Materials Literature
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Abstract The soils over about half of South Africa are developed from sedimentary rocks of the Karoo Supergroup. Some units within the Karoo strata display variations in their mineralogical composition which correlate with fluctuations in the environment of deposition and with palaeotemperature. The former trends are…
This paper addresses the continuum models of solidification of a monocomponent substance, that generalize the classical Stefan problem by incorporating effects of interfacial kinetics. We consider the key planar solidification problem of this sort. The model implies a rigid solid and an incompressible liquid of equal…
Quenched high-temperature-phase MnBi film was successfully obtained by quenching the low-temperature-phase MnBi film in air. The high-temperature-phase has been found to appear below 300°C, which is different from a previously reported result. Its Kerr rotation and Kerr ellipticity spectra have been measured at room t…
Abstract Die Darstellung von pulverförmigem UNb 6 O 16 gelingt durch Festkörperreaktion (1 000°C oder 1 100°C; evakuierte Quarzglasampulle) aus UO 2 , NbO 2 und Nb 2 O 5 (Gemenge 1:2:2). Schwarze Einkristalle sind durch chemischen Transport in einem geringen Temperaturgefälle (1 000°C→990°C; Transportmittel NH 4 Cl) z…
A review is given of our present general classification of the liquid crystals. The liquid crystal structures are divided into two main groups: nematic phases with parallel ordering of the long molecular axes and smectic phases having additional layered structure. An interesting phenomenon is that the liquid crystal p…
Consideration has been given to the possibility of graded laminates based on aluminium and titanium alloys and their composites. In addition to increased toughness, damping, and fatigue crack growth resistance, laminates produced by diffusion bonding may provide a cost effective route to the utilisation of advanced ma…
A study has been conducted to understand and prevent the formation of cracks in alumina‐zirconia‐silica (AZS) refractory blocks during solidification processing. A fundamental approach has been taken, centered on the development of a three‐dimensional mathematical model to predict heat flow and stress generation in fu…
Abstract The orientational states induced upon two‐step biaxially stretching low‐density polyethylene at 25°C have been investigated. A pole figure analysis of the (200), (020), and (002) crystalline planes has been employed to elucidate the evolution of the molecular crystalline orientation as a function of biaxial s…
Composite materials in which the organic host is stiffened by guest particles, are widely used in nature and are produced synthetically by man. Organisms also produce a different type of composite in which the host is a crystal and the guests are macromolecules occluded in an orderly fashion within the crystal. The be…
Abstract Pulverförmige Präparate lassen sich durch Tempern des äquimolaren Gemenges aus UO 2 und Nb 2 O 5 in evakuierten Quarzglasampullen bei 1 100°C darstellen. Einkristalle sind durch chemischen Transport im geringen Temperaturgefälle (1 000°C → 990°C; Transportmittelkombination NbCl 5 /Cl 2 ) zugänglich. UNb 2 O 7…
Dislocations with Burgers vectors b5 = 〈-211111〉 and b3 = 〈10 − 10 − 10〉 in an Al[sbnd]Cu[sbnd]Fe icosahedral quasicrystal (IQC) have been identified for the first time by the defocus convergent-beam electron diffraction method. Unlike the dislocations already found in IQCs, the Burgers vector components of these two…
Sm(OH) 2 NO 3 , was prepared by hydrolysis of the corresponding nitrate, leading to a product which is insoluble in water. IR-spectroscopy showed a comparison with the analogous Gd-compound. The temperature of decomposition to SmONO 3 is below 573 K. The structure was refined by the Rietveld technique in space group P…
Abstract The influence of covalency and bridging ligands on cooperative optical effects in dimers with closely coupled lanthanide ions in insulating crystals and binuclear complexes is theoretically treated. It is shown that there is a specific interaction between Ln 3+ ions (which may be called covalent coupling) in…
Owing to macroscopic electric fields arising from thermal fluctuations of a ferroelectric domain wall, the attraction energy of two parallel walls decays at large distances between the walls (h) as ${\mathit{h}}^{\mathrm{\ensuremath{-}}2}$ with a prefactor that is proportional to T and to a ratio of dielectric constan…
Abstract 1-Phenylethanol, acetophenone, 2,3-diphenylbutane, and ethylbenzene are produced in the (porphinato)manganese(III)-catalyzed reaction of styrene with NaBH4 in aerobic benzene–ethanol. Chloro(5,10,15,20-tetraphenylporphinato)manganese(III) ([MnIIICl(tpp)]) and chloro[5,10,15,20-tetrakis(2,4,6-trimethylphenyl)p…
This paper describes a newly developed measurement and identification technique for synchronous machine parameters. The first part presents a technique to generate periodic broadband power signals with a controllable amplitude spectrum using a classic rectifier bridge. These signals are well suited to measure the freq…
Progress in first-principles surface phonon calculation and multiple scattering phonon cross-section calculation has provided a more complete understanding of the localized vibrational modes on unreconstructed metal surfaces. A discussion of some of the new results is given focusing on how the new information resolves…
The effect of In impurity on the dark and photoconductivity and the optical band gap of amorphous (Se0.7Te0.3)100−xInx has been studied. The activation energy ΔE and the pre-exponential factor σ0(0,T) which appear in the dc conductivity are found to increase with increasing In content. The photocurrent, as a function…
The excitation cross-sections of DyI spectral lines in the 262-363 nm spectrum region have been measured by the extended crossing beams method, recording optical signals from the intersection region. Measurements have been made of 21 optical excitation functions at electron energies varying from the excitation thresho…
The effect of hydrogen gas on the properties of tetrahedral amorphous carbon deposited in a filtered cathodic arc has been investigated. It is shown that hydrogen flow rates of less than 0–05 s.c.c.m. give rise to an increase of 3–4% in the film density and in the sp3 content above that of the non-hydrogenated films.…