One of the main factors of laser induced damage is the modulation to incident laser which is caused by the defect in the subsurface of the fused silica. In this work, the repaired damage site irradiated by CO2 laser is simplified to a Gaussian rotation according to the corresponding experimental results. Then, the three-dimensional finite-difference time-domain method is employed to simulate the electric field intensity distribution in the vicinity of this kind of defect in fused silica front subsurface. The simulated results show that the modulation is notable, the Emax is about 2.6 times the irradiated electric field intensity in the fused silica with the damage site (the width is 1.5 μm and depth is 2.3 μm) though the damage site is repaired by CO2 laser. The phenomenon and the theoretical result of the annular laser enhancement existed on the rear surface are first verified effectively, which agrees well with the corresponding experimental results. The relations between the maximal electric field intensity in fused silica with defect depth and width are given respectively. Meanwhile, the corresponding physical mechanism is analysed theoretically in detail.
A honeycomb-like metallic catalyst (Pt-Ni-P/Ti) supported on a Ti sheet was prepared by electrodeposition-displacement method. The Ni-P amorphous alloy was first electrodeposited on the Ti substrate, and then replaced by displacement of Ni in amorphous Ni-P with H 2 PtCl 6 . The morphology and methanol oxidation performance of the prepared catalyst were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), anodic linear sweep voltammetry (LSV), cyclic voltammetry (CV), and the anodic stripping of a pre-adsorbed CO monolayer. The SEM results show that the Pt-Ni-P nanoparticles obtained by displacement of Ni in amorphous Ni-P with H 2 PtCl 6 had a honeycomb-like porous structure, while the Pt-Ni nanoparticles had a wheat-like structure. The formation of the honeycomb-like porous structure can be explained by the so-called "out-situ dissolution-deposition mechanism", in which the metallic Ni in Ni-P/Ti electrode preferentially dissolve to form pore structure and release electron. The released electrons can be captured by the 2 6
By molecular dynamics simulations employing an embedded atom method potential, we have investigated structural transformations in single crystal Al caused by uniaxial strain loading along the [001], [011] and [111] directions. We find that the structural transition is strongly dependent on the crystal orientations. The entire structure phase transition only occurs when loading along the [001] direction, and the increased amplitude of temperature for [001] loading is evidently lower than that for other orientations. The morphology evolutions of the structural transition for [011] and [111] loadings are analysed in detail. The results indicate that only 20% of atoms transit to the hcp phase for [011] and [111] loadings, and the appearance of the hcp phase is due to the partial dislocation moving forward on {111} fcc family. For [011] loading, the hcp phase grows to form laminar morphology in four planes, which belong to the {111} fcc family; while for [111] loading, the hcp phase grows into a laminar structure in three planes, which belong to the {111} fcc family except for the (111) plane. In addition, the phase transition is evaluated by using the radial distribution functions.
By performing density functional theory plus U calculations, we systematically study the structural, electronic, and magnetic properties of UO2 under uniaxial tensile strain. The results show that the ideal tensile strengths along the [100], [110], and [111] directions are 93.6, 27.7, and 16.4 GPa at strains of 0.44, 0.24, and 0.16, respectively. After electronic-structure investigation for tensile stain along the [001] direction, we find that the strong mixed ionic/covalent character of U-O bond is weakened by the tensile strain and there will occur an insulator to metal transition at strain over 0.30.
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