镀怪中基体金属扩散系数的测定

铜在防渗铜镀层中的扩散系统是评价镀层防渗铜能力的重要参数。采用了电子显微探针法,“俣野”数值方法推导出扩散系数,并分析了铜在柱状和块状镍镀层中的扩散系数。     

气相扩散系数的简易测定

1引言菲克定律中的扩散系数DAB代表单位浓度梯度下的扩散通量，表证某个组分A在介质B中扩散的快慢，是物质的一种传递属性，类似于传热中的导热系数。但比导热系数更为复杂：它至少要涉及两种物质，因而有多种多样的组合方式；同时随温度的变化较大，还与气体的总压有关。故文献中扩散系数的数据难以齐全。而应用半经验公式估算时，精确度又欠佳[1]．本文介绍一种简易方法，用以测定两组分混合气体的扩散系数。对其测定原理进行严谨而完整的分析论证，并通过实例说明其应用。2测定原理如图1所示，在一细长直立的玻璃管底都盛入纯液体入不…     

对二甲苯在醋酸中扩散系数的测定

为了提供精对苯二甲酸（PTA）生产过程中相关体系的扩散系数,利用金属膜池并用氯化钾水溶液标定了膜池常数。用已有文献值的乙酸水溶液验证了装置的可靠性。测定了298.15-323.15K不同温度下对二甲苯在醋酸中的积分扩散系数,还分别给出了微分扩散系数与对二甲苯浓度的关联式。结果表明在相同温度下对二甲苯在醋酸中的扩散系数随着对二甲苯浓度的增加而减小,在同一浓度下随着温度的升高而增加。     

邻二甲苯在醋酸中扩散系数的测定

利用金属膜池并用氯化钾水溶液标定了膜池常数。用已有可靠文献值的乙酸水溶液验证了装置的可靠性。测定了298．15～323．15K不同温度下邻二甲苯在醋酸中的积分扩散系数,还分别给出了微分扩散系数与邻二甲苯浓度的关联式。结果表明在相同温度下邻二甲苯在醋酸中的扩散系数随着邻二甲苯浓度的增加而减小,在同一浓度下随着温度的升高而增加。     

聚合物体系中小分子物质扩散系数的测定

简述了用本体平衡法，逆流气相色谱法，自旋回声脉冲梯度场的核磁共振法和激光全息干涉技术测定聚合物体系中小分子物质的扩散系数。     

青霉素钾在水溶液中扩散系数的测定

用金属膜池法测定了２９８Ｋ条件下青霉素钾在水溶液中的积分扩散系数,给出了微分扩散系数与浓度的关联式。     

L-抗坏血酸在水溶液中扩散系数的测定

用金属膜池法测定了２９８．１５Ｋ的抗坏血酸在水溶液中可溶解范围内积分扩散系数,该金属膜池法用已知扩散系数的乙酸＋水物系进行校验,证明了本方法及装置的可靠性。此外,还分别给出了它们的微分扩散系数与浓度的关联式,关联式误差较小     

电解质通过离子交换膜的扩散系数测定

本文叙述了电导法测定电解质通过离子交换膜扩散系数的原理、方法,并推导出计算公式。均相离子交换膜的盐扩散系数小于异相膜,含水量少的膜小于含水量多的膜,阴膜小于阳膜。二价金属离子的盐在阴膜中的扩散系数小于一价金属离子的盐。对两种电解质分别测得它们在膜中的扩散系数后,即可算出其分离系数S_A~B 值。     

气相色谱法测定分子筛扩散系数

气相色谱法测定分子筛扩散系数是根据色谱VanDeemeter过程，将被测分子筛装人色谱柱中，以测得的色谱往理论板高度（H）和相应的线速度（u）作图，求得在高线速度部分的斜率（C），计算分子筛的扩散系数（Dp）。本文测定了8种5A型和4种13X型分子筛对氧和氛的扩散系数，证明用不同制各方法得到的产品其扩散系数有很大的差异，故其应用的工艺条件亦不应雷同。     

气相色谱法测定分子筛扩散系数

气相色谱法测定分子筛扩散系数是根据色谱VanDeemeter过程，将被测分子筛装人色谱柱中，以测得的色谱柱理论板高度（H）和相应的线速度（μ）作图，求得在高线速度部分的斜率（c），计算分子筛的扩散系数（D_p）。本文测定了8种5A型和4种13X型分子筛对氧和氛的扩散系数，证明用不同制各方法得到的产品其扩散系数有很大的差异，故其应用的工艺条件亦不应雷同。     

Estimation of surface diffusion coefficient in liquid phase adsorption

An estimation procedure of surface diffusion coefficient, D_s, in liquid phase adsorption was proposed. The procedure is based on a restricted diffusion model, in which D_s is correlated with molecular diffusivity by considering a restriction energy due to an adsorptive interaction between adsorbates and adsorbents. In some adsorption systems, D_s of different adsorbates could be calculated with an error less than about 50% from only one datum of each adsorption equilibrium constant. Irrespective of temperature, the procedure, can be applied for the estimation of D_s even in a wide range of D_s of about 4 orders of magnitude.     

Effective diffusion coefficient of chloride in porous concrete

A simplified diffusion model is given in the present paper to represent the chloride diffusion in porous concrete. The model with appropriate effective diffusion coefficient is shown to represent equally well as the more complex diffusion/reaction model proposed by Pereira and Hegedus.⁴ However the present model has the main advantages of being amenable to an analytic solution and ease of model parameter estimation.     

Concentration-dependent molecular diffusion coefficient of gaseous ethane in liquid toluene

We report new experimental data on concentration-dependent molecular diffusion coefficient of ethane in toluene at temperatures ranging from 21 to 125°C and pressures up to 4.14 MPa. An analytical model has also been developed for estimation of the diffusion coefficient utilizing the experimental data of the interface velocity as a result of swelling and the rate of gas dissolution in the liquid phase. It is shown that the diffusion coefficient of ethane in toluene is dependent on the initial mass fraction of the gaseous component in the liquid. In addition, the effect of concentration dependency of the molecular diffusion coefficient on diffusive mass flux is quantified. The results reveal that the assumption of a constant diffusion coefficient introduces ~10–60% error in calculation of diffusional mass transfer flux. The developed methodology finds application in estimation of the concentration-dependent molecular diffusion coefficient of gases in liquids.     

纸张干燥中湿分扩散系数的估算

纸张干燥过程涉及到多孔介质的热质传递,如何确定质量扩散系数是所建立的多孔物料湿分扩散模型能否进行数值计算的关键。按Liukov公式将湿分扩散系数视为含湿质量分数的非线性函数,在恒温下进行纸张干燥实验,通过比较湿分蒸发质量的测量值与理论计算值,采用多变量寻优的方法对多孔介质一维情况下的湿分扩散系数进行估算,得到了实验条件下的纸张湿分扩散系数的计算公式。并进一步确定了纸张中的湿分扩散系数与含湿质量分数和温度之间的函数关系式。     

氨基酸扩散系数的分子动力学模拟

采用分子动力学模拟的方法模拟了298. 15 K正则系综下甘氨酸、丙氨酸等12种氨基酸在水中的扩散过程，扩散系数的计算采用微分-区限变分法。计算结果表明：相同浓度下按不同分子数样本计算得到的扩散系数有较大差别，且分子数越多则模拟结果越接近于实验值。5种氨基酸在水中的扩散系数与文献值相对比，误差小于7%。还用同样的方法模拟了氧气在水中的扩散过程，模拟结果与实验结果吻合也较好。实验表明采用分子模拟手段可以获得具有工业应用价值的扩散系数，从而有助于计算传质学的发展。     

Determination of the trichloroethylene diffusion coefficient in water

Trichloroethylene (TCE) is a halogenated aliphatic organic compound frequently detected as pollutant in soils and ground water. To study the fate of TCE in water and to devise effective remediation strategies, a series of advection‐diffusion (dispersion) models, where the diffusion coefficient of TCE (D_TCE) is an important parameter, have been developed. However, D_TCE in water has never been experimentally determined and only theoretical values ( cm² s^?1 at 25°C) are present in the literature. A new method based on the Taylor dispersion technique, which allows to measure D_TCE in a broad range of temperature and, in principle, in any solvent is presented. At 25°C D_TCE = cm² s^?1 and the value increases almost linearly with the temperature, while, in the limit of the experimental error, is independent from [TCE] for dilute solutions. From the temperature dependence of D_TCE, it was possible to calculate the specific TCE fitting constant in the well‐known Wilke and Chang theoretical relation and the activation energy of the diffusion process through the Arrhenius plot. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3511–3515, 2015     

脂肪酸在甲基丙烯酸异丁酯凝胶中扩散系数的估测

采用分散质分子染色、跟踪手段,对游离脂肪酸分子在甲基丙烯酸异丁酯高分子凝胶体系中有效扩散系数进行测定和估算,实验测得有效扩散系数为10-11 m2/s数量级范围,处于估测范围之内。同时对比了分散质分子在纯液相中的自由扩散系数,并分析了凝胶体系中脂肪酸分子的扩散机制。结果表明:利用染色、跟踪定量法对大分子分散介质在凝胶体系中扩散行为的研究和有效扩散系数的估测具有可行性。     

盐种类和浓度对蛋白质疏水性吸附过程有效孔扩散系数的影响

研究了牛血清白蛋白在配基密度不同的两种疏水性吸附剂Phenyl Sepharose FF low sub和Phenyl Sepharose FF high sub上的吸附平衡和孔内传质动力学,重点考察了盐种类和浓度的影响.结果表明,Na2SO4溶液中盐浓度的增加导致蛋白质吸附容量的增大和解离常数的降低比(NH4)2SO4溶液更显著.利用孔扩散模型得到的有效扩散系数随盐浓度及配基密度的增大而提高,表明表面扩散作用对孔内传质的贡献随吸附容量提高而增大.     

Cation diffusion at the polymer coating/metal interface

Theoretical and experimental studies were carried out on the transport of cations in the channel between a polymer coating and a metal substrate from a defect in the absence of an applied electrical potential. The model consists of two stages: an initial period during which ions diffuse in the coating/metal interfacial 'channel' and adsorb on the coating surface, and a propagation period during which ions also diffuse into the coating. The mathematical models were solved to predict the cation concentration and flux under the coating and the relative rate of diffusion between the initial and propagation periods. Model parameter values were derived from the results of an experiment conducted in a specially designed diffusion cell. The experiment measured the depletion of Na⁺ ions in a cylindrical, central reservoir, which was placed within the perimeter of a defect through the coating of an epoxy-coated steel panel. Model predictions of concentration versus time agreed well with the experimental results, which showed that most of Na⁺ ions were removed by lateral diffusion from the reservoir during the initial period. Further, the transport during the initial period was much faster than that during the propagation period. The results also indicated that during the propagation period, the rate-limiting step was the lateral diffusion along the coating/metal interface rather than diffusion through the coating.     

离子液体中的相互作用对硝基苯扩散系数的影响

应用紫外吸收光谱法和循环伏安法研究了离子液体中的相互作用及对离子液体中硝基苯的扩散系数的影响。结果表明,硝基苯的紫外光谱受离子液体EMimBF₄(1-甲基-3-乙基咪唑四氟硼酸盐)与其相互作用的影响,硝基的吸收峰红移,210 nm以下的末端吸收消失,而苯环的吸收基本不变;离子液体与硝基苯之间的作用主要发生在硝基上。在离子液体中电还原,硝基苯的扩散系数受硝基苯与离子液体、水与离子液体的相互作用的影响。同一离子液体中,随硝基苯浓度增加,扩散系数减小。相同硝基苯浓度时,不同离子液体的咪唑阳离子侧链越长扩散系数越小,但扩散系数减小得越缓慢;同一离子液体中,随着水浓度增加,硝基苯扩散系数增大;不同离子液体中,咪唑侧链越长,随着水的浓度增加,硝基苯扩散系数增加越快。