Al-Zn-Mg-Cu合金组织和电导率及抗应力腐蚀性能研究

研究了三种Al-Zn-Mg-Cu合金在回归再时效状态下的组织、电导率与抗应力腐蚀性能的关系.结果表明,电导率≥35.46%IACS的合金均表现出良好的抗应力腐蚀性能与较高的拉伸强度,晶界组织为粗大分立的η相,晶内为均匀弥散的GP区和η'相;而电导率≤34.63%IACS的合金虽然拉伸强度较高,但抗应力腐蚀性能较低,晶界组织为尺寸较小的链状η相.分析表明,相对常规T73等过时效状态的高电导率(38%～42%IACS),回归再时效状态弥散的晶内组织导致了较低的电导率和高抗拉强度,但粗大分立的晶界析出相仍然使其获得了优良的抗应力腐蚀性能,从而使合金表现出电导率适中(35.46%～36.82%IACS)、抗应力腐蚀性能良好和拉伸强度高的特点.     

Pressure dependence of electrical conductivity in polypyrrole

The electrical conductivity as a function of pressure to about 1.1 GPa is determined for p-toluenesulphonate-doped polypyrrole at two different doping levels and also for tetrafluoroborate-doped polypyrrole. A second-order polynomial is found to fit the observed data better than either of the existing models. The polynomial is of the form σ(P) = − aP² + bP+ σ(0).     

Synthesis of polyanilines with high electrical conductivity

A procedure for the chemical synthesis of conductive polyanilines is presented. The effect of the relative concentration of reactants on the material properties is studied. The synthesis is realized with hydrochloric or phosphoric acids. It is shown that it is possible to perform the oxidative polymerization condensation at temperatures up to 99 °C and that its control can give rise to polyanilines with high conductivity. The optimum temperature depends on the acid used and is, for the cases considered, higher than the one used in the procedures reported so far. In particular, pellets of polyanilines synthesized with H₃PO₄ are produced with conductivities up to 58 S/cm.     

Measurement of electrical conductivity of micron-scale metallic wires

Electrical conductivltles of micron-scale aluminum wires were quantitatively measured by a four-point atomic force microscope （AFM） probe. This technique is a combination of the principles of the four-point probe method and standard AFM. This technique was applied to the 99.999% aluminum wires with 350 nm thickness and different widths of 5.0, 25.0 and 50.0 μm. Since the small dimensions of the wires, the geometrical effects were discussed in details. Experiment results show that the four-point AFM probe is mechanically flexible and robust. The four-point AFM probe technique is capable of measuring surface topography together with local electrical conductivity simultaneously. The repeatable measurements indicate that this technique could be used for fast in-situ electrical properties characterization of sensors and microelectromechanical system devices.     

EPR and electrical conductivity in microporous polyaniline

We have studied a series of microporous polyaniline (PANI) samples, each of the structure with micro-channels and micro-caves inside (a diameter of 1.5–2.5 μm), formed as a non-periodic network of microrods. Microporous polyaniline is a paramagnetic material and strong EPR signals with the g-factor in the range of 2.0030–2.0032 and the line width ΔB between 1.80 and 6.50 Gs have been measured for samples of various electrical conductivity. The EPR line asymmetry is high (almost 1.5) in the case of PANI samples of the highest electrical conductivity (0.35 S/cm).We found that lithium cations present in the reaction medium can stabilise values of the EPR line asymmetry parameter and g-factor observed for PANI samples prepared in such conditions. Lithium cations are able to influence the intermolecular hydrogen bonding which is essential for the interchain coupling leading to an increase in the EPR line asymmetry and a higher electrical conductivity. Thus, the properties of PANI samples are modified by lithium cations.     

碳纳米管-银复合材料的制备工艺和电导率

采用粉末冶金方法制备碳纳米管-银复合材料,研究了制备工艺、碳纳米管含量对碳纳米管-银基复合材料密度、硬度、抗弯强度、电导率的影响.结果表明:采用复压烧结,烧结温度为700℃时,复合材料的性能较好;碳纳米管和银的弱界面结合,使得碳纳米管对复合材料的强化效果不明显;当碳纳米管的体积含量大于10%时,碳纳米管在晶界上发生偏聚,碳纳米管-银界面对电子产生散射,导致复合材料的电阻率迅速增加.     

铝合金的力学性能及其电导率

评述了影响铝合金力学性能和电导率的主要因素，说明铝合金的力学性能与其电导率有一定的关联。介绍了电导率在铝合金热处理工艺制定和力学性能检测中的应用，指出借助于电导率的测定，可以初步推测铝合金的某些力学性能和初步优化铝合金的某些热处理工参数，达到测试快速、无损和简便的目的。     

Study on SCR De NOx mechanism through in situ electrical conductivity measurements on V2O5-WO3/TiO2 catalysts

V2O5-WO3/TiO2 catalysts were prepared by impregnation method and in situ electrical conductivity measurements were carried out to investigate the reaction mechanism for ammonia SCR (selective catalytic reduction) of NOx.The electrical conductivity change with ammonia supply and the increase of electrical conductivity were mainly caused by reduction of the labile surface oxygen.The electrical conductivity change of catalysts shows close relationship with the conversion rate of NOx.Variation of conversion rate in atmosphere without gaseous oxygen also supports that the labile lattice oxygen is indispensable in the initial stage of the de NOx reaction.These results suggest that the liable lattice oxygen acts decisive role in the de NOx mechanism.They also support that De NOx reaction occurs through the Eley-Rideal type mechanism.The amount of labile oxygen can be estimated from the measurement of electrical conductivity change for catalysts with ammonia supply.     

The electrical conductivity of NiO at 1000°C

Specimens of NiO for conductivity measurements were made from Ni foil, containing less than 25ppm total impurities, by spot welding platinum leads to the foil which was then oxidized to compact NiO at 1300°C. Four point d.c. conductivity measurements were carried out at oxygen partial pressures between 1 atm and 10^?10 atm provided by gas mixtures and monitored using a zirconia-based solid state cell sensitive to oxygen. The results indicate a predominance of doubly charged cation vacancies below 10^?5 atm oxygen partial pressure and of singly charged cation vacancies above this value.     

High-temperature electrical conductivity of Li–Ge ferrites

Electrical conductivity of germanium-substituted lithium ferrites of different compositions have been investigated as a function of composition and temperature. Plots of log(σT) versus 10³/T are almost linear and have shown a transition near the Curie temperature. The activation energy in the ferromagnetic region is in general less than that in the paramagnetic region. An attempt is made to explain the conduction mechanism in Li–Ge ferrites.     

Structure and electrical conductivity of TCNQ-2,3,7,8-tetramethoxychalcogenanthrene complexes

Charge-transfer complexes formed by reaction of 2,3,7,8-tetramethoxychalcogenanthrenes(5,10-dichalcogenacyclo-diveratrylenes, ‘Vn₂E₂’) with 7,7,8,8-tetracyanoquinodimethane (TCNQ) are prepared and their structures determined. Spin concentration, mobilities and gap energies of the polycrystalline samples are evaluated from e.s.r. intensities and electrical conductivity measurements. The influence of the different chalcogen atoms on physical properties is discussed.     

Correlation between vibrational spectra and electrical conductivity of polythiophene

Polythiophene films synthesized by electrochemical polymerization under various conditions were undoped and redoped maximally with iodine. The electrical conductivity of the redoped films was in the range 2 × 10² − 5.9 S cm⁻¹. Vibrational spectra of the undoped films were analysed on the basis of those of model compounds including 2,2′-bithiophene, 2,2′:5′,2″-terthiophene and 2,2′:5′,2″:5″,2′-quaterthiophene. First, the intensity ratio of the infrared CH out-of-plane bending bands at 697 (2-substituted thiophene) and 787 cm⁻¹ (2,5-substituted thiophene) is a clue to the degree of polymerization. Secondly, the intensity ratio of the infrared double-bond symmetric and antisymmetric stretching bands reflects the distribution in length of the conjugated segment. Finally, the intensities of three Raman bands at 1155, 682 and 652 cm⁻¹ give information about the amount of distorted structure around the inter-ring C-C bonds. From the comparison of the spectroscopic and conductivity data, it is concluded that a high degree of polymerization alone is not adequate for a doped film to have high electrical conductivity but abundance of long conjugated coplanar segments is the requisite condition.     

铝电解质熔体电导率研究进展

高电导熔盐电解质体系的开发是实现铝电解过程节能降耗的主要途径之一。综述了铝电解用钠冰晶石熔体电导率的研究进展,并分析了添加剂Al2O3、AlF3、LiF、CaF2以及MgF2等对熔体导电能力的影响,对不同研究者获得的研究结果进行了对比分析。同时,对钾冰晶石的电导率研究也进行了概述,指出为开发高电导的电解质体系,应深入研究熔体导电率及其影响因素。     

高温熔盐电导率测试方法

熔盐电解质的导电性对熔盐电解的能耗有极大的影响,直接关系到熔盐电解生产的能耗和成本。介绍了四电极法、连续改变电导池、交流电桥法和交流阻抗法测量高温熔盐电导率的基本原理、优点和存在的问题,为高温熔盐电导率测量方法的选择提供了参考。     

Kinetics interpretation of NiO electrical conductivity under low oxygen pressures

In a previous work it has been stated that the NiO electrical conductivity changes connected to the oxygen pressure changes may be considered as a transitory phenomenon. A mixed kinetics case controlled by the formation of surface cation vacancies and their diffusion in the bulk is proposed to explain the reaction process. By means of an equivalent electrical circuit in good agreement with the kinetics model it was possible to reproduce the experimental phenomenon.     

轨道电路合金导线的硬度及导电性能

以单一添加稀土元素Ce、Y和复合添加Ce+Y的Cu-Cr-Zr合金轨道电路导线为研究对象,研究了合金化元素和热处理工艺对Cu-Cr-Zr合金导线的硬度和电导率的影响,并分析了合金导线的抗高温软化性能。结果表明,添加稀土元素Ce、Y的合金导线时效后的硬度提高了14~20 HV0.1,而电导率降低了2%~4%IACS;相同时效时间下合金导线硬度从高至低的顺序为Cu-Cr-Zr-Ce > Cu-Cr-Zr-Y > Cu-Cr-Zr,电导率从高至低的顺序为Cu-Cr-Zr > Cu-Cr-Zr-Ce > Cu-Cr-Zr-Y;复合添加Ce+Y合金导线的软化温度提高了约30 ℃,Cu-Cr-Zr-Ce-Y合金中的时效析出相主要是CrCu2(Zr, Mg)相。     

熔盐电解法制备金属钛的氧空位导电机制和阴极结构的研究

熔盐电解法制备金属钛是取代高污染,高能耗的传统金属钛冶炼方法的重要工艺。但是,熔盐电解法所需时间长,效率低,是阻碍该法发展的瓶颈问题。因此,本文以提升脱氧速度为目标,首先研究了试片厚度对反应速度的影响,再配合采用量子化学方法,研究了TiO₂的导电机制。基于实验和计算结果,设计了多层阴极。多层TiO₂阴极经6 h的电解后,得到了含氧量在3 500-4 000 ppm的金属钛,且各片产物没有明显差别。相比传统的阴极制备方法,电解速度得到有效提高。并且多层阴极解决了电解速度与产量的矛盾,为熔盐电解法的工业应用提供了有益的参考。     

7A04-T73铝合金锻件电导率与力学性能稳定性的研究

针对7A04-T73铝合金锻件生产中出现的电导率与力学性能不匹配问题,通过对该合金锻件锻压工艺及热处理工艺的试验研究,确定了影响电导率与力学性能的因素。结果表明,7A04铝合金锻件的最佳锻造温度为400℃～420℃,淬火温度为469℃～475℃,双级时效制度为(115±5)℃8 h+(180±5)℃12 h。