Materials Literature
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Incompatible polymer blends between polyamide-6 (PA6) and poly(phenylene oxide) (PPO) have been compatibilized in situ by the styrene-glycidyl methacrylate (SG) reactive copolymers. The epoxy functional groups in SG copolymers can react with the PA6 amine and carboxylic endgroups at interface to form various SG-g-PA6…
Four types chitosan-based hydrogels have been prepared: cross-linked chitosan (cr-CS), cross-linked chitosan interpenetrating polyether polymer network (cr-CS/PE semi-IPN), cocross-linked chitosan and gelatin hybrid polymer network (CS/Gel HPN), and Chitosan/Pectin (CS/Ptn) ionic complex hydrogels. Water was used as a…
In this article we present overall crystallization characteristics of five polycaprolactone samples with mean molecular weights ranging from 50,000 to 400,000. The crystallization temperatures and heats of crystallization are determined as a function of mean molecular weight as well as for cooling rates in the range 0…
A new approach, plasma-induced graft polymerization of poly(ethylene glycol) methacrylate (PEGMA), was used to introduce PEG graft chains with hydroxyl end groups onto a polyurethane (Tecoflex) surface. After argon plasma treatment and subsequent exposure to air, graft polymerization onto Tecoflex films was allowed to…
We develop a model to study the thermal expansion of surfaces, wherein phonon frequencies are obtained from ab initio total energy calculations. Anharmonic effects are treated exactly in the direction normal to the surface, and within a quasiharmonic approximation in the plane of the surface. We apply this model to th…
LEED experiments show that Li adsorbed at Cu(100) surfaces at room temperature induces a (2x1) missing row substrate reconstruction while adsorption at lower temperatures, T=180 K, results in an unreconstructed Cu(100)+c(2x2)--Li overlayer structure. Substrate reconstruction has not been observed for Na nor for K adso…
Competition between conductive cooling and advective heating occurs whenever hot fluid invades a cold environment. Here the solidification of hot viscous flow driven by a fixed pressure drop through an initially planar or cylindrical channel embedded in a cold rigid solid is analysed. At early times, or far from the c…
The interaction of hydrogen with many transition metal surfaces is characterized by a coexistence of activated with non-activated paths to adsorption with a broad distribution of barrier heights. By performing six-dimensional quantum dynamical and classical molecular dynamics calculations using the same potential ener…
Prediction criteria for surface reconstructions are discussed, with reference to ab initio calculations of the (110)-$1\times 2$ missing-row and (100)-$5\times 1$ quasi-hexagonal reconstructions of Ir and Rh.
Paths of tetragonal states between two phases of a material, such as bcc and fcc, are called Bain paths. Two simple Bain paths can be defined in terms of special imposed stresses, one of which applies directly to strained epitaxial films. Each path goes far into the range of nonlinear elasticity and reaches a range of…
We have calculated formation energies and position of the defect levels for all native defects and for a variety of donor and acceptor impurities employing first-principles total-energy calculations. An analysis of the numerical results gives direct insight into defect concentrations and impurity solubility with respe…
The diffusivity of Ga and Al adatoms on the (2x4) reconstructed GaAs(001) surface are evaluated using detailed ab initio total energy calculations of the potential energy surface together with transition state theory. A strong diffusion anisotropy is found, with the direction of fastest diffusion being parallel to the…
We present a method for the controlled fabrication of stable nanostructures under ambient conditions. The surfaces under consideration, WSe2, are imaged by an atomic force microscope. By applying a voltage between the tip and the sample, we can control an etching process at the surface: different voltage thresholds fo…
A substantial difference in the angular distributions of $2p$ photoelectrons from polarized oxygen atoms was found for two antiparallel atomic polarizations. This magnetic dichroism was studied as a function of photon energy from 25 to 52 eV. Our method extends traditional photoelectron angular distribution measuremen…
We report an absolute measurement of the tensor analyzing powers ${T}_{20}$ and ${T}_{22}$ in elastic electron-deuteron scattering at a momentum transfer of $1.6{\mathrm{fm}}^{\ensuremath{-}1}$. The novel approach of this measurement is the use of a tensor polarized ${}^{2}\mathrm{H}$ target internal to an electron st…
A simple fabrication method is described to produce reliable and robust (self-repairing) field emission sources from randomly aligned carbon nanotubes. The sources display stable and reproducible current–voltage characteristics with sharp turn on near 100 V and emission currents up to 400 mA/cm2 at 200 V. Two successf…
The vibrational properties of carbon monoxide adsorbed to the copper (100) surface are explored within density functional theory. Atoms of the substrate and adsorbate are treated on an equal footing in order to examine the effect of substrate--adsorbate coupling. This coupling is found to have a significant effect on…
Strains of nearly 0.2% have been induced along [001] in unstressed crystals of Ni2MnGa with magnetic fields of 8 kOe applied at 265 K. These stains are associated with the superelastic motion of twin boundaries in the martensitic phase that is stable below about 274 K.
It is shown in this paper that the wetting behavior of n-alkanes on a water surface can be predicted using the wetting theory of Cahn, together with experimental results for n-alkane vapor adsorption on water which are readily available in the literature. The evolution of the wetting behavior with the carbon number of…
Structural relaxation in viscous glycerol has been followed from 5.9 ps to 3.7 ns by coherent neutron scattering around the structure factor maximum. In a 100 K interval, the line shape of the decay function shows no significant temperature dependence; the mean relaxation time scales accurately with viscosity. Interpa…