Corrosion inhibition of carbon steel in tetra-n-butylammonium bromide aqueous solution by benzotriazole and Na3PO4

The corrosion inhibition behavior of benzotriazole, Na3PO4 and their mixture on carbon steel in 20 wt.% (0.628 mol l(-1)) tetra-n-butylammonium bromide aerated aqueous solution was investigated by weight-loss test, potentiodynamic polarization measurement, electrochemical impedance spectroscopy and scanning electron microscope/energy dispersive X-ray techniques. The inhibition action of BTA or SP or inhibitors mixture on the corrosion of carbon steel is mainly due to the inhibition of anodic process of corrosion. The results revealed that inhibitors mixtures have shown synergistic effects at lower concentration of inhibitors. At 2 g l(-1) BTA and 2 g l(-1) SP showed optimum enhanced inhibition compared with their individual effects.

Experimental Investigation on Propane Hydrate Dissociation by High Concentration Methanol and Ethylene Glycol Solution Injection

The dissociation behaviors of propane hydrate by high concentration alcohols inhibitors injection were investigated. Methanol (30.0, 60.1, 80.2, and 99.5 wt %) and ethylene glycol (30.0, 60.1, 69.8, 80.2, and 99.5 wt %) solution were injected, respectively, as alcohols inhibitors in 3.5 L transparent reactor. It is shown that the average dissociation rates of propane hydrate injecting methanol and ethylene glycol solution are 0.02059-0.04535 and 0.0302-0.0606 mol.min(-1).L-1, respectively. The average dissociation rates increase with the mass concentration increase of alcohols solution, and it is the biggest when 99.5 wt % ethylene glycol solution was injected. The presence of alcohols accelerates gas hydrate dissociation and reduces the total need of external energy to dissociate the hydrates. Density differences act as driving force, causing the acceleration effects of ethylene glycol on dissociation behaviors of propane hydrate are better than that of methanol with the same injecting flux and mass concentration.

A three-dimensional analytical solution of the microheater temperature before bubble nucleation

A three-dimensional analytical solution of the microheater temperature based on heat diffusion equation is developed and compared with experimental results. Dimensionless parameters are introduced to analyze the temperature rise time and the distribution under steady state. To study the microheater temperatures before bubble nucleation, a set of working fluids and microheaters are considered. It is shown that the dimensionless time xi(-)(0) required for the temperature rise from room to 95% of the steady state temperature is about 75, not dependent on working fluids and microheaters. Heat transfer to the surrounding liquid is mainly caused by conduction, not by convection and radiation mechanisms. The microheater length affects the surface temperature uniformity, while its width influences the steady temperatures significantly, yielding the transition from heterogeneous to homogeneous nucleation mechanism from square microheaters to narrow line microheaters. 

Influence of 3A molecular sieve to tetrahydrofuran(THF) hydrate formation

Visual observation of the THF hydrate formation process in the presence of a 3A molecular sieve has been made at normal atmosphere and below a temperature of zero by microscopy. The results indicate that a 3A molecular sieve can induce the nucleation of the THF hydrate and promote the THF hydrate growth. With the existence of a 3A molecular sieve, the growth rate of THF hydrate is between 0.01 and 0.05 mu m/s. In comparison with the system without any 3A molecular sieve, the growth rate increases about 4 nm/s. After the THF hydrate grows into megacryst, the crystals will recombine and partially change under the same condition.

Study on the kinetics of hydrate formation in a bubble column

Gas hydrate formation experiments were performed using methane in the presence of tetrahydrofuran (THF) in aqueous solution in a transparent bubble column in which a single pipe or a sintered plate was used to produce bubbles. The mole fraction of THF in aqueous solution was fixed at 6%. The hydrate formation kinetic behaviors on the surface of the rising bubble, the mechanical stability of hydrate shell formed on the surface of the bubble, the interactions among the bubbles with hydrate shell were observed and investigated morphologically. The rise velocities of individual bubbles with hydrate shells of different thickness and the consumption rates of methane gas were measured. A kinetic model was developed to correlate the experimentally measured gas consumption rate data. It was found that the hydrate formation rate on the surface of the moving bubble was high, but the formed hydrate shell was not very easy to be broken up. The bubbles with hydrate shells tended to agglomerate rather than merge into bigger bubble. This kind of characteristic of hydrate shell hindered the further formation of hydrate and led to the lower consumption rate of methane. The consumption rate of methane was found to increase with the decrease of temperature or increase of pressure. The increase of gas flux led to a linear increase in consumption rate of methane. It was demonstrated that the developed kinetic model could be used to correlate the consumption rate satisfyingly.

Synthesis of novel hexagon SnO2 nanosheets in ethanol/water solution by hydrothermal process

The novel hexagon SnO2 nanosheets are successfully synthesized in ethanol/water solution by hydrothermal process. The samples are characterized by X-ray diffraction (XRD), infrared ray (IR) and transmission electron microscopy (TEM). By changing the reaction conditions, the size and the morphology can be controlled. Comparison experiments show that when the temperature increased from 140 degrees C to 180 degrees C, the edge length of the hexagon nanoparticles increases from 300-450 nm to 700-900 nm. On the other hand, by adjusting the ratios of water to ethanol from 2 to 0.5, SnO2 nanoparticles with different morphologies of triangle and sphere are obtained. When the concentration of NaOH is increased from 0.15 M to 0.30 M, a hollow ring structure can be obtained. (c) 2006 Elsevier B.V. All rights reserved.

两亲性三嵌段共聚物在选择性稀溶液中的自组装及应用

本论文主要研究了ABA和ABC型两亲性三嵌段共聚物在选择性稀溶液中的自组装行为，得到了多种形态新颖、结构复杂多样的胶束，研究了这些复杂胶束的形成过程，探讨了影响胶束形态的各种因素并通过适当的方法对胶束形态进行调控。研究了聚乙烯基毗陡（P4VP）／聚苯乙烯（PS）三嵌段共聚物P4VP-b-PS-b-P4VP在二氧六环／水中的自组装行为，成功得到了嵌段共聚物环状胶束，并通过实验研究了环状胶束的形成过程。结果表明，胶束形态依赖于退火时间的长短。随着退火时间的延长，胶束结构从棒状过渡到环形结构。以实验结果为基础提出了环状胶束形成的新的机理，即囊泡塌陷形成环。同时，通过改变实验条件还得到了一些新型的环状复合结构，如环套环形、鸟状、哑铃形、戒指形、网络状等结构，并得到了与计算机模拟一致的结果。通过不同的方法对ABA型三嵌段共聚物（P4VP-b-PS-b-P4VP）在选择性溶液中的自组装胶束形态进行调控：首先，详细研究了P4VP-b-PS-b-P4VP在不同的共溶剂中的自组装行为。结果表明通过单纯改变共溶剂的性质可以很方便地调节胶束的形态，得到了球、棒、囊泡等结构。并用混合溶剂的方法得到了长度和直径可控的纳米线胶束。同时，通过加入第二种选择性溶剂（核层嵌段PS的选择性溶剂甲苯）的方法使形成胶束的核层嵌段在胶核中的伸展程度增加，从而使胶束形态发生转变。其次，研究了加入表面活性剂十五烷基苯酚（PDP）以构建分子间氢键来调节P4VP-b-PS-b-P4VP的胶束形态。结果表明，通过调节PDP的加入量可以使胶束形态发生从球到棒，到网络状、再到囊泡结构的转变。通过实验对比系统地研究了PDP的加入对胶束形态转变的影响，提出了相应的形态转变机理。再次，研究了不同分子量的嵌段共聚物之间共混及共聚物与均聚物共混对胶束形态的影响。结果表明加入亲油嵌段的均聚物对共聚物胶束形态影响非常明显，胶束形态与加入的均聚物的分子量及加入量直接相关。同时得到了一些新形态的胶束，如海绵状、笼子状等。共聚物共混的研究结果表明：通过两种不同分子量的共聚物共混可以得到这两种共聚物胶束的过渡态结构。用共聚物混合的方法还可以得到一些具有生物模拟性的胶束结构，如乌贼状、章鱼状等。这加深了人们对囊泡的形成机理及各种胶束形态之间形态转变的认识。P4VP-b-PS-b-P4VP通过在二氧六环／水中的自组装形成了囊泡，结果表明囊泡的尺寸依赖于初始状态下共聚物在共溶剂中的浓度及退火时间。除得到常规的球形囊泡外，还得到一些非球形囊泡，如长条形、三角形、项链形等囊泡结构。结合计算机模拟的方法研究了囊泡的形成机理，发现这些不同结构的囊泡的形成是由于初始状态下密度涨落所引起的。研究了实验中经常出现的各种胶束形态共存现象的原因，发现体系中亚稳态的存在是多形态共存的重要原因之一。通过聚苯乙烯一左聚乙烯基毗睫一左聚氧乙烯（PS一b一PZVP一b一PEO）在THF／水中的二次自组装首次得到了一种具有生物模拟性的巨大的节状蠕虫胶束（SWM）。研究发现，SWM是由重复单元盘状结构和丝状结构相连组成的。最令人吃惊的是这种SWM与自然界中的一些生命体如蛆叫、蛹、昆虫类的幼虫结构非常相似。通过对SWM形成过程中的中间态胶束结构的深入研究发现SWM是由球形胶束通过二次自组装形成的。SWM的形成过程可以分为三个阶段：ABC三嵌段共聚物先组装形成球形结构；这些球型结构粘连在一起形成梭形的中间结构；这些梭状中间结构中的球经过重组和重新调整各嵌段的排布最终形成SWM。用所得到的嵌段共聚物胶束为模板，采用无电沉积的方法成功制备了各种形态的金属一有机高分子纳米复合材料。用简单的方法还得到了导电金属金一银的双金属纳米结构材料。这些纳米结构材料在微电子器件等领域有潜在应用价值。以上研究结果丰富了人们对嵌段共聚物在选择性介质中自组装行为的理解，为人们提供了对生物材料自组装本质的理解的依据。这在两亲性分子在溶液中自组装的基础研究方面以及基于这些自组装形态而构建结构及功能更复杂的纳米结构材料等方面都有一定的意义。

EER studies of the single quantum well GaAs/AlxGa1-xAs electrode/nonaqueous solution interface

The interfacial behavior of the single quantum well (SQW) GaAs/AlxGa1-xAs electrode in HQ/BQ and Fc/Fc(+) electrolytes was characterized respectively by studying the quantum confined Stark effect and Franz-Keldysh oscillation with electrolyte electroreflectance spectroscopy. The interaction of the surface state of the SQW electrode with redox species and its effects on the distribution of external bias at the interface of the SQW electrode are discussed.

A Novel Power Supply Solution of a Passive RFID Transponder

This paper presents a power supply solution for fully integrated passive radio-frequency identification(RFID) transponder IC,which has been implemented in 0.35μm CMOS technology with embedded EEPROM from Chartered Semiconductor.The proposed AC/DC and DC/DC charge pumps can generate stable output for RFID applications with quite low power dissipation and extremely high pumping efficiency.An analytical model of the voltage multiplier,comparison with other charge pumps,simulation results,and chip testing results are presented.

Characterization of CdSe and CdSe/CdS core/shell nanoclusters synthesized in aqueous solution

CdSe nanoclusters overcoated with CdS shell were prepared with macapoacetic acid as stabilizer. The optical properties of CdSe nanoclusters and the influence of CdS shell on the electronic structures of CdSe cores were studied by optical absorption, photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. Based on PL and PLE results and the theoretical calculation on fine structure of bandedge exciton, a model of formation of excimer within the small clusters was proposed to explain the large Stokes shift of luminescence from absorption edge observed in PL results. (C) 2000 Elsevier Science B.V. All rights reserved.