scholarly journals Graphite and Diamond Formation in the Carbide–Oxide–Carbonate Interactions (Experimental Modeling under Mantle P,T-Conditions)

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 522 ◽  
Author(s):  
Yuliya Bataleva ◽  
Yuri Palyanov ◽  
Yuri Borzdov ◽  
Ivan Novoselov ◽  
Oleg Bayukov
Keyword(s):  
Redox Reactions ◽  
Experimental Modeling ◽  
Silicate Melt ◽  
Diamond Growth ◽  
Potential Mechanism ◽  
Diamond Formation ◽  
Reducing Conditions ◽  
Reduction Of Co2 ◽  
Fluid Interactions

Experimental modeling of the formation of graphite and diamond as a result of carbide–fluid interactions was performed in the Fe3C–SiO2–Al2O3–(Mg,Ca)CO3 systems at 6.3 and 7.5 GPa and 1100–1650 °C. In the experiments with ƒO2-gradient (7.5 GPa, 1250–1350 °C), graphite + magnesiowüstite + garnet ± cohenite assemblage was formed. Graphite was produced through the redox interactions of carbide with carbonate or CO2 (reducing conditions), and redox reactions of magnesiowüstite and CO2 (oxidizing conditions). At 1450–1650 °C, crystallization of graphite, garnet, magnesiowüstite and ferrospinel, as well as generation of Fe2+,3+-rich carbonate–silicate melt occurred. This melt, saturated with carbon, acted as a medium of graphite crystallization and diamond growth on seeds. In the experiments without ƒO2-gradient (6.3 GPa), decarbonation reactions with the formation of CO2-fluid and Fe,Mg,Ca-silicates, as well as C0-producing redox reactions of CO2-fluid with cohenite were simultaneously realized. As a result, graphite (± diamond growth) was formed in assemblage with Fe2+,Fe3+,Mg-silicates and magnetite (1100–1200 °C), or with Fe3+-rich garnet and orthopyroxene (1300–1500 °C). It has been established that a potential mechanism for the crystallization of graphite or diamond growth is the oxidation of cohenite by CO2-fluid to FeO and Fe3O4, accompanied by the extraction of carbon from Fe3C and the corresponding reduction of CO2 to C0.

scholarly journals Experimental Modeling of Ankerite–Pyrite Interaction under Lithospheric Mantle P–T Parameters: Implications for Graphite Formation as a Result of Ankerite Sulfidation

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1267
Author(s):  
Yuliya V. Bataleva ◽  
Ivan D. Novoselov ◽  
Yuri M. Borzdov ◽  
Olga V. Furman ◽  
Yuri N. Palyanov
Keyword(s):  
High Pressure ◽  
Redox Reactions ◽  
Elemental Carbon ◽  
Iron Concentration ◽  
Experimental Modeling ◽  
Diamond Growth ◽  
Carbon Formation ◽  
Sulfide Melt ◽  
Redox Interaction ◽  
High Pressure Apparatus

Experimental modeling of ankerite–pyrite interaction was carried out on a multi-anvil high-pressure apparatus of a “split sphere” type (6.3 GPa, 1050–1550 °C, 20–60 h). At T ≤ 1250 °C, the formation of pyrrhotite, dolomite, magnesite, and metastable graphite was established. At higher temperatures, the generation of two immiscible melts (carbonate and sulfide ones), as well as graphite crystallization and diamond growth on seeds, occurred. It was established that the decrease in iron concentration in ankerite occurs by extraction of iron by sulfide and leads to the formation of pyrrhotite or sulfide melt, with corresponding ankerite breakdown into dolomite and magnesite. Further redox interaction of Ca,Mg,Fe carbonates with pyrrhotite (or between carbonate and sulfide melts) results in the carbonate reduction to C0 and metastable graphite formation (±diamond growth on seeds). It was established that the ankerite–pyrite interaction, which can occur in a downgoing slab, involves ankerite sulfidation that triggers further graphite-forming redox reactions and can be one of the scenarios of the elemental carbon formation under subduction settings.

scholarly journals Electron Inventory of the Iron-Sulfur Scaffold Complex HypCD Essential in [NiFe]-Hydrogenase Cofactor Assembly

2021 ◽  
Author(s):  
Sven T. Stripp ◽  
Jonathan Oltmanns ◽  
Christina S. Müller ◽  
David Ehrenberg ◽  
Ramona Schlesinger ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Redox Activity ◽  
Construction Site ◽  
Iron Ion ◽  
Paramagnetic Resonance ◽  
Iron Sulfur ◽  
Reducing Conditions ◽  
Reversible Redox ◽  
Electron Paramagnetic ◽  
Redox Conversion

The [4Fe-4S] cluster containing scaffold complex HypCD is the central construction site for the assembly of the [Fe](CN)2CO cofactor precursor of [NiFe]-hydrogenase. While the importance of the HypCD complex is well established, not much is known about the mechanism by which the CN– and CO ligands are transferred and attached to the iron ion. We developed an efficient protocol for the production and isolation of the functional HypCD complex that facilitated detailed spectroscopic investigations. The results obtained by UV/Vis-, electron paramagnetic Resonance (EPR)-, Resonance Raman-, Fourier-transform infrared (FTIR), and Mössbauer spectroscopy provide comprehensive evidence for an electron inventory fit to drive multi-electron redox reactions. We demonstrate the redox activity of the HypCD complex reporting the interconversion of the [4Fe-4S]2+/+ couple. Additionally, we observed a reversible redox conversion between the [4Fe-4S]2+ and a [3Fe-4S]+ cluster. MicroScale thermophoresis indicated preferable binding between the HypCD complex and its interaction partner HypEF under reducing conditions. Together, these results suggest a redox cascade involving the [4Fe-4S] cluster and a conserved disulfide bond of HypD that may facilitate the synthesis of the [Fe](CN)2CO cofactor precursor on the HypCD scaffold complex.

Diamond-coated carbon fiber

1994 ◽  
Vol 9 (3) ◽  
pp. 636-642 ◽  
Author(s):  
J. Ting ◽  
M.L. Lake
Keyword(s):  
Carbon Fiber ◽  
Microwave Plasma ◽  
Diamond Growth ◽  
Gas Mixture ◽  
Diamond Formation ◽  
Diamond Deposition ◽  
Diamond Nucleation ◽  
Pan Fiber ◽  
Coated Carbon ◽  
Pan Fibers

Diamond deposition was attempted on polyacrylonitrile (PAN) fiber and vapor grown carbon fiber (VGCF). PAN fibers were severely etched in a microwave plasma, whereas diamond was successfully deposited on VGCF. A diamond growth rate of 0.1 μm/h on VGCF was determined at a gas mixture of 99.9 sccm H2/0.1 sccm CH4 and a pressure of 30 Torr. It is proposed that diamond formation on VGCF occurs on not only the prism planes, but also the basal planes owing to the unique structure of VGCF. An explanation is proposed to explain diamond nucleation on the basal planes.

scholarly journals How do diamonds grow in metal melt together with silicate minerals? An experimental study of diamond morphology

2020 ◽  
Vol 32 (1) ◽  
pp. 41-55
Author(s):  
Aleksei Chepurov ◽  
Valery Sonin ◽  
Jean-Marie Dereppe ◽  
Egor Zhimulev ◽  
Anatoly Chepurov
Keyword(s):  
Natural Diamond ◽  
Diamond Growth ◽  
Chemical Compositions ◽  
Silicate Minerals ◽  
Metal Melt ◽  
Origin And Evolution ◽  
Metal Melts ◽  
Reducing Conditions ◽  
Diamond Crystallization ◽  
The Stability

Abstract. The origin and evolution of metal melts in the Earth's mantle and their role in the formation of diamond are the subject of active discussion. It is widely accepted that portions of metal melts in the form of pockets can be a suitable medium for diamond growth. This raises questions about the role of silicate minerals that form the walls of these pockets and are present in the volume of the metal melt during the growth of diamonds. The aim of the present work was to study the crystallization of diamond in a complex heterogeneous system: metal-melt–basalt–carbon. The experiments were performed using a multianvil high-pressure apparatus of split-sphere type (BARS) at a pressure of 5.5 GPa and a temperature of 1500 ∘C. The results demonstrated crystallization of diamond in metal melt together with garnet and clinopyroxene, whose chemical compositions are similar to those of eclogitic inclusions in natural diamond. We show that the presence of silicates in the crystallization medium does not reduce the chemical ability of metal melts to catalyze the conversion of graphite into diamond, and, morphologically, diamond crystallizes mainly in the form of a cuboctahedron. When the content of the silicate material in the system exceeds 5 wt %, diamond forms parallel-growth aggregates, but 15 wt % of silicate phases block the crystallization chamber, preventing the penetration of metallic melt into them, thus interrupting the growth of diamond. We infer that the studied mechanism of diamond crystallization can occur at lower-mantle conditions but could also have taken place in the ancient continental mantle of the Earth, under reducing conditions that allowed the stability of Fe–Ni melts.

scholarly journals Interaction of Corroding Iron with Eight Bentonites in the Alternative Buffer Materials Field Experiment (ABM2)

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 907
Author(s):  
Paul Wersin ◽  
Jebril Hadi ◽  
Andreas Jenni ◽  
Daniel Svensson ◽  
Jean-Marc Grenèche ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Hard Rock ◽  
High Spatial Resolution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rock Laboratory ◽  
Reducing Conditions ◽  
Buffer Material ◽  
High Level ◽  
Redox Evolution

Bentonite, a common smectite-rich buffer material, is in direct contact with corroding steel in many high-level radioactive waste repository designs. The interaction of iron with the smectite-rich clay may affect its swelling and sealing properties by processes such as alteration, redox reactions and cementation. The chemical interactions were investigated by analysing the Fe/clay interfaces of eight bentonite blocks which had been exposed to temperatures up to 130 °C for five years in the ABM2 borehole at the Äspö Hard Rock Laboratory managed by the Swedish Nuclear Fuel and Waste Management Co (SKB). Eleven interface samples were characterised by high spatial resolution methods, including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and μ-Raman spectroscopy as well as by “bulk” methods X-ray diffraction, X-ray fluorescence and 57Fe Mössbauer spectrometry. Corrosion induced an iron front of 5–20 mm into the bentonite, except for the high-Fe bentonite where no Fe increase was detected. This Fe front consisted mainly of ferric (oxyhydr)oxides in addition to the structural Fe in the smectite fraction which had been partially reduced by the interaction process. Fe(II) was also found to extend further into the clay, but its nature could not be identified. The consistent behaviour is explained by the redox evolution, which shifts from oxidising to reducing conditions during the experiment. No indication of smectite alteration was found.

Wüstite stability in the presence of a CO 2 -fluid and a carbonate-silicate melt: Implications for the graphite/diamond formation and generation of Fe-rich mantle metasomatic agents

Lithos ◽  
2016 ◽  
Vol 244 ◽  
pp. 20-29 ◽  
Author(s):  
Yuliya V. Bataleva ◽  
Yuri N. Palyanov ◽  
Alexander G. Sokol ◽  
Yuri M. Borzdov ◽  
Oleg A. Bayukov
Keyword(s):  
Silicate Melt ◽  
Diamond Formation

Methyl versus acetylene as diamond growth species

1990 ◽  
Vol 5 (11) ◽  
pp. 2313-2319 ◽  
Author(s):  
Stephen J. Harris ◽  
L. Robbin Martin
Keyword(s):  
Diamond Film ◽  
Diamond Films ◽  
Hydrogen Gas ◽  
Diamond Growth ◽  
Silicon Substrates ◽  
Methyl Radicals ◽  
Diamond Formation ◽  
Detailed Chemistry ◽  
Concentration Diffusion

We have modeled plasma-assisted diamond growth on substrates placed in a high velocity 1-dimensional flow. The gas consisted of methane or acetylene injected into a flow of partially dissociated hydrogen gas at 800 °C. Diamond is formed only near the injector. More diamond is formed when methane is the additive, and Raman spectra show that the quality of the diamond films is also higher when methane is the additive. The model, which includes detailed chemistry, convection, concentration diffusion, and thermal diffusion, shows that with this experimental arrangement only methane and methyl radicals are present in significant quantities when methane is added, while only acetylene is present when acetylene is added. We conclude that (1) Diamond films can be grown directly from methyl radicals (or, possibly, from methane) and from acetylene. This suggests that a variety of hydrocarbons could act as growth species. (2) An environment containing methane and methyl is much more effective for growing diamond films than one containing acetylene. (3) The quality of the diamond film depends on the identity of the growth species, with acetylene producing lower quality films than methyl (or methane). (4) The fall-off in diamond formation with distance from the injector is due to destruction of species crucial to diamond growth on the silicon substrates.

scholarly journals Sulfide Formation as a Result of Sulfate Subduction into Silicate Mantle (Experimental Modeling under High P,T-Parameters)

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 373 ◽  
Author(s):  
Yuliya Bataleva ◽  
Yuri Palyanov ◽  
Yuri Borzdov
Keyword(s):  
Experimental Study ◽  
High Pressure ◽  
Lithospheric Mantle ◽  
Experimental Modeling ◽  
Silicate Melt ◽  
Free System ◽  
Oxide Melt ◽  
High Pressure Apparatus

Ca,Mg-sulfates are subduction-related sources of oxidized S-rich fluid under lithospheric mantle P,T-parameters. Experimental study, aimed at the modeling of scenarios of S-rich fluid generation as a result of desulfation and subsequent sulfide formation, was performed using a multi-anvil high-pressure apparatus. Experiments were carried out in the Fe,Ni-olivine–anhydrite–C and Fe,Ni-olivine–Mg-sulfate–C systems (P = 6.3 GPa, T of 1050 and 1450 °C, t = 23–60 h). At 1050 °C, the interaction in the olivine–anhydrite–C system leads to the formation of olivine + diopside + pyrrhotite assemblage and at 1450 °C leads to the generation of immiscible silicate-oxide and sulfide melts. Desulfation of this system results in the formation of S-rich reduced fluid via the reaction olivine + anhydrite + C → diopside + S0 + CO2. This fluid is found to be a medium for the recrystallization of olivine, extraction of Fe and Ni, and subsequent crystallization of Fe,Ni-sulfides (i.e., olivine sulfidation). At 1450 °C in the Ca-free system, the generation of carbonate-silicate and Fe,Ni-sulfide melts occurs. Formation of the carbonate component of the melt occurs via the reaction Mg-sulfate + C → magnesite + S0. It is experimentally shown that the olivine-sulfate interaction can result in mantle sulfide formation and generation of potential mantle metasomatic agents—S- and CO2-dominated fluids, silicate-oxide melt, or carbonate-silicate melt.

scholarly journals Laboratory study of spectral induced polarization responses of magnetite — Fe2+ redox reactions in porous media

Geophysics ◽  
2014 ◽  
Vol 79 (1) ◽  
pp. D21-D30 ◽  
Author(s):  
Christopher G. Hubbard ◽  
L. Jared West ◽  
Juan Diego Rodriguez-Blanco ◽  
Samuel Shaw
Keyword(s):  
Redox Reactions ◽  
Induced Polarization ◽  
Phase Response ◽  
Field Surveys ◽  
Spectral Induced Polarization ◽  
Reducing Conditions ◽  
Redox Active ◽  
Large Phase ◽  
Ph Range

Spectral induced polarization (SIP) phase anomalies in field surveys at contaminated sites have previously been shown to correlate with the occurrence of chemically reducing conditions and/or semiconductive minerals, but the reasons for this are not fully understood. We report a systematic laboratory investigation of the role of the semiconductive mineral magnetite and its interaction with redox-active versus redox-inactive ions in producing such phase anomalies. The SIP responses of quartz sand with 5% magnetite in solutions containing redox-inactive [Formula: see text] and [Formula: see text] versus redox-active [Formula: see text] were measured across the pH ranges corresponding to adsorption of these metals to magnetite. With redox inactive ions [Formula: see text] and [Formula: see text], SIP phase response showed no changes across the pH range 4–10, corresponding to their adsorption, showing [Formula: see text] anomalies peaking at [Formula: see text]–74 Hz. These large phase anomalies are probably caused by polarization of the magnetite-solution interfaces. With the redox-active ion [Formula: see text], frequency of peak phase response decreased progressively from [Formula: see text] to [Formula: see text] as effluent pH increased from four to seven, corresponding to progressive adsorption of [Formula: see text] to the magnetite surface. The latter frequency (3 Hz) corresponds approximately with those of phase anomalies detected in field surveys reported elsewhere. We conclude that pH sensitivity arises from redox reactions between [Formula: see text] and magnetite surfaces, with transfer of electrical charge through the bulk mineral, as reported in other laboratory investigations. Our results confirm that SIP measurements are sensitive to redox reactions involving charge transfers between adsorbed ions and semiconductive minerals. Phase anomalies seen in field surveys of groundwater contamination and biostimulation may therefore be indicative of iron-reducing conditions, when semiconductive iron minerals such as magnetite are present.

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