Materials Literature
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A behavioral model of magnetic materials is presented. This model takes into account both hysteresis and dynamic phenomena. It predicts B(H), /spl phi/(t) and d/spl phi/(t)/dt characteristics, and a few pieces of experimental data are needed to identify its parameters. In this paper, the authors propose to validate th…
Porphyrins with steric hindrance at the periphery are known to exhibit severely non-planar macrocycle conformations. Among other dodecasubstituted porphyrins, the title compound has been studied widely and shows a typical saddle-distorted macrocycle. The specific conformation of the porphyrin leads to the formation of…
A diffraction grating technology based upon volume-phase holograms shows promise of enhanced performance for many applications in astronomical spectroscopy over classical surface-relief grating technology. We present a discussion of the underlying physics of a volume-phase grating, give some theoretical performance ch…
A finite element, numerical model of a solid railway wheel was perfected permitting the simulation of a block braking operation. The analyses performed, backed by experimental tests, permitted the degree of variation in the residual stress state (induced by differential quenching heat treatment and successive temperin…
Hen egg white lysozyme was employed for studying aggregation and nucleation events induced by simple electrolytes such as NaCl while the process was monitored by time-resolved, small-angle static light scattering. The fractal dimension, the weight-average molecular weight, the mean radius of gyration and the homogenei…
Microbial corrosion scenarios based on the action of sulfate-reducing bacteria (SRB) under disbonded tape coatings on the outside of gas pipelines have been described previously. Secondary oxidation of these sites leads to formation of unique corrosion products. These have been associated with serious corrosion damage…
A concept is outlined to incorporate dislocation climb in a discrete three-dimensional model of dislocation dynamics. Each dislocation line consists of a sequence of interconnected piecewise straight segments which are embedded in a homogeneous linear elastic medium. The dynamics are described by solving Newton's equa…
The electrodynamic balance (EDB) is demonstrated to be useful for the in situ study of aqueous droplet solidification. We have used an EDB to study the solidification of solution droplets used for ceramic powder synthesis by spray pyrolysis. The mass change and the elastic light scattering of the drying 20 μm solution…
High-modulus and high-strength carbon fibers were submitted to oxidation plus sizing and grinding treatments. Subsequent changes at the fiber surfaces were studied by Raman spectrometry. X-ray diffractograms and Raman spectra of the fresh fibers were compared with those of other carbon materials with different graphit…
Sol–gel techniques have been used to produce various high temperature ceramic matrix composites including Ni/α-Al2O3, Fe/α-Al2O3, Ni/ZrO2, SiC(whisker)/α-Al2O3, and SiC(platelet)/α-Al2O3, as well as chemically modified versions of some of these systems. In all cases, the composites have displayed uniform microstructur…
The fine structure of Haslea ostrearia Simonsen, a diatom that is able to synthesize a blue pigment (marennine), is described. Ultrastructurally, this microalga has a typical naviculoid organization, but marked changes occur depending on the stage of cell blueing by accumulation of marennine. A comparison of the ultra…
ABSTRACT Surface topography and roughness of garlic and onion skins were studied by atomic force microscopy in order to estimate the surface area. Image‐processing and Arc/Info software were used to interpret the data. The calculated ratio between apparent and measured surfaces (roughness factor) deviated from 1.11 to…
Abstract The glass transition temperatures of PVC containing stearic acid derivatives as lubricants have been used to define two new parameters of lubrication: the saturation concentration and the efficiency constant . The saturation concentration represents the maximum amount of lubricant compatible with PVC in a spe…
Different transmission electron microscopy techniques have been compared for the detection and size measurements of ordered regions on a nanometer scale in a disordered matrix phase. As a model system, the perovskite lead magnesium niobate doped with varying amounts of La has been chosen for the present study. While s…
Methyl methacrylate (MMA) plasmas and plasma-polymerized methyl methacrylate (PPMMA) films were studied in situ with FTIR and FTIR/ATR (attenuated total reflection) in an r.f. capacitively coupled glow discharge. A statistically designed experiment was conducted by varying the r.f. power, process pressure, and MMA flo…
X-ray-scattering data from chiral smectic-$A$ liquid crystals under an applied electric field have been analyzed to investigate the layer-buckling instability. A quantitative description of the scattering data at all values of the field is obtained via calculation of the minimal-energy layer displacement profiles dete…
Abstract In situ silica reinforcement was applied to the acrylonitrile—butadiene rubber (NBR) vulcanizates. The amount of in situ silica introduced in the NBR vulcanizates was limited due to the high polarity of NBR. The presence of γ-mercaptopropyltrimethoxysilane (γ-MPS) in the NBR vulcanizate increased the conversi…
The first‐principles calculation of finite‐temperature phase stability and thermodynamic properties of multicomponent oxides presents a significant challenge. The time scale on which substitutional disorder occurs prevents the use of standard simulation methods, and a correct description of entropic effects requires t…
The Fe 2 O 3 particles with diameters of 3−5 nm were encapsulated between the core and the shell of polymer via emulsion polymerization into the heterostructured microspheres, which were observed through TEM images. The photovoltaic response of the composites, which was studied by the electric-field-induced surface-ph…
Ultradrawing of atactic poly(acrylonitrile) (PAN) was investigated for a Mv series, ranging 8.0 × 104–2.3 × 106. Samples for the draw were prepared from 0.5–30 wt % solutions of PAN in N,N′-dimethylformamide. The solutions were converted to a gel by quenching from 100 to 0°C. The dried gel films were initially drawn u…