Materials Literature
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The combined electron and hole mobility of a single-crystal type IIa natural diamond and a polycrystalline diamond film deposited by chemical vapor deposition (CVD) were measured using transient photoconductivity as a function of excitation density (1013–1017 cm−3) and temperature (120–410 K). In natural diamond the t…
Abstract Two hexafluoro‐substituted aromatic polyimides, 6FDA‐ p ‐PDA and 6FDA‐4,4′‐ODA, were synthesized. The influence of some synthetic conditions on physical properties and gas permeabilities of the 6FDA polyimide membranes were studied. Gas permeabilities and permselectivities of six different gases for the homog…
Abstract The fiber/epoxy resin adhesion increases after plasma treatment on ultrahigh molecular weight polyethylene (UHMW‐PE) fibers. The surface modification of UHMW‐PE monofilaments was studied using a combination of techniques: contact‐angle measurements, SEM, and pullout tests. The results may be summarized as fol…
Different structural models for solid argon clusters with more than 500 atoms, that have been proposed previously on the basis of energy considerations, but whose origin and growth histories are not well understood, are compared with other models that have been devised mainly to overcome these difficulties, at the exp…
An experimental study of the effect of disorder on the nematic to isotropic (N–I) transition of a liquid crystal is reported. Differential scanning calorimetry is used to monitor the N–I transition of p-azoxyanisole in a series of controlled pore glasses. An increase and a decrease in the N–I transition temperature is…
Abstract A model two‐step synthesis of a saturated hyperbranched hydroxyl‐terminated ester has been developed to show a synthesis route. Three different series of hyperbranched esters with different terminations have been synthesized to relate some of their properties to their structures. This route has then been used…
Ordered diamond films have been deposited on single-crystal silicon substrates via an in situ carburization followed by bias-enhanced nucleation. Textured diamond films with greater than 50% of the grains oriented D(100)//Si(100) and D〈110〉//Si〈110〉 were grown in both a horizontal and vertical microwave plasma chemica…
Phenyl phenoxyformate, C 13 H 10 O 3 , M r =214.2, orthorhombic, P2 1 2 1 2 1 , a=6.062 (2), b=7.242 (1), c=23.375 (4) A, V=1026.2 A 3 , Z=4, D x =1.387 g cm -3 , λ(Mo Kα)=0.71069 A, μ=0.92 cm -1 , F(000)=448, T=164 K, R=0.0384 for 1375 unique reflections with I>2σ(I). Diphenyl car bonate constitutes the simplest cong…
Abstract Studies of the thermal and photodegradation of two commercial polymers, stabilized and unstabilized low‐density polyethylene, show the effects of weathering on differential scanning calorimetry (DSC) curves. The shape and the size of the melting peak vary significantly in thermal aging and in accelerated phot…
The luminescence of cerium-doped barium fluoride crystals has been investigated as a function of wavelength and time. For excitation UV light, X-rays and gamma rays were used. The well known cross luminescence (CL) near 200 nm and self-trapped exciton luminescence (STE) near 300 nm, which are due to excitations of the…
Abstract The thermal conductivities of unidirectional gel‐spun polyethylene fiber‐reinforced composites have been measured parallel (K∥︁) and perpendicular (K⊥) to the fiber axis from 15 to 300K. The axial thermal conductivity K∥︁ varies linearly with volume fraction v f of fiber, while the transverse thermal conducti…
A general formula for the optical-luminescence yield spectra arising from the core excitation is derived, making use of a simple phenomenological model. In this model, it is assumed that various excitations from core electron levels give rise to an identical luminescence in the individual yields. A smaller yield of th…
Photoablation of polymers by pulsed excimer laser radiation is commonly believed to be a controlled layer-by-layer removal process. A mass spectrometer was used to monitor neutral species ejected from polyimide samples in vacuum by 248 nm laser radiation. For fluences close to threshold, the ablation rate starts to dr…
The total energy of ZnS as a function of unit-cell volume has been calculated for the zinc-blende and rocksalt structures by the first-principles Hartree-Fock linear-combination-of-atomic-orbitals method. The calculated structural properties of both phases and the transition pressure between them agree very well with…
We consider the weakly first-order phase transition between the isotropic and ordered phases of nematics in terms of the behavior of topological line defects. Specifically, we present analytical and Monte Carlo results for a new coarse-grained theory of nematics which incorporates the inversion symmetry of nematics as…
We present a theoretical approach to study the conformational and thermodynamical properties of grafted polymer layers. The theory is based on the generalization of a mean-field approach previously used to treat chain packing in amphiphilic aggregates. The theory can be used for any chain model, for any mixture of gra…
We present dynamic light scattering data which show that aqueous gelatin gels display a power-law relaxation to a nonergodic background. In the pregel sol this power law is termined by a stretched exponential which restores ergodicity and which has a q dependent characteristic time proportional to the viscosity. The p…
Abstract The solubility of carbon dioxide, methane, and propane in poly(dimethyl silmethylene) [(CH 3 ) 2 SiCH 2 ] x and poly(tetramethyl silhexylene siloxane) [(CH 3 ) 2 Si (CH 2 ) 6 Si (CH 3 ) 2 O] x was measured in the temperature range from 10.0 to 55.0°C and at elevated pressures. The present results are compared…
Abstract The glass transition ( T g ) of thin polystyrene films (ca. 3000 A˚) cast on silicon wafers was determined by a new technique. An ellipsometer was used to determine the refractive index and thickness of the polystyrene films. T g was determined by measuring the temperature dependence of the refractive index.…
High quality, low resistivity (2.6×10−4 Ω cm), 0.32-μm-thick amorphous and polycrystalline, pure and Sn-doped, In2O3 films prepared by high density plasma-assisted electron beam evaporation were used to investigate the effect of Sn doping on the electronic transport properties of this material. Amorphous films with hi…