New Allotropic Form Of Carbon Research Articles

Unusual Properties of Raman Spectra of Carbon Graphite from Seregen Deposit (Taimyr). A New Allotropic Form of Carbon?

Unusual Properties of Raman Spectra of Carbon Graphite from Seregen Deposit (Taimyr). A New Allotropic Form of Carbon?

Low-temperature mechanical properties of fullerites: structure, elasticity, plasticity, strength

The results of long-term studies on the physical-mechanical properties of C60 and C70 molecular crystals (fullerites) were systematized and described. These materials are the new allotropic form of carbon in which fullerenes (stable molecules consisting of 60 and 70 atoms) represent the elementary base units. Molecules are combined into crystalline structures mainly by dispersive (van der Waals) forces with a small contribution from covalent bonds. The anomalies of the fullerite crystal structures and features of the phase transitions occurring in them, which are caused by dispersive forces, orientation ordering, and dynamics of the molecules’ rotational degrees of freedom, were discussed. The most interesting transformations of fullerite lattice structures and orientation states were observed in the temperature range of 77 K ≲ Т ≲ 350 K. The majority of the experimental investigations were carried out at these temperatures. The experiments were concentrated on the effects that lattice-orientation phase transitions had on the mechanical properties of single crystals, polycrystalline solids, and compacts. Acoustical spectroscopy at low and high oscillation frequencies, micro- and nanoindentation and macrodeformation methods were used in the experimental research. The crystallogeometric aspects and dislocation mechanisms of plastic slip in fullerites, as well as the methods of observing dislocations and studying their mobility, are described in detail. Also the influence of different external factors, namely, illumination (photoplastic effect), pulsed magnetic field (magnetoplastic effect), and sample compaction pressure (baropolymerization effect) are discussed. The effects of saturating samples of different morphology with hydrogen, oxygen, and inert gas impurities on the fullerites’ mechanical properties were considered. The discussion of the experimental results is accompanied by a brief description of their theoretical interpretation based on analyzing the interaction of elastic and plastic deformations of the fullerite lattice with the processes of orientational ordering, rotation, and librational vibrations of molecules.

Prospects for the Use of Carbon Nanotubes in Medicine

Newly discovered compounds showing unique properties can have profound effect on development of medicine. As far as carbon is concerned, a discovery of great consequences for medicine was that of a new allotropic form of carbon known as fullerene. Recently much interest has been paid to the application of carbon nanotubes as carriers of therapeutic drugs, biosensors, in gene therapy or in anticancer therapy.

Self-propagating high-temperature synthesis as a promising method for the utilization of technical lignins

The self-propagating high-temperature synthesis method has been used for technical lignin utilization after long-term storage under atmosphere conditions. For the first time a new allotropic form of carbon, carbonized lignin, has been obtained and analyzed. It has been shown that, in terms of its parameters (dispersity, surface groups), the carbonized lignin is a suitable alternative to conventional brands of technical carbon in resin compounds.

C72: gaudiene, a hollow and aromatic all-carbon molecule

A new allotropic form of carbon is proposed. The molecular structure of a cavernous C72 molecule has been optimized at the density functional theory level. The structure belonging to the Oh point group was found to be a minimum on the potential energy surface. Current-density calculations show that the gaudiene molecule with formally 72 π electrons sustains strong diatropic currents when exposed to an external magnetic field.

A New Allotropic Form of Carbon [C[sub 28]][sub n] Based on Fullerene C[sub 20] and Cubic Cluster C[sub 8] and Si and Ge Analogs of This Form: Computer Simulation

The structure of a new allotropic form of carbon [C28]n having a simple cubic lattice and space group \(Pm \bar 3\) is proposed. The geometrical parameters of the building block of such a hypothetic crystal are preliminarily determined from DFT-PBE calculations of the cluster C8 @(C20)8 and the polyhedral hydrocarbon molecule C8 @(C20H13)8, in which the centers of the cubic clusters C8 coincide with the centers of the cluster C8 @(C20)8 and of the molecule C8 @(C20H13)8, respectively, and dodecahedral C20 carbon cages are located at the vertices of a cube. The energy of dissociation of the cluster C8 @(C20)8 into a cubic cluster C8 and eight dodecahedral clusters C20 is calculated to be 1482 kcal/mol, and the energy of each C8-C20 bond is equal to 74.2 kcal/mol. The structure of the [C28]n crystal is refined using the DFT-PBE96/FLAPW method and optimized geometry. Calculations show that the crystal is a dielectric with an energy gap of 3.3 eV. The lattice parameter a of the crystal is equal to 5.6 A, and its density is 3.0 g/cm3. The possible existence of analogous allotropic forms of elements Si and Ge is discussed. A method is proposed for designing a hypothetic allotropic form [C28]n from C20(CH3)8 molecules with T h symmetry.

Organic Chemists Conquer the Synthesis of C60

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and Characterization of Cyclic Silicon Compounds of Fullerenes

Organosilicon compounds are perhaps the most important inter-element compounds, as exemplified by disilanes and polysilanes. Similarly, ever since fullerene C60 became available in preparatively useful quantities, this new allotropic form of carbon has attracted much attention, particularly its chemical functionalization. The present review describes how these two disparate classes of compound can be induced to react together and combine to form novel derivatives endowed with unusual properties. In particular, we describe how silylenes derived from various disilane derivatives under thermal and photochemical conditions can react with fullerenes and endohedral metallofullerenes. Mono- bis- and even multi-silylation of the fullerene framework takes place leading to a new class of fullerene-based organic compounds which at the same time opens a promising new field in materials science.

Narrow-line spectra of fullerene molecules in a crystalline matrix

The new allotropic form of carbon, the fullerenes, which possess unusual physical properties and are promising for various practical applications, have received much attention in recent years. Revealing the energy structure of fullerenes is one of the pressing problems of the physics of these novel materials. Rich information on their electronic and vibrational states could be obtained from optical spectra. However, until recently only wide-band absorption and emission spectra of fullerenes were observed in both solutions and the crystalline state (in fullerites), which did not allow full advantage of to be taken optical spectroscopy. The possibility of producing narrow-line spectra of fullerene C{sub 70} molecules in solid solutions of organic crystals at low temperatures was established. The present paper contains more detailed information on these spectra. In addition, observation of the narrow-line spectrum of the fullerene C{sub 60} molecule is reported for the first time. First the authors consider C{sub 70} spectra.

Buckminsterfullerene as a model reactant for testing electron transfer theory

The importance of molecular structure and quantum mechanical properties in determining the kinetics of electron transfer has been discussed at length in the recent literature [l]. According to Marcus’ theory [2], the reactant is represented as a simple sphere, any changes in molecular configuration accompanying electron transfer being associated with an internal reorganization energy. In order to estimate the outer sphere reorganization energy one must assume a size and shape for the reacting molecule. Attempts to improve on the simple spherical model have included descriptions based on ellipsoids [3] and on collections of spheres [4]. Even when the molecule is approximately spherical, selection of its radius requires careful consideration of a variety of experimental data [5,6]. Considerable attention has been directed in recent months to the electrochemistry of buckminsterfullerene (C,), the new allotropic form of carbon 17-161. This molecule can be reduced in polar solvents in several one electron transfer steps [9-161. From the point of view of testing electron transfer theory, it would seem to be an ideal system. It is close to spherical in shape, and is chemically uniform over its surface. Because of its large size, the rate constant associated with electron transfer is expected to be large. We have recently studied the thermodynamics and kinetics of electroreduction of both C, and C,, in several polar solvents at platinum microelectrodes. In the present communication we present kinetic data for the first electron transfer to these molecules and compare the results obtained with those for other fast heterogeneous reactions studied under similar conditions. It should be noted that the C,, molecule is spheroidal in shape with the ratio of the shorter major axis to the longer equal to 0.86 1171. Data are also presented for some activation

Another Possible Carbon Allotrope

AbstractA new allotropic form of carbon formed by allene units is described. Its tetragonal unit cell contains 12 carbon atoms (8 sp2 and 4 sp) and it has a calculated density of 2.72 g. cm−3. As a result of the mixture of sp2 and sp carbon atoms, this new all‐carbon molecule is expected to be rather stable and may have metallic properties.

Chaoite, a New Allotropic Form of Carbon, Produced by Shock Compression

Journal of the American Ceramic SocietyVolume 63, Issue 3-4 p. 238-239 Chaoite, a New Allotropic Form of Carbon, Produced by Shock Compression NOBUO SETAKA, NOBUO SETAKA Member, the American Ceramic Society.Search for more papers by this authorYOSHIZO SEKIKAWA, YOSHIZO SEKIKAWASearch for more papers by this author NOBUO SETAKA, NOBUO SETAKA Member, the American Ceramic Society.Search for more papers by this authorYOSHIZO SEKIKAWA, YOSHIZO SEKIKAWASearch for more papers by this author First published: March 1980 https://doi.org/10.1111/j.1151-2916.1980.tb10710.xCitations: 31 The writers are with the National Institute for Researches in Inorganic Materials, 1–1 Namiki, Sakura-mura, Niihari-gun, Ibaraki, 300–31 Japan. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume63, Issue3-4March 1980Pages 238-239 RelatedInformation

A New Allotropic Form of Carbon from the Ries Crater

A new allotropic form of carbon occurs in shock-fused graphite gneisses in the Ries Crater, Bavaria. The assemblage in which it occurs consists of hexagonal graphite, rutile, pseudobrookite, magnetite, nickeliferous pyrrhotite, and baddeleyite. Electron-probe analyses indicate that the new phase is pure carbon. It is opaque and much more strongly reflecting than hexagonal graphite. Measurement of x-ray diffraction powder patterns leads to cell dimensions a = 8.948 +/- 0.009, c = 14.078 +/- 0.017 angstroms, with a primitive hexagonal lattice.