Si Content Research Articles

Role of silicon in legume‐insect interactions: Insights from a plant experiencing different levels of herbivory

Abstract Silicon (Si) supplementation can enhance symbiotic functions in some legumes (Fabaceae) with their nitrogen‐fixing rhizobia, such as root nodulation and nitrogen fixation. However, it is still poorly understood how Si influences legume–insect interactions. Here, we investigated how a symbiotic legume responds not only to Si supplementation but also to herbivory treatment with varying infestation levels in two events. We conducted a controlled climate chamber experiment by growing Medicago truncatula plants inoculated with rhizobia. For half of the plants, the soil was kept without Si (−Si), whereas the other half was regularly supplemented with Si (+Si). We then infested the plants with caterpillars of Spodoptera littoralis with 0, 1 or 3 larvae and 0, 1 or 1 larva in single herbivory attack and in double herbivory attack, respectively. To understand plant responses to such treatment combinations, we examined 16 functional traits. Nodule number, nodule fresh mass and nodule leghaemoglobin concentrations were not affected in single attack plants. However, increasing levels of herbivory led to decreases in such measured traits in double attack plants. Foliar C to N ratio increased in single attack plants but decreased in double attack plants with increasing levels of herbivory, indicating contrasting resource allocation. Herbivory did not affect the content of foliar Si, which was higher in +Si than −Si plants. Si and herbivory led to reduced foliar phenolics in double attack plants, suggesting a potential trade‐off between silicification and phenolic production. Si and herbivory led to increased trichome densities in single attack plants, but patterns were less clear in double attack plants. Herbivory but not Si reduced plant biomass with increasing levels of herbivory in double attack plants. Relative growth rates of the caterpillars, as proxy for plant resistance, decreased mainly due to herbivory treatment, when fed on single attack plants. Using a trait‐based approach, we provide novel insights to better understand the response of a legume to Si supplementation and different herbivory levels and events. We conclude that herbivory predominantly exerts much stronger effects than Si on various plant traits, pointing to a necessity to respond to herbivory by induced defence strategies. Read the free Plain Language Summary for this article on the Journal blog.

Effect of H on Mechanical Properties and Corrosion Resistance of Ferritic/Martensitic Steels with Different Si Contents

Effect of H on Mechanical Properties and Corrosion Resistance of Ferritic/Martensitic Steels with Different Si Contents

Effect of gradation on thermal and mechanical properties of reaction‐bonded silicon carbide ceramics

AbstractParticle grading is a reliable method to improve mechanical properties of reaction‐bonded silicon carbide (RBSC) ceramics. This work aims to explore the effects of particle grading on thermal and mechanical characteristics of RBSC ceramics. Results showed that the powder grading enabled to increase sintering density of silicon carbide (SiC) ceramics. The use of large particle SiC powder in grading led to a 28% increase in thermal conductivity but a 22% decrease in bending strength. Meanwhile, the addition of finer SiC powder exerted minimal effect on thermal conductivity but noticeably increased bending strength by 10%. Therefore, properly adjusting particle size in grading allows for the control of residual Si content and microstructure, thereby simultaneously increasing thermal conductivity and bending strength of the material.

Unraveling the Complex Temperature-Dependent Performance and Degradation of Li-Ion Batteries with Silicon-Graphite Composite Anodes

Competing effects of graphite and Si result in a complex temperature dependent performance and degradation of Li-ion batteries with Si-graphite composite anodes. This study examines the influence of varying the Si content (0 to 20.8 wt%) in Si-graphite composite anodes with consistent areal capacity and N/P ratio in full cells containing NMC622 cathodes. One hundred pilot-scale double-layer pouch cells were built and cycle aged in the temperature range from −10 to 55 °C. Electrochemical characterization demonstrated that increasing Si contents enhance capacity and mitigate internal resistance at low temperatures. On the other hand, high Si contents decrease charge-discharge energy efficiency and cycle life, particularly at elevated temperatures. Post-mortem analysis of aged electrodes, including physico-chemical characterization (scanning electron microscopy, energy-dispersive X-ray analysis, thickness measurements) and cell reconstruction revealed significant solid electrolyte interphase growth and increased loss of active material in anodes with high Si content. The optimum temperature for longest cycle life as derived from Arrhenius plots decreased from 30 °C for graphite anodes to 10 °C for cells with moderate Si content up to 5.8 wt%. These findings allow the design of optimized cells by balancing the Si content versus operating temperature in order to achieve lowest cell aging.

Influence of Si-addition on tribological and corrosion properties of Ta-Si-C coatings

Ta-Si-C coatings with Si content varying from 2.7 to 30.8 at.% were synthesized by magnetron co-sputtering. Their microstructure, tribological properties and corrosion performance were investigated. The coatings exhibited two distinct structural forms: a Ta(C, Si) solid solution for the lower silicon contents (2.7 and 5.6 at.% Si) and a Ta(C, Si)/a-C:Si nanocomposite for higher Si content (13.7, 20.8 and 30.8 at.% Si). Notably, the Ta(C, Si) solid solution at 5.6 at.% Si demonstrated the highest hardness of 44±2.7 GPa, resulting from the solid solution strengthening. Furthermore, this solid solution also demonstrated the lowest wear rate (1.21×10-6 mm3N-1m-1), due to its superior hardness and H3/E2 ratio. Additionally, the coating with 5.6 at.% Si displayed the most outstanding corrosion resistance, attributed to its higher crystalline quality and denser structure, which effectively prevented the permeation of corrosive media through the coating to the substrate.

Thermal Stability and Thermal Fatigue Resistance Improvement of New High Toughness 5% Cr Hot Working Die Steel

This work developed a new high toughness 5% Cr martensitic hot working die steel (GYDCK-20), which exhibits better thermal stability and thermal fatigue resistance than AISI H13 steel. The concrete study involves: conducting on the evolution of microstructures and mechanical properties of two steels during the 60-hour holding process at 600°C, as well as the thermal fatigue behavior under the cyclic heating-water quenching conditions. The experimental results showed that in the case of ensuring the same initial hardness of two steels (43-43.5 HRC), GYDCK-20 emerged better thermal stability and superior toughness after 60-hour holding process at 600°C. After thermal cycling was increased from 1000 to 2000 times, the average crack length growth rate of GYDCK-20 was 31.8% lower than that of H13 and the maximum crack width growth rate was 35.1% lower than that of H13. It was found that thermal fatigue cracking was dominated by transgranular propagation at lower cycle numbers, while more inclined to propagate along the grain boundaries at higher cycle numbers. The higher toughness of GYDCK-20 steel promotes the dispersion of thermal stress, thereby enhancing the thermal fatigue resistance. It is mainly attributed to the lower V content of GYDCK-20 steel, which reduces the density of large-sized MC primary carbides. On the other hand, the lower Si content promotes the dissolution of cementite particles, and the secondary carbides precipitate in a smaller and uniformly distributed form, which hinders the propagation of thermal fatigue cracks, while also delays the coarsening of the fatigue-adverse phase M23C6 carbides.

Exceptional strength-ductility synergy in the novel metastable FeCoCrNiVSi high-entropy alloys via tuning the grain size dependency of the transformation-induced plasticity effect

In-depth knowledge of the coupling between grain refinement and the transformation-induced plasticity (TRIP) effect in metastable alloys is a viable approach for the improvement of strength-ductility synergy, which needs systematic research with consideration of commercial austenitic stainless steels and novel high-entropy alloys (HEAs). Accordingly, in the present work, two Si-containing metastable HEAs in the Fe47Co30Cr10Ni5V8-xSix system (x = 3 and 6 at.%) were designed, and the TRIP-assisted AISI 304L stainless steel was also considered for comparison. The alloys were processed by cold rolling and annealing to obtain different grain sizes. Reducing the stacking fault energy (SFE) through adjusting chemical composition contributes to minimizing the detrimental effect of grain refinement on the ductility of TRIP alloys, while extremely low SFE must be avoided owing to the fast kinetics of deformation-induced martensitic phase transformation, which leads to the deterioration of ductility. In contrast to AISI 304L stainless steel, a strong TRIP effect was maintained upon grain refinement in the Fe47Co30Cr10Ni5V2Si6 HEA due to the remaining apparent SFE in the appropriate TRIP range. The tuned kinetics of martensitic transformation was found to be responsible for the exceptional ductility (∼65%) of Fe47Co30Cr10Ni5V2Si6 HEA at an ultrahigh tensile strength of 1250 MPa. Therefore, considering the identical trend of SFE with grain size, an appropriate initial SFE value is important for tuning the grain size dependency of the TRIP effect. Moreover, the ultrahigh strength was attributed to the high volume fraction of α΄-martensite as well as the high strength of the martensite phase due to the high Si content. Accordingly, for achieving strong-yet-ductile HEAs, a high Si content is recommended to benefit from solid solution strengthening in the martensite phase, a specially-designed chemical composition is needed for attaining a high volume fraction of α΄-martensite, and SFE should be in a desirable range to tune the kinetics of martensitic phase transformation.

Reduced Graphene Oxide/Silica Based Electrode Material: Synthesis and Characterization

<span lang="EN-US">Developing a Reduced Graphene Oxide (rGO) synthesis method based on rice husk as a composite electrode material with silica has garnered particular attention for designing high-quality electrode materials. This research successfully synthesized rGO-Si material from rice husk-derived activated carbon through a one-step thermal reduction process at 200 °C. This method offers a simple, efficient, cost-effective, and environmentally friendly synthesis approach. The resulting samples' morphology, surface composition, crystal structure, surface area, and pore diameter size were characterized using FE-SEM, EDX, XRD, and SAA-BET. EDX characterization results confirmed the predominance of carbon content in the samples. At the same time, the natural emergence of Si without external addition due to thermal reduction at 200 °C was an intriguing initial finding. The spherical crystal structure of silica between the wrinkled rGO layers was confirmed through FE-SEM and XRD analysis. The synergistic effect between Si and rGO significantly increased the sample's surface area, with a value of 34.17 m<sup>2</sup>/g for the rGO sample before thermal reduction, which increased to 121.24 m<sup>2</sup>/g after the thermal reduction process at 200 °C. This process also positively impacted the reduction in pore size of rGO-Si, with a value decreasing from 9.33 nm before thermal reduction to 4.89 nm after the thermal reduction process. The results of this study demonstrate that rGO-Si synthesized from rice husk-derived activated carbon holds great potential as a high-performance electrode material, combining the advantages of thermal reduction, natural Si content, and increased surface area for diverse applications.</span>

Geochronological and geochemical constraints on the multistage magmatic processes of the Lianhuashan batholith, South China: Implications for the petrogenesis and polymetallic mineralization

The Lianhuashan batholith, which is a composite pluton located in the middle part of a world-class giant tungsten (W) polymetallic belt of South China, hosts a huge reserve of more than 50000 t of W. Despite this great economic significance, the petrogenesis of each phases of the Lianhuashan batholith, as well as its temporal and genetic relationships to the W polymetallic mineralization, is still unclear. To address these questions, we conducted a comprehensive study for the Lianhuashan batholith, including LA-ICP-MS zircon U-Pb dating, whole-rock geochemical and in-situ mineral trace element analyses. Different from previous studies, four main granitic phases (G1 to G4) were identified. The biotite granite (G1) formed from 168.6 to 165.3 Ma, has the lowest Si content and high Al and Fe contents, and is significantly depleted in Ba, Sr, Ti, P, and Nb whereas enriched in U, Hf, Zr, and Y contents. In contrast, the two-mica granite (G2) and fine-grained muscovite granite (G3), formed from 162.8 to 160.5 Ma, exhibit similar characteristics including enrichment in La, Y, Hf, Th, U, and depletion in Ba, Sr, and P. The porphyritic granite (G4) is the latest magmatic phase and formed at 158.3 Ma. It is characterized by high K, Si, Th, U, Zr, Hf contents but low Al, Fe, Sr, P, and Ti contents. These features support that four main phases of the Lianhuashan batholith belong to S-type granites that experienced significant fractional crystallization, and display reduced and low temperature features. Combined with previously published studies, we suggest that the Lianhuashan batholith formed in an intraplate extensional setting triggered by the high-angle rollback subduction of the paleo-Pacific plate. The three early phases (i.e., G1–G3) are in turn more oxidized and are responsible for the transition from Sn- to W-dominated mineralization. In contrast, the G4 granite, characterized by lower oxygen fugacity, is resposible for Pb-Zn-Ag-U polymetallic mineralization.

Study on the effect of Si content on the compatibility of F/M steels with lead-bismuth eutectic using small punch testing

This study investigates the impact of silicon (Si) on the corrosion resistance and post-corrosion toughness of ferrite/martensitic (F/M) steels in a liquid lead-bismuth eutectic (LBE) environment. Corrosion tests were performed on HT-9 and EP-823 (1.17 wt.% Si) steels at 550 °C for 1000 h under oxygen-controlled conditions. The resulting oxide layer consisted of an outer magnetite layer, a spinel layer and an inner oxide zone (IOZ). A Si-rich oxide layer was identified within the spinel and IOZ layers of EP-823, which slowed the growth rate of the oxide layer, enhanced antioxidant performance, and inhibited dissolution corrosion by the LBE. Post-corrosion mechanical properties were evaluated using a small punch test. Results showed a significant reduction in HT-9’s toughness within 240 h of corrosion, while EP-823 exhibited increased brittleness after 500 h due to Si-promoted carbide and Laves phase precipitation, significantly reducing its toughness.

Temperature dependent radiative and non-radiative recombination lifetimes of luminescent amorphous silicon oxynitride systems

In our previous work, we deeply researched the absolute photoluminescence (PL) quantum yields of luminescent modulating a-SiNxOy films with various N/Si atom ratios under different measurement temperatures. In this work, we further systematically studied the temperature dependent kinetic processes of radiative and non-radiative recombinations in a-SiNxOy systems in the visible light range. First, we investigated the structure of a-SiNxOy films and obtained the concentrations of both trivalent Si and N-Si-O defects related dangling bonds through XPS, FTIR and EPR measurements. Then we further tested the transient fluorescence attenuation of a-SiNxOy films detected at different emission wavelengths. We found that the PL lifetimes of a-SiNxOy films vary with the change of N-Si-O defect state concentrations, which is different from the typical PL decay characteristics of band tail related a-SiNx films previously reported. By combining the resulting PL IQE values with the ns-PL lifetimes, we further intensively redetermined the radiative and non-radiative recombination lifetimes of a-SiNxOy systems. The related radiative recombination rates were obtained (kr∼108 s−1), which can be compared to the results in the direct band gap.

Bacterial endophyte Pseudomonas mosselii PR5 improves growth, nutrient accumulation, and yield of rice (Oryza sativa L.) through various application methods

BackgroundPseudomonas spp. have drawn considerable attention due to their rhizospheric abundance and exceptional plant growth-promoting attributes. However, more research is needed on the optimal application methods of Pseudomonas mosselii for rice growth, nutrient accumulation, and yield improvement. This research explored the application of the endophytic bacterium P. mosselii PR5 on rice cultivar BRRI dhan29 with four treatments: control, seedling priming, root drenching, and bacterial cell-free culture (CFC) foliar application.ResultsPR5 led to better rice growth, improved nutrient acquisition, and higher yields compared to the control, regardless of the application method used. The highest results in fresh weight of root (146.93 g/pot), shoot (758.98 g/pot), and flag leaf (7.88 g/pot), dry weight of root (42.16 g/pot), shoot (97.32 g/pot), and flag leaf (2.69 g/pot), and grains/panicle (224.67), were obtained from seedling priming treatment, whereas root drenching resulted in maximum plant height (105.67 cm), root length (49.0 cm), tillers/pot (23.7), and panicles/pot (17.67). In all three application methods, rice grain yield per pot was higher in PR5 inoculated treatments, compared to the control. The amount of P, Mg and Zn in the shoot and N, P, Ca, Mg and Si content in the flag leaf was significantly increased along with effective suppression of naturally occurring blast disease in bacterial CFC foliar application, validated by multivariate analysis.ConclusionOur results indicated that rice seedlings priming with PR5 improved rice growth, yield and nutrient uptake, whereas CFC foliar application significantly increased the concentration of most nutrients in the rice plant and suppressed the naturally occurring rice blast disease. This research highlights the significant potential of P. mosselii PR5 in enhancing rice growth, yield, and nutrient uptake, particularly through seedling priming and CFC foliar application methods.

The Influence of Surface Segregation on the Anodizing of AlSi11Cu2(Fe) Diecastings

A positive segregation is usually formed on the casting surfaces produced by high-pressure die casting (HPDC). In diecast Al-Si-Cu alloy components, this segregation shows a higher content of Si compared to the nominal composition of the alloy and it drastically affects the anodizing response of the casting surface. In the present work, HPDC components were produced by AlSi11Cu2(Fe) alloy, grit-blasted, and then anodized in a sulfuric acid electrolyte at the temperature of -4.5°C. Before the anodizing process, some regions of the casting were also milled, in order to completely remove the surface segregation. Microstructural investigations were carried out on grit-blasted and milled surfaces to characterize the initial substrates before anodizing, and to study their effect on the growth of the anodic layer. Scratch and wear tests were also performed to investigate the surface mechanical properties after anodizing. The results show that the surface segregation and the rough surface present on grit-blasted substrate leads to the formation of a thin and homogeneous anodic layer. On the contrary, a thicker and scalloped oxide film is formed on the milled surfaces. After anodizing, grit-blasted surfaces show lower wear and scratch resistance than milled substrates. The presence of surface segregation prevents the thickening of the anodic layer, negatively affecting the surface wear resistance due to the reduced oxide thickness.

Silicate coprecipitation reduces green rust crystal size and limits dissolution-precipitation during air oxidation

Green rusts (GR) are mixed-valence iron (Fe) hydroxides which form in reducing redox environments like riparian and wetland soils and shallow groundwater. In these environments, silicon (Si) can influence Fe oxides’ chemical and physical properties but its role in GR formation and subsequent oxidative transformation have not been studied starting at initial nucleation. Green rust sulfate [GR(SO4)] and green rust carbonate [GR(CO3)] were both coprecipitated from salts by base titration in increasing % mol Si (0, 1, 10, and 50). The minerals were characterized before and after rapid (24 h) aqueous air-oxidation by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fe extended x-ray absorption fine structure spectroscopy (EXAFS), and N2-BET surface area. Results showed that only GR(SO4) or GR(CO3) was formed at every tested Si concentration. Increasing % mol Si caused decreased plate size and increased surface area in GR(CO3) but not GR(SO4). GR plate basal thickness was not changed at any condition indicating a lack of Si interlayering. Air oxidation of GR(SO4) at all % mol Si contents transformed by dissolution and reprecipitation into lepidocrocite and goethite, favoring ferrihydrite with higher % Si content. Air oxidation of GR(CO3) transformed into magnetite and goethite but increasing Si caused GR to oxidize while retaining its hexagonal plate structure via solid-state oxidation. Our results indicate that Si has the potential to cause GR to form in smaller particles and upon air oxidation, Si can either stabilize the plate structure or alter transformation to ferrihydrite.Graphical

Cement Composites Biodeterioration by Acidithiobacillus Thiooxidans

The focus of this work was to study the biodeterioration of special cement composites by sulfur-oxidizing bacteria Acidithiobacillus thiooxidans. The laboratory prepared cement composites that contained the selected additives - silica fume (a secondary raw material) and zeolite (a natural raw material), as partial replacements for the binder. The tests were carried out in laboratory conditions. During the experiments, changes to the pH values and the Ca and Si concentrations were observed in the liquid phases. Based on the achieved results, it can be concluded that concrete composites with partial replacement of the binder by silica fume and zeolite have a higher resistance to biogenic sulfuric acid.

The Influence of Fluoride Ions on the Forms of Lanthanide Migration in Natural and Polluted Waters of the Lovozero Massif (The Kola Peninsula)

A comprehensive study (monitoring, thermodynamic modeling) of natural and anthropogenically polluted waters of the Lovozero Massif has been carried out. A thermodynamic study of the weathering of the Lovozero Massif within the “water-rock-atmosphere” system at a temperature of 5 °C showed that the elements contained in the rocks of the studied massif influence the formation of the chemical composition of natural waters. It has been established that an increase in the degree of “water-rock” interaction leads to an increase in the concentrations of F−, Cl−, SO42−, and HCO3− in the solution. This affects the mobility of lanthanum, cerium, and other elements due to the formation of complex compounds with them. The relatively high content of fluorine, phosphorus, and HCO3− (weak and medium acids) in the solution promotes the dissolution of silicates while Si, Al, and P are released into the solution. Monitoring of water from a flooded mine in which there is an increase in the degree of interaction of water with rock showed higher pH values for the concentrations of Na, HCO3−, F−, P, Al, Si, V, U, La, and Ce. The conclusions are relevant in the context of the use of groundwater for drinking water supply purposes. The obtained information is useful to evaluate the health of the population of the region under study.

Modelling of blast furnace ironmaking process based on digital twin

AbstractThe blast furnace ironmaking process is a crucial step in the steel industry. Effectively modelling the blast furnaces is significant in ensuring smooth operation and accelerating the digitalisation transformation of blast furnaces. The authors focus on the mechanism modelling of the blast furnace operation process, using a digital twin model development platform to simulate the main reaction processes inside the blast furnaces. Under on‐site production conditions, Si, Mn and Ti contents of molten iron and the corresponding indicators for model accuracy are calculated. For Si, Mn, and Ti content, the Root Mean Square Error values are 0.0678, 0.0108 and 0.0093 for dataset 1, while 0.0933, 0.0120 and 0.0111 for dataset 2, respectively, indicating that the model has a small simulation error and high accuracy. By comparing the simulation results with accurate laboratory results, the model is validated to have satisfactory simulation reliability and compensates for the existing shortcomings in the blast furnace mechanism modelling field.

Geochemical constraints on reaction temperature and pressure and heat- and mass-transfer efficiency at Rainbow Hydrothermal Field

Seafloor vent fluids hosted by oceanic core complexes (OCCs) are thought to represent circulation of seawater-derived hydrothermal fluid along deeply penetrating, low-angle detachment faults. However, estimation of the source temperatures and pressures of such fluids has been limited because geochemical methods typically require vent fluid silica concentrations to be buffered by quartz, a condition not often met at oceanic core complexes. Here, we extend the calculation of the Si-Cl geothermobarometer to enable predictions of fluid Si concentrations in equilibrium with any Si-buffering mineral assemblage, rather than being restricted to quartz. We apply this method to Rainbow Hydrothermal Field vent fluid compositions and find that they are consistent with buffering by a plagioclase+talc+chlorite+tremolite mineral assemblage at conditions ranging from (430 °C, 359 bar) to (470 °C, 468 bar), which correspond to depths of 1.3–2.4 km below the seafloor. These estimates agree well with the locations of seismically imaged magma chambers within the Rainbow Massif. Additionally, calculations of fluxibility and Fe solubility support this relatively shallow origin for Rainbow vent fluids and imply relatively efficient heat and Fe extraction from the seafloor. We estimate that only 24–30 % of the heat content and almost no Fe is lost during upflow of Rainbow vent fluids.Compared to other OCC-hosted seafloor vents, the source region of Rainbow vent fluids is anomalously shallow, an observation consistent with geological interpretations of the Rainbow Massif. Vent fluids at Rainbow Hydrothermal Field have exhibited apparently stable and greater-than-seawater salinity for over two decades. We interpret these vent fluids as vapors derived from a higher-salinity source fluid that developed over multiple cycles of magma injection and phase-separation inherent to the formation of oceanic crust along slow-spreading, non-volcanic segments of oceanic spreading centers. Alternatively, higher-salinity source fluids could be derived from mineral hydration reactions associated with serpentinization of ultramafic rocks. The occurrence of greater-than-seawater salinity vent fluids is thus predicted to be a common feature of OCC-hosted vent fields, as indicated by several known examples, including the TAG, Kairei, and Edmond vent fields.

Study on the Microstructure, Mechanical Properties, and Corrosion Behavior of 900 °C-Annealed CoCrFeMnNiSix (X = 0, 0.3, 0.6, 0.9) High-Entropy Alloys

In this study, a series of CoCrFeMnNiSix (x = 0, 0.3, 0.6, 0.9) high-entropy alloys (HEAs) were prepared by suspension melting of cold crucible, annealed at 1000 °C, and then quenched at 900 °C. The changes in the microstructure of the HEAs after the addition of Si were analyzed using X-ray diffraction (XRD), metallographic microscope, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). The hardness, room-temperature friction, and wear behavior, room-temperature compressive properties, and corrosion resistance of the annealed CoCrFeMnNiSix HEAs were also studied. The results show that when the Si content is 0 and 0.3, the annealed CoCrFeMnNiSix HEA exhibits a single face-centered cubic (FCC) structure. As the silicon content increases, a face-centered orthorhombic (FCO) phase appears. At a Si content of 0.9, a hexagonal close-packed (HCP) phase is observed. After heat treatment, the hardness of the CoCrFeMnNiSix HEAs increases continuously with the addition of Si. The HEA with a Si content of 0.9 achieves the highest hardness of 974.8 ± 30.2 HV. The HEA with a Si content of 0.6 reaches the highest compressive strength and yield strength, which are 1990.3 MPa and 1327.5 MPa. When the Si content is 0.9, the HEA shows the smoothest surface after wear, with the best wear resistance, achieving a value of 0.21 mm−1. In the CoCrFeMnNiSix HEAs after 900 °C heat treatment, the HEA with a Si content of 0.6 exhibits the lowest self-corrosion current density of 0.23 µA/cm2 and the highest pitting potential of 157.65 mV, indicating the best corrosion resistance.

Geochemical characterization of trace fossil assemblages in spotted marls and limestones of the Lower Jurassic of the Western Carpathians: environmental implications

AbstractThe trace fossils of the spotted limestones and marls from upper Pliensbachian of the Skladaná Skala section, Western Carpathians (Slovakia), are characteristic of Zoophycos ichnofacies preserved in outer shelf deposits. The ichnoassociation is dominated by Lamellaeichnus and Chondrites, while Palaeophycus, Planolites, Teichichnus, Thalassinoides, Trichichnus, and Zoophycos, are less abundant. The presence of relatively large sized traces (reaching a decimetre in horizontal dimension for Thalassinoides and Zoophycos) and continuously well bioturbated deposits point to well oxygenated shallow zone (mixed layer) and deeper part of stiffed substrate of the transitional layer of bottom substrate up to the first tens of centimetres to depth. A first tier (tier I) corresponds to the shallowest sediment occupied by Bathysiphon tests and other epifaunal body fossils. The tier II is characterized by shallow infaunal burrows of deposit feeders (Planolites) and permanent dwelling, open burrows (Palaeophycus, Thalassinoides) located in a Ca-rich sediment (corresponding to CaCO3). The tier III is dominated by deposit feeders (Lamellaeichnus, Teichichnus) that burrowed stiff Ca-rich sediment below the redox boundary. Trace fossils of tier III are rich in fine siliciclastics (high content in Si, Al, K mainly associated to clays) and pyrite framboids (enrichment in Fe, S and Co). The deposit-feeders of tier III maintain connection to the sediment-water interface. Tier IV (Zoophycos, Teichichnus and large Chondrites), and deepest infaunal forms of the tier V. (Trichichnus, Pilichnus and tiny forms of Chondrites) comprises trace fossils commonly rich in pyrite framboids with relatively high content of Fe, S, and Co, congruent with chemosymbiotic behaviour commonly inferred for Chondrites, Trichichnus, and the organic-matter storage of Zoophycos.