Mixture Of Si Research Articles

Mineral Heterostructures for Simultaneous Removal of Lead and Arsenic Ions

This study focuses on Pb2+ and As(V) adsorption on mineral heterostructures based on a mixture of Si, Fe, and Ti oxides (MOHs). Various techniques were performed to analyze the morphological and structural properties of the synthesized metal oxide samples. In addition to the experimental optimization of the parameters determined by the response surface method (RSM), the effects of pH, adsorbent dosage, temperature, and contact duration on the batch and column system adsorption efficiency of single-component and simultaneous lead and arsenate removal were tested. The pseudo-second-order kinetic model and Weber–Morris model were more relevant to the adsorption on the metal(loid)s. The adsorption of Pb2+ was related to the Langmuir isotherm model, while the adsorption of As(V) was fitted to the Freundlich isotherm model. The thermodynamic parameters indicate the spontaneity of the adsorption process with a low endothermic character. The MOHs were more effective in removing Pb2+ and As(V) in the multi-component system (87.7 and 46.1%, respectively) than in the single-component system (56.3 and 23.4%, respectively). This study demonstrates that mineral heterostructures can be effectively used to remove cations and anions from water systems, and due to their fast kinetics, they can be applied to the needs of rapid interventions after pollution.

Evaluating the efficacy of strategies for silicon/graphite anodes in Li-ion batteries

Recent research has been focused on the utilization of silicon (Si) based anode for high-energy–density lithium-ion batteries (LIBs) owing to the high theoretical capacity of Si (∼ 3578 mAh g−1). To mitigate the intrinsic volume change of Si (∼ 300 %) upon cycling, research focused on the co-utilization strategy of Si with graphite anode (SiG) in the form of the blending (physical mixture of Si and graphite) and composite (building up material containing Si and graphite). However, the underlying mechanisms of the two strategies that cause different electrochemical results have not been thoroughly explored. In this study, we aimed to investigate the composite anode (C-SiG-650) and blending anode (B-SiG-650) with a specific capacity of ∼ 650 mAh g−1 in terms of electrochemical performance. The composite electrode exhibited a uniform distribution of SiG particles, which helps for faster Li+ ion transport into bulk, whereas the blending electrode exhibited aggregation of SiG particles, which impedes the Li+ ion transport into the bulk. As a result, the composite anode exhibited superior capacity retention and rate performance compared to the blending electrode. Moreover, the composite anode containing full-cell delivered a higher specific capacity of 162 mAh g−1 and capacity retention of 73.58 % after 100 cycles. This implies that directly utilizing composite anode with a low-capacity SiG particle is a promising way to achieve high volumetric energy density for commercial device applications.

Silicon kerf loss as a potential anode material for lithium-ion batteries

In this work, industrially processed silicon kerf loss (abbreviated to silicon kerf) from the photovoltaic industry is assessed as an anode material for the lithium-ion battery (LIB). The study includes both a characterization of processed silicon kerf from different sources and a comparison with commercially available nano-sized silicon (40 and 100 nm) in electrochemical testing. Such a direct comparison between these two silicon types in electrochemical testing provides a new insight into silicon kerf as an anode material. The silicon kerf particles are flake-like with varying lengths, with a mean particle size (d50) measured to ∼700 nm and a dimension of thickness of a few tens of nanometers. However, the specific surface area ranging from 20 to 26 m2/g is comparable to that of a silicon material of size ∼100 nm. The silicon oxide layer surrounding the particles was measured to 1–2 nm in thickness and, therefore, is in a suitable range for the LIB. In terms of electrochemical performance, the silicon kerf is on par with the commercial nano-sized silicon, further supporting the size evaluation based on the specific surface area considerations. Initial discharge capacities in the range 700–750 mAh/g (close to the theoretical value for the 12 wt% Si mixture with graphite) and first cycle efficiencies of 86%–92% are obtained. The cycling stability is comparable between the two materials, although the differential voltage analysis (DVA) of the galvanostatic data reveals that only the silicon kerf samples maintain silicon activity beyond 120 cycles. This study shows that industrially processed silicon kerf has characteristics similar to nano-sized silicon without reducing the size of the silicon kerf particles themselves. Considering its low carbon footprint and potentially lower cost, it can thus be an attractive alternative to nano-sized silicon as an anode material for the LIB industry.

INFLUENCE OF SINTERING TEMPERATURE ON THE STRUCTURAL OF Mg2Si0.3Sn0.7 ALLOY PREPARED BY POWDER METALLURGY

The efficiency of energy consumption can be improved by reducing the heat lost during the combustion process of automotive engines. By converting waste heat energy into other energy sources that can be used directly, efficiency can be achieved. Mg2Si0.3Sn0.7 is a metal alloy that has the potential to convert waste heat into power. In this research, we used the powder metallurgy method to synthesize the Mg2Si0.3Sn0.7-based alloy. A mixture of Mg, Si, and Sn powders that had been milled for 2 hours was insulated in the stainless-steel tube to avoid oxidation and combustion. Heat treatment was conducted with temperature variations of 700, 750, and 800°C for 4 hours to investigate the influence of sintering temperature on the crystal structure of the Mg2Si0.3Sn0.7-based alloy. The microstructure and formation of the material were examined using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). Based on XRD analysis, it was found that the Mg2Si0.3Sn0.7 phase and a small amount of magnesium oxide (MgO) phase have formed. Due to the phase transition from Mg2Si0.3Sn0.7 to Mg2Sn at a sintering temperature of 800°C, the cubic lattice constant -a changes from 0.6631 nm to 0.6765 nm.

Low‐temperature curable adhesive for joining SiC/SiC components: Their application in wide range of temperatures

AbstractHerein we report the formulation of phenolic resin–based adhesive to join SiC substrates for a wide range of application temperatures. The formulation consists of phenolic resin as a binder and a mixture of B4C, Al2O3, Y2O3, Si, and SiO2 powders as active filler. The X‐ray diffraction, thermogravimetric analysis, porosity, and scanning electron microscopy analysis were carried out to understand the reactions occurring within this adhesive during its exposure to application temperatures. These results were also used to understand thermal stability and morphological changes that are involved in the formulated adhesive during its application. The shear strength values of lap joints of SiC substrates made with this phenolic adhesive after exposure to temperatures between 200 and 1500°C were studied to evaluate its adhesive capacity. Obtained SiC joints with this adhesive have shown an excellent lap shear strength value of 24 MPa after its cure. These joints were also found to be intact with good shear strength values of more than 5 MPa even after exposure to temperatures ranging from 200 to 1500°C. The results further confirm that the adhesive is potentially viable for joining SiC segments for their application at a wide range of temperatures in oxidative environments.

Flame-sprayed MgAl2O4- and calcium aluminate-based coatings for application in the aluminium industry

The aluminium industry is a major consumer of refractories with increasing wear by fluxes, the use of oxy-fuel burners, higher furnace temperatures, higher amounts of alloying Mg and recycled Al metal as well as a requirement for higher efficiencies. Today, most furnaces are lined with aluminosilicate-based materials. The reactions between the aluminosilicate and the metal lead to the formation of a mixture of Si, Al, and Al2O3 with unreacted refractory material, which has to be removed as they negatively affect the thermal properties of the refractories and the efficiency of the furnace. To reduce the penetration of Al into the refractory material, non-wetting additives such as barium sulphate, different types of fluorides, and CaO were used. The aim of this study was the investigation of different calcium aluminate-based coatings to reduce the wettability of a metallic substrate by molten aluminium. Feedstock composed of calcium magnesium aluminate CMA, calcium di-aluminate CA2, and CA/CA2 with and without TiO2 were characterised and processed via powder and flame spraying to thin coatings on metal substrates. The spraying parameters have been optimized and the phase composition, roughness, macro- and microstructure, porosity, and bending strength of the coatings have been analysed. Additionally, a finger test, as well as a casting test, have been performed by pouring 1.5 kg AlSi7Mg alloy at 800 °C over coated half-pipes using pure alumina as reference coating. The amount of residual Al sticking on the substrates after the casting test indicates the degree of wetting of the coatings. The thermally sprayed CMA and CA2 powder feedstock showed the lowest degree of interaction with the aluminium melt.

Atomistic insights into bias-induced oxidation on passivated silicon surface through ReaxFF MD simulation

The study investigated the bias-induced oxidation through ReaxFF molecular dynamics simulations in order to bridge the knowledge gaps in the understanding of physical–chemical reaction at the atomic scale. Such an understanding is critical to realise accurate process control of bias-induced local anodic oxidation nanolithography. In this work, we simulated bias-induced oxidation by applying electric fields to passivated silicon surfaces and performed a detailed analysis of the simulation results to identify the primary chemical components involved in the reaction and their respective roles. In contrast to surface passivation, bias-induced oxidation led mainly to the creation of Si–O–Si bonds in the oxide film, along with the consumption of H2O and the generation of H3O+ in the water layer, whereas the chemical composition on the oxidised surface remained essentially unchanged with a mixture of Si–O–H, Si–H, Si–H2, H2O–Si and Si–O–Si bonds. Furthermore, parametric studies indicated that increased electric field strength and humidity did not significantly alter the surface chemical composition but notably enhanced the bias-induced oxidation, as indicated by the increased number of Si–O–Si bonds and oxide thickness in simulation results. A good agreement is achieved between the simulation and experimental results.

High-permeability Fe-based soft magnetic composite comprising anisotropic Fe-Si chip fillers

Here, we demonstrate a novel hybrid soft magnetic composite (SMC) comprising highly-ductile pure-Fe powders and anisotropic Fe-6.5wt%Si chips to capture both high density and soft magnetic properties including high permeability and low core loss. Thin Fe-6.5wt%Si chips with dimensions of 2 mm × 0.5 mm × 0.04 mm were continuously fabricated through melt spinning using grooved copper wheels, and uniform and dense SiO 2 surface insulation coatings on the Fe powders and Fe Si chips were achieved through solution-based sol-gel process. Then, the hybrid SMCs were fabricated through compaction molding of pure Fe powder and Fe Si mixtures with various mixing ratios. Degree of alignment of Fe Si chips and packing density of the hybrid SMCs depending on powder-to-chip mixing ratio were systematically investigated, and their effects on the soft magnetic properties were thoroughly evaluated. Finally, the hybrid SMC with optimum powder-to-chip mixing ratio of 6:4 showed highest permeability of 472 and core loss of 157.34 W/kg (at 1 T and 1 kHz), which are 22.25% higher, and 51.05% lower values than those of pure-Fe SMC, confirming the effectiveness of Fe Si chip fillers in the enhancement of soft magnetic properties of SMCs. • Novel Fe-based SMCs comprising anisotropic chips has been introduced. • High density (>95%) hybrid SMCs with various powder-to-chip ratio were demonstrated. • Fe Si chip fillers significantly lowers coercivity (by 59%) and increases permeability by 29% of the SMCs. • Hybrid SMCs showed 52% decreased core loss from that of the pure-Fe SMC.

Carbon ion beam induced chemical modification and nano-pyramid growth on Si surface

We report the growth of nano-ripple on, initially smooth Si surface due to chemically guided additional instability generation during 10 keV C+ bombardment at grazing (70°) ion incidence. Also, the transformation of the ripple structure to triangular nano-pyramidal structure at higher ion fluence is investigated in details. It is shown that the chemical nature of the surface changes due to silicon carbide formation at the ion impact sites, and the surface becomes a mixture of Si and SiC. The differential sputtering of Si from pure Si and SiC, generates an additional instability which leads to trigger the ripple pattern on the surface. The variation of height amplitude, lateral correlation length and slope angles of the developed structures are investigated and explained in terms of existing continuum theory. At very high ion fluence the transformation of the structure into three dimensional triangle (pyramidal) is revealed and the mechanism is explained in the light of variation of local ion impact angle and its consequent effects.

The effect of intra-molecular bonds on the liquid-liquid critical point in modified-WAC models.

To obtain a better understanding of liquid-liquid critical points (LLCPs) in one-component liquids, we extend the modified-WAC model by E. Lascaris, Phys. Rev. Lett. 116, 125701 (2016) which is known to have a LLCP. The original WAC model is a model for silica (SiO2) and consists of a mixture of non-bonded Si and O ions. By adding explicit intra-molecular Si-O bonds to the model, we are able to study how several parameters (Si-O bond length, O-Si-O angle, and bond stiffness) affect the existence and location of the LLCP. We find that for this model, only the Si-O bond length has a strong effect on the LLCP, while the bond angle and bond stiffness have no significant effect on the LLCP. An analysis of the relevant coordination numbers indicates that increasing the bond length decreases the ratio RSi/O of additional Si ions per additional O ion in the first coordination shell of the Si, which causes the LLCP to move to higher, more accessible temperatures. The behavior of the RSi/O parameter shows a strong correlation with the behavior of the LLCP and might be a useful tool to determine if a LLCP exists at low, hard-to-reach temperatures in other models.

Carbon Encapsulated Silicon for High-Capacity Durable Anodes

One of the biggest challenges of the near future is how to meet the increasing energy demand without any adverse environmental impact. Lithium-Ion batteries (LIBs) are one of the promising alternative energy storage systems to replace conventional non-rechargeable batteries. LIBs are becoming one of the most widely used energy storage devices because of their relatively high specific energy density (~300 Wh/kg), excellent stability over a wide temperature range, and lower cost than other battery systems. Intense research is in progress to increase the capacity of anode electrodes for realizing high-energy LIBs. In this context, silicon (Si) has a great potential to replace commercial graphitic anode active materials mainly due to its high theoretical specific capacity (4200 mAh/g) and low working potential (0.37 to 0.45 V vs. Li/Li+). To harness and maintain a high capacity from Si-based anodes, we must deal with two main challenges: (i) volume changes of Si (>300%) during charging and discharging, which cause pulverization of the material and loss of electrical contact, and (ii) unstable growth of solid-electrolyte interphase (SEI) layer, which can cause early degradation of performance in Si-anode batteries. To overcome these challenges, different approaches have been taken. This includes developing graphite/Si anodes with limited amounts of Si (<30 wt.%), conformal coating of Si active materials (e.g., CVD carbon coating), etc. However, these challenges still could not be fully overcome.To advance the use of Si materials in LIB anodes, we developed a viable technology to create a hybrid silicon-carbon material, called Si@C, in which a soybean-derived carbon cloud protects Si nanoparticles during the battery operation. We employed soybean oil in a scalable oil-in-water emulsion polymerization technique to produce Si-containing polymeric particles. In this method, we emulsified two immiscible solutions. One contains a homogeneous Si mixture in epoxidized soybean oil (ESO), and another contains a uniform dispersion of ball-milled lignin or soyhull powders in water. Citric acid, a crosslinking agent, was used to help polymerize the ESO and integrate carbon-rich lignin/soyhull with polymerized particles. The final Si@C product was achieved by carbonizing the polymerized solid product at 500 °C (under argon) and ball milling to get a fine powder. Several Si@C hybrid materials containing 20 wt.% to 50 wt.% Si were successfully prepared and utilized for anode preparation. Electrodes were made by coating a slurry of Si@C active material, carbon black, and binder with a mass ratio of 60:20:20 onto an ion-permeable Bucky Paper (BP, a flexible and conductive paper made of carbon nanotubes). Anodes with different binding systems were prepared to determine an appropriate binder for Si@C based batteries. The 2032-type coin cells were assembled for battery testing using 1M LiPF6 in EC:DMC in a volume ratio of 1:1 as the electrolyte, Li chips as the counter electrode, and Celgard 2325 as the separator. The coin cells were cycled at a current rate of 0.1C (420 mA/gSi) over the potential range of 0.01 – 1.0 V at room temperature.Battery results showed that Si@C hybrid materials increased the capacity of Si anodes by a factor of >2. At Si mass loading of 1.0 mg/cm2, implementing our carbon cloud approach led to an increase in the discharge capacity of anodes from 0.5 mAh (corresponding to anode with bare Si) to >1.0 mAh (corresponding to anode with Si@C hybrids). Results from battery cycling at 0.1C demonstrated excellent capacity retention of >95% after 130 cycles for anodes prepared using our Si@C active materials. The Si content of Si@C hybrid particles was also found to be an influential factor in the cycling performance of anodes. Finally, we observed that the use of water-based polyacrylic acid (PAA) and carboxymethyl cellulose (CMC) binders improve the electrochemical performance of Si@C based anodes. These water-based binders are ideal for preparing Si-based slurries, and the need for using toxic solvents (e.g., NMP) to prepare slurries can be averted. In conclusion, we innovated a viable technology that uses biomass (soybean oil and soyhulls) to enhance Si-based batteries' performance. We demonstrated that our Si@C materials with a carbon cloud protecting the Si nanoparticles are promising active materials to improve the capacity and cycling stability of LIB anodes.

Back Cover Image, Volume 1, Issue 4, October 2022

Battery EnergyVolume 1, Issue 4 12072 COVEROpen Access Back Cover Image, Volume 1, Issue 4, October 2022 First published: 26 October 2022 https://doi.org/10.1002/bte2.12072AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Back Cover: The conception of cheaper and greener electrode materials is critical for Li-ion battery manufacturers. In article number BTE.20220016, Vanpeene et al. have shown that a by-product of the carbothermic reduction of SiO2 to Si, consisting of a mixture of Si, SiC and C, can be used as raw material for production of high-capacity anodes for Li-ion batteries. Volume1, Issue4October 202212072 RelatedInformation

The influence of V addition on the structure, mechanical properties, and oxidation behaviour of TiAlSiN coatings deposited by DC magnetron sputtering

The influence of V content on the morphology, structure, hardness (H) and reduced Young's modulus (E), adhesion, and oxidation resistance of TiAlSiN coatings is investigated. The coatings were produced by DC reactive magnetron sputtering, with increasing V contents from 0, 4.8 and 11.0 at.%. All coatings exhibit a fcc type structure. The coating with 4.8 at.% of V shows the highest values of H and E, whereas the values are similar for the reference coating and the coating with 11.0 at.% of V. The coatings adhere well to the substrates and show a dense and compact columnar growth extending from the adhesive interlayer to the top surface of the coatings. The dynamic thermal gravimetric oxidation curves reveal that V additions decreases the onset point of oxidation significantly and degrades the oxidation resistance of the coatings. A dual oxide layer is formed on the top surface of the reference coating: an outer porous Ti–Al–O rich layer with plate-like features on the top, which classified to TiO2 (rutile and anatase) and Al2O3 phases, and an inner Ti–Si–O rich layer with Al depletion that identified as mixture of amorphous Si–O and Ti–Si–O protective oxides. The diffusion of V to the top surface governs the oxidation process of the V-containing coatings, i.e. increasing V concentration leads to disrupt the formation of the protective continuous oxide layers easily.

Transforming Silicon Slag into High-Capacity Anode Material for Lithium-Ion Batteries

Silicon is mainly produced by carbothermic reduction of silica. This process generates a by-product called silicon slag, which consists mainly of a mixture of Si, SiC and C. This silicon slag represents considerable energy and material losses. On the other hand, the production of cheaper and more environmentally friendly electrode materials is essential for Li-ion battery manufacturers. In this study, it is demonstrated that this waste containing 65 wt% Si, 31 wt% SiC and 4 wt% C can be valorized as low-cost high-capacity LiB anode material. After 20 h of high-energy ball-milling, C is fully converted to SiC and a micrometric powder is obtained in which submicrometric SiC inclusions are embedded in a nanocrystalline/amorphous Si matrix (Fig. 1a). This material displays a specific discharge capacity ≥1100 mAh g-1 at a current density ≤ 0.9 A g-1 (Fig. 1b) and an areal capacity ≥3.5 mAh cm-2 for at least 100 cycles (Fig. 1c). Moreover, calendering has no negative impact on the electrode performance (Fig 1d). The dQ/dV curves (Fig. 1e) do not shown intense-sharp anodic peak at about 0.45V characteristic of the delithiation of the c-Li15Si4 phase, suggesting that its formation is here prevented. This may be beneficial for the electrode cycle life as the formation of c-Li15Si4 phase is well-known to accentuate the particle cracking. However, a progressive and irreversible increase of the electrode mass and thickness is observed over cycling (reaching 125% and 60% after 200 cycles, respectively) (Fig. 1f), which is mainly attributed to the accumulation of solid electrolyte interphase (SEI) products in the electrode. Figure 1

Effect of MgO on electrochemical properties of silicon-based anode composite material

A silicon (Si)/magnesia (MgO)/graphite composite (denoted as SMG@C) was synthesized by high-energy ball milling (HEBM) via the reduction of silica (SiO) by magnesium (Mg) and subsequent addition of graphite, followed by pitch pyrolysis for carbon coating. The particles of MgO in the SMG@C were removed by hydrogen chloride (HCl) leaching to form the Si/graphite composite (denoted as SG@C). The microstructural characteristics of the two composite materials were analyzed by X-ray diffraction and transmission electron microscopy and their electrochemical properties were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and capacity cycling tests. Results indicated that the a homogeneous mixture of nanoscale Si and MgO was fabricated by HEBM, and some of the Si and MgO formed a specific crystallographically coherent interface which was determined as Si(220)//MgO(200). The values of Warburg coefficient for SMG@C and SG@C were determined to be 1.84 Ω/S1/2 and 203.42 Ω/S1/2, respectively. When the SMG@C anode composite material was cycled for 440 cycles at a current density of 200 mA/g, its reversible capacity retention rate was 87.8%, showing excellent long-cycle performance compared to the SG@C. The presence of MgO in the anode composite material greatly improved the electrochemical properties.

Chemical Reactions and Phase Stabilities in the Si-Te System at High Pressures and High Temperatures.

Chemical reactions and phase stabilities in the Si-Te system at high pressures were explored using in situ angle-dispersive synchrotron powder diffraction in a large-volume multianvil press together with density functional theory-based calculations. Cubic and rhombohedrally distorted clathrates, with the general formula Te8@(Si38Te8) and wide compositional range, preceded by a hexagonal phase with the composition Si0.14Te, are formed for different mixtures of Si and Te as starting materials. Si0.14Te, with the structural formula Te2(Te0.74Si0.26)3(Te0.94Si0.06)3, is the very first chalcogenide with the Mn5Si3-type structure. Silicon sesquitelluride α-Si2Te3 decomposes into a mixture of phases that includes the clathrate and hexagonal phases at high pressures and high temperatures. The higher the pressure, the lower the temperature for the two phases to occur. Regardless of the starting compositions, only the clathrate is quenched to atmospheric conditions, while the hexagonal phase amorphizes on decompression. The rhombohedral clathrates Te8@(Si38Te8) form on quenching of the cubic phases to ambient conditions. There is a high degree of interchangeability of Si and Te not only in the clathrates but also in the Mn5Si3-type structure. The theoretical calculations of enthalpies indicate that the reported decomposition of α-Si2Te3 is energetically favorable over its transformation to another polymorph of the A2X3 type at extreme conditions.

Impact of silicon doping on the structure and crystallization of a vanadium-tellurite glass

We studied the effect of silicon doping on the structure and crystallization behavior of 50V2O5-50TeO2 (mol%) (VT) glass by performing solid-state nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). We observed two interesting phenomena. First, when the mixture of glass and Si is heated in argon to 560 K (1.1Tg), Si starts to react with VT glass and is oxidized to amorphous silica, being confirmed by NMR and FTIR. Second, Si suppresses the formation of the Te2V2O9 phase in VT glass during heating process up to 650 K (about 1.3Tg), whereas it leads to the formation of the new crystalline phase TeVO4 during heating to 725 K (1.4Tg). We discuss the origin of these two phenomena by considering the changes both in glass structure and in the redox reaction.

Magnesiothermic Reduction of Natural Quartz

In the current work, the metallothermic reduction of natural quartz by magnesium has been studied at 1373 K under different reaction conditions, i.e. quartz type, quartz particle size, Mg:SiO2 mole ratio and reaction time. The microstructure of reaction products was studied to illustrate the reaction progression through scanning and transmission electron microscopy techniques. X-ray diffraction analysis with Rietveld phase quantification was used to calculate the change in the amount of phases at different reaction conditions. The results showed that the Mg:SiO2 mole ratio strongly affects reaction mechanism and product characteristics such as phase content and microstructure. At lower Mg:SiO2 mole ratios, the reaction rate is fast at the beginning and the formation of a product layer consisting of different phases such as MgO, Si, Mg2Si, Mg2SiO4 and MgSiO3 around quartz particles limits the Mg diffusion. This phenomenon is more noticeable for larger quartz particle sizes where Mg should diffuse longer distance towards the quartz core to react with it. At higher Mg:SiO2 mole ratios, a significant amount of Si–Mg liquid alloy is formed during reaction where the high mobility of Mg in this liquid phase and cracking of quartz particles result in significantly higher reaction rate. Here the formation of intermediate phases is not significant and the products would be the mixture of MgO, Mg2Si, and either Si or Mg phases.

Silicon foliar spraying in the reproductive stage of cotton plays an equivalent role to boron in increasing yield, and combined boron-silicon application, without polymerization, increases fiber quality

Foliar spraying of a boron (B) + silicon (Si) mixture (1.50 g L-1 of B + 1.15 g L-1 of Si) during the reproductive stage of cotton plants could benefit both crop yield and fiber quality; however, further research is needed to confirm this hypothesis. Two experiments were carried out under field conditions, using the FM 906 GLT cotton cultivar, with experiment I conducted in the 2018/2019 growing season and II in 2019/2020. A randomized block design was used for both experiments, consisting of four treatments: water; foliar boron; foliar silicon; and foliar boron + silicon and six replications. A preliminary laboratory test was performed to assess the turbidity of B and Si solutions and determine their compatibility in a mixture. Four foliar applications were performed, beginning in reproductive stage B1, at intervals of 7–11 days. Foliar spraying of B alone was efficient in increasing concentrations of the micronutrient in cotton leaves and fiber. Silicon foliar application was also efficient in raising concentrations in leaves and fiber. Silicon + boron proved to be efficient in supplying cotton plans with both the micronutrient and the element. The internal CO2 concentration and photosynthetic rate of plants treated with B, Si or B+Si were higher than those observed in controls, with no difference between these treatments. The addition of Si to the boron spray solution (B+Si) and Si application alone (Si) increased WUE, with no difference between these treatments, compared with B and controls. Boron, Si and B+Si increased cotton fiber yield, in relation to the control treatment. Individual and combined (B+Si) application of B and Si increased the micronaire values and cotton fiber length in both growing seasons studied. Applying only B or Si also improved the tensile strength of cotton fibers in relation to controls and the highest value for this variable in both experiments was obtained when plants were treated with the B+Si mixture. Foliar spraying of B reduced the short fiber content when compared to controls and applying Si alone or added to the boron solution produced the lowest result for this parameter. Our results demonstrate that foliar Si spraying has an equivalent effect to B on the yield and fiber quality of cotton, and that combining the two elements is particularly beneficial to cotton fiber, improving its tensile strength and reducing short fiber content.

Insights into the growth of hexagonal Si crystals using Al-based nano absorber

Although hexagonal (2H) silicon (Si) semiconductors exhibit excellent optical properties owing to their quasi-direct bandgap, their growth conditions, which require extremely high pressures, preclude their widespread use in industrial applications. The current study, therefore, proposes a novel approach for the facile growth of hexagonal Si at atmospheric pressure via a unique phenomenon known as Al-based nano absorber. A mixed-source hydride vapor phase epitaxy (HVPE) method was used for the growth of the hexagonal Si single crystals employing a rapid interaction between GaCl3, AlCl, and SiCln gases at a high temperature of 1200 °C using a source mixture of Ga, Al, and Si. In this process, the Al-based nano absorber was formed, which resulted in the absorbance of Si atoms, rather than the growth of Al-based nano absorber, to form the Si crystals due to the subsequent lack of GaCl3 and AlCl sources. The hexagonal Si structure of these Si crystals was confirmed using field emission scanning electron microscopy, high-resolution x-ray diffraction spectroscopy, and Raman spectroscopy. Thus, the current study establishes atmospheric pressure mixed-source HVPE as a facile approach for growing various allotropic crystals such as Si, C, or Ge via absorption of other atoms by an Al-based nano absorber.