Materials Literature
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SUMMARY A unified thermodynamic constitutive model for Shape Memory Alloy (SMA) materials, based on the thermodynamic framework proposed by Boyd and Lagoudas,1is presented in this paper. The specific selections for the form of Gibbs free energy associated with the martensitic volume fraction are identified for several…
We have investigated liquid-liquid and solid-liquid phase separation of aqueous solutions of lysozyme. We have determined experimentally how the phase transition temperatures depend on protein concentration and the ionic composition of the solution. For a wide range of solution conditions, we find that the cloud-point…
Polyaromatic hydrocarbons are model compounds for graphite and have interesting electronic and optoelectronic properties. The synthesis and preliminary characterization of hexaalkyl‐substituted hexa‐ peri ‐hexabenzocoronenes (see figure) are described. It is shown that they exhibit hexagonal columnar mesophases with r…
Neutron scattering studies on a single crystal of the highly correlated electron system, ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}$ with $x\ensuremath{\approx}0.3$, have been carried out elucidating both the spin and lattice dynamics of this metallic ferromagnet. We report a large m…
The electrical properties of ceramic BaTiO 3 were investigated by ac impedance spectroscopy over the ranges 25°‐330°C and 0.03 Hz‐1 MHz. Results are compared with those obtained from fixed‐frequency measurements, at 1 kHz and 100 kHz. Fixed‐frequency Curie‐Weiss plots show deviations from linearity at temperatures wel…
We show by using formal asymptotics that the zero level set of the solution to the Cahn–Hilliard equation with a concentration dependent mobility approximates to lowest order in ɛ. an interface evolving according to the geometric motion, (where V is the normal velocity, Δ 8 is the surface Laplacian and κ is the mean c…
“Ultra‐monomolecular” films of block copolymers , i.e., films whose surface concentration is so low that the substrate cannot be covered homogeneously without affecting the structure of the macromolecules very strongly, have been studied using tapping‐ and friction‐mode SFM. Two‐dimensional phase separation yielding a…
The evolution of hydrogen and oxygen was studied on diamond electrodes containing approximately 10 21 boron atom/cm 3 . Voltammetry showed a wide potential window [−1.25 to +2.3 V vs. standard hydrogen electrode (SHE)] without significant water decomposition. This window was much narrower for poor quality diamond film…
The pronounced increases in isothermal compressibility, isobaric heat capacity, and in the magnitude of the thermal expansion coefficient of liquid water upon supercooling have been interpreted either in terms of a continuous, retracing spinodal curve bounding the superheated, stretched, and supercooled states of liqu…
An investigation designed to display the intrinsic properties of perovskite manganites was accomplished by comparing the behavior of bulk samples with that of thin films. Epitaxial 1500 \AA{} films of perovskite ${\mathrm{La}}_{0.67}$${\mathrm{Ca}}_{0.33}$Mn${\mathrm{O}}_{3}$ and ${\mathrm{La}}_{0.67}$${\mathrm{Sr}}_{…
We develop a method which permits the analysis of problems requiring the simultaneous resolution of continuum and atomistic length scales-and associated deformation processes-in a unified manner. A finite element methodology furnishes a continuum statement of the problem of interest and provides the requisite multiple…
The main component of this program is a simultaneous representation of the unit cell and the calculated powder pattern. It allows the manipulation of the crystal structure by moving selected atoms of the asymmetric unit. The resulting powder pattern can be directly compared to experimental data in order to obtain reli…
Shape memory alloy has been considered as an actuator for applications that require low bandwidth, high force, and large displacement. Two factors have limited the usefulness of such actuators: hysteresis and bandwidth limitation. This paper considers the hysteresis phenomenon from a control point of view. We first co…
The tensile properties of polystyrene reinforced with short sisal fiber and benzoylated sisal fiber were studied. The influence of fiber length, fiber content, fiber orientation, and ben-zoylation of the fiber on the tensile properties of the composite were evaluated. The ben-zoylation of the fiber improves the adhesi…
A poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) (80/20 w/w) polymer blend was studied by mechanical spectroscopy. Two relaxations can be distinguished: in the glassy state, a very large secondary relaxation in the range of 100 K to 325 K which results from the combination of secondary relaxations of PVC…
The published data on phase equilibria in the M–X–X' and M–Al–X ternary systems (M is a Group III-VIII transition metal, X, X' are B, C, N, Si) are surveyed. These systems provide a basis for the directed search for oxygen-free ceramic materials for various purposes. The phase diagrams for the ternary systems are pres…
Past work has shown that addition of high-density polyethylene (HDPE) to polypropylene (PP) resulted in a significant reduction in the elongation at break and in the gate-region impact strength of injection molded articles. In this study, we report on the compatibilization of these blends with ethylene/propylene/diene…
Fire-retardant polypropylene (PP) composites were prepared by combining this polymer with uncoated and surface treated forms of magnesium hydroxide filler and various elastomeric modifiers, with and without maleic anhydride functionalization. Mechanical properties of binary and ternary phase compositions differed sign…
Deformation and fracture processes of two types of modified polypropylenes (PPs) were investigated in situ by high voltage electron microscopy (HVEM, 1 MV) and scanning electron microscopy (SEM). One type of PP modified with ethylene–propylene block co-polymer rubber (EPR) showed a variation in particle size and inter…
Some materials exhibit thermoelectricity, a phenomenon not only useful for heating and cooling applications but also for power generation. In his Perspective, Tritt describes results reported by Sales et al . ( p. 1325 ) on a class of thermoelectrics called skutterudites. These compounds are promising higher performan…