Materials Literature
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The biocompatibility of ethylene-vinyl acetate copolymer (EVAc), polyethylene (PE), and polyaniline (PANi) films in the emeraldine (EM), nigraniline (NA) and leucoemeraldine (LM) intrinsic oxidation states were assessed through subcutaneous implantation into male Sprague-Dawley rats beneath the dorsal skin, for a peri…
Monolithic Ka-band phase shifter circuit that employs voltage tunable BaSrTiO/sub 3/ (BST) parallel plate capacitors is presented here. The circuit is capable of continuous 0/spl deg/-157/spl deg/ phase shift at 30 GHz with an insertion loss of only 5.8 dB and return loss better than 12 dB. In addition to promising lo…
The interactions between PEO-based templates and metallic centres are key in the synthesis of mesostructured materials. In low-water-content media, strong chelation between metal centres and the non-ionic polar heads leads to polymer unfolding, and thus to worm-like phases. Larger quantities of water and acid added to…
In this paper, the classical Preisach independent domain model is used to capture the essential characteristics of hysteresis nonlinearity in electromagnetic (EM) actuators made of soft ferromagnetic material. Experimental results demonstrate its ability to accurately model electromagnetic hysteresis for variations in…
The cure kinetics of four epoxy/amine systems including commercial RTM6 and F934 resins have been investigated under both isothermal and dynamic curing conditions. Differential Scanning Calorimetry (DSC) was the thermoanalytical technique used to determine the cure kinetics of these resin systems. The complexity of th…
A review of recent developments in the applications and actions of intumescent fire-retardance is given. An attempt has been made to classify the main systems of importance such as melamine, ammonium polyphosphate, melamine phosphate, pentaerythritol phosphate, sodium silicate, vermiculite, expandable graphite and mic…
This paper is concerned with the processes of thermal degradation of nylon 6 and nylon 6,6, which lead to crosslinking and the production of involatile char. The techniques used in this study include thermogravimetric analysis (TG), differential scanning calorimetry (DSC), hot-stage Fourier transform infrared spectros…
The growing use of secondary electron imaging in the scanning electron microscope (SEM) to map dopant distributions has stimulated an increasing interest in the mechanism that gives rise to so-called dopant contrast. In this paper a range of experimental results are used to demonstrate the wide applicability of the te…
In the present study, the processing and the mechanical properties of new thermoset nanocomposites prepared from aqueous suspensions of microcrystalline cellulose fillers and epoxy are described. The nature of cellulose fibers, which display a large aspect ratio and the ability to associate by means of H-bonds implies…
The connection between hysteresis and thermal relaxation in magnetic materials is studied from both the experimental and the theoretical viewpoint. Hysteresis and viscosity effects are measured in Finemet-type nanocrystalline materials above the Curie temperature of the amorphous phase, where the system consists of fe…
The magnetic properties of ${\mathrm{Li}}_{x}{\mathrm{Ni}}_{1\ensuremath{-}x}\mathrm{O}$ compounds with x ranging between 0.4 and 0.49 are investigated. Magnetization and ac susceptibility measured at temperatures between 2 K and 300 K reveal a high sensitivity to x, the excess lithium concentration. We introduce a pe…
Using first-principles calculations based on a variational density functional perturbation theory, we investigate the lattice dynamics of solid solutions of barium and strontium titanates. Averaging the information available for the related pure compounds yields results equivalent to those obtained within the virtual…
A summary of the work recently carried out on the morphotropic phase boundary (MPB) of PZT is presented. By means of x-ray powder diffraction on ceramic samples of excellent quality, the MPB has been successfully characterized by changing temperature in a series of closely spaced compositions. As a result, an unexpect…
The insulating state of matter is characterized by the excitation spectrum, but also by qualitative features of the electronic ground state. The insulating ground wavefunction in fact: (i) displays vanishing dc conductivity; (ii) sustains macroscopic polarization; and (iii) is localized. The idea that the insulating s…
The ppk gene encodes polyphosphate kinase (PPK), the principal enzyme in many bacteria responsible for the synthesis of inorganic polyphosphate (polyP) from ATP. A null mutation in the ppk gene of six bacterial pathogens renders them greatly impaired in motility on semisolid agar plates; this defect can be corrected b…
Most immiscible polymer blends are produced by melt compounding in extruders. The melting and mixing process can generate morphologies ranging from disperse drops to fibers to lamella to cocontinuous structures. Controlling these morphologies is critical to performance of the final blend. This paper reviews recent res…
A study of the exposure of SiC at 1200°C and high water‐vapor pressures (1.5 atm) has shown SiC recession rates that exceed what is predicted based on parabolic oxidation at water‐vapor pressures of less than or equal to ∼1 atm. After exposure to these conditions, distinct silica‐scale structures are observed; thick,…
The heats of combustion for 49 commercial and developmental polymers of known chemical structure were determined using an oxygen bomb calorimeter according to standard methods. The experimental results were compared with thermochemical calculations of the net heat of combustion from oxygen consumption and the gross he…
Abstract. We study the structural and thermodynamic properties of a model of point particles interacting by means of a Gaussian pair potential first introduced by Stillinger (Stillinger F H 1976 J. Chem. Phys. 65 3968). By employing integral equation theories for the fluid state and comparing with Monte Carlo simulati…
The columnar mesomorphism of triphenylene-, phthalocyanine-, tetraazaporphyrin- and porphyrin-based compounds is briefly reviewed and the potential use of this particular supramolecular structure for charge-conducting devices is discussed. Suitably substituted triphenylenes exhibit ideal material properties for photoc…