Materials Literature
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Asymmetric biphenyl type polyimides (PI) were prepared by thermal imidization of polyamic acids (PAA) derived from 2,3,3‘,4‘-biphenyltetracarboxylic dianhydride (a-BPDA) and p -phenylenediamine (PDA) or 4,4‘-oxydianiline (ODA). The dynamic mechanical properties of these PIs were compared with those of the isomeric PIs…
Auger electron spectroscopy (AES) and electron energy loss spectroscopy (EELS) in a reflection mode are compared as the methods for phase composition investigation of thin film oxide systems by ion profiling. As an example, the Al/Al2O3/Si and YBa2Cu3O7/CeO2/Al2O3 systems are considered. The adaptation of applied stat…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHybrid Nanoparticles with Block Copolymer Shell StructuresKeith J. Watson, Jin Zhu, SonBinh T. Nguyen, and Chad A. MirkinView Author Information Department of Chemistry, Northwestern University 2145 Sheridan Road, Evanston, Illinois 60208 Cite this: J. Am. Chem. Soc. 1…
The basic formulation of the quantum mechanical/molecular mechanical (QM/MM) methodology is presented. Critical issues related to running a QM/MM calculation are described and the future prospects of this methodology are discussed in detail.
We have grown highly oriented lead zirconate titanate [Pb(Zr, Ti)O3 or PZT] films on oxidized silicon substrates using a thin MgO buffer layer (7–70 nm thick). Ferroelectric nonvolatile memory field-effect transistors (FETs) were successfully fabricated using the metal/PZT/MgO/SiO2/Si structure in conjunction with rad…
A detailed three-dimensional structural analysis of single-walled carbon nanotubes was carried out using a scanning tunneling microscope (STM) operated at room temperature in ambient conditions. On a microscopic scale, the images show tubes condensed in ropes as well as tubes which are separated from each other. For a…
The combined effects of mechanical stress and surface electromigration on the dynamics of transgranular voids in passivated metallic thin films are analyzed based on self-consistent dynamical simulations. Depending on the strength of the electric and stress fields, void morphological instabilities can lead to film fai…
A nematic liquid crystal in cylindrical pores of polycarbonate (Nuclepore) membranes with radii 25--400 nm was studied by dynamic light scattering. The fundamental mode of the orientational fluctuations shows a crossover from bulk behavior, dominated by bulk-elastic constant $K$, to a surface-dominated one, in which t…
We use atom-resolved scanning tunneling microscopy to evidence the formation of carbon atomic chains on the C-terminated $\ensuremath{\beta}\ensuremath{-}\mathrm{SiC}(100)$ surface. These carbon atom lines, which exhibit an extremely high thermal stability (up to $\ensuremath{\approx}1200\ifmmode^\circ\else\textdegree…
Magnetoelastic phenomena correlated with magnetoresistive ones have been investigated for bilayered manganite crystals, ${\mathrm{La}}_{2\ensuremath{-}2x}{\mathrm{Sr}}_{1+2x}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ ( $0.3\ensuremath{\le}x\ensuremath{\le}0.45$), by measurements of the striction parallel and perpendicular to…
The products of laser ablation of graphite in a nitrogen atmosphere have been studied by transmission electron microscopy and electron energy-loss spectroscopy. Using nickel and cobalt as catalyst, single-wall carbon nanotubes can be produced with a yield similar to that obtained in an inert gas. Nitrogen has not been…
The systematic analysis of high-resolution NMR data, bond lengths, and isotropic ${}^{13}\mathrm{C}$ chemical shifts of crystals of squaric acid ( ${\mathrm{H}}_{2}\mathrm{SQ}$) and its deuterated compound ( ${\mathrm{D}}_{2}\mathrm{SQ}$) yields convincing evidence that order-disorder and displacive features coexist a…
The basic formulation of the quantum mechanical/molecular mechanical (QM/MM) methodology is presented. Critical issues related to running a QM/MM calculation are described and the future prospects of this methodology are discussed in detail.
The question on the dominant driving mechanism (displacive or order-disorder) at each structural phase transition of KNbO3 is investigated by means of molecular dynamics simulations. To this purpose, we first develop a shell model by determining its potential parameters in order to reproduce the ferroelectric instabil…
Highly oriented, multiwalled carbon nanotubes were grown on polished polycrystalline and single crystal nickel substrates by plasma enhanced hot filament chemical vapor deposition at temperatures below 666 °C. The carbon nanotubes range from 10 to 500 nm in diameter and 0.1 to 50 μm in length depending on growth condi…
We report the effect of metal-island size variation in nanoparticle-enhanced photodetectors. Nanoparticle size was controlled by varying the deposition and annealing conditions used to produce the metal-island films. Increasing the size of silver-island particles fabricated onto 165 nm thick silicon-on-insulator (SOI)…
The mechanical behavior of multiwalled carbon nanotube/epoxy composites was studied in both tension and compression. It was found that the compression modulus is higher than the tensile modulus, indicating that load transfer to the nanotubes in the composite is much higher in compression. In addition, it was found tha…
The gigantic reduction of the electric resistivity under the applied magnetic field, CMR effect, is now widely accepted to appear in the vicinity of the insulator to metal transition of the perovskite manganites. Recently, we have discovered the first order transition from ferromagnetic metal to insulator in $\rm La_{…
A systematic study of the electronic structure in perovskite manganites is presented. The effective Hamiltonian is derived by taking into account the degeneracy of $e_g$ orbitals and strong electron correlation in Mn ions. The spin and orbital orderings are examined as functions of carrier concentration in the mean-fi…
In this work, we prepared the interpenetrating polymer networks of bismaleimide and polyether-type polyurethane(polyoxypropylene)–crosslinked epoxy (BMI/PU(PPG)–EP IPNs) by employing the simultaneous bulk polymerization technique. The polyurethane (PU)–crosslinked epoxy was identified via infrared (IR) spectra analysi…