Monoclinic Sulfur Research Articles

Ex‐Situ Raman Microscopic Investigation of the High‐Order Polysulfide Restriction of Encapsulated Sulfur Nanowires

Lithium-sulfur (Li−S) batteries are attracting significant research attention because of their high theoretical energy density (2500 Wh kg−1) and excellent economic feasibility. However, commercialization has proven difficult owing to their low electronic conductivity and the dissolution of lithium polysulfide (Li2Sx; x=1–8). In particular, lithium polysulfide dissolution is known to be caused by high-order polysulfide generated at the start of the discharge process. Thus, the control of this factor is important because it determines the electrochemical performance of the cell. In this study, three types of sulfur nanocomposites in the orthorhombic, amorphous, and monoclinic phases, were designed and successfully manufactured. The mechanism of polysulfide generation was confirmed to differ according to the location of sulfur on the carbon matrix (inner pores and surfaces) and allotropic form of sulfur (S4–S8) via electrochemical tests. Furthermore, the electrochemical reaction mechanism was identified by tracing the lithium polysulfide species according to the reaction region using ex-situ Raman spectroscopy. In this research, suppression of the high-order polysulfide generation reaction by controlling the monoclinic sulfur was represented by a single plateau galvanostatic curve, suggesting a clear strategy for maximizing cycle stability in next-generation Li−S batteries

A non-confined gamma monoclinic sulfur cathode in carbonate electrolyte based room temperature K–S batteries

This work extends our novel monoclinic γ-sulfur approach of polysulfide mitigation to the K–S chemistry. The lack of soluble polysulfides enable extremely stable cycling to 500 cycles in carbonate electrolyte.

Phase transition process of sulfur in bitumen and its effect on rheological properties of bitumen

Partial substitution of sulfur for bitumen helps reduce bitumen consumption while promoting recycling of the sulfur in waste residues. The properties of sulfur-extended bitumen (SEB) are closely related to the chemical reaction process and the phase transition process of sulfur in bitumen, and these two processes are influenced by sulfur dosage and curing time. Therefore, SEB samples with sulfur dosages of 1 %, 5 %, 10 %, 15 %, 20 %, 25 % and 30 % were prepared and cured for 0, 15, 30, or 60 days. Differential scanning calorimetry was conducted to understand the sulfur recrystallization process in bitumen, and a dynamic shear rheometer was used to analyze the rheological properties of SEB samples. Results show that molten sulfur can turn to monoclinic sulfur immediately after cooling; the monoclinic sulfur gradually turns to orthorhombic sulfur, and the ratio between the two forms stabilizes after curing for 15 days. The recrystallization of sulfur in bitumen needs sufficient curing time, and the sulfur states in bitumen vary depending on the sulfur dosage. When the sulfur dosage is lower than 15 %, sulfur dissolves into bitumen. The dissolved sulfur softens the bitumen and increases its low-temperature properties and resistance to fatigue cracking. When the sulfur dosage is 10 %, 15 %, 20 %, 25 %, or 30 %, surplus sulfur is recrystallized to orthorhombic sulfur. When the sulfur dosage is 35 % or more (the dosages evaluated in the former study), surplus sulfur is recrystallized to monoclinic sulfur. The chemically crosslinked sulfur and recrystallization sulfur help increase the elastic component in bitumen and improve the rutting resistance and fatigue life of bitumen. However, when the sulfur dosage exceeds 20 %, the effect of stress concentration stands out due to bulk gathering of recrystallized sulfur, and this effect stops further improvement in the fatigue life of SEB samples. The effects of recrystallization sulfur on bitumen are mainly concentrated in the first 15 days of curing time, even though much more recrystallized sulfur is detected after more curing time, even at 60 days (the longest curing time evaluated in this study). Therefore, a curing time of 15 days is sufficient for accurate evaluation of SEB properties.

Study of Thermodynamic Properties of Monoclinic Sulfur (Sβ) Under High Pressure Using Three Different Equations of State for the Treatment Scabies in Dermatology

Thermodynamic properties of monoclinic β-sulfur Sβ under high pressure up to 20 Gpa have been studied, where Orthorhombic α-sulfur Sα changes to Sβ at 94.4℃. The high pressure technology used to tackle the crystallization volume of sulfur Sβ without changes in the chemical properties. Sulfur Sβ can be used after the effect of high pressure in the development of the medicine used to treat scabies. The present study is performed to calculate the effects of high pressure on some important physical properties of the material such as (bulk modulus (B), compression volume ratio (VP/Vo), Grüneisen parameter ), Debye temperature (θD) and phonon frequency spectrum (pfs). Three different equations of state EOS's (Birch- Murnaghan EOS, Vinet EOS and modified Lennard-Jones EOS) were implemented to analyze pressure-volume relationship and then combining calculated data with various expressions of volume dependence of the other thermodynamic properties that are; Bulk modulus, Grüneisen parameter, Debye temperature and phonon frequency spectrum. The behavior of any of these concepts were described in different figures. It was found that, relative volume, and Grüneisen parameter were decreased with high pressure, while the other considered parameters; Bulk modulus, Debye temperature and phonon frequency spectrum were expected to increase as a high pressure is applied.

Stabilization of gamma sulfur at room temperature to enable the use of carbonate electrolyte in Li-S batteries

This past decade has seen extensive research in lithium-sulfur batteries with exemplary works mitigating the notorious polysulfide shuttling. However, these works utilize ether electrolytes that are highly volatile severely hindering their practicality. Here, we stabilize a rare monoclinic γ-sulfur phase within carbon nanofibers that enables successful operation of Lithium-Sulfur (Li-S) batteries in carbonate electrolyte for 4000 cycles. Carbonates are known to adversely react with the intermediate polysulfides and shut down Li-S batteries in first discharge. Through electrochemical characterization and post-mortem spectroscopy/ microscopy studies on cycled cells, we demonstrate an altered redox mechanism in our cells that reversibly converts monoclinic sulfur to Li2S without the formation of intermediate polysulfides for the entire range of 4000 cycles. To the best of our knowledge, this is the first study to report the synthesis of stable γ-sulfur and its application in Li-S batteries. We hope that this striking discovery of solid-to-solid reaction will trigger new fundamental and applied research in carbonate electrolyte Li-S batteries.

Carbon consumption and adsorption-regeneration of H2S on activated carbon for coke oven flue gas purification.

Carbon consumption of activated carbon varies with sulfur-containing products. In this work, differential thermogravimetric (DTG), electron paramagnetic resonance (ESR), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD) we re used to reveal the adsorption-regeneration process of H2S and the effect of adsorption products on carbon consumption. The results show that H2S reacts with the C=C bond to form the C-S bond as an intermediate state, followed by the formation of elemental sulfur. It directly sublimates at approximately 380 °C, about 30 °C higher than the decomposition temperature of H2SO4. In the thermal regeneration process, the elemental sulfur in the form of monoclinic sulfur (S8) first breaks into infinitely long chain molecules (S∞) and then into small molecules, finally into sulfur vapor. The desorption of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H2SO4; moreover, the compressive strength reduces less due to its slight effect on the disordered graphitic structure. H2S also reacts with the C=O bond to form H2SO3 or H2SO4. The desorption of H2SO3 does not require carbon consumption. The decomposition of H2SO4 needs to react with the C=C bond to release SO2, CO2, and CO, and the compressive strength of activated carbon significantly decreases. The carbon consumption originates from two aspects; the one from the regeneration of sulfur-containing products is more than twice the other one from the decomposition of oxygen-containing functional groups.

Fluorinated graphene/sulfur hybrid cathode for high energy and high power density lithium primary batteries

It is a great challenge to obtain high performance carbon fluoride (CFx) cathodes with high specific capacity and good rate performance due to the electronic conductivity of CFx being known to decrease with an increase in the specific capacity. Herein, we propose a novel fluorinated graphene (FG)/sulfur hybrid cathode to enhance both the energy density and power density of lithium/carbon fluoride (Li/CFx) batteries. Impressive enhancements of the specific capacity, discharge voltage, and rate capability are demonstrated with the novel FG/sulfur hybrid cathode. In comparison with the pristine FG cathode, the hybrid cathode exhibits higher electrochemical activity, lower overpotential, and faster ion transfer over the main discharge range. Furthermore, when the melt-diffusion method is used to prepare the hybrid cathode, the uncommon monoclinic sulfur is presented under ambient temperature. A significant synergistic effect which reduces the reaction resistance effectively is demonstrated with the presence of monoclinic sulfur, leading to the highest energy density of 2341 W h kg−1 and a power density up to 13 621 W kg−1 at 8.0 A g−1. Our results are expected to introduce a new generation of high energy and high power density lithium primary cells, based on a simple and effective strategy employing FG/S hybrid cathodes.

Paragenesis BN/CNTs hybrid as a monoclinic sulfur host for high rate and ultra-long life lithium–sulfur battery

A paragenesis BN/CNT hybrid was prepared via a one-step co-pyrolysis method. Used as a sulfur host for Li–S batteries, the cathode exhibits high active-sulfur utilization, superior cycling stability and excellent rate capability.

Preparation and physicochemical characterization of ingredients of Indian traditional medicine, Mahamrutyunjaya Rasa

BackgroundMahamrutyunjaya rasa is an ayurvedic formulation used in the treatment of cardiac disorders. It contains the purified roots of Visa (Aconitum ferox), Brihati (Solanum indicum), fruits of Pippali Kana (Piper longum), Marica (Piper nigrum), Gandhaka (Sulfur), Hingula (Cinnabar) and Tankana (Sodium metaborate) as per Bhaishajya Ratnavali. The purification (shodhana) process changes the physiochemical properties of the raw materials which need to be studied and understood. ObjectiveThe present work aims to perform a comprehensive physicochemical characterization of raw materials, intermediates and the final product obtained during purification, using modern analytical techniques. Materials and methodsThe standard methods as per traditional text were followed and the physicochemical changes were also investigated by collecting samples at different steps of purification. The samples were analysed using various techniques, viz. Fourier transform infra-red spectroscopic (FTIR), X-ray diffraction (XRD), Differential Scanning Calorimeter (DSC) and High Performance thin Layer chromatography (HPTLC). ResultsThe FTIR and HPTLC analysis of the alkaloidal extracts of Visa showed loss of an ester group with shift in the peaks from 1720 cm−1 (CO stretching of esters) to 1676 cm−1 (CO stretching of Ketone) which signifies the conversion of alkaloid Aconitine (LD50 – 0.08 mg/kg) to Benzoylaconine (LD50 – 24 mg/kg) improving its safety. The analysis of gandhaka by XRD and DSC showed that purification brought about transformation of orthorhombic sulphur into monoclinic sulphur and it reverted back to original form with higher purity. The treatments given to gandhaka and hingula with organic compounds made them homologous to the body tissues. Analysis of purified tankana showed that the processing led to loss of water and slight change in the crystal structure with the shift in the endothermic peak from 110.6 °C to 104.2 °C. ConclusionThus, the present study provides a scientific backing to the methodologies used by Ayurvedic practitioners. The study also provides physicochemical fingerprints for the standardization as well as characterization of raw materials and forms a technical platform for manufacturers to develop quality control standards.

Monoclinic sulfur cathode utilizing carbon for high-performance lithium–sulfur batteries

Abstract Sulfur cathodes for lithium–sulfur batteries have been designed to be combined with conductive carbon because the insulating nature of sulfur causes low active material utilization and poor rate capability. This paper is the first to report that carbon can induce a phase transition in a sulfur cathode. The stable form of a sulfur crystal at ambient temperature is orthorhombic sulfur. We found that monoclinic sulfur becomes more stable than orthorhombic sulfur if carbon atoms penetrate into the sulfur at elevated temperatures and the carbon density exceeds a threshold of C 0.3 S 8 . The high stability of the carbon-containing monoclinic sulfur persists during lithiation and is attributed to locally formed linear SC 3 S chains with marked stability. This study provides a novel perspective on the role of carbon in the sulfur cathode and suggests control of the crystal phase of electrodes by composite elements as a new way of designing efficient electrode materials.

Clogging of water supply wells in alluvial aquifers by mineral incrustations, central Serbia

The formation of incrustations on public water supply well screens reduces their performance considerably. The incrustations increase hydraulic losses, reduce the capacity of the well and screen, affect the quality of the pumped water and increase maintenance costs. In alluvial environments, the most common deposits are iron and manganese hydroxides. However, the rates of formation, compositions and levels of crystallization vary, depending on the geochemical characteristics of the alluvial environment, the microbiological characteristics of the groundwater and the abstraction method. Samples of 15 incrustations were collected from wells that tap shallow alluvial aquifers and were found to be dominated by iron. XRD analyses detected low-crystalline ferrihydrite and manganese hydroxide in the samples collected from the water supply source at Trnovce (Velika Morava alluvial). The incrustations from the Belgrade Groundwater Source revealed the presence of ferrihydrite and a substantial amount of goethite ?-FeOOH. Apart from goethite, greigite (Fe3S4) was detected in three samples, while one sample additionally contained bernalite Fe(OH)3 and monoclinic sulfur S8. Among carbonates, only siderite was detected. Iron oxidizing bacteria generally catalyze deposition processes in wells, while sulfate reducing bacteria (SRB) play a role in the biogenic formation of greigite. Determining the nature of the deposited material allows better selection of rehabilitation chemicals and procedure.

ChemInform Abstract: Encapsulated Monoclinic Sulfur for Stable Cycling of Li—S Rechargeable Batteries.

AbstractAn encapsulated sulfur electrode for Li—S rechargeable batteries consisting of well aligned monoclinic sulfur nanowires completely covered by a minimal amount of carbon shows excellent electrical performance.

Batteries: Encapsulated Monoclinic Sulfur for Stable Cycling of Li–S Rechargeable Batteries (Adv. Mater. 45/2013)

On page 6547 Do Kyung Kim, Jang Wook Choi and co-workers describe a highly aligned and carbon-encapsulated sulfur cathode synthesized with an AAO template that exhibits a high and long cycle life, and the best rate capability based on the complete encapsulation of sulfur (physical) and implementation of the monoclinic sulfur phase (chemical).

Encapsulated Monoclinic Sulfur for Stable Cycling of Li–S Rechargeable Batteries

Monoclinic S8 , an uncommon allotrope of sulfur at room temperature, can be formed when common orthorhombic S8 is heat-treated under enclosed environments in nanometer dimensions. Monoclinic S8 prevents the formation of soluble polysulfides during battery operation, resulting in unprecedented cycling performance over 1000 cycles under the highest sulfur content to date.

Colloidal stability and coagulation kinetics study of different sized sulphur nanoparticles

Colloidal stability and coagulation kinetics of orthorhombic and monoclinic sulphur nanoparticles (SNPs) were determined in terms of their size distribution along a gradient of temperature, dilution and time-drive. Dynamic light scattering (DLS) was used to determine the size and shape of SNPs in the colloidal suspension. A simultaneous study with high-resolution scanning and transmission electron microscopy was undertaken to evaluate the shape and actual (core) size of SNPs. All the DLS-derived data were statistically analysed to determine the effect of temperature, dilution and time drive on the growth kinetics of SNPs in the colloidal medium. Polymer-stabilised orthorhombic (∼10 nm) and monoclinic (∼15 nm) SNPs were found to be highly stable in the variable range of physical conditions and validates their active use in antimicrobial drug formulations.

Evaluation of physicochemical properties, and antimicrobial efficacy of monoclinic sulfur-nanocolloid

Stable nanocolloids of monoclinic sulfur (β-SNPs) were prepared through ‘water-in-oil microemulsion technique’ at room temperature after suitable modifications of the surface. The morphology (rod shaped; ~50 nm in diameter) and allotropic nature (monoclinic) of the SNPs were investigated with Transmission Electron Microscopy and X-ray Diffraction technique. The surface modification, colloidal stability, and surface topology of β-SNPs were evaluated with Fourier Transform Infrared Spectroscopy, zeta potential analysis, and Atomic Force Microscopy. Thermal decomposition pattern of these nanosized particles was determined by Thermo Gravimetric Analysis (TGA). β-SNPs-colloids expressed excellent antimicrobial activities against a series of fungal and bacterial isolates with prominent deformities at their surface. In contrast, insignificant cytotoxicity was achieved against the human derived hepatoma (HepG2) cell line upon treatment with β-SNPs. A simultaneous study was performed to determine the stock concentration of β-SNP-colloids using a novel high phase liquid chromatographic method. Cumulative results of this study hence, elucidate the stabilization of nanosized monoclinic sulfur at room temperature and their potential antimicrobial efficacy over micron-sized sulfur.

A new and simple method for sulfur nanoparticles synthesis

Sulfur nanoparticles were successfully synthesized via novel water-in-oil microemulsion system. The microemulsion system contained cyclohexane as an oil phase, Triton X-100 as a surfactant, butanol as a co-surfactant and sodium polysulfide solution or hydrochloric acid solution as aqueous phase, respectively. The sulfur nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. The results showed that the as-prepared monoclinic sulfur nanoparticles exhibited high purity and spherical shape with an average size of about 22 nm.

Geometric analysis of the models of sulfur (S8) x molecular nanoclusters in computer experiment

A version of a computer nanoscope is proposed for single crystals with the known atomic structure for a detailed analysis of surface coordination bonds forming on nanosized nuclei due to the intermolecular interaction. Different stages of the study of rhombic and monoclinic sulfur (from the atomic/molecular structure on the first stage to the model packing growth polyhedra on the final stage) are analyzed. The calculation results of the coordination numerical sequences revealed in the computer experiment when the coordination spheres are filled with S8 molecules with the formation of rather large molecular clusters with a size of about 10 nm or more are presented.

Reductive Precipitation of Elemental Selenium from Selenious Acidic Solutions Using Sodium Dithionite

In this work, the batch-reactor reduction of selenious acid (H2SeO3) species with sodium dithionite (Na2S2O4) from weakly acidic sulfate solutions containing 300 mg/L of selenium at 23 οC was studied. The results showed that, at an initial pH value of 3, <0.5 μg/L of selenium(IV) remained in solution after reduction. The reductive precipitation reaction started as soon as dithionite was added in the selenium-bearing solution and was completed within less than a minute. However, it was determined that the precipitate was not stable in the presence of the dithionite decomposition byproduct and partially redissolved after several hours. The reaction product, characterized using X-ray diffraction, scanning electron microscopy, and chemical analysis, was determined to be red amorphous selenium. The precipitate, in addition to elemental selenium, was determined to contain monoclinic sulfur that was apparently formed via a side reaction pathway involving the decomp...

Electrochemical desulfurization of geothermal fluids under high temperature and pressure

Electrochemical removal of sulfide ions was achieved in salt water using graphite anodes in an autoclave under high temperatures and pressures, simulating geothermal fluids. The reaction products were characterized using microscopy and X-ray photoelectron spectroscopy (XPS). At low temperatures the reaction rate is quite small. It decreases rapidly with time down to a negligibly small value, which increases only slightly with temperature. The reaction produces elemental sulfur, which was seen under the microscope and identified using XPS. It passivates the electrode and hence diminishes its activity. Above about 115 °C, much higher removal rates can be sustained for much longer times, while the increase of temperature has a much stronger effect on the reaction rate. Under this condition, elemental sulfur was no longer detected among the reaction products, while the electrode retained its activity for continuous operation. The XPS spectra at high temperatures reveal the presence of oxygen bearing sulfur species, such as sulfates. The melting of sulfur (at 115 °C) has a much stronger effect on the efficiency of the process than the transition of orthorhombic to monoclinic sulfur (at 95 °C). A Clausius-Clapeyron’s analysis reveals that the melting point of sulfur inside the autoclave is nearly equal to its normal melting point.