Journal articles on the topic 'Interface coupled dissolution-reprecipitation reactions'
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Zhao, Jing, and Allan Pring. "Mineral Transformations in Gold–(Silver) Tellurides in the Presence of Fluids: Nature and Experiment." Minerals 9, no. 3 (March 9, 2019): 167. http://dx.doi.org/10.3390/min9030167.
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Gold–(silver) telluride minerals constitute a major part of the gold endowment at a number of important deposits across the globe. A brief overview of the chemistry and structure of the main gold and silver telluride minerals is presented, focusing on the relationships between calaverite, krennerite, and sylvanite, which have overlapping compositions. These three minerals are replaced by gold–silver alloys when subjected to the actions of hydrothermal fluids under mild hydrothermal conditions (≤220 °C). An overview of the product textures, reaction mechanisms, and kinetics of the oxidative leaching of tellurium from gold–(silver) tellurides is presented. For calaverite and krennerite, the replacement reactions are relatively simple interface-coupled dissolution-reprecipitation reactions. In these reactions, the telluride minerals dissolve at the reaction interface and gold immediately precipitates and grows as gold filaments; the tellurium is oxidized to Te(IV) and is lost to the bulk solution. The replacement of sylvanite is more complex and involves two competing pathways leading to either a gold spongy alloy or a mixture of calaverite, hessite, and petzite. This work highlights the substantial progress that has been made in recent years towards understanding the mineralization processes of natural gold–(silver) telluride minerals and mustard gold under hydrothermal conditions. The results of these studies have potential implications for the industrial treatment of gold-bearing telluride minerals.
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Renard, François, Anja Røyne, and Christine V. Putnis. "Timescales of interface-coupled dissolution-precipitation reactions on carbonates." Geoscience Frontiers 10, no. 1 (January 2019): 17–27. http://dx.doi.org/10.1016/j.gsf.2018.02.013.
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Janssen, A., A. Putnis, T. Geisler, and C. V. Putnis. "The experimental replacement of ilmenite by rutile in HCl solutions." Mineralogical Magazine 74, no. 4 (August 2010): 633–44. http://dx.doi.org/10.1180/minmag.2010.074.4.633.
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AbstractTo determine the mechanism of acid-leaching of ilmenite to ultimately forming rutile, we have carried out an experimental study of ilmenite alteration in autoclaves at 150ºC in HCl solutions. The resulting products were studied by X-ray diffraction, scanning electron microscopy, electron microprobe and Raman spectroscopy. In some experiments the solution was initially enriched in 18O and the distribution of the isotope in the alteration products mapped from the frequency shift of cation oxygen stretching bands in the Raman spectra. The alteration begins at the original ilmenite crystal surface and has also taken place along an intricate branching network of fractures in the ilmenite, generated by the reaction. Element-distribution maps and chemical analyses of the reaction product within the fractures show marked depletion in Fe and Mn and a relative enrichment of Ti. Chemical analyses however, do not correspond to any stoichiometric composition, and may represent mixtures of TiO2 and Fe2O3. The fracturing is possibly driven by volume changes associated with dissolution of ilmenite and simultaneous reprecipitation of the product phases (including rutile) from an interfacial solution along an inward moving dissolution-reprecipitation front. Raman spectroscopy shows that the 18O is incorporated in the rutile structure during the recrystallization. Throughout the alteration process, the original morphology of the ilmenite is preserved although the product is highly porous. The rutile inherits crystallographic information from the parent ilmenite, resulting in a triply-twinned rutile microstructure. The results indicate that the ilmenite is replaced directly by rutile without the formation of any intermediate reaction products. The reaction is described in terms of an interface-coupled dissolution-precipitation mechanism.
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Rao, Ashit, Subhash C. Ayirala, Mohammed B. Alotaibi, Michel H. G. Duits, A. A. Yousef, and Frieder Mugele. "Nonmonotonic Coupled Dissolution‐Precipitation Reactions at the Mineral–Water Interface." Advanced Functional Materials 31, no. 51 (October 5, 2021): 2106396. http://dx.doi.org/10.1002/adfm.202106396.
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Hövelmann, Jörn, Christine Putnis, and Liane Benning. "Metal Sequestration through Coupled Dissolution–Precipitation at the Brucite–Water Interface." Minerals 8, no. 8 (August 10, 2018): 346. http://dx.doi.org/10.3390/min8080346.
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The increasing release of potentially toxic metals from industrial processes can lead to highly elevated concentrations of these metals in soil, and ground- and surface-waters. Today, metal pollution is one of the most serious environmental problems and thus, the development of effective remediation strategies is of paramount importance. In this context, it is critical to understand how dissolved metals interact with mineral surfaces in soil–water environments. Here, we assessed the processes that govern the interactions between six common metals (Zn, Cd, Co, Ni, Cu, and Pb) with natural brucite (Mg(OH)2) surfaces. Using atomic force microscopy and a flow-through cell, we followed the coupled process of brucite dissolution and subsequent nucleation and growth of various metal bearing precipitates at a nanometer scale. Scanning electron microscopy and Raman spectroscopy allowed for the identification of the precipitates as metal hydroxide phases. Our observations and thermodynamic calculations indicate that this coupled dissolution–precipitation process is governed by a fluid boundary layer at the brucite–water interface. Importantly, this layer differs in composition and pH from the bulk solution. These results contribute to an improved mechanistic understanding of sorption reactions at mineral surfaces that control the mobility and fate of toxic metals in the environment.
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Rao, Ashit, Subhash C. Ayirala, Mohammed B. Alotaibi, Michel H. G. Duits, A. A. Yousef, and Frieder Mugele. "Nonmonotonic Coupled Dissolution‐Precipitation Reactions at the Mineral‐Water Interface (Adv. Funct. Mater. 51/2021)." Advanced Functional Materials 31, no. 51 (December 2021): 2170379. http://dx.doi.org/10.1002/adfm.202170379.
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Kontonikas-Charos, Alkis, Cristiana L. Ciobanu, Nigel J. Cook, Kathy Ehrig, Roniza Ismail, Sasha Krneta, and Animesh Basak. "Feldspar mineralogy and rare-earth element (re)mobilization in iron-oxide copper gold systems from South Australia: a nanoscale study." Mineralogical Magazine 82, S1 (February 28, 2018): S173—S197. http://dx.doi.org/10.1180/minmag.2017.081.040.
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ABSTRACTNanoscale characterization (TEM on FIB-SEM-prepared foils) was undertaken on feldspars undergoing transformation from early post-magmatic (deuteric) to hydrothermal stages in granites hosting the Olympic Dam Cu-U-Au-Ag deposit, and from the Cu-Au skarn at Hillside within the same iron-oxide copper-gold (IOCG) province, South Australia. These include complex perthitic textures, anomalously Ba-, Fe-, or REE-rich compositions, and REE-flourocarbonate + molybdenite assemblages which pseudomorph pre-existing feldspars. Epitaxial orientations between cryptoperthite (magmatic), patch perthite (dueteric) and replacive albite (hydrothermal) within vein perthite support interface-mediated reactions between pre-existing alkali-feldspars and pervading fluid, irrespective of micro-scale crystal morphology. Such observations are consistent with a coupled dissolution-reprecipitation reaction mechanism, which assists in grain-scale element remobilization via the generation of transient interconnected microporosity. Micro-scale aggregates of hydrothermal hyalophane (Ba-rich K-feldspar), crystallizing within previously albitized areas of andesine, reveal a complex assemblage of calc-silicate, As-bearing fluorapatite and Fe oxides along reaction boundaries in the enclosing albite-sericite assemblage typical of deuteric alteration. Such inclusions are good REE repositories and their presence supports REE remobilization at the grain-scale during early hydrothermal alteration. Iron-metasomatism is recognized by nanoscale maghemite inclusions within ‘red-stained’ orthoclase, as well as by hematite in REE-fluorocarbonates, which reflect broader-scale zonation patterns typical for IOCG systems. Potassium-feldspar from the contact between alkali-granite and skarn at Hillside is characterized by 100–1000 ppm REE, attributable to pervasive nanoscale inclusions of calc-silicates, concentrated along microfractures, or pore-attached. Feldspar replacement by REE-fluorcarbonates at Olympic Dam and nanoscale calc-silicate inclusions in feldspar at Hillside are both strong evidence for the role of feldspars in concentrating REE during intense metasomatism. Differences in mineralogical expression are due to the availability of associated elements. Lattice-scale intergrowths of assemblages indicative of Fe-metasomatism, REE-enrichment and sulfide deposition at Olympic Dam are evidence for a spatial and temporal relationship between these processes.
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Kasioptas, A., C. Perdikouri, C. V. Putnis, and A. Putnis. "Pseudomorphic replacement of single calcium carbonate crystals by polycrystalline apatite." Mineralogical Magazine 72, no. 1 (February 2008): 77–80. http://dx.doi.org/10.1180/minmag.2008.072.1.77.
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AbstractDuring chemical weathering and natural hydrothermal reactions, apatite can form by replacing calcium carbonates. In hydrothermal experiments in which aragonite and calcite single crystals have been reacted with phosphate solutions, the carbonates are replaced by polycrystalline hydroxylapatite (HAP). In both cases the crystals have retained their overall morphology while their compositions have changed significantly. The HAP appears to have a crystallographic relationship to the parent carbonate crystals. The textural relationships are consistent with an interface-coupled dissolution-precipitation mechanism. Structural relationships and relative molar volumes and solubilities appear to be factors that greatly affect replacement reactions.
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Ebert, William L. "Glass Degradation in Performance Assessment Models1." MRS Proceedings 1744 (2015): 163–72. http://dx.doi.org/10.1557/opl.2015.333.
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ABSTRACTThe interface with reactive transport models used in performance assessment calculations is described to identify aspects of the glass waste form degradation model important to long-term predictions. These are primarily the conditions that trigger the change from the residual rate to the Stage 3 rate and the values of those rates. Although the processes triggering the change and controlling the Stage 3 rate are not yet understood mechanistically, neither appears related to an intrinsic property of the glass. The sudden and usually significant increase in the glass dissolution rate suggests the processes that trigger the increase are different than the processes controlling glass dissolution prior to that change. Application of a simple expression that was derived for mineral transformation to represent the kinetics of coupled glass dissolution and secondary phase precipitation reactions is shown to be consistent with experimental observations of Stage 3 and useful for modeling long-term glass dissolution in a complex disposal environment.
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Bin Mohamad Sultan, Borhan, Dominique Thierry, and Kevin Ogle. "Aluminum Alloy Etching: New Insights By Element Resolved Electrochemical Analysis." ECS Meeting Abstracts MA2022-02, no. 13 (October 9, 2022): 784. http://dx.doi.org/10.1149/ma2022-0213784mtgabs.
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Aluminum alloys are pickled and/or etched as a preliminary step prior to anodization or conversion coating. The chemistry of the etching/pickling process must be carefully engineered to avoid the enrichment of the alloying elements such metallic Cu which can interfere with subsequent treatments. Understanding and optimizing the etching process is therefore a major concern for the use of aluminum alloys, and especially, the Cu-rich high strength aluminum alloys. The etching reaction is a mixed potential process similar to other forms of aqueous corrosion. However, the dynamic nature of the interface makes it difficult to apply conventional electrochemistry to determine the rates and mechanisms of the different reactions and therefore, to predict how the etching process will vary with electrolyte composition. Among the many complicating factors, we can cite the very high dissolution rate of the alloy coupled with the formation of gas and the release of intermetallic particles. The dissolution of alloying elements such as Cu and Mg – the reactions of interest – occur at rates several orders of magnitude below that of Al dissolution. For example, Cu dissolution makes a negligible contribution to either electron exchange or mass loss. Finally, the rapid reaction rates and the short time scale of the process preclude the appearance of a true steady state, necessary for the interpretation of many electrochemical techniques. Therefore, to gain insight into the mechanism of the acid etching process, we have used an element-resolved electrochemical technique, atomic emission spectroelectrochemistry (AESEC) (Gharbi et al., 2016; Gharbi et al., 2017; Sultan et al., 2022). This permits the direct measurement of the elemental dissolution rates as a function of time, on an element-by-element basis. In this work, we illustrate the element-resolved electrochemical approach to surface treatment focusing on the acid etching of three alloys: a commercial high-strength AA7449 alloy (containing Zn, Cu, and Mg), and binary Al-Cu and Al-Mg alloys to represent the extremes of alloying element nobility. In sulfuric acid, the binary alloys also represent the extremes of selective versus congruent dissolution. The Al-Mg binary alloy undergoes a simultaneous, congruent dissolution mechanism with Mg dissolving simultaneously with Al. By contrast, the Al-Cu binary alloy exhibits a selective dissolution mechanism with Al dissolving to leave behind dealloyed metallic Cu on the surface of the material. This is ultimately followed by the release of Cu-rich particles due to anodic undermining. The electrolytes investigate in this work represent a range of oxidizing strengths from pure sulfuric acid to pure nitric acid and various mixtures of the two. The effect of Fe(III), an important component of many state-of-the-art etching solutions, was also investigated. Experimental elemental Evans diagrams were determined to clarify the electrochemical nature of the dissolution reactions, specifically how the elemental dissolution rates were related to one another and how they were coupled to the cathodic reactions. An example is shown in the Figure (right), based on the 2022 publication of Sultan et al. On the left, we show a cartoon representation of the dissolution process as determined for a high strength AA7449 alloy. On the right, we show the experimental element-resolved Evans diagram for the same alloy in sulfuric acid. It was found that Cu would not dissolve at the open circuit potential in sulfuric acid, but displayed active dissolution with a well-defined Tafel slope of 44 mV/decade at higher potential. The dissolution rate of Cu in the etching solutions was controlled by the redox potential of the electrolyte as determined by the addition of nitric acid and/or Fe(III). Based on our results, the Fe(III) additive in the presence of nitrate appears to serve a catalytic role, enhancing the rate of electron transfer between Cu and nitrate. The dissolution of Al and Mg were independent of potential suggesting simultaneous dissolution across an oxide film. The rates and mechanisms of Cu particle release will also be discussed. BBM Sultan, D Thierry, JM Torrescano-Alvarez, K Ogle, “Selective dissolution during acid pickling of aluminum alloys by element-resolved electrochemistry”, Electrochim. Acta, 404(2022)139737. O Gharbi, N Birbilis, K Ogle, “In-situ monitoring of alloy dissolution and residual film formation during the pretreatment of Al-alloy AA2024-T3”, J. Electrochem. Soc. 163 (2016)C240. O Gharbi, N Birbilis, K Ogle, “Li reactivity during the surface pretreatment of Al-Li alloy AA2050-T3”, Electrochim. Acta 243(2017)207-219. Figure 1
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Liang, Feng, Bitao Lai, Jilin Zhang, Hui-Hai Liu, and Weichang Li. "An Experimental Study on Interactions Between Imbibed Fracturing Fluid and Organic-Rich Tight Carbonate Source Rocks." SPE Journal 23, no. 06 (August 23, 2018): 2133–46. http://dx.doi.org/10.2118/188338-pa.
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Summary Carbonate reservoirs dominate oil (70%) and gas (90%) reserves in the Middle East, and imbibition is the main mechanism for fracturing-fluid uptake during the hydraulic-fracturing stimulation process. Because of the highly heterogeneous nature of tight carbonate source rocks, it is crucial to understand the effects of imbibed fluid on the mechanical, morphological, and flow properties of carbonate rocks. Although the influence of imbibed fluids on the wettability of carbonate reservoir has been studied extensively, research regarding the effects of imbibed fluids on the texture and mineralogy of carbonate rocks is still very limited. This paper aims to provide a conceptual approach and work flow to characterize and quantify microstructure and mineralogy changes in carbonate rocks caused by imbibed fluids. A thin section of a low-permeability organic-rich carbonate-rock sample [7×7×0.3 mm (length×width×thickness)] was used in the study. The sample was submerged into 2%-KCl (pH = 7.1) fluid from one end to simulate the spontaneous-imbibition process. A scanning electron microscope (SEM) was used to capture the sample's morphological changes before and after spontaneous imbibition. Energy-dispersive-spectroscopy (EDS) maps were measured before and after fluid treatment to investigate changes in various elemental distribution. In addition, inductively coupled plasma (ICP) equipped with an optical-emission-spectrometer (OES) detector was used to quantify dissolved-ion concentration in the treatment fluid. Permeability and porosity were measured using core plugs with dimensions of 1.0×1.5 in. (diameter×length) before and after fluid treatment. During the imbibition process, approximately one-half of the sample was submerged in the treatment fluid. The SEM images for the thin-section sample showed three zones with distinct fluid-uptake characteristics. In Zone I, which was fully submerged in the testing fluid, a significant amount of mineral dissolution was observed. In Zone III, which was above the testing-fluid level, considerable mineral precipitation was detected. While in the transition zone just above the water/air interface (Zone II between the previous two zones), only a minor level of mineral dissolution was observed. Elemental-distribution changes resulting from the fluid treatment were identified by EDS analysis in all three zones. Gypsum and calcite crystals dissolved into imbibed fluids upon reaction. Gypsum was found reprecipitated on the rock surface in the zones above fluid level. The observed gypsum formation likely resulted from the dissolution of the gypsum from the rock matrix, then reprecipitation later from the imbibition experiment caused by water evaporation. Absolute-permeability and porosity measurements for core-plug samples have shown that both were increased after the imbibition process.
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Schipper, C. Ian, William D. A. Rickard, Steven M. Reddy, David W. Saxey, Jonathan M. Castro, Denis Fougerouse, Zakaria Quadir, Chris Conway, David J. Prior, and Kat Lilly. "Volcanic SiO2-cristobalite: A natural product of chemical vapor deposition." American Mineralogist 105, no. 4 (April 1, 2020): 510–24. http://dx.doi.org/10.2138/am-2020-7236.
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Abstract Cristobalite is a low-pressure, high-temperature SiO2 polymorph that occurs as a metastable phase in many geologic settings, including as crystals deposited from vapor within the pores of volcanic rocks. Such vapor-phase cristobalite (VPC) has been inferred to result from silica redistribution by acidic volcanic gases but a precise mechanism for its formation has not been established. We address this by investigating the composition and structure of VPC deposited on plagioclase substrates within a rhyolite lava flow, at the micrometer to nanometer scale. The VPC contains impurities of the form [AlO4/Na+]0—coupled substitution of Al3+ charge-balanced by interstitial Na+—which are typical of cristobalite. However, new electron probe microanalysis (EPMA) element maps show individual crystals to have impurity concentrations that systematically decline from crystal cores-to-rims, and atom probe tomography reveals localized segregation of impurities to dislocations. Impurity concentrations are inversely correlated with degrees of crystallinity [observed by electron backscatter diffraction (EBSD), hyperspectral cathodoluminescence, laser Raman, and transmission electron microscopy (TEM)], such that crystal cores are poorly crystalline and rims are highly ordered tetragonal α-cristobalite. The VPC-plagioclase interfaces show evidence that dissolution-reprecipitation reactions between acidic gases and plagioclase crystals yield precursory amorphous SiO2 coatings that are suitable substrates for initial deposition of impure cristobalite. Successive layers of cubic β-cristobalite are deposited with impurity concentrations that decline as Al-bearing gases rapidly become unstable in the vapor cooling within pores. Final cooling to ambient temperature causes a displacive transformation from β→α cristobalite, but with locally expanded unit cells where impurities are abundant. We interpret this mechanism of VPC deposition to be a natural proxy for dopant-modulated Chemical Vapor Deposition, where halogen-rich acidic gases uptake silica, react with plagioclase surfaces to form suitable substrates and then deposit SiO2 as impure cristobalite. Our results have implications for volcanic hazards, as it has been established that the toxicity of crystalline silica is positively correlated with its purity. Furthermore, we note that VPC commonly goes unreported, but has been observed in silicic lavas of virtually all compositions and eruptive settings. We therefore suggest that despite being metastable at Earth's surface, cristobalite may be the most widely occurring SiO2 polymorph in extrusive volcanic rocks and a useful indicator of gas-solid reaction having occurred in cooling magma bodies.
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Hentschel, Felix, Emilie Janots, Claudia A. Trepmann, Valerie Magnin, and Pierre Lanari. "Corona formation around monazite and xenotime during greenschist-facies metamorphism and deformation." European Journal of Mineralogy 32, no. 5 (October 15, 2020): 521–44. http://dx.doi.org/10.5194/ejm-32-521-2020.
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Abstract. Epidote/allanite–fluorapatite coronae around monazite and xenotime are investigated in Permian pegmatites deformed under greenschist-facies conditions during Alpine tectonometamorphism in the Austroalpine basement, Eastern Alps. The aim was to evaluate the replacement reactions involved in the formation of a corona microstructure, its age and relation to deformation. In the corona core, monazite and xenotime single crystals show domains with different composition and age. Monazite (Mnz1) and xenotime (Xen1) dating by electron microprobe (EPM) reveals an age of 250–287 Ma, consistent with the Permian magmatic age of the pegmatites. These are partly replaced by secondary monazite (Mnz2) and xenotime (Xen2) compositions yielding younger Mesozoic (170–210 Ma) and Alpine (30–120 Ma) ages. The same crystallographic orientation of the primary and secondary monazite and xenotime indicates interface-coupled dissolution–precipitation reactions. Allanite U–Th–Pb dating by laser ablation inductively coupled mass spectrometry in the corona revealed an age of 60±6 Ma, interpreted as the age of corona formation. The coronae around monazite consist of an inner zone of equant fluorapatite grains surrounded by prismatic allanite, which are surrounded by epidote enriched in heavy rare earth elements (HREEs) and REE-poor epidote grains. Compared to coronae around monazite, fluorapatite has higher REE contents and no allanite occurs in the coronae surrounding the xenotime. General reactions for monazite and xenotime breakdown can be written as follows: Mnz1+(Si,Ca,Al,Fe,F)fluid→Mnz2+LREE-Ap+Aln+HREE-Ep+Ep+(Th,U)O2+(Th,U)SiO4,Xen1+(Si,Ca,Al,Fe,F)fluid→Xen2+HREE-Ap+HREE-Ep+Ep+(Th,U)O2. The amount of replacement (judged by the relative proportions of monazite and fluorapatite) is low for monazite included in tourmaline but high within the mylonitic foliation. This dependence on the degree of replacement on the local surrounding microfabric indicates that fluid availability along grain boundaries in the matrix and cracks controlled reaction advancement, allowing the elementary mass transfer required for corona formation (e.g. input of Ca, Al, Si, Fe, F). The oblate shape of the coronae aligned within the foliation of the pegmatites and the deflected foliation around the coronae, without an outer rim of prismatic epidote showing signs of deformation, indicate that the main stage of corona formation took place during deformation and reactions were still ongoing after the main stage of deformation. The corona microstructure documents replacement reactions of a single reactant into multiple distinct mineral growth zones by dissolution and precipitation processes at non-isostatic, greenschist-facies conditions, which prevailed in the area to the north of the Defereggen–Antholz–Vals shear zone between the middle Cretaceous and the Oligocene. These reactions ceased before being completed, and REE gradients within single grains within the corona and on the thin-section scale are preserved, which suggests restricted and/or episodic transport of REE in the fluid phase and/or availability of fluid.
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Bosbach, Dirk, Horst Geckeis, Frank Heberling, Olaf Kolditz, Michael Kühn, Katharina Müller, and Thorsten Stumpf. "An interdisciplinary view of the long-term evolution of repository systems across scales: the iCROSS project." Safety of Nuclear Waste Disposal 1 (November 10, 2021): 85–87. http://dx.doi.org/10.5194/sand-1-85-2021.
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Abstract. The interdisciplinary project “Integrity of nuclear waste repository systems – Cross-scale system understanding and analysis (iCROSS)” combines research competencies of Helmholtz scientists related to the topics of nuclear, geosciences, biosciences and environmental simulations in collaborations overarching the research fields energy and earth and environment. The focus is to understand and analyze close-to-real long-term evolutionary pathways of radioactive waste repositories across nanoscales to repository scales. The project is subdivided into work packages dealing with laboratory studies, field experiments in underground research laboratories (URLs), advanced modelling studies and the integration and alignment of data and information using virtual reality methods. In this sense, the project structure aims at a holistic view on relevant processes across scales in order to comprehensively simulate potential repository evolutions. Within the multi-barrier system of a repository for heat-generating radioactive waste, a number of complex reactions proceed, including dissolution, redox processes, biochemical reactions, gas evolution and solid/liquid interface and (co)precipitation reactions. At the same time, thermal and external mechanical stress has an impact on the conditions in a deep geological repository. All those processes are highly coupled, with multiple interdependencies on various scales and have a strong impact on radionuclide mobility and retention. In recent years, substantial progress was achieved in describing coupled thermal-hydro-mechanical-chemical-biological (THM/CB) processes in numerical simulations. A realistic and concise description of these coupled processes on different time and spatial scales is, at present, a largely unresolved scientific and computational challenge. The close interaction of experimental and simulation teams aims at a more accurate quantification and assessment of processes and thus, the reduction of uncertainties and of conservative assumptions and eventually to a close-to-real perception of the repository evolution. One focus of iCROSS is directed to relevant processes in a clay rock repository. In this context, the iCROSS team became a full member of the international Mont Terri consortium and worked in close collaboration with international and German institutions in URL projects. Respective experiments specifically deal with coupled processes at the reactive interfaces in a repository near field (e.g. the steel/bentonite and bentonite/concrete interfaces). Within iCROSS, the impact of secondary phase formation on radionuclide transport is investigated. At Mont Terri, experiments are in preparation to study radionuclide transport phenomena in clay rock formations within temperature gradients and in facies exhibiting significant heterogeneities on different scales (nm to cm). Beside those studies, high resolution exploration methods for rock characterization are developed and tested and the effect of temperature and other boundary conditions on the strength, creep properties and healing of faults within Opalinus clay are quantified. Multiphysics models coupled to reactive transport simulation have been further developed and applied to laboratory and field experiments. Results are digitally analyzed and illustrated in a visualization center, in order to enhance the comprehension of coupled processes in repository systems across scales. The present contribution provides an overview on the project and reports selected results. The impact of considering complex coupled processes in repository subsystems for the assessment of the integrity of a given (generic) repository arrangement is discussed.
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Lin, Che-Yu, Kun-Lin Lin, and Chien-Cheng Lin. "Reactions between Si melt and various ceramics." Processing and Application of Ceramics 13, no. 2 (2019): 115–23. http://dx.doi.org/10.2298/pac1902115l.
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Reactions between different kinds of ceramics and silicon were studied to evaluate ceramics as candidates for their use in the process of silicon-crystal growth. Three types of ceramic plates, Al2O3, ZrO2 and quartz (SiO2), were put into contact with a silicon wafer via annealing at 1450 ?C for 30min under an Ar atmosphere. Defects appeared at the Si-ceramics interface. Among these, a crack and a dislocation pile up were found at the Si-SiO2 dissolution couple. In addition, two intermetallic compounds, Y2Si2O7 and Zr-Si, produced by the diffusion of Y, O and Zr from the ZrO2 into the Si, were found at the Si-ZrO2 dissolution couple. At the interface of the Si-Al2O3 dissolution couple, no intermetallic compounds and few defects were found. The oxygen concentration and electrical resistivity near the interface were high and gradually decreased away from the interface for all Si-ceramics dissolution couples.
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Hülse, Dominik, Sandra Arndt, Stuart Daines, Pierre Regnier, and Andy Ridgwell. "OMEN-SED 1.0: a novel, numerically efficient organic matter sediment diagenesis module for coupling to Earth system models." Geoscientific Model Development 11, no. 7 (July 9, 2018): 2649–89. http://dx.doi.org/10.5194/gmd-11-2649-2018.
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Abstract. We present the first version of OMEN-SED (Organic Matter ENabled SEDiment model), a new, one-dimensional analytical early diagenetic model resolving organic matter cycling and the associated biogeochemical dynamics in marine sediments designed to be coupled to Earth system models. OMEN-SED explicitly describes organic matter (OM) cycling and the associated dynamics of the most important terminal electron acceptors (i.e. O2 , NO3, SO4) and methane (CH4), related reduced substances (NH4, H2S), macronutrients (PO4) and associated pore water quantities (ALK, DIC). Its reaction network accounts for the most important primary and secondary redox reactions, equilibrium reactions, mineral dissolution and precipitation, as well as adsorption and desorption processes associated with OM dynamics that affect the dissolved and solid species explicitly resolved in the model. To represent a redox-dependent sedimentary P cycle we also include a representation of the formation and burial of Fe-bound P and authigenic Ca–P minerals. Thus, OMEN-SED is able to capture the main features of diagenetic dynamics in marine sediments and therefore offers similar predictive abilities as a complex, numerical diagenetic model. Yet, its computational efficiency allows for its coupling to global Earth system models and therefore the investigation of coupled global biogeochemical dynamics over a wide range of climate-relevant timescales. This paper provides a detailed description of the new sediment model, an extensive sensitivity analysis and an evaluation of OMEN-SED's performance through comprehensive comparisons with observations and results from a more complex numerical model. We find that solid-phase and dissolved pore water profiles for different ocean depths are reproduced with good accuracy and simulated terminal electron acceptor fluxes fall well within the range of globally observed fluxes. Finally, we illustrate its application in an Earth system model framework by coupling OMEN-SED to the Earth system model cGENIE and tune the OM degradation rate constants to optimise the fit of simulated benthic OM contents to global observations. We find that the simulated sediment characteristics of the coupled model framework, such as OM degradation rates, oxygen penetration depths and sediment–water interface fluxes, are generally in good agreement with observations and in line with what one would expect on a global scale. Coupled to an Earth system model, OMEN-SED is thus a powerful tool that will not only help elucidate the role of benthic–pelagic exchange processes in the evolution and the termination of a wide range of climate events, but will also allow for a direct comparison of model output with the sedimentary record – the most important climate archive on Earth.
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Casella, Laura A., Erika Griesshaber, Xiaofei Yin, Andreas Ziegler, Vasileios Mavromatis, Dirk Müller, Ann-Christine Ritter, et al. "Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment." Biogeosciences 14, no. 6 (March 24, 2017): 1461–92. http://dx.doi.org/10.5194/bg-14-1461-2017.
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Abstract. Biomineralised hard parts form the most important physical fossil record of past environmental conditions. However, living organisms are not in thermodynamic equilibrium with their environment and create local chemical compartments within their bodies where physiologic processes such as biomineralisation take place. In generating their mineralised hard parts, most marine invertebrates produce metastable aragonite rather than the stable polymorph of CaCO3, calcite. After death of the organism the physiological conditions, which were present during biomineralisation, are not sustained any further and the system moves toward inorganic equilibrium with the surrounding inorganic geological system. Thus, during diagenesis the original biogenic structure of aragonitic tissue disappears and is replaced by inorganic structural features. In order to understand the diagenetic replacement of biogenic aragonite to non-biogenic calcite, we subjected Arctica islandica mollusc shells to hydrothermal alteration experiments. Experimental conditions were between 100 and 175 °C, with the main focus on 100 and 175 °C, reaction durations between 1 and 84 days, and alteration fluids simulating meteoric and burial waters, respectively. Detailed microstructural and geochemical data were collected for samples altered at 100 °C (and at 0.1 MPa pressure) for 28 days and for samples altered at 175 °C (and at 0.9 MPa pressure) for 7 and 84 days. During hydrothermal alteration at 100 °C for 28 days most but not the entire biopolymer matrix was destroyed, while shell aragonite and its characteristic microstructure was largely preserved. In all experiments up to 174 °C, there are no signs of a replacement reaction of shell aragonite to calcite in X-ray diffraction bulk analysis. At 175 °C the replacement reaction started after a dormant time of 4 days, and the original shell microstructure was almost completely overprinted by the aragonite to calcite replacement reaction after 10 days. Newly formed calcite nucleated at locations which were in contact with the fluid, at the shell surface, in the open pore system, and along growth lines. In the experiments with fluids simulating meteoric water, calcite crystals reached sizes up to 200 µm, while in the experiments with Mg-containing fluids the calcite crystals reached sizes up to 1 mm after 7 days of alteration. Aragonite is metastable at all applied conditions. Only a small bulk thermodynamic driving force exists for the transition to calcite. We attribute the sluggish replacement reaction to the inhibition of calcite nucleation in the temperature window from ca. 50 to ca. 170 °C or, additionally, to the presence of magnesium. Correspondingly, in Mg2+-bearing solutions the newly formed calcite crystals are larger than in Mg2+-free solutions. Overall, the aragonite–calcite transition occurs via an interface-coupled dissolution–reprecipitation mechanism, which preserves morphologies down to the sub-micrometre scale and induces porosity in the newly formed phase. The absence of aragonite replacement by calcite at temperatures lower than 175 °C contributes to explaining why aragonitic or bimineralic shells and skeletons have a good potential of preservation and a complete fossil record.
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Altree-Williams, Alexander, Allan Pring, Yung Ngothai, and Joël Brugger. "Textural and compositional complexities resulting from coupled dissolution–reprecipitation reactions in geomaterials." Earth-Science Reviews 150 (November 2015): 628–51. http://dx.doi.org/10.1016/j.earscirev.2015.08.013.
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Xia, Fang, Jinwen Zhou, Joël Brugger, Yung Ngothai, Brian O’Neill, Guorong Chen, and Allan Pring. "Novel Route To Synthesize Complex Metal Sulfides: Hydrothermal Coupled Dissolution−Reprecipitation Replacement Reactions." Chemistry of Materials 20, no. 8 (April 2008): 2809–17. http://dx.doi.org/10.1021/cm7033883.
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Zhou, Haoyang, Richard Wirth, Sarah A. Gleeson, Anja Schreiber, and Sathish Mayanna. "Three-Dimensional and Microstructural Fingerprinting of Gold Nanoparticles at Fluid-Mineral Interfaces." American Mineralogist 106, no. 1 (January 1, 2021): 97–104. http://dx.doi.org/10.2138/am-2021-7696.
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Abstract Recent studies have identified gold nanoparticles in ores in a range of deposit types, but little is known about their formation processes. In this contribution, gold-bearing magnetite from the well-documented, world-class Beiya Au deposit, China, was investigated in terms of microstructure and crystallography at the nanoscale. We present the first three-dimensional (3D) focused ion beam/scanning electron microscopy (FIB/SEM) tomography of the distribution of gold nanoparticles in nanopores in the low-Si magnetite. The porous low-Si magnetite, which overprints an earlier generation of silician magnetite, was formed by a coupled dissolution-reprecipitation reaction (CDRR). The extrinsic changes in thermodynamic conditions (e.g., S content and temperature) of the hydrothermal fluids resulted in the CDRR in magnetite and the disequilibrium of Au-Bi melts. The gold nanoparticles crystallized from Au-supersaturated fluids originating from the disequilibrium of Au-Bi melts and grew in two ways depending on the intrinsic crystal structure and pore textures: (1) heteroepitaxial growth utilizing the (111) lattice planes of magnetite, and (2) randomly oriented nucleation and growth. Therefore, this study unravels how intrinsic and extrinsic factors drove the formation of gold nanoparticles at fluid-mineral interfaces.
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Putnis, A. "Mineral replacement reactions: from macroscopic observations to microscopic mechanisms." Mineralogical Magazine 66, no. 5 (October 2002): 689–708. http://dx.doi.org/10.1180/0026461026650056.
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AbstractMineral replacement reactions take place primarily by dissolution-reprecipitation processes. Processes such as cation exchange, chemical weathering, deuteric alteration, leaching, pseudomorphism, metasomatism, diagenesis and metamorphism are all linked by common features in which one mineral or mineral assemblage is replaced by a more stable assemblage. The aim of this paper is to review some of these aspects of mineral replacement and to demonstrate the textural features they have in common, in order to emphasize the similarities in the underlying microscopic mechanisms. The role of volume change and evolution of porosity is explored both from natural microtextures and new experiments on model replacement reactions in simple salts. It is shown that the development of porosity is often a consequence of mineral replacement processes, irrespective of the relative molar volumes of parent and product solid phases. The key issue is the relative solubility of the phases in the fluid phase. Concepts such as coupled dissolution-precipitation, and autocatalysis are important in understanding these processes. Some consequences of porosity generation for metamorphic fluid flow as well as subsequent crystal growth are also discussed.
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Ague, Jay J., and Jennifer A. Axler. "Interface coupled dissolution-reprecipitation in garnet from subducted granulites and ultrahigh-pressure rocks revealed by phosphorous, sodium, and titanium zonation." American Mineralogist 101, no. 7 (July 2016): 1696–99. http://dx.doi.org/10.2138/am-2016-5707.
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Perdikouri, C., A. Kasioptas, C. V. Putnis, and A. Putnis. "The effect of fluid composition on the mechanism of the aragonite to calcite transition." Mineralogical Magazine 72, no. 1 (February 2008): 111–14. http://dx.doi.org/10.1180/minmag.2008.072.1.111.
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AbstractExperiments were performed to investigate the transformation of natural aragonite crystals to calcite by reaction with aqueous solutions of calcium carbonate at hydrothermal conditions for different periods of time. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and Laser ablation inductively coupled mass spectrometry (LA-ICP-MS) were used to characterize the reaction product. The results indicate that the replacement of aragonite by calcite follows an interface-coupled dissolution-precipitation mechanism.
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Brugger, Joël, Aoife McFadden, Claire E. Lenehan, Barbara Etschmann, Fang Xia, Jing Zhao, and Allan Pring. "A Novel Route for the Synthesis of Mesoporous and Low-Thermal Stability Materials by Coupled Dissolution-Reprecipitation Reactions: Mimicking Hydrothermal Mineral Formation." CHIMIA International Journal for Chemistry 64, no. 10 (October 29, 2010): 693–98. http://dx.doi.org/10.2533/chimia.2010.693.
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Chong, Eugene, Jae Sam Jeon, Woo Kyung Sung, and Hyung Sun Kim. "Interface Reaction between Fillers and Phosphate Glass for Barrier Ribs in Plasma Display Panel." Solid State Phenomena 124-126 (June 2007): 415–18. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.415.
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The present study is mainly focused on the evaluation of interface reaction between ceramic fillers and phosphate glass matrix for barrier ribs in PDP. The samples were prepared by dry milling for frits with a mean particle size(d50) of 1-2㎛. The frit was mixed with ceramic fillers (Al2O3, ZnO) and was fired at 550°C for 30 minutes. Interface reaction was observed by measuring the weight change of fired samples as a function of immersion time in 90°C de-ionized water and in 60°C acid solution. Fired samples were characterized by differential thermal analyzer, scanning electron microscopy, X-ray diffraction and ion dissolution was analyzed by inductive coupled plasma measurement. The results suggest that properties of barrier rib depend on the crystallization behavior and interface reaction between the fillers and the glass matrix.
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Xia, Qing, Jiajun Liu, Yongsheng Li, Jeffrey de Fourestier, Dazhao Wang, Degao Zhai, Xiaofei Yu, Xin Lü, and Xuefeng Li. "Mineral paragenesis of the Anfangba gold deposit, western Qinling Orogen, China: Implication for coupled dissolution-reprecipitation reactions and the liquid bismuth collector model." Ore Geology Reviews 139 (December 2021): 104502. http://dx.doi.org/10.1016/j.oregeorev.2021.104502.
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Lyubimtseva, N. G., N. S. Bortnikov, S. E. Borisovsky, O. V. Vikent’eva, and V. Yu Prokofiev. "Pseudomorphic Rhythmically Banded and Oscillatory Tetrahedrite–Tennantite Aggregates in the Darasun Gold Deposit (Eastern Transbaikalia, Russia): A Result of Coupled Dissolution–Reprecipitation Reactions." Doklady Earth Sciences 483, no. 1 (December 2018): 1431–36. http://dx.doi.org/10.1134/s1028334x18110041.
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Passerone, Alberto, Fabrizio Valenza, and Maria Luigia Muolo. "High Temperature Solid-Liquid Interactions in Metal-Ceramic Brazing: A Critical Review." Materials Science Forum 884 (January 2017): 132–65. http://dx.doi.org/10.4028/www.scientific.net/msf.884.132.
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Solid-liquid interactions in metal-ceramic systems are extremely important in high temperature brazing processes. These interfacial phenomena are reviewed here, from both the thermodynamic and microstructural viewpoints. At high temperature, the wetting characteristics and the adhesion properties of the joints are strongly related to the high atomic mobility of the different phases, giving rise to different phenomena, ranging from the dissolution of the ceramic in the liquid phase, reactions, formation of new phases and reprecipitation at the solid-liquid interface. The role phase diagrams in guiding the choice of the filler alloys composition and to optimize the brazing procedures is emphasized. In particular, it is shown that the computation of new diagrams and the critical use of the existing ones is essential to understand how to suppress the substrate dissolution and to interpret the evolution of the system. Experimental data are presented and discussed concerning the interactions between liquid metals with early-transition-metal diborides (TiB2, ZrB2, HfB2) as a typical example involving the joining of Ultra-High Temperature Ceramics (UHTCs). Overall, these studies represent the basic step linking the chemical and structural information to the design of industrial processes involving a liquid phase at high temperature, such as the production of metal-ceramic joints or composite materials to be used in highly demanding applications.
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McElhinney, Tara R., Tim J. Dempster, and Peter Chung. "The influence of microscale lithological layering and fluid availability on the metamorphic development of garnet and zircon: insights into dissolution–reprecipitation processes." Mineralogical Magazine 86, no. 1 (December 13, 2021): 9–26. http://dx.doi.org/10.1180/mgm.2021.97.
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AbstractThe response of garnet and zircon to prograde amphibolite-facies metamorphism in late Proterozoic mica schists from the Scottish Highlands has been investigated. Spatial analysis of zircon populations using scanning electron microscopy was undertaken in Dalradian Schists that have undergone a sequence of prograde garnet growth and localised breakdown reactions involving coupled dissolution–reprecipitation. Fluid availability and matrix permeability strongly control this metamorphic response and different generations of garnet contain radically different populations of metamorphic micro-zircon and associated changes in the detrital zircon population. Micro-zircon abundance increases during garnet growth, whereas that of detrital zircon decreases. The mineralogy of the matrix influences zircon abundance in porphyroblast phases, where garnet overgrows a micaceous matrix zircon-rich garnet forms and where it overgrows a quartzofeldspathic matrix the result is zircon-poor garnet. Following garnet growth, micro-zircon abundance decreases at each stage of the prograde reaction history, with sillimanite-zone schists containing the lowest abundance, suggesting micro-zircons are texturally less stable at staurolite- and sillimanite-grade metamorphism. Micro-zircons are distributed evenly across host minerals in the matrix, with the exception of retrograde chlorite where micro-zircons are absent due to fluids removing Zr before new zircon can precipitate. There is an overall decrease in the mode of zircon at each stage of the reaction history, indicating that zircon is a highly reactive phase during amphibolite-facies metamorphism and is very sensitive to individual prograde and retrograde reactions.
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Brugger, Joel, Aoife McFadden, Claire E. Lenehan, Barbara Etschmann, Fang Xia, Jing Zhao, and Allan Pring. "ChemInform Abstract: A Novel Route for the Synthesis of Mesoporous and Low-Thermal Stability Materials by Coupled Dissolution-Reprecipitation Reactions. Mimicking Hydrothermal Mineral Formation." ChemInform 42, no. 19 (April 14, 2011): no. http://dx.doi.org/10.1002/chin.201119213.
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Di Lorenzo, Fulvio, Cristina Ruiz-Agudo, Aurelia Ibañez-Velasco, Rodrigo Gil-San Millán, Jorge Navarro, Encarnacion Ruiz-Agudo, and Carlos Rodriguez-Navarro. "The Carbonation of Wollastonite: A Model Reaction to Test Natural and Biomimetic Catalysts for Enhanced CO2 Sequestration." Minerals 8, no. 5 (May 11, 2018): 209. http://dx.doi.org/10.3390/min8050209.
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One of the most promising strategies for the safe and permanent disposal of anthropogenic CO2 is its conversion into carbonate minerals via the carbonation of calcium and magnesium silicates. However, the mechanism of such a reaction is not well constrained, and its slow kinetics is a handicap for the implementation of silicate mineral carbonation as an effective method for CO2 capture and storage (CCS). Here, we studied the different steps of wollastonite (CaSiO3) carbonation (silicate dissolution → carbonate precipitation) as a model CCS system for the screening of natural and biomimetic catalysts for this reaction. Tested catalysts included carbonic anhydrase (CA), a natural enzyme that catalyzes the reversible hydration of CO2(aq), and biomimetic metal-organic frameworks (MOFs). Our results show that dissolution is the rate-limiting step for wollastonite carbonation. The overall reaction progresses anisotropically along different [hkl] directions via a pseudomorphic interface-coupled dissolution–precipitation mechanism, leading to partial passivation via secondary surface precipitation of amorphous silica and calcite, which in both cases is anisotropic (i.e., (hkl)-specific). CA accelerates the final carbonate precipitation step but hinders the overall carbonation of wollastonite. Remarkably, one of the tested Zr-based MOFs accelerates the dissolution of the silicate. The use of MOFs for enhanced silicate dissolution alone or in combination with other natural or biomimetic catalysts for accelerated carbonation could represent a potentially effective strategy for enhanced mineral CCS.
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Riba, O., E. Coene, O. Silva, and L. Duro. "Spent fuel alteration model integrating processes of different time-scales." MRS Advances 5, no. 3-4 (2020): 159–66. http://dx.doi.org/10.1557/adv.2020.51.
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ABSTRACTA 1D reactive transport model has been implemented in iCP (interface COMSOL Multiphysics and PhreeqC) to assess the corrosion of Spent Fuel (SF), considered as homogeneous UO2(am,hyd) doped with Pd. The model couples: i) generation of water radiolysis species by alpha and beta radiation considering the complete water radiolysis system with the kinetic reactions involving: H+, OH-, O2, H2O2, H2, HO2-, HO2·, O·, O-, O2-, H·, ·OH and e- ii) processes occurring in the spent fuel surface: oxidative dissolution reactions of UO2(am,hyd) and subsequent reduction of oxidized fuel, considering H2 activation by Pd, and iii) corrosion of Fe(s) in oxic and anoxic conditions. Process i) has been implemented in COMSOL and processes ii) and iii) have been implemented in PHREEQC with their kinetic constants being calibrated with different sets of experimental data published in the open literature. The model yields a UO2(am,hyd) dissolution rates similar to the values selected in safety assessments.
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Lyubimtseva, N., N. Bortnikov, S. Borisovskiy, S. Vikent’eva, and V. Prokofiev. "Pseudomorphous Rhythmic-Banded and Oscillatory Aggregates of Tetrahedrite-Tennantite at the Gold Deposit Darasun (Eastern Transbaikalia, Russia): a Result of the Coupled Dissolution-Reprecipitation Replacement Reactions." Доклады академии наук 483, no. 1 (November 2018): 89–93. http://dx.doi.org/10.31857/s086956520003418-2.
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Li, Nan, Jun Deng, David Groves, and Ri Han. "Controls on the Distribution of Invisible and Visible Gold in the Orogenic Gold Deposits of the Yangshan Gold Belt, West Qinling Orogen, China." Minerals 9, no. 2 (February 4, 2019): 92. http://dx.doi.org/10.3390/min9020092.
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Six orogenic gold deposits constitute the Yangshan gold belt in the West Qinling Orogen. Gold is mostly invisible in solid solution or in the sulfide lattice, with minor visible gold associated with stibnite and in quartz-calcite veins. Detailed textural and trace-element analysis of sulfides in terms of a newly-erected paragenetic sequence for these deposits, together with previously published data, demonstrate that early magmatic-hydrothermal pyrite in granitic dike host-rocks has much higher Au contents than diagenetic pyrite in metasedimentary host rocks, but lower contents of As, Au, and Cu than ore-stage pyrite. Combined with sulfur isotope data, replacement textures in the gold ores indicate that the auriferous ore-fluids post-dated the granitic dikes and were not magmatic-hydrothermal in origin. There is a strong correlation between the relative activities of S and As and their total abundances in the ore fluid and the siting of gold in the Yangshan gold ores. Mass balance calculations indicate that there is no necessity to invoke remobilization processes to explain the occurrence of gold in the ores. The only exception is the Py1-2 replacement of Py1m, where fluid-mediated coupled dissolution-reprecipitation reactions may have occurred to exchange Au between the two pyrite phases.
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Alihussein, Hussein, Martin Geier, and Manfred Krafczyk. "A Parallel Coupled Lattice Boltzmann-Volume of Fluid Framework for Modeling Porous Media Evolution." Materials 14, no. 10 (May 12, 2021): 2510. http://dx.doi.org/10.3390/ma14102510.
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In this paper, we present a framework for the modeling and simulation of a subset of physical/chemical processes occurring on different spatial and temporal scales in porous materials. In order to improve our understanding of such processes on multiple spatio-temporal scales, small-scale simulations of transport and reaction are of vital importance. Due to the geometric complexity of the pore space and the need to consider a representative elementary volume, such simulations require substantial numerical resolutions, leading to potentially huge computation times. An efficient parallelization of such numerical methods is thus vital to obtain results in acceptable wall-clock time. The goal of this paper was to improve available approaches based on lattice Boltzmann methods (LBMs) to reliably and accurately predict the combined effects of mass transport and reaction in porous media. To this end, we relied on the factorized central moment LBM as a second-order accurate approach for modeling transport. In order to include morphological changes due to the dissolution of the solid phase, the volume of fluid method with the piece-wise linear interface construction algorithm was employed. These developments are being integrated into the LBM research code VirtualFluids. After the validation of the analytic test cases, we present an application of diffusion-controlled dissolution for a pore space obtained from computer tomography (CT) scans.
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Wang, Mengmeng, Jiang Ju, Jingjing Li, Yang Zhou, Haiyang Lv, Haiyan Gao, and Jun Wang. "The Formation Mechanism of a Self-Organized Periodic-Layered Structure at the Solid-(Cr, Fe)2B/Liquid-Al Interface." Materials 13, no. 17 (September 2, 2020): 3869. http://dx.doi.org/10.3390/ma13173869.
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A periodic-layered structure was observed in solid-(Cr, Fe)2B/liquid-Al diffusion couple at 750 °C. The interface morphology, the reaction products, and the potential formation mechanism of this periodic-layered structure were investigated using an electron probe microanalyzer (EPMA), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS). The results indicate that the reaction between (Cr, Fe)2B and liquid Al is a diffusion-controlled process. The formation of intermetallics involves both the superficial dissolution of Fe and Cr atoms and the inward diffusion of Al at the interface. The layered structure, as characterized by various experimental techniques, is alternated by a single FeAl3 layer and a (FeAl3 + Cr3AlB4) dual-phase layer. A potential mechanism describing the formation process of this periodic-layered structure was proposed based on the diffusion kinetics based on the experimental results.
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Fisher, Donald M., John N. Hooker, Andrew J. Smye, and Tsai-Wei Chen. "Insights from the geological record of deformation along the subduction interface at depths of seismogenesis." Geosphere 17, no. 6 (November 4, 2021): 1686–703. http://dx.doi.org/10.1130/ges02389.1.
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Abstract Subduction interfaces are loci of interdependent seismic slip behavior, fluid flow, and mineral redistribution. Mineral redistribution leads to coupling between fluid flow and slip behavior through decreases in porosity/permeability and increases in cohesion during the interseismic period. We investigate this system from the perspective of ancient accretionary complexes with regional zones of mélange that record noncoaxial strain during underthrusting adjacent to the subduction interface. Deformation of weak mudstones is accompanied by low-grade metamorphic reactions, dissolution along scaly microfaults, and the removal of fluid-mobile chemical components, whereas stronger sandstone blocks preserve veins that contain chemical components depleted in mudstones. These observations support local diffusive mass transport from scaly fabrics to veins during interseismic viscous coupling. Underthrusting sediments record a crack porosity that fluctuates due to the interplay of cracking and precipitation. Permanent interseismic deformation involves pressure solution slip, strain hardening, and the development of new shears in undeformed material. In contrast, coseismic slip may be accommodated within observed narrow zones of cataclastic deformation at the top of many mélange terranes. A kinetic model implies interseismic changes in physical properties in less than hundreds of years, and a numerical model that couples an earthquake simulator with a fluid flow system depicts a subduction zone interface governed by feedbacks between fluid production, permeability, hydrofracturing, and aging via mineral precipitation. During an earthquake, interseismic permeability reduction is followed by coseismic rupture of low permeability seals and fluid pressure drop in the seismogenic zone. Updip of the seismogenic zone, there is a post-seismic wave of higher fluid pressure that propagates trenchward.
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Casella, Laura A., Sixin He, Erika Griesshaber, Lourdes Fernández-Díaz, Martina Greiner, Elizabeth M. Harper, Daniel J. Jackson, et al. "Hydrothermal alteration of aragonitic biocarbonates: assessment of micro- and nanostructural dissolution–reprecipitation and constraints of diagenetic overprint from quantitative statistical grain-area analysis." Biogeosciences 15, no. 24 (December 21, 2018): 7451–84. http://dx.doi.org/10.5194/bg-15-7451-2018.
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Abstract. The assessment of diagenetic overprint on microstructural and geochemical data gained from fossil archives is of fundamental importance for understanding palaeoenvironments. The correct reconstruction of past environmental dynamics is only possible when pristine skeletons are unequivocally distinguished from altered skeletal elements. Our previous studies show (i) that replacement of biogenic carbonate by inorganic calcite occurs via an interface-coupled dissolution–reprecipitation mechanism. (ii) A comprehensive understanding of alteration of the biogenic skeleton is only given when structural changes are assessed on both, the micrometre as well as on the nanometre scale.In the present contribution we investigate experimental hydrothermal alteration of six different modern biogenic carbonate materials to (i) assess their potential for withstanding diagenetic overprint and to (ii) find characteristics for the preservation of their microstructure in the fossil record. Experiments were performed at 175 °C with a 100 mM NaCl + 10 mM MgCl2 alteration solution and lasted for up to 35 days. For each type of microstructure we (i) examine the evolution of biogenic carbonate replacement by inorganic calcite, (ii) highlight different stages of inorganic carbonate formation, (iii) explore microstructural changes at different degrees of alteration, and (iv) perform a statistical evaluation of microstructural data to highlight changes in crystallite size between the pristine and the altered skeletons.We find that alteration from biogenic aragonite to inorganic calcite proceeds along pathways where the fluid enters the material. It is fastest in hard tissues with an existing primary porosity and a biopolymer fabric within the skeleton that consists of a network of fibrils. The slowest alteration kinetics occurs when biogenic nacreous aragonite is replaced by inorganic calcite, irrespective of the mode of assembly of nacre tablets. For all investigated biogenic carbonates we distinguish the following intermediate stages of alteration: (i) decomposition of biopolymers and the associated formation of secondary porosity, (ii) homoepitactic overgrowth with preservation of the original phase leading to amalgamation of neighbouring mineral units (i.e. recrystallization by grain growth eliminating grain boundaries), (iii) deletion of the original microstructure, however, at first, under retention of the original mineralogical phase, and (iv) replacement of both, the pristine microstructure and original phase with the newly formed abiogenic product.At the alteration front we find between newly formed calcite and reworked biogenic aragonite the formation of metastable Mg-rich carbonates with a calcite-type structure and compositions ranging from dolomitic to about 80 mol % magnesite. This high-Mg calcite seam shifts with the alteration front when the latter is displaced within the unaltered biogenic aragonite. For all investigated biocarbonate hard tissues we observe the destruction of the microstructure first, and, in a second step, the replacement of the original with the newly formed phase.
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Lee, Martin R., Kim A. Waldron, and Ian Parsons. "Exsolution and alteration microtextures in alkali feldspar phenocrysts from the Shap granite." Mineralogical Magazine 59, no. 394 (March 1995): 63–78. http://dx.doi.org/10.1180/minmag.1995.59.394.06.
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AbstractAlkali feldspar phenocrysts (bulk composition Or75.0Ab24.6An0.4) in the subsolvus Shap granite comprise a fine-scale mixture of subregular pristine crypto- and micro-perthites with altered, micropore-rich feldspar with irregular microstructures. The regular perthites are strain-controlled intergrowths of Albite and/or Periclinetwinned albite exsolution lamellae within tweed orthoclase. The microperthites formed at ⩽ 590°C by heterogeneous nucleation of thin albite films which coarsened to > 1 µm length. Cryptoperthites developed at < 400°C by homogeneous nucleation of sub-µm long platelets between films. Platelets are coherent, but the coarser microperthite lamellae are semi-coherent, with pairs of misfit dislocations sub-regularly spaced along the albite-orthoclase interface. As much as 30% of any one feldspar crystal is turbid, a result of the formation of numerous µm to sub-µm sized micropores during deuteric alteration. In some areas, deuteric fluids gained access to the interior of feldspar crystals by exploiting semi-coherent film lamellae. Albite was selectively dissolved and micropore-rich irregular microcline was reprecipitated in its place. In other parts of the feldspars deuteric recrystallization completely cross-cuts the pristine microtextures and patch perthites have formed. These are coarse, incoherent to semi-coherent intergrowths of irregular microcline (replacing tweed orthoclase) and Albite-twinned albite. The deuteric reactions occurred at < 400°C; the main driving force for dissolution and reprecipitation was decrease in the elastic strain energy at the coherent interfaces of crypto-and micro-perthite lamellae, and the recrystallization of tweed orthoclase to irregular microcline.
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Khaledialidusti, Rasoul, and Jon Kleppe. "Surface-Charge Alteration at the Carbonate/Brine Interface During Single-Well Chemical-Tracer Tests: Surface-Complexation Model." SPE Journal 23, no. 06 (August 17, 2018): 2302–15. http://dx.doi.org/10.2118/191356-pa.
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Summary Water chemistry has been shown to affect oil recovery by affecting surface charge and rock dissolution. The single-well chemical-tracer (SWCT) test is a field method to measure residual oil saturation (Sor), in which hydrolysis reaction of an ester has been known as a key process that could displace the equilibrium state of a reservoir by changing formation-water (FW) composition. Because oil mobilization during the SWCT tests causes an error in the measurement of Sor, changes in water chemistry might be a concern for the accuracy of Sor measurements. In our previous work, the extent to which different reservoir parameters might change water composition and the effect of water-chemistry changes on the calcite dissolution and the oil liberation from the carbonate-rock surfaces were extensively evaluated. In this study, the effect of water-chemistry changes on surface-charge alteration at the carbonate/brine interface has been studied by constructing and applying a surface-complexation model (SCM) that couples bulk aqueous and surface chemistry. We present how the pH drop induced by the displacement of the equilibrium state and changes in water chemistry in the formation affect surface charge in a pure-calcite carbonate rock during the SWCT tests. The results show that a pH drop during the SWCT tests while calcium concentration is held constant in the FW by ignoring calcite dissolution yields a less-positive/more-negative surface charge so that wettability of carbonate rock might be altered to a less-oil-wetting state, when the oil is negatively charged. In reality, however, calcite dissolves by water-chemistry changes during the SWCT tests, which leads to an increasing calcium concentration in the FW. Consequently, an SWCT test in carbonates is accompanied by increasing calcium concentration while pH drops, which yields an increase in the surface charge of carbonate rocks. Therefore, the pH drop does not directly affect the surface charge of carbonate rock during an SWCT test, and calcium concentration increased from calcite dissolution could control the surface charge more significantly.
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Lim, Hyung-Seok, Sujong Chae, Litao Yan, Guosheng Li, Ruozhu Feng, Yongsoon Shin, Zimin Nie, et al. "Crosslinked Polyethyleneimine Gel Polymer Interface to Improve Cycling Stability of RFBs." Energy Material Advances 2022 (January 5, 2022): 1–10. http://dx.doi.org/10.34133/2022/9863679.
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Redox flow batteries are considered a promising technology for grid energy storage. However, capacity decay caused by crossover of active materials is a universal challenge for many flow battery systems, which are based on various chemistries. In this paper, using the vanadium redox flow battery as an example, we demonstrate a new gel polymer interface (GPI) consisting of crosslinked polyethyleneimine with a large amount of amino and carboxylic acid groups introduced between the positive electrode and the membrane. The GPI functions as a key component to prevent vanadium ions from crossing the membrane, thus supporting stable long-term cycling. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were conducted to investigate the effect of GPI on the electrochemical properties of graphitic carbon electrodes (GCFs) and redox reaction of catholyte. X-ray photoelectron spectroscopy (XPS) and 1H nuclear magnetic resonance (NMR) spectra demonstrated that the crosslinked GPI is chemically stable for 100 cycles without dissolution of polymers and swelling in the strong acidic electrolytes. Results from inductively coupled plasma mass spectrometry (ICP-MS), Fourier-transform infrared (FTIR) spectroscopy, and energy-dispersive X-ray (EDX) spectroscopy proved that the GPI is effective in maintaining the concentration of vanadium species in their respective half-cells, resulting in improved cycling stability because of it prevents active species from crossing the membrane and stabilizes the oxidation states of active species.
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Tanaka, Takeshi, Masaru Takizawa, and Akihiro Hata. "Verification of the Effectiveness of UV-Polishing for 4H-SiC Wafer Using Photocatalyst and Cathilon." International Journal of Automation Technology 12, no. 2 (March 1, 2018): 160–69. http://dx.doi.org/10.20965/ijat.2018.p0160.
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The polishing of 4H-SiC wafer processed under ultraviolet (UV) irradiation was investigated to verify the phenomena and effectiveness of ultraviolet-ray aided machining (U-RAM). Inductively coupled plasma spectrometry (ICPS) analysis was conducted to quantitatively determine the oxidation/dissolution volume of SiC. X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) were used to qualitatively analyze the 4H-SiC surfaces. These analyses were used to clarify the compounds that are formed/removed by the decomposition of cathilon dye and water during the polishing of 4H-SiC using TiO2-, cathilon- and TiO2-cathilon (mixed) slurries, all of which contained diamond particles. ICPS measurements indicate that a small amount of Si dissolves in aqueous solutions of cathilon- and TiO2-cathilon. XAS and XPS measurements indicate that SiC composes the bulk of the as-received 4H-SiC, and the surface and thin surface form an interface oxide inside SiC. The chemical-mechanical polishing of 4H-SiC using the TiO2-cathilon slurry forms an oxide, interface oxide, oxynitride and nitride. Diamond particles easily remove these compounds by mechanical scratching. It is possible to attain smaller surface roughness and higher polishing efficiency by combination with chemical reaction of TiO2-cathilon slurry and mechanical action of diamond particles under UV irradiation.
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Shi, Xin, Xinyue Liu, Xianshuo Cao, Xiaoning Cheng, and Xihong Lu. "Oxygen functionalized interface enables high MnO2 electrolysis kinetics for high energy aqueous Zn-MnO2 decoupled battery." Applied Physics Letters 121, no. 14 (October 3, 2022): 143903. http://dx.doi.org/10.1063/5.0116388.
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Aqueous Zn-based batteries show great potential in large scale energy storage system due to their low-cost and high-safety merits. However, the practical application of Zn-based batteries is restricted by their inferior energy and power densities, which is resulted from the low output voltage and poor reaction kinetics of cathode materials. To address the above issues, we propose a decoupled aqueous Zn–Mn battery with high-rate and high-voltage by using oxygen functionalized carbon nanotubes (OCNTs) substrate. The functional interface can greatly improve the wettability of the electrode, promote the ion transport capability, and facilitate the rapid deposition/dissolution of MnO2/Mn2+. Consequently, the OCNTs/MnO2 electrode can deliver a high capacity of 9.2 mA h cm−2 and superior capacity retention of 86.6% at an ultrahigh current density of 200 mA cm−2. When coupled with Zn anode, the Zn//OCNTs/MnO2 decoupled full battery exhibits a high discharge plateau (∼2.45 V) and area specific capacity (1.96 mA h cm−2) at a current density of 2 mA cm−2. Moreover, the outstanding peak power density of 13.4 kW kg−1 and peak energy density of 564.4 W h kg−1 can be achieved for Zn//OCNTs/MnO2 battery (based on the mass of active material involved in the reaction on the positive and negative electrodes during charge and discharge), far beyond currently reported aqueous electrochemical energy storage devices. This work provides a train of thoughts for the development of high energy and power density aqueous batteries.
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Emberson, Robert, Niels Hovius, Albert Galy, and Odin Marc. "Oxidation of sulfides and rapid weathering in recent landslides." Earth Surface Dynamics 4, no. 3 (September 22, 2016): 727–42. http://dx.doi.org/10.5194/esurf-4-727-2016.
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Abstract. Linking together the processes of rapid physical erosion and the resultant chemical dissolution of rock is a crucial step in building an overall deterministic understanding of weathering in mountain belts. Landslides, which are the most volumetrically important geomorphic process at these high rates of erosion, can generate extremely high rates of very localised weathering. To elucidate how this process works we have taken advantage of uniquely intense landsliding, resulting from Typhoon Morakot, in the T'aimali River and surrounds in southern Taiwan. Combining detailed analysis of landslide seepage chemistry with estimates of catchment-by-catchment landslide volumes, we demonstrate that in this setting the primary role of landslides is to introduce fresh, highly labile mineral phases into the surface weathering environment. There, rapid weathering is driven by the oxidation of pyrite and the resultant sulfuric-acid-driven dissolution of primarily carbonate rock. The total dissolved load correlates well with dissolved sulfate – the chief product of this style of weathering – in both landslides and streams draining the area (R2 = 0.841 and 0.929 respectively; p < 0.001 in both cases), with solute chemistry in seepage from landslides and catchments affected by significant landsliding governed by the same weathering reactions. The predominance of coupled carbonate–sulfuric-acid-driven weathering is the key difference between these sites and previously studied landslides in New Zealand (Emberson et al., 2016), but in both settings increasing volumes of landslides drive greater overall solute concentrations in streams. Bedrock landslides, by excavating deep below saprolite–rock interfaces, create conditions for weathering in which all mineral phases in a lithology are initially unweathered within landslide deposits. As a result, the most labile phases dominate the weathering immediately after mobilisation and during a transient period of depletion. This mode of dissolution can strongly alter the overall output of solutes from catchments and their contribution to global chemical cycles if landslide-derived material is retained in catchments for extended periods after mass wasting.
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Kang, Sinwoo, Changbin Im, Ioannis Spanos, Kahyun Ham, Ahyoun Lim, Robert Schlögl, Timo Jacob, and Jaeyoung Lee. "Improved Stability of Nickel-Iron Based Oxygen Evolution Electrocatalyst By the Immobilization of Tetraphenylporphyrin." ECS Meeting Abstracts MA2022-02, no. 49 (October 9, 2022): 1943. http://dx.doi.org/10.1149/ma2022-02491943mtgabs.
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Anion exchange membrane water electrolysis (AEMWE) is an attractive technology for the production of green hydrogen and has advantages in terms of cost owing to the use of non-precious catalyst materials. NiFe-based materials are the best-in-class electrocatalysts for the alkaline oxygen evolution reaction. Defining the active sites of NiFe-based materials has been a controversial issue over the past decades. Previously, Ni was regarded as an active site; however, active sites, such as Fe or Ni–Fe dual active sites have been considered in recent studies. Despite the complexity of heterogeneous catalysis, with the aid of in situ/operando measurements and density functional theory (DFT) calculations, Fe was selected as the ultimate active site in state-of-the-art materials. However, the electrocatalyst suffers from rapid degradation in Fe-purified KOH. Herein, we report a catalyst/electrolyte interface engineering strategy using tetraphenylporphyrin (TPP) to alleviate the destabilization of NiFe-based catalysts. The online electrochemical flow cell inductively coupled plasma-optical emission spectroscopy proved that thermodynamically unstable Fe liberation was the primary cause of deactivation. TPP acts as a protective layer and suppresses hydrated metal dissolution at the catalyst/electrolyte interface. The stable TPP layer on NiFe elongates the lifetime near the electrode, enhancing the redeposition kinetics of the active site, Fe. As a proof of concept, the role of TPP was validated at the half-cell and 2.4 times suppression of degradation rate in AEMWE scale at a constant current density of 500 mA cm-2. This strategy of using a TPP as a protective layer may serve as a new platform for stable oxygen evolution electrocatalysts.
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You, Jiahui, and Kyung Jae Lee. "Analyzing the Dynamics of Mineral Dissolution during Acid Fracturing by Pore-Scale Modeling of Acid-Rock Interaction." SPE Journal 26, no. 02 (January 12, 2021): 639–52. http://dx.doi.org/10.2118/200406-pa.
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Summary Hydrochloric acid (HCl) is commonly used in acid fracturing. Given that the interaction between acid and rock affects multiphase flow behaviors, it is important to thoroughly understand the relevant phenomena. The Darcy-Brinkman-Stokes (DBS) method is most effective in describing the matrix-fracture system among the proposed models. This study aims to analyze the impact of acid-rock interaction on multiphase flow behavior by developing a pore-scale numerical model applying the DBS method. The new pore-scale model is developed based on OpenFOAM, an open-source platform for the prototyping of diverse flow mechanisms. The developed simulation model describes the fully coupled mass balance equation and the chemical reaction of carbonate acidizing in an advection-diffusion regime. The volume of fluid (VOF) method is used to track the liquid- and gas-phase interface on fixed Eulerian grids. Here, the penalization method is applied to describe the wettability condition on immersed boundaries. The equations of saturation, concentration, and diffusion are solved successively, and the momentum equation is solved by pressure implicit with splitting of operators method. The simulation results of the developed numerical model have been validated with experimental results. Various injection velocities and the second Damkohler numbers have been examined to investigate their impacts on the CO2 bubble generation, evolving porosity, and rock surface area. We categorized the evolving carbon dioxide (CO2) distribution into three patterns in terms of the Damkohler number and the Péclet number. We also simulated a geometry model with multiple grains and a Darcy-scale model using the input parameters found from the pore-scale simulations. The newly developed pore-scale model provides the fundamental knowledge of physical and chemical phenomena of acid-rock interaction and their impact on acid transport. The modeling results describing mineral acidization will help us implement a practical fracturing project.
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Hastie, Evan C. G., Daniel J. Kontak, and Bruno Lafrance. "Gold Remobilization: Insights from Gold Deposits in the Archean Swayze Greenstone Belt, Abitibi Subprovince, Canada." Economic Geology 115, no. 2 (March 1, 2020): 241–77. http://dx.doi.org/10.5382/econgeo.4709.
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Abstract Recognizing if and how Au is remobilized, in solid, melt, or fluid state, is critical for understanding the origin of high-grade ore zones in Au deposits. When evidence for Au remobilization can be demonstrated, then primary versus secondary processes can be distinguished, resulting in a more complete understanding of Au deposit formation. To address this, samples from two Au deposits, Jerome and Kenty, in the Archean Swayze greenstone belt of northern Ontario, Canada, together with archived samples from 39 high-grade Au deposits from the Abitibi greenstone belt across Ontario and Quebec, were geochemically characterized using integrated scanning electron microscopy-energy dispersive spectroscopy and electron microprobe imaging and analyses in addition to laser ablation-inductively coupled plasma-mass spectrometry elemental mapping. These data provided the basis to develop a model for Au remobilization and upgrading of Au that is widely applicable to orogenic gold settings. Data for the Jerome deposit indicate that Au uptake into early pyrite was not due to pulsing of different fluids, but instead was predominantly controlled by S availability, whereby the oscillatory/sector zoning in pyrite resulted from the substitution of As into S sites during rapid growth due to local chemical disequilibrium. In addition, Au-bearing pyrite from both the Jerome and Kenty deposits records textures, such as porosity development coincident with the presence of native gold and accessory sulfide phases, that are strongly suggestive of coupled dissolution-reprecipitation (CDR) reactions that liberated Au and associated elements from earlier auriferous (100–5,000 ppm Au) pyrite. During the remobilization process, Au and Ag were decoupled, which resulted in (1) a change in Au/Ag ratios of 0.5 to 5 in early pyrite to ≈9 in the new native gold (900 Au fineness) and (2) incorporation of Ag into cogenetic secondary mineral phases (e.g., chalcopyrite, tetrahedrite, and galena). Evidence for an association of low-melting point chalcophile elements (LMCE; Hg, Te, Sb, and Bi) with Au at the Jerome, Kenty, and many (>50%) of the 39 historic deposits sampled, along with native gold filling structurally favorable sites in vein quartz in all samples, indicates a fluid might not have been the only factor contributing to remobilization. This systematic Au-LMCE association strongly supports a model whereby Au is released by CDR reactions and is then remobilized by fluid-mediated, LMCE-rich melts that began to form at 335°C and/or by local, nanoparticle (nanomelt?) transport during deformation and metamorphism. Conclusions drawn from this study have implications for Au deposits globally and can account for the common presence of coarse-grained, commonly crystalline, native gold filling fractures in quartz and the paragenetically late-stage origin of gold in veins. They can also better explain the inability of Au in solution remobilization models to account for locally high gold grades, given the relatively low solubility of Au in hydrothermal fluids.
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Alotaibi, Mohammed B., Dongkyu Cha, Karam Chand, and Ali A. Yousef. "Effects of ions on the characteristics of monolayer at brine/oil interfaces." E3S Web of Conferences 89 (2019): 04003. http://dx.doi.org/10.1051/e3sconf/20198904003.
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The advanced waterflooding technologies through salinity and ionic content adjustment can make favorable impacts on rock wettability and oil recovery. In carbonate reservoirs, SmartWater at low ionic strength showed strong chemical interactions with carbonate minerals and oil components. As a result, several hypotheses are proposed in literature as ionic exchange, rock dissolution, surface charges and others. The applied macroscopic and microscopic technologies have certain limitations in identifying the structures at interfaces especially at monolayers. In this paper, advanced Sum Frequency Generation (SFG) spectroscopy is utilized for the first time to characterize the chemical structures of molecules at the brine/oil interfaces. Different brines recipes and model oil are tested to determine the effects of individual and combined ions on the monolayer structures. Stearic acid is also mixed with hydrocarbons to mimic the acidity condition of fluids in the reservoir. The change in the chemical structure is mo nitored with time at a broad wavenumber range from 1,000 to 3,800 cm-1. Distinct spectral signatures of oil components and water ions are detected at different pH conditions. The SFG data is compared with the previous macroscopic wettability results to predict the components that are highly affected during waterflooding and enhanced oil recovery (EOR) processes. This study brings new insights on understanding the chemical structures at the thin monolayers of flat and curved geometric at different aqueous interfaces. The measured spectra, coupled with a wide range of laser polarization settings, and signal intensity trends are discussed in terms of composition, and structure of organic and inorganic components. For example, the intensity for SmartWater at certain wavenumber is three folds higher when compared to high salinity water. This indicates that the interactions at oil/water interfaces are enhanced at lower ionic strengths. In addition, these findings are also confirmed with similar behaviors at a higher salinity brine as connate formation brine. The novelty of this interfacial study can provide better understanding of the reaction mechanisms altering the ionic strength and salinity of injection water and its impact due to the changes in geometric interfaces. Such understanding is also crucial to optimize the chemistry of injection water and its interaction with oil components and carbonate rock, to ultimately alter wettability toward water-wet.
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Figowy, Sarah, Benoît Dubacq, Yves Noël, and Philippe d'Arco. "Partitioning of chromium between garnet and clinopyroxene: first-principle modelling versus metamorphic assemblages." European Journal of Mineralogy 32, no. 4 (July 3, 2020): 387–403. http://dx.doi.org/10.5194/ejm-32-387-2020.
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Abstract. Understanding the geochemical behaviour of trace and minor elements in mineral assemblages is of primary importance to study small- and large-scale geological processes. Partition coefficients are frequently used to model the chemical evolution of minerals and fluids during melting and in metamorphic rocks of all grades. However, kinetic effects hampering equilibrium partitioning may invalidate the modelling. This study aims at calculating partition coefficients and testing their applicability in natural mineral assemblages, choosing Cr in garnet and clinopyroxene via exchange with Al as a case study. First-principle modelling has been combined with measurements and element mapping to estimate partition coefficients for Cr and the deviation from equilibrium. Results highlight the role of crystal chemistry over the strain field around point defects, controlling the dynamics of the Cr3+ = Al3+ exchange between clinopyroxene and garnet. Ab initio calculations allowed estimation of Cr partition coefficients between garnet and clinopyroxene, using a thermodynamic approach based on endmembers and mixing models simplified for trace element behaviour. The Cr3+ = Al3+ exchange reaction between garnet and the jadeite component of clinopyroxene depends on the grossular and pyrope content, with Cr preferentially incorporated into grossular over jadeite but preferentially incorporated into jadeite over pyrope. Comparison of predicted partition coefficients to measured concentrations in natural samples, together with element mapping, shows large disequilibrium. Cr-rich and Cr-poor sectors exhibit disequilibrium attributed to slow diffusivity of Cr during crystal growth and interface-coupled dissolution–precipitation, even for garnet–clinopyroxene assemblages crystallized around 850 ∘C.
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Lönartz, Mara I., Jenna Poonoosamy, Yuankai Yang, Naila Ait-Mouheb, Guido Deissmann, and Dirk Bosbach. "Deciphering porosity clogging at barrier interfaces in deep geological repositories for radioactive waste." Safety of Nuclear Waste Disposal 1 (November 10, 2021): 181–82. http://dx.doi.org/10.5194/sand-1-181-2021.
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Abstract. The disposal of spent nuclear fuels and high-level radioactive wastes in deep geological repositories represents one of the greatest scientific-technical and societal challenges of our times. Most disposal concepts rely on a multibarrier system, consisting of a combination of engineered materials, geotechnical and geological barriers to provide a safe containment of the radioactive waste to protect humans and the environment against dangers arising from ionizing radiation. A reliable safety assessment of a deep geological repository over assessment time scales of several 100 000 years requires a profound and comprehensive understanding of the complex coupled physical (thermal, hydraulic, mechanical), chemical and biogeochemical (THM/CB) processes that govern the long-term evolution of the repository system. As a result of thermal and chemical gradients at the interfaces of different components and materials of the multi-barrier system (e.g. interfaces between metallic waste containers and bentonite backfill or between structural concrete and clay host rock), mineral dissolution and precipitation reactions are promoted; thus the (local) porosity, the volume filled with gas and/or water, can increase or decrease leading to changes in the macroscopic transport properties of the respective media. Although a reduction of the porosity (porosity clogging) appears to be desirable to inhibit radionuclide migration, it can also be detrimental, particularly in the case of gas pressure build-up due to canister corrosion or bacterial activity. So far, porosity clogging at barrier interfaces and associated consequences on solute or gas transport remain poorly understood; currently used mathematical descriptions of porosity clogging in reactive transport codes usually fail to capture respective experimental observations (Chagneau et al., 2015; Deng et al., 2021). In this context, we are developing a “lab-on-a-chip” set-up, which combines time lapse optical microscopy imaging and in operando Raman spectroscopy (Poonoosamy et al., 2019, 2020) to determine (i) whether complete clogging is possible and permanent, (ii) which parameters control the porosity clogging and (iii) which changes in transport properties of porous media are induced due to porosity clogging. Our approach comprises micronized counterdiffusion experiments with in situ visualization and monitoring of the evolution of mineralogy and microstructure/pore architecture with time. Complementary pore scale modelling will be used to derive key relationships that describe changes in transport properties due to mineral precipitation-induced porosity clogging. This approach will help to improve reactive transport codes and their predictive capabilities thus enhancing confidence and reduce uncertainties in long-term predictions, leading to more realistic descriptions of the evolution of complex repository systems.