Abstract: The structure, elastic and electronic properties of 2H-CuGaO2 are calculated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density functional theory. The calculated equilibrium lattice parameters is in good agreement with experimental and reported values. The elastic coefficients, bulk, shear and Youngs modulus, Poissons ratio and elastic anisotropy ratio of 2H-CuGaO2 were calculated. The electronic properties of 2H-CuGaO2 have been calculated and the results show that 2H-CuGaO2 has an indirect band gap.
Abstract: An Ni-4.8at%Ti alloy was prepared and the electron energy loss spectroscopy (EELS) of nickel was collected. The d-electron occupancy of Ni is measured from the white-line intensity of EELS. It was found that relative to pure Ni the d-electron occupancy of Ni in Ni-4.8at%Ti alloy did not change significantly.
Abstract: Molecular dynamics simulation method was used to study the rarefied gaseous flows in nanochannels. A pressure-driven force was introduced to drive the gas to flow between two parallel walls. The effects of driven force magnitude and channel height were investigated. The results show that a single layer of gaseous molecules is adsorbed on the wall surface. The density of adsorption layer decreases with the increase of channel height, but doesnt vary with driven force. The velocity profile across the channel has the traditional parabolic shape. The average velocity and gas slip velocity on the wall increase linearly with the increase of pressure-driven force. The gas slip velocity decreases linearly with the increase of channel height. The ratio of slip to average velocity decreases linearly with the increase of channel height.
Abstract: The surface of aramid fiber is very smooth and chemical inert.The adhesiveness of aramid fiber with EPDM rubber materials is not good.So the tensile strength of EPDM rubber composite materials is influenced seriously.This paper modified the surface of aramid fiber with silicon coupling agentKH-550. We test the chang of fibers in surface with the ESCA,and the result is that content of carbon decreased ,while content of nitrogen and oxygen element increased.The activity of surface of fiber has been increased. Strength of composite materials increased from 2.58MPa to 3.22 MPa . The SEM photos of samples indicate that the weight of EPDM rubber on surface of EPDM rubber is more than untreated fiber composite materials .The treating effect on aramid fiber is best when the concentration of KH-550 is 5%,5hours.
Abstract: Subject to a compressive membrane force, a film bonded to a compliant substrate often forms wrinkles. In the past, the studies of such wrinkles are mostly based on the assumption of semi-infinite substrate. However, such an assumption cannot be satisfied in real applications. This paper focuses on wrinkling of a rigid film on a compliant thin-substrate. The finite element method used to analyze wrinkling and investigate the relationship between the critical wavelength, material parameters (such as film Youngs modulus, substrate Poisson's ratio) and geometric parameters (such as substrate thickness). Meanwhile, the finite element results are compared with analytical results.
Abstract: Nanocomposites have been utilized increasingly because of their high strength, stiffness, toughness, and through-thickness properties. The incorporation of carbon nanofibers with a high aspect ratio and extremely large surface area into glass/epoxy polymer composites improve their tensile and compression properties significantly. Although a number of efforts have been made to improve various properties by mixing nanoparticles directly into resin, however, it could lead to high viscosities which create problems during processing. In this particular study, an attempt has been made to investigate tensile and compression behavior of nanocomposites by using, state of the art, a different technique i.e spraying the Carbon nanoFibers (CNF) on dry woven glass pre-form before infusion. The nanocomposite samples were prepared using a spraying methodology i.e dispersing the 2.0 weight percent CNF solution on glass fabric, and evaporating the solvent such that only nanofibers remain on perform, followed by Vacuum Assisted Resin Transfer Molding (VARTM). Tensile and compression tests were performed to evaluate the effectiveness and behavior of CNF addition on these mechanical properties. Results indicated simultaneous improvement in tensile and compression properties by incorporating a very small amount of carbon nanofibers into the matrix system. 1821 percent improvement in tensile strength and 6-9 percent in compressive strength, with respect to the neat composite. The rise in their modulus has also been discussed in detail and part of this study. For in-depth analysis, microscopic approaches were also carried out to investigate the fracture behavior and mechanism of material. Scanning electron microscopy of fractured surfaces revealed improved primary fibermatrix adhesion and indications of CNF-induced matrix toughening due to the presence of CNFs. SEM evaluation also revealed relatively less damage in the tested fracture surfaces of the nanophased composites in terms of matrix failure, fiber breakage, matrixfiber de-bonding, and de-lamination, compared to the neat system.
Abstract: Fatigue crack growth (FCG) behavior at weld nugget zone (WNZ) and heat affected zone (HAZ) in friction stir welded (FSWed) joints joined by using a bobbin type tool in 5052, 6N01 and 7N01 aluminum alloys were investigated comparing to the base materials (BM). Constant stress amplitude fatigue crack growth tests were conducted with stress ratio of 0.1. Crack closure behavior was investigated simultaneously during fatigue test with unloading elastic compliance method. The results in this study showed that in near threshold region, FCG resistance in WNZ of FSWed 5052 and 6N01 joints was lower than that in the BM and the HAZ. In contrast, FCG resistance in WNZ of FSWed 7N01 joint was higher than that in the BM and the HAZ. At high ΔK region, WNZ of FSWed 5052 joint had the similar FCG resistance with the BM and the HAZ. However, WNZ of FSWed 6N01 joint showed lower FCG resistance compared to the BM and the HAZ. FCG resistance in WNZ of FSWed 7N01 joint was the similar with that in the HAZ but was lower than that in the BM. Crack closure behavior was observed in BM and HAZ for all materials tested. In WNZ, crack closure was found in FSWed 7N01 joint but was not found in FSWed 5052 and 6N01 joints. Difference in FCG behavior at different weld region was mainly due to difference in crack closure behavior in FSWed 5052 and 6N01 joints. However, in case of FSWed 7N01 joint, it is considered that effect of microstructure was significant on FCG behavior even at high ΔK region.
Abstract: This study relates to a micromechanics based finite element model of the effect of oxidation on heat transfer and mechanical behavior of a (Zr,W)B2 ceramic at high temperature. An adaptive remeshing technique is employed in both heat transfer and thermal stress analysis models. A global-local modeling technique is used to combine finite elements with infinite elements for thermal stress analysis. Temperature and thermal stress distributions in the ceramic and the oxides are presented.
Abstract: A new kind of functionalized CdTe/Fe3O4 was synthesized for the quantitative and selective determination of bovine serum albumin (BSA). The effects of pH value, reaction time, temperature and dosage of CdTe/ Fe3O4 on the detection of BSA were investigated. Under optimal conditions, the straight line equation: F/F0=1.40412+0.07216 C (μmol/L) was found between the relative fluorescence intensity and the concentration of BSA in the range of 0.69-5.52 μmol/L, and the limit of detection was 0.18 μmol/L.