Materials Science Forum Vols. 663-665

Abstract: In this work, the pits were successfully etched on the (001) sapphire single crystal surface. The experiments were processed by using fused KOH etchant at different temperature about 15 minutes. The difference in the morphology of etching pits on c plane sapphire was observed by metallurgical microscope and atomic force microscopy. It was found that the size of etch pits would be increasing if the temperature high enough. And the density of etch pits had a maximum at about 320°C.Finally, it was put forward and discussed that three kinds of mechanisms about the etching pits based on the experimental fact: annexed, merger, expansion.

Abstract: With properly chosen structural parameters, the transmission spectra of the mirror symmetrical model of photonic crystal (AB)m (CD)n (BA)m is calculated by means of transfer matrix method. When the transmission band of photonic crystal (CD) is inside the band gap of photonic crystal (AB)m (BA)m, both sharing the same central frequency as their symmetry centers, mirror symmetrical photonic quantum well is formed. At both sides of the central frequencies in the reduced units in the transmission spectra of the well, there are odd resonance-peaks, which symmetrically distributed and orderly localized, and show an obvious quantization effect for transmission-peaks. The number and location of the transmission peaks can be modulated by changing the number of period n of photonic crystal (CD). This can be used for designing the adjustably odd-passaged optical filters.

Abstract: The superparamagnetic NiFe2O4 nanoparticles were synthesized using a hydrothermal technology through P123 sphere micelles as ‘nanoreactor’ in this work. Their morphologies, structures, surface properties and magnetism were characterized by FE-SEM, XRD, FTIR, and VSM, respectively. The nickel ferrite samples are nearly spherical and homogeneous nanoparticles with average size range of about 50-120 nm. They possess superparamagnetism at room temperature and higher saturation magnetization. X-ray diffraction (XRD) pattern confirms that the samples belong to the cubic crystal system with an inverse-spinel structure. Fourier transform infrared (FTIR) absorption spectrum indicates that the NiFe2O4 nanoparticles are stabilized by the P123 adsorbed on the surface of nanoparticles.

Abstract: A complicated 3D model was established to solve the problem of the lifetime of an engine support. With the finite element analysis software ANSYS, we analyzed the fatigue problem for an engine support and derived the numerical values of the lifetime of a typical engine support. Our work provides the fundamental guidance to optimize the structure of the engine support.

Abstract: Microscale flyash/SBS composite modified asphalts (CMA) were prepared by melt blending. Rolling thin film oven test (RTFOT) was employed to study the anti-aging property. Both flyash and SBS disperse homogeneously in the base asphalt, which lead to an improvement in terms of toughness, strength, and thermal stability. Moreover, microscale flyash plays a significant role in the CMA. The effect of flyash on the properties of SBS modified asphalt appears as a decreasing penetration, an increasing softening point, and a decreasing ductility. The anti-deformation ability under high temperature of the CMA improved significantly. In comparison with that of the base asphalt, the softening point of the CMA decreases after aging, which maybe attribute to the different rheological properties between the CMA and the base asphalt. Compared to that of SBS modified asphalt, the anti-aging property of CMA improved significantly. This demonstrates that the microstructure of flyash can prevent oxygen from diffusing and permeating.

Abstract: The evolution operator approach is applied to studying photon-electron pumping effects on a quantum dot connected to two magnetic leads in the presence of both via-dot and over-dot tunneling channels. It is found that a microwave field applied to the quantum dot may give rise to charge and spin pumping at zero bias voltage for asymmetric magnetic junctions.