Materials Literature
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The bandstructure of pentacene is calculated using first-principles density functional theory. A large anisotropy of the hole and electron effective masses within the molecular planes is found. The band dispersion of the HOMO and the LUMO is analyzed with the help of a tight-binding fit. The anisotropy is shown to be…
Measurements of light emission from a scanning tunneling microscope probing a Na overlayer on the (111) surface of Cu are reported along with results of a model calculation that essentially agree with the experimental ones. The observed light emission spectra show two characteristic features depending on the bias volt…
Plasma treatment of polymers encompasses a variety of plasma technologies and polymeric materials for a wide range of applications and dates back to at least the 1960s. In this article we provide a brief review of the United States patent literature on plasma surface modification technologies and a brief review of the…
Experiments designed to investigate surface degradation of XLPE by corona discharges between circular electrodes are described. Charge injection behavior was also studied by measuring the surface potential V/sub s/, which was found to be radially symmetrical and strongly influenced by the particular conditions of the…
The damage in power capacitor dielectrics by harmonics in power networks is investigated. Five typical distorted waves generated by an HV (high-voltage) harmonic testing installation were recorded in tests of four model types of capacitors. Results show that all waves containing harmonics of different order have damag…
A solar photovoltaic (PV) thermoelectric generator (TEG) hybrid system combines the economics of a solar photovoltaic system with the reliability and heating capability of a thermoelectric generator system. The solar system provides power during seasons with abundant sunshine while the thermoelectric generator system…
A description is given of the principles and practice regarding degree-of-polymerization (DP) measurements and applications in which they are used to evaluate the degree of aging. The authors discuss the possibility of expediting lifetime predictions using expert system techniques. Experience shows that the DP measure…
A research program has been initiated to determine if propylene carbonate can be used as an insulator in the high-voltage accelerator field. Electrical properties, such as dielectric strength, resistivity, frequency response, and surface tracking, have been investigated. Initial tests show that propylene carbonate can…
The Solidification Using a Baffle in Sealed Ampoules (SUBSA) and Pore Formation and Mobility Investigation (PFMI) furnaces were developed for operation in the International Space Station (ISS) Microgravity Science Glovebox (MSG). Both furnaces were launched to the ISS on STS-111, June 4, 2002, and are currently in use…
Abstract Polymerization of styrene in aqueous dispersions of the dodecanamide derivative of poly(propyleneimine) dendrimer DAB‐ dendr ‐(NH 2 ) 64 and sodium dodecyl sulfate (SDS) produced stable latices. With initial SDS concentrations of 10 mM or less, molar ratios of SDS to dendrimer end groups ranging from 2.3:1 to…
The technological revolution and busy schedule compel human society to search for better civic amenities. This leads to the use of modern personal care goods such as disposable diapers and sanitary napkins. Presently, all of the goods use microporous polyolefin films. The high-strength microporous polyolefin films als…
Electric stress, voltage waveshape, temperature, contaminants and insulation resistance to oxidation have been analyzed as to their influence on triggering breakdown of a water-treed polymer. The transition from a water tree to an electrical tree is dependent on several factors, including voltage waveshape, and magnit…
A laboratory investigation was undertaken to study the nature of surface charge decay and its mechanism with several synthetic organic materials after both corona and contact charging in different environments. Some results for low-density polyethylene (LDPE) are presented and discussed. The behaviour of the decay sho…
Six kinds of typical oil gaps were designed and tested to simulate partial discharges (PD) in the insulation of power transformers. The frequency spectra of acoustic emission (AE) of PD in those gaps were presented and investigated with a computer-aided measuring system. The attenuation of AE and the variation of its…
Graft copolymerization of 2-Hydroxy ethyl methacrylate (HEMA) on to chitosan was studied using cerium (IV) as the initiator. Optimization of the grafting was worked out by varying the reaction time and monomer concentration. Under controlled conditions, up to 685% grafting with a grafting yield of 92.4% was achieved.…
The authors present a brief assessment of the experience gained with synthetic dielectrics as applied to solid extruded cables and review the up-to-date work carried out on the development of oil-filled commercial cables insulated with polypropylene laminated paper (PPLP). The primary emphasis is placed on the relativ…
New copper(II) toluate complexes with saturated monoheterocyclic bases, substituted piperidines, of the type Cu(OOCR)2L (where R = 2‐, 3‐, or 4‐CH3C6H4 and L = 1‐methyl‐, 1‐ethyl‐ or 2,6‐dimethylpiperidine) have been synthesized and characterized by elemental analyses, IR, electronic reflectance and EPR spectral and m…
Corona charging is a powerful method for studying storage and electric charge transport in dielectric films. The development of this technique for the study of polymer foils is summarized. The improvement achieved with the use of a biased vibrating grid, allowing the measurement of the potential buildup is commented o…
The thermal aging of cross-linked polyethylene (XLPE) cable models has been investigated to obtain information on aging effects and mechanisms. After thermal life tests, XLPE cable models were subjected to chemical, physical, electrical and microstructural characterizations. The results of density, melting point and e…
Measurements carried out on a large wall bushing are described. They show that uneven rain distribution can cause flashovers even at very low pollution levels. A possible mechanism for these rain flashovers is proposed. It is reported that water-repellent surfaces provide an efficient remedy for this type of flashover…