Carbon Nets Research Articles

In situ Mössbauer spectroscopic study of iron III chloride intercalated in graphite under reaction conditions

In situ 57Mössbauer spectroscopy has been used to study the process of reduction and Fischer-Tropsch reactions on FeCl 3 intercalated in graphite layers. It is found that on flowing H 2 on graphite intercalated by FeCl 3 at 400° C, FeCl 3 converts to FeCl 2 and partly to small particles of α-Fe. The Mössbauer spectra of the reduced sample are superposition of a sextuplet and two quadrupole doublets indicative of metallic iron and two species of FeCl 2. However, at room temperature and at 400° C for a short period of reduction the magnetic hyperfine splittings ( ca. 295 kOe and 262 kOe respectively) are smaller than the corresponding parameters for bulk metallic iron. The differences have been attributed to the interaction between the monolayers of iron atoms and the carbon nets of the graphite support. When the reduction was carried out for a longer period, α-Fe was formed. When a sample reduced for a short period of time is heated at 400°C in the presence of the synthesis gas, part of the iron particles sinter, and α-iron is observed. On heating the above sample once again at 400°C in the presence of the synthesis gas, the remaining small particles of iron are totally converted to the bulk phase (α-Fe). Experimental observations indicate that α-Fe and FeCl 2 are present on the surface as well as inbetween the intercalated graphite layers.

Theoretical Organic Chemistry

Chapter headings: Theoretical Organic Chemistry: Looking Back in Wonder (J.J.C. Mulder). Inter-Relations between VC & MO Thoeries for Organic -Networks (D.J. Klein). The Use of the Electrostatic Potential for Analysis and Prediction of Intermolecular Interactions (T. Brinck). Exploring Reaction Outcomes through the Reactivity-Selectivity Principle Estimated by Density Functional Theory Studies (B.S. Jursic). A Hardness and Softness Theory of Bond Energies and Chemical Reactivity (J.L. Gazquez). Molecular Geometry as a Source of Chemical Information for -Electron Compounds (T.M. Krygowksi, M.K. Cyra ski). Average Local Ionization Energies: Significance and Applications (J.S. Murray, P. Politzer). Intrinsic Proton Affinity of Substituted Aromatics (Z.B. Maksi , M. Eckert-Maksi ). Dipole Moments of Aromatic Heterocycles (C. Parkanyi, J-J. Aaron). New Developments in the Analysis of Vibrational Spectra. On the Use of Adiabatic Internal Vibrational Modes (D. Cremer et al.). Atomistic Modeling of Enantioselection: Applications in Chiral Chromatography (K.B. Lipkowitz). Theoretical Investigation of Carbon Nets and Molecules (A.T. Balaban). Protein Transmembrane Structure: Recognition and Prediction by Using Hydrophobicity Scales through Preference Funtions (D. Jureti et al.). Polycyclic Aromatic Hydrocarbon Carcinogenicity: Theoretical Modelling and Experimental Facts (L. von Szentpaly, R. Gosh). Cycloaddition Reactions Involving Heterocyclic Compounds as Synthons in the Preparation of Valuable Organic Compounds. An Effective Combination of a Computational Study and Synthetic Applications of Heterocycle Transformations (B.S. Jursic). Triplet Photoreactions Structural Dependence of Spin-Orbit Coupling and Intersystem Crossing in Organic Biradicals (M. Klessinger). Index.

A technique for preparing holey carbon films for high resolution electron microscopy

SUMMARYA simple and reproducible method of preparing holey carbon nets for use as support films for high resolution electron microscopy is described.

Structure of Graphite

SINCE the original determination by Bernal1 of the structure of graphite, various alternative structures have been proposed from observations of extra lines and spots on X-ray diffraction photographs. The Bernal structure can be visualized as hexagonal nets of carbon atoms stacked in layers so that half the atoms in one layer are directly above those in the layer below; the other half being above the holes in the first layer. Lipson and Stokes2 were able to show that extra lines on Debye–Scherrer powder photographs of graphite filings could be indexed on the basis of a rhombohedral structure, which can be obtained from the hexagonal structure by shearing a layer a distance |a|/√3 in a direction, where |a| is the lattice parameter of the unit cell in the layer planes. This structure was afterwards verified by X-ray and electron diffraction work on single crystals3. In all cases where it has been found, the rhombohedral modification results from deformation of the original hexagonal structure and can be eliminated by suitable annealing treatments. A second modification of the original hexagonal structure was proposed by Lukesh4 from his observation of satellite spots on c-axis precession photographs of single crystals. This modification results in a large orthorhombic superlattice cell in which the carbon nets are slightly distorted hexagons.