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。
Suppression of the multiphoton fluorescence contribution to the hyper-Rayleigh (second-order nonlinear optical) scattering signal was recently achieved by intrinsic demodulation of the fluorescence at high amplitude-modulation (AM) frequencies [Olbrechts et al., Rev. Sci. Instrum. 69, 2233 (1998)]. These high AM frequ…
Dielectric surface flashover in vacuum is characterized by a three-phase development, as shown by current measurements covering the range from 10−4 to 100 A, assisted by x-ray emission measurements, high speed photography, and time-resolved spectroscopy. Further information is gained from a comparison of the flashover…
New dianhydrides containing t-butyl and phenyl pendant groups have been synthesized and used as monomers, together with commercial diamines, to prepare novel polyimides. The influence of the chemical structure of the monomers on their reactivity has been studied by quantum semiempirical methods. The polyimides have be…
As a contribution to the understanding of the thermodynamics of the glass transition phenomenon a series of molecules having the same steric character, but differing in the strength and nature of intermolecular interactions, has been investigated. The series is based on systematic changes of substituents on disubstitu…
Structural materials for first–wall and breeding-blanket components will be exposed to 14\3MeV neutrons, plasma particles and electromagnetic radiation. In magnetically confined systems, the operation mode will be quasi–continuous. Typical operation conditions for next–step devices and demonstration plants will be des…
The surface phonon mode of CdSe quantum dots in a glass matrix was investigated by Raman spectroscopy. The blueshift and broadening of the surface phonon frequency were observed as the quantum dot size was reduced. It was shown that the observed size-dependent blueshift and broadening are mainly caused by the lattice…
The transition from the dynamics of isolated molecules to that of a bulk liquid is observed for the first time by analyzing the dielectric relaxation $({10}^{\ensuremath{-}2}--{10}^{9}\mathrm{Hz})$ of ethylene glycol (EG) guest molecules confined to zeolitic host systems of different topology. Beyond a threshold chann…
Dielectric films have been prepared by radio-frequency plasma-enhanced chemical vapor deposition from mixtures of tetramethylsilane with oxygen. The films have been characterized as-deposited and after annealing at 400 °C to determine the thermal stability of their properties. Rutherford backscattering and forward rec…
Nanocrystallites of semiconductors, especially those belonging to II-VI and III-V groups, show size-dependent optical and electrical properties. In this paper we report on x-ray photoemission results of CdS nanocrystallites of two different sizes and compare these results with bulk CdS. The S $2p$ and $2s$ core levels…
Further insight into processing-structure-property relationships have been carried out for existing and candidate carbon-based protective overcoats used in the magnetic recording industry. Specifically, 5 nm thick amorphous diamond-like carbon (a:C) and nitrogenated diamond-like carbon (a:CNx) overcoats were deposited…
By means of extensive Monte Carlo simulations of the bond fluctuation model, we study the effect of adding AB diblock copolymers on the properties of an interface between demixed homopolymer phases. The parameters are chosen such that the homopolymers are strongly segregated, and the whole range of copolymer concentra…
Density functional calculations have been performed for many isomers of neutral carbon clusters Cn (4⩽n⩽32, n even) using both local spin density (LSD) and gradient-corrected (Becke–Perdew) approximations to the exchange-correlation energy. The stable isomers include chains, rings, cages, and graphitic (“plate ” and “…
We present the first successful attempt at calculating cluster full-potential x-ray absorption near-edge structure (XANES) spectra, based on the finite difference method. By fitting XANES simulations onto experimental spectra we are able to perform electron population analysis. The method is tested in the case of Ti $…
We study hydrogen-bond dynamics in liquid water at low temperatures using molecular dynamics simulations, and find results supporting the hypothesized continuity of dynamic functions between the liquid and glassy states of water. We find that average bond lifetime $(\ensuremath{\sim}1\mathrm{ps})$ has Arrhenius temper…
We present a detailed study of the electronic properties of CdSe nanocrystals in the absence and presence of a dielectric medium. The electronic structure of the nanocrystal is modeled within the framework of the empirical pseudopotential method. We use a real-space grid representation of the wave function, and obtain…
The shear viscosity of liquid ${\mathrm{Zr}}_{41.2}{\mathrm{Ti}}_{13.8}{\mathrm{Cu}}_{12.5}{\mathrm{Ni}}_{10.0}{\mathrm{Be}}_{22.5}$ has been measured. At the liquidus temperature we find an extremely high viscosity of 2.5 Pa s, favoring glass formation. At deep supercooling the time scales for the diffusion of small…
We have investigated the effects of nanometer-sized silver particles on the optical properties of Eu3+ ions in SiO2 glass. Glass samples were prepared by the sol-gel method. The mean particle size and volume fraction of silver particles, which were estimated from UV-VIS absorption spectra using Mie-Drude theory modifi…
The electronic structure of various nickel oxides with nickel valence varying from 1+ to 3+ was investigated with the aim to find similarities and differences to the isoelectronic cuprates. Only if the Ni ions are forced into a planar coordination with the O ions can a $S=1/2$ magnetic insulator be realized with the d…
We present measurements of the lattice thermal conductivity ${\ensuremath{\kappa}}_{\ensuremath{\perp}}$ normal to the interfaces of $(\mathrm{GaAs}{)}_{n}/(\mathrm{AlAs}{)}_{n}$ superlattices with n between 1 and 40 monolayers. The conductivity was measured by an optical pump-and-probe technique in the temperature ra…
Electronic and magnetic properties of ribbon-shaped nanographite systems with zigzag and armchair edges in a magnetic field are investigated by using a tight-binding model. One of the most remarkable features of these systems is the appearance of edge states, strongly localized near zigzag edges. The edge state in a m…