Materials Literature
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We present a variational calculation of the envelope wave function of an exciton inside a cube. We show that all sixfold integrals can be reduced to threefold integrals with a change of variables which shortens tremendously the computer calculations. Then (i) we calculate numerically the Bohr radius, the correlation e…
In situ x-ray-diffraction studies of nanophase TiO2 during annealing reveal a strong angular-dependent decrease in diffuse background intensities and a corresponding increase in rutile and anatase phase peak intensities for samples annealed above 623 K. This behavior is consistent with the crystallization of an amorph…
Partial monolayers of uniform length alkyl chains [CH3(CH2)n–; n=10–21] bonded at constant coverage onto a disordered lattice of silanol groups on amorphous SiO2, exhibit a distinct change in surface wetting behavior for 14≤n≤17 which correlates closely with a significant shift in the average conformational ordering o…
Light-emitting porous silicon films have been obtained by anodic etching p-type Si samples in a HF-ethanol solution. Porous Si samples efficiently luminesce at room temperature in the visible region. A degradation of the luminescence intensity with time is observed. Micro-Raman spectroscopy of free-standing porous sil…
The structure and magnetic properties of nanocrystalline, two-phase Sm2Fe17Nx+α-Fe alloys prepared by mechanical alloying and heat treatment have been studied. Remanence enhancement and single-phase magnetic behavior were observed in isotropic powders crystallized at low temperatures (about 600 °C), while crystallizat…
Molecular dynamics simulation of a united-atom polyethylene model was performed to study the short time dynamics of polymer liquid and glass. Simulation runs lasting up to 5 ns were performed at ten temperatures above and below the estimated glass transition temperature. Quantities evaluated for the purpose of studyin…
Electron energy loss spectroscopy and high-resolution images of carbon nanotubes, obtained using a 2 nm probe and energy resolution of 0.5 eV, revealed a 15 eV surface plasmon for tubes containing \ensuremath{\le}12 cylindrical graphitic sheets. As the number of sheets increases further the 24 eV bulk plasmon quickly…
Abstract The dielectric properties of poly(vinyl‐chloride) (PVC) were investigated as a function of frequency and temperature. Attention was focused on the low frequency dielectric properties. Samples with different molar masses were studied. Two dipolar retardation processes were observed, one due to a local motion i…
Abstract The structural aspects of rigid suspension poly(vinyl chloride), PVC, have been investigated on the basis of two independent series of suspension PVC samples, polymerized at temperatures between 26 and 84°C. The reproducibility of the suspension polymerization process and the importance of the polymerization…
We present a systematic experimental investigation of the photoluminescence of heavily doped, compensated Si:P,B. The spectra broaden as the doping levels are increased, as expected. The spectral weights of the no-phonon peak and the phonon-assisted transitions vary with compensation and with excitation intensity. In…
Abstract Thermal diffusivity, heat capacity, and density of polyvinyl chloride/polycaprolactone (PVC/PCL) blends were measured by the laser flash method, DSC, and pycnometry, respectively. The thermal conductivity of the PVC/PCL blends was determined from the results. The miscibility of the blend and crystallinity of…
Molten Si was allowed to solidify isothermally at initial bulk undercoolings ΔT from 5.7 to 157 K. It was found that in addition to the 〈211〉 twin dendrites two novel dendrites were found: the 〈110〉 twin and the 〈100〉 twin free dendrite. The 〈110〉 twin dendrite has multiple twin planes, and the orientation of the twin…
Room-temperature luminescence observed in porous silicon has been attributed either to direct radiative recombination in nanometer-size silicon in the porous silicon network, or to chemical complexes of silicon, hydrogen, and/or oxygen. In this paper, we attempt to correlate results of infrared and photoluminescence s…
We present a theoretical study of the structural stability of ordered configurations of ${\mathrm{B}}_{\mathit{x}}$${\mathrm{C}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ solid solutions with the graphite structure. The calculations were carried out self-consistently using norm-conserving pseudopotentials in the local-den…
We have used neutron reflection and phase contrast microscopy to investigate the morphology and surface topology of thin films of nearly symmetric (f=0.55) and asymmetric (f=0.77), poly (ethylene–propylene)–poly (ethylethylene) (PEP–PEE) diblock copolymers (f being the PEP volume fraction) and have identified three im…
A deterministic global optimization algorithm is introduced for locating global minimum potential energy molecular conformations. The proposed branch and bound type algorithm attains finite ε-convergence to the global minimum through the successive refinement of converging lower and upper bounds on the solution. These…
Abstract Electrochemical synthesis of polyaniline (PANI) was carried out under cyclovoltammetric conditions using H 2 SO 4 , HCl, HNO 3 , and HClO 4 as supporting electrolytes. The observed different rate of PANI deposit growth depending on the acid in the solution has been explained on the grounds of a different degr…
The ab initio full-potential linearized-augmented-plane-wave method for a free-slab geometry was used to calculate the electronic structure and geometry of a clean ${\mathrm{TiO}}_{2}$ (110) rutile surface. Surface induced states were found in the density of states, such as an s-like surface state at -15 eV. Band bend…
Time-zero current-voltage characteristics and time-dependent current behavior of metal-ferroelectric-metal (Pt-PZT-Pt) capacitor structures have been studied. Under constant-voltage stressing, the current density through the 1500-Å-thick lead-zirconate-titanate (PZT) film exhibits a power-law dependence on time, with…
Intense laser irradiation has been used to anneal porous silicon. In situ Raman spectroscopy and photoluminescence (PL) spectroscopies have been used as probes of the silicon particle sizes and temperatures, and the resulting light emission of porous silicon. Once annealed, the PL of porous silicon while at 830 \ifmmo…