Abstract: This study experimentally analyzed the hygrothermal effect on the static and fatigue strengths of acid-treated multi-walled carbon nanotubes (CNTs)/epoxy composites. The nanocomposite specimens with various CNT contents (0., 0.5, and 1.0 wt.%) were statically and fatigue-tested under three different hygrothermal conditions (25 °C/60% RH, 25° C/85% RH, and 40 °C/85% RH) to investigate the influences of hygrothermal conditions and CNT contents on the tensile static and fatigue strengths of the studied nanocomposites. The results show that the static and fatigue strengths decreased slightly at 25 °C/85% RH environments compared with those tested under the 25 °C/60% RH condition. However, the static and fatigue strengths of the studied nanocomposites decreased substantially under the 40 °C/85% RH condition. The combined temperature and humidity environments weaken the interfacial adhesion between the CNT surfaces and the epoxy matrix. Moreover, the experimental results show that the addition of 0.5 wt.% of carbon nanotubes improved the static and fatigue strengths considerably under the same hygrothermal environments. However, when an excessive amount of CNTs was used (1.0 wt.%), the nanocomposite exhibited the lowest strengths compared with the specimens with 0 and 0.5 wt.% CNTs. The stress concentration effect caused by the CNT aggregates was detrimental to the static and fatigue strengths of the studied nanocomposites.
Abstract: Stainless automotive battery fastener requires high dimension precision and narrow tolerance. In order to save the developing cost and accumulate more production design experiences, CAD/CAE technology has been used in multi-stage cold forging with five stages to shorten our developing cycle time. In this paper, the CAD drawing is made by Inventor 3D software, then import the STL file to DEFORM-3D software to do the settings of pre-process and simulation analysis. Effective stress, effective strain, velocity field, and forging force have been shown in this study. Finally, the actual manufacture measurement results compares with simulation datum to verify the analysis acceptance. After comparing the FEM simulation results with actual forming measurements, the error rate of washer diameter is increased in fourth stage. Although the measurement results are still in tolerance, the future work is to decrease the error rate through optimizing the mold design of fourth stage. The verification is performed to reduce the error rate according to the research method proposed in the study. On the other hand, the mold life in the actual forming is found to be easily damaged in the fifth stage. In the future, production improvement should be done through modifying the design of mold and die for the third and the fourth stages, the life of mold and die is explored to reduce the forging force in the fifth stage.
Abstract: Biodegradable metals have been proposed for temporary implants such as coronary artery stent and internal bone fixators. During implantation, a stent is inserted and expanded by using a catheter into a narrowed coronary artery and is subjected to mechanical stress in a corrosive body fluid environment, a condition where stress corrosion cracking may occur. This letter reports an experimental work to verify the susceptibility of Fe-35Mn alloy, a proposed alloy for biodegradable coronary stent, to stress corrosion cracking under a pseudo-physiological condition.
Abstract: Recent years due to the rise of awareness of environmental protection and energy conservation are attention. Which is the most representative of the bike. Many processing factors must be controlled in the bicycle chain wheel. This study employed the rigid-plastic finite element (FE) DEFORMTM 3D software to investigate the plastic deformation behavior of an aluminum alloy workpiece as it is forged for bicycle chain wheels. Factors include the temperature of the forging billet, shear friction factor, temperature of die and punch speed control all parameters. Moreover, this study used the Taguchi method and Genetic algorithm neural networks to determine the most favorable optimization parameters. Finally, our results confirmed the suitability of the proposed design, which enabled a bicycle chain wheel die to achieve perfect forging during finite element testing.
Abstract: Silicon nitride (SiNx), an important material used as a dielectric layer and passivation layer in thin film transistor liquid crystal display (TFT LCD) was patterned by a non-lithographic process. SiNx was deposited by plasma enhanced chemical vapor deposition (PECVD) on glass substrate. Laser photoablation can effectively pattern 5 µm diameter with 200 nm depth hole in SiNx thin films with laser photoablation. The threshold remove fluence is 1350 mJ/cm2 with 1 laser irradiation shot. The contact-hole taper angle as a function of the laser irradiation shot number. The taper angle increased with increasing the laser irradiation shot number. The contact-hole taper angle etched profile was successfully controlled by vary the laser irradiation shot number.
Abstract: Recent years mesoporous bioactive glasses (MBGs) have become important biomaterials because of their high surface area and the superior bioactivity. Various studies have reported that when MBGs implanted in a human body, hydroxyl apatite layers, constituting the main inorganic components of human bones, will form on the MBG surfaces to increase the bioactivity. Therefore, MBGs have been widely applied in the fields of tissue regeneration and drug delivery. The sol-gel process has replaced the conventional glasses process for MBG synthesis because of the advantages of low contamination, chemical flexibility and lower calcination temperature. In the sol-gel process, several types of surfactants were mixed with MBG precursor solutions to generate micelle structures. Afterwards, these micelles decompose to form porous structures after calcination. Although calcination is significant for contamination, crystalline and surface area in MBG, to the best of the authors’ knowledge, only few systematic studies related to calcination were reported. This study correlated the calcination parameters and the microstructure of MBGs. Microstructure evaluation was characterized by transmission electron microscopy and nitrogen adsorption/desorption. The experimental results show that the surface area and the pore size of MBGs decreased with the increasing of the calcination temperature, and decreased dramatically at 800°C due to the formation of crystalline phases.
Abstract: The effect of titanium and aluminum contents, strain, strain rate and tested temperatures on the mechanical properties and microstructural properties will be investigated in this study. These cobalt base super alloys are to be tested using material testing system (MTS) at strain rates of 10-3, 10-2 and 10-1s-1 and at temperatures of 700°C, 500°C and 25°C respectively. It is found that the flow stress increases with increasing strain rate and Ti and Al contents, but decreases with increasing temperature. Furthermore, the strain rate sensitivity increases with increasing strain rate, but decreases with increasing temperature. The microstructural observations confirm that the mechanical response of the cobalt superalloy specimens is directly related to the effects of the titanium and aluminum contents, strain rate and temperature on the evolution of the microstructure. It can be observed that the strengthening effect in cobalt suprealloy is a result primarily of dislocation multiplication. The dislocation density increases with increasing strain rate, but decreases with increasing temperature.
Abstract: Abstract. The effects of thermal annealing on the electrical and interfacial structure properties of Ni/Au on n-type GaN Schottky contacts were investigated by current-voltage (I-V) . Based on the I-V measurement study, it was found that the Schottky barrier height increased when the contact was annealed in the 300 °C – 400 °C temperature range. A drastic improvement of the Schottky barrier height was attained by thermal annealing at 400 °C for 10 minutes. However, it degraded when the annealing temperature exceeded 500 °C. The contact annealed at 550 °C showed nonrectifying behavior. For this paper, the GaN metal-semiconductor-metal (MSM) ultraviolet photodetectors were fabricated using Ni/Au Schottky contacts. As expected, compared with the MSM detector without the thermal annealing process, the dark current of the MSM device with the 400 °C thermal annealing process drastically decreased as much as three orders of magnitude, due to the enhancement of the Schottky barrier height
Abstract: To study the relationship between the molecular main chain structure and the properties of amine based tetra-functional epoxy resins, especially for the thermal stabilities and the mechanical properties, N,N,N',N'-Tetraglycidyl-2,2-Bis[4-(4-aminophenoxy)phenyl]propane (TGBAPP) and N,N,N',N'-Tetraglycidyl-4,4'-diamino diphenyl ether (TGDDE) were cured with Methyl nadic anhydride (MNA). The thermal behavior of the cured epoxy resins were studied with the thermo-gravimetric analysis (TGA), and the glass transition temperature (Tg) were determined with the Dynamic Mechanical Analysis (DMA). Additionally, the mechanical properties of them were tested. The results indicated that the cured epoxy resin based on TGBAPP had better thermal stabilities and toughness.
Abstract: In this work, titanium-doped indium-tin-oxide (ITIO) films were deposited onto the glass substrates at room temperature by in-line RF magnetron sputtering. The deposition rate of the ITIO film increases with the RF power. The average transmittance of the deposited ITIO film is higher than 85% in the wavelength range of 350 - 950 nm. The resistivity of the sputtered ITIO has been reduced down to 7.03 × 10-4 Ω-cm. The poly-Si solar cell with ITIO film as the anti-reflection coating shows an efficiency improvement of 36.5% over that with AZO anti-reflection coating.