High Silicon Content Research Articles

Petrogenesis and metallogenic significance of late Mesozoic granites in the Akjilga mining area, Tajikistan: constraints from geochronology and geochemistry

The Akjilga (Акджилга) mining area in Tajikistan sits in the central part of the Pamir syntaxis in the western part of the Indo–Eurasia collisional orogenic belt. Recently, the mineralization phenomena of skarn-type tin polymetallic ore bodies and dolomite-type rare-earth metals in the copper polymetallic mining area have been reported. However, the limited knowledge on the genesis of granite and its relationship with mineralization in this area hinders further research. Here, the Late Mesozoic granite rocks in the mining area were studied by petrology, geochemistry, and zircon U–Pb dating. The results showed that the rocks comprise majorly porphyric biotite syenogranite and minorly porphyric biotite monzogranite. The zircon U–Pb age of the porphyric biotite syenogranite was 108.3 ± 2.0 Ma, highlighting the Early Cretaceous period. The porphyric biotite syenogranite features high silicon and potassium contents and low iron, magnesium, calcium, sodium, titanium, and phosphorus contents. Furthermore, their aluminum saturation indexes were 1.11–1.21. Therefore, they were classified as high-potassium calc-alkaline strong peraluminous rocks. Trace-element analysis showed the enrichment of large ionic lithophile elements and light rare-earth elements (REEs); the deficiency of high-field-strength elements and heavy REEs; and the negative anomalies of Nb, P, and Ti. Compared with ordinary granites, the porphyric biotite syenogranite exhibits a higher differentiation index (91.20–93.96) and strong negative Eu anomaly (0.05–0.26), as well as a low Zr content and abnormally low Nb/Ta, Zr/Hf, Y/Ho, ∑LREE/∑HREE ratios. Therefore, the rocks are considered highly differentiated I-type granites with good Sn polymetallic and rare-metal prospecting potentials, and it resulted in the subduction-collision of the Rushan-Pshart ocean between the Middle Pamir block and the South Pamir block during the northward subduction process of the Late Mesozoic New Tethys ocean (Shyok ocean).

Dilatometric Investigation of Si-Rich Contacting Anode Under External Pressure

Silicon with high abundance and high gravimetric capacity around 3579 mAh.g-1 at Li15Si4 fully lithiated state [1] is one of the attractive anode materials in lithium-ion batteries. Volume expansion of around 300% in the fully intercalated state is the Achilles’ heel of silicon, causing particle pulverisation, continuous formation of solid electrolyte interface (SEI), loss of electrical contact and capacity loss.[2] The use of silicon composite instead of pure silicon, [1,3] limited de/lithiation,[4] and boosting the electrical connection between particles by applying optimal external pressure[5] are practical solutions to mitigate these disadvantages. This study investigates the electrochemical performance and the dilatometric behaviour of a multilayer pouch cells (0.06 to 1.5 Ah) under the external mechanical pressure. Using 1/3 of the Si capacity in order to stabilise the electrochemical performance of a high silicon content anode (70 wt% Si). An irreversible electrode expansion of about 20% after 3 cycles of formation at 0.1C and a 75% electrode thickening after 200 cycles at 0.5C were observed.

Achieving superior mechanical properties: Tailoring multicomponent microstructure in AISI 9254 spring steel through a two-stage Q&P process and nanoscale carbide integration

In the pursuit of lightweight, durable steel, we have successfully developed a multicomponent structure in AISI 9254 spring steel using a two-stage quenching and partitioning (Q&P) process. The primary objective of this process was to engineer an optimized microstructure consisting of nanobainite, martensite, and nano-carbides. Utilizing the insights gained from the results of advanced techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT) performed on the as-received AISI 9254 spring steel, we refined the quenching and partitioning (Q&P) path, leading to the successful establishment of a bainitic transformation for superior mechanical properties. Our tensile tests revealed a high yield strength (≈ 1600 ± 25 MPa) and ultimate tensile strength (≈ 1850 ± 50 MPa), along with considerable elongation (≈ 11.15 ± 0.25%). We also identified that pre-formed martensite lath defects and high silicon content play crucial roles during the Q&P process, preventing carbide coalescence and increasing strain-hardening capacity. This study demonstrates the potential of a Q&P process to generate high-strength, ductile steel for automotive and aerospace applications.

Laser Scanning Method for High-Resolution Thickness Mapping of Lithium-Ion Pouch Cells

A precise understanding of the physical properties of lithium-ion cells including the cell thickness distribution during cycling and its connection with lifetime is important for cell improvement. A laser scanning instrument has been developed to perform contact-free thickness measurements in operando for small 250 mAh lithium-ion pouch cells and a large 60 Ah automotive format pouch cell. LiNi0.83Mn0.07Co0.10O2/silicon-graphite cells with 20 and 10 wt% micron-sized silicon particles, a LiNi0.8Mn0.1Co0.1O2/natural graphite cell, and a medium-Ni/graphite automotive cell were either cycled in the laser scanning setup with continuous operando thickness mapping or aged at elevated temperature on separate battery cyclers with intermittent operando thickness mapping using the new laser scanning instrument. During the operando cycles, the cell thickness was measured periodically every 1 h and a graphical quantification method was developed to determine reversible and irreversible swelling of the silicon-containing and silicon-free cells. Using the high-resolution laser scanning technique, irreversible cell swelling could be correlated with capacity loss, especially in cells with high silicon content. Graphite-based cells with mature interface like the large automotive pouch cell showed a fully reversible swelling profile indicative of a long-lived cell.

Atmospheric Pollution from a Storage of Tungsten–Molybdenum Ore Mining and Processing Wastes

Experimental studies of the surface atmosphere pollution with mining and processing wastes of tungsten–molybdenum ore were carried out using an equipment devised for collecting aerosols above the surface of sands. It has been established that toxic components formed during the decomposition of residual sulfide mineralization and products of interaction between acidic waters and rocks are transported with water vapor from the sands to the surface. The moisture condensed over the sands contains high concentrations of aluminum, fluorine, iron, silicon, manganese, zinc, and phosphorus. These elements form an atmospheric pollution halo over the technogenic sands and are further dispersed by air currents over neighboring areas. In winter, the snow cover is polluted over a vast territory due to wind dispersion of the aerosols. The halo of pollution extends over tens of square kilometers. A dependence was identified of qualitative and quantitative composition of the components polluting the snow cover on the storage time of the ore processing products. It is shown that some of the toxic elements pass into solution during snow melting from suspended solids, which are brought by wind from the territory where the soil cover is disturbed by mining.

Exploring Microstructure, Wear Resistance, and Electrochemical Properties of AlSi10Mg Alloy Fabricated Using Spark Plasma Sintering

Al-Si-Mg alloy has excellent casting performance due to its high silicon content, but the coarse eutectic silicon phase can lead to a decrease in its mechanical properties. Samples of AlSi10Mg alloy were prepared by using a spark plasma sintering method, and it was found that sintering temperature has a significant impact on the grain size, eutectic silicon size and wear and corrosion properties after heat treatment. At a sintering temperature of 525 °C, the alloy exhibits the best wear performance with an average friction coefficient of 0.29. This is attributed to the uniform precipitation of fine eutectic silicon phases, significantly improving wear resistance and establishing adhesive wear as the wear mechanism of AlSi10Mg alloy at room temperature. The electrochemical performance of AlSi10Mg sintered at 500 °C is the best, with Icorr and Ecorr being 1.33 × 10−6 A·cm−2 and −0.57 V, respectively. This is attributed to the refinement of grain size and eutectic silicon size, as well as the appropriate Si volume fraction. Therefore, optimizing the sintering temperature can effectively improve the performance of AlSi10Mg alloy.

Effects of N/Si ratio on mechanical properties of amorphous silicon nitride coating

The utilization of silicon nitride coatings has been proposed as an effective method to enhance wear resistance and mitigate the release of metallic ions from biomedical implants. However, the relatively high dissolution rate of low-density coatings remains an obstacle to their implementation. Here, chemical vapour deposition techniques may have advantages over the typically used physical vapour deposition (PVD) methods. Therefore, in this study, silicon nitride coatings were obtained by low-pressure chemical vapor deposition (LPCVD). Since the nitrogen-to-silicon (N/Si) ratio and deposition temperature have been reported as major factors affecting the performance of the coatings, the effects of ammonia (NH3) to dichlorosilane (SiH2Cl2) flow ratio and deposition temperature were systemically investigated in the form of microstructure, mechanical and tribological properties of the coatings. The results revealed that the coatings exhibited a dense structure. As the ammonia flow ratio increased, the surface became smoother, and the hardness and elastic modulus increased and reached the maximum at a flow ratio of 4, giving a hardness of around 27 GPa and an elastic modulus of 290 GPa, respectively. The higher mechanical properties of the coatings deposited at a flow ratio of 4 are attributed to the stronger covalent Si-N bonding, as confirmed by XPS results. However, the coatings deposited at a flow ratio of 2 exhibited the lowest wear rate, at 9.5 10−7 mm3 Nm−1, around one-third of the value of the coatings deposited at a flow ratio of 6, likely due to the high silicon content of these coatings. Increasing the temperature resulted in an increased deposition rate, higher hardness and elastic modulus as well as a lower wear rate, likely due to incomplete reactions at lower temperatures. The generally high hardness and low wear rate indicate that the coatings deposited by LPCVD are promising for application in spinal implants.

Carbonate lithium isotope systematics indicate cooling triggered mass extinction during the Frasnian-Famennian transition

We present comprehensive Li-C-Sr isotopic studies on two classic marine carbonate sections (Yangdi and Dongcun) transecting the Late Devonian Frasnian-Famennian (FF) boundary from South China to constrain the causes of the FF mass extinction. Both sections show positive Li and C isotopic excursions in carbonate and unchanged conodont 87Sr/86Sr ratios across the FF boundary. Low Li/Ca and Sr/Ca ratios, but heavy Li isotope composition (δ7Li) of the Dongcun section indicate possible diagenetic alteration on carbonate Li isotopic records. By contrast, the Yangdi section records more primary seawater δ7Li signal, showing a ∼ 2 ‰ positive excursion before the FF boundary, although reconstructed paleo-seawater δ7Li values (from 11.8 ± 1.4‰ to 13.8 ± 1.4‰) are lower than modern times. Combined box model with Monte Carlo simulation demonstrates that low seawater δ7Li requires low riverine δ7Li and small effective Li isotopic fractionation by marine sinks (Δ7Lisw-ms). The latter is likely due to high silicon concentration in the paleo-seawater and rapid formation of clay minerals. Positive δ7Li excursion but invariant 87Sr/86Sr ratios in the seawater are related to attenuated continental weathering (reduced riverine fluxes but increased riverine δ7Li), and enlarged effective Δ7Lisw-ms. Based on the present data we suggest that rapid climate cooling is responsible for the weathering transition and must have exerted significant influence on the marine environment. Global climate cooling weakens seawater stratification while intensifying oceanic circulation and upwelling, resulting in enhanced primary productivity, precipitation of the Kellwasser black shales and a remarkable positive C isotopic excursion in carbonate. Additionally, rapid climate cooling around the FF boundary has significantly threatened the ecological system and finally triggered mass extinction especially for the faunas adapted to warm temperatures.

Compression and bending of alkali-activated slag cementitious materials at high temperature

Alkali-activated slag cementitious material (AASCM) with manufactured sand can effectively utilise industrial waste slag and reduce river sand consumption. Steel fibres can effectively improve the mechanical properties of AASCM. Therefore, in this study, the influence of steel fibres and aggregate type on the compression and bending properties of AASCM after high-temperature treatment was investigated. The results show that the mass loss rate, compressive strength and flexural strength loss rate of AASCM with manufactured sand were higher than those with natural river sand at different temperatures. Steel fibres can increase the mass loss rate of AASCM; however, the influence of the steel fibre content on the mass loss of AASCM was not apparent. When the temperature was lower than 600°C, the compressive and flexural strength of AASCM was effectively increased by steel fibres, while, for temperatures higher than 800°C, the mechanical properties of AASCM did not improve, owing to the oxidation failure of steel fibres. Microstructure analysis showed that the number of microcracks in the AASCM increased, owing to the high silicon content of the manufactured sand, and the bond property between the steel fibres and cementitious materials decreased with an increase in temperature.

Recovered Scandium from Tungsten Residue with High Silicon Content

Recovered Scandium from Tungsten Residue with High Silicon Content

Minerals of the apatite group from ultramafic lamprophyres of the Zima alkaline-ultramafic carbonate complex (Urik-Iya graben, Eastern Sayan region)

Research subject. This paper presents the results of a study of minerals of the apatite group from aillikites of the Zima alkaline-ultramafic carbonatite complex. Aim. To determine the composition of apatites to characterize the studied rocks and to elucidate the patterns of element distribution in the magma of aillikites in the late crystallization stages. Materials and Methods. Minerals of the apatite group from 6 samples (4 from dikes of the Bol'shetagninsky massif, 1 from the Bushkanai dike, 1 from the Beloziminskaya pipe) were studied. The samples showed similar textural-structural features, differing in the mineral composition of the groundmass. Results. Minerals of the apatite group are widespread in the groundmass of all the studied rocks. They are characterized by idiomorphic, subidiomorphic crystals of homogeneous composition, 10-100 microns in size. Minerals of the apatite group were identified as fluorapatite and hydroxyapatite characterized by a significant SiO2 content (up to 5 wt %), low SrO content (up to 1.5 wt %) and REE2O3 (up to 2 wt %). The studied apatites also include MgO, FeO, Na2O, SO4, and CO3. Fluorapatites from dyke aillikites are characterized by a higher silicon content as compared to apatites from the Beloziminskiy pipe. Apatites from fresh aillikites of the Bushkanai dyke have a relatively higher content of Sr, REE, and F than minerals from serpentinized samples. Conclusions. The composition of the studied apatites has a lower Sr and Ba content than orangeite and lamproite apatites. In terms of Sr, Si and REE contents, the studied apatites are similar to kimberlite and ailikite apatites. Such a difference allows minerals of the apatite group to be used as an indicator mineral for classification of kimberlites and related rocks, but only in combination with petrography and composition of other minerals of the groundmass.

Microstructure evolution of Ni-Cr-Mo superalloy fabricated by microwave-assisted combustion synthesis

In this study, the microwave-assisted self-propagation high-temperature synthesis (SHS) technique was utilized to successfully synthesize the Nistelle super C commercial alloy with the chemical composition of Ni59Cr23Mo18. The precursors used for this purpose were NiO, Cr2O3, and MoO3 oxide compounds. The thermodynamicall calculations were carried out by the Factsage software. The synthesized alloys' chemical composition, phase, and microstructure were evaluated by induction-coupled plasma, X-ray diffraction, optical microscopy, and scanning electron microscopy. The findings revealed considerable residual silicon in the final product due to using Si as the reducing agent. The presence of residual Si in the chemical composition led to forming a eutectic Niγ-FCC+ Mo2Ni3Si microstructure in the alloys produced by the alumino/silicothermic method. The high silicon content in the excess Al-containing sample led to forming of proeutectic Mo2Ni3Si phases with a petaloid morphology. Besides, this alloy displayed small islands of the interdendritic nickel silicide phase. Conversely, the aluminothermic sample showed a nearly single-phase structure with low amounts of the precipitates of chromium and molybdenum-rich phases. The phase diagram plotted for this sample indicated that the precipitates were probably TCP phases like σ and P. In all the samples, the segregation of Mo occurred significantly, while Cr was distributed almost uniformly in all regions. The formation of the Mo2Ni3Si intermetallic phase resulted in the significant segregation of Mo and depletion of the Niγ-FCC matrix from this element. However, the segregation of Mo was also observed near the grain boundaries in the single-phase sample. The results showed that the dissolution of the alloying elements, especially molybdenum, caused severe offset in some peaks of the Niγ-FCC XRD pattern.

Effect of thermal aging at 550 °C on microstructure and mechanical properties of a 9Cr martensitic steel with high silicon content

Effect of thermal aging at 550 °C on microstructure and mechanical properties of a 9Cr martensitic steel with high silicon content (named as HSi steel) was investigated by field emission scanning electron microscopy (FESEM), electron backscattered diffraction (EBSD), transmission electron microscopy (TEM) and tensile and impact test. During aging, the martensitic matrix (including lath size, effective grain size and high angle boundaries) basically keeps stable. The M23C6 in HSi steel gradually coarsens with increasing aging time and the morphology of M23C6 on grain boundary tends to be chain-shaped, and then gradually becomes discrete again. Meanwhile, the Laves phase will precipitate adjacent to M23C6 due to a Si-rich layer around M23C6 and coarsens quickly before aging for 3000 h. With further increasing aging time, Laves phase is stable with a size of about 136 nm. The mechanical properties test results show that yield strength and elongation have little change during aging. However, the impact energy of HSi steel drops obviously after precipitation of Laves phase and the impact fracture presents cleavage fracture morphology. When the aging time is over 3000 h, the coarsening rate of Laves phase is very low and the HSi steel exhibits a relatively stable impact energy about 113 J. After aging up to 10,000 h, HSi steel still has excellent comprehensive mechanical properties.

Control of Nanoparticle Dispersion, SEI Composition, and Electrode Morphology Enable Long Cycle Life in High Silicon Content, Nanoparticle-Based Composite Anodes for Lithium-Ion Batteries

Striking a balance between high theoretical capacity, Earth abundance, and compatibility with existing manufacturing infrastructure, silicon is one of the few materials that meets the requirements for a next-generation anode for rechargeable lithium-ion batteries. Due to complications with extreme volume changes during charging/discharging and reactive interfacial chemistries, however, the cycle-life of silicon-based composite anodes is unacceptable for broad use. Developing a majority silicon composite anode formulation that overcomes these challenges and is compatible with current industry manufacturing practices requires materials and chemical engineering solutions that account for both electrode morphology and interfacial chemistry. Here, we synthesize surface-functionalized silicon nanocrystals that enable a highly dispersed and homogeneous slurry that can easily be integrated into standard electrode fabrication process. We use this formulation to print a 76 wt. % silicon composite electrode. We show that the contents and the morphology of the silicon electrolyte interphase – a determining factor in the cycle life of silicon-based anodes – can be controlled with a post-synthetic thermal curing procedure. When paired against a capacity-matched lithium nickel manganese cobalt oxide LiNi0.8Mn0.1Co0.1O2 cathode, the cell retains 72% of its capacity through 1000 charge/discharge cycles while delivering an initial anode specific capacity of nearly 1000 mAh/g and an areal capacity of 2.55 mAh/cm2. Figure 1

Dilatometric study of high silicon bainitic steels: Solid-state transformations

High silicon bainitic steels have gained significant recognition in various applications due to their exceptional properties, such as high strength, favourable corrosion resistance, and excellent high-temperature stability. This study investigates an alloy capable of generating a finer bainitic structure through a transformation at 260 °C, leading to the desired microstructure. Interestingly, other phenomena were discovered while pursuing optimal heat treatment conditions. At temperatures exceeding 850 °C, the alloy exhibits a tendency for graphite formation, which has intriguing implications for its mechanical properties. The high silicon concentration in the alloy significantly retards cementite growth, resulting in a microstructure composed solely of bainitic ferrite and residual austenite through the transformation of austenite below the bainite start temperature. Furthermore, it is observed that pearlite formed during rapid transformation at 650 °C does not exhibit the predicted equilibrium chemical composition. This discrepancy challenges the existing models of pearlite growth, which assume local equilibrium at the shared interface with austenite. This research aims to investigate the influence of silicon content on solid-state transformations in high-silicon steels using dilatometry, optical microscopy, scanning electron microscopy, and X–ray diffraction techniques. These analytical methods will provide insights into the intricate processes occurring during isothermal transformation temperatures, contributing to a deeper understanding of the material's behaviour and its potential applications.

Effect of silicone segment and imidization of polyimide-based binder on the electrochemical performances of high silicon content anode for lithium-ion batteries

Binders are expected to play important role in silicon-based anode materials, but have not been well explored. In this work, a serial of silicon containing polyimides and polyamides have been synthesized and used as the binder of high content (80wt%) silicon anode. Systematic characterizations have been done on the chemical structures, physical properties of the binders, and the electrochemical performances of silicon-based anode. It was found that the swelling ratio, adhesion strength, and hardness plays important roles on the initial Coulombic efficiency (ICE) and capacity retention of silicon-based anode, and these parameters highly depend on the types and properties of binders. After optimizing the chemical structures and physical properties of the binders, a high specific capacity of 2941 mAh g−1, relatively high initial Coulombic efficiency (ICE) of 83%, and good capacity retention of 85% (after 200 cycles) have been obtained. These results would help researchers to design new types of binders for silicon-based anode to improve its ICE and capacity stability.

Effect of Preheating on the Mechanical Workability Improvement of High-Strength Electrical Steels during Tandem Cold Rolling

Cold-rolled silicon steel strip products are widely used as the main soft magnetic components in cores of electrical motors, generators, and transformers. In the case of rotating electrical machines, the so-called non-oriented electro-technical steels are normally applied. They are characterized by a similar behaviour to the induced magnetic field found in all sheet plane directions. The kind of soft magnetic alloys that defined herein not only possess an isotropy of electromagnetic properties, but also high mechanical strength; such alloys are called high-strength electro-technical (HSET) steels. These commercially produced HSET steels contain a high silicon content in the range of 3–4 wt.%. However, if the silicon content exceeds 3%, the machinability of Fe–Si alloys is dramatically reduced and they become much more brittle as a consequence. According to this, regular hot band brittle damage occurs during cold deformation at a high-speed tandem rolling mill. In accordance with these reasons, the production of thin high-strength silicon steel grades using the traditional methods of cold rolling deformation is extremely problematic and it is characterised by a high degree of steel sheet mechanical damage. In this scientific work, the effect of preheating hot-rolled strips on their mechanical workability improvement during tandem cold rolling was investigated. The results of this study indicate that the cold rolling of hot bands at elevated temperatures increases their resistance to brittle failure and mechanical plasticity. Moreover, the mathematical simulation clearly demonstrates that residual stress is distributed relatively homogeneously across the thickness of samples, which were cold rolled at 100 °C in contrast to the same ones deformed at room temperature.

CO2 capture using lithium-based sorbents prepared with construction and demolition wastes as raw materials

CO2 capture was tested using lithium silicates prepared with construction and demolition waste materials (CDWM) to climate change mitigation. Four types of CDWM with high silicon and aluminum content were evaluated: sand, block, ceramic sanitary ware (CSW), and concrete wastes. CDWM were characterized by XRF, XRD and SEM-EDS; subsequently, the non-conventional precursors were mixed with LiOH and thermally treated in two stages: at 250 and 550 °C. Li4SiO4 was synthesized using conventional SiO2, applying the same synthesis method, and used as a reference. Li4SiO4, Li2SiO3 and LiAlO2 crystalline phases were obtained from all CDWM. Additionally, Li2CaSiO4 was detected in the case of wastes with high calcium content (block and concrete). The prepared Li4SiO4 samples were evaluated using the TGA technique for CO2 capture in dynamic and isothermal modes. The bulk CO2 adsorption in the Li4SiO4 prepared with CDWM started at a lower temperature (380 °C) than the material prepared with conventional precursors (500 °C). The temperature of CO2 sorption maxima was estimated at around 600 °C, being the Li4SiO4 prepared with block waste the material with the best performance. According to the isothermal analysis, the block-derived lithium silicate achieved a maximum CO2 capture capacity of 183 mg/g at 580 °C with PCO2 = 0.2; the desorption was observed above this temperature. The kinetic results (Avrami Eroffev model) were similar to those of Li4SiO4 prepared with conventional SiO2. Moreover, the stability of the materials was demonstrated during 20 cycles of the sorption-desorption process, displaying a constant sorption capacity of 180 CO2 mg/g.

Powder bed fusion of soft-magnetic iron-based alloys with high silicon content

Powder bed fusion of soft-magnetic iron-based alloys with high silicon content

Systematic study of growth behavior of β-Al9Fe2Si2 in Al alloys with high iron and silicon contents

β-AlFeSi is one of the most common and most damaging intermetallics in aluminum alloys containing silicon. The study of its growth behavior is crucial for alloy design. In this work, Al-8.1Si–5Fe and Al–13Si–3Fe alloys were cast to study the growth of β-AlFeSi. The skirt like β-AlFeSi clusters formed by splitting were discovered, and this phenomenon was found to be mainly caused by thermal stress. By micro to atomic scale electron microscopy studies, a layer-by-layer growth mode along the (001) crystal plane was proposed for β-AlFeSi. In addition, it is found that β-AlFeSi grows along the heat flow, and the preferred growth orientation is determined to be [100]/[010]. Other characteristics of β growth, such as stacking faults and inducing formation of pores, were also reported and discussed.