Materials Literature
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Single-walled carbon nanotubes are synthesized by chemical vapor deposition of methane at controlled locations on a substrate using patterned catalytic islands. The combined synthesis and microfabrication technique presented here allows a large number of ohmically contacted nanotube devices with controllable length to…
<div class="section abstract"><div class="htmlview paragraph">The daily variation in air temperature is large compared with the temperature changes a short distance below the surface of the ground. In theory, a heat engine can be arranged to produce electricity from this temperature difference. In practice…
We have performed an angle-resolved photoemission study on untwinned PrBa$_2$Cu$_3$O$_7$, which has low resistivity but does not show superconductivity. We have observed a dispersive feature with a band maximum around ($π$/2,$π$/2), indicating that this band is derived from the undoped CuO$_2$ plane. We have observed…
We have studied the chemical potential shift in La$_{2-x}$Sr$_x$NiO$_4$ and the charge ordering transition in La$_{1.67}$Sr$_{0.33}$NiO$_4$ by photoemission spectroscopy. The result shows a large ($\sim$ 1 eV/hole) downward shift of the chemical potential with hole doping in the high-doping regime ($δ\gtrsim$ 0.33) wh…
The dielectric response of many materials exhibits universal behavior in the form of a power law frequency dependence of the ac conductivity. This response is seen in all types of structures both crystalline and amorphous and for all types of polarizing species including dipoles and ions. Here I demonstrate that for i…
Abstract Disordered or ‘glassy’ materials are of significant technological value. Their structure can be investigated by diffraction (neutron, X-ray, electron) techniques. When the available volume is very small (eg thin films, non-homogeneous structures) only electrons are suitable. Cockayne and McKenzie developed a…
In narrow-band conductors a weakly screened Coulomb interelectron repulsion can supress narrow-band electrons’ hopping, resulting in formation of a “frozen” electron phase which differs principally from any known macroscopic self-localized electron state including the Wigner crystal. In a zero-band-width limit the “fr…
A discontinuity wall in smectic A liquid crystals was discussed in M. Kléman, Points, Lines and Walls in Liquid Crystals, Magnetic Systems and Various Ordered Media (J. Wiley. Chichester 1983). Possible solutions describing a twist disclination which terminates the discontinuity wall in an infinite smectic A liquid cr…
The synthesis of meso-tetraphenylporphyrin (TPP) and its application in a solar- energy conversion device are described as an undergraduate laboratory experiment. In the first part of the exercise, a convenient procedure for the synthesis of TPP is presented. In the second section of the experiment, the construction o…
Abstract The electrical properties of SrTiO3 (strontium titanate) ceramics are strongly influenced or even dictated by grain boundary segregation of charged point defects, such as dopant atoms, impurities, vacancies, or self-interstitials. The atomistic structure of the grain boundaries, their energy, and the segregat…
Abstract Quantitative analysis with the electron microprobe analyzer (EMPA) has yielded more accurate results over time as a result of improvements in ZAF and other correction routines, mass absorption coefficients, synthetic pseudocrystals for ultralight elements, computers, software programs, backscattered electron…
Abstract A comprehensive understanding of the relation between structure and properties in nano-materials calls for an extensive knowledge of the adhesion between nanoparticles. Electron diffraction contrast from the stress field caused by adhesion between contacting particles yields a detailed information on surface…
Based on complex electro-optical and dielectric measurements, the processes of low frequency relaxation in PDLC (Polymer Dispersed Liquid Crystals) films have been studied. Experimental data are presented to investigate PDLC structure and its evolution with increase in LC concentration. These results are found to be i…
This chapter contains sections titled: Introduction Experimental Procedures Results and Discussion Conclusions Acknowledgements
The dependence of the cellular (biogenic) and frustule-associated (mineralized) silica content of the diatoms Navicula salinarum and Thalassiosira weissflogii on salinity and aluminium conditions was studied in order to make it possible to manipulate silicification in vitro and maximize it to levels required for physi…
The texture changes during the initial phase of blanching of potatoes, carrots and green peas at different blanching times (0–240 s) and temperatures (85 °C, 95 °C, 100 °C) were investigated. The breaking force (N) was determined by compression or Back extrusion tests with an Instron texture tester. Electronmicroscopi…
A model for rim porosity that takes into account the effect of overpressurization on rim pores is proposed for high-burnup UO2 fuel. It is based on the assumption that all the fission gases produced are retained in rim pores, and the threshold pellet average burnup required for the formation of the rim region is 40 MW…
Tetra(n-butyl)ammonium ds-diacidooxophthalocyaninato(2-)niobates(V) and -tantalates(V), ( n Bu 4 N) cis [M(X) 2 Opc 2- ] (M = Nb, Ta; X = F, Cl, NCS, N 3 ), are obtained by the reaction of cis [M(Cl) 3 pc 2- ] or cis [M(Cl}Opc 2- ] (M = Nb, Ta) with the respective tetra(n-butyl)ammonium salt. ( n Bu 4 N) cis [Nb(F) 2…
Abstract A new CuII-NiII heterodinuclear complex [Cu(PEoxd)Ni(bpy)2](ClO4)2·1/2H2O has been synthesized and its structure determined by single crystal X-ray analysis. Crystal data: space group P21/c with a = 9.226(2) Å, b = 30.857(6) Å, c = 14.241(3) Å, and β = 97.36(3)°, V = 4021(2) Å3, Z = 4. Magnetic measurement in…
A simple double-well potential model is established. It shows that the nature of the low-frequency dielectric constant in ferroelectrics is the additional hopping of the off-center ions in multi-site potential. The co-operative effect causes the fact that the Curie-Weiss law is obeyed. The mechanism of the molecular f…