Materials Literature
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Initial magnetization and demagnetization data are reported for three forms of rapidly solidified Nd-Fe-B permanent magnet materials: melt-spun ribbons, hot-pressed magnets, and die upset magnets. In all three materials, the results are consistent with domain-wall pinning at Nd2Fe14B grain boundaries as the coercivity…
Simultaneous measurements of electrical conductivity \ensuremath{\sigma} and thermoelectric power Q were performed on a single crystal of ${\mathrm{Ba}}_{0.03}$${\mathrm{Sr}}_{0.97}$${\mathrm{TiO}}_{3}$ over an extensive range of temperature (500--1100?deC) and oxygen partial pressure (${10}^{\mathrm{\ensuremath{-}}18…
We present here a complete set of experimental results, obtained by electron paramagnetic resonance (EPR) and deep-level transient spectroscopy (DLTS), on the so-called EL2 defect in GaAs. It is obtained on semi-insulating materials and specially doped materials grown as semi-insulating ones, which have been submitted…
Unmixing kinetics of quenched critical polymer mixture of polystyrene and poly(vinyl methyl ether) was investigated by time-resolved light scattering technique. In the late stage of spinodal decomposition τ>60, τ being a reduced time, a simple dynamic scaling law was found on the scattering function I(q,t); I(q…
Heterogeneous catalysis in the low-pressure (5 mbar) plasma phase is shown to result from mass and energy exchanges between the plasma and the solid surface. Perturbation of the plasma medium by the solid is interpreted as a catalytic action to the extent that it leads to an increase of chemical reactivity of the syst…
Organic single crystals provide an ideal model for studying the factors that influence chemical processes in structured media. Reaction trajectories are well defined and reveal the influence of spontaneous mechanical stresses equivalent to tens of thousands of atmospheres. Analysis of molecular and crystal structures…
In an axisymmetric approximation the author demonstrates a parity breaking transition to a twisted configuration in tangentially anchored nematic liquid crystal droplets. The twisted phase occurs when K 11 >or=K 22 +0.431K 33 . In a magnetic field there is another transition corresponding to the droplet axis changing…
A mean-field theory is presented for the coarsening of a two-dimensional soap-film network. This theory explains (1) the correlation between area and number of sides of the cells, and (2) the anomalous absence of dynamical scaling laws, which is shown to have its origin in the topological constraint of a space-filling…
A technique of high voltage electron beam lithography and BCl3/Ar reactive ion etching for laterally patterning GaAs/Al0.3Ga0.7As multiple quantum wells is described. The resulting structures were analyzed using scanning electron microscopy and a novel reflection electron microscopy technique, and their geometries are…
Martensitic transformations are shown to be driven by the interplay between two fluctuating strain components. No soft mode is needed, but a central peak occurs representing the dynamics of strain clusters. A two-dimensional magnetic-analog model with the martensitic-transition symmetry is constructed and analyzed by…
Dynamic coarsening of crystal surfaces by formation of macrosteps is explained by an improved model for impurity absorption. It is related to interface propagation in random media. Some unusual recursive equations are encountered. The model is analyzed by various methods and exhibits some universal features. We find c…
Abstract The phase behavior of binary mixtures of copolymers containing varying amounts of styrene and acrylonitrile (SAN) with a large range of aliphatic polyesters was examined. Miscibility was observed over a limited range of AN contents of the SANs, for each polyester, while similarly for each SAN, miscibility was…
Abstract The dynamic mechanical properties of thermoplastic elastomers from polypropylene natural rubber blends have been evaluated with special reference to the effect of blend ratio and extent of dynamic crosslinking of the elastomer phase. The effects of HAF black and silica fillers have also been studied. It has b…
Abstract Ultrahigh molecular weight polyethylene (UHMWPE) was mechanically mixed with conventional polyethylenes (LLDPE, HDPE, and LLDPE) using an internal mixer. Rheological studies of these blends suggest that UHMWPE seems to be miscible with LLDPE, HDPE, and LDPE in the melt state. Yield characteristics are observe…
Abstract The phase behavior of blends of various polymethacrylates with poly(epichlorohydrin) (PECH); poly(ethylene oxide) (PEO); and a copolymer of epichlorohydrin and ethylene oxide [P(ECH/EO)], was examined using differential scanning calorimetery (DSC), dynamic mechanical properties, and optical indications of pha…
Abstract The kinetics of solid state polymerization of poly(ethylene terephthalate) (PET) have been investigated at a variety of conditions. Equations have been developed to describe the relationships of time, temperature, and final molecular weight for PET precursors prepared from specified catalyst and monomer syste…
The attenuation of far-infrared (λ=0.119 mm) surface plasmons has been measured as a function of the thickness of a silicon overlayer on top of silver. Good agreement with theory was obtained indicating that the Drüde model for the dielectric constant of silver is valid out to these wavelengths.
Energetic ion beam irradiation of diamondlike carbon thin films induces a decrease of 4–5 orders of magnitude in the resistivity of the films from their as-grown value of 107 Ω cm. The initial decrease in resistivity with increasing ion dose is due to the loss of hydrogen from the films with a concomitant decrease in…
Gold micropatterns have been generated by the laser photolysis of dimethylgold (III) acetylacetonate, Me2Au(acac), in the vapor phase. Linewidths as fine as 2 μm were readily obtained utilizing a simple optical projection system comprised of a 4× projection lens, a lithographic photomask, and the UV output from an exc…
The first solid-state field-effect transistor has been fabricated utilizing a film of an organic macromolecule, polythiophene, as a semiconductor. The device characteristics have been optimized by controlling the doping levels of the polymer. The device is a normally off type and the source (drain) current can be modu…