Materials Literature
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A study of the mechanical properties in an accelerated service-related environment of recycled glass-fiber-reinforced polyamide 66 is reported. Material reinforced with 30 wt % of short fibers was reground and remolded up to seven times. Thermal aging in air at 140°C for up to 3000 h and coolant aging at 110°C for up…
Six kinds of regioselectively substituted cellulose heteroesters (cellulose propanoate diacetate, cellulose butanoate diacetate, cellulose acetate dipropanoate, cellulose butanoate dipropanoate, cellulose acetate dibutanoate, and cellulose propanoate dibutanoate) and three kinds of cellulose triesters (cellulose triac…
The reaction of carboxylic acid anhydride with poly(vinyl alcohol) (PVA) leads to vinyl alcohol—vinyl ester copolymers which contain carboxylic acid groups. Esterification enables degrees of modification to be reached which depend on the chemical structure of the anhydride introduced and the ratio of the reagents in t…
Reactions of laser-ablated Cr atoms with O2 gave a very strong, sharp 965.4 cm−1 band and weak, sharp 1869.7, 984.3, 914.4, 846.3, 716.2, and 643.1 cm−1 bands. The 1869.7, 965.4, and 914.4 cm−1 bands track together on annealing, show 52Cr, 53Cr, 54Cr isotopic splittings appropriate for a single Cr atom and triplets wi…
This article addresses the effect of thermal aging on unreinforced and glass-reinforced recycled polyamide 66. As an accelerated test, injection-molded test bars were aged at 110, 140, and 170°C for up to 4000 h in air to simulate service life. FTIR spectroscopy demonstrated that the oxidative degradation primarily oc…
We have found that the chemistries of inner and external coagulants, gelation bath temperature, and air gap distance have profound effects on 6FDA-polyimde hollow-fiber morphology and performance. This 6FDA-polyimide is made of 50 mol % 2,2′-bis(3,4′-dicarboxyphenyl) hexafluoro propane dianhydride (6FDA) and 50 mol %…
Single - molecule fluorescence spectroscopy of a multichromophoric conjugated polymer (molecular weight ∼20,000) revealed surprising single-step photobleaching kinetics and acute jumps in fluorescence intensity. These jumps were shown not to result from spectral diffusion and were attributed to fluctuations in the qua…
We present a new integral equation formulation of the polarizable continuum model (PCM) which allows one to treat in a single approach dielectrics of different nature: standard isotropic liquids, intrinsically anisotropic medialike liquid crystals and solid matrices, or ionic solutions. The present work shows that int…
Nucleation and its mechanism of diamond on titanium substrates under very low pressure was studied using hot-filament chemical vapor deposition. Very high nucleation rates and densities (10^8-10^{10} cm^{-2}) were obtained under 1 torr, which were 1-3 orders of magnitude higher than the counterpart (10^7 cm^{-2}) unde…
Absorption and fluorescence spectra of Nd3 +were measured in potassium tantalum gallate, lead bismuth gallate (PBG), fluorozirconate (ZBLAN), and Ge-Ga-S glasses. A Judd -Ofelt analysis was performed to determine the spontaneous emission probability and stimulated emission cross section of the4 F3/2 ?4 I11/2 transitio…
Diamond nucleation under very low pressure (0.1-1.0 torr) was obtained at very high nucleation densities and very rapid rates using hot-filament chemical vapor deposition (HFCVD). The density on mirror-polished silicon was as high as 10^10 - 10^11 cm^{-2}, equivalent to the highest density in a microwave-plasma CVD sy…
The electrical resistivity of liquid hydrogen has been measured at the high dynamic pressures, densities and temperatures that can be achieved with a reverberating shock wave. The resulting data are most naturally interpreted in terms of a continuous transition from a semiconducting to a metallic, largely diatomic flu…
The first non-empirical computation of lattice thermal conductivity has been performed for MgO using molecular dynamics (MD), a non-empirical ionic model (the Variationally Induced Breathing (VIB) model), and Green-Kubo theory. The computation is first-principles in the sense that no parameters are fit to experiment.…
The liquid - glass transition in n-propanol has been investigated in detail by measuring the pressure dependence of the Brillouin scattering spectra. Using a home-made Brillouin microscope equipped with a diamond anvil cell, backward-geometry spectra were measured as a function of pressure from 1 atm to 8.3 GPa. As th…
To obtain physical insight into the slowing of the molecular dynamics when a macromolecule grows as a result of polymerization, (i) the dielectric relaxation spectra, and (ii) the heat evolved during the growth of a linear chain structure by means of the reaction of diepoxide with a monoamine have been measured simult…
Thermal stability (up to 350°C) is one of the characteristics of the supramolecular mesogenic polyamide formed by self-assembly during the complexation between a phyenylbezoic acid and a nylon containing pyridyl units in its backbone. The probable structure of the hydrogen-bonded complex is shown schematically on the…
Epitaxial ferromagnetic manganite films have been sputtered on bicrystal substrates. Their magnetoresistance was measured as a function of magnetic field and temperature. The grain boundary magnetoresistance at low temperature is separated from the intrinsic magnetoresistance near the Curie temperature. The grain boun…
The spectral properties of Pr 3+ doped BaInGaGeSe chalcogenide glasses are reported. Absorption spectra, emission spectra, and lifetimes of the lower lying manifolds have been measured. Radiative transition rates are calculated and compared with measured experimental lifetimes. The strong mid-IR emission and spectral…
The molecular geometry is mirrored in the macroscopically ordered patterns found in a series of stiff, phenylacetylene dendrimers 1. These compounds form hexagonal columnar liquid crystalline phase with snowflake-like morphologies.
Promising as a chelating agent and as a photosensitizer hemiporphycene is the third porphyrin isomer after porphycene and corrphycene with a central N4 coordination sphere. The stable octaethyl derivative of hemiporphycene 1 was obtained by the combination of a McMurry reaction a reductive CC cleavage from a bis(tetra…