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Volume Resistivity (volume + resistivity)
Selected AbstractsElectrically Conductive Thin Films Prepared from Layer-by-Layer Assembly of Graphite PlateletsADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Mubarak Alazemi Abstract Layer-by-layer (LBL) assembly of carbon nanoparticles for low electrical contact resistance thin film applications is demonstrated. The nanoparticles consist of irregularly shaped graphite platelets, with acrylamide/,, -methacryl-oxyethyl-trimethyl-ammonium copolymer as the cationic binder. Nanoparticle zeta (,,) potential and thereby electrostatic interactions are varied by altering the pH of graphite suspension as well as that of the binder suspension. Film thickness as a function of zeta potential, immersion time, and the number of layers deposited is obtained using Monte Carlo simulation of the energy dispersive spectroscopy measurements. Multilayer film surface morphology is visualized via field-emission scanning electron microscopy and atomic-force microscopy. Thin film electrical properties are characterized using electrical contact resistance measurements. Graphite nanoparticles are found to self-assemble onto gold substrates through two distinct yet overlapping mechanisms. The first mechanism is characterized by logarithmic carbon uptake with respect to the number of deposition cycles and slow clustering of nanoparticles on the gold surface. The second mechanism results from more rapid LBL nanoparticle assembly and is characterized by linear weight uptake with respect to the number of deposition cycles and a constant bilayer thickness of 15 to 21,nm. Thin-film electrical contact resistance is found to be proportional to the thickness after equilibration of the bilayer structure. Measured values range from 1.6,m,,cm,2 at 173,nm to 3.5,m,,cm,2 at 276,nm. Coating volume resistivity is reduced when electrostatic interactions are enhanced during LBL assembly. [source] Effect of weak reductant on properties of electroless copper polyacrylonitrile nanocomposites for electromagnetic interference shieldingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010Keng-Yu Tsao Abstract In this work, the electroless copper method with different reductant compositions (NaHSO3/Na2 S2O3·5H2O and Na2S2O3·5H2O) without sensitizing and activating, was used to deposit copper-sulfide deposition on the polyacrylonitrile (PAN) surface for electromagnetic interference (EMI) shielding materials. The weak reductant, NaHSO3, in the electroless copper method was used to control the phase of copper-sulfide deposition. The Cux(x=1,1.8)S was deposited on the PAN (CuxS-PAN) by reductant composition (NaHSO3/Na2S2O3·5H2O) and the Cux(x=1,1.8)S deposition of CuxS-PAN possesses three kinds of copper-sulfide phases (CuS, Cu1.75S and Cu1.8S). However, the electroless copper with reductant was only Na2S2O3·5H2O (without weak reductant, NaHSO3), the hexagonal CuS deposition was plated on the PAN (CuS-PAN) and increased the EMI shielding effectiveness of CuS-PAN composites about 10,15 dB. In this study, the best EMI SE of CuS-PAN and CuxS-PAN composites were about 27,30 dB and 15,17 dB respectively, as the cupric ion concentration was 0.24 M. The volume resistivity of CuS-PAN composite was about 1000 times lower than that of CuxS-PAN composite and lowest volume resistivity of CuS-PAN composites was 0.012 , cm, as the cupric ion concentration was 0.24 M. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Synthesis and comparative physicochemical investigation of partly aromatic cardo copolyestersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007N. B. Joshi Abstract Copolyesters were synthesized through the condensation of 0.0025 mol of 1,1,-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 0.0025 mol of ethylene glycol/propylene glycol/1,4-butanediol/1,6-hexane diol, and 0.005 mol of terephthaloyl chloride with water/chloroform (4:1 v/v) as an interphase, 0.0125 mol of sodium hydroxide as an acid acceptor, and 50 mg of cetyl trimethyl ammonium bromide as an emulsifier. The reaction time and temperature were 2 h and 0°C, respectively. The yields of the copolyesters were 81,96%. The structures of the copolyesters were supported by Fourier transform infrared and 1H-NMR spectral data and were characterized with the solution viscosity and density by a floatation method (1.1011,1.2697 g/cm3). Both the intrinsic viscosity and density of the copolyesters decreased with the nature and alkyl chain length of the diol. The copolyesters possessed fairly good hydrolytic stability against water and 10% solutions of acids, alkalis, and salts at room temperature. The copolyesters possessed moderate-to-good tensile strength (11,37.5 MPa), good-to-excellent electric strength (19,45.6 kV/mm), excellent volume resistivity (3.8 × 1015 to 2.56 × 1017 , cm), and high glass-transition temperatures (148,195°C) and were thermally stable up to about 408,427°C in a nitrogen atmosphere; they followed single-step degradation kinetics involving 38,58% weight losses and 34,59% residues. The copolyesters followed 2.6,2.9-order degradation kinetics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Effect of ATH content on electrical and aging properties of EVA and silicone rubber blends for high voltage insulator compoundJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007M. A. Pradeep Abstract The effect of trihydrated alumina (Al2O3, 3H2O) (ATH) filler in ethylene-vinyl acetate copolymer (EVA) and silicone rubber blends was investigated by performing a series of laboratory experiments to simulate different natural aging conditions. Samples with varying ATH content in a 50-50 blend of EVA and polydimethylsiloxane (PDMS) (silicone rubber, MQ) were tested to investigate the tracking resistance, resistance to UV radiation, corona, heat, and water immersion. Changes in surface resistivity, volume resistivity, and hydrophobic characteristics were evaluated for different compounds having ATH content. These exercises were mainly carried out to optimize the filler level. In immersed condition the water absorption increases with ATH content. The recovery of hydrophobicity, after aging by heat, is appreciable at higher ATH levels, than at lower ATH levels. The tracking and erosion resistance decrease as ATH content increases. When compounds containing different ATH content were subjected to corona treatment, the samples with higher ATH levels exhibited better results. All samples changed their color to a darker shade and there was an increase in the hydrophobicity, when subjected to UV radiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3505,3516, 2007 [source] Piezoresistivity in continuous carbon fiber polymer-matrix compositePOLYMER COMPOSITES, Issue 1 2000Shoukai Wang Piezoresistivity involving the volume resistivity of a continuous unidirectional carbon fiber epoxy-matrix composite in the fiber direction decreasing reversibly upon tension in the fiber direction was observed by the four-probe method, due to an increase in the degree of fiber alignment. Use of the two-probe method resulted in measurement of the contact resistance rather than the volume resistance. The contact resistance increased reversibly upon tension. [source] | ||||||||||