Materials Literature
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The force as a function of separation is measured between two mica surfaces coated with adsorbed bilayers of cetyltrimethylammonium bromide (CTAB) and immersed in aqueous ionic micellar solutions of CTAB. At low separations double-layer forces are observed and arise soley from the dissociated counterions and free ${\m…
Molecular dynamics simulations reveal the mechanism of the structural memory effect in alpha-berlinite (AlPO(4)), where a single crystal transforms to an amorphous solid by compression and then reverts to the original crystalline structure upon release of pressure. The enhanced oxygen coordination around the aluminum…
Abstract Ferromagnetism is a well-known phenomenon wherein solids exhibit spontaneous magnetization even in the absence of an external magnetic field. An important characteristic of ferromagnetic materials is the hysteresis loop found in the relationship between magnetization and magnetic field. The electrical analogu…
To investigate the pH dependence of the conformational stability of barnase, urea denaturation curves were determined over the pH range 2-10. The maximum conformational stability of barnase is 9 kcal mol-1 and occurs between pH 5 and 6. The dependence of delta G on urea concentration increases from 1850 cal mol-1 M-1…
Cathodoluminescence (CL) in a transmission electron microscope has been used to investigate impurities and defects in single crystals in diamond films grown by the combustion-flame method and correlate them with the microstructure. Nitrogen was present in a number of different impurity defect forms; band A emission wa…
The Nasicon-type phosphate CuZr 2 (PO 4 ) 3 exhibits two fluorescences occurring in the violet and green regions. They are assigned to two different centres: the violet one to isolated Cu + and the green one to Cu + -Cu + pairs occupying the same site. These assignments are in agreement with previous structural invest…
We describe a new technique for measuring the thickness and optical constants of dielectric, semiconducting, and thin metal films. Beam profile reflectometry provides excellent precision for films as thin as 30 Å and as thick as 20 000 Å. The technique is also capable of simultaneous 2 and 3 parameter measurements and…
We show by scanning tunneling microscopy (STM) imaging that native oxide growth in moist air on hydrogen terminated Si(111) 1×1 surfaces begins by continuing formation of small oxide nuclei, 10–20 Å in diameter, in the topmost Si layer. Their statistical distribution on the flat terraces points to a homogeneous nuclea…
Gadolinium clusters (N=11--92) in a molecular beam exhibit dramatic size dependences in their magnetic properties. Two principal behaviors are observed: rigid rotor precession and nutation when the magnetic moment is tightly locked to the lattice by crystal anisotropy, and superparamagnetism when the moment is approxi…
Unidirectional charge flow was observed in potassium tantalum niobate, ${\mathrm{KTa}}_{0.6}$${\mathrm{Nb}}_{0.4}$${\mathrm{O}}_{3}$, films. These films of relaxor-type diffuse phase transition material were formed by metalorganic deposition and had a polarization gradient normal to the surface of the films. Novel cha…
We have measured the temperature dependence of the photoluminescence of porous silicon and have found that it disagrees with the expected behavior of crystalline or amorphous silicon. We also found that soaking the samples in oxygen and simultaneously illuminating them with light results in the quenching of the photol…
Abstract Some resins have been synthesized by reacting quinacetophenone with substituted benzoic acids and furfuraldehyde in the presence of basic catalysts. The resins have been characterized by IR spectra of the characteristic groups. The number average molecular weights of the resins have been evaluated by the cond…
Abstract Polyethylene was reacted with maleic anhydride and N ‐phenylmaleimide in solution. The effect of modification on its physico–chemical properties, such as mechanical, oxygen gas transmission, water vapor transmission, and grease resistance properties, was studied.
Abstract New model compounds for poly[ N,N′ ‐bis(phenoxyphenyl)pyromellitimide] have been synthesized in order to investigate the formation of imine bonds which are proposed to form during the curing process and lead to crosslinking in the bulk polymer. Raman studies show that terminal amines can react with imide carb…
Abstract The amount and structure of the crystals formed by the solvent‐induced crystallization (SIC) following a sorption‐desorption cycle of five fluids (benzene, toluene, chloroform, methylene chloride, and carbon disulfide) in amorphous PEEK was determined by wideangle x‐ray scattering (WAXS). The SIC crystal stru…
The quality of hot-filament chemical-vapor-deposited diamond films has been quantitatively assessed by 1H and 13C nuclear-magnetic-resonance (NMR) spectroscopy. As the carbon mole fraction increases from 0.053 to 0.074 in the gas phase, film quality in terms of sp2 carbon content, bonding disorder, and spin-lattice re…
The spin dependence of low-energy electron absorption and reflection from ferromagnetic Fe(110) is investigated using the normalized difference between the absorption (or reflection) of electrons polarized parallel and antiparallel to sample magnetization. The resulting absorption and reflection spin asymmetries are f…
The temperature-dependent optical spectra of the major insulating forms of polyaniline—the fully reduced leucoemeraldine base, half-oxidized emeraldine base (EB), and fully oxidized pernigraniline base (PNB)—and of two oligomeric model compounds for polyaniline are reported. All three forms of the polymer possess a ∼3…
Depolarized Rayleigh spectra of ortho-terphenyl (OTP) were measured in the temperature range from Tg to Tg+190 K. Two samples prepared with and without ‘‘clusters’’ were used for the measurement. Four different Fabry–Perot interferometers covering the time range from about 0.5 ps to 100 ns were employed. Two relaxatio…
Studies have been conducted to further characterize overoxidized polypyrrole films grown on carbon electrodes. Differences in apparent diffusion coefficients for various probes are interpreted via a model based on both hydrophobic and electrostatic interactions between the probe and polymer film. These electrode coati…