Materials Literature
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Macroporous SiC with a highly ordered pore array was prepared for the first time using low molecular weight SiC preceramic polymers such as polymethylsilane or polycarbosilane by utilizing sacrificial colloidal silica crystalline arrays, as a template which were subsequently etched off after pyrolysis in an argon atmo…
Up to now, electric-field-induced nonlinear conduction in the ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ system (PCMO) has been ascribed to a current-induced destabilization of the charge ordered phase. However, for $x<~0.25,$ a ferromagnetic insulator state is observed, and charge orderi…
Er-doped tin–silicate glass–ceramic composites were synthesized from Si, Er and Sn molecular precursors by following a sol–gel method. Optical spectroscopy and electron microscopy showed that the resulting material is composed of an amorphous silica network that encloses submicrometric SnO2 crystalline clusters. Analy…
The purpose of this two-part article, is first to give an update of recent developments of gradient plasticity as this was advanced by Aifantis and co-workers in the early eighties to address dislocation patterning and shear band problems, and then to elaborate on two specific issues of current interest: size effects…
Abstract Two new sequential poly(ester amide)s (PEAs) derived from 1,4‐butanediol, sebacic acid, and L ‐alanine (PABA8) or glycine (PGBG8) are prepared and characterized. For comparative purposes the related polyesters (PEs) 4,10 and 6,10 are also studied. The calorimetric analysis shows that the inclusion of amino ac…
p -type conducting films of α-BuCu2S2 have been deposited onto glass and KBr substrates, yielding a conductivity of 17 S/cm and a Hall mobility of 3.5 cm2/V s. For a 430-nm-thick film, the optical transparency approaches 90% in the visible portion of the spectrum at 650 nm, and a transparency of 40% extends throughout…
We fabricated an all-perovskite oxide p-n junction comprised of hole-doped (p-) manganite La0.9Ba0.1MnO3 and electron-doped (n-) titanate Sr0.99La0.01TiO3 films. The junction showed good rectifying properties at both room temperature and low temperature in a simple structure without inserting an insulating layer. By o…
Oxide thin films are usually grown on substrates which offer the smallest mismatch with the desired structure of the film. The choice of high-quality substrates with suitable lattice constants is unfortunately very limited. Coherently grown films are therefore always under tensile or compressive in-plane strain. We re…
Since the discovery of Fe–Ni alloys showing low thermal expansion (LTE) in 1896, many Invar alloys have been developed based on magnetovolume effect where negative thermal expansion is induced by magnetic transformation. Herein, we show that the control of stress-induced martensitic transformation due to cold working…
The electron energy-loss near-edge structure (ELNES) at the O K edge has been studied in yttria-stabilized zirconia (YSZ). The electronic structure of YSZ for compositions between 3 and 15 mol % ${\mathrm{Y}}_{2}{\mathrm{O}}_{3}$ has been computed using a pseudopotential-based technique to calculate the local relaxati…
The present paper is devoted to the description of optical absorptions in supported metallic particles smaller than the wavelength of light. The breaking of symmetry brought by the presence of the substrate and by the finite contact angle for the particle leads to a nonhomogeneous local field and allows excitation of…
Nanometer-sized fluorescent particles were successfully synthesized. The nanoparticles have a narrow, tunable, symmetric emission spectrum and a broad, continuous excitation spectrum. They are also photochemically stable. A synchronous fluorescence method was developed for the rapid determination of DNA with functiona…
The molecular self-diffusion coefficients in nematic and smectic-A thermotropic liquid crystals are measured using stimulated-echo-type 2H and 1H pulse-field-gradient spin-echo nuclear magnetic resonance (PGSE NMR) combined with multiple-pulse dipolar decoupling and slice selection. The temperature dependence of the p…
The thermal behavior of Cu2S nanowires has been studied in the presence of N2 and O2. The nanowires are stable in N2 at the highest temperature we have studied (320 °C), but they are oxidized by O2 to Cu2O above 260 °C and to CuO at even higher temperatures. At the highest temperature we have studied (400 °C), the S a…
An atomic force microscope (AFM) has been used to modify the electrical properties of carbon nanotube devices. By applying voltage pulses from a metal-coated AFM tip, electrical breaks (“cuts”) or tunneling barriers (“nicks”) can be created at any point along a tube. These methods are applied to make single tube devic…
The dynamics of macroscopically homogeneous sheared suspensions of neutrally buoyant, non-Brownian spheres is investigated in the limit of vanishingly small Reynolds numbers using Stokesian dynamics. We show that the complex dynamics of sheared suspensions can be characterized as a chaotic motion in phase space and de…
In copper and other face centered cubic metals, high-energy particle irradiation produces hardening and shear localization. Post-irradiation microstructural examination in Cu reveals that irradiation has produced a high number density of nanometer sized stacking fault tetrahedra. The resultant irradiation hardening an…
Calculations of quantum transport in a carbon nanotube transistor show that such a device offers unique functionality. It can operate as a ballistic field-effect transistor, with excellent characteristics even when scaled to 10 nm dimensions. At larger gate voltages, channel inversion leads to resonant tunneling throu…
We study phase separation from a nematic liquid crystal with spatially nonuniform director gradients. Particles of a phase-separated component, which is either an isotropic fluid (silicone oil) or a nonmesogenic photopolymer, accumulate in the regions with the strongest director distortions, thus reducing the overall…
Mn 2+ -doped ZnS nanoparticles and Mn2+-doped ZnS nanoparticles coated with a shell of ZnS were prepared in reverse micelles. Mn2+ emission at 580 nm in the coated nanoparticles was seven times stronger than that in the uncoated ones. Ultraviolet light treatment enhanced the luminescence at 580 nm in the uncoated nano…