Dielectric and electrical properties of ordinary Portland cement and slag cement in the early hydration period

The dielectric constant and electrical conductivity of ordinary Portland cement (OPC) with water-cement ratios (w/c) of 0.30, 0.35 and 0.40 were measured for the first 30 h hydration, using a microwave technique in the frequency range 8.2–12.4 GHz. It was found that both the dielectric constant and electrical conductivity of the cement paste are sensitive to the water-cement ratio, the higher the w/c value, the greater the dielectric constant and electrical conductivity, and the longer the hydration time. We also found that the higher the frequency the greater the electrical conductivity but the smaller the dielectric constant. The dielectric constant and electrical conductivity of high- and low-slag cement with water-solid ratio (w/s) of 0.40 were measured in the first 30 h after mixing. The changes in dielectric constant and electrical conductivity of low-slag cement with time are similar to that of OPC, but the high-slag cement shows very different dielectric and electrical properties compared with OPC and low-slag cement. The relationship between the dielectric and electrical properties of cement paste and cement hydration was also discussed.     

Properties of polycarbonate (PC)/multi-wall carbon nanotube (MWCNT) nanocomposites prepared by melt blending

This investigation deals with an easy method to develop electrical conductivity in polycarbonate (PC)/multi-wall carbon nanotube (MWCNT) nanocomposites with low loading of MWCNT. This was achieved by melt-blending of in-situ bulk polymerized low molecular weight poly(methyl methacrylate) (PMMA)/MWCNT nanocomposites and PC in various compositions at 280 degrees C in internal mixer. Differential scanning calorimetry (DSC) study showed single Tg in (85/15 w/w) PC/PMMA blend, indicating miscibility of PC and PMMA in the blend. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies of the melt-blended PC/PMMA/MWCNT nanocomposites revealed homogeneous dispersion and distribution of MWCNTs in PC matrix. Finally, through optimizing the blending composition of PC and PMMA/MWCNT nanocomposites, electrical conductivity of 3.74 x 10(-7) S x cm(-1) was achieved in the (85/15 w/w) PC/PMMA/MWCNT nanocomposites with the MWCNTs loading as low as approximately 0.37 wt%. Storage modulus of PC was found to increase significantly in presence of small amount (0.37 wt%) of MWCNTs in the nanocomposites.     

电场诱导多壁碳纳米管有序排列对多壁碳纳米管/环氧树脂复合材料性能的影响

采用交流（AC）电场诱导法制备了多壁碳纳米管（MWCNTs）均匀分散且定向有序排列的MWCNTs/环氧树脂复合材料。采用SEM、偏振拉曼光谱等研究了电场强度、MWCNTs含量、加电时间及温度（黏度）等因素对MWCNTs定向排列的影响,讨论了MWCNTs有序排列对MWCNTs/环氧树脂复合材料电学和力学性能的影响。结果表明：MWCNTs沿电场方向有序排列;MWCNTs/环氧树脂复合材料施加AC电场后的拉曼强度明显高于未施加电场的情况;当MWCNTs含量从0wt%增加到0.025wt%时,MWCNTs/环氧树脂复合材料导电率从2.3×10^-12 S/cm增加到1.3×10^-8 S/cm,增加了约4个数量级;MWCNTs含量为2.5wt%时,MWCNTs/环氧树脂复合材料拉伸强度提高了26.3%。     

Ni、Si元素配比对Cu-Cr-Zr合金组织与性能的影响

在Cu-Cr-Zr合金中添加Ni、Si元素,制备Cu-0.6Cr-0.15Zr、Cu-2.8Ni-0.7Si-0.6Cr-0.15Zr(w(Ni)/w(Si)=4∶1)、Cu-2.8Ni-0.9Si-0.6Cr-0.15Zr(w(Ni)/w(Si)4∶1)、Cu-2.8Ni-0.56Si-0.6Cr-0.15Zr(w(Ni)/w(Si)4∶1)共4种合金。研究了Ni、Si元素及其配比对合金组织及性能的影响。结果表明:Ni、Si元素细化了合金组织,增强了合金高温力学性能。合金时效初期先析出CrSi2化合物,时效后期析出相颗粒主要有CrSi2、Ni2Si、ZrCrSi2,形态为长条形、椭圆形及圆盘状。时效处理后,与Cu-0.6Cr-0.15Zr合金相比,加入Ni、Si元素后合金硬度从131HV上升到240HV以上;导电率从88%IACS左右降到40%IACS左右。Ni、Si元素配比对导电率的峰值影响有限,在4%IACS~9%IACS;对硬度峰值的影响在20HV~30HV之间。     

Resistive-switching behavior in polycrystalline CaCu(3)Ti(4)O(12) nanorods

Highly aligned CaCu(3)Ti(4)O(12) nanorod arrays were grown on Si/SiO(2)/Ti/Pt substrates by radio-frequency sputtering at a low deposition temperature of 300 °C and room temperature. Structural and morphological studies have shown that the nanostructures have a polycrystalline nature and are oriented perpendicular to the substrate. The high density of grain boundaries in the nanorods is responsible for the nonlinear current behavior observed in these arrays. The current-voltage (I-V) characteristics observed in nanorods were attributed to the resistive memory phenomenon. The electrical resistance of microcapacitors composed of CaCu(3)Ti(4)O(12) nanorods could be reversibly switched between two stable resistance states by varying the applied electric field. In order to explain this switching mechanism, a model based on the increase/decrease of electrical conduction controlled by grain boundary polarization has been proposed.     

Electric‐Field‐Tunable Conductivity in Graphene/Water and Graphene/Ice Systems

This study demonstrates that the application of an external electrical potential to a phenyl‐sulfonic functionalized graphene (SG)/water suspension distinctly enhances its electrical conductivity via the structural transition from isolated clusters to a 3D SG network. Microstructural and alternating current impedance spectroscopy studies indicate that the surface charge plays an important role in the state of dispersion and connectivity of the SG in the suspension due to the potential‐dependent interactions with functional groups on the SG surface in the presence of an external electrical potential. In addition, the conductive SG/ice can be produced via liquid–solid phase transition of the SG/water suspension in the presence of an external electrical potential, which shows a one‐order magnitude improvement in electrical conductivity compared with pure ice. The electric‐field‐tunable property advances the understanding of nanofluid systems and has many potential applications.     

Effect of evaporated copper and aluminum on post-annealed SiOC(-H) films deposited using plasma-enhanced chemical vapor deposition

Low dielectric constant SiOC(-H) films were deposited on p-type Si(100) substrates by plasma-enhanced chemical vapor deposition (PECVD) using dimethyldimethoxysilane (DMDMOS, C₄H₁₂O₂Si) and oxygen gas as precursors. We studied the detailed electrical characterization of SiOC(-H)/p-Si(100) interfaces using different experimental parameters for using the multilevel interconnections in ultra large-scale integrated circuits (ULSI). To improve the SiOC(-H)/p-Si(100) interface, the wafer was cleaned using the RCA process and rinsed with deionized water. The deposited SiOC(-H) films were annealed at different temperatures ranging from 250 to 450 °C in a vacuum. The interface properties of the SiOC(-H)/p-Si(100) with Cu/SiOC(-H)/p-Si(100)/Al metal-insulator-semiconductor (MIS) structures were investigated by capacitance-voltage (C-V) measurement with a flat band shift by electric field stress. Trapped charge, fixed oxide charge, and the interface trap density of SiOC(-H) films were related to the dielectric breakdown and leakage current density at the SiOC(-H)/p-Si(100) interface. From these analyses, detailed electrical properties defining the interface states of the MIS structures were reported.     

SO42-/TiO2固体超强酸掺杂可剥离膜的放射性去污性研究

制备出酸度- 13. 20 相似文献   

影响低密度聚乙烯/氧化锌复合材料场致电导因素的研究

氧化锌(ZnO)是一种电导率具有场强依赖性的半导体材料,由其经烧结而制备的非线性电阻器件在稳压、过压保护、防雷、灭孤、消噪、补偿、消磁等方面得到了广泛的应用.以低密度聚乙烯(LDPE)和氧化锌粉末共混复合体系为研究对象,实验研究了影响LDPE/ZnO复合材料场致电导的主要因素.研究结果表明,增加ZnO的掺量、升高温度和减小压力均能提高LDPE/ZnO复合材料的非线性程度;对于按不同生产工艺制备的ZnO,其晶粒生长行为的不同导致晶粒结构的差异,从而使得含有不同制备工艺的ZnO的LDPE/ZnO复合材料的电导特性存在较大差别.     

An electromechanically coupled theory for piezoelastic beams taking into account the charge equation of electrostatics

Summary The present paper is devoted to the coupling between electrical and mechanical fields in piezoelastic structures. In the present contribution, an electromechanically coupled technical theory for flexural and extensional deformations of piezoelastic composite beams is developed. Such a technical theory should be of special interest for control applications, where a lower-order but sufficiently accurate modelling is required.In a first step, an equivalent single-layer theory of the Timoshenko-type for composite beams is utilized. The influence of shear, rotatory inertia as well as the influence of the electric field is taken into account in this technical beam theory. The electric field is unspecified so far in this formulation, but is coupled to the deformation by means of the charge equation of electrostatics. In order to incorporate this coupling, the electric potential is approximated by a power series in the thickness direction of the beam. Terms up to an order of two are considered in the approximation. The formulation then is adapted to the electric boundary conditions at the upper and lower sides of the electroded piezoelectric layers, namely that the electrodes have to be equipotential areas. Putting this distribution into an electrical variational principle, a weak one-dimensional formulation of the charge equation of electrostatics is obtained for the axial distribution of the electric potential. Prescribing the electric potential at the electrodes, and specifying the electrical boundary conditions at the vertical ends of the layer, this weak form completes the proposed electromechanically coupled technical theory for composite piezoelastic beams.In order to demonstrate the influence of the coupling between deformation and electric field, the quasi-static behavior and free flexural vibrations of a symmetrically laminated 3-layer beam are studied in detail. Results are compared to results of coupled finite element computations as well as to results obtained by a simplified theory, previously developed by the authors.The present paper is an extended version of a lecture presented at the Symposium Coupled Field Problem in Smart Structures in the course of the 1999 ASME Mechanics & Materials Conference, June 27–30, 1999, Virginia Polytechnice Institute and State University, Blacksburg, Virginia.     

DNA sequencing up to 1300 bases in two hours by capillary electrophoresis with mixed replaceable linear polyacrylamide solutions

This paper presents results on ultralong read DNA sequencing with relatively short separation times using capillary electrophoresis with replaceable polymer matrixes. In previous work, the effectiveness of mixed replaceable solutions of linear polyacrylamide (LPA) was demonstrated, and 1000 bases were routinely obtained in less than 1 h. Substantially longer read lengths have now been achieved by a combination of improved formulation of LPA mixtures, optimization of temperature and electric field, adjustment of the sequencing reaction, and refinement of the base-caller. The average molar masses of LPA used as DNA separation matrixes were measured by gel permeation chromatography and multiangle laser light scattering. Newly formulated matrixes comprising 0.5% (w/w) 270 kDa and 2% (w/w) 10 or 17 MDa LPA raised the optimum column temperature from 60 to 70 degrees C, increasing the selectivity for large DNA fragments, while maintaining high selectivity for small fragments as well. This improved resolution was further enhanced by reducing the electric field strength from 200 to 125 V/cm. In addition, because sequencing accuracy beyond 1000 bases was diminished by the low signal from G-terminated fragments when the standard reaction protocol for a commercial dye primer kit was used, the amount of these fragments was doubled. Augmenting the base-calling expert system with rules specific for low peak resolution also had a significant effect, contributing slightly less than half of the total increase in read length. With full optimization, this read length reached up to 1300 bases (average 1250) with 98.5% accuracy in 2 h for a single-stranded M13 template.     

共聚炭化法制备多孔炭材料及其电容性能研究

采用酚醛树脂(PF)为热稳定聚合物, 端环氧基的聚合物(QS)为热不稳定聚合物, 利用聚合物共聚炭化法制备多孔炭。经红外光谱分析及热重分析证实, 在酚醛树脂与QS的共聚固化物中, QS链段上的环氧基与酚醛树脂链段上的酚羟基发生反应生成醚键, QS接枝到酚醛树脂的链段上。BET比表面积、孔结构和电化学性能分析表明: 在共聚固化物PF/QS的炭化过程中, QS的热解逸出能起到造孔作用, 并随着QS用量的增加多孔炭的比表面积先增大后减小。QS加入量为15%的多孔炭具有最大的比表面积609.0 m²/g、总孔容0.28 cm³/g和微孔孔容0.22 cm³/g, 与聚合物共混炭化法相比, 在相同热不稳定聚合物加入量条件下, 多孔炭的比表面积和孔容都有所提高。该多孔炭电极在30wt% KOH电解液中的比电容达177.5 F/g, 具有良好的电容特性。     

Effect of silver in Y1Ba2Cu3O7−x samples

Two techniques for preparing Y-Ba-Cu-O/Ag specimens are presented: (a) solid-state reaction, and (b) normal precursors dissolved in hot concentrated nitric acid and dried in air. The samples are characterized by scanning electron microscopy (SEM), scanning Auger, X-ray diffraction, optical microscopy and electrical resistivity measurements. In comparison with a normal 1-2-3 superconductor it was found that the normalized resistance [R(T)/R(280 K)] decreases for both preparation methods. The material retained a high initial temperature of superconductivity, T _c, for a maximum of 6% w/o Ag₂O during solid-state reaction and 6.5% w/o Ag₂O for samples dissolved in hot concentrated nitric acid and dried in air.     

P-doped CoSe2 nanoparticles embedded in 3D honeycomb-like carbon network for long cycle-life Na-ion batteries

We report for the first time a Na-ion battery anode material composed of P-doped CoSe2 nanoparticles(P-CoSe2)with the size of 5-20 nm that are uniformly embed in a 3D porous honeycomb-like carbon network.High rate capability and cycling stability are achieved simultaneously.The honeycomb-like carbon network is rationally designed to support high electrical conductivity,rapid Na-ion diffusion as well as the accommodation of the volume expansion from the active P-CoSe2 nanoparticles.In particular,heteroatom P-doping within CoSe2 introduces stronger P-Co bonds and additional P-Se bonds that signif-icantly improve the structure stability of P-CoSe2 for highly stable sodiation/desodiation over long-term cycling.P-doping also improves the electrical conductivity of the CoSe2 nanoparticles,leading to highly elevated electrochemical kinetics to deliver high specific capacities at high current densities.Benefiting from the unique nanostructure and atomic-level P-doping,the P-CoSe2(2∶1)/C anode delivers an excel-lent cycle stability with a specific capacity of 206.9 mA h g-1 achieved at 2000 mA g-1 after 1000 cycles.In addition,this material can be synthesized using a facile pyrolysis and selenization/phosphorization approach.This study provides new opportunities of heteroatom doping as an effective method to improve the cycling stability of Na-ion anode materials.     

High performance hard carbon coatings (diamond‐like coatings)

Different dLc coating types are applied at an industrial scale by sulzer Metco thin Film. The coatings are generated with different coating architecture. Deposition methods are: magnetron sputtering, electron beam evaporation and PA‐cVd. Reactive magnetron sputtering is used to deposit metal containing a‐c:h coatings (a‐c:h:Me), e.g. MAXit W‐ch. Pure a‐c:h coatings as functional top coatings are used for cavidur®, MAXit® AhdLc and special versions of dylyn® coatings. In addition to the pure a‐c:h coatings, doped a‐c:h coatings are also used. The dylyn® family of coatings is comprised of at least one layer a‐c:h:si:O. The dylyn® coatings may be doped with metal (a‐c:h:ti:si:O) to adapt selected properties like electrical conductivity.     

高密度聚乙烯—炭黑（HDPE—C）PTC材料的导电机制

利用炭黑与高密度聚乙烯复合制成了具有ＰＴＣ功能的导电材料（ＨＤＰＥ－Ｃ）,根据目前各种地电理论,提出“晶界”导电模型,并推导出了炭黑的填加量（Ｌ）、高聚物结晶体大小（α）、碳粒子半径（ｒｃ）、碳粒子间距（Ｘ）之间的关系,晶界导电模型与实验结果有较好的符合。     

Electroluminescence from light-emitting diodes by using water-dispersed ZnSe nanocrystals and polymer

Electroluminescence was obtained from an indium-tin-oxide/poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV): ZnSe/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/ 8-tris-hydroxyquinoline (Alq3)/LiF/Al structured device, in which ZnSe nanocrystals were synthesized in aqueous solution by using mercapto-acetate acid as stabilizer. The mechanical, electrical, and optical properties of the device were established. The photoluminescence and electroluminescence spectra changed with the mass ratio of ZnSe to MEH-PPV in the composite. Comparison between the absorption spectra and photoluminescence spectra of the ZnSe nanocrystals and the MEH-PPV thin film exhibited an effective energy transfer from ZnSe nanocrystals to MEH-PPV, which was one reason for the difference between the photoluminescence and electroluminescence spectra of the MEH-PPV: ZnSe composite film. The recombination mechanism of ZnSe nanocrystals under photo excitation and electric injection was investigated with the help of a single layer device structure of indium-tin-oxide/ZnSe/LiF/Al.     

A Numerical Investigation on a c.w. High-power,Electron-beam,Pre-ionized He : N 2 : CO 2 : CO Laser

We studied some kinetic, fluid-dynamic and electrical problems arising in the numerical modelling of a c.w. TE high power CO₂ laser operating with N₂, He and CO additives. We adapted a five-temperature pulsed laser model to the c.w. case by coupling a set of fluid-dynamic equations to the kinetic set. We added the rate equation for the secondary electron density. We calculated in some detail the ionization term and fitted experimental results to determine attachment and recombination coefficients in the discharge chamber. In order to solve our equations a numerical code has been developed. By this means we investigated the effects of temperature, density and velocity variations in the flowing mixture on the small signal gain of the device. We obtained profiles in the laser chamber of the sustainer current, small signal gain and fluid-dynamic parameters. A simple (Fabry-Perot) optical cavity model has been used to calculate output power and electrical efficiency of the device. A comparison of numerical code predictions and experimental results is presented.     

Surface electrical conductivity in ZnS(Cu,Cl, Mn) thin films

The surface electrical conduction in an In₂O₃(Sn)/ZnS(Cu, Cl, Mn)/Al thin film system was investigated by measuring the dependence of the current through the ZnS(Cu, Cl, Mn) film on the application of a sinusoidal voltage to two electrodes on the surface of the film. The measurements were carried out in an arrangement with an additional d.c. voltage applied between one of the upper electrodes and the lower electrode. The results obtained are discussed on the basis of a proposed theoretical model.     

Preparation and Application of Flexible Ethylene Vinyl Acetate Adhesive Composites by Ultrasonic-Assisted Forced Infiltration

Herein, carbon nanotubes (CNTs)–cellulose nanocrystals (CNCs)/ethylene-vinyl acetate (EVA) composite are prepared with excellent bonding properties, electrical conductivity, and thermal conductivity using an ultrasonic-assisted forced infiltration (UAFI) method. The CNTs–CNCs (10:1)/EVA composite had the highest shear (82.9 N) and strip (12.2 N) forces at the interface when bonding leather to fabric as an interface bonding material (IBM). Different mass ratios of CNTs to CNCs in the composites lead to different electrical and thermal conductivity properties. When the mass ratio of CNTs to CNCs is 10:1, the CNTs–CNCs(10:1)/EVA composites reach an electrical and thermal conductivity of 158.37 S m⁻¹ and 6.351 W (m·K)⁻¹, respectively. In addition, the CNTs–CNCs(10:1)/EVA composite shows excellent thermal stability, mechanical properties, thermal performance, and electromagnetic shielding. The prepared EVA composite has a broad application prospect in IBM.