High Si Research Articles

High‐Performance Yolk‐Shell Structured Silicon‐Carbon Composite Anode Preparation via One‐Step Gas‐Phase Deposition and Etching Technique

AbstractFor producing high‐capacity silicon (Si) anodes, a combined gas‐phase deposition and etching technique is developed to construct yolk‐shell structured silicon‐carbon composites. As a novel etching agent in battery field, NF3 is applied to selectively etch Si to tailor the architecture. Si particles as self‐sacrificed precursor have no need to build artificial or complex templates in advance, thereby greatly simplifying fabrication process and showcasing practicality. As a result, yolk‐shell structured silicon‐carbon composites are successfully fabricated in a single step. Sufficient buffer space between Si and carbon layer accommodates the significant expansion of Si during lithiation, preventing fracture of the carbon layer, which greatly improves service life of Si‐based anodes. Moreover, the refined particle size of Si and abundant pores in inner Si cores enhance the lithiation and de‐lithiation kinetic. Even with a high Si loading of 3.9 mg cm−2, the produced anode exhibits a superior areal capacity of 16.3 mAh cm−2 at 0.2 mA cm−2. Furthermore, at a high current density of 4 A g−1, it demonstrates an excellent capacity of 1114 mAh g−1 after 1000 cycles with a capacity retention of 96.3%. Additionally, with pre‐lithiation, it is successfully paired with an iron trifluoride cathode to construct high‐energy lithium‐ion batteries.

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.

Applicability of Waste from Al Industry toward Dephosphorization of Hot Metal in Primary Steel Making

Managing industrial waste is a global challenge. Red mud is a byproduct of the aluminum industry posing serious concerns. The presence of FeO and CaO in red mud makes it a potential DeP flux. Red mud has been utilized as a DeP flux in previous studies, but these studies deal with low Si content and no P2O5 content in the red mud. However, certain steel makers have high initial Si content (0.6–0.7 wt%) in the hot metal, and with increasing demand for low P steel, new dephosphorization fluxes need to be explored. Addressing this gap, this study investigates red mud's potential as a flux for dephosphorization in hot metal with elevated Si levels. Conducting slag–metal equilibrium experiments at 1350 °C, using red mud‐based fluxes, the research achieves a 40% dephosphorization degree under optimized conditions of double deslagging and fluxing. Analysis via wet chemical methods and inductively coupled plasma mass spectrometry confirms the effectiveness of the approach. Furthermore, thermodynamic calculations highlight the influence of O2 partial pressure and Si content on dephosphorization efficacy. Through laboratory experiments and theoretical insights, this study provides a valuable roadmap for leveraging red mud as a sustainable flux in hot metal dephosphorization processes, contributing to both waste management and steel production efficiency.

Insights into the environmental risk variation of heavy metals from MSWI fly ash after thermal plasma vitrification

Thermal plasma vitrification of municipal solid waste incineration fly ash (MSWI FA) shows potential for effective dioxin degradation and heavy metal immobilization. However, the environmental risks posed by heavy metals released after vitrification remain understudied. This work investigates two types of MSWI FA—circulated fluidized bed fly ash (CFA) and mechanical grate furnace fly ash (GFA)—blended with waste glass and vitrified via thermal plasma treatment. The physical and chemical properties of the original FA and vitrified glasses (CFA-glass and GFA-glass) were analyzed. Environmental risks were assessed using the risk assessment code (RAC) and the overall pollution toxicity index (OPTI). Results showed that CFA, with higher Si and Al content, exhibited better vitrification than GFA. Plasma vitrification reduced chlorine content from 5.79 % and 10.59 % to 0.22 % and 0.16% due to Cl volatilization. Heavy metals with low boiling points, such as Cd and Pb, were significantly reduced, while high-boiling-point Cr, Ni remained and the acid resistance of vitrificated FA significantly deteriorated, which increased the potential leaching of heavy metals. In alkaline conditions, the OPTI value of CFA-glass dropped to 2, indicating a strong immobilization effect. This study provides critical insights for managing heavy metals in fly ash through thermal plasma vitrification.

Real-time study of the interplay between phase formation and stress evolution at the W1−xSix/a−Si interface

Nanoscale W1−xSix layers with different Si content were deposited by magnetron sputtering on amorphous silicon layers. The structure and stress evolution during deposition were monitored and in real time. Thus, it was possible to disentangle different origins of stress built-up (interface formation, phase formation, grain growth, and texture) on the nanoscale. It was found that the bcc phase with a composition-dependent texture forms at low Si content (less than 10% Si), but only above a critical thickness. At intermediate Si content (13.9% and 16.5% Si), or low Si content and low thicknesses (≲4.5 nm), the β phase with A15 structure and coexisting phases (bcc or amorphous) form, while a single, amorphous phase is observed at high Si content (≳22% Si). An A15 formation driven by impurities (O,C,N) was excluded by combined x-ray photoelectron spectroscopy and x-ray diffraction measurements on a second sample series. calculations of substitutional bcc and A15 W1−xSix alloys support the formation of A15 at higher Si content. The A15-containing interlayer should be taken into account when discussing the superconductivity of W/Si multilayers. The stress evolution during deposition of W1−xSix was correlated with the microstructure evolution, and compared to similar observations for Mo1−xSix. Due to the crystalline phase (bcc/A15) and bcc texture ([111] and [110]) competition, the structure formation of W1−xSix shows a higher complexity. This explains the wide range of stress states (from tensile to compressive) observed after deposition of W1−xSix. Nanoscale W-Si based stress-compensation layers could be employed for tailoring the stress state of nonepitaxial semiconductor devices. Published by the American Physical Society 2024

High temperature stress relaxation behavior of high Si, Mo-doped austenitic stainless steels

The resistance to stress relaxation at high temperatures is of importance to fasteners. In this study, the stress relaxation behavior of high Si, Mo-doped austenitic stainless steels at 450, 510, 550, 600 and 650 °C were investigated, taking the microstructure evolution at high-temperature long-term condition into account. It is found that Mo can effectively mitigate the plastic strain rate at high temperatures by impeding the extension of partial dislocations, thus leading to a noteworthy enhancement in the stress relaxation resistance. The first-principles calculations indicated that the addition of Mo can suppress the formation of a multi-phase composed of G phase and ferrite at high temperatures, by increasing the segregation energy of Si, Cr, and Ni at grain boundaries. This multi-phase induces the formation of stacking faults and twins, and therefore is responsible for an abnormal reduction in the residual stress.

Supramolecular-driven construction of multilayered structure by modified hummers method for robust silicon anode

Rational design of nano-structured silicon (Si)-based composites to enhance the structural stability and electrical conductivity is key to developing high-performance lithium-ion batteries. Here, a supramolecular self-assembly strategy is first adopted to prepare Si@rGO composites with multilayered structure through the modified Hummers method. Experimental results demonstrate that Si@SiOx NPs are uniformly distributed in rGO interlayers by supramolecular interaction. In situ Raman results suggest that the multilayer embedded structure can effectively confine the Si NPs and preserve the integrity of the electrode. Theoretical calculations indicate that the imbalanced charge distribution in inner interface shows enhanced dual-interfacial bonding and charge interactions in the Si@SiOx⊂rGO composite, resulting in an interfacial electric-field between Si NPs and rGO for fast ionic and charge migration. The fabricated MSi@SiOx⊂rGO anode with high Si contents (> 60 wt.% Si) exhibits superior Li-ion reaction kinetics (882.4 mAh g−1 at 8 A g−1), durable structural stability (0.031% per cycle capacity attenuation with an average Coulombic efficiency > 99.7%), and low expansion rate. High-mass-loading electrodes show great potential for commercial applications. Full cells assembled with LiCoO2 cathodes also demonstrate outstanding Li-ion storage properties. This work provides insights into the interfacial design of Si@C anodes for advanced Li-ion battery.

Influence of Si on the Elevated-Temperature Mechanical and Creep Properties of Al–Cu 224 Cast Alloys during Thermal Exposure

The influence of Si content (0.1–0.8 wt.%) on the development of precipitation microstructures and the resultant mechanical and creep properties during thermal exposure, up to 1000 h at 300 °C, in Al–Cu 224 cast alloys, was systematically investigated. The room and elevated temperature yield strength (YS) increased with increasing Si content under the T7 condition, which was attributed to the fact that the Si promoted the precipitation of fine θ′. However, Si increased the coarsening of θ′ during thermal exposure at 300 °C, and the alloys with low Si exhibited a higher YS and creep resistance at elevated temperatures than high Si alloys. The mechanical strength and creep resistance were mainly controlled by the precipitation strengthening of the predominant θ′ phase. Because of the high mechanical strength and creep resistance of the 0.1Si alloy during long-term thermal exposure, the Si level in Al–Cu alloys should be maintained at a low level of 0.1 wt.% for high-temperature applications. The strengthening mechanisms were quantitatively analyzed, based on the characteristics of the precipitate. The predicted YS values under different exposure conditions agreed well with the experimentally measured values.

International Simple Glass (ISG) dissolution rate in a (Si, Ca)-rich environment at 90 °C and alkaline conditions

The dissolution of International Simple Glass (ISG) was investigated at 90 °C and alkaline conditions with various concentrations of dissolved Si and Ca to unravel the combined effects of those elements on ISG reactivity. Experiments were conducted over durations ranging from 20 days to 3 months. Through morphological, structural, and chemical characterizations, the glass dissolution rate was proven to be strongly correlated with the activity of dissolved silica in the solution. While dissolved calcium did not significantly impact the dissolution rate, precipitation of calcium silicate hydrates (CSH) during the experiments enhanced ISG dissolution rate, though to a modest extent. The 3-months experiments highlighted the strong correlation between the dissolution mechanism and the evolution of the nature of secondary phases in saturated solution. During the first 20 days and at high Si and Ca concentrations, CSH precipitated and aggregated, without preventing the passivating impact of the gel layer at the surface of the glass: the dissolution was controlled by diffusion. Then, a resumption of dissolution occurred between 19 days and 76 days, corresponding to the CSH growth, and a possible mechanistic switch to a hydrolysis-controlled reaction rate. Finally, in some experiments, a drop in pH due to carbonate precipitation was observed along with a decrease in the dissolution rate, falling back in a diffusion-limited regime. Overall, this study shows that at 90 °C, pH = 10 and concentrations of SiO2(aq) exceeding 50 % of saturation with respect to amorphous silica, irrespective of Ca concentration but in presence of CO2(aq), ISG exhibits a very good chemical durability.

Slowly Rotating Peculiar Star BD00°1659 as a Benchmark for Stratification Studies in Ap/Bp Stars

We present the results of a self-consistent analysis of the magnetic silicon star BD+00°1659, based on its high-resolution spectra taken from the ESPaDOnS archive (R = 68,000). This narrow-lined star shows the typical high Si abundance and Si ii– iii anomaly, making it an ideal prototype for investigating the vertical distribution of Si and Fe in the stellar atmosphere. The derived abundances, ranging from helium to lanthanides, confirm the star’s classification as a silicon Bp spectral type. Silicon and iron are represented by lines of different ionisation stages (Fe i– iii, Si i– iii), indicating an ionisation imbalance interpreted as evidence of atmospheric stratification. Our stratification analysis reveals that there is a jump in iron and silicon abundances of 1.5 dex at atmospheric layers with an optical depth of logτ5000 = −0.85–−1.00. Non-LTE calculations for iron in this stratified atmosphere show minor non-LTE effects. Our results can be applied to studying the impact of stratification on the emergent flux in rapidly rotating Si stars with similar atmospheric parameters and abundance anomalies (for example, MX TrA), where direct stratification analysis is challenging due to line blending.

Extractable soil silicon in relation to sugarcane yield on mineral soil

Florida sugarcane production is mostly on organic soils, but the cultivation area on mineral soils is also expanding. Silicon (Si) is beneficial for sugarcane growth and development on weathered soil. However, the low solubility and availability of soluble Si is an issue in Florida’s mineral soils. This study aimed to assess soil Si extraction methods based on sugarcane yield response to calcium silicate application. It also examined the relationship between sugarcane yield with extracted plant-available soil Si, alongside plant Si concentrations. The experiment followed a randomized complete block design involving 2 fields, with 24 plots each, and 6 replications. Four rates of calcium silicate (0 control, 2.24, 4.48, and 6.67 Mg ha−1) were applied before planting sugarcane. Soil samples were collected prior to planting and after each harvest. Soil Si was extracted using 0.5 M acetic acid, 0.7 N NH4OAc, Mehlich 3, and 0.01 M CaCl2 extractants. Leaf samples were collected over a three-year sugarcane life cycle (from 2019 to 2022) to evaluate the relationship between soil Si and leaf Si concentrations. The relationships between parameters were analyzed using linear and nonlinear regression models. Results indicated that higher Si application rates increased Si concentrations in sugarcane leaves in both fields. However, only one field showed a yield response to Si, likely due to high pre-plant soil Si in the other field. The best extractant should correlate strongly with either yield or leaf Si content, but no single extractant showed a strong correlation with either, making it infeasible to identify the best extractant.

Synergy Effect of High K-Low Ca-High Si Biomass Ash Model System on Syngas Production and Reactivity Characteristics during Petroleum Coke Steam Gasification

The synergy effect of high K-low Ca-high Si biomass ash-based model system (BAMS) on the synthesis gas output and reaction characteristics of petroleum coke (PC) steam gasification process was studied using three biomass ash (BA) components, KCl, SiO2, and CaCO3, which were used as the model compounds. In the ternary model system, the steam gasification experiment of PC was conducted using a fixed bed reactor and gas phase chromatography. The synergistic effects of binary and ternary components in the ternary model system on the gasification of PC were obtained. These investigations were based on the data from the gas analysis and examined the gasification reaction process, syngas release behavior, and reaction characteristics. This study examined the effects of binary and ternary components in the ternary model system on the evolution of semi-char structure during PC gasification. This correlation revealed the synergistic effect of the model system on PC gasification. Scanning electron microscope (SEM) and Raman spectroscopy were used to characterize the structure and surface microstructure of the gasification semi-char. The results showed that the yields of different gases in the ternary model system were in H2 > CO > CO2. Compared with single PC gasification, the yields of H2, CO, syngas, and carbon conversion were increased by 29.42 mmol/g, 20.40 mmol/g, 56.68 mmol/g, and 0.35, respectively. All other components in the ternary model system with high K-low Ca-high Si demonstrated catalytic effect, except for SiO2 and the Ca-Si system, which showed inhibitory effects on syngas release and reaction features. Integrating SEM and Raman spectroscopic analyses, it was elucidated that CaCO3 and KCl diminished the degree of graphitization in semi-char through interactions with the carbonaceous matrix. This phenomenon facilitated the gasification process and exhibited a synergistic effect. Secondly, SiO2 will react with CaCO3 and KCl, producing inert silicates and inactivating these compounds, leading to the decline of catalysis.

High-Performance CsPbI3 Quantum Dot Photodetector with a Vertical Structure Based on the Frenkel-Poole Emission Effect.

The selection of photoactive materials and the design of device structures are critical to the photoelectronic performance of photodetectors. This study reports on a vertically structured photodetector device with rapid, stable, and efficient photoelectric performance across the UV-visible broadband range based on the Si++/SiO2/Au/single-layer graphene/CsPbI3 quantum dots (QDs) configuration. In this specific device structure, a relatively high conductivity Si++/SiO2 wafer was used as the substrate, a CsPbI3 QD film with high light absorption was used as the photoactive layer, and a monolayer graphene with high conductivity was inserted between the substrate and the CsPbI3 QD film to form a heterojunction with the QD film. Based on the Frenkel-Poole emission effect arising from the high trap state density within the SiO2 layer, the device exhibited excellent photoelectric performances. Especially at a wavelength of 365 nm, a photocurrent responsivity of 2319 A/W, a specific detectivity of 1.15 × 1014 Jones, an external quantum efficiency of 7883%, and an on/off time of 39/36 ms at a Si++ terminal voltage of -80 V and an optical power density of 84.03 nW/cm2 can be achieved.

Enhanced steam thermal cycle resistance of Yb2Si2O7 environmental barrier coatings via Al modification

SiC-based ceramic matrix composites are susceptible to performance losses in steam environments, necessitating the use of environmental barrier coatings for their protection. The high Si activity of Yb2Si2O7 material may induce the emergence of Si(OH)4 in steam environments, resulting in the development of a pore structure within Yb2Si2O7. This pore structure weakens the service life of the coating, highlighting the importance of enhancing the steam corrosion resistance of environmental barrier coatings as a key factor in improving their overall longevity. In the present study, we employed Al modification technique to improve the steam corrosion resistance of Yb2Si2O7 coatings. The results indicated that Al-modified Yb2Si2O7 coatings exhibited superior steam thermal cycle corrosion resistance compared to the non-modified Yb2Si2O7 coatings after testing performed at 1523 K for 1000 h (10 h per cycle). This improvement was attributed to the presence of Yb3Al5O12 and Al2O3 composite phases within the Al-modified Yb2Si2O7 coatings, which exhibited low steam activity and effective steam corrosion resistance. Moreover, Al-modified Yb2Si2O7 coatings obtained the dual excellent performance of improving the steam corrosion resistance of Yb2Si2O7 coating and not weakening the thermal cycle ability, providing a guarantee for the longer life of Yb2Si2O7 coating.

Biomass ash (BA) waste as an activator to produce carbon-negative cement

The use of biomass, as a renewable energy source, to run heating and power plants is propelled by sustainable European policy. Olive is an important resource in Mediterranean countries. The residues from the extraction of olive oil are used as biomass, either to produce the oil or to generate heat or electricity. The disposal of ash residue poses an important burden. This study uses olive pit bottom ash waste (OBA) to produce carbon-negative cement. The OBA is mixed with waste GGBS (GGBS), and neither calcination nor thermal curing are used to lower environmental impact.The cements produced contain up to 60 %OBA and have a carbon sequestration capacity up to -97.45 kg CO2e/m3. An optimum mix with 40 %OBA is developed (using auxiliary activator), with compressive strength of 36–44 MPa and a carbon sequestration capacity of 40–45 kg CO2/m3. A modified loss on ignition test is proposed to evaluate the embodied carbon of biomass ash.The OBA's main chemical constituents: K2O and CaO, afford outstanding activation and alkalinity to release Ca2+ Si4+ and Al3+ from GGBS to form calcite, hydrotalcite, C-(A)-S-H and amorphous cements. Using sodium carbonate (NC) and lime as supplementary activators enhanced the mechanical properties of the cements and slightly changed their composition and microstructure. NC is the most efficient activator, it increased dissolution, and produced a denser and stronger cement with higher Si and K concentration that includes gaylussite, N-A-S-H and C(K)-A-S-H. Pre-dissolving the NC prior to mixing increases the activator's efficiency, producing less calcite cement for the same amount of NC. By adding 4 % pre-dissolved NC, the compressive strength increased by 138.76 % (compared to OBA-GGBS mortar without auxiliary activators) and 113.94 % compared to the material with NC in powder form.

Novel Abietane type Sugar Triazole Hybrids and Amides against SARS‐CoV‐2 Spike Glycoprotein and Influenza A Virus

Abietane type diterpenic (dehydroabietic, 2,3‐dihydroquinopimaric and maleopimaric) acids were converted by the acid chloride method into a series of aliphatic and heterocyclic amine spacered conjugates. A number of structurally novel derivatives holding 1,2,3‐triazole moieties were designed and synthesized by treating of the propargylated amides and esters with a sugar azides using the Cu(I)‐catalyzed click chemistry approach. The synthesized N‐containing diterpene derivatives were tested for their potential inhibition of influenza A/PuertoRico/8/34 (H1N1) virus in MDCK cell culture and SARS‐CoV‐2 pseudovirus in BHK‐21‐hACE2 cells. Among tested forty‐five compounds ten derivatives were the most efficacious against influenza virus A with IC50 0.7‐63.4 μM together with high selectivity index SI value from 11 from 94. Dihydroquinopimaric acid N‐ethylpiperazine‐amide and dehydroabietic acid 1,2,3‐triazoles spacered with glucose and lactose showed anti‐SARS‐CoV‐2 pseudovirus activity with EC50 values of 1.79‐25.46 µM. Molecular docking and dynamics modeling investigated the binding mode of the lead compounds into the binding pocket of influenza A virus M2 protein and the RBD domain of SARS‐CoV‐2 spike glycoprotein.

Valorization of oil‐based drilling cuttings as a substitute for bauxite in fracturing proppants application

AbstractThis study aimed to increase the scale of oil‐based drilling cuttings (OBDCs) resource utilization in the ceramic industry. The sintering process and mechanism were explored based on the analysis of physicochemical properties, phase transitions, and microstructure. The results showed that (1) The main ceramic‐technological characteristics of the OBDC were determined, which belonged to high‐silica solid waste with a high Si–Al ratio and a low acid–base ratio of oxides. (2) The low meltability temperature of the OBDC could largely influence the determination of the sintering temperature range for ceramic products. (3) The chemical components OBDC provided were involved in the formation of molten phases, which could affect dimensional accuracy and mechanical properties. Meanwhile, the dolomite promoted the formation of closed pores and enhanced lightweight performance. (4) Before 800°C, dolomite decomposed and reacted with SiO2 to form silicate, and then a new feldspar crystal appeared. After 1000°C, orthoclase completely melted into the molten phase, only two phases of quartz and diopside existed in the material until 1150°C. When the temperature was higher than 1350°C, the glass transition of the phase was basically intensified. (5) In the analyzed scenarios, the results indicated OBDC can only be doped in low contents and degrades the ceramic material properties.

Infrared optical properties of SiGeSn and GeSn layers grown by molecular beam epitaxy

The infrared optical properties of thick GeSn films (>500 nm) having 10% Sn concentration and of SiGeSn layers, utilized for the growth of strain-relieved, direct-gap GeSn films by molecular beam epitaxy, are investigated. Two growth methods are used: a graded-growth structure and a stepped-growth structure that help us to illustrate the properties of the GeSn and SiGeSn layers. Interestingly, there can be strong absorption in SiGeSn films throughout the infrared. We observe an increase in infrared absorption with increasing Sn concentration up to 21% Sn and in films, where the Sn is held constant at 18%, with increasing Si concentration up to 30%. Cavity effects in the infrared transmission measurement of stepped-growth structures are observed and associated with reflections at growth interfaces. Si–Si bond formation is proposed to occur at high Si concentrations in SiGeSn films, and the bandgap in SiGeSn films appears to decrease with increasing Si and Sn concentrations.

Soil silicon availability and silicon uptake by winter wheat in Tokachi district, Hokkaido

ABSTRACT Silicon (Si) is the second most abundant element in soils and is a beneficial element for plant growth, particularly for gramineous plants such as rice, corn, and wheat. In Japan, soil Si availability and its relationship with Si in plants have been mainly focused on paddy soils and rice. Although Si has also been reported to benefit wheat production via enhanced phosphorous uptake and resistance to diseases, there is little study on Si availability in agricultural soils related to wheat production in Japan. The objectives of this study were to (1) assess the soil available Si and its relation to other soil properties in upland fields, (2) evaluate Si concentration and its distribution in winter wheat, (3) clarify the relationship between the soil available Si and the Si concentration in wheat, and (4) identify suitable methods to determine available Si for agricultural soils. Surface soil and wheat samples were collected from 40 growers’ field along four different river terraces including lowland, low terrace, middle terrace, and high terrace of the Tokachi district in 2020 and 2021. Soil available Si was evaluated by three methods using acetate buffer and phosphate buffer solution. The soil available Si contents in agricultural soils varied from field to field considerably, and were remarkably larger in the fields located on the middle and high terraces compared to the lowland and the low terrace, suggesting the effects of soil parent materials and pedogenic factors, particularly volcanic ashes and amorphous clay minerals. The mean Si uptake by winter wheat was 13.4 g m−2 and comparable to N and K uptake and greater than P. Winter wheat mainly stores Si in culms, leaves and husks, and the highest mean concentration of Si in above-ground part of winter wheat was 27.6 g kg−1 in husks. The high Si concentration in the husk may be related to enhancing plant physical protection to preharvest sprouting and fungal diseases. Among three methods, the acetate buffer solution method could be the most promising method to determine soil Si availability in agricultural soils of the studied area.

Study of bainite and martensite tempering in a medium C high Si steel. microstructural disparities and equilibrium convergence

This study investigates the tempering behavior of bainite and martensite in a medium carbon, high silicon steel, with a focus on the microstructural evolution and the attainment of equilibrium, over a temperature range of 200–650 °C. The dissimilarities between the characteristics of the two initial microstructures, both comprising a C-saturated tetragonal ferrite matrix and retained austenite, are reflected in the differences observed in their evolution towards equilibrium as the tempering temperature increases. Therefore, while retained austenite plays a pivotal role in the bainitic microstructure, in the martensitic microstructure it is the ferritic matrix, which is highly dislocated and enriched in carbon, that plays a determinant role. The findings demonstrate that while both bainite and martensite can converge towards the same equilibrium state upon high-temperature tempering (600–650 °C), the pathway to this convergence is markedly different, with bainite exhibiting a slower transformation rate. This path to equilibrium has been characterised by means of high-resolution dilatometry, scanning electron microscopy and detailed X-ray diffraction analysis. This has provided a dynamic and detailed picture of the most relevant microstructural changes and tempering mechanisms in high silicon steels. It has also provided a foundation for tailoring heat treatment processes to optimise the mechanical properties of advanced bainitic and martensitic steels.