Materials Literature
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Abstract The polymerizable cationic surfactant, vinylbenzyldimethylethanolammouium chloride (VBDEAC), was synthesized to functionalize montmorillonite (MMT) clay and used to prepare exfoliated polystyrene–clay nanocomposites. The organophilic MMT was prepared by Na + exchanged montmorillonite and ammonium cations of t…
A simple mixture of thiourea and AgNO3 in alkaline solution without any template or substrate, allowed to stand at room temperature, forms a unique self-supported pattern of Ag2S nanorods. The picture shows a scanning electron micrograph of a typical product: a flake of polycrystalline Ag2S with Ag2S nanorods that rad…
Volcanic ash-derived soils have high pH0 and very low cation exchange capacity attributed to their highly reactive colloidal constituents, the short-range-order minerals. Fertility is in doubt unless the effects of positive adsorption sites are masked and the increment of negative charge improved. Laboratory and glass…
The photoluminescence and photostimulated luminescence of Ag and AgI nanoclusters formed in zeolite-Y are studied using fluorescence spectroscopy. The photoluminescence spectra of AgI nanoclusters show emission from both AgI as well as Ag nanoclusters which are present in small amounts in the AgI nanoclusters, while i…
Zeolite β, silicalite-1, ZSM-5, and TS-1 coated spheres have been prepared successfully through layer-by-layer assembly of nanozeolite/polymer multilayers on polystyrene (PS) microspheres, and hollow zeolite spheres have been obtained by removal of the core by calcination. In the adsorption process of nanozeolites ont…
A Cu–Zn–Al precursor (CZA) was synthesized efficiently by coprecipitation of the corresponding cations with sodium carbonate at constant pH and temperature. The starting precursor contained a mixture of two hydroxycarbonate phases: rosasite and a Cu–Zn hydrotalcite-like phase. The thermal decomposition was studied by…
We perform a combination of diffraction and diffusion of neutron and high-resolution x-ray experiments on the ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Ba}}_{x}{\mathrm{TiO}}_{3}$ system as well as dielectric susceptibility and polarization measurements. We show the ${\mathrm{SrTiO}}_{3}$-type antiferrodistortive phas…
It is shown that our multi-high-frequency $(40\ensuremath{-}200 \mathrm{GHz})$ resonant cavity technique yields distortion-free high-field electron paramagnetic resonance (EPR) spectra for single-crystal samples of the uniaxial and biaxial spin $S=10$ single-molecule magnets (SMM's) $[{\mathrm{Mn}}_{12}{\mathrm{O}}_{1…
The radial dependency of the vibrational frequencies of single-wall carbon nanotubes in the G band (1500-1600 cm(-1)) is studied by density functional theory. In metallic nanotubes, a mode with A1 symmetry is found to be significantly softer than the corresponding mode in insulating tubes or graphite. The mechanism th…
We present an exact expression for the frequency-dependent Kohn-Sham exact-exchange (EXX) kernel for periodic insulators, which can be employed for the calculation of electronic response properties within time-dependent (TD) density-functional theory. It is shown that the EXX kernel has a long-wavelength divergence be…
In1-xMnxAs diluted magnetic semiconductor (DMS) thin films have been grown using metalorganic vapor phase epitaxy (MOVPE). Tricarbonyl(methylcyclopentadienyl)manganese was used as the Mn source. Nominally single-phase, epitaxial films were achieved with Mn content as high as x=0.14 using growth temperatures Tg>475 C.…
The effect of grain size, easy magnetization axis and anisotropy constant distributions in the irreversible magnetic behavior of granular alloys is considered. A simulated granular alloy is used to provide a realistic grain structure for the Monte Carlo simulation of the ZFC-FC curves. The effect of annealing and exte…
The intermetallic compound SmMn$_2$Ge$_2$, displaying multiple magnetic phase transitions, is being investigated in detail for its magnetization behavior near the 145 K first order ferromagnetic to antiferromagnetic transition occuring on cooling, in particular for thermomagnetic history effects in the magnetization d…
The initial stages of growth of Ge and Si on the Ge(001) surface are studied and compared to growth on the Si(001) surface. Metastable rows of diluted ad-dimers exist on both surfaces as intermediate stages of epitaxial growth. Unexpectedly, for Ge(001) these rows are found exclusively in the <310> directions, whereas…
Electron-phonon scattering is studied within an effective-mass theory. A continuum model for acoustic phonons is introduced and electron-phonon interaction due to modification of band structure is derived as well as a normal deformation potential. In a metallic nanotube, the deformation potential does not participate…
Field emission energy distribution (FEED) has been measured for undergate-type triode carbon nanotube (CNT) field emitters where the gate electrodes are located underneath the cathode electrodes. The diode-type emission for these CNT emitters was found to follow the Fowler–Nordheim relation, whereas the triode-type em…
A model is proposed for the recent gate voltage VG modulation experiment of a kink-shaped carbon nanotube (NT) Schottky diode [Z. Yao, H. Postma, L. Balents, and C. Dekker, Nature (London) 402, 273 (1999)]. Since larger VG increases both the forward and the reverse turn-on voltages of the diode, we show that: (1) the…
Nanoporous-carbon (NPC) films are grown using physical processes such as low-power pulsed-laser deposition with attenuation of the ablated carbon species kinetic energy attained by using an inert background gas. With room-temperature growth and negligible residual stress, NPC can coat nearly any substrate to any desir…
Room-temperature micro-Raman scattering and temperature-dependent dielectric measurements were carried out on sol-gel-derived ferroelectric Pb1−xLaxTi1−x/4O3 (PLT x=0.05–0.30) thin films. Results indicate that the crystal structure and the electrical properties of PLT films were strongly influenced by the La contents.…
Two novel disc-shaped compounds (1, 2) with strong intramolecular hydrogen bonds were prepared and characterized; compound 2 showed a thermotropic mesophase as characterised by polarized optical microscopy, DSC and X-ray diffraction studies.