Materials Literature
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Porous silicon layers grown on nondegenerated p-type silicon electrodes in hydrofluoric acid electrolytes are translucent for visible light, which is equivalent to an increased band gap compared to bulk silicon. It will be shown that a two-dimensional quantum confinement (quantum wire) in the very narrow walls between…
Living polymerization techniques can be used to achieve a high degree of control over polymer chain architecture. Examples of the type of polymers that can be synthesized include block copolymers, comb-shaped polymers, multiarmed polymers, ladder polymers, and cyclic polymers. This control of structure, in turn, resul…
Different polymers can be combined into a single material in many ways, which can lead to a wide range of phase behaviors that directly influence the associated physical properties and ultimate applications. Four factors control polymer-polymer phase behavior: choice of monomers, molecular architecture, composition, a…
Polymers attached by one end to an interface at relatively high coverage stretch away from the interface to avoid overlapping, forming a polymer "brush." This simple picture may serve as the basis for models in diverse interfacial systems in polymer science, such as polymeric surfactants, stabilized suspensions of col…
Abstract A study has been made on the effect of mineral and organic acids on the radiation‐induced graft polymerization of styrene onto low‐density polyethylene films. Effects of different solvents and dose rate of irradiation on the grafting yield were also investigated. The influence of irradiation time and monomer…
Abstract A program has been developed for the prediction of sulfate scale formation in single waters or mixtures. The program considers the effect of pressure, temperature, and brine composition using classical thermodynamics and modem electrolyte theory. The important effect of [MgS04°] ion pairing is considered expl…
Abstract This study focuses on the thermal behavior and curing kinetics of a commercially available poly(carbosilane). Poly(carbosilane) is used for the production of silicon carbide (SiC) fibers by high‐temperature pyrolysis. Thermal characterization studies were carried out by employing a differential scanning calor…
Abstract The increase in the viscosity of an aqueous solution or gel of hydroxypropylmethylcellulose (HPMC) in the presence of an anionic surfactant is attributed to a two‐step process: (a) the surfactant undergoes ion–dipole interaction with the ethereal oxygen in HPMC, in the absence or presence of water, and (b) hy…
We have measured the surface index change and birefringence in K(+)-Na(+) ion-exchanged waveguides and compared the results with theory. The contribution to the index change caused by the polarizability/volume changes (Deltan(p)) is calculated using two theoretical models which use empirical relations based on the gla…
Abstract Composites of styrene–butadiene rubber were prepared with three different types of lead oxide, namely, monolead oxide (PbO), lead dioxide (PbO 2 ), and red lead oxide (Pb 3 O 4 ). Concentrations of Pb 3 O 4 ranging between 17 and 88 wt % were utilized, whereas 87 wt % was used for PbO and PbO 2 . The prepared…
Molecular dynamics computer simulations have been carried out on a system consisting of cylindrically symmetric molecules with length-to-breadth ratio k = 3 and well depth ratio k′ = 5 interacting through the Gay-Berne potential. For this system we have located the coexistence points corresponding to the isotropic-nem…
Abstract Tests in Berea sandstone cores have been carried out which simulate scale inhibitor treatments by the precipitation squeeze method. The studies have shown that squeezes with common phosphonate inhibitors last twice as long as squeezes using common polymer inhibitors in cores containing brines with low calcium…
Indium—tin oxide (ITO) applied to optoelectronic devices must meet several requirements simultaneously, i.e. electrical conductivity, optical transparency, and structurability by photolithography. As will be shown, these properties are mainly based on the microstructure of the ITO films. The microstructure changes fro…
The superspace description of incommensurably modulated crystals is used to generalize commonly used band-structure methods to cover this class of crystals. The methods considered are the nearly-free-electron method, the tight-binding method, and the Korringa-Kohn-Rostoker equations in the atomic-sphere approximation.…
We present a calculation of the cluster integrals which appear in the density expansion of the inverse mean cluster size for an assembly of spherical particles with a square well potential where the range of connectedness is equivalent to the interparticle interaction range. This percolation series is constructed to t…
The effects of uniaxial stress σ y y on the incommensurate (INC) phase transition of quartz have been investigated by light scattering spectroscopy. The 1q INC phase is induced between β and the 3q INC phase and its region becomes wider with the increase of stress. Anomalies of the central peak in the Rayleigh-Brillou…
A method to determine the switching field distribution Hs(■cr>gc0) of powder assemblies of magnetically hard materials with a random orientation of the easy axes is described. The method is based on the ferromagnetic resonance absorption and the measurements of remanence curves. Direct information about the swi…
The temperature dependence from ambient to 2325 K of the high frequency E2g mode intrinsic to the hexagonal phase of boron nitride has been determined using a pulsed-excitation gated-detection technique which effectively discriminates against sample blackbody emission. A monotonic decrease of 80 cm−1 in mode frequency…
The resistivity of polypyrrole films, from 300 to 1.3 K, doped with ${\mathrm{ClO}}_{4}$ ions at various concentrations to have a different number of polarons and bipolarons, can be better fitted by ${\mathit{T}}^{\mathrm{\ensuremath{-}}1/3}$ than ${\mathit{T}}^{\mathrm{\ensuremath{-}}1/4}$. The conduction process in…
Chlorine incorporated into silica glasses by sintering porous soot rods under Cl2/He atmosphere or by fabricating with plasma methods were found to be mostly as ≡SiCl, which gives rise to an optical absorption tail above ≂7.5 eV. The cross section of the optical absorption at ≂7.77 eV (160 nm) was found to be 1.14×102…