聚苯胺修饰电极膜厚度的理论公式及其验证

本文提出了用于计算聚苯胺修饰电极膜厚度的理论公式,它适用于恒电流法和循环扫描伏安法制得的膜,经验证理论和实验相符合.文中还讨论了PANI密度及摩尔体积的计算和电化学测定方法.     

稀土-过渡族合金双层磁光膜的交换耦合性能分析

稀土-过渡族合金GdFeCo/TbFeCo双层膜交换耦合性能的控制是实现中心孔探测型磁超分辨的关键.分别从理论和实验的角度研究了两层膜的交换耦合性能.理论计算结果表明, 在温度升高到接近读出层补偿点时, 由于两层之间的交换耦合, 读出层磁化方向由室温时的面内变为垂直于膜面.实验得到了类似的结果, 理论和实验结果有很好地吻合.另外, 还分析了两层膜交换耦合性能的影响因素, 分析结果对以后的实验有很好的指导作用.     

超临界CO_2诱导相转化法制备聚苯乙烯膜及膜体系的相图计算

以甲苯为溶剂,利用超临界CO_2诱导相转化法制备了多孔非对称聚苯乙烯膜.通过扫描电镜对膜结构进行了表征,探讨了不同温度、压力和铸膜液中聚苯乙烯浓度对膜形态、孔径分布及膜孔隙率的影响;同时,基于Tompa扩展的Flory-Huggins聚合物溶液理论计算了聚苯乙烯/超临界CO_2/甲苯铸膜体系的三元相图.研究表明,在温度为35~65℃、压力为8~16 MPa及聚合物质量分数为15%~35%条件下,制备的聚苯乙烯膜截面呈胞腔状孔结构,孔隙率为53.54%~84.67%,且孔隙率随温度、压力和聚苯乙烯浓度均呈现出先增大后减小的趋势.相图计算结果表明,温度对体系双节线位置的改变影响较小,而压力对其影响相对较大.     

纳滤膜对电解质溶液分离特性的理论研究(II): 混合电解质溶液

假定纳滤膜具有狭缝状孔, 使用纯水透过系数、膜孔径及膜表面电势来表征纳滤膜的分离特征, 用流体力学半径和无限稀释扩散系数表征了离子特性. 采用扩展Nernst-Planck方程、Donnan平衡模型和Poisson-Boltzmann理论描述了混合电解质溶液中离子在膜孔内的传递现象, 计算了三种商用纳滤膜(ESNA1-LF, ESNA1和LES90)对同阴离子、同阳离子和含四种离子的混合电解质体系中离子的截留率, 并与实验数据进行了比较. 计算结果表明, 电解质溶液中离子在纳滤膜孔内传递的主要机理是离子的扩散和电迁移, 纳滤膜对混合电解质溶液中离子的分离效果主要由空间位阻和静电效应决定. 该模型在低浓度时对含一价离子的混合电解质溶液通过纳滤膜的截留率计算结果比较准确, 但对高浓度或含高价离子的混合电解质溶液则偏差较大.     

纳滤膜对电解质溶液分离特性的理论研究(I): 单一电解质溶液

电解质溶液在纳滤膜中的截留率对于膜法海水淡化和重金属离子的脱除非常重要. 本文假定膜具有狭缝状孔, 采用扩展Nernst-Planck方程、Donnan平衡模型和Gouy-Chapman理论来描述电解质溶液中离子在膜孔内的传递现象. 使用纯水透过系数、膜孔径及膜表面电势来表征纳滤膜的分离特征, 这三个参数可通过Levenberg-Marquardt方法由实验数据关联得到. 本文使用该模型计算了两种商用纳滤膜(NF45和SU200)对1-1型(NaCl, KCl, LiCl), 2-1型(K₂SO₄)和2-2型(MgSO₄)单一电解质溶液的截留率, 并与实验数据进行了比较, 两者吻合较好. 计算结果表明电解质溶液中离子在纳滤膜孔内传递的主要机理是离子的扩散和电迁移, 纳滤膜对电解质溶液中离子的分离效果主要由空间位阻和静电效应决定. 该模型在低浓度时对电解质溶液通过纳滤膜的截留率计算结果较准确, 但对高浓度电解质溶液则偏差较大.     

纳滤膜对电解质溶液分离特性的理论研究(Ⅰ):单一电解质溶液

电解质溶液在纳滤膜中的截留率对于膜法海水淡化和重金属离子的脱除非常重要.本文假定膜具有狭缝状孔,采用扩展Nernst-Planck方程、Donnan平衡模型和Gouy-Chapman理论来描述电解质溶液中离子在膜孔内的传递现象.使用纯水透过系数、膜孔径及膜表面电势来表征纳滤膜的分离特征,这三个参数可通过Levenberg-Marquardt方法由实验数据关联得到.本文使用该模型计算了两种商用纳滤膜(NF45和SU200)对1-1型(NaCl,KCl,LiCl),2-1型(K2SO4)和2-2型(MgSO4)单一电解质溶液的截留率,并与实验数据进行了比较,两者吻合较好.计算结果表明电解质溶液中离子在纳滤膜孔内传递的主要机理是离子的扩散和电迁移,纳滤膜对电解质溶液中离子的分离效果主要由空间位阻和静电效应决定.该模型在低浓度时对电解质溶液通过纳滤膜的截留率计算结果较准确,但对高浓度电解质溶液则偏差较大.     

荷电膜的膜电位研究

膜电位是表征荷电膜传递现象的重要参数之一.本文简要介绍了膜电位理论基础,包括T.M.S.理论和不可逆热力学理论.分别阐述了关于离子交换膜、双极膜、两性膜以及复合膜的膜电位的最新进展,并提出今后的发展方向.     

钠型斜发沸石Na+-K+离子交换特性研究(Ⅱ)--过程传质模型及动力学特性研究

利用浅床实验法研究查明了钠型斜发沸石Na -K 离子交换过程以液膜扩散为主的控制机理,依据传质膜理论,推导出液膜控制下的离子交换传质速率模型,并测定了离子交换动力力学曲线和过程传质系数.研究结果表明:钠型斜发沸石Na -K 离子交换速率与溶液流速、温度和溶液的K 浓度成正比,与溶液粘度和沸石粒径成反比,过程总传质系数的模型计算值 与实验值拟和较好.     

荷电膜的膜电位研究进展

膜电位的测定是表征荷电膜的传递现象的重要参数之一。本文简要介绍了膜电位理论基础,包括T. M. S.理论和不可逆热力学理论。分别阐述了关于离子交换膜、双极膜、两性膜以及复合膜的膜电位的最新进展,并提出今后的发展方向。     

咪唑啉缓蚀剂膜抑制腐蚀介质扩散行为的MD研究

采用分子动力学模拟的方法,对5种1-(2-氨乙基)-2-烷基-咪唑啉缓蚀剂[(NH2)C2H4-C3H4N2-CH2(CH2)nCH3,n=5,7,9,11,13]抑制CO2腐蚀的缓蚀机理进行了研究.计算了4种腐蚀介质粒子(H2O,H3O+,Cl-和HCO-3)在不同缓蚀剂膜中的扩散系数,并从自由体积分数、腐蚀介质粒子与缓蚀剂膜的相互作用、膜的自扩散性能等方面对缓蚀剂膜抑制腐蚀介质粒子扩散行为的微观机理进行了分析.扩散系数的计算结果表明:缓蚀剂膜能有效抑制腐蚀介质的迁移,削弱其腐蚀能力;与中性H2O分子对比,缓蚀剂膜对H3O+,Cl-和HCO-3带电离子的扩散具有更强的抑制效果;随烷基链长的增加,5种缓蚀剂膜对腐蚀粒子扩散的抑制能力呈增强趋势.综合分子动力学计算结果,5种缓蚀剂缓蚀性能随着烷基链长的增加逐渐增强,理论评价结论与实验结论相吻合.     

醋酸离子液体[C2mim][OAc]水溶液的摩尔表面Gibbs自由能

在288.15-318.15 K温度范围内测定了不同浓度离子液体1-乙基-3-甲基咪唑醋酸盐([C₂mim][OAc])水溶液的表面张力和密度;在改进李以圭等人的溶液表面张力模型基础上,提出摩尔表面Gibbs自由能新概念,建立了摩尔表面Gibbs自由能随溶液浓度变化的线性经验方程,利用这个经验方程估算了[C₂mim][OAc]水溶液的摩尔表面Gibbs自由能,并进一步预测了该溶液的表面张力,其预测值与相应的表面张力实验值高度相关并非常相似。由此可见,摩尔表面Gibbs自由能与等张比容极其类似,可能成为预测离子液体及其溶液性质的一种新的半经验方法。在指定溶液浓度下,根据溶液的摩尔表面Gibbs自由能随温度呈线性变化的规律,得到了新的Eötvös方程,与传统的Eötvös方程相比,新Eötvös方程的每一个参数都有明确的物理意义:斜率的负值是摩尔表面熵,截距是摩尔表面焓,在指定浓度的溶液中摩尔表面焓几乎不随温度变化。     

Carbon Aerogel Films Synthesized at Ambient Conditions

Carbon aerogels derived from organic sol-gel process and supercritical drying are novel porous materials with interconnect structures and higher electrical conductivity, which are considered to be ideal electrode materials for supercapacitors and rechargeable batteries. The objective of the research was to synthesize carbon aerogel films at ambient conditions. Resorcinol formaldehyde (RF) and carbon aerogel films have been produced with extremely high RC ratio (molar ratio of resorcinol to catalyst) followed by subcritical drying. The structure of the porous films was investigated using electron scanning microscope. The specific surface area was measured by using nitrogen adsorption (BET) and electrical conductivity was measured with four-probe method. It was found that with extremely high RC ratio, the porous structure of RF and carbon aerogel films can be controlled from micro to macro porous at ambient conditions. With respect to the application as electrodes for fuel cells, carbon aerogel films with different porous structures on the two surfaces have been also obtained through optimizing the sol-gel process.     

Theoretical studies on electrochemistry of p-aminophenol

Geometric parameters, vibrational frequencies and thermochemical values of p-quinonimine (p-Q) and p-aminophenol (p-AP) were computed by ab initio calculation (HF) and density function theory (DFT) with the 6-31G(d,p) basis set. Cyclic voltammetry with a goldren electrode of p-AP solutions in phosphate buffers at pH 7.30 showed that standard electrode potential of half reaction for (p-Q) and (p-AP) is 0.728V. Standard electrode potential of half reaction for p-Q and p-AP were calculated using the sum of electronic and thermal free energies of p-Q and p-AP with normal hydrogen electrode (NHE) as a reference electrode. The results show that the theoretical standard electrode potential of half reaction for p-Q and p-AP is 0.682V at B3LYP/6-31G(d,p) level and 0.622V at HF/6-31G(d,p) level, respectively, indicating that computed standard electrode potential at B3LYP/6-31G(d,p) level are more reliable than that at HF/6-31G(d,p) level.     

锌铈混合金属氧化物薄膜电化学沉积的研究

采用自制四电极体系,原位测量锌铈混合氧化物薄膜电沉积过程电极/溶液界面pH的动态变化。电极/溶液界面的pH-时间曲线表明,pH快速上升后达到平衡,且电沉积过电位越大,达到平衡pH值的时间越短,平衡pH值也越高。X射线粉末衍射(XRD)实验证明薄膜沉积物是由ZnO和CeO2组成。电感耦合等离子体(ICP)技术分析了不同电沉积电位、不同电沉积时间下电沉积产物中Ce(Ⅲ)/Zn(Ⅱ)的物质的量比,结果表明Ce(Ⅲ)/Zn(Ⅱ)的物质的量比随着pH值的升高而增加。依据Zn2+离子和Ce3+离子液相和固相中存在形态的热力学数据,计算了2种金属离子的条件溶解度随pH的变化曲线。结合实验测试数据和理论计算结果,讨论了电极表面金属氧化物的电化学沉积机理,并阐明了阴极表面混合金属氧化物的组成取决于液-固两相中金属离子存在形态的热力学性质。     

Temperature dependence of the Kováts retention index. Convex or concave curves

The non-linearity in the temperature dependence of the Kováts index, I (the formation of convex or concave curves) was characterized by the second derivative, d(2)I/dT(2). The expression deduced on a purely mathematical-physicochemical basis is d(2)I/dT(2)=[2TDeltaS(CH(2))dI/dT-100deltaDeltaC(p)]/TDeltaG(CH(2)). The solute-dependent factor for dI/dT, d(2)I/dT(2), and the extreme temperature in the I vs. T relationship is deltaDeltaC(p), which is the molar solvation heat capacity difference between the solute and a hypothetical n-alkane which elutes at the same time as the given solute, while the solvent-dependent factors are the solvation entropy and free energy of the methylene unit, DeltaS(CH(2)) and DeltaG(CH(2)). Experimentally, convex Ivs.T curves with a minimum are formed when deltaDeltaC(p)>0, while concave ones with a maximum are observed when deltaDeltaC(p)<0. In the event of a linear temperature dependence, the former equation can be simplified: dI/dT=100deltaDeltaC(p)/2TDeltaS(CH(2)). The deviation from linearity (higher d(2)I/dT(2)) increases with increasing deltaDeltaC(p) values. The model equations were tested from the dataset published by the Kováts group on C78 (19,24-dioctadecyldotetracontane), POH (18,23-dioctadecyl-1-untetracontenol), PCN (1-cyano-18,23-dioctadecyluntetracontane) and TMO (1,38-dimethoxy-17,22-bis-(16-methoxyhexadecyl)-octatriacontane) and by present measurements on the Innowax phase.     

Experimental and computational studies on the molecular energetics of chlorobenzophenones

The standard (p degrees = 0.1 MPa) molar enthalpies of formation, Delta(f)H(m)degrees, of crystalline 2-, 3- and 4-chlorobenzophenone and 4,4'-dichlorobenzophenone were derived from the standard molar energies of combustion, Delta(c)U(m)degrees, in oxygen, to yield CO(2)(g), N(2)(g), and HCl x 600H(2)O(l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The Calvet high-temperature vacuum sublimation technique was used to measure the enthalpy of sublimation, Delta(cr)(g)H(m)degrees, of the compound 2-chlorobenzophenone. For the other three compounds, the standard molar enthalpies of sublimation, at T = 298.15 K were derived by the Clausius-Clapeyron equation, from the temperature dependence of the vapor pressures of these compounds, measured by the Knudsen-effusion technique. From the values of Delta(f)H(m)degrees and Delta(cr)(g)H(m)degrees, the standard molar enthalpies of formation of all the compounds, in the gaseous phase, Delta(f)H(m)degrees (g), at T = 298.15 K, were derived. These values were also calculated by using the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G(d) computational approach.     

Electrochromic and photoelectrochromic properties of sol–gel derived tungsten trioxide/titania composite thin films

Tungsten trixoide/titania (WO₃-titania) composite thin films with W/Ti molar ratios of 100/0, 98/2, 96/4, 94/6 92/8 and 90/10 were prepared on fluorine-doped tin oxide conducting glass, and their electrochromic (EC) and photoelectrochromic (PEC) performances were investigated in this study. The composite thin films were synthesized by sol–gel process using peroxotungstic acid and titanium (IV) n-butoxide as the precursors. The surface morphology and composition of the composite thin films were characterized using scanning electron microscope with energy dispersive spectrometer. Electrochemical experiments with in situ spectroscopic measurement were employed to study the EC properties of the composite thin films. It was found that the presence of titania in the WO₃ matrix might slightly decreases its EC performance. PEC cells using the composite thin films as the working electrode and a sputtered semitransparent platinum thin film on ITO as the counter electrode were fabricated and their PEC performances were investigated. The device using composite thin film prepared from sol solution with a W/Ti molar ratio of 96/4 exhibited the best PEC performance.     

普通有机分子或药物热分解稳定性的理论预测

采用密度泛函理论方法, 在B3LYP/6-31+G(d,p)水平上, 对任意选定的32个有机化合物或药物进行最低能量构象优化和结构参数理论计算. 建立了四极矩参数Q_ii与半数摩尔热分解函数Y_d(1/2)的相关方程, 其定量构性关系(QSPR)方程为Y_d(1/2)=-8.65747-3.8954Q_ii, 相关系数为r²=-0.99297, 交叉验证相关系数为XV-r²=0.99188, F检验结果为4237.343321. 训练集化合物的半数分解温度T_d(1/2)的平均绝对预测误差(AVEDEV)为14.70 K. 进一步利用该方程对测试集中43个分子进行预测验证, T_d(1/2)的预测值与实验值的相关系数为0.92304, Y_d的预测值与实验值的相关系数为0.99345, 证实了所建立方法的可靠性. 结构差异性分析表明, 训练集和测试集中的化合物均较均匀地分布在结构参数的3D空间中, 化合物结构具有较好的多样性和差异性.     

邻苯二胺的电聚合及膜氧化还原过程的研究

石英晶体微天平;循环伏安法;邻苯二胺的电聚合及膜氧化还原过程的研究     

Investigation of the effects of Au-colloid modification on cobalt hexacyanoferrate film growth and mass transport by electrochemical quartz crystal microbalance

The growth of cobalt hexacyanoferrate (CoHCF) films on bare and Au-colloid-modified electrodes in nitrate or sulfate solutions was monitored by electrochemical quartz crystal microbalance. The average efficiency of CoHCF film growth for Au colloid modified electrodes is 23 and 12 ng cm(-2) s(-1) in KNO3 and K2SO4 solutions, respectively, while those values for the bare gold electrode are 15 and 9 ng cm(-2) s(-1), respectively. In K2SO4 solution, the apparent molar masses for the Au-colloid-modified electrode at lower and higher potential is 58.4 and 37.3 g mol(-1), respectively, which is larger than those for the bare gold electrode (51.7 and 26.3 g mol(-1), respectively). The respective results were also obtained in KNO3 solution. Furthermore, the difference of the apparent molar masses at lower and higher potential for Au-colloid-modified electrodes is smaller than that for bare gold electrodes in the same electrolyte. Additionally, the mechanism of charge propagation is dependent on different anions in electrolyte solutions at higher potentials where the second redox reaction of CoHCF occurs. Therefore, the existence of Au colloids can accelerate CoHCF film growth and weaken the effect of anions on mass transport.