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Vacuum-microgravimetric characterization of catalyst candidates for fuel cell electrodes
Classified abstracts 3524-3534 investigation of the surface diffusion of oxygen on W(110). The vibrating electrode consists of a wire of 6 pm diameter which can be moved across the surface at a distance of 15 pm. The local work function profile is converted to the corresponding concentration profile by a calibration curve obtained by Auger spectroscopy. The evaluation achieved by the Boltzmann-Matano analysis yields a concentration dependent diffusion coefficient with an activation energy of 27 f 2 kcal. The concentration dependence can qualitatively be explained by the known adsorption properties of this adsorbate-substrate system. Von R Butx and H Wagner, Vakuum-Tech. 26 (5), 1977, 142-146 (in German).
36 3524. Scanning electron microscopic investigations of polytetrafluorethylene and polyphenylenesulfide coatings. (Germany) A principal survey on the supra-molecular structure of polytetrafluorethylene and polyphenylenesulphide is given. Monodisperse and polydisperse coating systems of PTFE and PPS are applied into aluminium sheets under various technological conditions. Scanning electron microscopic investigations of the coating surfaces for different ratios of mixtures ate considered to characterize the surface structure. (Austria) Von H Hubeny and H Dragaun, Vakuum-Tech, 26 (5), 1977, 137-141 (in German).
36 3525. Unfolding appearance potential spectra. (GB) The Soft X-ray Appearance Potential Spectra of a number of layer materials have been found to be in excellent agreement with the predictions of a conduction band self convolution model. Crystal field splitting of d orbitals in octahedrally co-ordinated transition metal dichalcogenides gives rise to strong effects in AP spectra which are consistent with a self convolution interpretation. A similar argument is successfully applied to the remarkable graphite spectrum, a detailed analysis of which correlates well with secondary electron emission data and also Photon Appearance Potential Spectroscopy. The deduced form of the conduction band d.o.s. is in qualitative accord with Painter and Ellis’s band calculations. C Webb, Vacuum, 27 (9), 1977,537-544. 36 3526. Secondary emission spectroscopy of solid surfaces. (USSR) Physical bases and possibilities of all methods of secondary emission spectroscopy of solid surfaces are considered. Instruments for secondary emission spectroscopy are described. Utilization of secondary emission spectroscopy is discussed. M V Gomoyunova, Zh Tekh Fiz, 46 (6), 1976, 1137-l 170 (in Russian).
36 3529. Thermal disorder of silver bromide studied by 100 keV proton channelling. (Germany) Channelling of 100 keV protons by the Rutherford backscattering technique in single crystals of AgBr is studied experimentally in the temperature range of 90 to 595 K. The results for the critical angle, the temperature dependence of the minimum yield and the dechannelling cross section of silver obtained from a thin evaporated metallic surface layer are presented. (France) M Roulet et al, Phys Sfafus Solidii (a), 35 (l), 1976,97-108. 36 3530. The influence of electron escape depth on the quantitative analysis by Auger spectroscopy. (USSR) It is shown that it is necessary to account the escape depth of Auger electrons at quantitative determination of chemical composition of surface by the Auger electron spectroscopy. Experimental determination of escape depth of Auger electrons with energies 50, 120 and 400 eV has been made with the aid of adsorption of In atoms on the (100) face of GaP and GaAs. It is found that the escape depth of 51 eV Auger electrons of Ga is about one monolayer, that of 120 eV Auger electrons of P is about 2.5 atomic layers and that of 403 eV Auger electrons of In in a thick In layer is about 4 atomic layers. The given calibration curves can be used for quantitative determination of chemical composition in the systems GaAs and GaP + In. A Yu Mityagin et al, Radiotekh Elektron, 21 (3), 1976, 589-493 (in Russian).
36 3531. Location of interstitial deuterium in TaD0.067 by channelling. (Germany) The channelling of a 750 keV 3He ion beam with an angular divergence of 0.05” in connection with a resonant nuclear reaction D(3He, p)“He was used for direct determination of the interstitial position of deuterium in TaDo.os, at room temperature. It is found that the majority (in excess of 90%) of deuterium atoms occupy the tetrahedral sites-in the b c c tantalum lattice. M Antonini and H D Carstanien. Phvs Sfalus Solidii (a). 34 (2). 1976 K153-K157. 36 3532. Application of secondary electron multipliers as detectors of ultrasoft radiation in X-ray microanalysers. (USSR) It is experimentally shown that open secondary electron multipliers with dynodes of Cu+ Be alloy and evaporated CsI photo-cathode on glass or aluminium substrates possess higher sensitivity of detection of ultrasoft X-radiation of light elements than flowing proportional counters usually used in X-ray microanalysers. A I Kozlenkov et al, Prib Tekh Eksper, No 1, 1976, 202-205 (in _I.
.,,
.,,
Russian).
36 3527. A study of relative energy losses of channelled protons in a tungsten single crystal. (Germany) The differences in the stopping of protons with incident energy of 6.3 MeV moving along the different crystallographic directions in tungsten are investigated. The energy spectra of protons scattered in tungsten single crystals with thickness of 40 to 80 pm were measured by a semiconductor spectrometer. Experimental results are discussed. (USSR) A S Rudnev, Phys Starus Solidii (a), 35 (l), 1976, K23-K27. 36 3528. High-resolution examination of uncoated insulators by SEM applied to grain boundaries in sodium chloride. (Germany) A technique for direct observation of grain boundaries in nonconducting alkali halide bicrystals by scanning electron microscope without using either conducting coatings or low-resolution low-voltage operation is described. The technique is based on the use of a backscattered electron detector in conjunction with an environmental cell. The electron detector consists of the wide-angle scintillator-light guide and a photomultiplier. Elimination of charging artefacts on an uncoated insulating specimen, when using the back-scattered electron detection mode of operation, requires the specimen to be surrounded by a residual vapour pressure of the order of 10-i torr. This mode of operation confirmed the existence in grain boundaries in nominally pure NaCl of second phase particles, the shape and distribution of these particles showing that the precipitation reaction can markedly influence boundary structure and properties. (England) L B Harris et al, Phys Stafus Solidi (a), 35 (l), 1976, 371-377.
37. INORGANIC CHEMISTRY, ANALYTICAL CHEMISTRY, DISTILLATION, MISCELLANEOUS CHEMICAL APPLICATIONS, OIL AND HYDROCARBON TECHNOLOGY 37 3533. Vacuum-microgravimetric characterization of catalyst candidates for fuel cell electrodes. (Germany) In the search for noble-metal-free cathode materials resistant to acid electrolytes and capable of catalysing the conversion of oxygen thermogravimetric methods have been used to determine the conditions of preparation, to analyse the chemical properties and to characterize the pore structure of the potential catalysts. The paper comprises results of investigations on inorganic compounds, such as ammonium tungstates, chromates, vanadates, molybdate and permanganate, and on organic polymers, such as polyamide nitriles, other CN polymers and polyacenoquinone pyrolysates. Von H Behret et al, Vakuunl-Tech, 26 (5), 1977, 147-148 (in German). 37 3534. The remote measurement of sulphur in steels by mass spectrametry. (GB) An experimental technique is described which enables steel to be typified by its sulphur content. A single laser pulse fired at the surface vaporizes a controlled amount of the sample. This is done in an oxidizing atmosphere like air, or carbon dioxide and sulphur dioxide is formed which can be pumped through a vacuum probe, typically 30 m long, and measured in a mass spectrometer. An expression iS derived describing the shape of the pulse of gas obtained and the 159
36 3524. Scanning electron microscopic investigations of polytetrafluorethylene and polyphenylenesulfide coatings. (Germany) A principal survey on the supra-molecular structure of polytetrafluorethylene and polyphenylenesulphide is given. Monodisperse and polydisperse coating systems of PTFE and PPS are applied into aluminium sheets under various technological conditions. Scanning electron microscopic investigations of the coating surfaces for different ratios of mixtures ate considered to characterize the surface structure. (Austria) Von H Hubeny and H Dragaun, Vakuum-Tech, 26 (5), 1977, 137-141 (in German).
36 3525. Unfolding appearance potential spectra. (GB) The Soft X-ray Appearance Potential Spectra of a number of layer materials have been found to be in excellent agreement with the predictions of a conduction band self convolution model. Crystal field splitting of d orbitals in octahedrally co-ordinated transition metal dichalcogenides gives rise to strong effects in AP spectra which are consistent with a self convolution interpretation. A similar argument is successfully applied to the remarkable graphite spectrum, a detailed analysis of which correlates well with secondary electron emission data and also Photon Appearance Potential Spectroscopy. The deduced form of the conduction band d.o.s. is in qualitative accord with Painter and Ellis’s band calculations. C Webb, Vacuum, 27 (9), 1977,537-544. 36 3526. Secondary emission spectroscopy of solid surfaces. (USSR) Physical bases and possibilities of all methods of secondary emission spectroscopy of solid surfaces are considered. Instruments for secondary emission spectroscopy are described. Utilization of secondary emission spectroscopy is discussed. M V Gomoyunova, Zh Tekh Fiz, 46 (6), 1976, 1137-l 170 (in Russian).
36 3529. Thermal disorder of silver bromide studied by 100 keV proton channelling. (Germany) Channelling of 100 keV protons by the Rutherford backscattering technique in single crystals of AgBr is studied experimentally in the temperature range of 90 to 595 K. The results for the critical angle, the temperature dependence of the minimum yield and the dechannelling cross section of silver obtained from a thin evaporated metallic surface layer are presented. (France) M Roulet et al, Phys Sfafus Solidii (a), 35 (l), 1976,97-108. 36 3530. The influence of electron escape depth on the quantitative analysis by Auger spectroscopy. (USSR) It is shown that it is necessary to account the escape depth of Auger electrons at quantitative determination of chemical composition of surface by the Auger electron spectroscopy. Experimental determination of escape depth of Auger electrons with energies 50, 120 and 400 eV has been made with the aid of adsorption of In atoms on the (100) face of GaP and GaAs. It is found that the escape depth of 51 eV Auger electrons of Ga is about one monolayer, that of 120 eV Auger electrons of P is about 2.5 atomic layers and that of 403 eV Auger electrons of In in a thick In layer is about 4 atomic layers. The given calibration curves can be used for quantitative determination of chemical composition in the systems GaAs and GaP + In. A Yu Mityagin et al, Radiotekh Elektron, 21 (3), 1976, 589-493 (in Russian).
36 3531. Location of interstitial deuterium in TaD0.067 by channelling. (Germany) The channelling of a 750 keV 3He ion beam with an angular divergence of 0.05” in connection with a resonant nuclear reaction D(3He, p)“He was used for direct determination of the interstitial position of deuterium in TaDo.os, at room temperature. It is found that the majority (in excess of 90%) of deuterium atoms occupy the tetrahedral sites-in the b c c tantalum lattice. M Antonini and H D Carstanien. Phvs Sfalus Solidii (a). 34 (2). 1976 K153-K157. 36 3532. Application of secondary electron multipliers as detectors of ultrasoft radiation in X-ray microanalysers. (USSR) It is experimentally shown that open secondary electron multipliers with dynodes of Cu+ Be alloy and evaporated CsI photo-cathode on glass or aluminium substrates possess higher sensitivity of detection of ultrasoft X-radiation of light elements than flowing proportional counters usually used in X-ray microanalysers. A I Kozlenkov et al, Prib Tekh Eksper, No 1, 1976, 202-205 (in _I.
.,,
.,,
Russian).
36 3527. A study of relative energy losses of channelled protons in a tungsten single crystal. (Germany) The differences in the stopping of protons with incident energy of 6.3 MeV moving along the different crystallographic directions in tungsten are investigated. The energy spectra of protons scattered in tungsten single crystals with thickness of 40 to 80 pm were measured by a semiconductor spectrometer. Experimental results are discussed. (USSR) A S Rudnev, Phys Starus Solidii (a), 35 (l), 1976, K23-K27. 36 3528. High-resolution examination of uncoated insulators by SEM applied to grain boundaries in sodium chloride. (Germany) A technique for direct observation of grain boundaries in nonconducting alkali halide bicrystals by scanning electron microscope without using either conducting coatings or low-resolution low-voltage operation is described. The technique is based on the use of a backscattered electron detector in conjunction with an environmental cell. The electron detector consists of the wide-angle scintillator-light guide and a photomultiplier. Elimination of charging artefacts on an uncoated insulating specimen, when using the back-scattered electron detection mode of operation, requires the specimen to be surrounded by a residual vapour pressure of the order of 10-i torr. This mode of operation confirmed the existence in grain boundaries in nominally pure NaCl of second phase particles, the shape and distribution of these particles showing that the precipitation reaction can markedly influence boundary structure and properties. (England) L B Harris et al, Phys Stafus Solidi (a), 35 (l), 1976, 371-377.
37. INORGANIC CHEMISTRY, ANALYTICAL CHEMISTRY, DISTILLATION, MISCELLANEOUS CHEMICAL APPLICATIONS, OIL AND HYDROCARBON TECHNOLOGY 37 3533. Vacuum-microgravimetric characterization of catalyst candidates for fuel cell electrodes. (Germany) In the search for noble-metal-free cathode materials resistant to acid electrolytes and capable of catalysing the conversion of oxygen thermogravimetric methods have been used to determine the conditions of preparation, to analyse the chemical properties and to characterize the pore structure of the potential catalysts. The paper comprises results of investigations on inorganic compounds, such as ammonium tungstates, chromates, vanadates, molybdate and permanganate, and on organic polymers, such as polyamide nitriles, other CN polymers and polyacenoquinone pyrolysates. Von H Behret et al, Vakuunl-Tech, 26 (5), 1977, 147-148 (in German). 37 3534. The remote measurement of sulphur in steels by mass spectrametry. (GB) An experimental technique is described which enables steel to be typified by its sulphur content. A single laser pulse fired at the surface vaporizes a controlled amount of the sample. This is done in an oxidizing atmosphere like air, or carbon dioxide and sulphur dioxide is formed which can be pumped through a vacuum probe, typically 30 m long, and measured in a mass spectrometer. An expression iS derived describing the shape of the pulse of gas obtained and the 159