a new method for the application reliability and life evaluation of rubber products.

Abstract: The development of composite thin film materials bloomed with increasing demand and technical improvements. They have been used in various engineering areas, such as micro-conductor, sensors, and micro-electro-mechanical-system (MEMS) [1-. Nowadays, scientists were able to electroplate silicon carbide thin films directly on metal materials. Silicon carbide has many excellent mechanical properties, such as high Youngs modulus, high melting point, high hardness, and chemical inertness with resistance to high temperature oxidation and creep [4-7]. It is widely utilized in automotive and aerospace industry. Hence, it is very important to improve the durability and reliability of electroplated silicon carbide thin films.

Abstract: The cubic and rod-shaped powders of indium tin oxide were synthesized at a stable temperature reaction for 18h using the surfactant aid hydrothermal method under various conditions. The cubic and rod-shaped powder size changes with the concentration of the precursor. The finished products of indium tin oxide can be obtained by calcination at 500°C for 2h in air. Characterization was conducted using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffractometry (XRD), thermogravimetric analyzer/differential thermal analysis (TG/DTA) and the Brunauer-Emmett-Teller (BET). XRD analysis shows that the conditions of this experiment can produce pure ITO powders. The characterization of cubic and rod-shaped ITO powders is also discussed.

Abstract: A chemical bath deposition (CBD) method was applied to grow zinc oxide nanorod arrays on transparent conductive oxides acting as templates for the synthesis of TiO₂/ZnO nanostructures (TiO₂/ZNR) followed by HCl etching, and then these nanostructures were assembled as anodes in dye-sensitized solar cells. The ZnO nanorods, predominantly grew with good crystallinity along c-axis, exhibit wurtzite structure with smooth surface. Etching of the TiO₂/ZNR by HCl changes the most preferential crystal plane of ZnO from (002) to (100) and significantly increases the atomic ratio of Ti/Zn. Optical absorption measurements indicate a band gap energy of 3.1 eV for ZNR and TiO₂/ZNR. Increasing the spin coating time (SCT) of TiO₂ on ZNR increases the PL intensity. The seed layer number (SLN) of ZnO exerts moderate influence on the photo-to-electricity conversion and an optimum SLN was observed for this study.

Abstract: Carbon nanotubes (CNTs) have been proposed as one of the most promising materials for nanoelectro-mechanical system due to high elastic modulus, high failure strength and excellent resilience [1,. Recent development of many-body interaction [3, made possible realistic molecular dynamics (MD) simulations of carbon-made systems. We carried out such studies for carbon nanotubes under generic modes of mechanical load: axial compression, bending, and torsion. A singular behavior of the nanotube energy at certain levels of strain corresponds to abrupt change in morphology. In this letter, we report the torsional instability analysis of single wall carbon nanotube filled with hydrogen via molecular dynamics simulations. The simulations are carried out at a temperature 77K which previous study obtained the hydrogen storage inside CNT at this condition [A. C. Dillo. Here we use atomistic simulations to study a flexible surface narrow carbon nanotube with tube diameters 10.8 Å. According to conventional physisorption principles, the gas-adsorption performance of a porous solid is maximized when the pores are no larger than a few molecular diameters [8]. Under these conditions, the potential fields produced at the wall overlap to produce a stronger interaction force than that observed in adsorption on a simple plane. However, the mechanisms responsible for the adsorption and transportation of hydrogen in nanoporous solids or nanopores are not easily observed using experimental methods. As a result, the use of computational methods such as molecular dynamics (MD) or Monte Carlo (MC) simulations have emerged as the method of choice for examining the nanofluidic properties of liquids and gases within nanoporous materials [9,1. Several groups have performed numerical simulations to study the adsorption of water in CNTs [11-1, while others have investigated the diffusion of pure hydrocarbon gases and their mixtures through various SWNTs with diameters ranging from 2 ~ 8 nm [17-19] or the self-and transport diffusion coefficients of inert gases, hydrogen, and methane in infinitely-long SWNTs [20-21]. In general, the results showed that the transport rates in nanotubes are orders of magnitude higher than those measured experimentally in zeolites or other microporous crystalline solids. In addition, it has been shown that the dynamic flow of helium and argon atoms through SWNTs is highly dependent on the temperature of the nanotube wall surface [22]. Specifically, it was shown that the flow rate of the helium and argon atoms, as quantified in terms of their self-diffusion coefficients, increased with an increasing temperature due to the greater thermal activation effect. Previous MD simulations of the nanofluidic properties of liquids and gases generally assumed the nanoporous material to have a rigid structure. However, if the nanoporous material is not in fact rigid, the simulation results may deviate from the true values by several orders of magnitude. Several researchers have investigated the conditions under which the assumption of a rigid lattice is, or is not, reasonable [23, 24]. In general, the results showed that while the use of a rigid lattice was permissible in modeling the nanofluidic properties of a gas or liquid in an unconfined condition, a flexible lattice assumption was required when simulating the properties of a fluid within a constrained channel. Moreover, in real-world conditions, the thermal fluctuations of the CNT wall atoms impact the diffusive behavior of the adsorbed molecules, and must therefore be taken into account. This study performs a series of MD simulations to investigate the transport properties of hydrogen molecules confined within a narrow CNT with a diameter of 10.8 Å (~ 1 nm) at temperatures ranging from 100 ~ 800 K and particle loadings of 0.01~1 No/Å. To ensure the validity of the simulation results, the MD model assumes the tube to have a flexible wall. Hydrogen molecules are treated as spherical particles. In performing the simulations, the hydrogen molecules are assumed to have a perfectly spherical shape. In addition, the interactions between the molecule and the CNT wall atoms and the interactions between the carbon atoms within the CNT wall are modeled using the Lennard-Jones potential [25,2. The simulations focus on the hydrogen adsorption within the SWNT not adsorption in the interstices or the external surface of nanotube bundles.

Abstract: Atomic layer deposition (ALD) is utilized to grow high performance aluminum oxide (Al₂O₃) barrier films on flexible PET substrates, where the effects of precursor pulse time and deposition temperature on the film properties are also studied in this work. Significant differences are observed that the water vapor transmission rate of the PET substrate is largely improved by coating the Al₂O₃ barrier films. Further observations on the surface roughness, optical transmittance, adhesion, mechanical properties of the deposited films are also conducted. The results show that the Al₂O₃ film deposited with 10 msec precursor pulse time and 60°C deposition temperature behaves the best performance.

Abstract: Magnetic finishing with gel abrasive (MFGA) performs better than magnetic abrasive finishing (MAF) in terms of polishing efficiency. However, silicone gels are semi-solid polymer gels with deforming properties that are temperature dependent materials, ultimately degrading the polishing efficiency in MFGA significantly. Therefore, this study evaluated the MFGA mechanism to elucidate the properties of silicone gels in order to attain both the finished effect in MFGA and effective gel abrasives to produce a highly efficient polished surface. Cylindrical rods were polished using silicone gels with different plasticity to determine the temperature of abrasive media in the working area. Next, circulating effects of abrasive media were identified to ensure the efficiency in MFGA. Additionally, finding the relation between the concentrations of abrasive media and circulating effect in the working area. Experimental results showed that silicone gels with low plasticity produced high temperature of abrasive media in MFGA, and high temperature of abrasive medium made excellent circulating effect in the working area, inducing high material removal and fine surface roughness.

Abstract: In this paper, intermittent gas jet assisted laser drilling on stainless steel (SUS304) with a fiber laser of wavelength 1090 nm is studied. Compared with the conventionally used continuous gas jets in assisting laser drilling, the intermittent gas jet assisting can effectively increase the material removal rate. The intermittent gas jet can be modulated with the frequency to effectively reduce the over-cooling effect by the assist gas. Experimental result shows that the drilling depth and machining time can be improved. The effects of the intermittent gas jet pressures and the synchronicity of gas and laser pulses on the laser drilling are investigated and discussed. It is observed that the intermittent gas jet method obviously reduces heat loss and increases the machining efficiency during the laser drilling. Compared with result of using the continuous gas jet, laser drilling with the intermittent gas jet at 40 Hz increases the drilling depth with an improvement of 10%. It is worth noting that the intermittent gas jet method can also reduce the quantity and cost of gas while the gases such as helium and argon gases are applied.

Abstract: Aluminum films were prepared on the glass substrate by electron-beam vapor deposition. Nanoindentation tests were employed to determine the hardness and Youngs modulus of the Al film. The effect of substrate temperature on the mechanical properties of the Al film was investigated. Experimental results show that the hardness of Al film is increasing with the increase of the substrate temperature. It can also be observed that the Youngs modulus of Al film doesnt significantly depend on the substrate temperature.