Materials Literature
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Compared to most tetrahedral semiconductors, the temperature dependence of the absorption edges of the cuprous halides (CuCl, CuBr, CuI) is very small. CuCl and CuBr show a small increase of the gap $E_0$ with increasing temperature, with a change in the slope of $E_0$ vs. $T$ at around 150 K: above this temperature,…
A computer program has been developed for the determination of microstructural parameters from diffraction profiles of materials with cubic or hexagonal crystal lattices. The measured profiles or their Fourier transforms are fitted by ab initio theoretical functions for size and strain broadening. In the calculation o…
The area of periodic mesoporous materials prepared by cooperative assembly in the presence of amphiphile molecules underwent dramatic growth. Among the silica-based materials, many types may be regarded as ordered organic−inorganic nanocomposites. These were divided into five categories: (i) noncalcined amphiphile/sil…
<div class="htmlview paragraph">Diesel vehicles have significant advantages over their gasoline counterparts including a more efficient engine, higher fuel economy, and lower emissions of HC, CO, and CO<sub>2</sub>. However, NOx control is more difficult on a diesel because of the high O<sub>2&…
Electroluminescence (EL) from silicon nanocrystals in Si/CaF2 superlattices grown by molecular-beam epitaxy at room temperature was investigated and compared with that obtained from silicon nanocrystals in Si/SiO2 superlattices. EL spectra exhibited current-tunability, similar to that observed in silicon nanocrystals…
Modulated-temperature calorimetry measurements on the bulk glass-forming Pd40Ni40P20 alloy yielded the complex specific heat response of the deeply undercooled melt near the static glass transition. The imaginary contributions to the complex signal give direct access to the spectrum of slow α-relaxation modes of the u…
A model of switching in antiferroelectric liquid crystals is presented which predicts both helix unwinding in the pretransitional regime and a field induced transition to the ferroelectric state. When the ratio of the coefficients of the quadrupolar and dipolar ordering terms in the bulk free energy expression exceeds…
An epitaxially grown heterostructure consisting of alternating layers of LaMnO3 (8 unit cells) and SrMnO3 (4 unit cells) on a SrTiO3 substrate has been studied by a combination of electron energy-loss spectroscopy (EELS) and high-resolution transmission electron microscopy (HRTEM) on an atomic scale. Excitation edges…
A broad photoluminescence (PL) around 2.6–2.9 eV is known to appear in hydrogenated silicon oxynitride. Although its origin was reported to be Si–N bonds, it is not so clear since the material contains hydrogen. In the present research, we have confirmed that the same PL appears in silicon oxynitride grown by nitridin…
The radiation-induced evolution of the microstructure of Gd2Ti2O7, an important pyrochlore phase in radioactive waste disposal ceramics and a potential solid electrolyte and oxygen gas sensor, has been characterized using transmission electron microscopy and x-ray photoelectron spectroscopy. Following the irradiation…
A mechanical strain applied to a monodomain cholesteric elastomer modulates and eventually unwinds the helical director distribution. There are similarities with the classical problem of an electric field applied to a cholesteric liquid crystal, but also differences. Frank elasticity is of minor importance unless the…
We have used carbon nanotubes to electrically contact a 7 nm gold particle by scanning-probe manipulation. The result was a single-electron transistor showing a periodic modulation of the current as a function of gate voltage for temperatures up to ∼200 K, with the particle responsible for the main features of the ele…
Photosensitive ferroelectric materials exhibit various photoferroelectric phenomena due to the strong influence of nonequilibrium charge carriers on polarization and phase transition. These phenomena are essential for a number of applications including photodriven actuators and sensitive photodetectors. In this work,…
<div class="htmlview paragraph">In the recent years, considerable progress has been achieved in the development of urea-SCR for nonstationary, mobile applications. Main challenges are the reduction of the catalyst volumes and the optimization of the dosing strategy to minimize transient ammonia emissions during…
Delafossite-type CuAlO2 laminar crystals (R3̄m) were prepared through melt by a cooling method from 1423 K. The layer-by-layer structure of the crystal was observed. Because of the structural anisotropy of the crystal, electrical conductivity along the ab plane (σab) was higher than that along the c axis (σc), σab≳25σ…
In this work, we report the magnetocaloric effect (|ΔSM|), around the charge/orbital ordering transition in the mixed valent manganite Nd0.5Sr0.5MnO3. The magnitude of |ΔSM| around this first-order transition is around three times larger than that obtained around the second-order transition (ferromagnetic-metallic-to-…
We report observation of four- and five-photon absorption in the chalcogenide glasses at the telecommunication wavelengths. The nonlinear refractive index is sufficiently large that the optical switching criterion is satisfied.
Electron emission from vertically aligned carbon nanotubes grown by plasma enhanced chemical vapor deposition has been measured using a parallel plate anode and a 1 μm tungsten probe. The field emission characteristics were measured as a function of the nanotube diameter, length, and areal density. It was found that l…
Recent experiments indicate that water molecules adsorbed on carbon nanotube tips significantly enhance field-emission current. Through first-principles density-functional theory calculations we show that the water-nanotube interaction is weak in zero electric field. However, under emission conditions large electric f…
Through Quantum Monte Carlo simulation, we study the biquadratic-interaction model with the SU(2) symmetry in two and three dimensions. The zero-temperature phase diagrams for the two cases are identical and exhibit an intermediate phase characterized by finite quadrupole moment, in agreement with mean-field type argu…