Materials Literature
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The crystallographic structure of a large class of ABX 3 compounds can be characterised by the stacking sequences of face- and corner-sharing BX 6 -octahedra chains on a hexagonal lattice. Many different polytypes described by this type of stacking have been observed in these and related materials. An axial Ising-type…
Abstract Thermal degradation of polychloroprene under nitrogen, especially at the initial stages, has been studied by using 1 H‐NMR, 13 C‐NMR and FT–IR spectroscopy. A model polymer of low molecular weight ( M n = 6300) was prepared to avoid gelation during degradation. None of isomerized 1,2 unit has been found in th…
Abstract Sheets were cast by extruding polypropylenes (PP) which contained γ‐quinacridone, a β‐crystal nucleator, at levels of 0–10 ppm using a 30 mm ϕ extruder with a T‐die at extrusion temperatures of 200–260°C and chill roll temperatures of 30–90°C. The influences of raw resin characteristics such as γ‐quinacridone…
Abstract Solvent extraction followed by DSC, optical microscopy, and transmission electron microscopy show morphological evidence of molecular segregation for binary mixtures of poly(ethylene oxide)s (PEO). Two segregation types, namely microscopic and macroscopic segregation, have been found. A special etching method…
Abstract Polystyrene was crosslinked in either 1,2‐dichloroethane or carbon tetrachloride in the presence of aluminum chloride. Apparently, the reactions involve Friedel–Crafts substitution of phenyl ring with CH 2 CH 2 Cl or CCl 3 groups, which than participate in crosslinking, giving CH 2 CH 2 or CCl 2 , CCl, and C…
Abstract The glass transition temperature T g of propylene glycol (PG) and poly(propylene glycols) (PPGs) of molecular weight up to 4000 has been measured by differential scanning calorimetry, and the activation energy and change in heat capacity Δ C p have been determined in the glass transition range. The activation…
Abstract Differential scanning calorimetry (DSC) has been used to study the crystallization kinetics and thermal characteristics of poly(aryl‐ether–ether‐ketone) (PEEK) samples heated under a variety of conditions. Samples were heated in nitrogen and air at temperatures between 380 and 420°C for times up to 120 min. T…
Abstract The fracture toughness of commercial linear low‐density polyethylenes (LLDPE) has been found to be extraordinarily high relative to commercial low‐density (LDPE) and high‐density (HDPE) polyethylenes in previously reported investigations. The present investigation shows that this extraordinary fracture toughn…
It has now been established that paracrystals are the 'building blocks' of many materials including polymers, biological materials, colloids, molten metals and alloys, and catalysts. The concept of paracrystallinity and the main equations which are needed for the practical application of the theory to X-ray, neutron a…
For the N-V centre in type Ib diamond the optical detection of spin coherence in the 3 A state is reported. The 3 A-state lifetime is studied as a function of the light intensity used for the optical excitation of the N-V centre by means of spin-locking experiments. The shortening of the lifetime at higher excitation…
Diamond may be grown at low pressures where it is the metastable form of carbon. Recent advances in a wide variety of plasma and electrical discharge methods have led to dramatic increases in growth rates. All of these methods have certain aspects in common, namely, the presence of atomic hydrogen and the production o…
Luminescence measurements (photo-, X-ray-induced and thermo-), ionic thermocurrent and optical absorption data are presented on CaF2 doped with Ce and with Mn. The purpose of the study is to examine the processes of energy storage in this material following irradiation, and the subsequent release of this energy in the…
Low-frequency (≈︁ 1 Hz) internal friction associated with the martensitic transformation in NiTi, is systematically investigated under diverse heating and cooling rates T. The main contribution to the internal friction is due to transistory phenomena which decrease to zero with T. It is shown that the transitory inte…
Bulk dislocations in cubic and tetragonal BaTiO3 are analysed by TEM. Dislocations with Burgers vectors of the type b = a{100} lying along {010} directions are found in stoichiometric material whereas 72° dislocations are predominant in non stoichiometric material. Stacking faults (extended compositional defects in th…
The magnetic hysteresis loops for sintered multiphase Sm(Co0.68Cu0.08–Fe0.22Zr0.02)7.6 permanent magnets are investigated in the whole ferromagnetic temperature range between 10 K and Tc=1070 K. The measured temperature and field dependence of the coercive field is analysed within the framework of theoretical results…
The NMR and EPR measurements of a quasi-one-dimensional conductor β-Pb x V 2 O 5 ( x =0.18, 0.33, 0.37, 0.44) were carried out at temperatures between 12 K and 360 K. The evidence of a spin-singlet ground state was obtained from the temperature dependence of 51 V Knight shift for x =0.18. The observed spin susceptibil…
The polarization reversal process is investigated on the basis of the crystal structure accurately determined by X-ray structure analysis at 170°C in the paraelectric phase. It is concluded from the anisotropic character of the atomic thermal vibrations that polarization reversal is achieved by rotation of the NO 2 ra…
We present kinematical calculations of the diffraction patterns from domain-wall systems on a hexagonal substrate lattice. Diffraction-peak positions and intensities are calculated for the (\ensuremath{\surd}3\ifmmode\times\else\texttimes\fi{}\ensuremath{\surd}3)R30\ifmmode^\circ\else\textdegree\fi{} commensurate-to-i…
The transmission properties of a multilayered medium consisting of $N$ nonlinear slabs are studied. A general characteristic matrix formalism is applied to obtain the power dependence of the transmission coefficient. As an application, a nonlinear Fibonacci multilayer with as many as 55 and 233 nonlinear slabs is cons…
The electronic and structural properties of electrochemically synthetized five poly membered heterocycles [polypyrrole (PP), poly-N-methylpyrrole (PNMeP), polythiophene (PT), polybithiophene (PBT), and poly-3-methylthiophene (PMeT)] in their doped conducting and undoped semiconducting states have been determined by x-…