Experimental and numerical investigations on dissolution and recrystallization processes of GaSb/InSb/GaSb under microgravity and terrestrial conditions

The effects of gravity and crystal orientation on the dissolution of GaSb into InSb melt and the recrystallization of InGaSb were investigated under microgravity condition using a Chinese recoverable satellite and under normal gravity condition on earth. To investigate the effect of gravity on the solid/liquid interface and compositional profiles. a numerical simulation was carried out. The InSb crystal melted at 525 degrees C and then a part of GaSb dissolved into the InSb melt during heating to 706 degrees C and this process led to the formation of InGaSb solution. InGaSb solidified during the cooling process. The experimental and calculation results clearly show that the shape of the solid/liquid interface and compositional profiles in the solution were significantly affected by gravity. Under microgravity, as the Ga compositional profiles were uniform in the radial direction. the interfaces were almost parallel. On the contrary, for normal gravity condition, as large amounts of Ga moved up in the upper region due to buoyancy, the dissolved zone broadened towards gravitational direction. Also. during the cooling process, needle crystals of InGaSb started appearing and the value of x of InxGa1-xSb crystals increased with the decrease of temperature. The GaSb with the (111)B plane dissolved into the InSb melt much more than that of the (111)A plane. (C) 2000 Elsevier Science B.V. All rights reserved.

液/液界面上可质子化的药物转移反应的研究

近年来，电荷在两互不相溶电解质溶液界面上的电化学转移过程从实验和理理论上都引起了人们的极大兴趣，这主要是由于它与许多重要的生物和化学体系密切相关，如相转移催化、化学传感器、药理学中的药物释放以及模拟生物膜等。液／液界面常被看作人工膜和生物膜的简单模型，渺液界面电分析化学的主要研究对象是界面上的电荷转移反应以及伴随发生的相关的化学反应。本文简要回顾了油液界面电分析化学研究的发展历程，其双电层结构模型，油液界面电分析化学及可质子化的药物在油液界面上转移的基本理论。用三电极系统和电化学方法研究了可质子化的药物在水/1,2m-二氯乙烷界面上转移反应的机理，以及相比和溶液的pH值对药物转移反应的影响。主要结果如下： 1．用三电极系统研究了相比（r＝0.0004一1和1～2500）对可质子化的药物吡啶在水／1，2-二氯乙烷界面（W／DCE）上的转移反应的影响，实验结果用离子分配图表示出来。结果表明：在实验范围内，随着相比的增大，吡啶以中性分子形式存在的区域增大，质子化吡啶的转移式电位降低。2．设计了一利特定的电化学池，可使水相和有机相的体积减小到100μL以下。将含有支持电解质的水溶液滴在银／氯化银电极上，然后将1，2-二氯乙烷溶液覆盖在水溶液的表面，再与有机相参比电极和对电极构成常规的三电极系统，研究了相比为1行：附吩时可质子化药物阿米替林、苯海拉明和苯海索在水／1，2-二氯乙烷界面（W／DCE）上的转移反应，确定了它们的亲油性及转移反应的机理。

应用单、双通道微／纳米管研究液／液界面上电荷转移反应

应用单、双通道微／纳米管研究液／液界面上电荷转移反应过程是目前液／液界面电化学和电分析化学领域的研究热点之一。本文简要地回顾了液／液界面电分析化学研究的发展历程，介绍了液／液界面电分析化学的基本理论和最新进展。围绕着单、双通道微／纳米管技术，分别研究了液／液界面上的电子转移、简单离子转移、加速离子转移和电荷祸合转移过程。主要结果如下：1．应用循环伏安法和微、纳米管系统地研究了二苯并十八冠六（DB18C6）加速二十种氨基酸在水／1，2一二氯乙烷（CE）界面上的转移反应，探讨了其反应机理，测量了其配合常数以及动力学常数。这一研究将对人们理解在生命体中氨基酸在载体蛋白的推动作用下越过生物膜的主动运送过程有较重要意义。2．利用循环伏安法研究了在直接支撑在双通道微米管管尖上的单微一液／液界面上的电荷转移反应，包括简单离子（四甲基按离子TMA+）转移、加速离子转移（DB18C6加速K+离子）和电子转移（二茂铁／铁氰化钾＋亚铁氰化钾体系）反应过程。此装置是目前为止最简单的可用于研究液／液界面上的电荷转移反应的装置之一。3．利用双通道微米管支撑双一微液／液界面作为产生／收集装置考察了液／液界面上的电子转移以及电荷祸合转移过程，包括电子一离子、离子一离子祸合 转移反应。该工作丰富了双通道微米管技术，并且可以通过产生／收集实验观察到一些强亲水或强憎水离子的直接转移的伏安曲线，测得它们在W/DCE界面上的转移式电位以及条件吉布斯转移能。4．初步探讨了双通道微米管作为产生／收集装置所涉及的理论及其传质过程，应用边界元法数值拟合了收集效率与管形之间的关系，通过加速离子转移实验对拟合结果进行了验证。该工作将对于今后进一步深入地应用双通道微米管技术研究液／液界面上的电荷转移反应具有一定的指导作用。

固液黏着功的Berthelot平均规则的推广及应用

以固液黏着功的Berthelot几何平均规则及其推广为基础的Zisman方程、Fowkes方程和Owens-Wendt方程是固体表面张力测定的基础.对Berthelot几何平均规则进行了进一步的推广,并以此为基础,对Zisman方程中的参数给出了推广的表示式,并对Fowkes方程和Owens-Wendt方程进行了进一步的推广.

Thermal analysis of microstructural evolution of Al2O3 surface modified layers

Solidification behavior and microstructural evolution of surface modified layers in plasma cladding technique are studied via numerical simulations. Both the coupling effect of temperature and solid volume fraction are considered in the proposed thermal analytical model, by which the transient temperature distributions are calculated and the shape of melting pool is determined. Furthermore, we perform microscopic thermal analysis on the nucleation and growth behaviors of ceramic hardening phases and dendrites, as well as the kinetics of related two-phase flow systems. By comparing with experimental observations, the evolution mechanisms of the morphology of Al2O3 ceramic hardening layer are explained. Based on the above results, a relationship among the scanning velocity of plasma stream, dendritic growth rate and the advancing speed of solid/liquid interface is found, and an energy criterion is proposed for predicting the pushing/engulfing transition of ceramic particles by grain growth fronts. (C) 2009 Elsevier B.V. All rights reserved.

Pressurized electrochromatography coupled with electrospray ionization mass spectrometry for analysis of peptides and proteins

Pressurized capillary electrochromatography (pCEC) was coupled with electrospray ionization mass spectrometry (ESI-MS) using a coaxial sheath liquid interface. It was used for separation and analysis of peptides and proteins. The effects of organic modifier and applied voltage on separation were investigated, and the effects of pH value of the mobile phase and the concentration of the electrolyte on ESI-MS signal were investigated. The resolution and detection sensitivity with different separation methods (pCEC, capillary high-performance liquid chromatography) coupled on-line with mass spectrometry were compared for the separation of a peptide mixture. To evaluate the feasibility and reliability of the experimental setup of the system, tryptic digests of cytochrome c and modified protein as real samples were analyzed by using pCEC-ESI-MS.

Extraction kinetics of thorium(IV) with primary amine N1923 in sulfate media using a constant interfacial cell with laminar flow

Extraction kinetics of thorium(IV) with primary amine N1923 in sulfate media has been investigated by a constant interfacial cell with laminar flow. Studies of interfacial tension and effects of the stirring rate, temperature, and specific interfacial area on mass transfer rate show that the most probable reaction zone takes place at the liquid-liquid interface. According to the experimental data correlated as a function of the concentration of the relevant species involved in the extraction reaction, the rate equation of extracting thorium has been obtained as follows: -d[Th(IV)]((o))/dt = 10(-3.10)center dot[Th(IV)](0.89)center dot[(RNH3)(2)SO4](0.74).

Extraction kinetics of Sc(III), Y(III), La(III) and Gd(III) from chloride medium by Cyanex 302 in heptane using the constant interfacial cell with laminar flow

The extraction kinetics of Sc, Y, La and Gd(III) from the hydrochloric acid medium using Cyanex 302 (hereafter HL) in heptane solution have been measured by the constant interfacial cell with laminar flow. Reaction regions are explored at liquid-liquid interface. Extraction regimes are deduced to be diffusion-controlled for Sc(Ill) and mixed controlled for Y, La and Gd(Ill). Extraction mechanisms are discussed according to the dimeric model of Cyanex 302 in non-polar solution. From the temperature dependence of rate measurement, the values of E-a, Delta H-+/-, Delta S-+/- and Delta G(300)(+/-) are calculated and it is found that the absolute values of these parameters keep crescent trend for Sc, Y, La and Gd(III). At the same time, it is found that it can easily achieve the mutual separation among the Sc, Y and La(III) with kinetics extraction methods.

Facilitated ion-transfer of sodium cation by (anthraquinone-1-yloxy) methane-15-crown-5 across the water/1,2-dichloroethane microinterface

The transfer of sodium cation facilitated by (anthraquinone-1-yloxy) methane-15-crown-5(L) has been investigated at the water/1,2-dichloroethane microinterface supported at the tip of a micropipette. The diffusion coefficient of (anthraquinone-1-yloxy) methane-15-crown-5 obtained was (3.42 +/- 0.20) x 10(-6) cm(2) s(-1). The steady-state voltammograms were observed for forward and backward scans due to sodium ion transfer facilitated by L with 1:1 stoichiometry. The mechanism corresponded to an interfacial complexation (TIC) and interfacial dissociation (TID) process. The association constant was calculated to be log beta(o) = 11.08 +/- 0.03 in the DCE phase. The association constant of other alkali metals (Li+, K+, Rb+) were also obtained.

Controllable synthesis of highly luminescent and monodisperse CdS nanocrystals by a two-phase approach under mild conditions

Highly luminescent and monodisperse CdS nanocrystals (see Figure) have been synthesized using a two-phase approach. The synthesis of CdS nanocrystals at the liquid-liquid interface was easy, safe, and highly reproducible, and the reaction conditions were mild and controllable.

Investigation of facilitated ion-transfer reactions at high driving force by scanning electrochemical Microscopy

The kinetics of facilitated ion-transfer (FIT) reactions at high driving force across the water/1,2-dichloroethane (W/DCE) interface is investigated by scanning electrochemical microscopy (SECM). The transfers of lithium and sodium ions facilitated by dibenzo-18-crown-6 (DB18C6) across the polarized W/DCE interface are chosen as model systems because they have the largest potential range that can be controlled externally. By selecting the appropriate ratios of the reactant concentrations (Kr c(M)+/c(DB18C6)) and using nanopipets as the SECM tips, we obtained a series of rate constants (k(f)) at various driving forces (Delta(O)(W) phi(ML+)(0') - Es, Delta(O)(W) phi(ML+)(0') is the formal potential of facilitated ion transfer and Es is the potential applied externally at the substrate interface) based on a three-electrode system. The FIT rate constants k(f) are found to be dependent upon the driving force. When the driving force is low, the dependence of 1n k(f) on the driving force is linear with a transfer coefficient of about 0.3. It follows the classical Butler-Volmer theory and then reaches a maximum before it decreases again when we further increase the driving forces. This indicates that there exists an inverted region, and these behaviors have been explained by Marcus theory.

A nonmonotonic dependence of standard rate constant on reorganization energy for heterogeneous electron transfer processes on electrode surface

In the present work a nonmonotonic dependence of standard rate constant (k(0)) on reorganization energy (lambda) was discovered qualitatively from electron transfer (Marcus-Hush-Levich) theory for heterogeneous electron transfer processes on electrode surface. It was found that the nonmonotonic dependence of k(0) on lambda is another result, besides the disappearance of the famous Marcus inverted region, coming from the continuum of electronic states in electrode: with the increase of lambda, the states for both Process I and Process II ET processes all vary from nonadiabatic to adiabatic state continuously, and the lambda dependence of k(0) for Process I is monotonic thoroughly, while for Process II on electrode surface the lambda dependence of k(0) could show a nonmonotonicity.

Mass transfer kinetics of yttrium(III) using a constant interfacial cell with laminar flow. Part II. Extraction with Cyanex 272

The yttrium(III) extraction kinetics and mechanism with bis-(2,4,4-trimethyl-pentyl) phosphinic acid (Cyanex 272, HA) dissolved in heptane have been investigated by constant interfacial cell with laminar flow. The data has been analyzed in terms of pseudo-first order constants. Studies on the effects of stirring rate, temperature, acidity in aqueous phase, and extractant concentration on the extraction rate show that the extraction regime is dependent on the extraction conditions. The plot of interfacial area on the rate has shown a linear relationship. This fact together with the strong surface activity of Cyanex 272 at heptane-water interfaces has made the interface the most probable location for the chemical reactions. The forward, reverse rate equations and extraction rate constant for the yttrium extraction with Cyanex 272 have been obtained under the experimental conditions. The rate-determining step has been also predicted from interfacial reaction models. The predictions have been found to be in good agreement with the rate equations obtained from experimental data, confirming the basic assumption that the chemical reaction is located at the liquid-liquid interface.