Materials Literature
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Polycrystalline CrO2 is shown to exhibit a giant magnetoresistance (GMR) at low temperatures. A rapid decrease in the GMR with increasing temperature is correlated with a decrease in the intergranular resistance. Single-crystal CrO2 is a half-metallic ferromagnet, as the data are interpreted to reflect two types of ch…
The emissions performance of catalytic converters under different conditions of flow distribution was investigated. Computational Fluid Dynamics methods were utilised to model the maldistribution effects of different inlet cones. The effects of maldistribution on ageing, light-off and conversion were investigated usin…
Using ab initio molecular dynamics simulations, we have studied the growth mechanisms of boron-nitride (BN) nanotubes. In the experimental conditions of temperature, the behavior of single-wall BN nanotubes strongly depends on their helicity. Open-ended ``zigzag'' tubes close into an amorphouslike tip, preventing furt…
By lifting an epitaxial thin film off its growth substrate, we directly and quantitatively demonstrate how elastic strain can alter the magnetic and electrical properties of single-domain epitaxial SrRuO3 thin films (1000 Å thick) on vicinal (001) SrTiO3 substrates. Free-standing films were then obtained by selective…
The question of how carbon nanotubes (CNT)—believed to be the strongest filaments—relax under tension has been addressed. A dislocation theory applied to a two-dimensional nanocrystal such as the CNT describes the main routes of mechanical relaxation in this molecular structure: a brittle cleavage or, at high temperat…
A series of polyurethanes based on 2,4-toluenediisocyanate (TDI), with different amounts of 3-chloro-1,2-propanediol (CPDO), have been prepared. The process of thermal degradation was monitored by thermogravimetric analysis (TGA) alone or coupled with infrared spectroscopy (TGA/FTIR) and differential scanning calorime…
A phase diagram of a mixture consisting of nematic and smectic liquid crystals has been calculated self-consistently by combining Flory–Huggins (FH) theory for isotropic mixing and Maier–Saupe–McMillan (MSM) theory for smectic-A ordering. However, the MSM theory can be deduced to the original Maier–Saupe (MS) theory f…
Amorphous poly(propylene oxide), PPO (molecular weights, 425 and ∼106), complexed with NaClO4 salt has ionic conductivities as high as 10−5 S/cm at room temperature. In an attempt to directly study the dynamics of the Na+ ions, (I=3/2) nuclear magnetic resonance (NMR) spin-lattice relaxation times, T1, and spin–spin r…
We describe experiments devised to detect a possible effect of annealing on the vibrational density of states (DOS) in a glassforming polymer with high accuracy from inelastic incoherent neutron scattering. Such an effect could be expected from the argument that annealing changes the behavior of many measured quantiti…
Tussah silk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gain values were obtained with both grafting agents (up to 175%). The extent of homopolymerization was negligible for the MAA graftin…
Polyurethane (PU) anionomers were prepared as aqueous dispersions and as solutions in tetrahydrofuran or absolute ethanol using dimethylol propionic acid (DMPA) as the stabilizing moiety, isophorone diisocyanate, polytetrahydrofuran, and cyclohexane dimethanol. The structure–property relationships were investigated fo…
Direct measurements of the dynamics of photoinduced electrons in AgI, AgI/Ag2S, and AgBr/Ag2S semiconductor colloidal nanoparticles have been performed using femtosecond pump–probe laser spectroscopy. In AgI the transient absorption signal features a laser pulsewidth limited rise followed by a double exponential decay…
The influence of the molecular weight of poly(2,6-dimethylphenylene oxide) (PPO) on the flame retardancy of ethylene–propylene–diene-modified elastomer (EPDM) formulations containing melamine, kaolin, and PPO formulations was studied. The influence of the molecular structures of various char-forming polymers on their…
A systematic model is presented for a free expansion polymer foaming process that includes simultaneous nucleation and bubble growth. An influence volume approach, which couples nucleation and bubble growth, is used to account for the limited supply of dissolved gas. The melt rheology is described using the Larson vis…
We have performed electronic structure calculations of the interaction of potassium and oxygen with graphite (GR), individually and as coadsorbates. We use up to three graphite planes to represent the graphite surface, but we show that the main physics is correctly described by a single graphite layer. At low coverage…
The density of 0.5–3 μm thick vapor-deposited films of water ice were measured by combined optical interferometry and microbalance techniques during deposition on an optically flat gold substrate from a capillary array gas source. The films were of high optical quality with an index of refraction of 1.29±0.01 at 435.8…
Spatiotemporal fluctuations of the local structure in liquid water are studied with the molecular-dynamics simulation. At temperatures around and above the melting point, each molecule alternately goes through the structured period and the destructured period. Lifetime of each period spreads from several hundred fs to…
Soda-lime glass samples have been subjected to both single and double field reversals during electric field assisted - ion exchanges in the temperature range 350-450 C. Changes in refractive index profiles, chemical profiles and surface stress were observed during the exchanges and a comparison has been made with prev…
The low-frequency behaviour of the isotropic elastic modulus and mechanical loss tangent of modified lead titanate ferro-piezoelectric ceramics have been studied by the three-point bending technique. Measurements of these parameters as a function of the temperature were performed in the frequency range of 0.2 to 20 Hz…
This paper presents an experimental study of the coordination number of binary packings by the use of the liquid bridge technique and provides detailed information about the distributed coordination numbers corresponding to different types of contacts between small and large components and their dependence on particle…