Materials Literature
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Atoms, molecules, enzymes, proteins, DNAs, RNAs, nanoparticles, microparticles, tiles, and bricks are some of the most commonly encountered building blocks in chemistry and architecture. These building blocks can be grouped into subnanometer (atoms), nanometer (molecules, enzymes, proteins, DNAs, RNAs, and nanoparticl…
We report frequency and dissipation scaling laws for doubly-clamped diamond resonators. The device lengths range from 10 microns to 19 microns corresponding to frequency and quality-factor ranges of 17 MHz to 66 MHz and 600 to 2400 respectively. We find that the resonance frequency scales as 1/L^2 confirming the valid…
The kinetics of E' centers (silicon dangling bonds) induced by 4.7eV pulsed laser irradiation in dry fused silica was investigated by in situ optical absorption spectroscopy. The stability of the defects, conditioned by reaction with mobile hydrogen of radiolytic origin, is discussed and compared to results of similar…
The photo-luminescence features of Ge-oxygen defect centers in a 100nm thick Ge-doped silica film on a pure silica substrate were investigated by looking at the emission spectra and time decay detected under synchrotron radiation excitation in the 10-300 K temperature range. This center exhibits two luminescence bands…
This work reports on high resolution photoelectron spectroscopy for the valence band of Co 2 Mn 1− x Fe x Si ( x = 0,0.5,1) excited by photons of about 8 keV energy. The measurements show good agreement with calculations of the electronic structure using the LDA + U scheme. It is shown that the high energy spectra rev…
This work reports about electronic structure calculations for the Heusler compound Co$_2$FeAl$_{1-x}$Si$_x$. Particular emphasis was put on the role of the main group element in this compound. The substitution of Al by Si leads to an increase of the number of valence electrons with increasing Si content and may be see…
Growth of vertical epitaxial Si(100) nanowires on Si(100) substrates is demonstrated (see figure) using a combination of an anodic aluminum oxide template, catalytic Au particles embedded in nanopores directly on the Si substrate by using electroless deposition, and vapor–liquid–solid growth using SiH4. HF acid treatm…
Sol-gel processing is well-known to be a powerful technique for designing materials for optical applications. Here, some recent applications of functionalized sol-gel coatings in optics are briefly reviewed. Lanthanide-doped oxide nanocrystals form a new promising class of nanophosphors allowing the easy sol-gel prepa…
In situ optical absorption spectroscopy was used to study the generation of E' centres in amorphous SiO_2 occurring by photo-induced breaking of Si-H groups under 4.7eV pulsed laser radiation. The dependence from laser intensity of the defect generation rate is consistent with a two-photon mechanism for Si-H rupture,…
Deliberations in the National Seminar held on 9-10 February, 2007 at Saha Institute of Nuclear Physics, Kolkata, INDIA
We report the deposition of thin Co$_2$FeSi films by RF magnetron sputtering. Epitaxial (100)-oriented and L2$_1$ ordered growth is observed for films grown on MgO(100) substrates. (110)-oriented films on Al$_2$O$_3$(110) show several epitaxial domains in the film plane. Investigation of the magnetic properties reveal…
Polycrystalline samples of the Heusler compound Co 2 TiSn have been prepared and studied using bulk techniques (x-ray diffraction and magnetization) as well as local probes ( 119 Sn Mössbauer spectroscopy and 59 Co nuclear magnetic resonance spectroscopy) in order to determine how disorder affects the half-metallic be…
The passivation by diffusing H2 of silicon dangling bond defects (E' centers, induced by laser irradiation in amorphous SiO_2 (silica), is investigated in situ at several temperatures. It is found that the reaction between E' center and H_2 requires an activation energy of 0.38eV, and that its kinetics is not diffusio…
A simplified polycrystalline model (the so-called RL model) is proposed to simulate the anisotropic viscoplastic behavior of metallic materials. A generic method is presented that makes it possible to build a simplified anisotropic material texture, based on the principal features of the pole figures. The method is ap…
INTRODUCTION: Cardiovascular disease, including coronary artery and peripheral vascular pathologies, is the leading cause of mortality in the United States and Western countries. There is a pressing need to develop small-diameter vascular vessels for bypass surgery and other vascular reconstructive procedures. Tissue…
Fine particles of cobalt ferrite were synthesized by the sol?gel method. Subsequent heat treatment at different temperatures yielded cobalt ferrites having different grain sizes. X-ray diffraction studies were carried out to elucidate the structure of all the samples. Dielectric permittivity and ac conductivity of all…
In this paper, results of ab initio band structure calculations for A 2 BC Heusler compounds that have A and B sites occupied by transition metals and C by a main group element are presented. This class of materials includes some interesting half-metallic and ferromagnetic properties. The calculations have been perfor…
The focusing of electric current by a single p-n junction in graphene is theoretically predicted. Precise focusing may be achieved by fine-tuning the densities of carriers on the n- and p-sides of the junction to equal values. This finding may be useful for the engineering of electronic lenses and focused beam splitte…
O controle dos ciclos térmicos, nos tratamentos térmicos de têmpera e revenido, nos aços inoxidáveis martensítico do tipo 13Cr5Ni0,02C, é essencial para se obter boa resistência mecânica associada à resistência à corrosão, principalmente em equipamentos para a extração de petróleo. Corpos-de-prova foram austenizados p…
In this work, the geometry effect on the thermal shock behaviour of a nine layered Al2O3- 5%tZrO2/Al2O3-30%mZrO2 ceramic fabricated by slip casting has been studied. A finite element model has been used to estimate the magnitude and location of the maximum thermal stresses in the layered material as well as the influe…