炭黑填充高密度聚乙烯开关材料

炭黑填充高密度聚乙烯复合导导材料具有良好的开关效应，其电阻随温度及电压在某一范围内变化时会发生急剧性变化。本文简述了炭黑填充高密度聚乙烯复合体系的导电机理，电阻－温度关系，电流－电压特性，以及交联对其电阻率ρ－温度Ｔ曲线的影响和如何得到良好的ＰＴＣ强度。     

导电SBS／SBR复合材料的研究

本文研究了碳黑填充充ＳＢＳ／ＳＢＲ复合材料的基本电性能，对复合材料电阻率随温度的变化特性进行了详细研究，讨论了碳黑种类，结构和性质，填充浓度以及ＳＢＳ含量对复合材料电阻率和电阻－温度特性的影响，实验结果指出，碳黑（Ｎ５５０）／ＳＢＳ／ＳＢＲ（ＳＢＳ：ＳＢＲ＝１：１ｗｔ）复合材料的电阻率随温度的变化呈一定温度的正温度系数（ＰＴＣ）效应。     

用X－Y记录仪测量微电阻

采用Ｘ－Ｙ记录仪、恒流源等仪器，利用电流通过电阻产生电压降的原理，测量固体物质电阻，与目前常采用的外用电桥或电位差计的测量方法相比，测量方法简单、可靠、重复性好。     

稀土掺杂锰氧化物的电致电阻效应

用固相烧结法制备Nd0.67Sr0.33MnOy（y=2.85）多晶样品。样品输运性质表现出自旋相关电致电阻特征。对含量低于化学计量y=3.0样品，当温度高于某一特征温度时，电阻变化符合线性欧姆定律；但低于这一特征温度时，电阻大小与负载电流或电压有关，I-V曲线偏离线性规律；在绝缘体．导体相转变点附近，样品电阻随负载电流或电压增大而迅速减小，表现出巨大电致电阻效应。这种自旋相关的电致电阻行为与氧含量和界面有很大关系。     

微孔电极中微孔参数对电声特性的影响

为研究等离子体震源的电声特性随孔特性的变化，采用微孔电极放电，通过电压和电流探头测量负载电特性，阴影成像法和高速相机记录气泡脉动特征，水听器测量声脉冲，主要研究了不同微孔间距和数目下的电特性、气泡脉动和声特性。结果表明，随着微孔间距的增加，负载电压和能量不变，而负载电流和功率却在增加。另外，声脉冲幅值随着间距的增加出现了先上升再下降的趋势，最大可达到148.8 kPa；当孔数增加时，负载的峰值电压和电流虽然减少，但气泡声脉冲数增加，致使直达波的峰值增大。因此，增加孔数对提高微孔电极放电声脉冲的峰值是有利的。     

旋涂法制备碳纳米管发电薄膜

采用多次旋涂法在玻璃衬底表面涂覆单壁碳纳米管（SWNT）悬浊液,形成均匀的SWNT薄膜,测量碳纳米管的发电特性,利用扫描电子显微镜（SEM）观测SWNT的分布情况,并用四探针电阻仪测量薄膜不同区域的方块电阻和薄膜的电流-电压（1-V）特性,结果表明,薄膜的I-V曲线线性度和重复度很高。不同浓度的氯化钠（NaCl）溶液以不同的流速流过SWNT薄膜表面,研究薄膜两端感应电势和电路中的电流变化情况。通过分析该变化情况,对SWNT发电机理作进一步阐释。     

基于测录波形的铁芯设备励磁特性转换方法探讨

为获得铁芯设备伏安特性向励磁特性的简便转换方法,该文从励磁特性定义出发,给出基于电流有效值、电压平均值的处理方法和基于电流峰值、电压平均值的处理方法,并针对其处理方法在铁芯饱和下的适用性、电流有效值法带来的误差进行分析。结果表明:随铁芯饱和程度加深,电流谐波含量增加,电流有效值法造成的误差增大。利用对放电线圈放电过程的仿真计算与试验测量,并对比不同方法所测励磁曲线用于计算结果,结果表明利用电流峰值法所得励磁特性比电流有效值法结果更适用于铁芯设备电磁暂态的计算分析。     

容性耦合射频（CCRF）放电等离子体特性实验研究

利用自行研制的传感器和测量装置，通过对放射频放电电压电流以及其相位角的测定，算出放电算的总阻抗，结合放电管的等效电路，对容性耦合射频（CCRF）激励激光放电特性进行研究，得出容性耦合射频激励激光器等离子体的伏安特性的曲线，以及等离子体电阻，容抗与气体压器，放电电流之间的实验曲线，在Godyak射频放电模型的基础上得出等离子体的电子密度，并同内置铜电极射频激励铜离子激光器阻抗特性进行了比较。     

导电SBS/SBR复合材料的研究

本文研究了碳黑填充ＳＢＳ／ＳＢＲ复合材料的基本电性能，对复合材料电阻率随温度的变化特性进行了详细研究。讨论了碳黑种类、结构和性质、填充浓度以及ＳＢＳ含量对复合材料电阻率和电阻——温度特性的影响。实验结果指出，碳黑（Ｎ５５０）／ＳＢＳ／ＳＢＲ（ＳＢＳＳＢＲ＝１１ｗｔ）复合材料的电阻率随温度的变化呈一定强度的正温度系数（ＰＴＣ）效应。     

碳纤维水泥基材料电阻的非线性研究

研究了碳纤维水泥基材料(CFRC) 非线性电阻的伏安特性,并着重讨论了不同的碳纤维掺量和温度对CFRC材料电压-电阻关系的影响.结果表明:在较小外加电压下(＜2V)CFRC材料的电压-电阻曲线会出现明显的平台区,随着电压的进一步增大,其电阻逐渐降低呈现非线性特性.相同纤维掺量的水泥基材料随温度的升高其电压-电阻曲线下降斜率基本保持不变,但初始电阻值下降;而在温度保持不变时,随碳纤维掺量的增加,电阻随电压下降的趋势逐渐减缓.     

静电纺丝中的电流电压行为

静电纺丝是一种使高聚物熔体或溶液在外加静电场作用下形成射流，制备聚合物超细纤维的有效方法。它涉及到高分子科学、应用物理学、流体力学、电工学、化学工程、材料工程和流变学等。纺丝参数如电场强度、射流所带电荷、环境湿度等都影响静电纺丝过程。以聚环氧乙烷（PEO）的静电纺丝为例，研究了静电纺丝过程中环境湿度、溶液浓度、电解质浓度和流体静压力对纺丝过程中电流和电压关系的影响。研究结果表明：环境湿度对静电纺丝的电流电压行为没有明显的影响；但是盐的加入对电流电压行为影响很大；当纺丝时液面高度相同时，电流随着电压线性增大。     

Non-ohmic electric conduction in polycrystalline thulium oxide

The current voltage behaviour of polycrystalline Tm₂O₃ has been investigated at 77 K and 300 K to 350 K. At low voltages, the conduction is ohmic while at higher voltages the current has a quadratic dependence on voltage. The voltageV _T at which the transition from ohmic to non-ohmic conduction takes place changes from 180 V to 100 V as temperature increases from 77 K to 350 K. The results are interpreted in terms of the Rose theory of space charge limited currents (sclc) in defect insulators containing shallow traps.     

Study of a particular type of ferroresonance--The cyclic resonance

A device yielding a stabilized voltage with a steady wave-form by means of ferroresonance is described. Experimental results (voltages, currents, and reactive power) are plotted as functions of the applied voltage, and the applied voltage range over which ferroresonance can steadily occur is determined.     

D.C. I–V characteristics and steady-state photoconductivity of Au/Pb2CrO5/SnO2 sandwich-structure films under illumination in the visible region

The room temperature d.c. current–voltage (I–V) characteristics of an Au/Pb2CrO5/SnO2 sandwich-structure 1.39 μm thick film have been measured for d.c. voltages, Vd.c., in the range 0.25 V≤Vd.c.≤5.0 V. These measurements were carried out under both dark and visible-light illumination conditions. For Vd.c.<2.5 V, the I–V curves of the sample in both dark and light environments were found to be non-linear and conform to space-charge-limited (SCL) current governed by traps uniformly distributed in energy. At higher d.c. voltages, a nearly Mott–Gurney V2 behaviour of the dark current has been observed, whereas the I–V behaviour of the illuminated specimen was a combination of an ohmic conduction and a V2 dependence at low illumination levels and became highly ohmic at large light intensities. This behaviour can be understood in terms of a reduction in the SCL dark current in favour of a larger ohmic d.c. photocurrent as a result of neutralization of the majority-carrier space charge by the photogenerated minority carriers of the electron–hole pairs produced under the illumination with visible light of energy ℏω≅EG(∼2.1–2.3 eV for the Pb₂CrO₅ material). The d.c. photocurrent, I_phot, at a fixed d.c. voltage, was found to follow a power-law dependence on light intensity, F, of the form I_phot∝F^γ, with the exponent γ being dependent on the applied d.c. voltage. At the low-voltage side (V_d.c.<1.5 V), γ∼0.5, a value usually obtained when the photoconductivity behaviour is governed by bimolecular recombination mechanisms. As the d.c. voltage is increased further, γ increases monotonically until it saturates at a value of about 0.9 for d.c. voltages beyond 3.5 V, where monomolecular recombination processes seem to be more operative with increasing d.c. voltage. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of voltage on the conduction of a high-density polyethylene/carbon black composite at the NTC region

The time dependences of current and Joule heating under various voltages are studied to high-density polyethylene (HDPE) filled with carbon black (CB) of 0.082 in volume at an ambient temperature of 158 °C located at the region of negative temperature coefficient (NTC) of resistivity. The composite shows either a transition from the intrinsic to the steady conductions or an irreversible electrical breakdown depending on the applied voltage. The intrinsic conduction in the absence of Joule heating is explained combining two electron tunneling processes while the electric field induced NTC effect is related to the production of additional conducting pathways resulted from cold-emission.     

Conduction mechanism in amorphous In2III X3VI thin films

Amorphous In₂ ^IIIX₃ ^VIfilms (X = Te or Se) are obtained by vacuum thermal evaporation of bulk materials on glass substrates. The current - voltage characteristics in the temperature range 298–378 K and in the thickness range 212–652 nm exhibited a transition from an ohmic region in the lower field followed by non-ohmic region in the high field region, which has been explained by the anomalous Poole-Frenkel effect. The temperature dependence of current in the ohmic region is of thermally activated process. The variation of dielectric constant with temperature is investigated for the two compounds.     

Nanostructured layer formed on CP-Ti by plasma electrolysis (effect of voltage and duty cycle of cathodic/anodic direction)

The present work reports the usage of nanocrystalline plasma electrolytic saturation (PES) by applying pulsed current in an organic electrolyte based on Glycerol. Response surface methodology was applied to optimize the operating conditions for small nanocrystallite sizes of coatings. The levels studied were peak of applied cathodic voltage range between 500 and 700 V, peak of applied anodic voltage between 200 and 400 V and the ratio of duty cycle of cathodic direction to duty cycle of anodic direction at 0.25–0.35. The usage of high applied cathodic voltages and low anodic voltages and also low ratio of duty cycle of cathodic direction to duty cycle of anodic direction is more suitable for achieving lower sizes of complex nanocrystallites. The samples with high height to width ratio of distribution curves of nanocrystallites have simultaneously, smaller average sizes and lower length to diameter ratio of nanocrystallites.     

Space charge limited currents in graded films

The equilibrium current density is calculated for films in which the conductivity is a function of depth. Three specific cases are considered: (a) conductivity falling monotically with distance away from the injecting electrode; (b) conductivity rising monotonically; and (c) conductivity sharply peaked in the middle of the specimen. In all cases the current density is ohmic at low voltage and obeys the Mott-Gurney law at high applied voltage. There is a smooth transition between the limits, with no negative resistance region, and switching is unlikely to occur for this combination of ohmic and space charge limited transport mechanisms.     

Electrical conduction and low voltage blue electroluminescence in vacuum-deposited organic films

Bright blue (400–500 nm) recombination electroluminescence (EL) has often been observed from anthracene crystals with solid electrodes; external quantum efficiencies of 1%–8% have been seen and the theoretical efficiency is approximately 40%. The power efficiency has always been greatly degraded by the high voltages necessary to obtain reasonable currents through the comparatively thick crystals used. We report the preparation, and the structural, electrical and EL properties of approximately 0.6 μm vacuum-deposited anthracene films through which large steady state current densities can be passed at rather low applied voltages. The films showed the critical optimization effect, various structural and electrical properties exhibiting sharp singularities when the films were prepared at substrate temperatures within a narrow range near ?60 °C. EL visible in normal room lighting was obtained at applied voltages of only about 30 V and up; in thinner films, EL could be seen in a darkened room at only about 12 V. This is apparently the first time that clearly visible EL has been reported from an organic material at voltages significantly less than 100 V. Broadly similar results were obtained for perylene and 1,12-benzperylene films; EL does not appear to have been observed before from these substances in any form. We discuss in some detail the prospects for practical EL devices based on organic films. In view of our results, and of the great improvements which are now probably feasible, we conclude that the prospects are promising; if these improvements can be realized, such devices could include high efficiency blue light-emitting diodes, and large-area broader wavelength systems for illumination applications.     

Current transport mechanisms for heterojunctions of a-Se on various crystalline wafers (n-Si, p-Si and n-GaAs)

Heterojunction diodes fabricated by thermal evaporation of p-type amorphous selenium (a-Se) on various crystalline wafers (n-Si, p-Si and n-GaAs) are analyzed by measuring their current-voltage (J-V) characteristics. The measured J-V characteristics for the investigated devices of configuration Au/a-Se/c-wafer/Al, exhibit a rectifying behavior and the bulk effect of the a-Se layer. For low forward voltage, the conduction mechanism is dominated by recombination of the carriers in the amorphous side of the space charge region. At higher voltage, the J-V characteristics could be divided into two regions: an ohmic region and a space charge limited current region. The values of the activation energy obtained from the ohmic region are in agreement with those obtained from dc conductivity measurements in the same range of temperature. The reverse bias activation energy values at different temperatures are in agreement with those obtained from the temperature dependence of the forward saturation current, supporting the proposed recombination mechanism of conduction.