Materials Literature
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We present results of molecular dynamic simulations aimed at examining crack tip dislocation emission in fcc solids. The results are analyzed in terms of recent continuum formulations of this problem. In mode II, Au, Pd, and Pt displayed a new unanticipated mechanism of crack tip dislocation emission involving the cre…
The molecular mobility and hydration properties of model segmented polyurethanes from either poly(propylene glycol) (PPG) or poly(butylene adipate) (PBAD), both of molecular weight 2000 (soft segments), and three different diisocyanates (all-trans 4,4′-dicyclohexylmethane diisocyanate, 100% t,t HMDI; HMDI with 20% of…
Predictions from a recently developed mode coupling theory (MCT) are compared with experimental results for hard-sphere suspensions. A simple scaling of the MCT results leads to good agreement with the data. The scaled MCT predicts that for hard-sphere suspensions the zero-shear limiting viscosity obeys a generalized…
The effect of the matrix material on the magnetostriction of composites containing highly magnetostrictive particles has been studied. Experimental results showed that the elastic modulus of the matrix is an important factor determining the bulk magnetostriction of the composite. For a series of composites with the sa…
We have generated the thin-film ternary composition spread of (Ba1−x−ySrxCay)TiO3 on an equilateral-triangle-shaped LaAlO3 substrate. Compositional variation within the triangle was achieved by a precisely controlled shutter system inside a pulsed laser deposition chamber, which allows the deposition of precursors wit…
Polybutadienes (PBs) of narrow molecular weight distributions with high 1,4-microstructure were synthesized by sec-butyllithium-initiated, living polymerization. The shoulder-like anomalous behavior of the storage modulus G′(ω) in the terminal zone for PBs was studied using size exclusion chromatography (SEC) and rheo…
High-speed spinning of high molecular weight poly(ethylene terephthalate) (PET) having an intrinsic viscosity of 0.98 dL/g was performed at the take-up velocity range of 2.5–5.5 km/min. The structure of the as-spun filaments was analyzed by density, birefringence, WAXS, DSC, boiling water shrinkage, and tensile proper…
Low molecular-weight polylactic acid (PLA) was obtained by direct polycondensation of a mixture of 95% l and 5% d-lactic acid isomers, without catalyst, at 195°C. This polymer was used for the synthesis of microspheres by emulsion–solvent evaporation method. Gel Permeation Chromatography (GPC), X-ray Scattering (XRD),…
The quasicontinuum method is used to simulate three-dimensional Lomer-Cottrell junctions both in the absence and in the presence of an applied stress. The simulations show that this type of junction is destroyed by an unzipping mechanism in which the dislocations that form the junction are gradually pulled apart along…
The Stranski-Krastanov growth kinetics of undislocated (coherent) 3-dimensional islands is studied with a self-consistent mean field rate theory that takes account of elastic interactions between the islands. The latter are presumed to facilitate the detachment of atoms from the islands with a consequent decrease in t…
The results of electrical resistivity, heat capacity and magnetic susceptibility behavior of new class of alloys, Ce_{2-x}La_{x}CoSi_{3}, are reported. The x= 0.0 alloy is mixed valent and La substitution for Ce (x= 0.25) induces linear temperature dependence of resistivity at low temperatures, an observation of relev…
We report on systematic measurements of the distribution of normal forces exerted by granular material under uniaxial compression onto the interior surfaces of a confining vessel. Our experiments on three-dimensional, random packings of monodisperse glass beads show that this distribution is nearly uniform for forces…
The Hall effect in LuNi_2B_2C and YNi_2B_2C borocarbides has been investigated in normal and superconducting mixed states. The Hall resistivity rho_{xy} for both compounds is negative in the normal as well as in the mixed state and has no sign reversal below T_c typical for high-T_c superconductors. In the mixed state…
We report the observation of the pressure-induced high-spin to low-spin transition in FeS using new high-pressure synchrotron x-ray emission spectroscopy techniques. The transition is evidenced by the disappearance of the low-energy satellite in the Fe K$β$ emission spectrum of FeS. Moreover, the phase transition is r…
We present an analytical study of the spatial decay rate $γ$ of the one-particle density matrix $ρ(\vec r,\vec r')\sim\exp(-γ|\vec r-\vec r'|)$ for systems described by single particle orbitals in periodic potentials in arbitrary dimensions. This decay reflects electronic locality in condensed matter systems and is al…
Abstract A computer scaling study was conducted to predict the possibility of scale formation when seawater is injected into the northern Kuwaiti oilfields for reservoir pressure maintenance. Results indicated that the seawater is likely to be self-scaling with respect to calcium carbonate at reservoir conditions. The…
We consider the problem of a diblock copolymer thin film melt on a striped surface. The striped surface induces the lamellae to orient perpendicularly to the surface and align commensurate with the stripes at the bottom of the film. In all practical cases at the top of the thin film the free surface will prefer one bl…
The mode-coupling theory for the evolution of glassy dynamics in simple liquids yields correlation functions that, outside the transient regime, can be written as a superposition of relaxators with a broad distribution of relaxation rates. The known asymptotic laws for the dynamics near an ideal glass transition imply…
Heat-resistant flexible-film optical waveguides were fabricated from fluorinated polyimides. These waveguides operated in single mode and had low optical loss (0.3 dB/cm) at a wavelength of 1.3 microm for TE and TM polarizations. They also had good flexibility: The optical loss did not significantly change above a min…
Using rheometry and light scattering, we have studied the viscoelasticity of gels formed by the kinetically arrested phase separation in an emulsion−polymer mixture; to prevent the gels from collapsing under their own weight, we have used an isopycnic solvent. At constant osmotic pressure (set by the polymer concentra…