Carbon Content Research Articles

CONDITIONS OF THE OAK FORESTS GROWTH AND CULTIVATION ON THE TOP SURFACES AND SLOPES OF THE NEAR-VOLGA AND ERGENI UPLANDS AND THE PLAINS OF THE SAL-MANYCH INTERFLUVE

Planted oak forests in the south of European Russia are of great conservation and economic importance. The widespread practice of their creation in dry steppes and semideserts dates back to the 1950-1970s and allows to form oak (Quercus robur L.) plantations with longevity up to 40-60 years. The aim of the study is to investigate the growth features of oak trees under different soil-climatic and biocenotic conditions and to suggest methods to increase their longevity.The research was carried out in 2011-2016 in the south of the Near-Volga Upland, the northern part of the Ergeni Upland and lowland plains of the Sal-Manych interfluve at 28 temporary sample plots using common methods of forest inventory and regression data analysis.It has been established that the viability of oak is limited by unfavorable topographic position of plantations, increased climate dryness (HC 0,4-0,6), high content of soil carbonates and shallow-lying horizon of their accumulation, as well as the presence of shrub layer and other competitors for moisture. Under these conditions, afforestation of depressions on the plains and shady slopes with pure plantations of oak and other species without shrubs should gain advantage. The methods of their creation should be modified depending on the topographic position of particular forest area and the climate dryness.So, the main soil cultivation in depressions could last 1-2 years, applying the system of black fallow with plantation plowing. It is advisable to keep 3,5-4,0-meter row spacing, frequent tending, and intensive clearing of young tree stands. Maturer plantations need careful sanitary-selective cuttings, mainly the low-type ones, and preservation of high canopy density. Poor water availability and deterioration of plantations should be prevented by construction of dams.Reclamation plantations of low marketability are created on flat areas after 2-3 years of deeper basic tillage. The carbonate horizon should be loosened and a large moisture reserve is needed. Row spacing of 2,5-3,0 meters is reasonable, accelerating the canopy closure. The area of tree nutrition is expanded by low-intensive uniformly selective cuttings, forming more open stands. The longevity of oak in already existing plantations could be increased by eliminating its competitors, such as living ground cover, shrubs and associated species.

Spatiotemporal Dynamics of Carbon and Nitrogen in Subtropical Urban Streams (Santo André, SP, Brazil)

Urban sprawl poses a significant threat to urban stream water quality due to impermeabilization, reduced vegetation cover, and the release of diffuse pollutants. This study evaluates water quality in seven catchments in Santo André, SP, considering seasonality. Nutrient concentrations and in situ measurements were taken during both dry and rainy seasons. Comparisons were made using Kruskal–Wallis and Mann–Whitney tests. Streams showed significant differences in relation to water quality parameters. The Carapetuba, Jundiaí, and Apiaí streams were most adversely affected, underscoring the need for urgent water quality intervention (water conductivity above 500 μS/cm, dissolved oxygen below 2 mg/L, total dissolved carbon above 50 mg/L, and total dissolved nitrogen above 25 mg/L). Significant differences were observed across seasons. The dry season showed elevated temperatures (above 25 °C) and increased total dissolved carbon (above 50 mg/L) and nitrogen concentrations (above 30 mg/L), indicating reduced dilution effects from rainfall and heightened organic contamination. Conversely, the wet season demonstrated lower nutrient concentrations, emphasizing seasonal dynamics. Sustained, long-term monitoring of urban streams in Santo André and the implementation of sewage collection and treatment in irregular settlements are recommended. These measures are essential to mitigate the adverse impacts of urban expansion on water quality.

Insights into the oxidative thermal stability of mesoporous triazine‐based organic polymers: Kinetics and thermodynamic parameters

AbstractThis study investigates the thermal degradation kinetics of mesoporous triazine‐based polymers, namely triazine‐amine and triazine‐ether polymers. The synthesis, physicochemical characterization, and catalytic applications of these polymers were discussed in our previous report. Herein, the thermal stability parameters, including kinetic triplets and thermodynamic parameters, were determined using thermogravimetric analysis (TGA) and non‐isothermal mathematical approximations such as Coats‐Redfern, Broido, and Horowitz–Metzger methods. Triazine‐ether polymers exhibit thermal stability within the range of 200°C–300°C, while triazine‐amine polymer demonstrates superior thermal stability, reaching up to 450°C. According to the Coats‐Redfern method, the degradation follows reaction orders of 0.5 ≤ n ≤ 1. The activation energy of triazine‐amine polymer is notably high, particularly at the third degradation stage (e.g., 89.0 kJ/mol by the Broido method), attributed to its high nitrogen content. Conversely, the higher carbon content of triazine‐ether polymers reduces their activation energy to approximately 30 kJ/mol at all stages and thus, facilitates the degradation process. Thermodynamically, the degradation process is favorable yet non‐spontaneous, with intermediate states of the polymers exhibiting higher entropy, indicative of their enhanced degradation capability.

Effect of particle size distribution of sediments on development of polder soils in Japan

Abstract Purpose Polder soils develop from oceanic and lacustrine sediments covered with seawater, brackish water, and freshwater after artificial drainage. Because there are several concerns regarding the agricultural use of polder soils, soil genesis and properties have been considerably surveyed, mainly focusing on problematic soils developed from fine sediments. Although sediments have a wide range of particle size distributions due to different sedimentary conditions, particle size of parent materials have not been well addressed to understand the soil developmental process. In this study, Japanese polders with different reclamation ages and sedimentary conditions were surveyed to clarify the soil formation process and factors affecting pedogenesis. Materials and methods Soil samples were collected from 15 soil profiles in six Japanese polders under different land use types. Sedimentary conditions of polders were evaluated from particle size distributions using the hydrodynamic classification proposed by Pejrup (The triangular diagram used for classification of estuarine sediments: a new approach. Tide-influenced Sediment Environ Facies, pp 289–300, 1988). The major soil-forming factors of polders were extracted by principal component analysis (PCA) using general soil properties. Results and discussion Brackish lake and inner bay polders were characterized by calm hydrodynamic conditions comprising fine particles. Two polders reclaimed from a shallow inland sea were characterized by violent hydrodynamic conditions. Sandy sediments were also characteristic of immature soils reclaimed from a freshwater lake and an estuarine tidal flat. Soils on polders developed under calm hydrodynamic conditions enabled the accumulation of high total carbon content. The soil-forming process in the brackish bay oxidized pyrite, leading to an acidic soil reaction. Conversely, soils developed from sandy sediments were characterized by low iron content. The PCA extracted two factors explained by particle size and soil reaction relating to acidification and salt leaching. Conclusion Polder soils can be mainly discriminated by their particle size distributions, which are characterized by hydrodynamics under the sedimentary conditions, and the polder soil development is affected by water management in land uses after artificial drainage.

Characterization of groundnut shell biochar produced with different stainless steel combustion compartment volumes

AbstractBiochar, a solid material derived from a thermochemical process, has received significant attention due to its usefulness in various sectors. Previous studies have been conducted to improve the properties and quality of this material by altering the thermochemical processes, treating the feedstock, hybridizing the feedstock, and so forth, but little has been done on the effect of varying the reactor's configuration. This research aims to study the effect of varying the stainless‐steel‐based combustion compartment volume of a biomass‐fueled top‐lit updraft gasifier on the groundnut shell biochar. The biochar yields for reactors ranged from 34.9% to 51.2%. The sample produced in the smallest combustion compartment volume showed the highest carbon content, according to energy dispersive X‐ray spectroscopy (EDX) analysis. Potassium, another major element, decreased as the combustion compartment was reduced. Scanning electron microscopy (SEM) analysis revealed that the biochar samples produced had an irregular shape and rough surfaces, and reducing the combustion compartment volume resulted in larger particles on the surface. Fourier transform infrared (FTIR) spectroscopy analysis showed similarities and differences in peaks observed for all the samples. The biochar samples produced can find applications in wastewater treatment, energy conversion and storage, and soil amendment, and the findings contribute to the design and optimization of biomass‐based gasifiers.

Synergetic sludge conditioning by US enhanced Fe2+ activated sodium persulfate: Physicochemical properties and mechanisms

Efficient dewatering of sewage sludge is an energy- and carbon-saving procedure for sludge treatment in wastewater treatment facilities. The ultrasound-coupled divalent iron ion activated persulfate process can effectively promote sludge dewatering and improve organic substance content. Under the action of ultrasound (US 50 w/L), divalent iron ions (Fe2+) 200 mg/g (TS), and persulfate (PDS) 200 mg/g (TS) for 60 min, the capillary suction time (CST) was reduced by 79.74%, and the moisture content of the dewatered sludge cake reached 56.51 wt%. The organic carbon content of treated sludge was also four times higher than the original sludge and types were richer in short-chain volatile species in US/Fe2+/PDS. Moreover, the correlation analysis found that the relationship of between CST and SV30, Zeta and lactate dehydrogenase (LDH) were positive correlation, and the relationship of SCOD and TC were positively correlated with the PN (SB-EPS). Mechanistic studies showed that the US/Fe2+/PDS system could produce oxygen activators by US coupling Fe2+ to strengthen the effect of activated PDS strongly, while the sulfate radicals (SO4·-) radical was a dominant role. The cracking mechanism is divided into two pathways effectively degraded the macromolecule EPS into a small-molecule acid and further reduced the water-holding interfacial affinity as follow: (1) the radical path dominated by hydroxyl radicals (·OH), SO4·-, and superoxide radical (O2·-); (2) the non-radicals dominated by monoclinic oxygen (1O2). Afterwards, the electrostatic force and interfacial free energy were reduced, resulting in enhanced self-flocculation and mobility to enhanced dewaterability. These findings demonstrated the US/Fe2+/PDS system had significant advantages in sludge cracking and provided theoretical support for its practical application.

Response of Soil Fungal Community in Coastal Saline Soil to Short-Term Water Management Combined with Bio-Organic Fertilizer

This study aimed to elucidate the response of soil microbial communities to saline soil amelioration via biological organic fertilizer. A year-long experiment was conducted on coastal saline soil, employing water and fertilizer strategies. Three treatments were compared: dry field (control, CK), paddy field (W), and combined dry and irrigated fields with biological organic fertilizer (BW). Soil DNA was extracted and sequenced using high-throughput methods, revealing significant reductions in soil electrical conductivity (EC) and pH with W and BW treatments. Moreover, the BW treatment notably increased soil organic carbon content by 17.2%, as well as soil urease and alkaline phosphatase activity. Fungal community richness increased, with the BW treatment showing a 36% rise in the ACE index and a 24% increase in the Shannon index, while the Simpson index decreased by 59%. Dominant fungal phyla were Ascomycota, Mortierellomycota, and Basidiomycota, with Basidiomycota prevailing at the genus level. Redundancy analysis (RDA) indicated that soil pH, EC, and organic carbon were key determinants of fungal community distribution, with the BW treatment correlating negatively with pH and salt and positively with soil organic carbon (SOC). Fungal functional groups varied among treatments, with saprophytic fungi predominating, but the BW treatment showed a higher relative abundance of animal pathogenic fungi. In summary, the integration of biological organic fertilizer with flooding ameliorates soil properties and influences the changes in soil fungal community structure and function in the short term. These results could enhance the scientific basis for the efficient utilization and development of saline soil resources in coastal areas.

Effect of Integrated Use of Manures and Fertilizers on Physico-chemical Properties of Soil and Yield of Coconut (Cocos nucifera L.)

A field experiment was conducted during 2014-15 and 2015-16 in a thirty years old coconut garden of cultivar Pratap to study the effect of Integrated Use of Manures and Fertilizers on Physico-chemical Properties of Soil and Yield of Coconut (Cocos nucifera L.). Accordingly, treatments were applied to coconut orchard in three splits (viz., Stage I- June, Stage II- October and Stage III- February) in a year. Soil samples were collected periodically before fertilizers application and analysed for different physico-chemical properties (viz., pH, EC and organic carbon). The yield of each palm was recorded throughout the year under experimental plot. The application of RDN through FYM at 25 kg/palm/year + Neem Cake at 15 kg/palm/year + Vermicompost at 6 kg/palm/year (T10) recorded significant increase in pH, EC and organic carbon content in soil of coconut orchard. Also the physico-chemical properties of soil found to be improved during second year over the first year of experimentation. The application of RDF + Azadirachtin + Micronutrients through briquettes (T5) received highest yield of coconut. Therefore, it is concluded that application of RDF along with Azadirachtin and Micronutrients through Konkan Annapurna Briquettes in three splits (i.e. June, October and February) is beneficial for increasing the yield of coconut.

From sewage sludge and lignocellulose to hydrochar by co-hydrothermal carbonization: Mechanism and combustion characteristics

This investigation focuses on fabrication of hydrothermal carbon (HTC) using the co-hydrothermal carbonization (Co-HTC) method from the raw materials of sewage sludge (SS) and lignocellulose. The as-prepared hydrochar (HC) was characterized and analyzed by using ultimate analysis, proximate analysis, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, and Fourier transform infrared spectroscopy (FTIR) to investigate its fuel properties, surface morphology, and molecular structure. Particularly, the HC obtained from the Co-HTC process with pine sawdust as raw material exhibited several advantages in terms of carbon content (40.40 %), fixed carbon (FC) content (41.82 %), and high heating value (HHV, 14.87 MJ/kg). Synergistic effects were achieved from the components in the Co-HTC system, leading to increased carbon content, retention of organics, energy yield, HHV, and HC yield. Notably, the Co-HTC treatment of pine sawdust and SS demonstrated the most notable synergistic effect. Thermogravimetric analysis and combustion characteristic index (CCI) values showed that softwood lignin, represented by pine sawdust, exhibited better performance during combustion, with a CCI value of 21.78 (10−7 min−2 °C−3). In short, Co-HTC of hydrochar from lignocellulose and SS can represent a promising approach to resource utilization for obtaining solid fuel.

Effect of carburizing time treatment on microstructure and mechanical properties of low alloy gear steels

Gas carburizing significantly enhances the surface properties of low-alloy gear steels, resulting in superior micro-hardness, layer thickness, carbon content, and overall mechanical properties. Unlike other thermochemical processes such as nitriding and carbonitriding, which have limitations in core properties and hardening depth, gas carburizing offers unmatched surface hardness, wear resistance, and mechanical strength. This makes it ideal for demanding applications in the automotive, aerospace, and manufacturing industries. In this research, samples were gas-carburized for 4, 6, or 8 h. The results showed significant improvements: micro-hardness increased from approximately 140 HV to over 819 HV, and the surface layer thickness grew by more than 41%, from 1166 μm to 1576 μm. Additionally, the carbon content in the surface layer increased by over 450%, reaching up to 0.94 wt%. Clear correlations were observed between the duration of heating and the mechanical properties. Longer heating times, particularly after 8 h, raised ultimate tensile strength from 427.29 MPa to 778.33 MPa, while simultaneously decreasing elongation from 26.07% to 2.88% and resilience from 180 J cm−2 to 6.66 J cm−2. This optimization not only enhances surface hardness and durability but also improves key mechanical properties such as tensile strength, stiffness, resilience, and overall mechanical performance.

C/O Ratios and the Formation of Wide-separation Exoplanets

The gas and solid-state C/O ratios provide context to potentially link the atmospheric composition of planets to that of the natal disk. We provide a synthesis of extant estimates of the gaseous C/O and C/H ratios in planet-forming disks obtained primarily through analysis of Atacama Large Millimeter/submillimeter Array observations. These estimates are compared to atmospheric abundances of wide-separation (>10 au) gas giants. The resolved disk gas C/O ratios, from seven systems, generally exhibit C/O ≥ 1 with subsolar, or depleted, carbon content. In contrast, wide-separation gas giants have atmospheric C/O ratios that cluster near or slightly above the presumed stellar value with a range of elemental C/H. From the existing disk composition, we infer that the solid-state millimeter/centimeter-sized pebbles have a total C/O ratio (solid cores and ices) that is solar (stellar) in content. We explore simple models that reconstruct the exoplanet atmospheric composition from the disk, while accounting for silicate cloud formation in the planet atmosphere. If wide-separation planets formed via the core-accretion mechanism, they must acquire their metals from pebble or planetesimal accretion. Further, the dispersion in giant planet C/H content is best matched by a disk composition with modest and variable factors of carbon depletion. An origin of the wide-separation gas giants via gravitational instability cannot be ruled out, as stellar C/O ratios should natively form in this scenario. However, the variation in planet metallicity with a stellar C/O ratio potentially presents challenges to these models.

Optimization of hydrochar synthesis conditions for enhanced Cd(II) and Pb(II) adsorption in mono and multimetallic systems

The characterisation of hydrochars derived from Sargassum biomass collected along the Mexican Caribbean coast reveals their favourable morphology and chemical composition for incorporating metal ions, including Cd(II) and Pb(II). Among the synthesized materials, HCS-3, produced at 180 °C with a 2 h residence time, exhibited superior yield, specific area, carbon content, and capacity for removing Cd(II) and Pb(II). Adsorption equilibrium studies demonstrate the presence of adsorption processes during Cd(II) and Pb(II) retention on HCS-3, with adsorption capacities slightly exceeding 140 and 340 mg g⁻1, respectively. Notably, HCS-3 shows a greater affinity for Pb(II) over Cd(II) when both elements are present concurrently. The physicochemical analysis through FTIR spectroscopy, functional group analysis, point of zero charge determination, SEM/EDS, and other techniques evidenced that HCS-3 possesses favourable characteristics to serve as a heavy metal adsorbent. These findings underscore the efficacy of hydrochars from Sargassum biomass in removing heavy metals, suggesting their potential as superior adsorbents compared to traditional or novel materials, and advising its possible versatility for other pollutants. Utilizing these hydrochars could mitigate the economic and environmental impact of Sargassum biomass by repurposing it for valuable applications.

Potential of reproductive traits in functional ecology: A quantitative comparison of variability in floral, fruit, and leaf traits.

Despite their claimed low intraspecific variability, plant reproductive traits are less frequently used in functional ecology. Here we focused on underrepresented plant organs, i.e. flowers and fruits, by comparing their traits with well-established leaf traits. We evaluated 16 functional traits (six floral, six fruit, and four leaf traits) in a randomly selected group of woody species under comparable environmental conditions. We aimed to assess interspecific and intraspecimen variability and explore the potential of the proposed flower and fruit traits for ecological research. Traits related to the dry mass of flowers and fruits exhibited the highest interspecific variability, while carbon content traits in flowers and leaves had the lowest. At a specimen level, specific leaf area revealed the highest variation. Carbon content traits for all organs demonstrated the least intraspecimen variability, with flower carbon content being the least variable. Our study revealed connections between the newly proposed traits and widely recognized functional traits, uncovering intriguing links between the established traits and the floral and fruit traits upon which we focused. This complements the already well-recognized variability in plant form and function with additional insights into reproductive processes.

Implementation of a control and monitoring system for a cathodic protection cell to mitigate localized corrosion in fixed and mobile steel structures

The current study introduces a novel technique to handle electrochemical localized corrosion in certain limited regions rather than applying comprehensive cathodic protection (CP) treatment. An impressed current cathodic protection cell (ICCPC) was fabricated and firmly installed on the middle of a steel structure surface to deter localized corrosion in fixed or mobile steel structures. The designed ICCPC comprises three essential parts: an anode, a cathode, and an artificial electrolyte. The latter was developed to mimic the function of the natural electrolyte in CP. A proportional-integrated-derivative (PID) controller was designed to stabilize this potential below the ICCPC at a cathodic potential of −850 mV, which is crucial for protection efficacy. The controller of the protection system was designed to automatically activate the ICCPC when the environment of the steel structure is exposed to humidity. At a temperature range from 27 °C to 35 °C, the protection potential, current, and power showed an increase in percentage by 411 %, 688.74 %, and 2842.3 %, respectively when the humidity level rose from 10 % to 100 %. The intended spraying of sodium chloride (NaCl) solution on the structure at different concentrations from 1.5 % to 5 % showed excellent protection against corrosion, notable improvements in electrical conductivity, and reduction in resistance between the anode and cathode. The energy dispersive spectroscopy and scanning electron microscopy (SEM-EDS) analyses confirm effective corrosion inhibition under ICCPC coverage compared to unprotected areas. These tests revealed an absence of oxidation beneath the ICCPC compared with areas outside of its coverage. The areas outside of ICCPC protection showed a reduction in iron and carbon contents from 57.1 % to 47.0 % and 41.4 %–22.4 %, respectively, and an increase in oxygen from 1.6 % to 30.6 %.

Unveiling the efficiency of peanut shell-derived porous composite for water denitrification: Characterization, kinetic, isotherm and thermodynamic studies

This research investigated the valorization of peanut shell (PS) waste to produce a ZnO-modified activated carbon composite ZnO@PS-AC for water denitrification. The composite was synthesized through chemical activation with ZnCl₂ followed by pyrolysis at 700 °C. Characterization techniques revealed a highly porous structure with over 79 % carbon content and successful ZnO formation, indicating the effectiveness of the synthesis process. Batch adsorption experiments were conducted to evaluate nitrate removal under various conditions. The adsorption process demonstrated rapid kinetics, reaching equilibrium within 60 min. Isotherm studies showed a maximum adsorption capacity of 17.9 mg/g, while kinetic analysis revealed significant nitrate removal within the first 5 min. Phenomenological modelling suggested that adsorption onto active sites was the rate-limiting step in the process. Thermodynamic analysis indicated an exothermic, physical adsorption process, providing insights into the nature of the nitrate-adsorbent interactions. The study highlights ZnO@PS-AC’s potential as an eco-friendly, cost-effective adsorbent for nitrate removal from water. Its porous structure facilitates rapid uptake and efficient removal, making it a promising solution for water treatment applications. These findings demonstrate the viability of valorizing agricultural waste into effective water treatment materials, contributing to both waste management and environmental remediation efforts.

Ultra-high temperature brazing of C/C using a simplified FeNiCrCu high-entropy alloy as filler

To increase remelting temperature of C/C brazed joint, a simplified FeNiCrCu high-entropy alloy (HEA) filler was designed in high-temperature brazing (HTB). The joint formation mechanism and fracture behavior were studied. The eutectic reaction of FeNiCrCu HEA with C/C could not occur, helping increase joint remelting temperature over HEA melting point (1334 °C). For the recommended parameter 1350 °C-2 min, C/C dissolution occurred well, and no defect was observed both at interface and within bond seam. The maximum shear strength was 24.2 MPa due to the high strength in-situ (Cr,Fe)3C2 reinforced the high plastic Cu-Ni-Fe(S.S.) matrix and intimate wavy interface. Cr existed only in M3C2 in bond seam, reducing both carbon content and CTE of bond seam. For higher temperature and longer time, excessive liquid carbon content resulted in the presence of large solidified carbon with defect at interface, joint shear strength decreased dramatically. These results provide a unique braze system for brazing carbon-based materials.

Pedogenic variables with color indices in rubified Alfisols in the Kakalachinte microwatershed, Karnataka, South India

Soil properties and processes can often be estimated by soil color, which provides valuable information about composition and other properties. We focused on the morphology, particle size distribution, and chemical properties of Alfisols in Kakalachinte microwatershed, Karnataka, India. Soil redness indices were calculated: Buntley's and Westin's rate (BWR), Hurst's rate (HR); Torrent’ rates (TR1 and TR2); Barrón's and Torrent's rates (BTR1 and BTR2), and Viscarra's rate (VR). The Munsell notation was converted to the CIE (Commission Internationale del'Eclairage, CIE) Lab system, Lab model: L*, luminance, a*, redness, and b*, yellowness of moist soil samples. Forty-five soil samples were characterized for texture, soil reaction (pH), electrical conductivity, calcium carbonate content, organic carbon (OC) content, exchangeable cations (sodium, Na; potassium, K; magnesium, Mg; and calcium, Ca), base saturation (BS), and cation exchange capacity (CEC). The pH of the soils ranged from strongly acid (pH of 5.25) to strongly alkaline (pH of 8.73). These soils exhibited a low CEC, with a mean of 8.36 cmol(+)/kg and a coefficient of variation of >35%. The BS was found to be >70%, with a dominance of exchangeable Ca (6.93 ± 1.08 cmol(+)/kg). Correlation analysis revealed strong positive relationships between OC and the L* value (r = 0.6**). The correlation results revealed a strong positive correlation of a* value with TR1 (r = 0.54**), significant negative relationship between L* and BTR1 (r = −0.54*), BTR2 (r = −0.525*), and VR (r = −0.53*). Regression between soil OC and the L* value showed R2 of 0.40 and RMSE of 0.01; soil exchangeable K and Mg with the R2 = 0.74; RMSE = 0.12 and the R2 = 0.42; RMSE = 0.11 at p < 0.001. The study highlights the importance of converting Munsell color notation to the CIELab system for understanding the rubification process in relation to soil properties in Alfisols at the microwatershed level.

Enhanced tribological behavior and corrosion resistance in AlSiC-based coatings through varied carbon content

A series of AlSiC-based nanocomposite coatings with varying carbon concentrations were fabricated by filtered cathodic vacuum arc (FCVA) technology. These coatings featured an amorphous matrix with embedded Al4Si3C6 nanocrystals. With the increase in carbon content, the proportion of amorphous structure within the structure grew, which was accompanied by a rise in sp3 hybridized carbon bonds. This compositional change led to a significant enhancement in hardness and toughness. Notably, the AlSiC coating deposited at a flow rate of 50 sccm displayed exceptional mechanical properties, including a high hardness of approximately 23.2 GPa, toughness indices of H/E = 0.096 and H3/E2 = 0.216 GPa, a low friction coefficient around 0.18, a wear rate as low as ∼1.09 × 10−5 mm3 N−1 m−1, and a corrosion current density of approximately 1.08 × 10−9 A/cm2. The coating's superior tribological characteristics and corrosion resistance can be attributed to two main factors. The enhanced hardness and toughness indices (H/E and H3/E2) contributed to its improved deformability, which is essential for wear resistance. Secondly, the presence of a graphite layer formed during friction provided self-lubrication, further reducing wear. Additionally, the chemical inertness of both the amorphous SiC and the amorphous carbon phases within the nanocomposite structure significantly bolstered the coating's resistance to corrosion. The AlSiC nanocomposite coatings deposited by FCVA exhibit outstanding mechanical properties, tribological performance, and corrosion resistance, making them highly suitable for applications in environments where wear and corrosion are significant concerns.

Activation preference: A new descriptor to predict non-radical oxidation pathways

The peroxymonosulfate (PMS) activation was influenced strongly by active sites on a catalyst surface. To some extent, biochar characters, such as structure, elemental composition, and specific surface area (SSA), can reflect the composition of active sites. However, the understanding of active centers lacked accuracy in the structure–activity relationships of biochar-based catalysts (BBC) due to the consideration of one single feature. In this study, XGBoost (XGB), random forest regression (RF), and supporting vector regression (SVR) models were employed to construct descriptors to predict non-radical (NR) contribution in BBC/PMS systems. Consequently, the XGB model provided the best prediction with an R2 value of 0.81. Thereby, activation preference (γ), as a characteristic descriptor of BBC, was developed using the XGB model. Interestingly, the descriptor fully considered carbon content (C%), oxygen content (O%), defects (ID/IG), and SSA. Besides, O% played the most critical role in predicting NR contribution. Noticeably, the NR oxidation pathway could be promoted within the range of 50–60 % for C%, 30–50 % for O%, 0.4–1.2 for ID/IG, and 579–1259 m2/g for SSA in the BBC/PMS system. Herein, machine learning (ML) was applied to develop a comprehensive descriptor, further providing an innovative strategy for high-throughput screening of BBCs to activate PMS efficiently. The comprehensive descriptor offered a new perspective for elucidating the structure–activity relationship of BBC, facilitating the application of BBC/PMS systems in water treatment.

Core-shell structured LiFePO4/C nanocomposite battery material for lithium production from brines

The development of affordable and environmentally friendly methods to produce lithium is urgently required to cope with the accelerating growth of the lithium battery market. Battery materials such as LiFePO4 can be used to selectively sequestrate lithium from brine natural resources, thus producing a high-purity lithium salt for battery manufacture, but the long-term stability of the material is currently not sufficient for practical applications. Here, we report, for the first time, the development of a nanosized core-shell structured LiFePO4/C material for applications in lithium production from brines. This LiFePO4/C with a LiFePO4-core (∼123 nm size) covered by a pinhole-free carbon shell (∼5 nm thickness) was prepared via solvothermal synthesis, and the carbon content was optimised to 5 wt%. The optimal core-shell structured LiFePO4/C material exhibits a lithium extraction capacity of ca. 160 mA h g-1 at C/10 and ca. 130 mA h g-1 at 1C, and >87% capacity retention after 50 cycles of lithium sequestration and release at C/10 in synthetic brines. This excellent electrochemical performance is attributed to the homogenous nanosizing of the LiFePO4 particles as well as the full coverage of the carbon coating, which provides effective protection by preventing the direct contact of LiFePO4 with the brines, thus stopping the surface degradation reactions that compromise the long-term stability. A direct comparison with three commercial LiFePO4 materials demonstrates that, while similar performance is obtained in non-aqueous lithium-ion batteries, for lithium production applications, core-shell nanostructuring is crucial to achieve high capacity and preserve the material's longevity.