A mössbauer investigation of non-bridging oxygens in Na2O-Fe2O3-B2O3 glasses

Mössbauer measurements of sodium borate glasses 4 Fe₂O₃· x Na₂O· (96-x) B₂O₃ (x=6, 10, 15, 20, 25, 30) have been carried out. It was found that Fe³⁺ is present in both octahedral and tetrahedral sites, whereby the tetrahedral sites are preferred. In the range of Na₂O contents higher than about 15 mol%, the isomer shifts and quadrupole splittings for Fe³⁺ decrease continuously with increasing Na₂O concentration. These changes could be attributed to the formation of non-bridging oxygens (NBO) in the neighborhood of ferric ions. Increasing Na₂O content thus gives rise to more NBO increasing the symmetry of the iron polyhedra.     

The exact Mössbauer recoilless fraction in fractals ATT≠0

In this paper a detailed calculation of the Mössbauer fraction for a general non-Euclidean dimensionality is given. The result shows that the contributions to the Mössbauer effect in fractals come from three possible types of transition.     

以双硫酯为链转移剂的活性自由基聚合

合成并研究了两种双硫酯链转移剂的纯化方法 ,进行了多种单体以双硫酯为链转移剂的活性自由基聚合及嵌段共聚 .发现以PhC(S)SC(CH3) 2 Ph为链转移剂的效果比PhC(S)SCH(CH3)Ph好 ,聚合产物的多分散性系数较小 .引发剂与链转移剂的摩尔数比为 1∶3 5～ 1∶4 2时 ,得到多分散性系数小 ,实测分子量与理论分子量相近的聚合产物 .聚合物的分子量随时间和转化率的增加而增加 ,加入第二单体形成嵌段共聚物 ,具有活性聚合特征 .聚甲基丙烯酸酯大分子引发剂引发丙烯酸酯单体聚合时 ,聚合速度最快 .     

Investigation of the solid-solid surface adsorption of Eu2O3 on amorphous Al2O3

Solid-solid surface adsorption of Eu₂O₃ on anorphous Al₂O₃ have been investigated by the Mössbauer effect, X-ray diffraction analysis (XRD.) and Laser Raman Spectroscopy (LRS). The results of these studies indicate that the structure of EU₂O₃ dispersed onto the support surface depends on the structure of support and that there is an inductive effect of the support on the structure of the Eu₂O₃.     

A Mössbauer study of spin-pinning in the oxide surface layer on fine iron particles

Fine α-Fe particles coated with an oxide surface layer were prepared by the evaporation technique. The spin pinning in the oxide surface layer were studied by means of the Mössbauer effect in an applied field of 6T during a thermal-cycle process. The anisotropy energy on the surface was estimated.     

用YAG激光制备类金刚石薄膜及其光学折射率研究

用高功率的Ｎｄ＾３＋：ＹＡＧ脉冲激光轰击真空室内的石墨靶，形成激光等离子体雾状物质，在硅衬底上沉积形成类金刚石薄膜，用椭圆偏振光谱法测量不同衬底温度下制备的系列样品的厚度和折射率，发现随着衬底温度的升高，薄膜的厚度减小而的折射率增大，这种可以控制折射率米化的薄膜，可能为光学增透增反膜的制备提供一种新方法。     

五磷酸镧钕激光晶体发光的温度效应

研究了低温下Nd0.9 La0.1 P5O14晶体中,Nd3+离子在0.9,1.05,以及1.35μm附近发光光谱的精细结构及相应的跃迁过程,并与Nd:YAG晶体中Nd3+离子发光光谱及相应的跃迁作了比较。在77K-500K的温度变化范围内,研究了Nd3+在两种晶体中最强的发光线的温度依赖关系,发现相反的变化规律,指出这是与两种晶体的结构及跃迁过程有关。     

多孔硅表面Ag层对吸附其上的若丹明B染料分子表面增强Raman散射的影响

采用溶液电镀方法在多孔硅表面制备纳米尺寸的银颗粒,测量了不同镀银多孔硅表面吸附的ＲｈＢ染料分子以及固态的ＲｈＢ染料的Ｒａｍａｎ散射谱。在相同的激发强度下,固态ＲｈＢ染料的Ｒａｍａｎ散射最弱,而镀银的多孔硅表面具有明显的增强效果（～１０＾４）。     

The analysis of two-dimensional two-phase flow in horizontal heated tube bundles using drift flux model

This paper presents the experimental study and numerical simulation of two-dimensional two-phase flow in horizontal heated tube bundles. In the experiments, two advanced measuring systems with a single-fibre optical probe and a tri-fibre-optical-probe were developed to measure respectively the local void fraction and vapor bubble velocities among the heated tube bundles. In accordance with the internal circulation characteristics of two-phase flow in the tube bundles, a mathematical model of two-dimensional two-phase low Reynolds number turbulent flow based on the modified drift flux model and the numerical simulation method to analyze the two-phase flow structures have been developed. The modified drift flux model in which both the acceleration by gravity and the acceleration of the average volumetric flow are taken into account for the calculation of the drift velocities enables its application to the analysis of multi-dimensional two-phase flow. In the analysis the distributions of the vapor-phase velocity, liquid-phase velocity and void fraction were numerically obtained by using the modified drift flux model and conventional drift flux model respectively and compared with the experimental results. The numerical analysis results by using the modified drift flux model agree reasonably well with the experimental investigation. It is confirmed that the modified drift flux model has the capability of correctly simulating the two-dimensional two-phase flow. Received on 3 September 1998     

高频溅射生长ZnS:Tb,F薄膜的结构与发光

本文采用X射线衍射和阴极射线发光技术对溅射法生长的ZnS:Tb,F薄膜的发光光谱和薄膜的微观结构进行了研究,得出了激晶薄膜的晶粒尺寸与发光强度的关系.讨论了稀土离子的价态对掺杂稀土微晶薄膜的发光性质与晶粒尺寸的关系的影响.