Materials Literature
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The effect of electrode surface roughness on the breakdown potential in SF 6 , SF 6 -N 2 , and SF 6 -CO 2 has been measured and calculated using two surface-roughness models (a multi-ridge model and a single-needle-tip-protrusion model). The calculations are in reasonable agreement with the experimental results, indic…
Abstract Blends of polyimide isomers containing hexafluoroisopropylidene in the central moiety of the diamine residue have been studied. The isomers differed by having either a meta or a para linkage between the diamine and dianhydride residues. The miscibility of these materials was investigated by studying the glass…
Abstract Porous polydimethylsiloxane (PDMS) membranes were prepared by catalytic hydrosilyiation cure of a silicone compound containing a vinyl group and a SiH group in the presence of additives such as water, ethanol, ethylene glycol, and 2‐methoxyethanol. The pores were formed in the membrane as a result of hydrogen…
Abstract Unreacted PC/PBT blends have been obtained by melt blending in all the composition ranges. The followed processing method produced partially miscibilized and crystalline blends. The plot of the density of the amorphous part of the blends against its composition indicates that this parameter is more important…
Abstract Injectable collagen is a concentrated dispersion of collagen fibers in aqueous solution that is used to correct dermal contour defects through intradermal injection. The effect of hydrophobic forces on the rheology of concentrated dispersions of collagen fibers was studied by dynamic rheological measurements…
Abstract To determine the structure‐transport properties relations, we synthetized segmented polyether polyurethane with increasing rigidity. The formulation is based on poly(tetramethylene oxide diol) (PTMO) of different molecular weights, diphenylmethane aiisocyanate (MDI), and butanediol (BD). The synthesis is effe…
Abstract A thin membrane of bacterial cellulose (BC) obtained from Acetobacter culture was tested for its performance as a dialysis membrane in aqueous systems. The BC membrane showed superior mechanical strength to that of a dialysis‐grade regenerated cellulose membrane, allowing the use of a thinner membrane than th…
Experiments were performed on amorphous silica at temperatures of 1000°–2850°C and pressures of 9–14 GPa using a 2000‐t uniaxial split‐sphere multianvil apparatus (USSA‐2000). The melting curve of coesite was extended from 8 to 13.7 GPa, and the melting temperatures indicate a slope that is almost independent of press…
We investigate statistical-mechanical models on aperiodic structures ( e.g. quasi-periodic, random, self-similar). We derive a condition for the relevance of any kind of aperiodicity near a continuous phase transition, in the spirit of the Harris criterion. This explains why crystals and quasi-crystals exhibit the sam…
A variety of magnetic phase transitions have been observed for all the RFe 10 Mo 2 compounds from AC and DC magnetic measurements in the temperature range between 4.2 and 300 K. The alloys with R = Nd, Tb and Dy exhibit spin reorientation transitions and with R = Ho, Er and Tm some unidentified magnetic phase transiti…
We report visible light emission from porous structures formed in bulk and thin-film polycrystalline silicon materials by anodic etching in an HF:ethanol solution. Our results indicate photoluminescence (PL) peaks at wavelengths between 650 and 655 nm and with intensities comparable to those typically obtained from po…
An electrochemical technique is proposed to form a solid-state electrical contact of porous Si (PS) electroluminescence (EL) diodes. The PS layers were created by anodizing nondegenerate p-type single-crystal Si wafers in an HF solution, and then electrochemically polymerizing semitransparent conducting polypyrrole fi…
Pressure-induced structural transformation in ${\mathrm{SiO}}_{2}$ glass is investigated with molecular dynamics. At high densities, the height of the first sharp diffraction peak is considerably diminished, its position changes from 1.6 to 2.2 A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$, and a new peak appears at 2…
Here we demonstrate the first evidence that phase separation in polymer solutions could be essentially different from that in binary liquid systems. This difference is likely to originate from the strong asymmetry in molecular dynamics between the two separated phases. When the rheological time of the polymer-rich pha…
Abstract The in situ epoxidation of natural rubber latex was successfully performed in chain‐scissoring conditions. The chain‐scissoring process could be carried out simultaneously or successively to the epoxidation, to a determined extent. The rate and the degree of epoxidation depend on temperature, pH, and H 2 O 2…
He growth during an experiment were adequate except near the triple point.
Abstract This paper presents the influence of glass fibres on crystallization kinetics and on matrix morphology for poly(ethylene terephthalate) (PET)/glass fibre composites. The following parameters are also considered: fusion‐crystallization conditions, thermal stability and the addition of nucleating agents in the…
Composites combine the properties of two or more components. Conceptual tools are developed which guide the selection of components for making composites which maximise one or more aspect of thermo-mechanical performance.
The results reported indicate that the properties of polyurethanes elastomers can be tailored to serve a wide variety of applications, for low temperature uses as well. The glass transition temperatures of the soft segments (T gs ) which control the low temperature properties of polyurethane elastomers, ranged from -7…
A general model and analytical results have been derived to obtain laser-induced temperature rise in substrates with periodic multilayer structures. The substrate can be equivalent to a homogeneous substrate with anisotropic thermal conductivity, if the dimension of the periodic structure is much smaller than the lase…