Materials Literature
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The buildup of the internal bias in time and the decrease of the internal bias by forced switching of the polarization by an ac field have been described empirically by various authors. Both time dependencies can now be derived from a simple model, proposed recently by G. Arlt and H. Neumann [Ferroelectrics 87, 109 (1…
The effect of a dense electron-hole plasma on the stability of the diamond lattice of the crystalline group-IV elemental semiconductors C, Si, and Ge is examined with use of a tight-binding model. Such a plasma may result, for example, from a short, intense laser pulse. We find that the transverse-acoustic phonons of…
We have carried out a detailed investigation of liquid carbon (l-C) at T\ensuremath{\simeq}5000 K, and quenched amorphous carbon (a-C) at room temperature, using a first-principles molecular-dynamics method. In this paper we report calculations performed for a fixed density corresponding to low pressures. From our res…
A new slab model approach is examined for the electronic structure calculation of a polar semiconductor surface. Our proposed slab model contains fractionally charged H atoms which completely terminate a noninteresting surface of the slab. We have studied in detail the electronic structure of the polar GaAs(001) surfa…
We report an experimental investigation of the dependence of the lowest exciton energy of CdS clusters (quantum dots) on the cluster size. The cluster diameter is varied from 60 to 10 \AA{}. X-ray diffraction provides definitive identification of the cluster phase and permits a determination of the average cluster siz…
Fourier transform infrared absorption spectroscopy has been utilized to characterize the structure of porous silica gel films, both deposited on c-Si substrates and free standing. The films were either dried at room temperature or subjected to partial densification at 400–450 °C. The spectra of the gel films are compa…
Abstract The chemical incompatibility of infected seawater and formation water has prompted deposition of barium and strontium sulphate scales in producing wells of the Namorado field. The precipitation Squeeze process was chosen as a means of preventing scale formation in this field. The present paper describes tests…
The angle-resolved secondary-electron emission (ARSEE) spectra of highly oriented pyrolytic graphite have been measured in the 7-70 eV electron kinetic energy range. A peak observed at approximately=59 eV with K/sub ///=1.35-1.65 AA -1 was tentatively explained within a semiempirical approach based on a free electron…
Epitaxial thin films of ferroelectric bismuth titanate Bi4Ti3O12 have been grown by pulsed laser deposition on single-crystal [100] SrTiO3 substrates. Bismuth titanate has a high Curie temperature (675 °C) and saturation polarization values of 4 and 50 μC/cm2 along the c and b axis, respectively. Its a,b lattice param…
The pressure dependences of the Raman-active graphite layer shearing modes in highly oriented pyrolytic graphite (HOPG) and FeCl 3 -HOPG acceptor intercalation compounds for stage indices n=1, 2 and 3 have been measured in diamond anvil cell by use of a Spex-1403 Ramalog system. The results of high-pressure Raman spec…
The radial distribution function obtained by neutron diffraction on amorphous carbon films is compared to recent theoretical models. The first-neighbor peak is found to be quite broad for an amorphous semiconductor, in qualitative agreement with the predictions of molecular dynamics. However, the detailed shape of the…
It is shown that root lattices and their reciprocals might serve as the right pool for the construction of quasicrystalline structure models. All noncrystallographic symmetries observed so far are covered in minimal embedding with maximal symmetry.
Abstract The grafting and the crosslinking of polybutadiene during the bulk thermal polymerization of high‐impact polystyrene were studied. The kinetic equations for these two reactions were derived by the use of the moments of the distribution functions. This kinetic model indicates that both the density of grafting…
Abstract The permeability of CO 2 through polyurethane was investigated. It is found that the permeability increases with the decrease of hard segment content and the increase of soft segment length; however, no change of activation energy is involved. The permeability increases with the elevation of annealing tempera…
Abstract A method has been developed to cast novel organic/inorganic hybrid films from multicomponent solutions containing titanium alkoxides, poly( n ‐butyl methacrylate), water, and isopropanol of prescribed compositions. The sol–gel reactions and controlled drying procedure yielded materials of mechanical integrity…
Abstract In recent years, tetraethyl orthosilicate (TEOS) has been used as a precursor in preparing inorganic glasses. The technique, known as the sol‐gel process involves a two step poly(hydrolysis‐condensation)reaction sequence. The work presented here is concerned with the utilization of a suitably functionalized o…
Article The Role of Oxygen for the Spinel Interphase Formation at Diffusion-Bonded Ni/Al2O3 Interfaces) / Der Einfluß des Sauerstoffes auf die Spinellreaktionsschichtbildung an diffusionsverschweißten Ni/Al2O3 Grenzflächen was published on October 1, 1990 in the journal International Journal of Materials Research (vol…
Rare-earth doped phosphors are discussed here which exhibit intense fluorescence well above 1000C. This is a rare characteristic for solidstate materials. One immediate application for them is thermometry. For example surface temperatures of rotating components systems in hostile or restricted environments and systems…
It has previously been determined that absorption of infrared radiation in germanium due to free carriers can be controlled to some extent by doping. As a result, the use of germanium in infrared systems can be extended to thermal environments not possible before. This can be accomplished by using lower resistivity ge…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotoisomerization of spirobenzopyran in polystyrene filmToshiaki Ito, Mitsuo Hiramatsu, Isuke Hirano, and Hiroyuki OhtaniCite this: Macromolecules 1990, 23, 21, 4528–4532Publication Date (Print):October 1, 1990Publication History Published online1 May 2002Published inissue…