Ordered Phase (ordered + phase)

Distribution by Scientific Domains


Selected Abstracts


Grayscale Photopatterning of an Amorphous Polymer Thin Film Prepared by Photopolymerization of a Bisanthracene-Functionalized Liquid-Crystalline Monomer

ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010
Hideyuki Kihara
Abstract A method for grayscale photopatterning of an amorphous polymer film derived from a bisanthracene-functionalized liquid-crystalline monomer is developed. Solution photopolymerization of a monomer with two anthracene moieties, one at each end, affords an amorphous polymer. A combination of irradiation with patterned UV light and heating results in photopatterning on thin films prepared from the polymer. On non-irradiated areas of the film, the polymer reverts to the monomer owing to the thermal back-reaction of the anthracene photodimer, forming an ordered phase. On irradiated areas remaining in the amorphous phase, the thermal back-reaction is suppressed. This phenomenon results in a clear contrast and visual images on the film under polarized light. Grayscale photopatterning is also made possible for the solution-polymerized polymer by controlling the intensity of exposure. In addition, rewritable photopatterning can be achieved by melt photopolymerization of the monomer. The new photopatterning is essentially nondestructive because it needs neither image development nor anthracene-excitation light for reading. [source]


Quantum criticality of Ce1,xLaxRu2Si2: The magnetically ordered phase

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2010
Stéphane Raymond
Abstract We report specific heat and neutron scattering experiments performed on the system Ce1,xLaxRu2Si2 on the magnetic side of its quantum critical phase diagram. The Kondo temperature does not vanish at the quantum phase transition and elastic scattering indicates a gradual localization of the magnetism when x increases in the ordered phase. [source]


In-situ high-pressure study of the ordered phase of ethyl propionate

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2007
Roman Gajda
Ethyl propionate, C5H10O2 (m.p. 199,K), has been in-situ pressure-frozen and its structure determined at 1.34, 1.98 and 2.45,GPa. The crystal structure of the new high-pressure phase (denoted ,) is different from phase , obtained by lowering the temperature. The freezing pressure of ethyl propionate at 296,K is 1.03,GPa. The molecule assumes an extended chain s-trans,trans,trans conformation, only slightly distorted from planarity. The closest intermolecular contacts in both phases are formed between carbonyl O and methyl H atoms; however, the ethyl-group H atoms in phase , form no contacts shorter than 2.58,Å. A considerable molecular volume difference of 24.2,Å3 between phases , and , can be rationalized in terms of degrees of freedom of molecules arranged into closely packed structures: the three degrees of freedom allowed for rearrangements of molecules confined to planar sheets in phase ,, but are not sufficient for obtaining a densely packed pattern. [source]


Space group and atomic structure determination of a nano-sized ordered phase derived from a f.c.c. structure in maraging steel 12Cr,9Ni,4Mo,2Cu using transmission electron microscopy

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2003
Ping Liu
The unique properties of maraging steel Sandvik 1RK91 were attributed to unique precipitation: a nano-sized L phase in addition to the quasi-crystalline R, phase, which differs from any precipitation system in conventional maraging steels. The L phase was observed after ageing at either 748 or 823,K. It has flake morphology with dimensions ,100 × 500 × 500,Å. In the present study the structure of the L phase was examined using convergent-beam electron diffraction (CBED), energy-dispersive X-ray analysis (EDX) and high-resolution electron microscopy (HREM). The L phase could be described as Ti19Fe9Mo9Al8Cr5Ni50 or simply M50Ni50 (M = Ti, Fe, Mo, Al and Cr). The L phase is isostructural to FeNi. Its crystal structure was determined to have the ordered structure of the uAu-I type (L10, P4/mmm, a = 3.52, c = 3.63,Å and Z = 2) with two Ni atoms at ½ 0 ½ and 0 ½½, and two M atoms at 0 0 0 and ½½ 0. The crystal structure of the L phase can also be described using a primitive tetragonal cell and lattice parameters: a = 2.49 and c = 3.63,Å, Z = 1. The volume of the primitive tetragonal unit cell is 22.5,Å3 and the density is ,6.98,g,cm,3. The present study has demonstrated the possibility of determining the structure of an extremely small crystal by utilizing the information from CBED, EDX analysis and HREM. [source]


In Situ Characterization of a Nb and Mo Containing , -TiAl Based Alloy Using Neutron Diffraction and High-Temperature Microscopy,

ADVANCED ENGINEERING MATERIALS, Issue 11 2009
Ian J. Watson
Abstract In recent times, novel titanium aluminides containing the bcc , -phase at high temperatures are being developed for improved hot-working capabilities, however, predictions of the phase diagrams are merely uncertain. Here we present in-situ neutron studies, which are particularly sensitive to the atomic disorder in the ordered phases. Complementary laser scanning confocal microscopy is employed for in-situ microstructural investigations. [source]


Phase Relations and Thermal Expansion Studies in the Ceria,Yttria System

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2004
Sandeep V. Chavan
The synthesis, characterization, and bulk and lattice thermal expansions of a series of compounds with general composition Ce1,xYxO2,x/2 (0.0 ,x, 1.0) are reported. The XRD pattern of each product was refined to learn the solid solubility limit and the homogeneity range. The solid solubility limit of YO1.5 in CeO2 lattice, under the conditions of slow cooling from 1400°C, is represented as Ce0.55Y0.45O1.775 (i.e., 45 mol% of YO1.5). The subsequent compositions were biphase. There was no solubility of CeO2 into the lattice of YO1.5. The bulk thermal expansion measurements from ambient to 1123 K, as investigated using a dilatometer, revealed that the ,l (293,1123 K) values, within the homogeneity range, decreased on increased Y3+ content. A similar trend was observed for average lattice thermal expansion coefficient, ,a (293,1473 K), as investigated using high-temperature XRD. No ordered phases were obtained in this system under the used conditions. These studies on Ce1,xYxO2,x/2 (0.0 ,x, 1.0) system can be used to simulate the phase relation and thermal expansion behavior of Pu1,xYxO2,x/2 (0.0 ,x, 1.0), because CeO2 is widely used as a surrogate material for PuO2. [source]


Cobalt Coordination and Clustering in ,-Co(OH)2 Revealed by Synchrotron X-ray Total Scattering

CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2010
James
Abstract Structures of layered metal hydroxides are not well described by traditional crystallography. Total scattering from a synthesis-controlled subset of these materials, as described here, reveals that different cobalt coordination polyhedra cluster within each layer on short length scales, offering new insights and approaches for understanding the properties of these and related layered materials. Structures related to that of brucite [Mg(OH)2] are ubiquitous in the mineral world and offer a variety of useful functions ranging from catalysis and ion-exchange to sequestration and energy transduction, including applications in batteries. However, it has been difficult to resolve the atomic structure of these layered compounds because interlayer disorder disrupts the long-range periodicity necessary for diffraction-based structure determination. For this reason, traditional unit-cell-based descriptions have remained inaccurate. Here we apply, for the first time to such layered hydroxides, synchrotron X-ray total scattering methods,analyzing both the Bragg and diffuse components,to resolve the intralayer structure of three different ,-cobalt hydroxides, revealing the nature and distribution of metal site coordination. The different compounds with incorporated chloride ions have been prepared with kinetic control of hydrolysis to yield different ratios of octahedrally and tetrahedrally coordinated cobalt ions within the layers, as confirmed by total scattering. Real-space analyses indicate local clustering of polyhedra within the layers, manifested in the weighted average of different ordered phases with fixed fractions of tetrahedrally coordinated cobalt sites. These results, hidden from an averaged unit-cell description, reveal new structural characteristics that are essential to understanding the origin of fundamental material properties such as color, anion exchange capacity, and magnetic behavior. Our results also provide further insights into the detailed mechanisms of aqueous hydrolysis chemistry of hydrated metal salts. We emphasize the power of the methods used here for establishing structure,property correlations in functional materials with related layered structures. [source]