Electronic structure of hollow graphitic carbon nanoparticles made from acetylene carbon black

The electronic structure of hollow graphitic carbon nanoparticles obtained by catalytic graphitization of acetylene carbon black (ACB HGCNs) was studied by ultra-soft X-ray emission spectroscopy (USXES) method. The phases of the carbon powder samples were determined by XRD with monochromatic CuKα1 radiation. Transmission electron microscopy was used to study the ACB HGCN spatial structures and morphologies. The electronic structures of reference Q-graphenes and HGCNs obtained from iron carbide filled carbon nanocapsules (Fe3C@CNCs) which were synthesized by plasma method in hexane were measured for comparison with that of the synthesized ACB HGCNs

Electronic structure of hollow graphitic carbon nanoparticles made from acetylene carbon black

The electronic structure of hollow graphitic carbon nanoparticles obtained by catalytic graphitization of acetylene carbon black (ACB HGCNs) was studied by ultra-soft X-ray emission spectroscopy (USXES) method. The phases of the carbon powder samples were determined by XRD with monochromatic CuKα1 radiation. Transmission electron microscopy was used to study the ACB HGCN spatial structures and morphologies. The electronic structures of reference Q-graphenes and HGCNs obtained from iron carbide filled carbon nanocapsules (Fe3C@CNCs) which were synthesized by plasma method in hexane were measured for comparison with that of the synthesized ACB HGCNs

Subsurface mapping of Rustenburg Layered Suite (RLS), Bushveld Complex, South Africa : inferred structural features using borehole data and spatial analysis

Faults and other structural features within the mafic-ultramafic layers of the Bushveld Complex have been a major issue mainly for exploration and mine planning. This study employed a new approach in detecting faults with both regional and meter scale offsets, which was not possible with the usually applied structure contour mapping. Interpretations of faults from structural and isopach maps were previously based on geological experience, while meter-scale faults were virtually impossible to detect from such maps. Spatial analysis was performed using borehole data primarily. This resulted in the identification of previously known structures and other hitherto unsuspected structural features. Consequently, the location, trends, and geometry of faults and some regional features within the Rustenburg Layered Suite (RLS) that might not be easy to detect through field mapping are adequately described in this study.The University of Pretoria and the Federal University of Technology, Akure through the ETF initiative.http://www.elsevier.com/locate/jafrearsci2018-08-30Geolog

Microstructural evolution and trace element mobility in Witwatersrand pyrite

Microstructural analysis of pyrite from a single sample of Witwatersrand conglomerate indicates a complex deformation history involving components of both plastic and brittle deformation. Internal deformation associated with dislocation creep is heterogeneously developed within grains, shows no systematic relationship to bulk rock strain or the location of grain boundaries and is interpreted to represent an episode of pyrite deformation that predates the incorporation of detrital pyrite grains into the Central Rand conglomerates. In contrast, brittle deformation, manifest by grain fragmentation that transects dislocation-related microstructures, is spatially related to grain contacts and is interpreted to represent post-depositional deformation of the Central Rand conglomerates. Analysis of the low-angle boundaries associated with the early dislocation creep phase of deformation indicates the operation of {100} slip systems. However, some orientation boundaries have geometrical characteristics that are not consistent with simple {100} deformation.These boundaries may represent the combination of multiple slip systems or the operation of the previously unrecognized {120} slip system. These boundaries are associated with order of magnitude enrichments in As, Ni and Co that indicate a deformation control on the remobilization of trace elements within pyrite and a potential slip system control on the effectiveness of fast-diffusion pathways. The results confirm the importance of grain-scale elemental remobilization within pyrite prior to their incorporation into the Witwatersrand gold-bearing conglomerates. Since the relationship between gold and pyrite is intimately related to the trace element geochemistry of pyrite, the results have implications for the application of minor element geochemistry to ore deposit formation, suggest a reason for heterogeneous conductivity and localized gold precipitation in natural pyrite and provide a framework for improving mineral processing

X-ray Photoelectron Spectroscopy Study of Electronic Structure of Graphene Nanosheets

Investigations of graphene nanosheets and oxidized graphene nanosheets were carried out using X-rayphotoelectron spectroscopy. Scanning and transmission electron microscopy investigations were used in additionto X-ray photoelectron spectroscopy. It was found that functional carboxyl and epoxide groups were removedfrom samples due to argon bombardment in studies of oxidized graphene nanosheets with X-ray photoelectronspectroscopy. Thus the ОKα-band was not revealed in oxidized graphene nanosheets owing to oxygen removaldue to electron bombardment with the use of. ultra-soft X-ray emission spectroscopy. Keywords: X-ray photoelectron spectroscopy, electronic structure, graphene nanosheets, oxidized graphenenanosheets

Gold accumulation in the archaean witwatersrand basin, south africa-evidence from concentrically laminated pyrite

Concentrically laminated pyrite is a relatively common, although volumetrically minor, component of auriferous conglomerates in the Archaean (ca. 3.0-2.7Ga) Witwatersrand Basin of South Africa. This type of pyrite contains high amounts (several tens of ppm) of Au, but the origin of the pyrite is debated, and the timing of Au deposition in these grains is not known. In order to constrain the formation of pyrite, we have studied concentrically laminated pyrite and other coexisting types of pyrite (inclusion-rich, massive pyrite) by analysing the contents and distribution of Au and other trace elements by laser ablation ICP-MS, the S and Fe isotope composition by SIMS, and the mineral inclusions by scanning electron microscope and laser Raman spectroscopy. Trace element maps indicate that concentrically laminated pyrite is enriched in Sb, Mn, Au, Ag, Tl, Cu, Mo, Mn, and contains two types of gold: finely dispersed Au ("invisible gold", with Au/Ag ~0.1 and likely of primary origin) and Au inclusions with Au/Ag ~10 of secondary origin. The study of mineral inclusions revealed the presence of muscovite, chlorite, fine-grained carbonaceous matter, monazite, Ti-oxides, and quartz. Iron and multiple S isotopes suggest that concentrically laminated pyrite and inclusion-rich pyrite were formed from two separate pools of S and Fe with different isotope characteristics. Sulfur was derived from atmospheric S that had undergone mass-independent isotope fractionation to form SO42- with negative d33S that constituted concentrically laminated pyrite, and elemental S with positive d33S that formed inclusion-rich pyrite. Iron pools were derived from partial oxidation of Fe2+, so that concentrically laminated pyrite formed from a low-d56Fe residual Fe2+ (average +0.2‰) and inclusion-rich pyrite formed from a high-d56Fe Fe3+ pool (average +2.7‰). Biological activity may have been involved in the reduction of SO42-, causing a wide spread of d34S values (~25‰, S reducing microorganisms), as well as in the partial oxidation of Fe2+ (anaerobic photosynthetic Fe reducers or photosynthetic O2 producers), and in the formation of pyrite from Fe3+ (dissimilatory Fe reducers). We propose that concurrent biogenically-mediated pyrite formation and Au trapping suggest that microbial activity was responsible for the accumulation of Au and other trace elements (e.g. Sb, Mn, Ag, Tl, Cu, Mo, Mn) which are commonly enriched in organic matter-rich sediments