Materials Literature
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The use of electron energy-loss spectroscopy for characterization of zirconium oxide pseudopolymorphs is investigated. The results demonstrate that spectroscopic ``fingerprints'' for each phase can be identified and the technique can be utilized for phase identification. The oxygen K-edge spectra are analyzed in detai…
Macroscopic particles of size a immersed in liquid crystalline solvents (e.g. polystyrene spheres in a lyotropic nematic) will exert long-range forces on each other by distorting the order-parameter field around them. As a first step towards a full theory of this novel class of suspensions, we show how to calculate th…
Temperature dependences of dielectric constants, specific heat and D – E hysteresis loops of Li-doped zinc oxide ceramics were investigated. A new dielectric anomaly was found at 330 K in Zn 1- x Li x O with x =0.17. A cusp-like anomaly was also found in specific heat. A ferroelectric D – E hysteresis loop was success…
The effects of growth processes on the chemical bond structure, microstructure, and mechanical properties of carbon–nitride (CNx) thin films, deposited by reactive magnetron sputtering in a pure N2 discharge, are reported. The film deposition rate RD increases with increasing N2 pressure PN2 while N/C ratios remain co…
Abstract The cornucopia of novel porhyrinoid macrocycles that ‐ as a result of a symbiotic link between annulene and porphyrin chemistry ‐ has emerged from the Cologne laboratory over the last decade is reviewed.
The dielectric and piezoelectric properties of solid solutions with compositions PbZr 1- x Ti x O 3 , x =0.200 to 0.750, with an 0.005Nb 2 O 5 additive prepared by modern ceramic technology were investigated, focusing on the morphotropic phase boundary (MPB, x =0.467). Relationships between the dielectric, piezoelectr…
The presence of two distinctly different local segmental mobilities found in the case of several phase mixed polymer blends by two-dimensional 2H-NMR, dielectric spectroscopy and depolarized dynamic light scattering is rationalized through a simple concentration fluctuation model. Our primary hypothesis is that, altho…
The paramagnetic insulator to ferromagnetic metal transition in lanthanum manganites and the associated magnetoresistive phenomena is treated by considering the localization due to random hopping induced by slowly fluctuating spin configurations and electron-electron interactions. The transition temperature and its va…
Tantalum (Ta) and tantalum nitride films (Ta2N and TaN) of about 50 nm thickness were reactively sputter deposited onto (100) Si substrate by using dc magnetron sputtering and their diffusion barrier properties in between Cu and Si were investigated by using sheet resistance measurement, x-ray diffraction, Auger elect…
Poly( p ‐phenylene terephthalamide) (PPTA) was prepared on a transparent indium‐tin electrode as a mechanically stable film by electrolysis of a dimethylsulfoxide solution containing PPTA polyanions. The PPTA film was electroactive because of its ionic conductivity. When an aniline derivative, o ‐phenylenediamine, was…
A composite film consisting of conducting poly( o ‐phenylenediamine) (PoPD) and insulating poly(vinyl alcohol) (PVA) has been prepared in a proportion which possesses satisfactory mechanical strength and characteristics favorable for a humidity senor. The electrical conductivity and PoPD content curves were measured,…
The reactions of HCOOH and CH3COOH on CeO2(111) and CeO2(100) were studied using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). The carboxylic acids were found to dissociate on both surfaces to form carboxylates. Adsorbed formates and acetates decomposed near 60…
Photoelectron spectra of a fivefold quasicrystalline alloy ${\mathrm{Al}}_{70}$${\mathrm{Pd}}_{21}$${\mathrm{Mn}}_{9}$ and a related cubic alloy ${\mathrm{Al}}_{60}$${\mathrm{Pd}}_{25}$${\mathrm{Mn}}_{15}$ reveal two noteworthy features. The first is that the Pd $3d$ lines fall at binding energies which are 2.2 eV hig…
In Ba(Ti 1- x Sn x )O 3 solid solution, for Sn concentration x ≤0.1, the permittivity follows the Curie-Weiss law above the Curie point T c . The increase in the peak value of the permittivity at T c is due to the change in ferroelectric transition from first order to second order with increasing x . For x >0.1, so…
A nanocomposite comprised of conductive poly(aniline) chains interleaved between the layers of sol‐gel derived displays desirable properties as a positive electrode in a Li battery. The reversible capacity of (after mild oxygen treatment) is higher than the xerogel at intermediate discharge/charge rates at constant cu…
Using multi-ion interatomic potentials derived from first-principles generalized pseudopotential theory, we have studied ideal shear strength, point defects, and screw dislocations in the prototype bcc transition metal molybdenum (Mo). Many-body angular forces, which are important to the structural and mechanical prop…
The dynamics of fluid flow through nanomachines is different from in other systems in that the flow is granular (no continuum assumption) and that the `walls' move. We have performed molecular dynamics simulations of the flow of helium and argon inside carbon (graphite) nanotubes of several sizes. The fluid was starte…
In this study a phenomenological constitutive model is proposed to describe the finite, nonlinear, viscoelastic behavior of glassy polymers up to the yield point. It is assumed that the deformation behavior of a glassy polymer up to the yield point is completely determined by the linear relaxation time spectrum and th…
The effect of heat treatment on the grain size, phase assemblage, and mechanical properties of a 3 mol% Y‐TZP ceramic was investigated. Specimens were initially sintered for 2 h at 1450°C to near theoretical density; some specimens were then heat‐treated at 1550°, 1650°, 1750°, or 1850°C to coarsen the microstructure.…
Authigenic minerals play an important role in the preservation of most soft-bodied fossils. The greatest detail is preserved in apatite (calcium phosphate) but its precipitation is usually inhibited by the high concentrations of HCO 3 - in aqueous settings. Nonetheless, investigations of soft-bodied biotas have reveal…