Applied Mechanics and Materials Vol. 302

Abstract: A partial substitution of Ni by Mn has been implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous Mg2Ni-type Mg20Ni10-xMnx (x = 0, 1, 2, 3, 4) alloys were synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys were studied by x-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). The hydrogen absorption and desorption kinetics of the alloys were measured by using an automatically controlled Sieverts apparatus. The results show that the as-spun Mn-free alloy holds typical nanocrystalline structure, whereas the as-spun containing Mn alloys display a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass forming of the Mg2Ni-type alloy. The hydrogen absorption capacity of the alloys first increases and then decreases with the rising of Mn content, but the hydrogen desorption capacity of the alloys grows with the increasing of Mn content.

Abstract: Nano-structured and micron Al2O3-13%TiO2 coatings were deposited by air plasma spraying.Wear properties of the coatings under different temperature trough SRV friction and wear testing machine were studied, the results shows that the friction coefficient of nano and micron Al2O3-13%TiO2 coatings both have rising trend.with the temperature increases.The wear volume of micron coating is 1.8-2 times that of the nano coating..The nanometer Al2O3-13%TiO2 coating slide with ZrO2 is still compact and has no large crack after abrasion.

Abstract: A new process for advanced wastewater treatment process has been devised with auxiliary treatment unit employing the ammonia oxidizing photo-catalytic thin film. In winter time, due to low water temperature, conventional nitrogen removal treatment experiences almost no nitrification by nitrifying bacteria. To solve the problem and to meet the governmental effluent guideline the treated water has been recycled through the auxiliary unit in which the auxiliary system was applied with the thin film coating photo-catalyst. This study also identifies the characteristics of the thin film coating-photo-catalyst through XRD, SEM and analyzes the ammonia nitrogen removal efficiency by using the thin film coating photo-catalyst in the reactor which resembles a sewage treatment process. The evaluation of the entire process of biological treatment in accord with the application of thin film coating photo-catalyst was performed through computer simulation. A relevant computer model for mass balance was made and utilized to select proper optimal operating condition such as recycle ratio. Result shows the proposed new process has potential applicability to renovate existing treatment plants.

Abstract: Wood density samples were collected from dahurian larch (Larix gmelinii Rupr.) trees grown in northeastern China. Six discs (about 5 cm thick) were cut from each tree (i.e. from the root stem, at breast height (1.3m), and at 20%, 40%, 60%, and 80% of the total height). For each disc, a thick sliver with parallel sides was cut out along the diameter of the disc. The sliver was about 40-mm thick, with the pith located in the middle. Eight small pieces were cut from the sliver with equal distance from pith to bark. Wood density of small piece was obtained using water displacement method. A second order polynomial equation with linear mixed-effects was used for modeling wood density. The LME procedure in S-Plus is used to fit the mixed-effects models for the wood density data. The results showed that the polynomial model with three random parameters could significantly improve the model performance. The fitted mixed-effects model was also evaluated using a separate dataset. The mixed model was found to predict wood density better than the original model fitted using ordinary least-squares based on absolute and relative errors.

Abstract: La0.8Sr0.2FeO3 electrodes modified with nanoparticles of La0.8Sr0.2MnO3 (LSF/LSM) were prepared by infiltration method. LSM solution had good wettability on LSF surfaces and good electrochemical compatibility with LSF. The impedance of half-cells incorporating the electrodes was also examined. The deconvolution of the impedance spectrum indicated that the peak positions are changed after the LSF infiltration. The LSF/LSM electrode exhibited smaller polarization resistance than pure LSF electrode. Finally, a transform from asymmetry to symmetry appeared in the polarization curves of LSF/LSM electrode with the increase of temperature.

Abstract: In the solid state bonding, joint are made by pressing surfaces together at high temperature so that a bond grows across the interface by atomic diffusion. In order to satisfy both requirements of thermal and mechanical properties of aerospace vehicle, conductive CuCrZr alloy was bonded to duplex steel with high strength. Solid state bonding was performed at 3 different pressure conditions and at temperatures of 850°C and 950°C. Microstructural and mechanical evaluation was performed to obtain the optimum joining condition.

Abstract: The assembly of the limiting dome height tests is developed to evaluate the formability of the magnesium alloy sheet AZ31B. The influence of forming conditions on the formability of AZ31B sheet is investigated by limiting dome height tests. The limiting bulging coefficient is used to represent the formability of AZ31B sheet in the tests. The sheet thickness, forming temperature, punch speed and lubrication are taken as influence factors in the tests. The experimental results show that the sheet of thickness 0.6mm has better formability and the proper forming temperature is about 200~250°C for AZ31B sheet. The low punch speed and good lubrication can also improve the formability of AZ31B sheet.

Abstract: Bi0.9Nd0.1FeO3 (BNFO) films were deposited on Si (100) and (La,Sr)(Al,Ta)O3 (100) (LAST) substrate by radio frequency (RF) magnetron sputtering method respectively. The structure，morphology and magnetic properties were studied. X-ray diffraction (XRD) result indicates that the BNFO films on different substrate adopted different orientation. Cross-section scanning electron microscopy shows that the film thickness is 145 nm．Magnetic properties measurement shows that the film on Si(100) substrate has the larger saturation magnetization (Ms) of 3 686 emu/cm3, while the Ms value of the BNFO films on LSAT(100) substrate is only 1 213 emu/cm3.

Abstract: In this paper, magnesium hydride was used to react with water to produce the hydrogen gas. Magnesium hydride is the chemical compound MgH2, which contains 7.66% by weight of hydrogen. Although the concept of reacting chemical hydride with water to produce hydrogen is not new, there have been a number of recent published papers which might be employed to power fuel cell devices for portable applications. Under the room temperature, the hydrolytic reaction between magnesium hydride and water to form a thin-layer of magnesium hydroxide on the outer surface impedes water from coming into direct contact with the magnesium hydride. The key to continual removal of the coherent magnesium hydroxide layer by adding a citric acid has the following conclusions. First, using this approach can reach the 6.4wt% of hydrogen. Finally, the cost of producing hydrogen from magnesium hydride-water hydrogen generation approach would cost approximately $15 per kg hydrogen.

Abstract: The electrochemical performances of resorcinol–formaldehyde-based carbon aerogels can be significantly enhanced by nitric acid activation.FT-IR spectra and SEM images reveal the constitution and morphology of samples .The electrochemical performances of materials were tested by cyclic voltammetry,galvanostatic charge/discharge test ,electrochemical impedance spectroscopy and cyclic test. The results show that activation does not influence the molecular structure of carbon aerogels,which maintains their nano-porous structure. Activation increases the specific capacitance by 50% and improves the conductivity of carbon aerogels,resulting in fenfect cycling stability. So nitric acid activated carbon aerogels is an ideal electrode material for supercapacitors.