Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
The static electric polarizability tensor of single-wall carbon nanotubes is calculated within the random-phase approximation using a simple tight-binding model and a classical correction to include local fields. We find that the polarizability for constant fields parallel to the cylindrical axis is highly dependent o…
Using first-principles band-structure theory we have systematically calculated the (i) alloy bowing coefficients, (ii) alloy mixing enthalpies, and (iii) interfacial valence- and conduction-band offsets for three mixed-anion (CuInX2, X=S, Se, Te) and three mixed-cation (CuMSe2, M=Al, Ga, In) chalcopyrite systems. The…
The fundamental absorption edge of the anatase phase of ${\mathrm{TiO}}_{2}$ has been studied by performing polarized optical transmission measurements on single crystals at temperatures ranging from 4.2 to 300 K. An Urbach tail has been found that shows an exponential spectral dependence down to liquid-helium tempera…
Field emission of electrons from individually mounted carbon nanotubes has been found to be dramatically enhanced when the nanotube tips are opened by laser evaporation or oxidative etching. Emission currents of 0.1 to 1 microampere were readily obtained at room temperature with bias voltages of less than 80 volts. Th…
The dynamics of spreading of small amounts of viscous fluids are usually investigated using spherical droplets of oils. Recently we applied Frenkel's method to this problem and obtained a wide angle relation between the edge speed and the dynamic contact angle and this gave good agreement with literature data. In this…
Ion beam sputtering and dual ion beam sputtered films of titanium oxide were prepared and investigated at room temperature and compared with similar films prepared by e-beam (EB) gun deposition. Optical properties, i.e. Refractive index n and extinction coefficient k of films were determined by transmission spectropho…
Abstract An on‐line sensor for estimating conversion from measurements of ultrasound propagation velocity in emulsion polymerizations has been developed. The sensor does not require a sampling circuit, because it can be directly plugged in the reacting mixture. The performance of the sensor has been tested by comparis…
Abstract Nylon 6 was prepared by adiabatic anionic polymerization of ϵ‐caprolactam using hexamethylene dicarbamoyl dicaprolactam (HDC), cyclohexyl carbamoyl caprolactam (CCC), or phenyl carbamoyl caprolactam (PCC) as activators and sodium caprolactamate (NaCL) as a catalyst at various initial reaction temperatures ran…
Abstract This article describes a number of chemical routes for the recycling of sheet‐molding compounds (SMC) consisting of glass fibers, filler (calcium carbonate), and an unsaturated polyester–styrene thermoset resin. Treatment of milled SMC with ethanol/potassium hydroxide at 85°C for 48 h ultimately affords a sol…
Efficient conversion of infrared radiation centred at 1 mu m into visible luminescence has been observed in cubic Cs 2 NaErCl 6 crystals in which electric dipole transitions are forbidden by symmetry selection rules. Luminescence originating from the 4 F 9/2 and 4 T 9/1 levels of Er 3+ increases strongly with increasi…
We report a dependence of the photoabsorption cross section as measured by total electron yield at the Fe and Co $3p$ thresholds on the sign of the magnetization for $p$-polarized light at oblique incidence. Peak-to-peak asymmetries up to 4% are observed. The asymmetry increases towards grazing incidence, where the to…
We propose a phase-field model for the kinetics of isothermal crystallization of an amorphous solid at a concentration nearly equal to the equilibrium crystal stochiometry. The model utilizes two coupled fields: a nonconserved ordering vector field which describes the local lattice structure and a conserved nonorderin…
We have used molecular dynamics and simulated annealing to study an asymmetrical $\ensuremath{\Sigma}3$ tilt grain boundary with $〈211〉$ rotation axis in Cu. The boundary plane was inclined at 84\ifmmode^\circ\else\textdegree\fi{} with respect to the ${}\left(111\right)$ plane. A simple central force $N$-body interato…
We report the observation of the anisotropic linear polarization of porous Si photoluminescence measured in two excitation geometries. In the normal excitation geometry (exciting beam normal to the sample (100) surface) linear luminescence polarization of as much as 20% is seen parallel to the excitation polarization.…
Using an aluminum–porous p+ silicon junction, we have realized a sensor which dc current increases up to two orders of magnitude in the presence of ammonia, as for a series of various gases. To interpret quantitatively this phenomenon, we assume that the conductivity is governed by the width of a channel resulting fro…
For the first time we present results of ab initio calculations of the structural and electronic properties of heterocrystalline combinations of a cubic (3 $C$) and a hexagonal ( $\mathrm{pH}$, $p\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2,4,6$) polytype of SiC, the material exhibiting the most pronounced pol…
Theoretical and experimental results are presented providing evidence for fast Auger recombination in silicon nanocrystallites. Calculations give nonradiative lifetimes in the 1 ns range. Luminescence experiments on porous silicon exhibit a saturation at high excitation power. The Auger effect gives a natural explanat…
The domain structure of ferroelastic BiVO 4 crystals was investigated by X-ray diffraction, nuclear magnetic resonance, optical polarizing microscopy, transmission electron microscope, and electron diffraction techniques. From these results, it is found that the BiVO 4 crystals have only prominent W walls and no non-p…
The projection of the eigenfunctions obtained in standard plane-wave first-principle calculations is used for analyzing atomic-orbital basis sets. The "spilling" defining the error in such a projection allows the evaluation of the quality of an atomic-orbital basis set for a given system and its systematic variational…
Optical components are usually classified into diffractive and refractive elements. In this classification, refractive components are defined as elements that are sufficiently described by geometrical optics. For micro-optics this distinction is very often not applicable. Our goal is to understand which parameters con…