Atomic-scale simulation of nano-grains:structure and diffusion properties

Nanograins are characterized by a typical grain size from lto 100 nm.Mclecular dynamics aimubations have been carried out for the nanograin sphere with the diameters from 1.45 to 10.12 nm.We study the influence of grain size on structure and diffusion properties of the nanograins.The results reveal that as the grain size is reduced,the fraction of grain surface increases significantly,and the surface width is approximately constant；the diffusicn coefficlent is increased sharply,and the relation of the diffusion coefficient and the grain size is close to exponential relation below 10nm.     

纳米Zr-V-O粉末的XRD及TG-DSC研究

利用机械合金化制备纳米Zr-V粉末，对制备过程的材料进行物相分析和热分析试验。初始粉末Zr（150μm）和V（150μm）元素粉末（纯度99．15％）按原子比1：2或1：1进行混合后在氩气气氛中放入SimoloyerCMol—2球磨仓中，按几种不同的试验条件进行球磨。同时在997K和1047K下热处理40min和1h，并对热处理前后的粉末进行了物相和TG-DSC实验分析。     

Raman properties embeddedof GaSb nanoparticlesin SiO2 films

The Raman shifts of nanocrystalline GaSb excited by an Ar^ ion laser at wavelengths 514.5, 496.5, 488.0, 476.5,and 457.9nm are studied by an SPEX-1403 laser Raman spectrometer respectively, and they are explained by phonon confinement, tensile stress, resonant Raman scattering and quantum size effects. The Stokes and anti-Stokes Raman spectra of GaSb nanocrystals strongly support the Raman feature of GaSb nanocrystals. The calculated optical spectra compare well with experimental data on Raman scattering GaSb nanocrystals.     

理想的胰岛素晶体

在自然界或实验室内 ,“理想化”总是一个难以实现的概念 .但最近美国休斯顿大学的P .Vekilov教授及其同事们发现 ,他们常常可以将胰岛素晶体生长成理想的晶体形式 .他们让胰岛素蛋白质在一个已有的胰岛素晶体的螺旋位错缺陷处进行生长 ,蛋白质将绕着这个缺陷发生晶化并形成一个理想晶状胰岛素 .这是因为螺旋位错常常使晶层间产生一个微小的角度偏差 .对于大多数的晶体来说 ,晶层间的相互作用能促进晶体生长时界面间的配置 ,并导致晶层阶跃发生束缚和形成一个有条纹的晶体 .除此之外 ,在溶液中输入被溶解物质也能引起晶层阶跃的约束 .胰岛…     

单光子态的产生与测量

报道了通过自发参量下转换产生单光子态的实验研究,使用中心波长425 nm的飞秒脉冲泵浦Ⅰ类非共线相位匹配的BBO晶体,在实验上得到单光子计数率为2.978×10-4,并分析了实验中的相关问题.     

γ-辐照对纯Y_2SiO_5和Eu~(3+)∶Y_2SiO_5晶体光谱性能的影响

研究了γ-辐照前后纯Y2SiO5和Eu3+掺杂的Y2SiO5晶体吸收光谱的变化,辐照后,未退火和氢气退火的纯Y2SiO5晶体在260~270 nm和320 nm波段产生了附加吸收峰,分别是由F心和O-心的吸收引起的;经过空气退火的纯YSO晶体中,由于消除了氧空位,因此辐照后没有出现色心吸收峰。在Eu3+∶Y2SiO5晶体中,不但有相同的F心和O-心吸收峰,而且还有Eu2+离子在300 nm和390 nm的吸收峰。随着辐照剂量的增加,色心附加吸收峰增强。空气退火能减少Eu3+∶Y2SiO5晶体中的色心,而氢气退火能增加色心。     

激光晶体YAG中Er3+的辐射跃迁

本文讨论和分析了激光晶体YAG中Er3+离子的激光上能级的4S3/2、4I11/2和4I13/2辐射跃迁的有关因素。     

Fabrication of Compound Lattice by Holographic Lithography

Some compound lattices in photonic crystals with large complete photonic band gaps, such as the diamond structure and the two-dimensional hexagonal compound structure, is desired for fabrication. A novel method for fabrication of compound lattices by holographic lithography is reported. The key point is phase modulation by photoelectrical control and multiple-exposure techniques. This technique introduces many advances: for instance,using the same coherent beams and without changing the position of the sample during multiple-exposure.     

Pyroelectricity and Spontaneous Polarization in [111] Oriented 0.955 Pb（Zn1/3Nb2/3）O3-0.045PbTiO3 Single Crystals

We report that the measurements of the pyroelectric current of the pre-poled [111]-oriented 0.955 Pb（Zn1/3Nb2/3） O3-0.045 PbTiO3 （PZN-4.5%PT） single crystals can shed some light on the phase transition and spontaneous polarization characters of this material in a similar way to measures of remanent polarization and dielectric properties. The pyroelectric current is measured and the corresponding spontaneous polarization is calculated as a function of temperature with various poling fields added during cooling the sample from 200℃ to room temperature. Critical electric field of 0.061 k V/cm is found to be essential to induce the intermediate ferroelectric orthorhombic phase between the ferroelectric rhombohedral and tetragonal phases. Below the critical field, the polarization increases almost linearly with the increase of poling field. At the critical field, the polarization at 30OC increases abruptly from 14μC/cm^2 for a poling field of O.06kV/cm to 29.5μC/cm^2 for a poling field of 0.061 kV/cm, and afterwards, increases slowly and saturates to 31 μC/cm^2 for poling fields beyond 0.55 kV/cm.     

Nano-tribological study on a super-hydrophobic film formed on rough aluminium substrates

A novel super-hydrophobic stearic acid (STA) film with a water contact angle of 166^o was prepared by chemical adsorption on aluminum wafer coated with polyethyleneimine (PEI) film. The micro-tribological behavior of the super-hydrophobic STA monolayer was compared with that of the polished and PEI-coated Al surfaces. The effect of relative humidity on the adhesion and friction was investigated as well. It was found that the STA monolayer showed decreased friction, while the adhesive force was greatly decreased by increasing the surface roughness of the Al wafer to reduce the contact area between the atomic force microscope (AFM) tip and the sample surface to be tested. Thus the friction and adhesion of the Al wafer was effectively decreased by generating the STA monolayer, which indicated that it could be feasible and rational to prepare a surface with good adhesion resistance and lubricity by properly controlling the surface morphology and the chemical composition. Both the adhesion and friction decreased as the relative humidity was lowered from 65% to 10%, though the decrease extent became insignificant for the STA monolayer. The project supported by the National Natural Science Foundation of China (50375151, 50323007, 10225209) and the Chinese Academy of Sciences (KJCX-SW-L2)