Materials Literature
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An improved process is presented to functionalize carbon nanotubes by potassium permanganate with the help of phase transfer catalyst (PTC). The PTC helps to extract potassium permanganate from the solid phase to an organic solvent phase and improves the efficiency of nanotube oxidation. The higher reaction efficiency…
This study describes the relative effect on the permanent magnet characteristics viz. remanence (Br), intrinsic coercivity (Hci), Curie temperature (TC), and rectangularity of the intrinsic demagnetization curve, when Al, Cu, Ga, and Nb are added individually to NdFeB. Each elemental addition causes significant improv…
Organic-inorganic hybrids are an important class of new materials that offer improved thermal and mechanical properties over normal polymers. They may be produced by either the sol-gel route or through the use of inorganic compounds possessing reactive functional groups. Polyhedral oligosilsesquioxanes (POSS) are comp…
We show that one-dimensional topological objects (kinks) are natural degrees of freedom for an antiferromagnetic Ising model on a triangular lattice. Its ground states and the coexistence of spin ordering with an extensive zero-temperature entropy can be easily understood in terms of kinks forming a hard-sphere liquid…
We investigate the fatigue and refreshment by dc-electrical field of the electrical properties of Pt/Pb(Ti,Zr)O$_3$/Pt ferroelectric capacitors. We find an asymmetry in the refreshment, that is, the fatigued state can be refreshed by application of negative high dc-voltage to the top electrode, but no refreshment is m…
We present first-principles calculations of phase coherent electron transport in a carbon nanotube (CNT) with realistic contacts. We focus on the zero-bias response of open metallic CNT's considering two archetypal contact geometries (end and side) and three commonly used metals as electrodes (Al, Au, and Ti). Our ab-…
We use supercell and frozen-magnon approaches to study the dependence of the magnetic interactions in (Ga,Mn)As on the Mn concentration. We report the parameters of the exchange interaction between Mn spins and the estimates of the Curie temperature within the mean-field and random-phase approximations. In agreement w…
We report on the first principles determination of the conductance properties of Buckminster fullerene adsorbed on a gold surface, comparing them with recent Scanning Tunneling Microscopy/Spectroscopy (STM/S) experiments [J.Chem.Phys.116, 832 (2002)]. Our procedure has the two appealing features of being able to eluci…
Graphite nanoparticles, with diameters as small as 2 nm (see picture) can be fabricated by the carbonization of polypyrrole nanoparticles of similar dimensions, which have been prepared by a low-temperature polymerization technique in which a micellar microemulsion acts as a “nanoreactor”. The graphite nanoparticles e…
Nanoshells are mesoscopic particles consisting of a dielectric core coated with a metal shell, in particular gold or silver, of uniform nanometer scale thickness. This topology supports plasmon excitations with frequencies that are sensitively dependent on the relative radii of the nanoparticle's core and shell. The p…
Molybdenum blocks in organic polymers: Bifunctionalized hexamolybdate anions (such as 1) can be selectively synthesized in high yields by using the octamolybdate anion 2 as the starting material. The ion 1 can then be used in the synthesis of the first main-chain-polyoxometalate-containing hybrid polymer.
A ferroelectricity-magnetism-coexisting system, hexagonal $R{\mathrm{MnO}}_{3}(R=\mathrm{Y},$ Lu, and Sc), has been investigated by synchrotron x-ray and neutron powder diffraction measurements. It is found from x-ray diffraction measurements that the ferroelectric polarization originates from the tilting of ${\mathrm…
Abstract The chemistry of vulcanization and its effects on vulcanizate properties are reviewed. Also, the chemistry of the protection of rubber vulcanizates from the effects of oxidation and ozonation is reviewed. © 2002 Wiley Periodicals, Inc. J Appl Polm Sci 87:24–30, 2003
Taming the uncontrollable: The novel heteropolymolybdates, such as the [SeIVMo6O21(O2CCH2NH3)3]2− ion shown, functionalized by amino acids, can be derivatized at two different positions in a controlled manner. In addition, further functionalization of the clusters through the amino groups is possible, thus the 18 new…
We have characterized Zn1−xCoxO (x=0.25) films grown on sapphire (0001) substrates by pulsed laser deposition using various growth conditions to investigate the growth condition dependence of properties of Co-doped ZnO films. The substrate temperature (TS) was varied from 300 to 700 °C and the O2 pressure (PO2) from 1…
The mechanical properties of polycrystalline materials are largely determined by the kinetics of the phase transformations during the production process. Progress in x-ray diffraction instrumentation at synchrotron sources has created an opportunity to study the transformation kinetics at the level of individual grain…
The propagation of waves supported by capacitively loaded loops is investigated using a circuit model in which each loop is coupled magnetically to a number of other loops. Since the coupling is due to induced voltages the waves are referred to as magnetoinductive (MI) waves. The mathematical formulations are mostly a…
In the preparation of polymer/clay nanocomposites, organoclay plays an important role in lipophilizing and dispersing the clay into less polar polymer matrixes. Organic modifiers of various chain lengths were examined in different types of clays, smectite, montmorillonite (MMT), and mica, to prepare their correspondin…
Block copolymer lithography makes use of the self-assembling properties of block copolymers to pattern nanoscale features over large areas. Although the resulting patterns have good short-range order, the lack of long-range order limits their utility in some applications. This work presents a lithographically assisted…
A composite medium consisting of an array of fine wires and split-ring resonators has been previously used to experimentally verify a negative index of refraction. We present a negative refractive index (NRI) metamaterial that goes beyond the original split-ring resonator/wire medium and is capable of supporting a bac…