Abstract: A low-voltage TiO2 capacitor-varistor ceramics doped with Ta2O5 and Nd2O3 was systematically researched. The effect of Nd2O3 on the microstructure, nonlinear electrical properties, and dielectric properties of TiO2-based ceramics was investigated. It was found that an optimal doping composition of 99.20 mol% TiO2-0.10 mol%Ta2O5-0.7 mol% Nd2O3 was obtained with low breakdown voltage of 8.5 v/mm, high nonlinear constant of 4.0, ultrahigh electrical permittivity of 1.07× 105 and low tanδ of 0.39. In view of these electrical characteristics, the ceramics of 99.20 mol% TiO2-0.10 mol%Ta2O5-0.7 mol% Nd2O3 is a viable candidate for capacitor-varistor functional devices. The theory of defects in the crystal lattice was introduced to explain the nonlinear electrical behavior of the Nd2O3-doped TiO2-based varistor ceramics.
Abstract: In order to investigate the effects of temperature on the contact strengths of the thick-walled cellular solids, materials of H59 brass was chosen for the preparation of cylindrical specimens which contain single pore, double pores, three pores and four pores respectively. The contact strengths of these specimens were determined in a YE-600 hydraulic testing machine at 20°C (room temperature) and 300°C respectively. The experimental results show that: the temperature had great effect on contact strength of the thick-walled cellular solids, mainly reflected in loading capacity and deformation, when the temperature increased from 20°C to 300°C, the loading capacity of the solids were reduced by 10.94 to 14.85% and the corresponding deformations were increased by 97.50 to 108.33%, which depended on the micro-pores structures. Furthermore, the effects of temperature on cracks out-look mainly reflected in cracks deepening with temperature. When the temperature increased from 20°C to 300°C, the depth of the cracks increased about 78 to 110%, which also depended on the micro-pores structures. However, temperature had little effect on the initiating position of the cracks for all micro-pores structures discussed from 20°C to 300°C.
Abstract: The PMN/EP composites were prepared by resin casting method from PMN powder pretreated with silane coupling agent KH-550. The microstructure of the PMN/EP composite was observed by SEM, the damping property and dielectric property of the composite were investigated by dynamic mechanical analyzer and impedance analyzer respectively. In the composite prepared with PMN powder pretreated by 1.5% silane coupling agent, much epoxy resin fragment is attached in the surface of PMN particles. When the silane coupling agent concentration is 1.5%, the composite shows the best damping property. Dielectric analyses suggest that the dielectric constant of the PMN/EP composite decreases with the increase of silane coupling agent content, however the dielectric loss increases with the increase of silane coupling agent content.
Abstract: Aluminum coatings were prepared by cold spray on mild carbon steel Q235. Scanning electron microscopy shows that the bond zone has good bonding between the substrate and the coating and the coatings consist of interlocked particles. The corrosion behaviors of the coatings in marine environment were studied by electrochemical methods. Free corrosion potentials of aluminum coatings are much lower than that of Q235. Potentiodynamic polarization measurements show that the curves of aluminum coatings have activity anodic dissolution zone, passivation zone and super-passivation zone. Corrosion morphology and energy dispersive spectrometers show that Cl- can penetrate into the coating and some of the substrate has been corroded. Corrosion only can happen on the coating surface and specific deeper sites, where Cl- can penetrate through pores. Cold spray aluminum coatings can protect the substrate from corrosion in marine environment.
Abstract: A new kind of die steel, WD1 used for warm work dies, was developed. The secondary hardening behavior and its affecting factors were studied. The results show that the secondary hardness increases with the content of C, Mo and V elements and Si element can significantly improve the secondary hardening effect though it’s not one of secondary hardening elements. The hardness of WD1 steel tempered at 520°C is more than HRC60, which can meet the requirements of warm work dies.
Abstract: A life cycle assessment was carried out to estimate the environmental impact of industry waste as aggregate in cement production. To confirm and add credibility to the study, an uncertainty analysis was also carried out. Results showed the impact seen from climate change, human toxicity, marine eutrophication, marine ecotoxicity, and freshwater eutrophication categories had an important contribution to overall environmental impact, due to energy use and direct emissions from clinker and limestone production stages. The most significant substances contribute to the climate change is CO2 to air; for the human toxicity, it is Hg to air and Mn to water; for the marine eutrophication and marine ecotoxicity, it is nitrate and Ni to water, respectively; for the freshwater eutrophication, it is phosphorus to water. Increasing electricity recovery rate, optimizing the raw material consumption for clinker production are highly recommended to reduce the adverse impact on the environment, and therefore reduce the pressure on the environment from dramatically increased hazardous industry waste disposal.
Abstract: In order to improve the corrosion resistance property of the aluminum alloy surface, a simple chemical immersion method was developed for fabricating the super-hydrophobic surface on aluminum alloy. After treating the chemical etched surface using low surface energy material stearic-acid, the aluminum alloy surface exhibits a super-hydrophobic property with water contact angle of 154° and contact angle hysteresis of 7°. The surface morphology was inspected with scanning electron microscope, and it was found that the surface was configured in a labyrinth structure with convexity and caves of micro-nanostructure; this hierarchical micro-nanostructure plays an important role in the formation of the super-hydrophobic surface. The effects of the etching time and the etchant (potassium permanganate solution) concentration on the super-hydrophobic surface were investigated, and the optimum technical conditions are that etching the aluminum alloy in 0.1mol/L potassium permanganate solution concentration for 3 h. At the same time, we also studied the wettability of the aluminum alloy super-hydrophobic surface. The results showed that the super-hydrophobic aluminum alloy has good stability, corrosion resistance property and self-cleaning.
Abstract: The dynamic modulus of elasticity (MOE) of forty one small Acer mono clear wood specimens was tested via stress wave, ultrasonic wave, edgewise vibration and flatwise vibration method respectively in laboratory. Then the static MOE of these specimens was measured with static bending test. The correlations between dynamic and static MOE were analyzed using linear regression method, and the difference of various methods was discussed using paired t test. The results show that the dynamic MOE of wood measured by four methods described above are higher than the static MOE, but their linear correlation is significantly strong. Thus, it is feasible to estimate static MOE using these four methods. Additionally, the mean of paired difference between static MOE and dynamic MOE tested by flatwise vibration method is least, and the correlation highest. Therefore, it is better to use flatwise vibration method to estimate static MOE of wood.
Abstract: We analyzed static finite element of the container flooring and chassis combination structure rolling by a car; then, we analyzed the maximum deformation and corresponding maximum stress of the flooring and chassis combination when chassis crossbeam cross-sectional shape from the U-shaped to the I-shaped and compared with the original structure with the same force, as well as the space between the central crossbeam decreased, we can see that, the appropriate crossbeam space can obviously increase the stiffness of the container and reduce the stress of the structure; at the same time, we analyzed the combinations which with different flooring structures, we can see that the difference deformation between the new combination and the original was small, so we know that the mechanical properties of flooring had little effect to the mechanical properties of the entire combination.