Pyrite is the most common among the group of sulfide minerals in the Earth and abundant in most geological settings. This gangue mineral in association with garnet, hematite, magnetite, and other sulfide minerals acts as an indicator mineral in the Kubi concession of the Asante Gold corporation in Ghana. X-ray diffraction (XRD), air annealing in a furnace, energy-dispersive x-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were applied to investigate the crystal structure, identify individual elements, permanence, transformation, and chemical/electronic properties of such pyrite. The study aims to identify individual elements and to gain an understanding of the surface reaction mechanisms, as well as the properties of precipitated pyrite particles observed during the hydrothermal formation of the ore deposit. XRD shows that pristine and annealed samples contain some hematite and quartz besides pyrite. Results from air annealing indicate that the relationship between pyrite and hematite-magnetite is controlled by temperature. EDX reveals that the sample has O and C as contaminants, while XPS in addition reveals Ba, Au, P, Al, and N. These elements are attributed to pyrite that bonds metallically or covalently to neighboring ligands/impurity minerals such as oxides, chalcogenide sulfides, as well as the gangue alteration minerals of magnetite and hematite in the pyrite sample.

These findings suggest that during the hydrothermal flow regime, pyrite, pathfinder elements, and impurity minerals/metals were in contact with quartz minerals before undergoing hematite transformation, which thus becomes an indicator mineral in the Kubi gold concession.

Altered and gangue quartz in hydrothermal veins from the Kubi Gold deposit in Dunkwa on Offin in the central region of Ghana are investigated for possible Au-associated indicator minerals and to provide the understanding and increase the knowledge of the mineral hosting and alteration processes in quartz. X-ray diffraction, air annealing furnace, differential scanning calorimetry, energy dispersive X-ray spectroscopy, and transmission electron microscopy have been applied on different quartz types outcropping from surface and bedrocks at the Kubi Gold Mining to reveal the material properties at different temperatures. From the diffraction results of the fresh and annealed quartz samples, we find that the samples contain indicator and the impurity minerals iron disulfide, biotite, titanium oxide, and magnetite. These minerals, under oxidation process between 574 and 1400 °C temperatures experienced hematite alterations and a transformation from α-quartz to β-quartz and further to cristobalite as observed from the calorimetry scans for hydrothermally exposed materials. The energy dispersive spectroscopy revealed elemental components of Fe, S, Mg, K, Al, Ti, Na, Si, O, and Ca contained in the samples, and these are attributed to the impurity phase minerals observed in the diffraction. The findings also suggest that during the hydrothermal flow regime, impurity minerals and metals can be trapped by voids and faults. Under favorable temperature conditions, the trapped minerals can be altered to change color at different depositional stages by oxidation and reduction processes leading to hematite alteration which is a useful indicator minerals in mineral exploration.

The Au mineralization in the Kubi Gold Mining Area in the Birimian of Ghana is associated with garnet (about 85 vol.%), magnetite, pyrrhotite, arsenopyrite, and sulfide minerals, as well as quartz with gold and calcite. These minerals and the included elements can act as indicator minerals or pathfinder elements. For the present work, we collected samples from drill holes at different depths, from the alluvial zone (0–45 m) to the ore zone (75–100 m). The distributions of minerals and elements in the rocks that act as indicator minerals and pathfinder elements in the concession area were investigated along the drill hole cross sections. X-ray diffraction shows that the samples contain garnet, pyrite, periclase, and quartz as the main indicator minerals. By energy-dispersive X-ray spectroscopy, Fe, Mg, Al, S, O, Mn, Na, Cu, Si, and K are identified as corresponding pathfinder elements. The results indicate that the Au mineralization in the Kubi Mine area correlates mostly with the occurrence of garnet, pyrite, goethite, and kaolinite in the host rocks, which show towards the surface increasingly hematitic and limonitic alteration in form of Fe(oxy-)hydroxides.

We investigate the effects of substrate bias on cathodic arc deposition of Cr coatings without external substrate heating at four different substrate bias levels, floating, −30, −50, and −70 V. After 10 min of deposition, the substrate temperature reaches 180, 210, 230, and 260 °C for floating potential, −30, −50, and −70 V, respectively. Time-of-flight energy elastic recoil detection analysis shows that all grown coatings are of high purity, with no coating containing more than 0.2 at.% of C and/or O. Increasing the substrate bias also reduces the number of macroparticles, steers the texture from preferred [110]- to [100]-orientation and induces a residual compressive stress of ∼450 MPa in the coatings. The hardness of the coatings remains at a constant 7.5 GPa irrespective of the substrate bias. The four-point probe resistivity of the grown coatings is 15–17 μΩcm regardless of substrate bias, close to the 12.9 μΩcm of bulk Cr.

Epitaxial growth of ZrB2 films on Si(100) substrates at 900 degrees C is demonstrated using direct-current magnetron sputter deposition from sintered ZrB2 targets. This case of epitaxial growth is structurally more challenging than on Si(111), 4 H-SiC(001), and Al2O3(001). From pole figure measurements, two epitaxial relationships are determined: A) in-plane: ZrB 2 [ 001 ] parallel to Si [ 110 ] and ZrB 2 [ 110 ] parallel to Si [ 110 ] , out-of-plane: ZrB 2 ( 100 ) parallel to Si ( 100 ) , and B) in-plane: ZrB 2 [ 1 2 over bar 1 ] parallel to Si [ 110 ] and the same multiply rotated 90 degrees around the 102 axis, out of plane: ZrB 2 ( 102 ) parallel to Si ( 100 ) . From full width at half maximum (FWHM) values from rocking curve measurements (omega-scans) of the 100 and 102 peaks, a measure of epitaxial quality for these two preferred orientations is obtained. Both omega-scans and theta/2 theta diffractograms show higher quality for the A-type with a FWHM value of 2.00 degrees compared with 4.97 degrees for the B-type. The film composition is found to be ZrB2.3 from time-of-flight elastic recoil detection analysis. The B-type crystallographic relationship ZrB 2 ( 102 ) parallel to Si ( 100 ) and ZrB 2 [ 1 2 over bar 0 ] parallel to Si [ 110 ] has not been previously reported.

We review the thin film growth, chemistry, and physical properties of Group 4-6 transition-metal diboride (TMB2) thin films with AlB2-type crystal structure (Strukturbericht designation C32). Industrial applications are growing rapidly as TMB2 begin competing with conventional refractory ceramics like carbides and nitrides, including pseudo-binaries such as Ti1-xAlxN. The TMB2 crystal structure comprises graphite-like honeycombed atomic sheets of B interleaved by hexagonal close-packed TM layers. From the C32 crystal structure stems unique properties including high melting point, hardness, and corrosion resistance, yet limited oxidation resistance, combined with high electrical conductivity. We correlate the underlying chemical bonding, orbital overlap, and electronic structure to the mechanical properties, resistivity, and high-temperature properties unique to this class of materials. The review highlights the importance of avoiding contamination elements (like oxygen) and boron segregation on both the target and substrate sides during sputter deposition, for better-defined properties, regardless of the boride system investigated. This is a consequence of the strong tendency for B to segregate to TMB2 grain boundaries for boron-rich compositions of the growth flux. It is judged that sputter deposition of TMB2 films is at a tipping point towards a multitude of applications for TMB2 not solely as bulk materials, but also as protective coatings and electrically conducting high-temperature stable thin films.

Boron carbide in its rhombohedral form (r-BxC), commonly denoted B4C or B13C2, is a well-known hard material, but it is also a potential semiconductor material. We deposited r-BxC by chemical vapor deposition between 1100 degrees C and 1500 degrees C from triethylboron in H-2 on 4H-SiC(0001) and 4H-SiC(0001). We show, using ToF-ERDA, that pure B4C was grown at 1300 degrees C, furthermore, using XRD that graphite forms above 1400 degrees C. The films deposited above 1300 degrees C on 4H-SiC(0001) were found to be epitaxial, with the epitaxial relationships B4C(0001)[1010]||4H-SiC(0001)[1010] obtained from pole figure measurements. In contrast, the films deposited on 4H-SiC(0001) were polycrystalline. We suggest that the difference in growth mode is explained by the difference in the ability of the different surfaces of 4H-SiC to act as carbon sources in the initial stages of the film growth.

X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) are applied to investigate the properties of fine-grained concentrates on artisanal, small-scale gold mining samples from the Kubi Gold Project of the Asante Gold Corporation near Dunwka-on-Offinin the Central Region of Ghana. Both techniques show that the Au-containing residual sediments are dominated by the host elements Fe, Ag, Al, N, O, Si, Hg, and Ti that either form alloys with gold or with inherent elements in the sediments. For comparison, a bulk nugget sample mainly consisting of Au forms an electrum, i.e., a solid solution with Ag. Untreated (impure) sediments, fine-grained Au concentrate, coarse-grained Au concentrate, and processed ore (Au bulk/nugget)samples were found to contain clusters of O, C, N, and Ag, with Au concentrations significantly lower than that of the related elements. This finding can be attributed to primary geochemical dispersion, which evolved from the crystallization of magma and hydrothermal liquids as well as the migration of metasomatic elements and the rapid rate of chemical weathering of lateralization in secondary processes. The results indicate that Si and Ag are strongly concomitant with Au because of their eutectic characteristics, while N, C, and O follow alongside because of their affinity to Si. These non-noble elements thus act as pathfinders for Au ores in the exploration area. This paper further discusses relationships between gold and sediments of auriferous lodes as key to determining indicator minerals of gold in mining sites.

The microstructure of stoichiometric ZrB2.0 and B over-stoichiometric ZrB2.5 thin films has been studied using atom probe tomography (APT), X-ray diffraction, and transmission electron microscopy. Both films consist of columnar ZrB2 grains with AlB2-type crystal structure. The narrow stoichiometry range of ZrB2 results in the presence of separate disordered B-rich boundaries even in ZrB2.0. At higher average B content, specifically ZrB2.5, the formation of a continuous network around the sides of the ZrB2 columns is promoted. In addition, the APT field evaporation characteristics of ZrB2 and its influence on the measured local composition has been studied and compared to the average composition from elastic recoil detection analysis (ERDA). Differences in the measured average compositions of the two techniques are explained by the APT detector dead-time/space. A new pile-up pairs correction procedure based on co-evaporation correlation data was thus employed here for the APT data and compared with the 10B-method (the B equivalence of the 13C-method), as well as the combination of both methods. In ZrB2.0, all of the applied compositional correction methods were found to reduce the compositional difference when appropriate isotopic abundances were used. In ZrB2.5, the inhomogeneity of the film likely increased the local APT composition to such an extent that even conservative correction procedures overestimated the B content compared to the ERDA reference. The strengths of the pile-up pairs correction compared the 10B and the combined methods are higher precision, due to it being less dependent on the accuracy of estimated isotopic abundances, and that the correction itself is not dependent on careful background correction of the mass spectrum.

The authors investigate sputtering of a Ti₃SiC₂ compound target at temperatures ranging from RT (no applied external heating) to 970 °C as well as the influence of the sputtering power at 850 °C for the deposition of Ti₃SiC₂ films on Al₂O₃(0001) substrates. Elemental composition obtained from time-of-flight energy elastic recoil detection analysis shows an excess of carbon in all films, which is explained by differences in the angular distribution between C, Si, and Ti, where C scatters the least during sputtering. The oxygen content is 2.6 at. % in the film deposited at RT and decreases with increasing deposition temperature, showing that higher temperatures favor high purity films. Chemical bonding analysis by x-ray photoelectron spectroscopy shows C–Ti and Si–C bonding in the Ti₃SiC₂ films and Si–Si bonding in the Ti₃SiC₂ compound target. X-ray diffraction reveals that the phases Ti₃SiC₂, Ti₄SiC₃, and Ti₇Si₂C₅ can be deposited from a Ti₃SiC₂ compound target at substrate temperatures above 850 °C and with the growth of TiC and the Nowotny phase Ti₅Si₃C_x at lower temperatures. High-resolution scanning transmission electron microscopy shows epitaxial growth of Ti₃SiC₂, Ti₄SiC₃, and Ti₇Si₂C₅ on TiC at 970 °C. Four-point probe resistivity measurements give values in the range ∼120 to ∼450 μΩ cm and with the lowest values obtained for films containing Ti₃SiC₂, Ti₄SiC₃, and Ti₇Si₂C₅.