117. anomalous thermal emission of bromine molecules from graphite-bromine residue compounds

1
686 ABSTRACTS tion pressure of C& is determined therefrom, and thermochemical data of the system are obtained. An interpretation is given to the hysteresis phenomena observed in the sorption-desorption cycle of the system. 116. A. Magnetic and gravimetric study of the kinetics of the first intercalation of bromine into a Pyro=bon A. Marchand, J_ C. Rouillon and M. H. de Macuzo (Cent7e de Recherc~s Paul Pascal, Dads Univer- sit&e, 33 Talewe, Frunce). Identical platelets of pyrocarbon were each submitted to a single sorption and desorption at various temperatures (2035°C) and bromine pressures (116-176 Torr). Changes of weight and diamagnetic anisotropy were measured in situ as a function of time. It is concluded that the first bromine insertion is a two-step process; the first step follows zero-order kinetics and corresponds to the building of metastahle structures, where electron transfer is more restricted than in lamellar or residue compounds formed at a later time. 117. AnomaIous thermal emission of bromine moleeuIes from graphite-bromine residue eompountia V. R. Deitz and J. L. Bitner (~uv~~ Research ~~~~, ~~~~n~~, D.C.). During the pro~ammed heating and cooling of the sample (O-950%) emission maxima were observed at approximately 110 and 75O”C, the peak quantities being l-15 p.p.m. Br* Upon cooling, the maxima were displaced somewhat to lower temperatures. Using a high-temperature (25-750°C) X-ray diffractometer, anomalous and reversible changes were indicated in the c-spacing. It is proposed that the diffusion of Brz, trapped at dislocations in the networks, is restricted by a temperature-dependent structural change in the graphite residue compound. 118. Extra dl@‘raetion patterns due to halogen doping of graphite M. Saito (School of ~e~~~e, Nikon ~~iv~~, Tokyo, Jupa~) and T. Tsuzuku (CoZ~ge of S&we ad Engirz-eering, Nihon Uniuewity, Tokyo, Japan). It has been found that graphite-ICI residue compounds prepared from a stress-annealed pyrolytic graphite produces distinctive extra patterns in the X-ray diffraction diagram. The interlayer spacing newly induced is 1.05 times larger than the (001) spacing of graphite lattice. The temperature dependence in the range down to 90 K has also been investigated. 119. Laxnellar oxide formation by liquid phase oxidation of earhons P. Ehrburger and J. B. Donnet (Centre de Recherches sw la Physico-Chimie &s Surjbes Solides-C.N.R.S. 68200 Moore, Frurwe). The oxidation of several types of carbons leading to the formation of lameliar oxides was studied. The progression of formation of graphitic oxides was followed by X-ray diffraction, i.r. spectroscopy and CO, evolution. The fraction of carbon transformable into graphitic oxide is inde- pendent of the reaction temperature and carbon characteristic. 120. A study of the electrical resistivlty of the oxidation products of graphite A. Martin-Rodriguez, J. D. Lopez-Gonzalez, E. Fernandez Duran and G. Pardo Sanchez (Faculty of Sciences, University of Granada, Spain). The electrical resistivity of the oxidation products of natural and artificial graphites has been studied. The eIectrical resistivity increases with the time of oxidation until reaching the values corresponding to graphitic acid. The influence of humidity content on the electrical resistivity has been studied. VI. FIBERS AND COMFOSITES 141. PAN pyrolysis studied by gas- and ESR-analyses A. Fiedler, E. Fitzer and F. Rozploch (Znstitid ftir Chemide Tech&, Universitat Kadsruhe, W. Germuny). The pyrolysis chemistry of oxidized PAN fibers in helium was studied between 250 and 1000°C by analyzing the gases during heat-treatment and by elementary analyses and KSR-absorption measure- ments of the residues. A maximum HCN formation was found around 8OO”C,caused by the disrupture of the heteroaromatics. The samples heattreated in this temperature range show an extreme broaden- ing of the ESR absorption line after room-temperature exposure to air. The relation of these two pheno- mena will be discussed.

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Page 1: 117. Anomalous thermal emission of bromine molecules from graphite-bromine residue compounds

686 ABSTRACTS

tion pressure of C& is determined therefrom, and thermochemical data of the system are obtained. An interpretation is given to the hysteresis phenomena observed in the sorption-desorption cycle of the system.

116. A. Magnetic and gravimetric study of the kinetics of the first intercalation of bromine into a Pyro=bon

A. Marchand, J_ C. Rouillon and M. H. de Macuzo (Cent7e de Recherc~s Paul Pascal, Dads Univer- sit&e, 33 Talewe, Frunce). Identical platelets of pyrocarbon were each submitted to a single sorption and desorption at various temperatures (2035°C) and bromine pressures (116-176 Torr). Changes of weight and diamagnetic anisotropy were measured in situ as a function of time. It is concluded that the first bromine insertion is a two-step process; the first step follows zero-order kinetics and corresponds to the building of metastahle structures, where electron transfer is more restricted than in lamellar or residue compounds formed at a later time.

117. AnomaIous thermal emission of bromine moleeuIes from graphite-bromine residue eompountia V. R. Deitz and J. L. Bitner (~uv~~ Research ~~~~, ~~~~n~~, D.C.). During the pro~ammed

heating and cooling of the sample (O-950%) emission maxima were observed at approximately 110 and 75O”C, the peak quantities being l-15 p.p.m. Br* Upon cooling, the maxima were displaced somewhat to lower temperatures. Using a high-temperature (25-750°C) X-ray diffractometer, anomalous and reversible changes were indicated in the c-spacing. It is proposed that the diffusion of Brz, trapped at dislocations in the networks, is restricted by a temperature-dependent structural change in the graphite residue compound.

118. Extra dl@‘raetion patterns due to halogen doping of graphite M. Saito (School of ~e~~~e, Nikon ~~iv~~, Tokyo, Jupa~) and T. Tsuzuku (CoZ~ge of S&we ad

Engirz-eering, Nihon Uniuewity, Tokyo, Japan). It has been found that graphite-ICI residue compounds prepared from a stress-annealed pyrolytic graphite produces distinctive extra patterns in the X-ray diffraction diagram. The interlayer spacing newly induced is 1.05 times larger than the (001) spacing of graphite lattice. The temperature dependence in the range down to 90 K has also been investigated.

119. Laxnellar oxide formation by liquid phase oxidation of earhons P. Ehrburger and J. B. Donnet (Centre de Recherches sw la Physico-Chimie &s Surjbes Solides-C.N.R.S.

68200 Moore, Frurwe). The oxidation of several types of carbons leading to the formation of lameliar oxides was studied. The progression of formation of graphitic oxides was followed by X-ray diffraction, i.r. spectroscopy and CO, evolution. The fraction of carbon transformable into graphitic oxide is inde- pendent of the reaction temperature and carbon characteristic.

120. A study of the electrical resistivlty of the oxidation products of graphite A. Martin-Rodriguez, J. D. Lopez-Gonzalez, E. Fernandez Duran and G. Pardo Sanchez (Faculty of

Sciences, University of Granada, Spain). The electrical resistivity of the oxidation products of natural and artificial graphites has been studied. The eIectrical resistivity increases with the time of oxidation until reaching the values corresponding to graphitic acid. The influence of humidity content on the electrical resistivity has been studied.

VI. FIBERS AND COMFOSITES

141. PAN pyrolysis studied by gas- and ESR-analyses A. Fiedler, E. Fitzer and F. Rozploch (Znstitid ftir Chemide Tech&, Universitat Kadsruhe, W. Germuny).

The pyrolysis chemistry of oxidized PAN fibers in helium was studied between 250 and 1000°C by analyzing the gases during heat-treatment and by elementary analyses and KSR-absorption measure- ments of the residues. A maximum HCN formation was found around 8OO”C, caused by the disrupture of the heteroaromatics. The samples heattreated in this temperature range show an extreme broaden- ing of the ESR absorption line after room-temperature exposure to air. The relation of these two pheno- mena will be discussed.