Materials Literature
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Variation of the preparation conditions of porous silicon carbide is shown to have a strong effect on the structural and electrical properties of the material obtained. A correlation has been observed between the fiber size and resistivity of porous SiC, a decrease of fiber size results in a semi-insulating material d…
Abstract Four different types of high‐density polyethylenes (HDPE) were blended with perlite at different concentrations. Silane coupling agent γ‐aminopropyltriethoxv silane (γ‐APS, A‐1100) was used to enhance the adhesion between perlite and HDPEs. Ultimate tensile strength and elastic modulus increased as the perlit…
The very high pressures (>1 GPa) that occur during the final stages of collapse of a cavitation bubble force the liquid near the bubble wall briefly (\ensuremath{\sim}1 ns) into a metastable state of subcooling, relative to the equilibrium phase diagram. Estimates for water show that solidification in the form of h…
We calculate the electrical conductivity, thermopower, and the electronic contribution to the thermal conductivity of a superlattice, with the electric field and the thermal gradient applied parallel to the interfaces. We include the tunneling between quantum wells. The broadening of the lowest subband when the period…
We show that arrays of tunnel junctions between normal metal electrodes exhibit features suitable for primary thermometry in an experimentally adjustable temperature range where thermal and charging effects compete. $I\ensuremath{-}V$ and $\frac{\mathrm{dI}}{\mathrm{dV}}$ vs $V$ have been calculated for two junctions…
Due to the overbinding that is inherent in existing {\em local} approximations to the density-functional formalism, certain reaction energies have not been accessible. Since the generalized gradient approximation significantly decreases the overbinding, prospects for density-functional-based reaction dynamics are prom…
We derive a stochastic nonlinear equation to describe the evolution and scaling properties of surfaces eroded by ion bombardment. The coefficients appearing in the equation can be calculated explicitly in terms of the physical parameters characterizing the sputtering process. We find that transitions may take place be…
The flow-graph approach (FGA) is applied to optical analysis of isotropic stratified planar structures (ISPS's) at inclined light incidence. Conditions for the presence of coherent and noncoherent light interaction within ISPS's are determined. Examples of the use of FGA for calculation of the transmission and the ref…
A colloidal suspension becomes unstable when a sufficient amount of non-ionic surfactant is added, undergoing a segregation process ascribable to depletion forces induced by the surfactant micelles. The concentrated phase which separates out is, however, less compact than theoretically expected and shows stable gel-li…
We study metastable PolyDimethylSiloxane (PDMS) films deposited on a substrate of fluorinated PDMS: after nucleation, a hole grows at constant velocity V. V is inversely proportional to the substrate viscosity and is proportional to - S , where S (< 0) is the spreading parameter. The velocity is a decreasing function…
The weak interplanar bonding in graphite is studied in the DFT formalism. The decomposition of the cohesive energy in its kinetic, electrostatic and exchange-correlation parts, coupled with the analysis of charge transfer, reveal an interplay between electronic delocalization and van der Waals contributions to the bon…
Reaction of pseudo-boehmite, [Al(O)(OH)] n, with carboxylic acids (RCO 2 H) results in the formation of the carboxylate-alumoxanes, [Al(O) x (OH) y (O 2 CR) z ] n where 2x + y + z = 3 and R = C 1 - C 13 . The physical properties of the alumoxanes are highly dependent on the identity of the alkyl substituents. The alum…
As in the first symposium volume (1), the term "inorganic and organometallic polymers" is primarily used to describe macromolecules that contain inorganic elements in the polymer backbone with either organic or inorganic side-groups. In addition to linear polymers with repeating monomer units, macromolecules consistin…
Carbon nanotubes produced in arcs have been found to have the form of multiwalled fullerenes, at least over short lengths. Sintering of the tubes to each other is the predominant source of defects that limit the utility of these otherwise perfect fullerene structures. The use of a water-cooled copper cathode minimized…
Dendrimers are well-defined, highly branched macromolecules that emanate from a central core and are synthesized through a stepwise, repetitive reaction sequence. The synthesis and characterization of dendritic boxes, based on the construction of a chiral shell of protected amino acids onto poly(propyleneimine) dendri…
An absolute pKa value of about 36 in acetonitrile is obtained for porphyrin from its reaction with phosphazene bases. The monoanion 1 is stable in aprotic solvents and was characterized by NMR and UV/ Vis spectroscopy. The remaining central proton in the monoanion migrates between the four nitrogen atoms much faster t…
Isolated fibers the thickness of a molecule but more than 104 molecules long are present in the gel formed from a solution of 1 in chloroform. This molecular stack may be seen as a molecular cable containing many wires and constructed from a stack of phthalocyanine units, four stacks of crown ether units, and a surrou…
We study the antiferrodistortive instability and its interaction with ferroelectricity in cubic perovskite compounds. Our first-principles calculations show that coexistence of both instabilities is very common. We develop a first-principles scheme to study the thermodynamics of these compounds when both instabilities…
The threshold energy surface for permanent atom displacements in copper at 550 K is determined by observing the growth of interstitial-type dislocation loops during electron irradiation in a high-voltage electron microscope. Comparison with the results of King et al. and Baily et al., obtained by measurements of the r…
In situ measurements of the dislocation mobility in polycrystalline silicon are carried out in a 1000 kV high voltage electron microscope (HVEM) using a heating-straining stage at temperatures between 530 and 780 °C. Most of the dislocations are found to move in the (111) [101] glide system. The effective shear stress…