Materials Literature
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The author investigates the temperature effects of PM (permanent magnet) motors using neodymium magnets on the torque production capability and on the efficiency of the motor. When PM motors are designed to operate in a wide temperature range, the reversible demagnetization of the neodymium magnets with temperature an…
A strategy for finding transition paths connecting two stable basins is presented. The starting point is the Hamilton principle of stationary action; we show how it can be transformed into a minimum principle through the addition of suitable constraints like energy conservation. Methods for improving the quality of th…
Eutectic two-phase cells, also known as eutectic colonies, are commonly observed during the solidification of ternary alloys when the composition is close to a binary eutectic valley. In analogy with the solidification cells formed in dilute binary alloys, colony formation is triggered by a morphological instability o…
Angle is more important than diameter: (n,n) Single-walled carbon nanotubes (SWCNTs; see picture) are less reactive than fullerene towards exohedral addition reactions. The reactivity of (n,n) SWCNTs towards sidewall addition reactions depends on the pyramidalization angles of the tube C atoms. Even with the same diam…
Bulk and thin film specimens of AgB2 were prepared. The bulk pellets were obtained from the powders of the constituents and the films were produced by cosputtering and sequential sputtering. The specimens were annealed and subjected for X-ray and Auger analysis. Preliminary results seems to indicate that AgB2 is an in…
We report a detailed study of steplike metamagnetic transitions in polycrystalline $\mathrm{P}{\mathrm{r}}_{\mathrm{0.5}}\mathrm{C}{\mathrm{a}}_{\mathrm{0.5}}\mathrm{M}{\mathrm{n}}_{\mathrm{0.95}}\mathrm{C}{\mathrm{o}}_{\mathrm{0.05}}{\mathrm{O}}_{\mathrm{3}}$. The steps have a sudden onset below a critical temperatur…
We provide a detailed description of a model and its computational algorithm for the secondary electron emission process. The model is based on a broad phenomenological fit to data for the secondary-emission yield and the emitted-energy spectrum. We provide two sets of values for the parameters by fitting our model to…
Alpha-, beta-, gamma-, and delta-MnO(2) single-crystal nanowires/nanorods with different aspect ratios have been successfully prepared by a common hydrothermal method based on the redox reactions of MnO(4)(-) and/or Mn(2+). The influences of oxidant, temperature, and inorganic cation (NH(4)(+) and K(+)) template conce…
The behavior of the O 2 | HO 2 − redox couple at equilibrium on a commercial uncatalyzed carbon-polytetrafluoroethylene (PTFE) oxygen-diffusion electrode, fed with O 2 partial pressures between 0.21 and 1.0 atm, has been studied by electrochemical impedance spectroscopy. Measurements have been made in the open-circuit…
Reducing thickness of thin ferroelectric films typically comes with an apparent degradation of their dielectric and ferroelectric properties. In practice one observes a marked decrease of the linear dielectric constant and of remanent and maximum polarizations which may arise from the presence of passive layers at the…
Four-probe dc measurements were conducted on a polycrystalline material of composition which showed that the conductivity changed linearly with time during the initial stages when the atmosphere was changed from dry air to wet air, or vice versa. In order to analyze this transient conductivity change with time, a mode…
Symmetrical and unsymmetrical benzophenone Schiff bases of bifurcated dipeptides [e.g., Ar2C=N-CHR1- CONH-HNCO-CHR2-N=CAr2] have been synthesized using Boc methodology. These ligands may be regarded as chiral porphyrin mimics because of the alpha-carbons of the amino acids. The Schiff bases function as effective ligan…
Band structure of the metallic (n,n) carbon nanotubes (coefficients n are the indices of the two-dimensional primitive lattice vectors of the graphene lattice) is calculated in terms of a linear augmented cylindrical wave method. The results are used to correlate the minimum direct energy gaps E11 between the conducti…
A procedure to compute analytical second derivatives of the dynamic first hyperpolarizability with respect to vibrational coordinates has been developed and implemented at the time-dependent Hartree-Fock level. Simplifications are obtained by the same techniques as those employed to derive the 2n+1 rule and the interc…
Magnetic-field (B=0–1.5 T) dependent thermoelectric power (TEP) of the Na-doped La0.7Ca0.3−yNayMnO3 (0.0⩽y⩽0.3) system has been studied in the temperature range 80–300 K. X-ray diffraction studies indicate a rhombohedrally distorted perovskite structure of the samples. The observed sharp peak in the resistivity (ρ) ve…
The formation of the collapsed carbon nanotubes (CNTs) in a chemical vapor deposition process is studied by intentionally adding some toxic materials (sodium carbonate, sodium phosphate, and calcium chloride) of the catalyst into the CNTs growth system. The distorted CNTs and fully collapsed CNTs are observed as compa…
We describe a simple method and device design that enables fast in-plane electro-optic modulation in conventional nematic liquid crystal (NLC) devices. When combined with optimized NLC materials, this approach yields rotational speeds of 1°/μs (independent of rotation angle, over a wide range) at a moderately low volt…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTOrdered Conducting Polypyrrole Doped with Sulfopropyl Ether of β-CyclodextrinWei Chen, Xiaobo Wan, Ning Xu, and Gi XueView Author Information Department of Polymer Science, State Key Laboratory of Coordination Chemistry, Nanjing Uni…
A novel method for estimating the refractive index and density of vacuum-deposited molecular glasses was invented. It is based on the analysis of the interference of the light transmitted through film samples. Molar volumes of toluene, ethylbenzene, and propylbenzene in the glass states were thus elucidated. The volum…
The self-diffusivities of high molecular weight polystyrene chains in CO 2 -swollen polystyrene matrices were measured in real time using neutron reflectivity. Bilayer films of hydrogenated and deuterated polystyrene (PS) were prepared on silicon substrates and exposed to compressed CO 2 . The broadening of the interf…