Fine Si Particles Research Articles

Microstructural characterization of cellular AlSi10Mg alloy fabricated by selective laser melting

In order to understand the microstructural characteristics of cellular (porous) AlSi10Mg alloy fabricated via selective laser melting (SLM), we designed SLM-fabricated AlSi10Mg alloy samples with various box-shaped structures containing interior X-shaped shelves as a representative model of porous aluminum. All fabricated samples exhibited characteristic microstructural morphologies comprising melt pools with columnar α-Al phases surrounded by fine eutectic Si particles. Several columnar α-Al phases exhibited 〈001〉 orientations along the elongation direction, resulting in a {001} texture. In the shelf wall regions of fabricated samples, the elongation direction of the columnar α-Al phases varied depending on the incline angle between the inclined wall plane and the laser irradiation direction (θ), reducing the formation of {001} texture in samples with high incline angles. In the regions wherein the X-shaped shelves intersect, the microstructure varied in different sections: the α-Al phases observed in the lower portion appeared coarser and more equiaxed compared with those in the upper portion. The microstructural difference was more significant in samples with higher incline angles, which contributes to the observed variations in hardness values. Based on the results obtained, we discuss the dominant factor leading to the observed inhomogeneity of the microstructure of cellular AlSi10Mg alloy fabricated via SLM.

Microstructural and tribological investigations of diecast and hard anodized AlSiCu alloys

This work is aimed to understand the impact of the surface characteristics of diecast Al-Si-Cu alloy on the hard-anodizing process. High-pressure die-cast plates made of AlSi9Cu3(Fe), AlSi11Cu2(Fe) and AlSi12Cu1(Fe) alloys were hard anodized in as-diecast condition and after sandblasting and surface milling operations.The thickness and morphology of the anodic layer were investigated using optical and electron microscopy, whereas the tribological properties were evaluated using a reciprocating sliding testing machine under ball-on-flat configuration. The removal of both external eutectic Si segregation and oxide passivating layer due to milling operation is beneficial to increase the thickness of the anodic film, independently of the investigated alloy. However, this leads to a decrease of the abrasion resistance due to the presence of coarser Si particles. Sandblasting removes lower amounts of material and its effect on the anodizing response is more affected by the initial chemical composition of the alloy. The thickness of the oxide layer over the as-diecast surfaces increases by increasing the eutectic fraction and decreasing the Cu content. The greater the amount of α-Al phase in the surface microstructure, the thicker the anodic layer will be. Fine and globular eutectic Si particles lead to a thicker hard anodic layer respect to coarser and plate-like ones. The anodizing response seems in any case to be more related to the amount of α-Al matrix than the shape of Si particles. Higher eutectic fraction with globular eutectic Si particles is useful to increase the tribological properties of the anodic film. Lower eutectic amounts lead to increase the thickness of the anodic film but also to decrease the abrasion resistance.

Tribo-mechanical behavior of complex hypereutectic Al–Si alloy compressed through a converging die at elevated temperatures

This work deals with the tribo-mechanical behavior of the complex hypereutectic aluminum-silicon alloy Al–18Si–2.5Cu–0.6Fe (wt%) in the as-cast condition and the following compression through converging die under different reduction ratios (R) of 1.5 and 2.0 at working temperatures of 300, 400, and 500 °C. X-ray diffractometry pattern showed the formation of intermetallic compounds (β-Al4.5FeSi and Al2Cu) due to the higher temperature during the process run over. Microstructural features were characterized by scanning electron microscope, and remarkable grain refinement was observed in the compressed samples. Mechanical properties were adjudged by tensile test and microhardness test. There was significant improvement in the ultimate tensile strength and hardness of the compressed billets which may be attributed to grain refinement of the matrix and uniform dispersion of the fine Si particles and the intermetallic compounds. A pin-on-disc tribometer was used for the wear test. Higher wear resistance was observed in the compressed alloy as compared to the as-cast alloy due to the presence of the fine Si particles and strengthening of the matrix. The present work provides valuable insights into tribo-mechanical characteristics of the Al–18Si–2.5Cu–0.6Fe (wt%) alloy for broad industrial applications.

Heat-induced molten pool boundary softening behavior and its effect on tensile properties of laser additive manufactured aluminum alloy

Changes in the microstructure and the mechanical properties of AlSi10 Mg alloy fabricated by selective laser melting combined with the subsequent heat treatment have been studied. The influence of the heat treatment on the molten pool boundary softening, microstructure evolution and the resultant mechanical properties has been elucidated. The as-fabricated specimens exhibited the various Si phase patterns within the different regions of the molten pool corresponding to the columnar perpendicular to the molten pool boundary and cellular columnar in the upper center region due to the various thermal behaviors. The solubility of Si atoms was decreased and rejected into fine Si particles with the formation of the molten pool boundary softening and the homogeneous distribution in the heat induced part, playing a key role in the mechanical properties of AlSi10 Mg alloy. The ultimate tensile strength decreased from 476.8 MPa for the as-fabricated part to 320.5 MPa while, the fracture ductility significantly increased from 7.33% to 13.3% as the test specimens were heat treated at 573 K for 2 h. It indicated that the microstructure evolution and tensile properties of the as-fabricated AlSi10 Mg alloy could be tailored through molten pool softening and size and morphology of the Si phase at the suitable heat treatments.

A comparative study on corrosion and microstructure of direct metal laser sintered AlSi10Mg_200C and die cast A360.1 aluminum

Direct metal laser sintering (DMLS) is an additive manufacturing technique that creates near-net-shape functional components by selectively melting metal powders in two dimensions layer by layer using a high power laser as a heat source. This technique offers to create parts with complex net-shape structures at an affordable cost with the least lead time. The main purpose of this study is to investigate the corrosion behavior and microstructure of AlSi10Mg_200C manufactured using DMLS compared with its die cast counterpart (A360.1 die cast Al alloy). The impact of the alloy’s surface finish, i.e. as-printed surface versus as-ground one, on the corrosion performance was also investigated. Several AlSi10Mg_200C cube samples were additively manufactured through DMLS technique. In addition, the same size cubes were cut from an aluminum A360.1 die cast ingot. The corrosion behavior of the two alloys was analyzed utilizing potentiodynamic polarization testing and electrochemical impedance spectroscopy in aerated 3.5 wt.% NaCl solution to mimic sea water environment at 25 °C. Further, the microstructures and composition of the samples before and after corrosion testing were investigated using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) spectroscopy. The results confirmed that the corrosion resistance of the alloy processed through DMLS was significantly better than the cast counterpart. This was attributed to the fine microstructure produced by DMLS, uniform distribution of the fine Si particles without formation of any intermetallic, due to the extremely rapid cooling and solidification rate during DMLS process and slightly lower Fe and Cu concentration of the AlSi10Mg alloy. In contrast, the A360.1 cast Al alloy samples experienced severe localized corrosion of the Al matrix in the periphery of the Fe containing IMC and Si flakes. The results also highlighted improved corrosion resistance of the as-printed DMLS sample compared with that of the as-ground one.

Synergistic effects of composition and heat treatment on microstructure and properties of vacuum die cast Al-Si-Mg-Mn alloys

The purpose of this study was to prepare high-quality Al-Si-Mg-Mn alloy with a good combination of strength and ductility employing the vacuum-assisted high-pressure die cast process. An orthogonal study of heat treatments was conducted to design an optimized T6 heat treatment process for both AI-10%Si-0.3%Mg-Mn and AI-11%Si-0.6%Mg-Mn alloys. The results demonstrate that no obvious blisters and warpage were observed in these two alloys with solid solution treatment. After the optimal T6 heat treatment of 530°Cx3h + 165°Cx6h, AI-11%Si-0.6%Mg-Mn alloy has better mechanical properties, of which tensile strength, yield strength and elongation reached 377.3 MPa, 307.8 MPa and 9%, respectively. The improvement of mechanical properties can be attributed to the high density of needle-like β(Mg5Si6) precipitation after aging treatment and the fine and spherical eutectic Si particles uniformly distributed in the α-AI matrix.

Size dependence of microstructure of AlSi10Mg alloy fabricated by selective laser melting

In order to investigate the size dependence of microstructure of the AlSi10Mg alloy fabricated by selective laser melting (SLM) combined with a powder bed technique, plate-shaped AlSi10Mg alloy samples with various widths (ranging from approximately 10mm to 0.3mm) were produced in this study. All the fabricated samples exhibited characteristic microstructural morphologies consisting of melt pools with columnar α-Al grains surrounded by fine eutectic Si particles, whereas their sample sizes had a relatively small effect on the texture and average grain size of the α-Al matrix. However, the formation of fine Si precipitates inside the columnar α-Al grains was observed more often for the smaller-sized samples, which could be a possible dominant contributor to the observed softening of the sample by reducing sample size. The obtained results were utilized for discussing the size dependence of the strength of the SLM-manufactured porous alloy samples.

Hybrid multi-objective optimization of microstructural and mechanical properties of B4C/A356 composites fabricated by FSP using TOPSIS and modified NSGA-II

Abstract A356 alloy was used as the base metal to produce boron carbide (B4C)/A356 composites using friction stir processing (FSP). The microstructural and mechanical properties of B4C/A356 composites were optimized using artificial neural network (ANN) and non-dominated sorting genetic algorithm-II (NSGA-II). Firstly, microstructural properties of the composites fabricated in different processing conditions were investigated. Results show that FSP parameters such as rotational speed, traverse speed and tool pin profile significantly affect the size of the primary silicon (Si) particles of the base metal, as well as the dispersion quality and volume fraction of reinforcing B4C particles in the composite layer. Higher rotational to traverse speeds ratio accompanied by threaded pin profile leads to better particles distribution, finer Si particles and smaller B4C agglomerations. Secondly, hardness and tensile tests were performed to study mechanical properties of the composites. FSP changes the fracture mechanism from brittle form in the as-received metal to very ductile form in the FSPed specimens. Then, a relation between the FSP parameters and microstructural and mechanical properties of the composites was established using ANN. A modified NSGA-II by incorporating diversity preserving mechanism called the ɛ elimination algorithm was employed to obtain the Pareto-optimal set of FSP parameters.

Ductilizing of cast hypereutectic Al–17%Si alloy by friction stir processing

In present research work, multi-pass friction stir processing was utilized for the as-cast Al–17%Si alloy. The multi-pass friction stir processing reproduced the aluminum (Al) matrix with a uniform distribution of the ultra-fine silicon (Si) particles. The multi-pass friction stir processing also resulted in the formation of refining cast microstructure with negligible porosity. The significant reduction in silicon particle size was measured and it reduced from 204 µm to 0.86 µm after the first pass and up to 0.30 µm after two pass friction stir processing. The frequency of fine Si particles was increased after two pass friction stir processing as compared to single pass friction stir processing. The engineering stress–strain curves revealed a significant enhancement in ductility and strength after one and two passes of friction stir processing as compared to the as-cast alloy. After one and two passes of friction stir processing, the ultimate tensile strength of as-cast alloy was enhanced by 24% and 31% and ductility was increased by 300% and 500%, respectively. The secondary electron micrograph of fracture surfaces of tensile specimens was taken before and after friction stir processing. The fractographs revealed the transformation from brittle mode to ductile dimples fracture after the multi-pass friction stir processing process.

Change in microstructure of selectively laser melted AlSi10Mg alloy with heat treatments

In the present study, we examined changes in the microstructure and mechanical properties of AlSi10Mg alloy, initially fabricated using selective laser melting (SLM) combined with a powder-bed system, by applying heat treatments at temperatures of either 300 or 530°C. The as-fabricated samples exhibited a characteristic microstructural morphology and {001} texture. Melt pools corresponding to the locally melted and rapidly solidified regions were found to be composed of several columnar α-Al grains surrounded by fine eutectic Si particles. A fine dislocation substructure consisting of low-angle boundaries is present within the columnar α-Al grains. At elevated temperatures, fine Si phase precipitates within the columnar α-Al phase and coarsening of the eutectic Si particles occurs. These fine Si particles inhibit grain growth in the α-Al matrix, resulting in the microstructural morphology and [001] texture observed in the heat-treated samples. The dislocation substructure disappears in the columnar α-Al grains. Furthermore, the formation of a stable intermetallic phase occurs, reaching microstructural equilibrium after long-term exposure. The as-fabricated specimen exhibits a high tensile strength of approximately 480MPa. The strength is independent of the tensile direction, that is, normal and parallel to the building direction. In contrast, the tensile ductility is found to be direction-dependent, and is therefore responsible for a fracture preferentially occurring at a melt pool boundary. The direction-dependence of the tensile ductility was not found in the specimen that had been heat-treated at 530°C. The present results provide new insights into the control of the direction-dependence of the tensile properties of AlSi10Mg alloys fabricated by SLM.

EFFECT OF THIXOFORMING ON THE WEAR PROPERTIES OF AL-SI-CU ALUMINUM ALLOY

In this study a hypoeutectic Al-6Si-3Cu aluminium alloy was synthesized using two different routes: the thixoforming process and the conventional mould casting process. The microstructural features, hardness and wear behavior of thixoformed alloy have been evaluated and compared with that of as-cast alloy. Cooling slope method was used to produce the non-dendritic microstructure feedstock for thixoforming. Thixoforming was carried out at 50% liquid fraction. The dry sliding wear behaviour of the produced alloys was investigated under two loads; namely, 10 and 50 N and 1m/s sliding speed for 9 km sliding distance. The thixoformed alloy exhibited globular primary phase morphology with fine and uniform distributed Si and intermetallic particles. On the contrary, dendritic primary phase, coarse flaky silicon particles and segregated microstructure has been observed in conventional cast alloy. Thixoformed alloy exhibited improvement in the wear resistance in comparison to the conventional cast alloy, which may be attributed to the microstructural enhancement resulting in improved hardness. The thixoformed samples displayed lower volume loss of ~16.20 mm3 and ~42.40 mm3 at loads of 10 and 50 N respectively compared with that of conventional cast samples. On the basis of observations and analyses on the wear rates and worn surfaces, the wear mechanism of the alloys was dominantly controlled by abrasive, adhesive and minor delamination.

Improvement in formability of semi-solid cast hypoeutectic Al-Si alloys by equal-channel angular pressing

Microstructure of Al-Si alloys are characterized by brittle eutectic Si particles. It is known that morphological change of Si particles from coarse acicular flake to fine fiber improves strength and ductility at once. To control the morphology without alloying, combined effects of semi-solid casting and severe plastic deformation were investigated in this study. The authors prepared a semi-solid JIS AC4CH cast alloy (Al-7.14%Si-0.41%Mg) with fine Si particles and a conventional cast alloy with coarse Si particles. The both alloys were processed through warm equal-channel angular pressing (ECAP) under several thermo-mechanical histories. Microstructure evolution by ECAP was evaluated in relation to deformation behavior.ECAP process was not able to refine Si particles of the conventional cast alloy as fine as those of the semi-solid cast alloy. Submicron Si particles in the semi-solid cast AC4CH slightly coarsened by warm ECAP. Combination of semi-solid casting and ECAP process provided refinement of Si particles, grain refinement of primary phase, and decrease of hardness difference between primary phase and eutectic. Controlling ECAP processing conditions improved strength and/or ductility and enabled flexible design of mechanical properties of semi-solid AC4CH.

New Method of Eutectic Silicon Modification in Cast Al–Si Alloys

The aim of the present work was to investigate various means of obtaining a fine eutectic silicon structure in A356.2 alloy and therefore improve the alloy mechanical properties. The effects of solidification rate, Sr modification and melt thermal treatment (MTT) on the silicon particle characteristics of A356.2 (Al–7 %Si–0.4 %Mg) alloy were studied. The particle characteristics measured were the average particle area, average particle length, average particle roundness and average particle aspect ratio, using image analysis and optical microscopy. The results showed that Sr modification-, superheat- and Sr modification-MTT (SrMTT)-processed castings provide fine eutectic Si particles, the SrMTT process giving the best modification results. Both size and morphology of the eutectic silicon particles are affected by the modification process used. The Sr-grain-refined, Sr-melt superheat and SrMTT castings show well-modified fibrous Si particles, whereas the MTT casting exhibits Si particles that, although refined to a certain extent, still retain their acicular morphology. Solidification rate affects the eutectic Si particle size in that a higher solidification rate produces finer Si particles. However, within the range of solidification rates provided by the end-chill mold used in this work, the solidification rate does not affect the morphology of the Si particles.

Effects of intermetallic phases on the electrochemical properties of rapidly-solidified Si-Cr alloys for rechargeable Li-ion batteries

The microstructures and the electrochemical properties of rapidly-solidified Si-Cr alloys of various compositions were investigated in order to elucidate the effects of intermetallic phases on the cyclic energy capacity of the materials. Rapidly-solidified ribbons of the alloys were prepared by using a melt-spinning process, which is one of the most efficient rapid-solidification processes. The ribbons were fragmented by using a ball-milling process to produce powders of the alloys. To examine the electrochemical characteristics of the alloys, we mixed each of the alloy powders with Ketjenblack®, a conductive material, and a binder dissolved in deionized water and used it to form electrodes. The electrolyte used was 1.5-M LiPF6 dissolved in ethyl carbonate/dimethyl carbonate/fluoroethylene carbonate. The microstructures and the phases of the alloys were analyzed by using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analyses. The obtained results showed that the microstructures of the rapidly-solidified Si-Cr alloys were composed of Si and CrSi2 phases. Fine Si particles with diameters of 50 − 100 nm were observed in an eutectic constituent while the sizes of the primary Si and CrSi2 phases were relatively larger at 500 − 900 nm. The specific energy capacities (C) of the Si-Cr alloys decreased linearly with increasing volume fraction (f) of the CrSi2 phase as follows: C = −1,667f + 1,978 after the 50th cycle. The Columbic efficiency after the 3rd cycle increased slightly with increasing volume fraction of the CrSi2 phase; this was effective in improving the cycling capacity of the Si particles.

Evolution of microstructure and mechanical properties in a hypoeutectic Al–Si–Mg alloy processed by accumulative back extrusion

This study demonstrates the evolution of microstructure and mechanical properties of a hypoeutectic Al–7Si–0.4Mg (A356) alloy processed by accumulative back extrusion (ABE) at temperatures ranging from 200 to 500°C. ABE processing is one of the new severe plastic deformation techniques enabling one to produce relatively large ultrafine-grained materials in a cylindrical shape. One complete pass of ABE was estimated to introduce a reasonably homogeneous effective strain of ~3 as calculated by finite element analysis. Microstructural observation showed that globular α-Al primary phase was subdivided into fine substructures and Si particles having a fibrous shape were fragmented and spheroidized within the eutectic constituent through ABE processing. There was no evidence of homogeneous distribution of the fine Si particles in the α-Al phase after ABE. Mechanical testing at room temperature showed that both yield strength and ultimate tensile strength of the A356 alloy dramatically increased through ABE, especially at lower processing temperatures, as compared with the as-cast condition whereas there was no significant reduction in ductility at all processing temperatures. The experimental results were discussed with emphasis on the microstructure evolution involving dynamic recrystallization and deformation behavior including strengthening mechanisms and strain hardening in the Al–Si alloy.

Improving wear performance of dual-scale Al–Sn alloys by adding nano-Si@Sn: Effects of Sn nanophase lubrication and nano-Si polishing

In this work, an attempt was made to further promote the wear and friction behavior of dual-scale structured Al–12wt% Sn bearing alloys by coupling with a nano-Si@Sn composite. A so-called tri-modal Al–Sn–Si (denoted as CG-30 Si-containing alloy), which exhibited increased bulk hardness and improved distribution and refinement of the Sn phase, was produced by combining mechanical alloying and conventional powder sintering. The wear performance of the Si-containing and Si-free alloys was differentiated by performing both block-on-ring and ball-on-disk testing. Moreover, the addition of nano-Si@Sn composites to the dual-scale Al–Sn matrix resulted in significant reductions of the friction coefficient and wear volume. These improvements in wear behavior stemmed from the polishing effect of fine Si particles on the counterface, and Sn-rich clusters that acted as lubricants on the worn surface; together, the polishing effect and lubrication led to the formation of a smooth tribolayer, and hence, a decrease in the tendency for abrasive wear. Abrasive wear was also reduced by an increase in the alloy hardness with the addition of Si. As such, Sn-phase modification via Si addition constitutes a promising method for preparing self-lubricating Al-based alloys.

Characterization of Si particles and their effects on and recrystallization in a nanostructured cold rolled Al-1% Si alloy

An Al-1.08 vol.% Si alloy was cold rolled to a reduction of 98% (εvM = 4.5) and then annealed at different temperatures up to 210°C (0.52 Tm) for different times. The deformed structure is characterized by a nanoscale lamellar structure with the presence of Si particles of coarse (> 1 μm), medium (100 nm - 1 μm) and fine (< 100 nm) sizes in the microstructure. Deformation zones are formed around the coarse Si particles and the boundary spacing is finer in the deformation zone than in the matrix. The medium Si particles have little effect on the morphology and boundary spacing. The fine Si particles are aligned along the lamellar boundaries indicating a stabilizing effect on the structural refinement during cold rolling. After annealing, enhanced recovery occurs in the deformation zones around the coarse Si particles. However the reduction in stored energy during recovery and the pinning effect of fine Si particles on the boundary migration prevent the advantage of particle stimulated nucleation (PSN) of coarse Si particles in the nanoscale lamellar structure. This study also demonstrates an important effect of the fine particles in delaying both recovery and recrystallization processes. This effect diminishes with increasing annealing temperature and coarsening the fine particles especially at triple junctions.

Electrically exploded silicon/carbon nanocomposite as anode material for lithium-ion batteries.

In this work, silicon (Si) containing carbon coated core-shell nanostructures were synthesized by electrical explosion of Si wires in ethanol solution followed by high energy mechanical milling (HEMM) process. Material characterization was carried-out using transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. HEMM led to very fine and amorphous Si particles in the presence of carbon and inactive Silicon-Carbide (SiC) matrix. These Si based nanocomposites, obtained through electrical explosion followed by HEMM (milled sample), exhibited enhanced electrochemical performance than unmilled nanocomposites, when evaluated as anode material for lithium-ion batteries (LIBs). On completion of (the) 1st cycle, milled and unmilled sample(s) showed specific discharge capacities around 825 mAh/g and 717 mAh/g, respectively. Interestingly, the coulombic efficiencies of milled and unmilled samples were 98.5% and 97% after 60th cycle respectively. The enhanced electrochemical performance is attributed to fine and amorphous Si based nanocomposite obtained through HEMM process.

Reinforcement of Hypereutectic Al-Si Alloys with Fe-Bearing Compounds and Si Particles Assisted with Ultrasonic Treatment

The hypereutectic Al-17Si-2Cu-1Ni-0.8Mn alloys with 2% or 3%Fe were fabricated out assisted with ultrasonic vibration (USV) treatment. The coarse plate-like δ-Al4(Fe,Mn)Si2 phase was transformed into fine particles with average diameter of about 17μm~20μm after USV treatment, and the volume fraction of particle-like Fe-bearing compounds is about 3.6%~5%. The polygonal primary Si crystals were also refined into particles with average diameter of about 15μm~23μm, and the volume fraction of primary Si declined to about 5.4%~6.5% after USV treatment. The matrixes of the castings were reinforced with fine Fe-bearing compounds and Si particles. The ultimate tensile strength of the alloys, which were produced by gravity casting process assisted with USV, increases with the increase of Fe content at 350 °C. It is considered the increase of the elevated temperature strength of the samples are mainly attributed to the refinement of δ-Al4(Fe,Mn)Si2 phase by USV and the increase of the volume fraction of the Fe-bearing compounds. The die casting process assisted with USV can further improve the mechanical properties of Al-17Si-2Fe-2Cu-1Ni-0.8Mn alloy.

Effect of Melt Thermal Treatment on Eutectic Silicon Particles Characteristics in Cast Al-Si-Mg Alloys

A new means of obtaining fine Si particles is through the use of a melt thermal treatment (MTT), where the mixing of low and high temperature alloy melts produces a fine Si structure. Modification is achieved by nuclei resulting from the degeneration of large atom clusters and some refractory solids in the low temperature melt when it is heated by the high temperature melt. This is a relatively recent technique which demonstrates promise as an alternative to Sr-modification, as it requires no element addition, thus reducing the risk of increased porosity normally associated with the addition of strontium to the melt. The use of melt superheat is also found to produce refinement of the eutectic Si structure. In this case, the high melt temperature assists in the degeneration of atom clusters, providing more nuclei for α-Al dendrite formation, and a resulting refinement of the microstructure. KeywordsMelt Thermal Treatment; Melt Superheat; Sr Modification Eutectic Si Particle Characteristics