Ferroelectric ceramics with a large piezoelectric anisotropy
This review concerns the experimental and theoretical publications devoted to the important problem of the large piezoelectric anisotropy in -based polarized ferroelectric ceramics.
Materials Literature
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Dielectric relaxation spectroscopy of polyethylene terephthalate (PET) films
The dielectric properties of biaxially stretched polyethylene terephthalate (PET) films of thickness and 68% degree of crystallinity were investigated by means of dielectric relaxation spectroscopy in the frequency range Hz and the temperature range C. Differencial scanning calorimetry (DSC), in the range C, was emplo…
<title>Bonding stresses between piezoelectric actuators and elastic beams</title>
A beam with piezoceramic elements bonded to the beam's top and bottom surfaces is investigated. Simple pin-force models allow the user to predict the deformation of the beam very well for the static case. As the pin-force models are simple they are well suited for active control algorithms of such structures. In exper…
Surface modification of polytetrafluoroethylene by Ar+ irradiation for improved adhesion to other materials
A surface of thin square polytetrafluoroethylene (PTFE) samples (1 × 1 × 0.2 cm3) was irradiated with Ar+ at 1 keV with varying ion dose from 5 × 1014 to 1 × 1017 ions/cm2 with and without an oxygen environment. The irradiated surface of the samples was examined by scanning electron microscopy (SEM) for surface textur…
<title>Effect of prestress on the dynamic performace of a Terfenol-D transducer</title>
The performance of magnetostrictive Terfenol-D is highly dependent on the state of the material and in particular on the mechanical prestress. This paper presents an experimental investigation of the effect of prestress on the dynamic performance of a Terfenol-D transducer. The effects of both prestress and magnetic b…
Effect of vinylacetate content on crystallinity and second-order transitions in ethylene?vinylacetate copolymers
Thermal characteristics of ethylene—vinylacetate (EVA) copolymers having vinylacetate contents ranging from 5 to 40 w/w % are studied by differential scanning calorimetry. It is first shown that EVA copolymers having a vinylacetate content lower than 30 w/w % obey the Flory and Burfield theories of copolymer crystalli…
Design of Surfaces for Patterned Alignment of Liquid Crystals on Planar and Curved Substrates
Molecularly designed surfaces formed by chemisorption of alkanethiols on ultrathin films of gold permit control of both the azimuthal and polar orientations of supported nematic liquid crystals (LCs). These surfaces, when patterned, form simple and versatile templates for the fabrication of complex optical structures…
Electronic Structures of Sr_{14-x}Ca_{x}Cu24O41
The electronic structures of Sr_{14-x}Ca_{x}Cu24O41 are calculated within the local density approximation. Around the Fermi energy there exist quasi-one-dimensional bands originated from the ladder and chain layers. The nearest-neighbor inter-ladder hoppings are estimated to be 5--20% of the intra-ladder ones. Possibl…
Biocatalytic Solvent-Free Polymerization To Produce High Molecular Weight Polyesters
Environmentally benign chemical synthesis is a central thrust in the current U.S. research arena. Production of polymers contributes to pollution during synthesis and after use. Thus, the synthesis of a biodegradable plastic by “green” technology could have a real impact. Indeed, such a polymer produced by microorgani…
Interplay between kinetic roughening and phase ordering
We studied interplay between kinetic roughening and phase ordering in 1+1 dimensional single-step solid-on-solid growth model with two kinds of particles and Ising-like interaction. Evolution of both geometrical and compositional properties was investigated by Monte Carlo simulations for various strengths of coupling.…
Thermal Stability of High Temperature Fuels
This paper describes recent results of AF-sponsored research in the thermal stability of high temperature fuels. At temperatures of 550 °C (1000 °F) and above, both thermal -oxidative and pyrolytic deposition are important. A brief discussion of deposition characteristics and mitigation measures is presented.
Charge distribution and optical properties of and F centres in crystals
Results of quantum chemical calculations for the and F centres in cubic and orthorhombic phases of a perovskite ferroelectric are presented and analysed in the light of existing experimental literature. It is shown that one (two) electrons of the and F centres, respectively, are considerably delocalized, even in the g…
Estimating the effective magnetostriction of a composite: A simple model
For a composite consisting of magnetostrictive particles dispersed in a nonmagnetostrictive matrix, a simple, approximate model for the effective magnetostriction, defined as the ratio of the magnetostriction of the composite to that of the magnetostrictive component, is described. The predictions of the model compare…
Ceramic Stationary Gas Turbine Development Program: Fourth Annual Summary
A team led by Solar Turbines Incorporated is conducting a three phase program under the sponsorship of the United States Department of Energy, Office of Industrial Technologies, to improve the performance of stationary gas turbines in cogeneration through the selective replacement of metallic hot section components wi…
A Probabilistic Approach to Aircraft Turbine Rotor Material Design
A probabilistic design code is being developed for high energy disks and rotors used in aircraft gas turbine engines. This code is intended to augment, not replace, the current safe-life approach to the design of these critical components. While the code will ultimately be applicable to a range of disk alloys, initial…
Low Energy Properties of(n,n)Carbon Nanotubes
According to band theory, an ideal undoped $(n,n)$ carbon nanotube is metallic. We show that the electron-electron interaction causes it to become Mott insulating with a spin gap. More interestingly, upon doping it develops superconducting fluctuations.
Strain stabilized metal–insulator transition in epitaxial thin films of metallic oxide CaRuO3
We report the observation of both metallic and semiconducting behavior in epitaxial thin films of the metallic oxide CaRuO3 deposited under identical conditions. X-ray diffraction studies showed that while semiconducting films with enlarged unit cells were obtained on single-crystal (100) SrTiO3 substrates, metallic f…
Novel Thermal Effects at the First Order Magnetic Phase Transition in Erbium, and a Comparison with Dysprosium
In low temperature studies of ultrapure erbium (and dysprosium) we have discovered unusual thermal effects at the first order magnetic transformation of erbium $(\ensuremath{\cong}19\mathrm{K})$. These include (1) superheating (i.e., the metal is colder after heat has been added to it than before the heat pulse), (2)…
Semidiscrete Variational Peierls Framework for Dislocation Core Properties
The classic Peierls theory of dislocations is critically examined and shown to contain a number of inconsistencies. For narrow core dislocations, as in Si, the classic theory leads to gross overestimation of the barrier to dislocation motion. We present a new, semidiscrete theory which corrects the inconsistencies of…
Effective Medium Theory of the Optical Properties of Aligned Carbon Nanotubes
We present an effective medium theory in order to analyze the reported optical properties of aligned carbon nanotube films [W. A. de Heer et al., Science 268, 845 (1995)]. This methodology is based on photonic band structure calculations and allows treatment of complex media consisting of particles that interact stron…