Materials Literature
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The nucleation and growth of diamond crystals on single-crystal copper surfaces implanted with carbon ions has been studied. Microwave plasma-enhanced chemical vapor deposition was used for diamond growth. The single-crystal copper substrates were implanted either at room temperature or at elevated temperature (∼820 °…
Motivated by widespread experimental observations of the ``banded structure'' in rapidly solidified alloys, we have studied numerically by Green's-function method the dynamics of the planar interface under rapid directional solidification condition. We find that the formation of this structure can be explained and par…
Comparison of Fourier transform infrared (FTIR) absorption spectroscopy, high resolution 13C nuclear magnetic resonance spectroscopy, and hydrogen evaluation by forward recoil elastic scattering (FRES) measurements shows that FTIR cannot be used to determine the carbon hybridization or total hydrogen content of diamon…
Porous silicon that strongly emits in the visible was analyzed using Raman scattering. The spectrum peaks near 508 cm−1, has a width of ∼40 cm−1, and is very asymmetric. Using a model of phonon confinement, this suggests that the local structure of porous silicon is more like a sphere than a rod and has a characterist…
Abstract Sizes of glass fibers used in composite materials include binders and coupling agents. Usually these types of compounds have a low molecular weight and present two identical reactive groups for binders and two different functions (namely, organic and inorganic groups) for the coupling agents. The aim of this…
Abstract The reaction of enzymic hydrolysis has been used as a probe to evidence the different structural features of bacterial native cellulose gels and films synthesized from different carbon sources. The gels were found to be more hydrolyzable than were the films, both in terms of reaction extent and of initial rea…
Abstract The structural characteristics and physical properties of epoxide‐treated tussah silk fibers from Antheraea pernyi silkworm are discussed in relation to the increasing weight gain values. Ethyleneglycol diglycidylether (E) and glycerin diglycidylether (G) were used as modifying agents. The noticeably high wei…
Polyhydroxybutyrate (PHB), a high molecular weight polyester, is accumulated as a storage carbon in many species of bacteria and is a biodegradable thermoplastic. To produce PHB by genetic engineering in plants, genes from the bacterium Alcaligenes eutrophus that encoded the two enzymes required to convert acetoacetyl…
Arc jet deposited films of diamond have been patterned using Au or photoresist masks and electron cyclotron resonance (ECR) O2 discharges. To achieve anisotropic features, additional RF-induced DC biasing of the sample is necessary. Diamond etch rates of 2000 Å/min were obtained for 1 mtorr, 400 W O2 discharges with −…
ABSTRACT Researchers have recently determined that capillary pressure plays a dominant role in controlling the texture, and hence the rheology, of foam flowing through a porous matrix. Of particular interest, the capillary pressure was found to reach a characteristic value, the limiting capillary pressure, at a relati…
The stabilities and growth kinetics of monoclinic celsian feldspar (BaAl2Si2O8) and of cymrite (BaAl2Si2O8.nH2O, where 0 < n < 1) have been investigated in the system BaO-Al2O3-SiO2-H2O at pressures up to 10 kbar and temperatures up to 800-degrees-C. Synthesis experiments and growth-rate studies using gel starti…
Tryptophan synthase from enteric bacteria is an alpha 2 beta 2 bienzyme complex that catalyzes the final two reactions in the biosynthesis of L-tryptophan (L-Trp) from 3-indole-D-glycerol 3'-phosphate (IGP) and L-serine (L-Ser). The bienzyme complex exhibits reciprocal ligand-mediated allosteric interactions between t…
Ammonia (NH3) and nitrogen (N2) were added to the hydrocarbon precursor 1,3 butadiene (C4H6) during rf plasma deposition of hydrogenated amorphous carbon (a:C-H) films. The effect of the additives on the film characteristics was determined by IR spectroscopy, solid state 13C cross polarization magic angle spinning nuc…
The critical dynamics near the consolute point of a relatively low molecular weight asymmetric critical binary polymer mixture is studied with dynamic light scattering. In contrast to a single exponential decay showing a critical slowing down, as has been reported for another low molecular weight polymer blend, we obs…
A combiation of video polarization microscopy and extensive digital line pattern analysis has been invoked to examine in quantitative detail the transformation of a lamellar into a ``labyrinthine'' magnetic-stripe domain pattern. The evolution of disorder is found to be mediated by a sequence of transverse, ``smectic'…
The mean-square displacement 〈\ensuremath{\Delta}${\mathit{r}}^{2}$(\ensuremath{\tau})〉 of particles in concentrated suspensions is measured at times sufficiently short to observe the transient nature of hydrodynamic interactions. For all volume fractions \ensuremath{\varphi}, the velocity autocorrelation function dec…
Substantial thinning or polishing of diamond films is a nontrivial problem because of the extraordinary hardness of diamond. In this letter, we report the observation of massive thinning of CVD diamond film (from ∼220 to ∼120 μm thickness) by simple diffusional transfer of carbon from diamond to iron foil at 900 °C. T…
Sputter-deposited SiO(X) (where X between 1.9 and 2.0) thin film coatings have been found to be durable to atomic oxygen. Such coatings will be used to protect polyimide Kapton photovoltaic array blankets from atomic oxygen attack in low earth orbit (LEO) on the Space Station Freedom (SSF). Monte Carlo modeling of ato…
Thermopower and electrical conductivity studies of copper substituted Mg-Al ferrites are undertaken over the temperature range 300 to 700 K. On the basis of the sign of the Seebeck coefficient (S), the ferrites under study can be considered as n-type semiconductors. A model is arrived at using Seebeck coefficient data…
The transport properties of undoped and copper-doped indium oxide and indium tin oxide ceramics are investigated. The correlation between density, carrier concentration, and mobility is analysed. The density of IO ceramics can be considerably increased by copper doping and approaches that of single crystals for 5 mol%…