Morphology Of Si Research Articles

Effects of Zr and Y additions on microstructure and mechanical properties of cast A356 alloy

In the present work, the effects of Zr and/or Y addition on microstructure and mechanical properties of cast A356 alloy were investigated using X-ray diffractometer (XRD), differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The heterogeneous nucleation effect on Zr-rich phases generated by the peritectic reaction, the increased constitutional undercooling caused by Y addition and serve as surfactant led to the grain refinement. Besides, The average size of eutectic Si reduced from 8.5 μm in the base alloy to 6.2, 1.3, and 1.7 μm with the addition of Zr/Y/Zr + Y, respectively. Zr can slightly refine eutectic Si due to the limited growth space caused by grain refinement, while Y can modify the morphology of eutectic Si from plate-like into fibrous-like through high density twins formed by the IIT mechanism. The optimal mechanical properties are obtained when Zr and Y are added simultaneously with the ultimate tensile strength, yield strength, and elongation values of 104 MPa, 201 MPa, and 7.6%, respectively. The YS and UTS increase was due to grain-refining, Si modification and precipitation strengthening. The enhancement of El was mainly caused by Si modification, which reduced the possibility of crack initiation and propagation at Si/α-Al interfaces.

Characterization of Silicon from Rice Husk Doped with Cobalt: Analysis of Structure and Magnetoelectric Properties

The development of Si-based materials has attracted increasing attention, particularly for application in semiconductors, batteries, sensors, and optical technology. Silicon has abundant availability, high energy storage capacity, and low work potential. However, it faces compatibility challenges due to its low electrical conductivity and extremely small magnetic susceptibility. This research aimed to investigate the influence of Co dopants on the structure, morphology, electrical conductivity, and magnetic susceptibility of silicon. Silicon was synthesized using the magnesiothermic reduction method, and silicon was modified with Co metal dopants at 0.1% and 0.5% concentrations through the impregnation method. XRD analysis results showed that Si, 0.1% Co/Si, and 0.5% Co/Si exhibit silicon diffraction patterns at 2θ = 28.42º; 47.28º; 56.11º; 69.13º; and 76.36º. The morphology of Si and Co/Si revealed a rough, uneven, and porous surface with particles appearing spherical. Electrical conductivity increases with Co concentration: Si = 1223 µS/cm, 0.1% Co/Si= 1376 µS/cm, and 0.5% Co/Si= 1529 µS/cm. Magnetic susceptibility measurements indicated that Si, 0.1% Co/Si, and 0.5% Co/Si are paramagnetic at a range of 1.18 x10-6 to 1.25 x10-5 SI. These characterization results confirmed that the modification with Co dopants can enhance the magnetoelectric properties of silicon.

Simultaneous refinement of α-Al and modification of Si in Al–Si alloy achieved via the addition of Y and Zr

Due to the Si/Zr-poisoning effect, conventional refiners often yield unsatisfactory results in refining α-Al grains for Al–Si alloys. In this work, the refinement of α-Al grains and the modification of eutectic Si are simultaneously achieved through the combined addition of Y and Zr to A356 alloy. The results indicate that the individual addition of Zr aids in refinement due to the formation of heterogeneous nuclei Al3Zr, while Y alone can refine α-Al grains and modify eutectic Si to a certain extent. When Y and Zr are added together, not only is the size of α-Al grains further refined to 22.1 μm, but the morphology of eutectic Si is also completely transformed into a fibrous structure. The interaction between Zr and Y decreases their solubility in the matrix, enhances heterogeneous nucleation, and induces the formation of a Al8FeMg3Si6YxZry phase enriched at grain boundaries, suppressing the growth of eutectic Si flakes. Compared to the use of Al–Ti–B refiners and Sr modifiers, the alloy with 0.25Zr and 0.3Y additions exhibits more significant grain refinement and Si modification. Furthermore, it facilitates the precipitation of fine Al3(Y, Zr) particles during the T6 heat treatment process, resulting in an optimal ultimate tensile strength (UST) of 289 MPa and an elongation of 9.75%.

Porous MCM‐41 Silica Materials as Scaffolds for Silicon‐based Lithium‐ion Battery Anodes

AbstractAiming for specific energy improvements, lithium‐ion battery (LIB) research explores Si based materials as potential alternatives for the negative electrode/anode. Si exhibits a high specific capacity when lithiated, accompanied by a large volumetric expansion. To mitigate expansion induced failures, composite materials with finely distributed Si inside a scaffold have been established. Potential scaffolds to create such Si composites are nano porous SiO2 materials, such as MCM‐41. MCM‐41 exhibits a fine nanostructure, and the synthesis allows precise tuning of the pore properties and thus, after filling with Si, of Si morphology and Si content in the composite. In this work, insights into relevant MCM‐41 synthesis parameters are acquired, with special attention towards specific pore volumes and pore sizes of the SiO2 powders. Materials characterization is performed using nitrogen sorption analysis, X‐ray scattering, electron microscopy and thermogravimetric analysis. Selected MCM‐41 scaffolds are processed to Si composites and integrated into LIB electrodes. The specific capacity and the stability of the Si−SiO2 composites are evaluated by PITT and galvanostatic cycling. They show capacities above 800 mAh g−1, i. e. more than twice the specific capacity of industry standard graphite, and last over 200 charge/discharge cycles before their capacity loss exceeds 25 %.

Effect of Al-Sr-Y intermediate alloy on microstructure and mechanical properties of A356 alloy

In this experiment, an intermediate alloy (Al-3Sr-8Y) that can refine and modify A356 alloy simultaneously was developed, and the synergistic effect of Sr and Y on the microstructure and mechanical properties of A356 alloy was investigated. The results show that when the content of Al-3Sr-8Y intermediate alloy reaches 0.3 wt%, the morphology of α-Al dendrites is significantly refined and the secondary dendrite arm spacing (SDAS) was significantly reduced. Moreover, the morphology of eutectic Si transforms from acicular to small fibrous, and the average area and aspect ratio of eutectic Si decrease to 0.81 μm2, and 2.01. This change is caused by the twin plane re-entrant edge (TPRE) poisoning mechanism, where the addition of Al-3Sr-8Y can poison the intrinsic growth position of the Si phase, reduce the growth rate of the Si phase, promote isotropic growth, and achieve a highly branched morphology of the Si phase to form a fibrous structure. Due to the excellent synergistic effect of Sr and Y, the tensile strength and elongation of the alloy reached the maximum values of 303.5 MPa and 9.5% when 0.3 wt% Al-3Sr-8Y was added after heat treatment, which is an increase of 18.2% and 86.3% compared with the untreated A356 alloy, respectively.

Thermodynamic and experimental study on carbothermal reduction of JSC-1A lunar regolith simulant for metal and metalloid production

The carbothermal reduction of JSC-1A lunar simulant with activated carbon was investigated for producing metals and metalloids. Chemical equilibrium compositions were examined using Gibb’s free energy minimization to identify favorable operating temperatures at 0.1, 10-8, and 3 × 10-15 bar for Fe and Si production. Complete conversion of Fe2O3 to Fe(g) was predicted at temperatures above 850 °C and about 90 % conversion of SiO2 to Si(g) was predicted at temperatures above 1000 °C for lunar surface pressure of 3 × 10-15 bar. Thermogravimetry was used to examine the reactions with mixtures of JSC-1A and stoichiometric activated carbon in 100 % Ar up to 1500 °C, and comparisons between temporal mass losses and CO evolution were used to estimate volatile production. The results were compared to ultra-high vacuum experiments at ∼ 10-12 bar with temporal CO measured. Solid-state surface material characterization was performed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy to identify elemental distributions and particle morphology of sample surface before and after experiment as well as chemical compositions present after experiment. Changes in elemental distributions and morphologies of Si-, Fe-, and Ti- in the sample before and after the experiment provided strong evidence of reactions of Si-, Fe-, and Ti- compounds in JSC-1A. Characterization of the loose sample after TGA confirmed the presence of crystalline SiC, Si, and Fe. Deposits collected on Cu foils mounted above the sample in the ultra-high vacuum experiments were found to contain Fe-, Al-, Mg-, and Si- volatiles.

Magnetic field treatment effects on microstructure and properties of A356 aluminium alloy

This study investigates the impact of pulsed magnetic fields (33 mT) under varying ageing temperatures (175, 185 and 195 °C) on α-Al grains, secondary phases and mechanical properties of A356 aluminium alloy. Results show that magnetic field ageing treatment can not only refines α-Al grains and promotes Si particle precipitation, but also improves the size and morphology of eutectic Si. The optimal α-Al grain refinement post-magnetic field treatment is observed at an ageing temperature of 195 °C. Meanwhile, the ultimate tensile strength and yield strength values were recorded at 345 and 283 MPa, respectively. The magnetic field ageing treatment exerts a dual influence: it accelerates atom diffusion, fostering the precipitation of reinforcing phases and simultaneously refines alloy grains, increasing the grain boundaries.

Understanding Electrochemical Properties for a Bio-Based Silicon Anode Electrode Enhanced with Carbon Nanostructure Conductive Additives and Water-Based Binders

Lithium Ion batteries (LIB) demand has shown an exciting increase lately, particularly looking for light-weight solution for portable devices [1], [2]. Recently, The development and implementation of electrode material production techniques pushed the LIB's current state performance to further improvement. Silicon (Si) anode-based electrodes are considered an attractvie alternative to conventional graphite electrodes due to their high specific capacity [3]. Theoretically, Si could alloy with Li up to Li4.4Si and result in a specific capacity of 4200 mAh/g, where the mechanical stress within the electrode material causes loss in the conductivity and breaking of the cell. To overcome this issue, different methodologies have been tested for further improvement of Si implementation with different nanostructures [4]. On the other hand, the production rate of LIB is very important to meet the high demand for different technologies. and, a commercial Si grade is highly recommended along with the conventional tape-casting production method. Furthermore, water-based binders, such as Polyacrylic Acid and Carboxy methyl Cellulose (cellulose-based binders) plays an important role in electrode preparation, where it is supporting the volume expansion of Si and preserveing electrode morphology [5]. Herein, we focus on producing a high-quality Si electrode with cellulose binder, enhanced by conductive carbon allotrope additives. In this study, different Si grades will be tested with different concentrations along with conductive and binder [6]. Electrochemical characterization of the Si anode half cell , such as cycling, cyclic voltammetry, and Impedance spectroscopy vs Li+ metal shows extended and stabilized cycling performance, inferring a reduced anode pulverization.

Microstructure features and mechanical properties of non-heat treated HPDC Al9Si0.6Mn–TiB2 alloys

This study aimed to enhance the mechanical properties of high pressure die casting (HPDC) Al9Si0.6Mn alloys by incorporating in-situ TiB2 particles. The effects of TiB2 addition on the microstructure and mechanical properties of as-HPDC Al9Si0.6Mn alloys were investigated. The results showed that TiB2 addition refined the bimodal grain structure and eutectic Si morphology in the central region of the as-HPDC alloys, which was the primary contributor to the mechanical properties. The thickness of the skin region and band zone increased with increasing TiB2 addition, while the central region exhibited a reduced thickness but remained dominant on the entire cross-section. The optimal TiB2 content was found to be 1 wt%, resulting in the 23.4 % reduction in grain size and 10.7 % enhancement in yield strength. The modified strengthening model based on the microstructure features of the central region accurately predicted the yield strengths of as-HPDC alloys. Finally, the morphological strengthening factors induced by TiB2 particles were analytically illustrated in the HPDC Al9Si0.6Mn–TiB2 alloys.

Effect of rare earth Ce on the microstructure and mechanical properties of cast Al–7Si alloys

Casting experiments were carried out on Al–7Si using different additions of rare earth Ce at a reaction temperature of 1200 K. Based on the ternary phase diagram of Al–Si–Ce, the effects of rare earth Ce on the α-Al grain refinement, the mechanism of the eutectic Si phase modification, as well as on the mechanical properties and fracture morphology of the alloy were investigated. The results show that the addition of rare earth Ce generates a Ce-containing phase inside the alloy, which becomes a heterogeneous core of eutectic Si and changes the nucleation conditions of eutectic Si. The mechanical properties of the alloy were optimal when the Ce addition was 0.2 wt.%, and the defect porosity and average pore area were minimized. Ce-containing phases were found at fracture cracks, and these Ce-containing phases were deviated and aggregated at grain boundaries, which induced defects to be generated, and microcracks were easily produced during plastic deformation, which ultimately led to the fracture of the alloy. According to the growth kinetic relationship, due to the difference of different atomic radii, the inter-atomic forces lead to different nucleation densities of grains. With the generation of Ce-containing phases at the interfaces, the eutectic Si changes its growth direction and grows towards a 70° angle to the original direction with a tighter atomic ordering sequence of the stacking, and more twinned Si is generated and gradually stacked up at the interfaces, which directly alters the morphology of the eutectic Si.

Study of the Morphology of Macroporous Si Obtained by Metal-Stimulated Etching with Au

Study of the Morphology of Macroporous Si Obtained by Metal-Stimulated Etching with Au

Effect of Ti and Sr on the microstructure and mechanical properties of Al-12Si-4.5Cu-2Ni alloy

The effect of Ti and Sr on the microstructure and mechanical properties of Al-Si-Cu-Ni alloy was studied. Research showd that the addition of 0.1% Ti and 0.02% Sr significantly reduced grain size and changed the morphology of eutectic Si. Sr promoted the formation of stacking faults and nano-Al2Cu. The strength and plasticity were significantly increased with ultimate tensile strength, yield strength and elongation being 239.6 MPa, 140.6 MPa, and 2.11%, respectively.

Solidification of Al12Si Melt Pool in Laser Powder Bed Fusion

An understanding of the solidification characteristics of the melt pool during laser powder bed fusion, L-PBF, metal printing is essential to ensure the manufacture of sound parts. This is the main theme of this article where it is attempted to unlock the solidification black box through calculation/measurement of the main solidification parameters of cooling rate, growth rate, temperature gradient, and undercooling. The very small melt pool size and its rapid cooling hinder the application of conventional tools to extract such information. A knowledge of these parameters and their effect on the microstructure and morphology of constituent phases could help to better control the L-PBF process and indeed all the fusion-based additive manufacturing routes, to fabricate high-quality parts. Al12Si alloy solidification during the L-PBF fabrication route is examined to highlight the extreme changes in solidification parameters and their effect on the morphology and size of eutectic Si. This is because the morphology of Si controls the mechanical properties of the finished part. The Al–Si eutectic has a divorced architecture attributed to the difficulty associated with Si growth resulted from rapid solidification. The generation of a temperature gradient of about 7700 °C/mm resulted in cooling rates in the range of 1.1 × 106 °C/s and a growth rate of 140 mm/s. Such values were then used to predict the morphology of eutectic Si based on the traditional approach.

Influence of ball materials on the surface activation behavior of coal ash particles during a mechanochemical process

In this study, the surfaces of coal ash particles were activated via a planetary ball mill-assisted mechanochemical process by utilizing balls that were made from different materials such as zirconia, alumina, and iron. The influence of ball materials on particle morphology, crystallinity, chemical structure, and elution of Si and Al ions in alkali solvents were systematically investigated for the first time, during when the impact energy and friction force induced on the coal ash surface was also clarified in details via the assistance of a self-constructed system. It was found that the mechanochemical process performed with zirconia and iron balls featured a preferred “grinding effect” with decreasing particle size and increasing specific surface area. This was due to the efficiently impact energy induced. In contrast, alumina balls featured an “activation effect” by inducing crystal distortion on the surface and thereby, promoting the ion elution within the alkaline solvents.

Tailoring the strength and corrosion resistance of Al-7Si: Eutectic Si modification by Sr and Sc

The effects of different content of Sr and Sc on the microstructure, mechanical properties and corrosion resistance of an Al-7Si alloy were investigated. The presence of Sc in the Sr-modified Al-Si alloy resulted in multiple types of eutectic Si morphologies. The modification of eutectic Si improved the yield strengthen and elongation of Al-7Si alloys, but lead to the increase of boundaries between α-Al and eutectic Si particles, which caused decrease of corrosion resistance and polarization resistance. The incomplete modification offered a possibility to satisfy the require that a compromise between mechanical properties and corrosion resistance. The relationship between the content of Sr and Sc and the morphologies of eutectic Si in the alloy was also summarized.

Elaboration of Silicon Nanostructures with Vapor-Phase Silver Assisted Chemical Etching: Correlation between Structural and Optical Properties.

Based on the widely used wet metal-assisted electroless etching, we develop in this work a novel vapor-phase silver-assisted chemical etching (VP-Ag-ACE) suitable for the elaboration of highly doped p-silicon (Si) nanostructures with strong, visible, and multi-peak photoluminescence (PL) emissions. The lateral and vertical etching rates (LER and VER) were discussed based on the etching mechanism of the VP-Ag-ACE. The antireflective suitability of the vapor-etched layer has been evaluated by a reflectivity measurement and exhibits reflectivity values lower than 3%. The PL emission at both room and low temperatures emissions were deeply discussed and correlated with the structural properties of the Si morphologies and their surface states based on the FTIR results.

A new synergy to overcome the strength-ductility trade-off dilemma in Al–Si–Cu alloy by micro-nano-particle complex clusters

The effects of the novel micro-nano-particle clusters (nano-AlN and submicron-TiC particles doped with B, referred as TiCB) on the microstructure and mechanical properties of the Al–9Si–3Cu alloy are investigated herein. Comprehensive analysis revealed that the nano-AlN particles resulted in a significant modification of eutectic Si by causing the poisoning of twin plane re-entrant edge growth of Si and restricting the growth of Si crystals. Correspondingly, the morphology of Si transformed from flaky to fibrous. Furthermore, the synergy of areas with and without particle clusters was emphasized to address their contributions to the simultaneous improvement of the strength and ductility. When inoculating the micro-nano-particle clusters into the Al–9Si–3Cu alloy, the yield strength, ultimate tensile strength, and elongation were 138 MPa, 253 MPa, and 5.8%, respectively, corresponding to increases of 23.2%, 23.4%, and 123.1% compared with those of the uninoculated Al–9Si–3Cu base alloy (112 MPa, 205 MPa, and 2.6%, respectively). After T6 heat treatment, the spheroidal Si and θ′ phases on the Al matrix further improved the strength of the Al–9Si–3Cu alloy. This work may provide a promising strategy to design and fabricate Al–Si–Cu alloy with high strength and ductility.

Mechanism of AlP modifying the morphology of Si in Al-20Si alloys based on experimental studies and first-principles calculations

ABSTRACT The modifying influence of aluminium phosphide to the morphology of primary Si and eutectic Si was investigated in hypereutectic Al-20Si alloys via adding Al-Cu-P master alloy (0.5, 1, 20 wt.%). Microstructural results showed when Al-Cu-P addition from 0 to 0.5%, primary Si phase decreases and eutectic Si phase size remains invariable; when addition higher than 0.5%, primary Si phase keeps invariable, eutectic Si phase size increases. To prove the nucleation effect of AlP on Si phase, interfacial properties of Si/AlP interface were investigated using first-principles calculations. Results showed the AlP(100)/Si(100) interface energy is between −1.45 J/m2 and −1.38 J/m2 for Al-terminated and P-terminated AlP model, both is much smaller than liquid Si/crystalline Si interface (0.34 J/m2), consolidates that AlP particles possess strong nucleation potency for Si phases. Therefore, the modifying influence of AlP to the morphology Si phase is well clarified as a function of AlP content in Al-20Si alloys.

Effects of thermal ageing on the wear behavior of the cerium modified Al-18si-3.6cu alloy

ABSTRACT In the present investigation, an Al-18Si-3.6Cu alloy was modified by cerium (Ce), heat treated (T6), and aged for 1, 3, 5, and 7 h at 210°C. The resulting microstructures revealed that the addition of Ce as a modifier changed the morphology of the primary Si from coarse with a sharp edge to spherical, large-acicular/needle-like eutectic Si into a fibrous state, and dendrites of the Al phase into round branches with less interface separation. After thermal ageing, the microstructure of the modified alloy revealed no change in the morphology of the primary Si phase. However, a considerable change in the eutectic Si phase and the formation of fine precipitates of Al2Cu and Al2CeSi intermetallics in the matrix. Hardness was found to be significantly higher in the modified and age-hardened alloys. A Pin-on-disc wear tester was used to investigate the dry sliding wear behavior of alloys at different loads (10, 20, 30, and 40 N) and 1.0 m/s sliding velocity. The results indicated that the wear rate in the modified alloy was lower than the base alloy. Furthermore, the modified alloy after 5 h age hardening demonstrated high wear resistance and improved wear bearing capacity compared to the 1, 3, and 7 h age hardened alloys.

Effect of T6 heat treatment on microstructure and mechanical properties of large-weight aluminum alloy flywheel housing parts formed by local-loading squeeze casting

In this research, ZL104 aluminum alloy flywheel housing with large wall-thickness difference and complex shape were formed via local-loading squeeze casting. The effects of T6 heat treatment process parameters (solution time and temperature, aging time and temperature) on mechanical properties and microstructure of ZL104 aluminum flywheel housing were studied. The microstructure of the formed parts with heat treatment was analyzed by scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and optical microscope (OM). The mechanical property test results indicated that the improvement of strength was limited with the increase of solution temperature and solution time, but the elongation improved significantly. For solution treatment, the optimum mechanical properties (ultimate tensile strength, yield strength, and elongation were 243 MPa, 133 MPa, and 14%) were obtained at 550 °C/3 h. The strength increased first and then decreased with the increase of aging time. After 8 h/175 °C aging treatment (following by solid solution), the maximum tensile strength and yield strength reached 312 MPa and 251 MPa, respectively. After T6 heat treatment, the morphology of Si spheroidized and coarsened obviously. The Si particles with fine size were formed. Continuous dynamic recrystallization occurred during heat treatment but was not very sufficient.