Comments on the effect of liquid layering on the thermal conductivity of nanofluids

This article provides critical examinations of two mathematical models that have been developed in recent years to describe the impact of nano-layering on the enhancement of the effective thermal conductivity of nanofluids. Discrepancy between the two models is found to be an artefact of an incorrect derivation used in one of the models. With correct formulation, both models predict effective thermal conductivity enhancements that are not significantly greater than those predicted by classical Maxwell theory. This study indicates that nano-layering by itself is unable to account for the effective thermal conductivity enhancements observed in nanofluids.     

十二烷基硫酸钠在粘土上的吸附等温线最大值及其位置的解释

本文有效地将十二基硫酸钠在高岭土上的吸附等温线与溶液的导电率曲线结合起来，研究了ＳＤＳ在高岭土和Ｎａ－高岭土上的吸附，发现ＳＤＳ在高岭土上的吸附等温线最大值与吸附后平衡溶液的ＣＭＣ、固液比、ＳＤＳ的沉淀损失等因素有关，圆满地解释了吸附等温线最大值及其出现的位置。     

离子交换法在净水剂制备中的应用研究

本文进行了Ａｌ２（ＳＯ４）３＋ＲＣｌ＋Ｈ２Ｏ体系的理论分析和跟踪测试，确认该体系的主要交换反应是：该交换反应促进了铝离子的水解，提高了硫酸铝的盐基度和混凝沉降速度，制得性能优于精制硫酸铝的聚硫氯化铝净化剂。     

High pressure transport behaviour of AgI-Ag2O-MoO3 glasses and the cluster model

The effect of pressure on the conductivity of fast ion conducting AgI-Ag₂O-MoO₃ glasses has been investigated down to 150 K. The observed variation of conductivities appears to support the application of cluster model to the ionic glasses. Contribution No. 258 from the Solid State and Structural Chemistry Unit.     

TCH-600氧、氮、氢分析仪在唐钢的应用

通过TCH-600氧、氮、氢分析仪在唐钢的实际应用,重点介绍了助熔剂、坩埚、样品熔解及空白和校正过程中应注意的问题,钢铁样品分析条件的选择.     

Application of the fractional factorial design in multiple W/O/W emulsions

In presented research, multiple W/O/W emulsions were developed by using experimental design method. A 24-1 fractional factorial design was performed by varying the following input parameters: primary polymeric emulsifier (PEG 30-dipolyhydroxystearate) concentration (0.8% and 2.4%), secondary polymeric emulsifier (Poloxamer 407) concentration (0.8% and 1.2%), electrolyte magnesium sulfate heptahydrate (0.08% and 0.4%) and electrolyte sodium chloride (0.08% and 0.4%). Multiple emulsions were prepared by a two-step emulsification process. Obtained emulsions were characterized with rheological measurements, conductivity and centrifugation tests. Factorial analysis revealed that the concentration of the primary emulsifier was the predominant factor influencing the phase separation, conductivity and maximal apparent viscosity. Additionally, electrolyte magnesium sulfate heptahydrate was more efficient in stabilizing these systems, compared to sodium chloride. The applied fractional factorial design method enabled determination of the optimal concentrations of the primary and secondary emulsifier, as well as the concentration of electrolytes, in order to obtain W/O/W emulsions with desired maximal apparent viscosities, low values of conductivity and without phase separation after centrifugation.     

Dielectric and conduction mechanism studies of PVA-orthophosphoric acid polymer electrolyte

Polyvinyl alcohol (PVA)-based proton conducting polymer electrolytes have been prepared by the solution cast technique. The conductivity is observed to increase from 10⁻⁹ to 10⁻⁴ S cm⁻¹ as a result of orthophosphoric acid (H₃PO₄) addition. The plot of conductivity vs temperature shows that a phase transition occurred at 343 K in the sample PVA-33 wt% H₃PO₄. The β-relaxation peak is observed at 313 K. The glass transition temperature of PVA-33 wt% H₃PO₄ is 343 K. Orthophosphoric acid seems to play a dual role, i.e., as a proton source and as a plasticizer. The ac conductivity σ _ac = Aω ^s was also calculated in the temperature range from 303 to 353 K. The conduction mechanism was inferred by plotting the graph of s vs T from which the conduction mechanism for sample PVA-17 wt% H₃PO₄ was inferred to occur by way of the overlapping large polaron tunneling (OLPT) model and the conduction mechanism for the sample PVA-33 wt% H₃PO₄ by way of the correlated barrier height (CBH) model.     

导电聚苯胺/TiO_2微/纳米球的制备及其结构表征

采用具有八面体形貌的氧化亚铜为模板,制备了聚苯胺/TiO2(PANI/TiO2)微/纳米球,TiO2纳米粒子很均匀地分散在聚苯胺中.研究了不同TiO2/苯胺(TiO2/ANI)摩尔比对PANI/TiO2复合物的结构、形貌和电学性能的影响.实验结果表明,随着TiO2/ANI摩尔比的增加,PANI/TiO2复合物的直径逐渐减小,当TiO2/ANI摩尔比为0.16时,复合物的平均直径为373nm,而当TiO2/ANI摩尔比增加到1.6时,复合物的平均直径降到80nm.PANI/TiO2复合微/纳米球的电导率随着TiO2/ANI摩尔比的增加先升高后降低,当TiO2/ANI摩尔比达到1.6时,电导率由10-4S/cm提高到100S/cm,达到最大值.产物的形貌和结构分别采用扫描电镜、透射电镜、红外吸收光谱和X-射线衍射等手段进行了表征.     

金属薄膜中的电导率计算

考虑到杂质和表面粗糙的散射,运用量子统计的格林函数方法,计算金属薄膜中的电导率．计算表明：在薄膜系统中,来自杂质和表面粗糙散射的电导率都以π／ｋＦ（ｋＦ为费米波矢值）为周期随厚度ｄ振荡．     

Conductivity exponent in three-dimensional percolation by diffusion based on molecular trajectory algorithm and blind-ant rules

Diffusion on random systems above and at their percolation threshold in three dimensions is carried out by a molecular trajectory method and a simple lattice random walk method, respectively. The classical regimes of diffusion on percolation near the threshold are observed in our simulations by both methods. Our Monte Carlo simulations by the simple lattice random walk method give the conductivity exponent μ/ν=2.32±0.02 for diffusion on the incipient infinite clusters and μ/ν=2.21±0.03 for diffusion on a percolating lattice above the threshold. However, while diffusion is performed by the molecular trajectory algorithm either on the incipient infinite clusters or on a percolating lattice above the threshold, the result is found to be μ/ν=2.26±0.02. In addition, it takes less time step for diffusion based on the molecular trajectory algorithm to reach the asymptotic limit comparing with the simple lattice random walk.