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针对氢在镀锌层中的扩散渗透性,采用电化学氢渗透技术对Fe/电镀Zn双层试样进行了研究.得到了镀锌层的厚度对镀层氢扩散系数以及氢稳态渗透通量的影响方式.研究结果表明,电镀锌层中氢扩散系数约为10-11cm2·s-1数量级,镀锌层能够阻滞氢的扩散渗透.相应地,随镀层厚度增大,试样氢稳态渗透通量和氢有效扩散系数减小 相似文献
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指出Debye-Hückel离子活度系数公式中,除了静电作用项以外还有另一项,称之为渗透项.渗透项鲜为人知,故着重讨论该项的意义和作用. 相似文献
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丝素膜上药物渗透量对溶液PH值的响应 总被引:4,自引:0,他引:4
蚕丝丝素蛋白膜是一种具有弱碱性和弱酸性的两性荷电膜。因此在丝素膜-水溶液体系中,水溶液pH值变化会影响丝素膜上溶质的渗透速度和渗透量。丝素膜的等电点pH≈4.5。丝素膜上药物渗透实验的结果表明:在pH=3.0~9.0的范围内,当溶液的pH<4.5时,丝素膜带正电,正离子苄三甲氯化铵的渗透系数下降;当溶液的pH>4.5时,丝素膜带负电,负离子酚磺酸钠的渗透系数明显下降。中性分子间苯二酚在丝素膜上的透过不受外部溶液pH值变化的影响。当溶液的pH>8或pH>4.5时,离子化的药物5-氟尿嘧啶或维生素C的渗透系数明显变小,这是因为两者分别在pH=8(pKa=8.0)和pH=4.5(pKa=4.25)以上变成带电离子。这表明离子化药物在蚕丝丝素膜上的渗透速度和渗透量对溶液pH值变化有较好的响应特性。 相似文献
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淋洗剂凝胶渗透色谱研究苯乙醇对F127胶束溶液的影响 总被引:3,自引:0,他引:3
淋洗剂凝胶渗透色谱研究苯乙醇对F127胶束溶液的影响王庆国,刘波,蔡力行,李光亚PriceC.BoothC.程F时(深圳大学应用化学系,深圳,518060)(曼彻斯特大学化学系,英国)(南京大学化学系)关键词淋洗剂凝胶渗透色谱,胶束溶液,嵌段共聚物凝... 相似文献
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制备了聚乙烯醇(PVA)/聚丙烯睛(PAN)渗透汽化复合膜,研究了交联剂用量、底膜结构、进料液组成、操作温度等因素对膜的渗透汽化性能的影响.发现PVA/PAN复合膜对水/醇混合液表现为水优先透过,进料液中乙醇浓度在60~99wt%的范围内,渗透通量Jt与温度之间符合Arrhenius关系,选择分离系数αW/E也随温度上升而增大.进料液为95wt%的乙醇/水混合液时,75℃下Jt高达300~450g/m2h,αW/E为800~1100.对异丙醇/水、异丁醇/水及甘油/水混合体系,复合膜显示出更为优秀的透过、分离性能.就膜的化学、物理结构与其渗透汽化性能间的关系进行了讨论. 相似文献
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研究了聚1-三甲基硅基丙炔膜渗透汽化分离乙醇-水溶液传质的主要特点。发现膜对乙醇优先吸附、溶解,对水优先扩散。但因吸附液中水含量很低,总的结果表现为优先透醇。在313K,膜厚20~25μm,料液浓度10wt%时,α=18.5,J=0.969kg·m-2·h-1。透过膜的渗透液及其中的水和乙醇渗透汽化表观活化能分别为28.87、31.30和27.66kJ/mol,并随料液浓度下降而增加。对实验数据进行非线性回归,建立了该膜传递乙醇的经验关联式:Je=-5.564C2E0+13.34CE0-0.1573(kg·m-2·h-1),计算值与实验值相吻合。 相似文献
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松香改性苯乙烯聚合物分子量及分子量分布的GPC测定 总被引:1,自引:0,他引:1
本文利用凝胶渗透色谱测定新型高分子材料(苯乙烯-歧化松香树脂乙烯酯)的分子量及分子量分布,实验数据重视性较好。标准偏差为0.074,变异系数为3.360%。 相似文献
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水溶性凝胶渗透色谱测定芸芝多糖各组分的分子量及相对含量 总被引:2,自引:0,他引:2
用水溶性凝胶渗透色谱法研究了芸芝多糖在水溶性凝胶柱上的吸附影响因素,建立了最佳分离、测试条件,成功地将芸芝多糖的混合物分离为三个组分,并测试各组分的分子量分别为1190000;796000;552000。各组分相对百分含量分别为83.6%,8.9%,7.5%。 相似文献
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Grand canonical ensemble Monte Carlo simulation (GCMC) combined with the histogram reweighting technique was used to study the thermodynamic equilibrium of a homopolymer solution between a bulk and a slit pore. GCMC gives the partition coefficients that agree with those from canonical ensemble Monte Carlo simulations in a twin box, and it also gives results that are not accessible through the regular canonical ensemble simulation such as the osmotic pressure of the solution. In a bulk polymer solution, the calculated osmotic pressure agrees very well with the scaling theory predictions both for the athermal polymer solution and the theta solution. However, one cannot obtain the osmotic pressure of the confined solution in the same way since the osmotic pressure of the confined solution is anisotropic. The chemical potentials in GCMC simulations were found to differ by a translational term from the chemical potentials obtained from canonical ensemble Monte Carlo simulations with the chain insertion method. This confirms the equilibrium condition of a polymer solution partition between the bulk and a slit pore: the chemical potentials of the polymer chain including the translational term are equal at equilibrium. The histogram reweighting method enables us to obtain the partition coefficients in the whole range of concentrations based on a limited set of simulations. Those predicted bulk-pore partition coefficient data enable us to perform further theoretical analysis. Scaling predictions of the partition coefficient at different regimes were given and were confirmed by the simulation data. 相似文献
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A theory is set up of spherical proteins interacting by screened electrostatics and constant adhesion, in which the effective adhesion parameter is optimized by a variational principle for the free energy. An analytical approach to the second virial coefficient is first outlined by balancing the repulsive electrostatics against part of the bare adhesion. A theory similar in spirit is developed at nonzero concentrations by assuming an appropriate Baxter model as the reference state. The first-order term in a functional expansion of the free energy is set equal to zero which determines the effective adhesion as a function of salt and protein concentrations. The resulting theory is shown to have fairly good predictive power for the ionic-strength dependence of both the second virial coefficient and the osmotic pressure or compressibility of lysozyme up to about 0.2 volume fraction. 相似文献
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The osmotic coefficients of acetamide, propionamide and butyramide in water were measured at 293.15, 298.15 and 308.15 K using
the isopiestic method. The activity coefficients were calculated for the aliphatic amides and the pairwise free energy coefficients
for solute-solute interactions were determined according to the McMillan-Mayer theory. The osmotic and activity coefficients
of amides are discussed in terms of solute-solute interactions. 相似文献
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The osmotic pressures of solutions of magnesium and calcium polystyrenesulphonate in water and in 25 wt % mixture of dioxane in water have been measured for concentrations from 0?002 to 0?06 molal in monomer units. The osmotic coefficient derived from these measurements is almost independent of concentration. Its values for solutions in dioxane-water mixtures are much lower than for aqueous solutions. The osmotic coefficients of solutions containing mixtures of polystyrenesulphonic acid and its calcium salt in 25 wt % dioxane have also been determined. The osmotic coefficient of these solutions has a distinct maximum at a certain value of the equivalent fraction of the acid. The experimental results are compared with the predictions of the cylindrical cell model and infinite line charge model. Satisfactory agreement between theory and experiment is found. 相似文献
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The osmotic compressibility of chemically crosslinked poly(vinyl acetate) (PVAc) gels in equilibrium with pure diluent has been determined by the method of decreasing equilibrium swelling in different swelling agents. The concentration dependence of the osmotic compressibility has been found to follow a scaling law with an exponent which was greater than that predicted by the mean-field theory. A comparison has been made between the elastic moduli determined by unidirectional deformation measurements and the compressional moduli obtained from the osmotic compressibility data. 相似文献
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To investigate the osmotic pressure of non-ionic and ionic surfactant solutions in the micellar and microemulsion regions, a potential of mean force including hard-core repulsion, van der Waals attraction and electric double layer repulsion is proposed to describe the interactions between micelles and between microemulsions. Both van der Waals attraction and electric double layer repulsion are represented using Yukawa tails. The explicit analytical expression of osmotic pressure derived from the first-order mean spherical approximation is implemented by accounting for the Donnan membrane effect. The proposed theory has been applied to micelle solutions of the non-ionic surfactant, n-dodecyl hexaoxyethylene monoether, the cationic surfactant, cetylpyridinium chloride, the anionic surfactant, sodium dodecyl sulfate, and spherical oil-in-water microemulsion system. Successful comparison is made between the proposed theory and the experimental osmotic pressure data for the studied surfactant solutions. Theoretical results show that the long-range electric double layer repulsion dramatically influences the osmotic pressure of both cationic and anionic surfactant solutions in the micellar region. The regressed model parameters such as effective micelle diameter, the mean aggregation number and effective micellar charge are in good agreement with those from static light scattering studies in the literature. 相似文献
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This article presents reaction rate data for the simple hydrolysis of acetic anhydride in the acetonitrile/water and acetone/water cosolvent systems and regression analyses using recently developed thermodynamic rate equations that contain electrostatic and solvent-solute terms. The isomole fraction plots for these reaction systems are linear, and previous theoretical work has shown that the electrostatic term is negligible for such systems. On the other hand, the reaction rates are dependent upon the cosolvent mole fraction, indicating that the solvent-solute term, which is modeled empirically, is significant. The results of the analyses provide the foundation for a paradigm shift away from the emphasis on electrostatic effects to more tenable explanations of kinetic behavior in solvent systems. 相似文献
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The osmotic pressure of dense solutions of DNA fragments in aqueous 0.2-2 M salt (NaCl, etc.) solutions were easily obtained from equilibrium ultracentrifugation data. Short, helical double stranded DNA fragment solutions showed a well defined ordering transition. The osmotic pressure of these helical solutions could be explained by the scaled particle theory of rigid sphero-cylinders. On the other hand, dense solutions of (single stranded) etheno-DNA derivatives (of about 100 nucleotides) showed no ordering phase transition. The osmotic pressure as a function of the ε-DNA concentration verifies a scaling prediction for random coils in the semi-dilute regime. Good fits to the reduced osmotic pressure are obtained by using the Kleintjens and Koningsveld modified mean field lattice gas equations of state. As inferred from the Zimm clustering function, essentially all intermolecular interactions at high ionic strength are purely repulsive. 相似文献
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A simple and analytical pair potential function was developed to represent the osmotic pressures in aqueous protein/salt systems under various conditions. Based on a hard core Lennard-Jones (HCLJ) potential model, the new potential function considers various interactions by extending the attractive Lennard-Jones potential. A temperature-dependent coefficient term was introduced to take into account the specific properties of given materials. Comparison of the new potential function with the HCLJ model in hydrocarbon and water systems showed that consideration of the temperature dependence in the potential function was effective, especially for strong polar systems such as water. To predict the osmotic pressures of aqueous lysozyme/(NH(4))(2)SO(4) solutions of various ionic strength and pH, the energy parameters of lysozyme were correlated with the experimental cloud point temperature. The proposed model agreed fairly well with the experimental osmotic pressure data with only previously obtained parameters. 相似文献
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Mou-Shan Chen 《Journal of solution chemistry》1979,8(2):165-173
The hydrodynamic and osmotic terms in the relaxation field are computed up to order linear in concentration for a dilute solution
of mixed strong electrolytes using the primitive model. The computation is based on the relative function μji computed in part earlier for the purely electrostatic interaction and in part in this work for the hydrodynamic interaction
assuming the adequacy of the Fuoss velocity field. The results are compared with the earlier computations of Fuoss and Onsager,
Murphy and Cohen, and Falkenhagen, Ebeling, and Kraeft. It is found that some terms of the new results are in agreement with
the earlier computations and the other terms represent an improved computation. 相似文献