Anisotropic chemical properties

Cs6Re6Si2 structure is expressed in the anisotropic chemical properties of the compound. The addition of water to the plate-shaped Cs6Re6Si2 crystals causes them to split parallel to the planes of the plates. This type of reaction is not known for the molybdenum and tungsten halides MgYn-... 

Crystals have spatially preferred directions relative to their internal lattice structure with consequences for orientation-dependent physico-chemical properties i.e., they are anisotropic. This anisotropy is the reason for the typical formation of flat facetted faces. For the configuration of the facets the so-called Wullf theorem [20] was formulated as in a crystal in equihbrium the distances of the facets from the centre of the crystal are proportional to their surface free energies. ... 

Abstract The present paper discusses classification of nano-objects, which is based on their size, morphology and chemical nature. The subject of nanochemistry includes those nano-objects whose chemical properties depend on size and morphology, such as spheroidal molecules, anisotropic (2D) and isotropic (ID) nanoparticles, nano-clusters and nanophases. Nanophase is a nano-dimensional part of the microphase whose properties depend on its size. The potential health hazards of nano-objects are associated with their capability of penetrating the body through inhalation, digestion or the skin. 

Whether or not the Si—Si dimer a bond is cleaved, it seems to be the consensus that the majority of the surface product forms two Si—C bonds, an analog of the [2 + 2] product. This is useful, since the orientation of the individual molecules can be controlled, yielding anisotropic physical properties of a chemically modified silicon surface as discussed in recent accounts50. 

The optical anisotropy observed in most carbon materials reflects the ordered stacking of graphite-like microcrystalline units that has been recognized to be essential in determining their properties. Pitch-based carbon fiber, electrode and metallurgical cokes, and carbons for nuclear reactors are characterized by their anisotropic texture since this structural factor is fundamentally related to their mechanical, thermal, electronic, and chemical properties (1-5) ... 

This contribution gives a review of recent spectroscopic investigations concerning the photophysical and photochemical primary and secondary processes of the solid state polymerization reaction in diacetylene single crystals. It will be shown, that diacetylenes are an unique model system for the study of the reaction mechanism of a solid state chemical reaction which is characterized by a variety of reaction intermediates. The polymerization reaction in these crystals is of special importance, due to the resulting polymer single crystals, which exhibit extraordinary anisotropic physical properties. 

Graphite shows very anisotropic thermal properties as a result of its crystal structure. This is because graphite possesses two-dimensional hexagonal network structures and the layers are held together very loosely by weak forces. For example, chemical vapor deposited carbon, which is manufactured with heat treatment at 3000°C after the deposition and possesses almost ideal graphite structures, has a thermal conductivity of 2,000 W/m-K (at room temperature) parallel to the layers and 10 W/m K in the perpendicular direction as shown in figure 1. This value in the parallel direction is approximately 4-5 times more than the value of silver or copper, which are typical high thermal conductivity metals. 

Metal-chain complexes containing stacked square-planar tetracyanoplatinate groups, [Pt(CN)4]2", are currently of high interest because of their one-dimensional (very anisotropic ) metallic properties. Complexes of this type contain metal-atom chains and often possess a characteristic brilliant, metallic luster. They may be synthesized by oxidation using chemical or electrolytic techniques.1 Although these compounds often appear metallic, they may also be semiconductors. These complexes differ in their Pt-Pt intrachain separations, degree of partial oxidation of the platinum atom (Pt2-1 2 4), electrical conductivity, and metallic color.2 Compounds in this series which contain platinum atoms in a nonintegral oxidation state are known as partially oxidized tetra-cyanoplatinate (POTCP) complexes. Some complexes also possess a metallic luster but are not metallic, as is the case for Tl4(C03)[Pt(CN)4] (see below). 

Gray metal close-packed hexagonal structure anisotropic high permeability to X-rays, mp 1287°. bp 2500° (extrapolated). d 1.8477. Heat capacity at constant pressure (30°) 0.437 cal/g/ C Walker el al, J. Chem. Eng. Data 7, 595 (1962). Latent heat of fusion 3.5 kcal/mole. Brinell hardness 60-125, Chemical properties similar to aluminum ... 

In 1973 Labes et ah 8,9) synthesized crystalline bundles of impure (SN)a. flbers. Although the S N atomic ratio was 1 1, the material contained 5.48% impurity (4.93% 0, 0.42% H, and 0.13% C). However, metallic-like conductivity was observed in directions parallel to the (SN), flbers, and this increased sharply with decrease in temperature. Six different samples had conductivities at room temperature of 10, 89, 230, 640, 1470, and 1730 ohm" cm" Since the electrical conductivity of an anisotropic substance can be affected enormously by even traces of impurities, we decided that it was most important to attempt to synthesize analytically pure crystals of (SN). and to examine the physical and chemical properties of the material. Only in this way would it be possible to determine whether the metallic-like properties reported for (SN). (8, 9) were characteristic of the pure material. 

Since the substrate may influence the anisotropic optical properties of the overlying film [595], the method of Buffeteau et al. [247, 566-568, 593] is conceptually more reliable when the MO is studied on solid transparent substrates, whereas the initial anisotropic optical constants are extracted from normal- and oblique-incidence transmission or polarized reflection of the same film on the same substrate. In the case when different substrates participate into the measurements (e.g., when MO in monolayers at the AW interface is studied), the comparison of the simulated and experimental spectra can be used for distinguishing chemical effects generated by specific film-substrate interactions [568b]. In particular, the kmm values derived from spectra of monolayers at the AW interface obtained by IRRAS are usually larger than those obtained by eUipsometric measurements of thin films on solid supports [247]. This difference has been attributed to a gradient in the optical properties of the interfacial water [71]. 

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