Materials Literature
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We have carried out a study of the photoluminescence properties of silicon-rich silica. A series of films grown using plasma enhanced chemical vapor deposition over a range of growth conditions were annealed under argon at selected temperatures. Photoluminescence spectra were measured for each film at room temperature…
Differential scanning calorimetry, Raman scattering, optical absorption, and upconversion of infrared to green luminescence have been studied for Er3+-doped lead-germanate glass 55GeO2⋅20PbO⋅10BaO⋅10ZnO⋅5K2O (GPBZK) and lead-tellurium-germanate glass 30GeO2⋅30PbO⋅30TeO2⋅10CaO (GPTC). Judd–Ofelt intensity parameters of…
The luminescence mechanism in a-C:H is described as a modification of the band tail luminescence in hydrogenated amorphous Si. The tail states of a-C:H are formed from clusters of ${\mathit{sp}}^{2}$ sites and luminescence occurs by recombination within each cluster. The paramagnetic defects are confirmed as the nonra…
β-Ga2O3 contains two crystallographically different Ga atoms in the asymmetric unit, one with tetrahedral and the other with octahedral coordination geometry. The Ga-O distances are in the range 1.833 (1)–1.863 (2) Å within the tetrahedra, but are longer within the octahedra [1.935 (2)–2.074 (1) Å]. The O atoms have a…
We use photoluminescence excitation and fluorescence line narrowing spectroscopies to examine structure observed in the band-edge absorption feature of CdSe quantum dots. We study eight samples ranging from \ensuremath{\sim}15 to \ensuremath{\sim}50 \AA{} in radius to probe the size dependence of this structure. We co…
We use photoluminescence excitation to study the electronic spectrum of CdSe quantum dots ranging from \ensuremath{\sim}12 to \ensuremath{\sim}53 \AA{} in radius. We follow the size evolution of ten quantum dot absorption features. Comparison of the spectra with theoretical predictions allows us to confidently assign…
γ-Irradiation of poly(tetrafluoroethylene) (PTFE) in the presence of air results in degradation of polymer chains by insertion of oxygen. At first, in the low-dose range below 400 kGy, a rise in crystallinity can be observed due to main chain scission in the amorphous part of the macromolecules. Dose increase up to ap…
The effects of silica, mullite, α-alumina and γ on the nonoxidative thermal degradation of poly(vinyl butyral) are described. To varying degrees, all of the inorganic oxides catalyzed reactions that produced butanal. Other significant products included: water, butenal, acetic acid, and alkyl aromatics. Two distinct ev…
A comprehensive kinetic model for a semibatch direct esterification reactor has been developed. The solid-liquid equilibirium of terephthalic acid was considered in the modeling. Effects of the monomer feed ratio, reaction temperatures, and oligomer addition on the conversion, degree of polymerization, and the formati…
An attempt was made to modify the properties of poly(butylene terephthalate) (PBT) by blending it with polyamide-6 (PA-6). Since PBT and PA-6 are incompatible, epoxy resin was used as a compatibilizer to form an alloy. Alloys of PBT and PA-6 with varying amounts (0–12%) of epoxy resin E-44 were prepared by melt blendi…
To improve the physical properties of starch-filled polyolefin, starch was modified into more hydrophobic material by the introduction of cholesterol unit, and the different starch-compositioned high-density polyethlene (HDPE) films were prepared with addition of either native starch or modified starch to compare thei…
Silk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gains (300%) were obtained with both monomers, the weight gain being linearly related to the amount of monomer contained in the reaction sys…
The thermal behavior in argon of homogeneously synthesized cellulose p-toluenesulfonates (tosylates) with a degree of substitution (DS) ranging from 0.4 to 2.3 was studied by means of thermogravimetry and derivative thermogravimetry from ambient temperature up to 500°C. For comparison, the thermal behavior of the star…
Cellulosic absorbents for water were synthesized by photografting (λ > 300 nm) acrylic acid (AA) onto fiberous carboxymethyl cellulose (CMC, degree of substitution [DS] = 0.1–0.4) at 30°C in the presence of N,N′-methylenebisacrylamide as a crosslinker. The CMC sample was pretreated with hydrogen peroxide in the presen…
Stable, thick poly(dimethylsiloxane) (PDMS) coatings are formed on iron(III) and aluminum oxide and calcium carbonate particles by impregnating the particles with dimethylsilicone oil and heating at 250–280°C. These coatings are strongly resistant to solvent extraction and to exposure in a water-saturated atmosphere.…
The effect of a fine powder of Y2O3, Nd2O2, and Ho2O3, on the crystal structure of isotactic polypropylene (iPP) was studied with WAXD and DSC techniques. The results showed that the addition of the three rare earth oxides (REOs) can increase the crystallite size of the α-form crystal and the degree of crystallinity o…
The compounding of calcium carbonate filled polypropylene (PP) is discussed with reference to a single-screw extruder and variants of mixing sections. The mixing section on the screw is exchangeable, and two dispersive mixing elements, namely the Zorro and the Maddock elements, were used. The calcium carbonate was sur…
Water-absorbing polyurethane foams were prepared from liquefied starch polyols and diphenylmathane diisocyanate (MDI) by using a cell-opening foaming surfactant. The liquefied starch polyols were obtained by the liquefactions of starch in the presence of polyethylene glycol-dominant reaction reagents by using sulfuric…
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characterized by x-ray powder diffraction is a layered compound isostructural with : a = 3.80 Å; c = 22.19 Å; space group . The magnetic properties are similar to those of but with an even more pronounced difference between the intralayer and interlayer exchange interactions of localized moments. The magnetic suscepti…