Range Of Carbon Concentrations Research Articles

Unveiling the mechanism of the carbon ordering and martensite tetragonality in Fe–C alloys studied via deep-potential molecular dynamics simulations

The martensitic transformation plays a pivotal role in the strengthening and hardening of steels, yet an accurate interatomic potential for a comprehensive description of the martensitic phase formation in Fe–C alloys is lacking. Herein, we develop a deep learning-based interatomic potential to perform molecular dynamics (MD) simulations to study the martensitic phase transformation across a range of carbon (C) concentrations. The results reveal that an increased C concentration leads to a suppression of phase boundary movement and a deceleration of the phase transformation rate. To overcome the timescale limitations inherent in MD simulations, metadynamics sampling was employed to accelerate the simulations of C diffusion. We find that C atoms tend to cluster at distances equivalent to the lattice parameter of Fe with the same sublattice occupation, leading to local lattice tetragonality. Such C-ordered structures effectively inhibit dislocation movement and enhance strength. The stress field induced by dislocations facilitates a higher degree of ordering. The formation of C-ordered structures is identified as a potentially crucial strengthening mechanism for martensitic steels. The consistency between our simulation results and reported experimental observations underscores the effectiveness of the developed DP model in simulating martensitic phase transformation in Fe–C alloys, providing detailed insights into the mechanisms underlying this process.

Comparison of cation exchange capacity extraction methods for soil data harmonization and soil classification in Central and East Europe

Cation exchange capacity and base saturation are of crucial importance for soil characterisation and classification; however, the interchangeability of soil data for international assessment of soil productivity, soil classification, mapping, and modelling is limited due to the lacking comparisons between results obtained using different analytical methods in particular regions of the world. The aim of the present study was to analyse the relationships between cation exchange capacity and base saturation measured using the methods adopted in Central and East Europe, and ‘standard’ techniques required for soil classification suggested by World Reference Base (WRB). This study was carried out using 183 soil samples collected from Luvisols, Retisols, Planosols, Chernozems, Phaeozems, Cambisols, and Arenosols in Poland, representing a wide range of texture, pH, and organic carbon content. A close comparability was found in noncalcareous soils between the ‘total sorption capacity’ (T) measured in Central and East Europe as the sum of base cations and ‘total’ (‘hydrolytic’) acidity, with the ‘standard’ cation exchange capacity (CEC) measured using 1 M ammonium acetate buffered at pH 7. The close correlation between T and CEC values (in noncalcareous soils) facilitates reliable data recalculation and its application in global modelling, soil classification and mapping. For soils containing carbonates, CEC must be measured using reference methods, because no relationship exists between T and CEC. The ‘potential’ base saturation (V) derived on the basis of T may be reliably recalculated to ‘standard’ base saturation (BS), allowing a retrieval of archival data from Central and East European regional databases and published reports. Similarities between the values of cation exchange capacity and base saturation, whether measured or calculated using the local and standard methods, allow a positive verification of previously proposed correlations between the local soil taxa and the reference soil groups of the WRB classification and soil orders defined by USDA Soil Taxonomy. The pH values corresponding to 50 % of ‘standard’, ‘potential’, and ‘effective’ base saturation were estimated at 5.5, 5.2, and 4.8, respectively. Irrespective of the differences between current estimates and previously reported pH threshold values corresponding to 50 % base saturation, the obtained results confirm that field measurements of soil pH may be considered a substitute for laboratory-measured base saturation for some purposes, such as soil classification.

A generalized adsorption model of CO2-CH4 in shale based on the improved Langmuir model

CO2 enhanced shale gas recovery (CO2-ESGR), as one of the most promising carbon capture, utilization and storage (CCUS) technologies, can both improve the shale gas production for clean energy supply and mitigate greenhouse gas emissions for the goal of carbon neutrality. The adsorption characteristics of CO2 and CH4 in shale play a key role in the reserve assessment of shale gas and the implementation of CO2-ESGR. The problem of accurate prediction of the adsorption and competitive adsorption characteristics of CO2 and CH4 in shale is still one of the main challenges for CO2-ESGR. To bridge the gap, this work developed a generalized prediction model for the adsorption properties of CH4, CO2, and their mixed gas in shale by improving the Langmuir model, covering a large range of temperature, pressure, and total organic carbon content (TOC). The mathematical models for the key parameters of the Langmuir model, the saturated adsorption capacity Q0 and Langmuir pressure PL, were built for the single-component gas based on their functional relationship with temperature and TOC, and for the mixed gas based on their relationship with Q0 and PL of the single-component gas and CO2 content. Then an improved Langmuir model for the adsorption properties of CO2-CH4 in shale was established. The accuracy of the improved model was verified with a relative deviation below 5 % in a large range of temperature (303–363 K), pressure (0–15 MPa) and TOC (1.06 %-3.83 %) by comparing the calculated adsorption with the experimental data. This generalized adsorption model not only ensures the prediction accuracy of CO2-CH4 adsorption characteristics in shale but also expands its application convenience in a large range of temperatures, pressures and TOC, providing a certain theoretical basis for CO2-ESGR technology.

Derivation of site-specific environmental quality guideline values for fuel-contaminated soils on sub-Antarctic Macquarie Island.

Accidental fuel spills associated with the storage, transfer, and use of diesel fuel for power generation have occurred on sub-Antarctic Macquarie Island since the establishment of the island's research station in 1948. An extensive in situ remediation program was implemented by the Australian government from 2009 to 2016 that used nutrient addition and air sparging to enhance the microbial degradation of petroleum products. During this period, a range of ecotoxicological assessments were conducted to better understand the impacts of fuel in soils on native biota and their sensitivity. This study compiles this ecotoxicological data into a species sensitivity distribution (SSD) to establish environmental quality guideline values (EQGVs) for fuels in soils on Macquarie Island. The SSD model includes 13 critical effect concentrations (CECs) selected using an expert judgment approach. These include data from functional and community-based tests as well as traditional single-species toxicity tests using microbes, plants, and invertebrates and representing the range of carbon content (~3%-48%) and fuel composition at various stages of degradation (from fresh to 18 months aged) in soils as occurs at contaminated sites on the island. A protective concentration (PC80) of 97 mg/kg TPH C9-C40 (95% CI 24-283) was derived for special Antarctic blend diesel from the SSD and is recommended as an appropriate site-specific EQGV and potential remediation target for the immediate station area in the vicinity of infrastructure. More conservative PC values are also provided for areas with higher conservation values outside the station footprint. These EQGVs are the first to be produced for fuels in the sub-Antarctic and Antarctic regions. They will be used to inform ongoing environmental management on Macquarie Island and are likely suitable and recommended for use more broadly across the sub-Antarctic. Integr Environ Assess Manag 2024;00:1-13. © 2024 Commonwealth of Australia. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Seven white dwarfs with circumstellar gas discs II: tracing the composition of exoplanetary building blocks

ABSTRACT This second paper presents an in-depth analysis of the composition of the planetary material that has been accreted on to seven white dwarfs with circumstellar dust and gas emission discs with abundances reported in Rogers et al. The white dwarfs are accreting planetary bodies with a wide range of oxygen, carbon, and sulphur volatile contents, including one white dwarf that shows the most enhanced sulphur abundance seen to date. Three white dwarfs show tentative evidence (2–3$\sigma$) of accreting oxygen-rich material, potentially from water-rich bodies, whilst two others are accreting dry, rocky material. One white dwarf is accreting a mantle-rich fragment of a larger differentiated body, whilst two white dwarfs show an enhancement in their iron abundance and could be accreting core-rich fragments. Whilst most planetary material accreted by white dwarfs display chondritic or bulk Earth-like compositions, these observations demonstrate that core-mantle differentiation, disruptive collisions, and the accretion of core-mantle differentiated material are important. Less than 1 per cent of polluted white dwarfs host both observable circumstellar gas and dust. It is unknown whether these systems are experiencing an early phase in the disruption and accretion of planetary bodies, or alternatively if they are accreting larger planetary bodies. From this work there is no substantial evidence for significant differences in the accreted refractory abundance ratios for those white dwarfs with or without circumstellar gas, but there is tentative evidence for those with circumstellar gas discs to be accreting more water rich material which may suggest that volatiles accrete earlier in a gas-rich phase.

Sorption of colored vs. noncolored organic matter by tidal marsh soils

Abstract. Tidal marshes are significant sources of colored (or chromophoric) dissolved organic carbon (CDOC) to adjacent waters and, as a result, contribute substantially to their optical complexity and ultimately affect their water quality. Despite this, our mechanistic understanding of the processes that regulate the exchange and transformation of CDOC at the tidal marsh–estuarine interface remains limited. We hypothesized that tidal marsh soils regulate this exchange and transformation subject to soil mineralogy and salinity environment. To test this hypothesis, we generated initial mass sorption isotherms of CDOC and noncolored dissolved organic carbon (NCDOC) using anaerobic batch incubations of Great Dismal Swamp DOC with four tidal wetland soils, representing a range of organic carbon content (1.77 ± 0.12 % to 36.2 ± 2.2 %) and across four salinity treatments (0, 10, 20, and 35). CDOC sorption followed Langmuir isotherms that were similar in shape to those of total DOC, but with greater maximum sorption capacity and lower binding affinity. Like isotherms of total DOC, CDOC maximum sorption capacity increased and binding affinity decreased with greater salinity. Initial natively adsorbed colored organic carbon was low and increased with soil organic content. In contrast, NCDOC desorbed under all conditions with desorption increasing linearly with initial CDOC concentration. This suggests that for our test solutions CDOC displaced NCDOC on tidal marsh soils. Parallel factor analysis of 3-D excitation emission matrices and specific ultraviolet absorbance measurements suggested that CDOC sorption was driven primarily by the exchange of highly aromatic humic-like CDOC. Taken together, these results suggest that tidal marsh soils regulate export and composition of CDOC depending on the complex interplay between soil mineralogy, water salinity, and CDOC vs. NCDOC composition.

Facile synthesis of high entropy carbide-nickel based cermets by in-situ carbo-thermal reduction of transition metal oxides

Equimolar and non-equimolar high entropy carbide-nickel based cermets were successfully prepared by in-situ carbo-thermal reduction of constituent metal oxides in a single pressureless vacuum sintering cycle at 1420°C. The carbon content in quinary (Ti0.2V0.2Nb0.2Ta0.2W0.2)Cx-10wt.%Ni and senary (Ti0.2V0.2Nb0.2Ta0.2W0.1Mo0.1)Cx-10wt.% Ni high entropy carbide cermets was varied (x = 0.6–1.0). Two-phase HEC-Ni cermets were formed at x = 0.75–0.85, whereas M6C (η-phase) and graphite phase coexisted at lower and higher carbon contents (x = 0.6, 0.9 and 1.0) in both HEC 5 and HEC 6 systems. In HEC 5, submicrometric WC precipitates were observed, which were attributed to the limited solubility of hexagonal-WC within the in-situ formed HEC 5 phase, contrasting with HEC 6 where no such precipitations were formed across the entire carbon content range. The partial replacement of W with Mo in the (Ti0.2V0.2Nb0.2Ta0.2W0.1Mo0.1)Cx-10 wt% Ni cermets promoted solid solution formation at lower temperature, and the grain size and hardness decreased and the fracture toughness increased. Both HEC-Ni cermets showed a homogeneous distribution of elements within the carbide phase, resulting in (HV30) hardness around 16 GPa and a fracture toughness around 8 MPa.m1/2. The phase evolution was systematically investigated by interrupting the sintering cycle at 600–1400 °C, employing XRD analysis. Thermodynamic calculations were performed to predict the critical reaction temperatures for carbo-thermal reduction. To evaluate the intrinsic mechanical properties of each phase and establish the correlation with microstructural features, micromechanical mapping was performed utilizing the high-speed nano-indentation technique.

Predicting organic carbon in European soils: Only in Southern Ukraine can we expect an increase in humus content

Soil organic carbon comprises the majority of the terrestrial soil carbon pool and plays an important role in the global carbon cycle and balance. Even minor changes in soil organic carbon (SOC) can have a significant impact, not only on climate but also on ecosystem stability, due to its key role in soil-atmosphere carbon exchange, plant growth, and food production. In order to assess the feedbacks between the terrestrial carbon cycle and climate change, and to maintain ecosystem functions, it is crucial to understand the spatial and temporal changes in SOC and the drivers of these changes. The role of soil as a source or sink of atmospheric CO2 is primarily influenced by changes in climate and soil water content. Climate change, particularly global warming, can have a direct or indirect impact on the decomposition of organic matter by regulating soil microbes and fauna, enzyme activity, and soil respiration. A warming climate may increase the loss of soil carbon to the atmosphere because warming has a stronger effect on respiration than on photosynthesis, resulting in a positive soil carbon-climate feedback. Climate warming can significantly affect soil organic matter stocks, with the magnitude of the effect largely dependent on the initial organic matter stock size. Soil carbon content is a crucial aspect of terrestrial ecosystems that affects their functional properties and the climate. Conversely, climate also has an impact on soil organic carbon content. The spatial variability of soil organic carbon content and the predictions made for the west-central European region are also important considerations. The study identified the spatial variation of soil organic carbon throughout Europe and forecast its dynamics in the next 50–70 years, considering global climate change. Digital soil mapping enables a more precise representation of soil properties in space, including the spatial quantification of prediction errors. The accuracy of these predictions increases as more local observations, such as soil profiles, are available to construct the prediction model. Digital soil mapping allows flexible spatial development of soil property maps. Soil properties, such as nutrient concentration and stocks, carbon, heavy metals, pH, cation exchange capacity, and physical properties like particle size and bulk density, can be modelled at different depths and spatial resolutions depending on the project's objectives and available input data. The r GSOCmap project used a 1 km grid to model soil organic matter content. In Europe, the range of soil organic carbon content is from 0 to 750 t/ha, with a mean of 78.1 t/ha and a standard deviation of 50.1 t/ha. Climatic factors were found to account for 29% of the variation in soil organic carbon based on regression analysis. The study revealed that an increase in air temperature leads to a decrease in soil organic carbon content, while an increase in precipitation results in an increase in this indicator. Additionally, the content of soil organic matter is negatively impacted by an increase in the seasonality of precipitation. According to the forecast, global climate change will cause an increase of 1.0–1.1 t/ha in the organic carbon content of 3.6% of the continent's area over the next 70 years. On 7.6% of the area, the changes will be insignificant. The soil organic carbon content is expected to decrease on 88.9% of the area. Of this, 35.1% will experience a slight decrease in carbon content by 0–1 t/ha, 28.4% will experience a moderate decrease in soil organic carbon content by 1.0–1.1 t/ha, and 25.3% will experience a significant decrease by 1.1–1.3 t/ha. The Baltic countries, Belarus, and the Black Earth zone of Russia are at the highest risk. The risk of Russia becoming highly dependent on food imports is increased by this fact. The prospects for Ukraine are quite optimistic. Even in the northern Azov region, we can expect an intensification of humus accumulation processes in the near future, mainly due to increased precipitation. Precipitation in southern Ukraine is a limiting factor that significantly affects agricultural productivity. Increased precipitation and organic matter growth in the soil present positive prospects for agriculture in southern Ukraine, including the northern Azov, Black Sea, and Crimea. It is possible that the occupation of these territories, which are promising for agricultural production, is one of the goals of Russian armed aggression against Ukraine.

ENERGY VALUE ASSESSMENT OF SOLID WASTE USING PROXIMATE AND ULTIMATE ANALYSIS OF GOSA DUMPSITE IN IDU, ABUJA

Proximate and Ultimate analysis of a MSW materials collected from Gosa Idu Dump site is herein presented; the variability of a MSW material trace to citizens’ life style and social status reflect the compositions. Municipal solid waste as cited by many others consists of organic materials, leather, plastics, metal/iron, glasses, rubber etc. The research on energy value assessment commenced on the 30th September, 2023 with collection of random samples and instant characterization for a steady duration of seven days. Both proximate and ultimate analysis was used in carrying out the research. Test result on characterization showed MSW exhibiting average percentage composition of organics at 64.43%, Leather 12.21%, plastics 3.36%, and rubber 1.82%. The sampled MSW was subjected to proximate and ultimate analysis to include; moisture content, volatile matter, fixed carbon, ash content, carbon, hydrogen, Nitrogen, sulphur and oxygen which are vital for computation of energy value assessment. The result of both proximate and ultimate analysis showed that the percentage of carbon content range from 35.33 to 46.67%, Hydrogen from 6.91 to 10.55%, Nitrogen from 1.13 to 2.18%, sulphur from 0.72 to 1.62% and Oxygen from 33.25 to 46.68%. The total energy recovered from the MSW sample collected from Gosa is 497,097.75 Kcal/kg depicting the overall energy potential of the Dump site. The research recommend adopting proximate and ultimate analysis as explorations and exploitations technics of energy value assessment of MSW and possibility of setting up a pilot test plant for waste to energy conversion of energy potentials for small scale power generation plant.

Characteristics of MICP- and EICP-treated sands in simple shear conditions: a benchmarking with the critical state of untreated sand

Microbial- or enzyme-induced calcium carbonate (CaCO3) precipitation (MICP and EICP) are relatively new ground improvement techniques. In this study, the mechanical behaviour of biotreated (MICP/EICP) and untreated sands was investigated in light of the critical state soil mechanics framework using a series of direct simple shear (DSS) tests. A wide range of calcium carbonate content (CC), initial void ratio after consolidation (e0) and effective initial normal stress ([Formula: see text]) was considered. The biotreated specimens showed improved shear strength and dilative tendency compared to untreated specimens with similar initial states. The ultimate state (US) for the biotreated sand shifted towards a smaller void ratio (e) than the value of e at the critical state of untreated sand at the same σ′N in e–log σ′N space. Compared to untreated sand, a significantly larger US stress ratio was achieved for the biotreated sand, particularly at high CC and low [Formula: see text]. The characteristic features of undrained behaviour, such as instability stress ratio, stress ratio at phase transformation and flow potential showed good relationships with modified initial state parameter, void ratio after biotreatment and CC. The bonding ratio, (τ/σ′N)bond, was used to quantify the interparticle bonding. The peak value of (τ/σ′N)bond for the biotreated sand was significantly larger than zero, particularly at high CC and low [Formula: see text], while the peak (τ/σ′N)bond for the untreated sand was negligible. It was also observed that the mobilisation and degradation of calcium carbonate bonds in biotreated sand during DSS shearing are influenced by both CC and [Formula: see text].

Hydrogen diffusion and storage in substoichiometric TiC

In this paper we investigate the nature of hydrogen diffusion in substoichiometric TiC using simulations. Specifically, we examine how well connected the carbon structural vacancies are in TiCx using percolation theory and how many structural carbon vacancies are connected to the surface of TiCx. This provides direct insight into the number of sites available for hydrogen storage and the interconnected nature of the carbon vacancy network. We also compute the binding energies and migration energies of hydrogen in TiCx using density functional theory. This is conducted over a range of carbon concentrations from nearly stoichiometric TiC to Ti2C and includes the differences in vacancy ordering. We find that the migration energy of hydrogen in TiCx generally decreases with carbon loss and is associated with the tetrahedral interstices near them but that the binding energy of hydrogen to TiCx is independent of carbon concentration. Furthermore, we show that this migration path can occur through the tetrahedral interstices, which is influenced by local carbon concentration. These results also demonstrate the vacancy ordered R3¯m Ti2C structure does not possess any more superior ability to store or transport hydrogen than the Fd3¯m Ti2C structure.

The importance of carbon to the formation and composition of silicates during mantle metasomatism

Mineral and fluid inclusions in mantle diamonds provide otherwise inaccessible information concerning the nature of mantle metasomatism and the role of fluids in the mass transfer of material through the Earth’s interior. We explore the role of carbon concentration during fluid-rock metasomatism in generating the range of garnet and clinopyroxene compositions observed in diamonds from the sub-continental lithospheric mantle. We use the Deep Earth Water model to predict the results of metasomatism between silicic, carbonatitic and peridotitic fluids and common mantle rocks (peridotites, eclogites and pyroxenites) at 5 GPa, 1000 °C, across a range of redox conditions (logfO2 = −2 to −4 ΔFMQ), and a wide range of initial carbon concentrations in the metasomatic fluids. Our results show that the predicted compositions of metasomatic garnets and clinopyroxenes are controlled by the initial geochemistry of fluids and rocks, with subsequent mineral-specific geochemical evolution following definable reaction pathways. Model carbon-rich metasomatic fluids that can form diamond (initial C-content >5.00 molal) result in Mg-rich garnets and clinopyroxenes typical of peridotitic, eclogitic, and websteritic inclusions in diamonds. However, model carbon-poor metasomatic fluids that do not form diamond result in Mg-poor, Ca-rich garnets and clinopyroxenes. Such garnets and clinopyroxenes do nevertheless occur as inclusions in diamonds. In our models, the abundance of carbon in the fluids controls the behaviour of the bivalent ions through the formation of aqueous Mg-Ca-Fe-C complexes, which directly govern the composition of garnets and clinopyroxenes precipitated during the metasomatic processes. As the C-rich initial fluids can form the higher Mg-eclogitic, peridotitic, and websteritic inclusions in diamonds, these inclusions can be syngenetic (metasomatic) or possibly protogenetic. However, in our models, the relatively Mg-poor, Ca- and Fe-rich eclogitic garnet and clinopyroxene inclusions found in mantle diamonds formed from C-poor fluids that do not precipitate diamond. These inclusions most likely reflect a metasomatic event prior to being incorporated into their host diamonds, or they could represent protolith-based protogenetic geochemistry. Therefore, the paragenetic groups used to classify diamonds should not be considered a genetic classification, as the role of fluid geochemistry appears to be more important than the one played by host rock geochemistry.

Physicochemical and mineral characteristics of soil materials developed naturally on two ∼ 50 years old coal combustion residue disposal sites in Croatia

Coal combustion has been one of the most dominant sources of energy for the last two centuries, generating tonnes of coal combustion residue (CCR). Rapid soil formation has been observed at old CCR disposal sites, altering the physiochemical and mineral properties of CCR, affecting contaminant release mechanisms and nutrient availability. Although ubiquitous, pedological properties of weathered CCR have been studied at only a small number of disposal sites. This study characterized two CCR landfills of similar age (∼50 years) using a range of parameters, including pH, total nitrogen and organic carbon content, major oxides (Al2O3, CaO, and SiO2), and macronutrients (Ca, K, Mg, P, and S), as well as textural and mineralogical data. In addition, specific surface area and cation exchange capacity were determined to assess particle properties, and 13C and 29Si NMR spectra were examined to characterize the organic matter and degree of polymerization of the coal ash glassy phase. Such comprehensive approach aimed to determine indicators of soil formation and to characterize the capacity of such landfills to retain water, nutrients, and contaminants. Both landfills displayed evidence of pedogenesis reflected in the pH decrease, formation of secondary minerals (such as ettringite, hydrotalcite, gypsum, and calcite), and changes in the C:N ratio. The Plaški landfill seems to have a better capacity to hold water, nutrients, and contaminants evident by higher clay content, CEC, and SSA values, possibly explaining why it developed more rapidly than Štrmac despite their similar age. The presence of montmorillonite in Plaški could be one of the main factors accelerating pedogenesis. 13C NMR spectra point to the unburned coal particles as the main origin of organic matter and 29Si NMR spectra showed higher depolymerization of a non-crystalline fraction in bare ash samples than in vegetated ash samples.

Pore Structure and Fractal Characteristics of Marine–Continental Transitional Black Shales: A Case Study of the Permian Shanxi Formation in the Eastern Margin of the Ordos Basin

To study the microscopic pore characteristics of marine–continental transitional shale, we studied the Daning–Jixian block of the Shanxi Formation using low-pressure CO2 adsorption (LP-CO2A) and low-temperature N2 adsorption (LT-N2A) methods in conjunction with field emission scanning electron microscopy (FE-SEM), geochemistry, and mineral composition analysis in order to obtain pore structure characteristic parameters. The fractal dimension of the pores was calculated using the Frankel–Halsey–Hill (FHH) model, and the study also discusses the factors that influence the pore structure. The study found that the marine–continental transitional phase shale of the Shanxi Formation has clay mineral contents ranging from 36.24% to 65.21%. The total organic carbon (TOC) contents range from 0.64% to 9.70%. Additionally, the organic matter maturity is high. The FE-SEM and gas adsorption experiments revealed that the transitional shale of the Shanxi Formation possesses a diverse range of pore types with relatively large pore sizes. The dominant pore types are organic and intragranular pores, with pore morphologies predominantly appearing as slit and parallel plate structures. According to the experimental data on gas adsorption, the total SSA values range from 11.126 to 47.220 m2/g. The total PV values range from 0.014 to 0.056 cm3/g. Micropores make up a greater proportion of the total SSA, whereas mesoporous pores make up a greater proportion of the total PV. The distribution of shale pore fractal dimensions D1 and D2 (D1 is 2.470 to 2.557; D2 is 2.531 to 2.755), obtained through LT-N2A data, is relatively concentrated. D1 and D2 have a positive correlation with the TOC content, clay mineral content, and BET-SSA, and D1 and D2 have a negative correlation with the quartz content. D2 is positively correlated with the Langmuir volume, showing that D2 can be used to evaluate the methane adsorption capacity.

Variations in microscopic properties of biomass char: Implications for biochar characterization

Biochar, a carbon-rich material produced during the thermochemical conversion of biomass, is considered to be an important material for environmental applications and sustainable agriculture. With interest in its use growing, it is essential to understand how pyrolysis parameters control biochar properties and, subsequently, which analytical methods can be applied effectively in characterizing biochar. While various methods are already in use, the potential of reflected light microscopy analysis has not yet been widely explored.This paper focuses on examining the microscopic properties of various biochars by implementing reflected light microscopy and assessing whether this technique has the potential to deliver quick, reliable, and essential information for biochar characterization. To support microscopic observations, selected physical (density and surface area) and chemical parameters (carbon and sulfur content, functional group distribution) of biochar samples were also determined.Megascopically and microscopically there is a considerable difference among biochars of different feeds including their size and shape, porosity, ratio of the abundance of cellular to non-cellular pores, inorganic matter content, the ratio of thick-walled to thin-walled inertinite, or the ratio between high-reflectance inertinite to low-reflectance inertinite and their reactivity. The biochars studied also showed variations in the oxygenated groups contribution, a wide range of carbon content (14.7 to 98.8%), density (1.45 to 2.47 g/cm3), and surface areas (from <1 to 363.6 m2/g).Our results demonstrate that microscopic characteristics and reflectance of biochar can provide crucial diagnostic value for predicting biochar properties and, in combination with other physical and chemical properties, help to enhance information about the biomass conversion process and potential practical use of biochar.

A Study on the Impact of Silicon and Manganese on Peritectic Behavior in Low Alloy Steels Assisted by Mold Thermal Mapping Technology and Shell Growth Measurements

Non-uniform shell growth commonly caused by the peritectic transformation in low carbon and low alloy steels has been directly correlated with mold thermal maps using a mold immersion test into a molten steel alloy. Mold thermal maps were obtained by performing real-time temperature measurements with optical fibers embedded 1 mm from the mold working surface. Shell growth measurements were obtained by 3D optical scanning of the recovered steel shell following immersion testing. The effects of silicon and manganese on the shell growth and mold temperature maps have been examined in relation to the peritectic transformation for varying carbon contents. Results of thermodynamic and kinetic simulations using ThermoCalc and its kinetic module—DICTRA predicted that silicon expands the carbon content range to values between (0.12 pct C to 0.21 pct C) where peritectic behavior occurs and that manganese shrinks the carbon content range and shifts the range to lower carbon contents (0.06 pct C to 0.12 pct C). The results of these simulations were used to guide the selection of chemistries examined in the dip test experiments with the aim of validating the software predictions. Dip tests were performed at similar steel making temperatures that were used for the software simulations between 1600 °C and 1650 °C. Both software results and experimental observation showed relatively good agreement for the compositions examined.

Comparative analysis of as-delivered heat-resistant bearing steels

A comparative analysis of the regulatory document requirements and the actual metallurgical quality characteristic values of domestic (8Kh4V9F2-Sh, 8Kh5M3VFB-ID) and foreign (M50 VIM-VAR) as-delivered heat-resistant bearing steels is carried out. The chemical composition, non-metallic inclusions, carbide heterogeneity, carbide morphology and hardness of hot-rolled bars of different diameters are studied. Additionally, the heat resistance is determined. It is established that the best quality (narrow component ranges, less non-metallic inclusions contamination, carbide heterogeneity and hardness) has M50 VIM-VAR steel, the worst quality is 8Kh4V9F2-Sh steel, which meets the most stringent requirements of regulatory documentation for M50 VIM-VAR steel. In bars with a diameter of up to 22 mm, the quality of all steels according to the studied characteristics does not noticeably differ. 8Kh5M3VFB-ID steel has the widest range of carbon and chromium content, the highest hardness, aluminum nitrides and eutectic carbides of the "honeycomb" type are observed. 8Kh4V9F2-Sh steel has the most heat-resistant, which allows its use at higher operating temperatures. The obtained data can be used when choosing a steel grade for bearings of a specific range.

Extraction and Characterization of Microcrystalline Cellulose from Walnut, Almond and Apricot Stone Shells

Walnut, Almond and Apricot stone shells are abundantly available agro wastes worldwide and are sources of cellulose. In this study microcrystalline cellulose were isolated from these renewable biomasses through acid hydrolysis method. Isolation of microcrystalline was performed due to its potential significance in cosmetics, medicine and food industries. Acid hydrolysis is carried out at different concentrations of sulphuric acid. Surface morphology and elemental composition of microcrystalline cellulose was characterized with Scanning electron microscopy, energy dispersive x-ray spectroscopy and FT-IR spectroscopy. SEM clearly showed that microcrystalline cellulose obtained through high acid concentration has better structural similarities with commercial microcrystalline cellulose However microcrystalline cellulose obtained with low concentration of acid showed lower fibrillation. Elemental analysis revealed that amount of Sulphur impurity (1.17-1.18) is present in microcrystalline cellulose when hydrolyzed with high H2SO4 concentration while negligible (0.10-0.72) in microcrystalline cellulose treated with low concentration of H2SO4. It is also found that carbon and oxygen contents range in Walnut, almond and Apricot C; 50.89-58.73, 54.07-55.58, 54.19-55.62, O; 39.72-48.01, 43.54-43.71 and 41.75-44.34 respectively while FT-IR shows required functional groups in prepared MCC specifically representing beta 1-4 glycosidic linkage at 849 cm-1 that depicts improved cellulose content with in the sample. Thus, this work confirms that Walnut, Almond and Apricot stone are promising sources for microcrystalline cellulose.

Thermodynamics of the effect of alloying on phase formation during crystallization of aluminum matrix composites with exogenous reinforcement

A thermodynamic assessment of the effect of alloying elements (Si, Mg, Cu, Ti) on phase formation processes during the production and liquid-phase processing of cast aluminum matrix composite materials with exogenous reinforcement (Al–SiC, Al–B4C) was carried out. It was shown that without suppressing Al–Si–C and Al4C3 carbide formation in the range of carbon concentrations from 0 to 4.5 wt.%, the equilibrium phase composition of Al–SiC composites in the solid state at 423 to 575 °C lies in the (Al) + Si + Al4SiC4 three-phase region, and the Al4SiC4 ternary carbide is replaced by the Al8SiC7 compound at a temperature below 423 °C. SiC and B4C phases in Al–SiC–Cu and Al–B4C–Cu systems are stable in the entire crystallization range and do not interact with aluminum or copper. In the Al–SiC–Mg system, the crystallization of composites containing more than 0.58 wt.% magnesium ends in the (Al) + Al3Mg2 + SiC + Mg2Si four-phase region. In the Al–SiC–Ti system, the end of crystallization is observed in the (Al) + Al3Ti + SiC three-phase region. In the Al–B4C system, once Al4C3 phase formation is suppressed, aluminum borides are formed with a deviation from the concentrations of elements providing 10 vol.% B4C towards boron increase and free carbon is formed with a deviation towards boron decrease. Under equilibrium conditions, Al–B4C–Si system crystallization ends in the (Al) + B4C + AlB12 + Al8SiC7 four-phase region (at a silicon content of up to 0.67 wt.%, and in the (Al) + Si + AlB12 + Al8SiC7 region at a higher silicon content. In the Al–B4C–Ti system, crystallization ends in the (Al) + TiB2 + B4C three-phase region at a titanium content of less than 0.42 wt.%.

Understanding soil selenium accumulation and bioavailability through size resolved and elemental characterization of soil extracts

Dietary deficiency of selenium is a global health threat related to low selenium concentrations in crops. Despite the chemical similarity of selenium to the two more abundantly studied elements sulfur and arsenic, the understanding of its accumulation in soils and availability for plants is limited. The lack of understanding of soil selenium cycling is largely due to the unavailability of methods to characterize selenium species in soils, especially the organic ones. Here we develop a size-resolved multi-elemental method using liquid chromatography and elemental mass spectrometry, which enables an advanced characterization of selenium, sulfur, and arsenic species in soil extracts. We apply the analytical approach to soils sampled along the Kohala rainfall gradient on Big Island (Hawaii), which cover a large range of organic carbon and (oxy)hydroxides contents. Similarly to sulfur but contrarily to arsenic, a large fraction of selenium is found associated with organic matter in these soils. However, while sulfur and arsenic are predominantly found as oxyanions in water extracts, selenium mainly exists as small hydrophilic organic compounds. Combining Kohala soil speciation data with concentrations in parent rock and plants further suggests that selenium association with organic matter limits its mobility in soils and availability for plants.