Materials Literature
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Abstract Compounds of natural rubber, styrene‐butadiene rubber, and butadiene rubber are vulcanized at different temperatures and the crosslink density and physical properties of the vulcanizates are compared. It is found that for each compound there is an optimum vulcanization temperature which results in the best co…
Abstract A heretofore uninvestigated approach to the production of cellulose acetate, the acetylation of whole wood pulp with subsequent isolation of the cellulose derivative by differential solubility, is described. The mechanical pulp used was produced by refining aspen wood chips with a disc refiner. Two convention…
Abstract Light‐induced yellowing of extruded rigid poly(vinyl chloride) formulations containing 0, 2.5, and 5 phr of titanium dioxide under exposure to monochromatic light was studied. Both photoyellowing and photobleaching were observed as wavelength‐dependent phenomena in the range of 280–500 nm. Action spectra for…
Abstract Linear low density polyethylene (LLDPE) was reinforced with different wood fibers, aspen chemithermomechanical pulp (bleached and unbleached), and other commerical wood pulps. Silane coupling agents A‐172, A‐174, A‐1100, and polymethylene polyphenyl isocyanate were used to improve the bonding between the fibe…
The fabrication of a miniature low power/high voltage thermoelectric convertor is described. The device which has arisen out of a requirement of the British gas industry for an autonomous source of electrical power for use in consumers' gas monitoring systems, generates fractions of a microwatt at several volts.
A phenomenological theory has been used to calculate the minimum thermal conductivity for 17 alkali halides with the NaCl structure in the temperature range 1-1200 K. The shortest mean free path has been chosen to be either the nearest-neighbour distance or the phonon wavelength. The calculations show that minimum the…
Grain boundary strengths are estimated experimentally for various Al2O3 structures. It turns out that grain boundary strength at room temperature is strongly affected by viscose relaxation processes proceeding during cooling the sintered structures. The results are used to discuss associated macroscopic mechanical pro…
Accurate dispersion relations have been used for the first time in a calculation of the volume dependence of the thermal conductivity in 16 alkali halides with the NaCl structure. Phonon dispersion relations have been calculated throughout the whole first Brillouin zone for different values of the lattice constant. Th…
Dielectric properties of ferroelectric Pb(Fe 1/2 Nb 1/2 )O 3 ceramics prepared using alkoxides were measured in the temperature 30-150 degrees C. The permittivity shows a broad maximum at the transition temperature T t and quadratic temperature dependence at temperatures above T t . The well saturated polarisation-ele…
Results are reported for the magnetic transitions in quasi-binary CeFe2 alloys with substitutions of Al or Mn on the Fe sites and substitutions of Y or U on the Ce sites. The transitions have been studied by magnetic susceptibility and electrical resistance measurements, and comparisons are made with previous work inv…
The influence of growth temperature on the interfacial abruptness of strained Ge layers, a few monolayers thick, embedded in Si has been studied using Raman spectroscopy to identify the presence of GeGe and GeSi bonds and medium energy ion scattering to characterize the spatial extent of the layers. Atomically sharp i…
Magnetoelastic measurements are performed in metallic glasses of composition (Fe0.79Co0.21)75+x. Si15−1.4xB10+0.4x (x = 0, 2, 4, 6, 8, 10) by means of the resonance-antiresonance method. High values of k (magnetoelastic coupling coefficient) and of the ΔY effect are observed in some compositions, reaching 0.7 for k an…
We report on experimental evidence of the important role of phonon broadening in very small CdSSe crystallites. At low temperature, spectral hole burning is observed. These results are in agreement with the special conditions of quantum confinement and with the polar character of this semiconductor.
Synthetic diamonds that are grown using nickel or a nickel alloy as the solvent-catalyst contain 1.40 eV centres which are strongly segregated in the (111) growth sectors. Absorption and cathodoluminescence measurements made using polarising optics show that the dipole moment of the centre is preferentially aligned wi…
The optical parameters (namely, the complex dielectric tensor and refractive indexes) of sodium nitroprusside dihydrate (SNP), ${\mathrm{Na}}_{2}$[Fe(CN${)}_{5}$NO]\ensuremath{\cdot}2${\mathrm{H}}_{2}$O (orthorhombic, space group ${D}_{2h}^{12}$) in the infrared (ir) region 1550--2250 ${\mathrm{cm}}^{\mathrm{\ensurema…
The diffuse x-ray scattering surrounding satellite reflections caused by charge-density waves has been measured at two different temperatures and analyzed in terms of phason scattering. From this analysis, the phason velocity has been obtained for all directions of propagation.
Simultaneous electron paramagnetic resonance (EPR) and optical absorption studies were carried out at room temperature in a Ge-doped silica fiber-optic waveguide following in situ ultraviolet (UV) irradiation with 254-nm (4.88-eV) photons. We have observed that the UV-induced EPR is directly correlated with the UV-ind…
The one-electron energy spectrum of a Penrose tiling lattice in a magnetic field is studied with a tight-binding Hamiltonian. We show the following remarkable results characteristic of a Penrose lattice. (1) The density of states in a magnetic field has a central peak with zero width at zero energy. It is shown that t…
Abstract The oxidative degradation of polybutadiene–styrene–acrylonitrile (ABS) copolymer was extensively investigated. Three factors were studied: the influence of ageing temperature on the rate of the oxidation of the copolymer; the efficiency of β‐carotene as chain breaking antioxidant; and the effect of butadiene…
Abstract Three vinyl monomers, 2,4,6‐trimethoxystyrene, 4‐( N,N ‐dimethylamino)styrene, and N ‐methyl‐2‐vinylpyrrole, were synthesized via the Wittig reaction from the corresponding aldehyes. These monomers were homopolymerized by radical polymerization using α,α′‐azoisobutyronitrile (AIBN) as initiator at 60°C. The r…