Materials Literature
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A new method was developed for binding poly-(ethylene oxide) (PEO) to polymer surfaces that involves the use of electron beam irradiation in two steps. In the first, methacrylic acid was grafted and polymerized to a polymer surface, changing it from hydrophobic to hydrophilic. Exposure of this surface to aqueous PEO s…
The metallic state of conducting polymers is a subject of continued interest and controversy. By means of a series of high-precision reflectance measurements on PF6-doped polypyrrole (PPy-PF6), the processes occurring as the system passes through the metal–insulator (M–I) transition are clarified. Evidence is presente…
We show via calculation and experiment that a recently observed angular magnetoresistance effect in low-dimensional conductors can be explained by ``effective electrons,'' which dominate the conductivity for magnetic-field orientations near inflection points on a warped Fermi surface. Closed orbits, which form in cert…
Novel poly(oxyethylene)/poly(caprolactone) POE/PCL copolymers were synthesized by step growth polymerization of poly(ε-caprolactone) diols and poly(ethylene glycol) diacids using dicyclohexylcarbodiimide as coupling agent. The reaction was performed at room temperature and yielded multiblock copolymers with predetermi…
Two samples with the same nominal composition ${\mathrm{La}}_{0.83}{\mathrm{Sr}}_{0.17}{\mathrm{Mn}}_{0.98}^{57}{\mathrm{Fe}}_{0.02}{\mathrm{O}}_{3}$ were prepared in air and argon. Thermograviametric, structural, resistive, and magnetic measurements show that the air-made sample has slightly higher ${\mathrm{Mn}}^{4+…
We explore a simple model for supercooled liquids in which reorientational and translational motions are inherently coupled to the structural relaxation. Several controversial aspects of the molecular motion in glass-forming materials are naturally resolved within the framework of our model. These include the geometry…
We report on GaAs/MCM-41 heterostructures synthesized by deposition of GaAs into the channels of MCM-41 using metalloorganic chemical vapor deposition. MCM-41 consists of an ordered array of silica tubules comprising pores with uniform and controllable diameter in the nanometer range. The GaAs/MCM-41 heterostructures…
Recent work has shown that metal quantum dots can be treated as “artificial atoms” and crystallized into “artificial solids” that have electronic properties that can be tuned by controlling interparticle coupling through the application of pressure. The interactions between the nanocrystals in such artificial solids a…
Surface PD (partial discharge) on an insulator from a TJ (triple junction) are reduced by recessing the TJ at the HV electrode. The insulators have an inner electrode connected to the ground potential. PD pulses whose magnitude is >10 pC are measured. The applied HV (50 Hz) is 1 to 1.5/spl times/ higher than that at t…
Starting from 5-(4-hydroxyphenyl)-10,15,20-tris(4-methylphenyl)porphyrin (2a), the new bis(porphyrinyloxy)alkanes 4a and 4d were synthesized by ether formation with the α,ω-dibromoalkanes Br(CH2)nBr (n = 8, 11; 3a, 3d). 4a was obtained by a two-step reaction with the 5-[4-(8-bromooctyloxy)phenyl]-10,15,20-tris(4-methy…
Abstract Phase transformation of high silica BEA to OU-1 and MTW was demonstrated for the first time. Zeolite OU-1, an analogous material to SSZ-31 and NCL-1, was synthesized using tetraethylammonium hydroxide (TEAOH) as a structure directing agent. The influence of Na and Al ions on stabilization of BEA phase during…
C–Gd2S3 and C–Tb2S3: Synthesis and X-Ray Structure Analysis of Single Crystals Pale yellow, bead-shaped single crystals of C-type Gd2S3 (a = 838.47(9) pm) and Tb2S3 (a = 835.23(9) pm) are obtained upon the oxidation of the respective rare-earth metal (M = Gd and Tb) with sulfur (molar ratio 2 : 3) in evacuated silica…
This paper presents the results of a continuing investigation into effect of water on water absorption and density of crosslinked polyethylene (XLPE). The experimental set up was made for the following XLPE cable insulations: steam and dry cured with water tree retardant crosslinked polyethylene (TR-XLPE) and without…
The residual ac breakdown voltage decreased to about half of the initial breakdown voltage after 3 months of accelerated aging test under immersion. This decrease was found to be caused mainly by a trace amount of moisture existing in the insulation. However, the breakdown voltage did not further decrease with increas…
Chromium nitride (CrN) coatings have been deposited on polished steel substrates by a plasma-beam sputtering technique in a Sputron apparatus (Balzers A. G.) at 200 °C. A thin intermediate layer of Cr (0.08 μm) was deposited between the substrate and the 2.8 μm thick CrN coating. The average roughness, Ra, of the subs…
Abstract Pb monoborate hydrate, Pb 5 B 3 O 8 (OH) 3 H 2 O, was synthesized in the hydrothermal system PbCO 3 –Li 2 B 4 O 7 –H 2 O ( T = 543 K, p = 100 bar; PbCO 3 /Li 2 B 4 O 7 = 0.25–0.5; 10–14 days). The hexagonal structure was established from X-ray single crystal diffraction, λ (Mo K α ) = 0.71073 Å; space group P…
The paper deals with gel permeation chromatography (GPC) monitoring of the behaviour of PET (polyethylene terephthalate) after repeated extrusions. Virgin PET was submitted to three successive extrusion/drying cycles and then the samples were swelled with hexafluoroisopropanol and treated with chloroform. GPC analysis…
Abstract In this paper, we review some of the significant synthesis approaches that we and others have evaluated for producing commercially viable water‐soluble biodegradable polymers. The goals set for these polymers, cost/performance equivalent with current non‐biodegradable polymers and complete biodegradation or a…
Ca (1+ x )/2 Sr (1+ x )/2 Zr 4 P 6−2 x Si 2 x O 24 ( x ≤ 0.37) compositions, which belong to the [NZP] family of low‐thermal‐expansion materials, were synthesized using the solid‐state reaction method. The lattice thermal expansion of members of this system was determined up to 1000°C by high‐temperature X‐ray diffrac…
Abstract The objective of this research is to synthesize synthetic biodegradable polymers that would have biological functions similar to nitric oxide. Polyglycolide (PGA) was the synthetic biodegradable polymer and 4‐amino‐2,2,6,6‐tetramethylpiperidine‐1‐oxy (Tempamine) was chosen as the source of nitroxyl radicals.…