Materials Literature
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By solving the full elastic equations on a two-dimensional lattice we grow cracks under various breaking conditions for a system that is submitted to external shear. We find that deterministic fracture patterns are in general branched and can be fractal. This effect is due to the competition between the direction of g…
We introduce a Ginzburg-Landau model for solid solutions to examine elastic effects near the phase separation. As a first application the spinodal curve is calculated when the elastic moduli depend on the concentration and an external stress is applied. The instability is triggered by fluctuations with wave vectors in…
Valence-band and core x-ray-photoemission spectroscopy has been used to examine the electronic structure of FeOOH and ${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$. The known small difference in the core-level Fe 2p spectra of the two compounds is discussed. X\ensuremath{\alpha} calculations of an ${\mathrm{FeO}}_{6}$${\mathr…
We report a systematic study of the segregation of third-column elements involved in group III-V arsenide structures to their (100) surface. The surface composition is obtained by in situ electron spectroscopies, on special structures built by molecular-beam epitaxy. In ternary alloys, an important surface enrichment…
We have obtained and analyzed Raman spectra of single-crystal, hot-pressed, and chemical-vapor-deposited boron carbide materials over their single-phase region (from \ensuremath{\sim}9 to \ensuremath{\sim}20 at. % carbon). These spectra provide insight into the substitutional disorder that characterizes these structur…
Semiempirical potentials for silicon, germanium, and their alloys are derived with use of the modified-embedded-atom-method formalism. Following Baskes [Phys. Rev. Lett. 59, 2666 (1987)], it is found that the host electron density which is a linear superposition of atomic densities in the embedded-atom method (EAM) mu…
The low-temperature near-band-gap photoluminescence of ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{\mathrm{x}}$ is studied over the whole composition range 0\ensuremath{\le}x\ensuremath{\le}1. We identify free- and bound-exciton processes and determine the properties of momentum-conserving phon…
The oxygen 1s x-ray-absorption edges of a series of 3d-transition-metal oxides have been measured. The structures at the edge arise from covalent mixing of the metal and oxygen states, which introduces oxygen p character in unoccupied states of mainly metal character. The spectra can be divided into two regions: The f…
Spin polarisation of Auger electrons arising from photoionisation of atoms by circularly polarised photons is studied theoretically. Calculations show that in a wide range of photon energies the polarisation is large and can be measured in experiment. It is shown that the polarisation transfer can be used to study the…
Glass-metal nanocomposites incorporating ultrafine particles of iron, nickel, cobalt and manganese, respectively, in a silica glass matrix have been prepared by heat treatment of a gel derived from a sol containing silicon tetraethoxide and a suitable metal organic compound. Metal particles in all the nanocomposites a…
The extinction coefficient of a weak absorbing film can be extracted from special absorption using a simple formula, provided the substrate is a kind of glass of refractive index within the range of 1.5-1.7.
The authors have used cathodoluminescence spectroscopy to examine point defects present in polycrystalline diamond films grown by the decomposition of a methane-hydrogen mixture in a microwave plasma. For films grown with low methane concentrations (0.3%) the bright-blue luminescence is predominantly due to donor-acce…
Two of the materials most often used as optical windows due to their high transmittance at infrared wavelengths are zinc selenide (ZnSe) and zinc sulfide (ZnS). However, these materials are soft and often degrade when subjected to a particle-impacting environment. Diamondlike carbon (DLC) films have the potential to p…
We present a model of insulating glasses in which defects interact strongly via the elastic strain field. The interactions are oscillatory at short range and cross over to 1/${r}^{3}$ interactions at longer length scales. This crossover is marked by a strong renormalization of the density of states and is consistent w…
The electrical conductivity of diamond thin films produced by the hot-filament technique is found to increase when diborane is incorporated in the precursor gas mixture. The combination of well-defined bulk conductivity measurements with quantitative secondary-ion mass spectrometry and Raman spectroscopy shows that th…
Band-structure calculations of ferromagnetic Fe 1/3 TaS 2 and Mn 1/3 TaS 2 using the augmented spherical-wave method are reported. The calculations give a spin magnetic moment of 4.35 mu B per Fe for Fe 1/3 TaS 2 and 4.18 mu B per Mn for Mn 1/3 TaS 2 . The local moments at Fe and Mn induce a magnetic polarisation of t…
We study surface and bulk equilibrium in Si-Ge alloys by direct simulation. The composition at a reconstructed (100) surface varies with depth in a complex oscillatory way. Lateral ordering occurs even in the fourth layer, driven by the local stress field. The bulk phase diagram is well described by regular solution t…
The gases that are emitted when an encapsulant resin is exposed to a high-temperature were analyzed by GC-MS. The effect of these gases on IC devices were studied using a Teflon vessel. The result showed that large amounts of bromides and organic acids are emitted from the encapsulant resin and that these gases are ge…
Abstract Mechanical blends of copolymer‐type polyacetal (POM) with ester‐based and ether‐based polyurethane (PU) are immiscible over the 0–50% PU compositional range. The PU elastomer was added to the rigid POM matrix to increase its toughness. The mechanical, physical, thermal, dielectric, and dynamic mechanical prop…
Abstract Homogeneous periodate oxidation of cellulose was achieved through methylol cellulose. The dissolution of methylol cellulose into aqueous periodate solution was followed by the gradual decomposition of methylol groups at random sites along the methylol cellulose chain. The recovery of glycol hydroxyl groups at…