含Li的Al-Zn-Mg-Cu合金沉淀析出过程的定量分析

应用小角度X射线散射技术结合TEM分析定量的描述Al-Zn-Mg-Cu-Li合金时效过程中析出相尺寸分布和形貌等信息。通过分析确定合金在几种时效状态下析出相为轴比在0．2～0．4之间的扁回转椭球形。确定了析出相特征尺寸的对数正态分布和质量依回转半径的Maxwell分布。并分析分布曲线随动力强度Ks的变化特征，可以看出，析出相尺寸和质量分布曲线基本满足随动力强度增加，几何平均值增加，分布范围变宽。     

丁基罗丹明B-AuI4-缔合纳米粒子体系的极谱猝灭效应研究

在0．1mol／LH2SO4介质中，丁基罗丹明B(RBB)在-0．59伏产生1个单扫描极谱峰。当有AuI^-4存在时，AuI^-4与RBB^ 主要通过静电引力形成疏水性的AuI4—2RBB缔合物分子。AuI4—2RBB存在较强的分子间作用力和疏水作用力而生成紫红色的(AuI4—RBB)n纳米微粒，在470nm处产生1个瑞利散射峰，在610nm处产生1个共振瑞利散射峰；而在-0．59伏处的极谱峰降低。这是由于该紫红色复合纳米微粒形成所致。当纳米微粒体系加入乙醇后，体系的瑞利散射峰和共振瑞利散射峰消失，极谱峰、同步荧光峰和颜色恢复，由于乙醇而致使紫红色的(AuI4-RBB)n纳米微粒分解为红色AuI4—RBB分子。研究结果表明，紫红色(AuI4-RBB)。纳米粒子的形成是其极谱猝灭和共振瑞利散射效应的根本原因。     

Structural and magnetic characterization of norbornene-deuterated norbornene dicarboxylic acid diblock copolymers doped with iron oxide nanoparticles

A series of iron oxide doped norbornene (NOR)/deuterated norbornene dicarboxylic acid (NORCOOH) diblock copolymers were synthesized and characterized by X-ray photoelectron spectroscopy (XPS), small angle neutron scattering (SANS) and superconducting quantum interference device (SQUID) experiments. γ-Fe₂O₃ nanoparticles were synthesized within the microdomains of diblock copolymers with volume fractions of NOR/NORCOOH 0.64/0.36, 0.50/0.50 and 0.40/0.60. A spherical nanoparticle morphology was displayed in the polymer with 0.64/0.36 volume fraction. Polymers with 0.50/0.50 and 0.40/0.60 volume fractions exhibited interconnected metal oxide nanostructures. The observed changes in the shape and peak positions of the small-angle neutron scattering profiles of polymers after metal doping were related to the scattering from the metal oxide particles and to the possible deformed morphologies due to the strong interparticle interactions between metal particles, which may influence the polymer microphase separation. The combined scattering from both polymer domains and magnetic particles was depicted in SANS profiles of metal oxide doped polymers. γ-Fe₂O₃ containing block copolymers were superparamagnetic at room temperature. An increase in the blocking temperature (T_b) of interconnected nanoparticles was observed and was related to the interparticle interactions, which depends on the average distance (d) between particles and individual particle diameter (2R). The sample with volume fraction of 0.4/0.6 have the lowest d/(2R) ratio and exhibit the highest T_b at 115 K.     

Real-time monitoring of segmental dynamics during crystallization of poly(l(-)-lactide) by simultaneous DRS/SALS technique

A novel experimental set up consisting of dielectric spectroscopy and small angle light scattering (or potentially any other optical technique used in combination) is introduced. The sample is enclosed in a Dielectric-Optical-Shear (DOS) cell capable of precisely controlling temperature and thickness. This method allows for simultaneous in situ, real-time monitoring of the changes in the molecular dynamics and corresponding development of supramolecular structure of a given polymer system during various time-sensitive processes. The DOS cell is utilized to investigate relaxation phenomena related to the glass transition, T_g, of poly(l(−)-lactide) during isothermal crystallization under quiescent, partially constrained conditions. A decrease in T_g was observed in situ via a shift in dipolar relaxation to higher frequency (confirmed calorimetrically, ex situ). The shift was most rapid in the spherulitic impingement stage of crystallization, at approximately 30% overall crystallinity.     

吡啶-氯化钾水溶液/n型硫化镉电极界面上的表面增强喇曼散射

本文研究了在吡啶-KC1水溶液中吡啶吸附在n-CdS电极上的表面增强喇曼散射(SERS)。在光照下,CdS电极经过正极化予处理数分钟,就能观察到吡啶吸附在CdS电极上的很强的SERS谱。其特征峰是1010和1036cm~(-1)与纯吡啶的喇曼特征峰991,1030cm~(-1)相比有了明显位移。又SERS谱随着吡啶浓度的增加而增强。外加电位对SERS也有一定影响,其曲线形状与CdS的I～V曲线很相似。对这些实验结果,本文用n型CdS电极的光电化学特性进行了初步的考察和讨论。     

聚甲基丙烯酰氧乙基二甲基丁烷基溴化铵共振光散射法测定核酸

通过光谱法研究聚甲基丙烯酰氧乙基二甲基丁烷基溴化铵(PMDB)和核酸的作用。结果表明通过共振光散射法用PMDB检测微量的DNA可靠、准确和简单。     

An accelerated algorithm for full band electron–phonon scattering rate computation

Computing scattering rates of electrons and phonons stands at the core of studies of electron transport properties. In the high field regime, the interactions between all electron bands with all phonon bands need to be considered. This full band interaction implies a huge computational burden in calculating scattering rates. In this study, a new accelerated algorithm is presented for this task, which speeds up the computation by two orders of magnitude (100 times) and dramatically simplifies the coding. At the same time, it visually demonstrates the physical process of scattering more clearly.     

Interpretation of quasi-elastic light scattering data for flexible chains: model dependence

The autocorrelation functions and corresponding relaxation times obtained from the forward depolarized quasi-elastic light scattering experiment are exhibited for two quite similar models of flexible polymer chains in solution. A very small change in the chain dynamics is found to be sufficient to change the relaxation time from a relatively short time independent of chain length, with an autocorrelation function suggestive of an unweighted sum of contributions from all the relaxation times in the spectrum of chain motion, to a long time with an autocorrelation function identical with that for the end-to-end vector, strongly dependent upon chain length and dominated by the longest relaxation time in the spectrum. These results raise the question whether widely-used models in which information about short-range chain structure and motion is deliberately omitted can be expected to be appropriate for the interpretation of depolarized scattering experiments.     

High quality double wall carbon nanotubes with a defined diameter distribution by chemical vapor deposition from alcohol

We have synthesized double wall carbon nanotubes (DWNTs) with few defects and little amorphous carbon by hot wall chemical vapor deposition (CVD) of alcohol. Catalysts for the DWNT growth were made from cobalt and molybdenum acetates. Scanning electron microscopy, transmission electron microscopy, multi frequency resonance Raman spectroscopy and optical absorption spectroscopy were used for characterization of the product with regard to DWNT yield, the nanotube diameter distribution, defect concentration and amorphous carbon content. Base pressures lower than 1 × 10⁻⁵ mbar in the CVD reactor considerably suppress defects in the DWNTs. Optimized growth conditions for DWNT formation are presented.