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Hexagonal Prisms (hexagonal + prism)

Distribution by Scientific Domains
Chemistry55%
Polymers and Materials Science33%

Selected Abstracts

Zinc Oxide Microstructures: Zinc Oxide Microtowers by Vapor Phase Homoepitaxial Regrowth (Adv. Mater.

ADVANCED MATERIALS, Issue 8 2009
8/2009)
Simultaneous axial and radial epitaxies can be achieved by growing ZnO microtowers by repeating a growth cycle several times, report Zhengwei Pan and co-workers on p. 890. The as-grown ZnO microtowers display a preferential growth habit of hexagonal prism,dihexagonal pyramid. Some rare or new growth habits such as dihexagonal prism,dihexagonal pyramid, hexagonal prism,trihexagonal pyramid and dihexagonal prism,trihexagonal pyramid (as shown on the cover) have also been identified. [source]

Zinc Oxide Microtowers by Vapor Phase Homoepitaxial Regrowth

ADVANCED MATERIALS, Issue 8 2009
Zhengwei Pan
Simultaneous axial and radial epitaxies can be achieved on growing ZnO microtowers through a regrowth technique of repeating the same growth circle for several times. The as-grown ZnO microtowers display a preferential growth habit of hexagonal prism,dihexagonal pyramid. The apexes of the pyramidal towers are very sharp, with a radius of curvature as small as 2 to 50 nm. [source]

Molten-salt Synthesis and Properties of ZnS with Hexagonal Prism Morphology

CHINESE JOURNAL OF CHEMISTRY, Issue 10 2007
Jin-Song LIU
Abstract ZnS with hexagonal prism morphology has been synthesized successfully by molten-salt method with ZnS nanoparticles as precursors, and the ZnS nanoparticles were prepared by one-step solid-state reaction of Zn(CH3COO)2·2H2O with Na2S·9H2O at ambient temperature. Crystal structure and morphology of the product were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and HRTEM. Ultraviolet-visible optical absorption spectrum of the ZnS hexagonal prism shows a distinct red shift from that of bulk ZnS crystals and photoluminescence spectrum exhibits strong emissions at 380 and 500 nm, respectively. Further experiments were designed and the formation mechanism of the ZnS hexagonal prism has been also discussed in brief. [source]

Synthesis of Zinc Glycerolate Microstacks from a ZnO Nanorod Sacrificial Template

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2009
Róbert Rémiás
Abstract We synthesized zinc glycerolate (ZnGly) microstacks bytreating ZnO with glycerol at 100 °C under reflux. We observed that the morphology of the ZnO source has a pronounced effect on the appearance of the ZnGly product. In the absence of structure-directing effects the product ZnGly is obtained as a random heap of hexagonal prisms with an average diameter and thickness of ca. 2.5 ,m and ca. 350 nm, respectively. However, bundles of nanorod-shaped ZnO obtained by the thermal decomposition of zinc oxalate nanorods could readily be transformed into 2,4 ,m long zinc glycerolate microstacks in which 6,12 hexagonal prisms are aligned face-to-face. We present evidence that the ZnGly plates in the microstacks are bound together by forces strong enough to withstand mechanical deformation exercised by a contacting AFM tip. The ZnGly microstacks appear to emerge from the ZnO nanorod bundles in an approx. 1:1 ratio in the reactive template synthesis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Control of apatite crystal growth by the co-operative effect of a recombinant porcine amelogenin and fluoride

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2006
Mayumi Iijima
Recently, we used native amelogenins extracted from developing pig enamel to examine the combined effect of fluoride and amelogenins on the growth of octacalcium phosphate (OCP) and apatite crystals. The purpose of the present study was to investigate this combined effect using a highly purified recombinant amelogenin. We applied porcine amelogenin (rP172) and fluoride in a dual-membrane system as a model for tooth enamel formation. The combination of rP172 and fluoride in this system resulted in the formation of rod-like apatite crystals. On the other hand, without fluoride, rod-like OCP crystals of a comparable size were formed, and rather large hexagonal prisms of mixed crystals of OCP and apatite grew without amelogenins. Thus, highly purified and homogeneous recombinant amelogenin, in co-operation with F, regulated the mineral phase, habit, and size of crystals in the same manner as the extracted heterogeneous porcine amelogenins. We suggest that in both cases the control over the crystal phase and morphology was a direct effect of amelogenin protein serving as a scaffold for apatite mineralization. [source]

Embryonic States of Fluorapatite,Gelatine Nanocomposites and Their Intrinsic Electric-Field-Driven Morphogenesis: The Missing Link on the Way from Atomistic Simulations to Pattern Formation on the Mesoscale

ADVANCED FUNCTIONAL MATERIALS, Issue 22 2009
Paul Simon
Abstract The shape development of fluorapatite (FAP),gelatine nanocomposites is revealed by means of HRTEM investigations starting from molecular dimensions up to the formation of mesoscaled (elongated) hexagonal prisms. The composite nature of the aggregates is proved by IR spectroscopy and by chemical analyses on all states of shape development. The initial states are characterized by triple-helical fiber protein bundles, which are mineralized step-by-step forming and fixing nanoplatelets of FAP in a mosaic arrangement. After being fully mineralized the bundles form elongated composite nanoboards. In the next step of the growth process the boards aggregate to bundles of boards which are in a more or less parallel alignment with respect to each other. By adding up more and more composite nanoboards a critical size is reached and an electric field is developed, which takes over control and directs the further development of the aggregates. This kind of electric-field-directed growth of the elongated polar nanoboards additionally leads to the formation and inclusion of protein nanofibrils into the growing composite aggregate. By this method, cone-like nanofibril structures develop along the long axis of the aggregates accompanied by more perfect parallel alignment of the composite boards within the aggregates. Further shape development is characterized by adding up composite nanoboards, in particular to increase the third dimension in volume. This thickening process preferably takes place in the middle part of the elongated aggregates and finally proceeds to their basal ends until a perfect hexagonal prismatic seed is formed, which then is ready for further shape development on the micrometer scale. [source]

Reciprocal-space mapping of epitaxic thin films with crystallite size and shape polydispersity

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2006
A. Boulle
A development is presented that allows the simulation of reciprocal-space maps (RSMs) of epitaxic thin films exhibiting fluctuations in the size and shape of the crystalline domains over which diffraction is coherent (crystallites). Three different crystallite shapes are studied, namely parallelepipeds, trigonal prisms and hexagonal prisms. For each shape, two cases are considered. Firstly, the overall size is allowed to vary but with a fixed thickness/width ratio. Secondly, the thickness and width are allowed to vary independently. The calculations are performed assuming three different size probability density functions: the normal distribution, the lognormal distribution and a general histogram distribution. In all cases considered, the computation of the RSM only requires a two-dimensional Fourier integral and the integrand has a simple analytical expression, i.e. there is no significant increase in computing times by taking size and shape fluctuations into account. The approach presented is compatible with most lattice disorder models (dislocations, inclusions, mosaicity, ,) and allows a straightforward account of the instrumental resolution. The applicability of the model is illustrated with the case of an yttria-stabilized zirconia film grown on sapphire. [source]

Li12Cu16+xAl26,x (x = 3.2): a new intermetallic structure type

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2008
Volodymyr Pavlyuk
The new ternary lithium copper aluminide, Li12Cu16+xAl26,x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li12Cu16+xAl26,x consists of pseudo-Frank,Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl2 and Li8Cu12+xAl6,x) and to the well known CaCu5 structure. [source]

Poly­[manganese(II)-,2 -benzidine-,2N:N,-,3 -bi­phenyl-2,2,-di­carboxylato-,4O:O,,O,,:O,,,]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2004
Min Jiang
The title compound, [Mn(C14H8O4)(C12H12N2)]n, with a novel three-dimensional framework, has been prepared by a hydro­thermal reaction at 433,K. Each Mn atom lies on a twofold axis in a slightly distorted octahedral geometry, coordinated by two N atoms from two benzidine ligands and four O atoms from three symmetry-related biphenyl-2,2,-dicarboxylate (bpdc) ligands. The benzidine ligands lie about inversion centres and the bpdc ligands about twofold axes. Each bpdc ligand is bonded to three Mn ions to form a continuous chain of metal ions. The bpdc ligands are accommodated in a series of distorted holes resembling hexagonal prisms. [source]