Splitting the Fast and Slow Motions in Molecular Dynamics Simulations Based on the Change of Cold Potential Well Bottom

The atomic motion is coupled by the fast and slow components due to the high frequency vibration of atoms and the low frequency deformation of atomic lattice, respectively. A two-step approximate method was presented to determine the atomic slow motion. The first step is based on the change of the location of the cold potential well bottom and the second step is based on the average of the appropriate slow velocities of the surrounding atoms. The simple tensions of one-dimensional atoms and two-dimensional atoms were performed with the full molecular dynamics simulations. The conjugate gradient method was employed to determine the corresponding location of cold potential well bottom. Results show that our two-step approximate method is appropriate to determine the atomic slow motion under the low strain rate loading. This splitting method may be helpful to develop more efficient molecular modeling methods and simulations pertinent to realistic loading conditions of materials.

Fast plasma sintering deposition of nano-structured silicon carbide coatings

Fast plasma sintering deposition of SiC nano-structured coatings was achieved using a specially designed non-transferred dc plasma torch operated at reduced pressure. Employing the Taguchi method, the deposition parameters were optimized and verified. With the optimized combination of deposition parameters, homogeneous SiC coatings were deposited on relatively large area substrates of Φ50 mm and 50×50 mm with a deposition rate as high as 20 μm/min. Ablation test showed that such coatings can be used as oxidation resistance coatings in high temperature oxidizing environment.

云母模板中Cu纳米线的制备及其光学性质研究

Nanopores with diameters between 30 nm and 180 nm have been fabricated by inducing latent track with fast heavy ions and etching process in 25 μm thick,single-crystal muscovite mica.For short etching time,the nanopores are columns with circular cross section.For long etching time the cross section of nanopores becomes rhombic.Thus the shape of nanopores depends on the etching time.Cu nanowires have been fabricated with controlled dimensions by electrodeposition into the nanopores.The ultraviolet-visible lig...中文文摘：利用快重离子辐照的单晶白云母片产生潜径迹,蚀刻得到直径在30—180nm纳米孔道.孔道形状依赖于蚀刻时间,蚀刻时间短得到圆柱形孔道,蚀刻时间长得到菱柱形孔道.从而在云母模板孔道中电化学沉积得到不同直径和形状的Cu纳米线.通过紫外可见光谱分析,发现铜纳米线的尺寸和形状影响其光学性质.直径小于60nm的近似为圆柱状Cu纳米线有一个明显的表面等离子体共振峰和一个微弱的次峰.随着直径增加,菱柱状的Cu纳米线主峰有明显的红移,次峰逐渐增强.同时利用扫描电子显微镜、X射线衍射对Cu纳米线的形貌和晶体结构特征进行了表征.