Materials Literature
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Abstract The ferritic steels used for reactor pressure vessels undergo a marked transition from ductile to brittle fracture behaviour over a relatively narrow temperature range. For most unirradiated mild steels the ductile to brittle transition temperature (d.b.t.t.) is between — 50° and 20 °C. The process of irradia…
We have discovered a new form of Fr\'eedericksz transition in which uniform splay distortion is replaced by a complex periodic twist-splay pattern having a lower critical field than that for uniform splay. Experimental evidence is presented along with an exact calculation of both the critical field and the initial for…
We report the observation of an order-disorder transition in the semiconductor strained-superlattice system GeSi/Si, which doubles the lattice periodicity in a $〈111〉$ direction. This phenomenon may be representative of a class of order-disorder transitions in strained-semiconductor systems, even when the lattice mism…
The dispersion of the nonlinear susceptibilities of Ar, ${\mathrm{N}}_{2}$, and ${\mathrm{O}}_{2}$ have been measured for wavelengths from 700.0 to 457.9 nm. A comparison is made with phenomenological models used in the literature.
Yimengite is a new species of mineral discovered in Shandong Province in 1980, with crystal chemical formula K(Cr, Ti, Fe, Mg, Al, Si)12O19. It belongs to hexagonal system, and its cell parameters α 0=5.857 and c 0=22.940. 749 separate diffraction intensities of crystal were collected on RASA=IIS auto-four-circle sing…
The y-expansion as introduced by Barboy and Gelbart is applied to a system of hard ellipsoids-of-revolution. The expansion is truncated after the third order term yielding an approximate theory requiring the second- and third-virial coefficients as inputs. As the third virial coefficient is not known analytically, num…
The temperature dependence of the infrared reflectivity spectra of NaNO 3 is reported in the whole ordered phase, from 10 to 549K. Reflectivity spectra from 5 to 600 cm -1 , are fitted with a model of the factorised form of the dielectric function including the relaxation mode. The temperature dependence of the infrar…
Non-uniform uniaxial nematics systems are discussed using the Landaude Gennes and Frank formalisms. These formalisms are compared and extended in order that the description they provide be consistent. It is then possible to treat the spatial dependence of the main order parameter Q(r) and the local biaxiality P(r) ind…
We present the results of Monte Carlo simulations on a system of hard ellipsoids of revolution with length-to-breadth ratios a/b = 3, 2·75, 2, 1·25 and b/a = 3, 2·75, 2, 1·25. We identify four distinct phases, viz. isotropic fluid, nematic fluid, ordered solid and plastic solid. The coexistence points of all first ord…
The influence of thickness errors and boundary imperfections on the performance of a multilayer x-ray mirror is discussed and it is shown that both can be obtained separately from a measured reflectivity curve at a short x-ray wavelength. Multilayers have greatly reduced scattering compared to single films, and for th…
Soon after the discovery of x-rays and their property of constructive interference scattering (diffraction) by solids resulting from the ordered array of atoms forming the solids, it was proposed that man-made (synthetic) layered structures might extend the range of utility of this phenomena into spectral domains not…
It is shown that a quartic orientational free energy leads to long-range icosahedral bond-orientational order which, through a coupling with a translational order parameter, stabilizes the icosahedral quasicrystalline phase. The bond-orientational order selects the wave vectors which point into vertices or faces of an…
The epitaxial growth of a Lennard-Jones system is studied as a function of substrate temperature ${T}_{s}$ and deposition rate. For all substrate temperatures the growth is into well-ordered layers. Layers become fully completed at intermediate ${T}_{s}$. At very low ${T}_{s}$ the layers contain defects and voids; how…
1 Vieillissement physique par absorption d'eau 1.1 Hydrophilie d'un polymère en relation avec sa structure 1.2 Plastification par l'eau 1.3 Endommagement par gonflements différentiels 1.4 Autres conséquences physiques de l'absorption d'eau 2 Vieillissement chimique en présence d'ea
X-ray powder diffraction results for various hydrides Tm 6 Mn 23 H x and Er 6 Fe 23 H x are reported and included in an extensive plot of hydride-cell volume V hydride against host-cell volume. All tetragonal hydride phases identified to data are observed to satisfy x>9, V hydride <1.883(5) nm 3 and c 0 >a 0 . It is d…
Abstract Aldonitrones are effective melt stabilizers for polypropylene, the most effective being benzaldonitrones containing a partially hindered 4‐hydroxy group in the aromatic ring. They form nitroxyl radicals in the polymer during processing, and these and the related hydroxylamines are believed to be involved in a…
Soxhlet-type leaching experiments were carried out for 200 days and the leaching solutions analyzed by inductively coupled plasma spectroscopy and atomic absorption spectroscopy. The data of the solution analysis and the results of our previous study on the surface layers revealed the fact that elements in the waste g…
The dual field effect on the relaxation time of the liquid-crystal BDH-E7 has been analyzed and demonstrated experimentally by using static magnetic and pulsed optical fields. The novelty of this effect is in the use of a strong external field to accelerate the molecular relaxation process. An improvement factor on de…
The catastrophic growth of unstable thermoplastic shear following the transition from homogeneous deformation to heterogeneous localized deformation through distributed shear banding is studied through approximate analytic and computational methods. The calculations provide expressions for shear-band widths, spacing,…
L'enthalpimétrie par réaction directe dans les systèmes silicatés n'est pas possible. La méthode de dissolution qu'il faut alors employer engendre une erreur importante vis-à-vis des faibles énergies mises en jeu dans l'effet alcalin mixte ici étudié. Nous montrons cependant que les composés silicatés liquides comport…