轻质油料电导率仪检定方法研究

叙述轻质油料电导率仪的检定原理及检定方法。采用高阻结合标准物质的方法解决了轻质油料电导率仪无法检定的问题。     

轻质油料电导率仪自动检定方法

研究了一种对轻质油料电导率仪进行自动检定的方法。采用模拟高阻技术和视频采集控制软件相结合,减少了人体对检定结果的影响,提高了检定效率和检定结果的可靠性。该方法对研究轻质油料电导率仪的测量参数和相关仪器的特殊测量范围的线性有很大的帮助。     

电导法研究丙烯酰胺反相微乳液聚合体系的稳定性

制备了Span80-Tween80/异辛烷/AM-H2O反相微乳液体系,用电导法考察了不同HLB(亲水-亲油平衡)值下电导率的变化规律,并研究了正丁醇(n-butanol)、氯化钠(NaCl)和醋酸钠(NaAc)的加入对微乳液体系电导率变化的影响规律.实验表明:HLB值为5.4时体系的电导率变化较小.正丁醇质量浓度为25 g/L时电导率几乎没有变化,当NaCl质量浓度为50 g/L或NaAc质量浓度为25 g/L时可以增加体系的稳定性,为检测微乳液的稳定性提供了一种有效途径.     

P2O5掺杂的磷钨酸常温电解质

以磷钨酸(PWA)为基质,加入适量的P2O5,制备了P2O5/PWA电解质. 采用交流阻抗谱方法研究了不同质量分数P2O5电解质的导电性能及相对湿度对电导率的影响. 结果表明,质量分数为7%的P2O5/PWA电解质,室温电导率达到0.045 S/cm;相对湿度在20%～70%范围内电解质的电导率变化不大;在40 ℃下长时间放置,电解质的质量损失小于2%,表明其常温保水性好.     

AOT/Triton X-100混合反胶束体系的导电性能

采用聚乙二醇辛基苯基醚(TritonX-100)和二(2-乙基己基)琥珀酸磺酸钠(AOT)双表面活性剂,与正己烷、正己醇和水构成混合反胶束体系;研究了表面活性剂质量比、助表面活性剂含量、水油体积比和温度等因素对反胶束体系导电性能的影响,同时采用循环伏安法研究了K3Fe(CN)6/K4Fe(CN)6在该体系中的电化学行为.结果表明:由两种表面活性剂构成的反胶束体系电导率σ明显大于单一表面活性剂反胶束体系电导率;体系电导率随AOT与TritonX-100的质量比w(w=mAOT∶mTritonX-100)的变化而变化,w为0-0.4时,电导率随w增大而线性增大,之后增加趋势变缓;w=0.96时,σ达到稳定值576μS·cm-1.混合体系电导率随溶水量的增大及温度的上升而提高;而增加助表面活性剂可显著降低体系的电导率.在所研究体系中,Fe(CN)36-/Fe(CN)46-电化学反应对的氧化还原峰电位几乎不随扫描速率变化,峰电位差约为75mV,峰电流的比值约为1,氧化峰电流与扫描速率的平方根成正比,说明K3Fe(CN)6/K4Fe(CN)6在混合反胶束体系中显示出良好的氧化还原可逆性,反应由扩散步骤控制.     

电场耦合法芯片电泳柱上电导检测特性研究

通过电场耦合作用对毛细管电泳柱上直流电导检测原理进行了分析, 利用带有双T结构检测池的玻璃和聚合物芯片对其特性进行了研究. 在电泳分离过程中, 电泳高电场通过检测通道耦合到出口的检测电极上并产生可被检测的电势差. 当导电性与支持电解质不同的组分谱带通过分离通道上的检测池时造成该电位差的变化, 该变化与溶液电导率、检测池长度和电场强度直接相关. 检测信号与基线相除得到的信号只和检测池中溶液的物理特征参数(电导率及电阻)有关. 用自制高阻抗信号转换系统可使芯片电泳电场强度提高到450 V/cm以上, 以1 mmol/L Tris-HCl为支持电解质, 在12 s内实现了K＋和Na＋的高重现性分离检测, 检出限达到5 μmol/L, 线性范围达两个数量级(10 μmol/L~2 mmol/L).     

氟代硼酸锂玻璃的分子动力学模拟

用分子动力学模拟方法,计算了氟代硼酸锂玻璃的电导率.研究的温度范围高于和近于玻璃转变温度,共模拟了七个体系,研究的成分大致覆盖了能形成玻璃的区域.所得极限电导率、活化能以及电导率随温度的变化与实验数据符合得相当好.以往的研究认为快离子传导的典型特征是仅有一种离子发生迁移,我们的模拟表明氟离子对电导也有较大贡献.用活化能数据可顺利解释这个三元系各体系的电导率相对高低问题.     

新型复合聚合物电解质离子导电行为的研究

PEG600和CH₂Cl₂通过Williamson缩聚反应,生成主链柔顺的PEG共聚物.¹H NMR测试表明其以[CH₂O(CH_2>CH₂O)¹³]为重复结构单元.与聚合物质量含量8%的气相SiO₂及适量的LiN(CF₃SO₂)2掺杂,制备一系列新型复合聚合物电解质.通过AC阻抗研究离子电导率,提出适合本体系的等效电路.该体系具有良好的成膜性能与热稳定性能,电导率比传统的PEO/盐体系高2～3个数量级.离子电导率随着温度的升高而增加,低温电导率增加较快,高温电导率增加较慢,呈非Arrhenius变化.在EO/Li=13～34:1(摩尔比)范围内,离子电导率随着盐浓度的变化出现两个峰值,低盐浓度的峰值较高.在303 K, EO/Li=28:1时,最大离子电导率接近10^-4 S/cm.     

用于锂离子电池的凝胶聚合物电解质的制备与性能

以丙烯腈(AN)、丙烯酸甲酯(MA)和衣康酸锂(IALi)为自由基共聚反应的主要单体, 采用溶液聚合方法, 合成轻度交联的P(AN-MA-IALi)聚合物电解质膜.通过FTIR, DSC和SEM等测试方法对共聚物的结构进行了表征, 利用交流阻抗等电化学方法对该膜的导电性能进行了研究.实验结果表明, 所制备的交联聚合物的室温电导率达到10-5~10-4 S/cm, 当IALi的质量分数为3%时, 所制备的聚合物电解质膜的电导率最大可达到1.89×10-4 S/cm.     

DMFC用质子型离子液体复合隔膜的制备及性能表征

由酸碱中和法制得质子型离子液体α-甲基吡啶三氟乙酸盐,再经相转化将质子型离子液体与PVDF-HFP复合成(PIL)/PVDF-HFP膜.交流阻抗测试表明,复合膜电导率随温度增加而递增,室温电导率:8×10-3S/cm,30℃电导率:1×10-2S/cm,80℃电导率:3×10-2S/cm.用计时电流法研究复合前后膜的甲醇渗透性能,结果显示,该离子液体复合前、后膜的阻醇性能无明显变化,但复合膜阻醇性能略优.     

Heat transfer and rheological properties of transformer oil-oxidized MWCNT nanofluid

Power transformers play a key role in power and electrical industries and thus boosting their efficiency is necessary. In this study, the effect of oxidized multi-walled carbon nanotubes on transformer oil thermophysical properties was experimentally investigated. The maximum amount of carbon nanotubes was chosen up to 0.01 mass% to assure the maximum purity of transformer oil. Heat transfer characteristics of transformer oil and nanofluids in two cases of free and forced convection were studied. Breakdown voltage, flash point, pour point, density, electrical and thermal conductivities, viscosity and shear stress, as eight important quality parameters, were determined. According to the experimental results, the Breakdown voltage decreased through concentration increasing. Electrical conductivity is not changed considerable with increasing concentration and temperature. Thermal conductivity of nanofluids and transformer oil changed with increasing temperature and concentration. Furthermore, at all concentrations and temperatures, the viscosity of the nanofluids was lower than that of transformer oil.     

Electrical properties of polyvinylcarbazole-tetracyanoquinodimethane charge transfer complexes

Electrical properties of polyvinylcarbazole-tetracyanoquinodimethane (PVK:TCNQ) charge transfer complexes were investigated as a function of the composition of the mixture, temperature, pressure and the method of sample preparation. It was shown that the electrical conductivity of the PVK:TCNQ complex (for TCNQ content <10% by weight) increased only slowly with increasing concentration of TCNQ and was only slightly higher than the conductivity of pure PVK. At higher TCNQ concentrations however an abrupt increase of the complex conductivity was observed. This effect may be attributed to the formation of semi-conductive tracks composed of uncomplexed neutral TCNQ molecules. The electrical conductivity of PVK:TCNQ complex was lower than the conductivity of TCNQ alone. The activation energy for electrical conductivity in the complex decreased with increasing TCNQ concentration from 0.99 eV for pure PVK to 0.37 eV for PVK:TCNQ (6:1) complex. The high field conductivity of the PVK:TCNQ complex could be explained by using the Poole-Frenkel model.     

Electrochemistry of capillary systems with narrow pores. VI. Convection conductivity (theoretical considerations)

Generally, the electrical convection current and the electrical convection conductivity (Smoluchowski's surface conductivity) have to be taken into account to describe transport phenomena across membranes with narrow pores although the electrical charge distribution within the pores cannot be described as a Helmholtz electrical double layer. In collodion membranes, which have a comparatively low fixed ion concentration, the contribution of the convection conductivity to the electrical conductivity of the pore fluid may be neglected. This assumption was made tacitly in the analysis of our data obtained with this type of membrane.

In this communication equations are derived which take the convection conductivity into account. They are in agreement with the phenomenological transport equations developed by Staverman on the basis of the thermodynamics of irreversible processes.

The electrical convection conductivity can be considered to be the contribution of the fixed ion concentration to the electrical conductivity. It is argued that this contribution cannot be neglected in ion exchange membranes with a high fixed ion concentration and a high mechanical permeability. Neglecting the electrical convection conductivity in such systems could lead to considerable differences between experimental conductivity data and the theoretical predictions. An electrical conductivity term for the fixed ions is proposed which can be used as a correction factor in the equations in which the contribution of the electrical convection conductivity has been neglected. Suggestions are made for the measurement of the electrical convection conductivity in systems with narrow pores and high electrical conductivity (e.g. ion exchange resins). The consequences of the electrical convection conductivity in practical applications of ion-exchange resins are discussed (acceleration of the rates of ion exchange; improvement of the separation properties by the application of a direct electrical current flow).     

Electrochemistry of capillary systems with narrow pores. VI. Convection conductivity (theoretical considerations)

Generally, the electrical convection current and the electrical convection conductivity (Smoluchowski's surface conductivity) have to be taken into account to describe transport phenomena across membranes with narrow pores although the electrical charge distribution within the pores cannot be described as a Helmholtz electrical double layer. In collodion membranes, which have a comparatively low fixed ion concentration, the contribution of the convection conductivity to the electrical conductivity of the pore fluid may be neglected. This assumption was made tacitly in the analysis of our data obtained with this type of membrane.In this communication equations are derived which take the convection conductivity into account. They are in agreement with the phenomenological transport equations developed by Staverman on the basis of the thermodynamics of irreversible processes.The electrical convection conductivity can be considered to be the contribution of the fixed ion concentration to the electrical conductivity. It is argued that this contribution cannot be neglected in ion exchange membranes with a high fixed ion concentration and a high mechanical permeability. Neglecting the electrical convection conductivity in such systems could lead to considerable differences between experimental conductivity data and the theoretical predictions. An electrical conductivity term for the fixed ions is proposed which can be used as a correction factor in the equations in which the contribution of the electrical convection conductivity has been neglected. Suggestions are made for the measurement of the electrical convection conductivity in systems with narrow pores and high electrical conductivity (e.g. ion exchange resins). The consequences of the electrical convection conductivity in practical applications of ion-exchange resins are discussed (acceleration of the rates of ion exchange; improvement of the separation properties by the application of a direct electrical current flow).     

Conductometric properties of linear polyelectrolytes in poor-solvent condition: the necklace model

We present a set of low-frequency electrical conductivity measurements of solutions of differently charged, salt-free polyelectrolytes in poor- and in good-solvent conditions, in the semidilute concentration regime. The data have been analyzed and discussed in light of the necklace model for hydrophobic polyelectrolytes recently proposed by Dobrynin et al. [Macromolecules 29, 2974 (1996)] that predicts the chains to collapse into spheroidal cores connected by narrow strings. By varying the quality of the solvent, we have measured the polyion equivalent conductance lambda(p) in an extended concentration range in the semidilute regime and have demonstrated that this parameter is influenced by the polyion chain conformation, giving further support, when the poor-solvent condition prevails, to the picture of a string of electrostatic blobs. On the contrary, in good-solvent condition, the electrical conductivity data are in reasonable good agreement with the picture of an extended chain consisting of a collection of electrostatic blobs. These electrical conductivity measurements, in light of scaling theory, furnish new experimental support for the necklace model for hydrophobic polyions in poor solvents.     

Novel conductive nanocomposites from perfluoropolyether waterborne polyurethanes and carbon nanotubes

The exceptional electrical conductivity of carbon nanotubes (CNTs) has been exploited for the preparation of conductive nanocomposites based on a large variety of insulating polymers. Among these, perfluoropolyether‐polyurethanes (PFPE‐PUs) represent a class of highly performing fluorinated materials with excellent water/oil repellency, chemical resistance, and substrate adhesion. The incorporation of highly conductive fillers to this class of highly performing materials allows them to be exploited in new technological and industrial fields where their unique properties need to be combined with the electrical conductivity or the electrostatic dissipation properties of carbon nanotubes. However, no studies have been presented so far on nanocomposites based on PFPE‐PUs and CNTs. In this work, polymer nanocomposites based on waterborne PFPE‐PUs and increasing amounts of carboxylated multiwall CNTs (COOH‐CNTs) were prepared and characterized for the first time. The effect of increasing concentration of COOH‐CNTs on the physical, mechanical, and surface properties of the nanocomposites was investigated by means of rheological measurements, dynamic mechanical analysis, thermal characterization, optical contact angle measurements, and scanning electron microscopy. In addition, electrical measurements showed that the highly insulating undoped PFPE‐PU system undergoes substantial modifications upon addition of COOH‐CNTs, leading to the formation of conductive nanocomposites with electrical conductivities as high as 1 S/cm. The results of this study demonstrate that the addition of COOH‐CNTs to PFPE‐PU systems represents a promising strategy to expand their possible use to technological applications where chemical stability, water/oil repellence and electrical conductivity are simultaneously required. Copyright © 2014 John Wiley & Sons, Ltd.     

Design of New Reaction Fields for Spherical Polypyrrole Particle Synthesis

Summary: Polypyrrole conducting polymers have been investigated widely for various applications because of their thermal and environmental stability and good electrical conductivity. Using chemical oxidative polymerization for the synthesis of polypyrrole particles, the reaction rate is very fast. In this study, we designed two new reaction fields for the synthesis of spherical polypyrrole nanoparticles. In the first system, oxidative polymerization of monomer droplets infused in a water/oil (W/O) emulsion reaction field was investigated. The second system employed dispersed monomer in an aqueous solution with a low concentration of oxidant in which polymerization was augmented by ultrasonic irradiation. Effective control of the reaction rate was important for enabling the synthesis of fine spherical polypyrrole particles.     

Electrical Properties Investigation in PA12/PANI Composites

Summary: Volume conducting PA-12 based composites powders were chemically prepared by in situ polymerization and aniline doping at room temperature. These kinds of polyamide / PANI composites were investigated regarding their electrical properties. Their ac and dc electrical properties measured in the frequency range of 10⁻²–10⁷ Hz are reported and the frequency dependence of electrical conductivity was investigated as a function of PANI concentration leading to the determination of the conductivity. The experimental conductivity was found to increase continuously with PANI content and explained by percolation theory with a relatively low percolation threshold of about 0.4 wt.%. The dielectric behavior of various PANI polymer composites has been characterized by the critical frequency ω_c (denoting the crossover from the dc plateau of the conductivity to its frequency dependent ac behaviour). Modelling the conductivity behavior versus volume fraction using Slupkowski approach has revealed that the considered parameters are not sufficient to describe the electrical conductivity behavior.     

Electrical conductivity of systems based on Na3AlF6-SiO2 melt

The electrical conductivity of molten binary and ternary mixtures based on the NaF-AlF₃-SiO₂ system was investigated by means of a tube-cell (composed of pyrolytic boron nitride) with stationary electrodes. An impedance/gain-phase analyser (National Instruments; a high-performance modular chassis controlled by Labview? software) was used for the cell impedance measurement. The conductivity was found to vary linearly with temperature in all the mixtures investigated. The concentration dependence of electrical conductivity (isotherms) thus obtained was divided into two parts. The first represents the concentration region of up to 10 mole % of SiO₂, the second the region with a higher concentration of SiO₂ (from 10 mole % to 40 mole %). While the conductivity decreased considerably with the concentration of SiO₂ in the second part, it increased surprisingly in the low concentration range. From these results, the influence of electrolyte composition and temperature on the electrical conductivity was examined.     

Correlation between wetting properties and electrical performance of solution processed PEDOT:PSS/CNT nano-composite thin films

Nano-composite thin films of poly(3,4-ethylenedioxythiophene) poly(styrene-sulfonate) (PEDOT:PSS) with different loading concentrations of multi-walled carbon nanotubes (MWCNT) were deposited on glass substrates using inkjet printing and spin coating techniques. The surface energy of the substrate was modified using an oxygen plasma to achieve different degrees of wetting by the composite solution. We show that the electrical properties strongly depend on the wetting of the substrate and by controlling the wettability, the conductivity of the nano-composite samples can be improved. Based on polymer conductivity, the electrical conductivity of the composite film can be improved or degraded by orders of magnitude with the incorporation of the same concentration of MWCNT. Moreover, electrical measurements show strong correlation between the conductivity of the carbon nanotube network and the resulting nano-composite films. The dependence of electrical properties on the wettability and the conductivity of the composite components could explain the diversity in the electrical behaviour reported in the literature for PEDOT:PSS/MWCNT nano-composite thin films.