Sulfur Dissolution Research Articles

Corrosion mechanisms of 316L stainless steel in polyphosphoric acid at elevated temperature: Behavior and mechanistic insights

The performance of 316 L stainless steel in polyphosphoric acid (PPA) at high temperature, remains a subject of considerable interest. Through weight-loss tests, electrochemical analyses, SEM, XRD, XPS, and ICP, the corrosion process of 316 L in PPA and the formation of corrosion products are systematically examined. The results elucidate a multi-step corrosion mechanism involving selective dissolution of sulfur and chromium, succeeded by the involvement of additional metallic elements, notably iron, in the construction of the corrosion product layers. This study contributes to a deeper understanding of 316 L stainless steel corrosion in PPA environments, offering insights crucial for corrosion mitigation and material design.

Investigation of Polysulfide Adsorption on FeS2 Additive in Sulfur Cathode of Li–S Battery by Ex situ UV–Visible Spectroscopy

The performance of lithium–sulfur (Li–S) rechargeable batteries is strongly dependent on the entrapment of the higher‐order intermediate polysulfides at the sulfur cathode. An attracting way of preventing the polysulfide shuttle is by introducing a polar host which can form a Lewis acid–base complex with polysulfides. Herein, the Li–S battery by incorporating iron sulfides (FeS2) as a polar Lewis acid to entrap higher‐order polysulfides at the cathode center is investigated. FeS2/S cathode demonstrates largely improved retention of capacity compared to C/S cathode (capacity fading per cycle of 0.12% and 0.80% for FeS2/S and C/S respectively) and good rate performance in Li–S batteries compared to conventional carbon–sulfur (C/S) cathode. This is attributed to the decrease in polysulfide dissolution and better retention of active sulfur in the cathode during battery cycling which is due to the polar FeS2 additive that well anchors polysulfides. The effect of FeS2 in preventing the shuttle mechanism is demonstrated by ex situ UV–vis spectroscopy and ex situ Raman spectroscopy studies.

Microscopic Mechanism and Percolation Model of Dynamic Deposition of Elemental Sulfur Particles in Acidic Gas Reservoirs.

The dissolution of elemental sulfur in acidic gas leads to its precipitation as gas pressure decreases, thereby causing potential damage to the formation due to the deposition of sulfur particles. Previous sulfur deposition prediction models often relied on the solubility of sulfur in acidic gas and the stress state of sulfur particles to determine the occurrence of deposition, thus establishing predictive models. However, in the presence of complex geological conditions, the multiphase flow through porous media and the adsorption of particles on pore throat walls can also influence sulfur particle deposition to some degree. It is well known that sulfur particle deposition during gas reservoir development exhibits instability, with multiple factors influencing the deposited sulfur particles. Particularly noteworthy is the influence of airflow velocity, which can resuspend sulfur particles that are physically adsorbed on pore throat surfaces, thereby reintegrating them into the gas phase. Additionally, the dynamic deposition of larger sulfur particles involves a dynamic process. This study elucidates the dynamic process of sulfur deposition by considering the diverse transport dynamics of sulfur particles. Physical adsorption and desorption behaviors of sulfur particles are determined based on variations in reservoir conditions. The desorption status of sulfur particles with different particle sizes within the formation is established by evaluating the equilibrium between the force exerted on the pore throat wall and the suspension force generated by gas flow. The critical conditions for sulfur deposition in Yuanba gas reservoir were obtained by substituting on-site parameters into calculations. Moreover, a mathematical model is proposed to describe the dynamic deposition and migration of sulfur particles, adopting principles from continuous porous media porous flow theory, fluid flow mass conservation, as well as sulfur particle desorption and migration. The formulated model is solved, and its resulting solution process and outcomes hold significant implications for numerical simulation and predictive assessment of the development impact on gas reservoirs, particularly in later stages.

A diamond-bearing core-mantle boundary on Mercury

Abundant carbon was identified on Mercury by MESSENGER, which is interpreted as the remnant of a primordial graphite flotation crust, suggesting that the magma ocean and core were saturated in carbon. We re-evaluate carbon speciation in Mercury’s interior in light of the high pressure-temperature experiments, thermodynamic models and the most recent geophysical models of the internal structure of the planet. Although a sulfur-free melt would have been in the stability field of graphite, sulfur dissolution in the melt under the unique reduced conditions depressed the sulfur-rich liquidus to temperatures spanning the graphite-diamond transition. Here we show it is possible, though statistically unlikely, that diamond was stable in the magma ocean. However, the formation of a solid inner core caused diamond to crystallize from the cooling molten core and formation of a diamond layer becoming thicker with time.

The Challenge of Electrolyte Impregnation in the Fabrication and Operation of Li‐ion and Li−S Batteries

AbstractModeling and simulations, coupled with selected experimental studies for validation, are employed to analyze electrolyte impregnation in battery fabrication, elucidate and assess its effects on battery operation. Digital twins of the electrolyte filling process or the cell cycling are based on continuum‐level physicochemical models taking into account the pore size distribution of the porous cathode and separator, dissolution and precipitation of any solutes such as sulfur or sulfides; additionally, ion transport and redox reactions in the liquid electrolyte for simulations of battery cycling. Electrolyte impregnation highly depends on cell format, with a cylindrical Li‐ion cell predicted to take up to 7 days under rest for homogeneous electrolyte distribution. Simulations of the electrolyte infiltration in Li−S coin cells revealed sulfur dissolution and reprecipitation, which was verified by experiments using in operando microscopy. Simulations of the first discharge of electrolyte‐lean Li−S cells demonstrated the effects of poor micropore wetting by the electrolyte.

Application of sulfur-based composite materials in the positive electrode of lithium-sulfur batteries

Traditional lithium-ion batteries are no longer able to keep up with the growing need for energy storage efficiency in areas like electric cars and renewable energy storage. Because of their great energy density, affordability, and environmental friendliness, lithium-sulfur batteries are regarded as a very promising solution for secondary battery systems. Sulfur-based compounds are an essential part of lithium-sulfur batteries and have a direct impact on the battery’s energy density and performance. However, sulfur-based compounds are easily soluble in electrolytes and have low conductivity, which shortens battery cycle life and energy efficiency. Sulfur dissolution can be successfully inhibited and capacitance may be enhanced by optimizing the structure and characteristics of sulfur-based materials, which will improve the overall performance of lithium-sulfur batteries. To enhance the performance of lithium-sulfur batteries, this article suggests three modification techniques for sulfur-based materials. These techniques mostly include compounding sulfur with carbon compounds, metal oxides, and polymers. This article also outlines the shortcomings of the present lithium-sulfur battery research and looks forward to the future development direction.

Molecular mechanism of elemental sulfur dissolution in H2S under stratal conditions.

Resulting from the solubility reduction of elemental sulfur during the development of high sulfur gas formations, sulfur deposition often occurs to reduce the gas production and threaten the safety of gas wells. Understanding the dissolution mechanism of elemental sulfur in natural gas is essential to reduce the risk caused by sulfur deposition. Because of the harsh conditions in the high-sulfur formations, it remains challenging to in situ characterize the dissolution-precipitation processes, making deficient the knowledge of sulfur dissolution mechanism. The dissolution of sulfur allotropes (SN, N = 2, 4, 6 and 8) in H2S, the main solvent of sulfur in natural gas, is studied in this work by means of first-principles calculations and molecular dynamics simulations. While S6 and S8 undergo physical interaction with H2S under the conditions corresponding to those at 1-6 km stratigraphic depths, S2 and S4 react with H2S and form stable polysulfides. Unravelling the mechanism would be helpful for understanding and controlling the sulfur deposition in high-sulfur gas development.

Highly Concentrated Electrolytes for Lithium Sulfur Batteries – the Role of the Anion(s)

Lithium-sulfur batteries (Li-S) have attracted a lot of attention as a alternative/complement to lithium-ion batteries (LIBs) – due to both high energy density, availability, and inexpensive materials used.[1]Yet, dissolution of sulfur from the C/S cathode and subsequent shuttling of lithium polysulfides (LiPS) to the anode as well as the instability of the Li metal anode itself are true scientific and technological challenges. Advancing in the field of electrolytes is one promising way to overcome both issues.Switching from the standard 1 M electrolyte design of LIBs to highly concentrated electrolytes (HCEs) may both prevent the dissolution of LiPSs and hinder dendrite formation at the lithium metal anode.[2]Here we combine experimental methods and computational approaches to investigate several HCEs based on various Li-salts in several standard organic solvents. Experimentally we targeted electrochemical properties, local electrolyte structure, and physico-chemical properties, with focus on the role(s) of the Li-salt anions. Furthermore, to predict the solubility of sulfur the conductor like screening model for real solvents (COSMO-RS), a computational fluid phase thermodynamic approach, was used.[3] Overall, the challenges and opportunities associated with the use of HCEs in Li-S batteries will be addressed, also highlighting potential areas for future research and development.References Peng et al., "Drastic effect of salt concentration in ionic liquid on performance of lithium sulfur battery." Journal of the Electrochemical Society 169.5 (2022): 050515.Suo et al., "A new class of solvent-in-salt electrolyte for high-energy rechargeable metallic lithium batteries." Nature communications 4.1 (2013): 1481.Jeschke and P. Johansson, "Predicting the Solubility of Sulfur: A COSMO‐RS‐Based Approach to Investigate Electrolytes for Li–S Batteries." Chemistry–A European Journal 23.38 (2017): 9130-9136.

Simulation of Lithium-Sulfur Batteries and Optimization of Cathode Structure

Recently, the spread of the mobile devices and clean energy, the demand for high-power and high-capacity secondary batteries has been growing. However, the energy density of lithium-ion batteries (LiB) that is widely used nowadays is reaching its design limit. Instead of LiB, lithium-sulfur batteries (LiSB) are expected as one of the next-generation secondary batteries. Compared to LiB, LiSB has the advantages of higher energy density, lower cost, and easier weight saving. In LiB, the driving force is the insertion and desorption reaction of lithium ions between the cathode and anode, while in LiSB, is the complex sulfur dissolution and precipitation reaction. In LiSB, the electrolyte determines the dissolution and precipitation of sulfur, which is thought to have a significant impact on battery characteristics. Therefore, new electrolyte systems are being developed daily and techniques to elucidate the reaction mechanisms are needed. Furthermore, the effect of carbon black, a conductive material, on battery characteristics has also been considered. In this study, we investigated the optimal initial lithium ion concentration and calculation focused on the precipitation form of each carbon species for the design of optimal electrode structures.Kumaresan's one-dimensional model [1] based on porous electrode theory was used. Sulfur was used as the cathode active material and lithium metal as the anode active material. Electron and ionic potentials were calculated from the electro-neutrality condition, concentration distribution in the electrolyte was calculated from the non-stationary mass balance equation, and electrochemical reactions at the interface between active material and electrolyte were calculated using the Butler-Volmer equation. Furthermore, stepwise reactions were considered by incorporating the electrochemical reaction of sulfur and the dissolution and precipitation reactions into the concentration distribution and the interfacial reactions. The temperature in the electrode layer was assumed to be constant, and no heat loss or side reactions due to overvoltage were assumed to occur. In LiSB, sulfur dissolved in the electrolyte on the cathode surface is sequentially reduced as polysulfide ions as the discharge progresses. It then combines with lithium ions transferred from the anode and expands to about 1.8 times. Therefore, based on our previous research [2], the effect of the expansion and contraction of the electrode particles was reflected by dynamic changes in the structural properties of the electrode layer.Ionic conductivity and transport number are important parameters that affect the properties of the electrolyte. The higher the lithium ion concentration, the higher the transport number, but the lower the ionic conductivity [3]. In this study, we focused on sulfolane-based electrolyte and investigated the effect of initial lithium ion concentration on discharge capacity by incorporating the relationship between ionic conductivity and transport number into a model. As a result, the discharge capacity reached its maximum when the initial lithium ion concentration was 3.0 M. In the static state, the ionic conductivity was highest around 1.6 M, but considering the operating conditions during discharge, the concentration distribution became be more remarkable due to the low transport number, which may have resulted in excessive Li2S precipitation near the separator. As an extension to the microstructure of the electrode layer, we focused on carbon black (CB). Two types of CB (KB, MCND) were targeted. When MCND and KB were used as CB under the same conditions in the experiment, it was confirmed that the discharge characteristics of MCND were significantly better than those of KB. In LiSB, Li2S precipitation has a significant effect on discharge characteristics. Therefore, we focused on the pores of both CBs. We reconstructed the binarized structure from X-ray CT images of both CBs, hypothetically precipitated Li2S in the pores, and calculated the relative conductivity. The relative conductivity represents the transport property and is highly dependent on the structure of the electrode layer. As a calculation result, the relative conductivity of KB became significantly smaller as the porosity decreased. From the above, the transport properties in both CBs were confirmed by calculation.As described above, it was suggested that an optimum lithium ion concentration exists, and the effect of different CB structures on transport properties was qualitatively evaluated. In the future, it is necessary to confirm the validity of the optimal concentration through experiments and to quantitatively evaluate the effect of different CB.AcknowledgmentThis study was supported by JST ALCA-SPRING Grant JPMJAL1301, Japan.

Biooxidation of refractory silver minerals as pretreatment for silver recovery

The worldwide demand for silver is increasing due to the technological development in different areas, especially for the requirements in the production of renewable energies; therefore, for the treatment of refractory minerals by conventional processes, it is necessary to study mechanisms to identify the viability of their processing and the feasibility of their recovery, ensuring profitability. Gold and silver present in the matrix of sulfide-based ores are not affordably recovered by the conventional method involving leaching in sodium cyanide solution. Therefore, it must be subjected to oxidation pretreatment or conversion of the sulfides to simple compounds that allow recovery of the precious metals. The methods of oxidation of minerals considered refractory are carried out by hydro and pyrometallurgical methods, seeking the dissolution of sulfur, iron, arsenic and other elements present. It is important to identify and consider the mineralogical structure, microbiological variety, physicochemical characteristics, types of reactors, bacterial interactions, among other factors. The choice of biooxidation as the preferred process in projects for the recovery of gold, silver, copper or other metals, in most cases is based on the economic advantage, compared to the conventional processes of roasting, chemical leaching and pressurized leaching. The biooxidation of refractory argentiferous ores has been extensively studied in recent years, concluding that its application is feasible, mainly because it is environmentally friendly.

The multiple sulfur isotope architecture of the Kambalda nickel camp, Western Australia

New data on the multiple sulfur isotope signature of Archean sulfides from country rocks and magmatic mineralization at the Moran deposit (Kambalda, Western Australia) were combined with previously published geochemical data to constrain the various stages of the dynamic evolution of this magmatic system, unveiling new insights into the transport mechanisms of sulfide liquids in komatiite magmas. Sulfides in the Archean magmatic and sedimentary host rocks of the komatiites display a unique mass-independent sulfur isotope signature (Δ33S), which records a photochemical reaction of sulfur in an oxygen-poor atmosphere prior to the Great Oxidation Event.Sedimentary rocks that are thought to be assimilated by komatiite show a distinctly positive Δ33S signature (+ 0.9 to + 2.4‰). Early ore sulfides situated above these sedimentary rocks contain relatively few valuable metals and display an overlapping Δ33S range (+ 0.6 to + 1.0‰). Subsequent but still early ore sulfides are situated above basalt, as the sedimentary rocks were thermo-mechanically eroded by the sulfide melt, displaying more mantle-like signatures (+ 0.2 to + 0.3‰) and valuable metal content - indistinguishable from the main ore deposit. This reflects a progressive dilution of the contaminant signature by the magmatic isotope signature of the komatiite liquid. Calculated volumes of the interaction of silicate melt and sulfide melt to explain the metal tenor of the ore and its Δ33S signature indicate a decoupling between chemical and isotopic signatures. This can be explained by upgrading the sulfide melt with valuable metals simultaneously with the dissolution of sulfur in the komatiite melt.

Use of Sulfur Waste in the Production of Metakaolin-Based Geopolymers

This preliminary study introduces the incorporation and chemical stabilization of sulfur waste into a geopolymer matrix and explores the concept of material production for further environmental and engineering solutions. In this study, a novel synthesis procedure for sulfur-based geopolymers was introduced, and the role of sulfur in geopolymers and its optimal content to obtain a stable structure were explored. Geopolymers were synthesized by dissolving sulfur in an alkaline activator in different proportions. The alkaline solution was then mixed with metakaolin to synthesize the geopolymer matrix. Adding sulfur in amounts from 0 wt.% to 5 wt.%, compared with metakaolin, led to an increase in the compressive strength of the geopolymers from 22.5 MPa to 29.9 MPa. When sulfur was between 5 wt.% and 15 wt.%, a decrease in the compressive strength was observed to 15.7 MPa, which can be explained by defects and voids in the geopolymer’s microstructure due to the solubility of excess sulfur. Because of the incorporation of sulfur into the geopolymers, a compact and dense microstructure was formed, as reported in the SEM analysis. An XRD analysis showed that, besides quartz and analcime, a new phase, Al2·H10·O17·S3, was also formed as a result of sulfur dissolution in the alkaline activator of the geopolymers.

Investigation of the Reaction Mechanism of All-Solid-State Lithium-Sulfur Batteries by Operando in Situ Raman Spectroscopy

In recent years, all-solid-state lithium-sulfur batteries (ASSLSBs) with sulfide-based solid electrolytes have become a leading energy storage system due to their high ionic conductivity, ultra-high energy density, high safety, and low cost. There have been many challenges with the practical applications of Li-S batteries, however, as a result of the sluggish redox kinetics of lithium polysulfide (LPS) and its shuttling effects. Single-atom catalysts (SACs) with atomically dispersed metal-based sites have proven to be promising electrocatalysts in Li-S batteries. To construct the ASSLSBs, we design and develop MoS2/SnS2 and Fe SACs with MoS2/SnS2 cathodes, Li5.4PS4.4Cl1.6 sulfide-based solid electrolytes, and Li-In anode. In the current study, in situ Raman spectroscopy is used to determine the LPS species in the sulfur cathode with SACs and without SACs during the ASSLSBs cycling. The aim is to understand the charge-discharge mechanism and the influence of SACs on the dissolution of sulfur and poly-sulfides. As compared to the MoS2/SnS2 cathode, the Fe@MoS2/SnS2 cathode exhibit the highest catalytic LPS conversion. In addition, the Fe@MoS2/SnS2 cathode delivers a high discharge capacity and long-cycling performance with high coulombic efficiency in ASSLSBs. In operando in situ Raman studies, SACs provide important new insights into the charge-discharge reaction mechanism for the next generation of ASSLSBs.

Homologous Heterostructured NiS/NiS2 @C Hollow Ultrathin Microspheres with Interfacial Electron Redistribution for High-Performance Sodium Storage.

Nickel sulfides with high theoretical capacity are considered as promising anode materials for sodium-ion batteries (SIBs); however, their intrinsic poor electric conductivity, large volume change during charging/discharging, and easy sulfur dissolution result in inferior electrochemical performance for sodium storage. Herein, a hierarchical hollow microsphere is assembled from heterostructured NiS/NiS2 nanoparticles confined by in situ carbon layer (H-NiS/NiS2 @C) via regulating the sulfidation temperature of the precursor Ni-MOFs. The morphology of ultrathin hollow spherical shells and confinement of in situ carbon layer to active materials provide rich channels for ion/electron transfer and alleviate the effects of volume change and agglomeration of the material. Consequently, the as-prepared H-NiS/NiS2 @C exhibit superb electrochemical properties, satisfactory initial specific capacity of 953.0mA h g-1 at 0.1 A g-1 , excellent rate capability of 509.9mA h g-1 at 2 A g-1 , and superior longtime cycling life with 433.4mA h g-1 after 4500 cycles at 10 A g-1 . Density functional theory calculation shows that heterogenous interfaces with electron redistribution lead to charge transfer from NiS to NiS2 , and thus favor interfacial electron transport and reduce ion-diffusion barrier. This work provides an innovative idea for the synthesis of homologous heterostructures for high-efficiency SIB electrode materials.

Molecular mechanism in the solubility reduction of elemental sulfur in H2S/CH4 mixtures: A molecular modeling study

The solubility evolution of elemental sulfur in sour gas is key to study the occurrence and inhibition of sulfur deposition in the exploitation of high-sulfur gas reservoirs. Elemental sulfur mainly dissolves in H2S, and its solubility decreases dramatically in the presence of methane. As both methane and H2S are the main components in high-sulfur gas, it is essential to understand the molecular mechanism of the solubility reduction in H2S/CH4 mixtures. Molecular dynamics simulations are carried out for the S8, H2S and CH4 mixtures to reproduce the solubility reduction upon methane addition, and then used to reveal the reduction mechanism at the level of intermolecular interaction. The simulations reveal that both the strong competitiveness and high collision probability of H2S–CH4 pairs reduce the average densities of H2S–S(S8) and H2S–H2S pairs, which reduce the sulfur solubility in a direct/indirect but cooperative way. The role of methane in the solubility reduction is then discussed and the molecular mechanism of sulfur dissolution and precipitation in the sour gasses is addressed.

Experimental study on the degree and damage-control mechanisms of fuzzy-ball-induced damage in single and multi-layer commingled tight reservoirs

Fuzzy-ball working fluids (FBWFs) have been successfully applied in different development phases of tight reservoirs. Field reports revealed that FBWFs satisfactorily met all the operational and reservoir damage control requirements during their application. However, the damage-control mechanisms and degree of formation damage caused by fuzzy-ball fluids have not been investigated in lab-scale studies so far. In this study, the degree of fuzzy-ball-induced damage in single-and double-layer reservoirs was evaluated through core flooding experiments that were based on permeability and flow rate indexes. Additionally, its damage mechanisms were observed via scanning electron microscope and energy-dispersive spectroscopy tests. The results show that: (1) For single-layer reservoirs, the FBWF induced weak damage on coals and medium-to-weak damage on sandstones, and the difference of the damage in permeability or flow rate index on coals and sandstones is below 1%. Moreover, the minimum permeability recovery rate was above 66%. (2) For double-layer commingled reservoirs, the flow rate index revealed weak damage and the overall damage in double-layer was lower than the single-layer reservoirs. (3) There is no significant alteration in the microscopic structure of fuzzy-ball saturated cores with no evidence of fines migration. The dissolution of lead and sulfur occurred in coal samples, while tellurium in sandstone, aluminum, and magnesium in carbonate. However, the precipitation of aluminum, magnesium, and sodium occurred in sandstone but no precipitates found in coal and carbonate. The temporal plugging and dispersion characteristics of the FBWFs enable the generation of reservoir protection layers that will minimize formation damage due to solid and fluid invasion.

Coupling of Oxygen Vacancies and Heterostructure on Fe3 O4 via an Anion Doping Strategy to Boost Catalytic Activity for Lithium-Sulfur Batteries.

The sluggish reaction kinetics and severe shutting behaviors of sulfur cathodes are the major roadblocks to realizing the practical application of lithium-sulfur (Li-S) batteries and need to be solved through designing/constructing rational sulfur hosts. Herein, an effective alternative material of Fe3 O4- x /FeP in-situ embedded in N-doped carbon-tube (Fe3 O4- x /FeP/NCT) is proposed. In this fabricated heterostructure, NCT skeleton works as a sulfur host provides physical barrier for lithium polysulfides (LiPSs), while Fe3 O4- x /FeP heterostructure with abundant oxygen vacancies provides double active centers to simultaneously accelerate e- /Li+ diffusion/transport kinetics and catalysis for LiPSs. Through the respective advantages, Fe3 O4- x /FeP/NCT exhibits synergy enhancement effect for restraining sulfur dissolution and enhancing its conversion kinetics. Furthermore, the promoted ion diffusion kinetics, enhanced electrical conductivity, and increased active sites of Fe3 O4- x /FeP/NCT are enabled by oxygen vacancies as well as the heterogeneous interfacial contact, which is clearly confirmed by experimental and first-principles calculations. By virtue of these superiorities, the constructed cathode shows excellent long-term cycling stability and a high-rate capability up to 10 C. Specially, a high areal capacity of 7.2 mAh cm-2 is also achieved, holding great promise for utilization in advanced Li-S batteries in the future.

Influence of impurities contained in fuel and air on sulfide corrosion of turbine blades of the gas turbine engine

In the process of improving gas turbine engines (GTE), increasing the resource and efficiency, there is a constant increase in temperature and pressure of the working fluid. Turbine elements are subjected to high thermomechanical loads and continuous exposure from the aggressive environment. These impacts are especially significant for the working blades of the first stages of the turbine, located in the area of the highest temperatures. One of the most serious types of damage in this case is the corrosive effect on the working blade from the combustion gases entering the flow part of the turbine. The TS-1 fuel used on an aircraft contains sulfur compounds in its composition – elemental sulfur and mercaptans, which in the combustion process, together with sodium and potassium in the air, leads to an aggressive effect on the material of the turbine blade. To ensure the long-term operation of the turbine blades of the turbine at the gas temperature at the turbine inlet up to 800...850 ℃, the content of these products in both fuel and air is limited according to the regulatory and technical documentation. However, it is not yet possible to exclude them completely. The presence of sulfur compounds on the turbine blades of the GTE causes sulfide corrosion. Therefore, the article considers the influence of impurities in fuel and air on the process of sulfide corrosion of the turbine blades material of the turbine. The mechanism of sulfur dissolution in metal oxides or protective coating is presented, as well as the diffusion of sulfur oxide from the coating surface into its depth. The reason for the influence of sodium chloride contained in the air on the corrosion of nickel alloy or the protective coating applied on it has been established. The influence of vanadium in the fuel on the corrosion rate is given. In order to increase the efficiency of the turbine blades when exposed to such an aggressive environment, it is proposed to use a new coating formed from an aqueous suspension and allowing the introduction of chromium into the coating, which provides a higher durability of such a coating in comparison with serial aluminide coatings. The introduction of chromium is ensured by an exothermic reaction occurring during the formation of the coating during heat treatment.

Solubility and dissolution kinetics of sulfur and sulfides in electrolyte solvents for lithium-sulfur and sodium-sulfur batteries.

In this study, we monitor the dissolution of sulfur and sulfides in electrolyte solvents for lithium-sulfur (Li-S) and sodium-sulfur (Na-S) batteries. The first aim of this research is to assemble a comprehensive set of data on solubilities and dissolution kinetics that may be used in the simulation of battery cycling. The investigation also offers important insights to address key bottlenecks in the development and commercialization of metal-sulfur batteries, including the incomplete dissolution of sulfur in discharge and insoluble low-order sulfides in charge, the probability of shuttling of soluble polysulfides, and the pausing of the redox reactions in precipitated low order sulfides depending on their degree of solid state. The tested materials include sulfur, lithium sulfides Li2Sx, x = 1, 2, 4, 6, and 8, and sodium sulfides Na2Sx, x = 1, 2, 3, 4, 6, and 8, dissolved in two alternative electrolyte solvents: DOL:DME 1:1 v/v and TEGDME. The determined properties of the solute dissolution in the solvent include saturation concentration, mass transfer coefficient, and diffusion coefficient of the solvent in the solid solute. In general, the DOL:DME system offers high solubility in Li-S batteries and TEGDME offers the highest solubility in Na-S batteries. Low solubility sulfides are Li2S2 and Li2S for the Li-S batteries, and Na2S3, Na2S2, and Na2S for the Na-S batteries. However, it is noted that Na2S3 dissolves fast in TEGDME and also TEGDME diffuses fast into Na2S3, offering the possibility of a swollen Na2S3 structure in which Na+ ions might diffuse and continue the redox reactions in a semisolid state.

Insights into the distribution characteristic changes of leaching solution in the gap between chalcopyrite and passivation layer with polyvinyl pyrrolidone: A molecular view

The passivation layer was proven to be an inevitable factor that prevents chalcopyrite leaching. Sulfur and jarosite are the commonly investigated substances in passivation layer research. In this study, the distribution characteristics of leaching solution in the gap between chalcopyrite and jarosite and between chalcopyrite and sulfur were investigated deeply at a molecular level. And the equilibrium distribution configurations were calculated. When polyvinyl pyrrolidone (PVP) was added, a significant layer formed near chalcopyrite. It prevented the accumulation of SO42− and thus prevent the formation of the passivation layer near chalcopyrite. Additionally, the increased diffusion coefficient of H2O molecules indicated the increased permeability and mobility of the leaching solution between chalcopyrite and passivation layer by PVP. Moreover, the increased diffusion coefficients of SO42− between chalcopyrite and sulfur referred to the enhanced dissolution of sulfur. Thus, chalcopyrite leaching was enhanced by PVP. The results provide a new view for the deep understanding of the enhancement mechanism of surfactants in chalcopyrite hydrometallurgy.