Silicon Powder Research Articles

Electrochemical Preparation of Nano-Sized Silicon as a Lithium-Ion Battery Anode Material

Highly pure silicon is an important component in photovoltaic applications and has potential in battery technology. In this study, the electrochemical behavior of Si (IV) was discussed in a NaF−LiF−Na2SiO3−SiO2 electrolyte at 750 °C, and lithium-ion battery performance with electrodeposited silicon powder as anode material were investigated. The cyclic voltammograms illustrated that the reduction of Si(IV) on an Ag electrode followed an irreversible two-step, two-electron process: Si(IV) → Si(II) and Si(II) → Si(0). Both reduction steps involved diffusion control, and the diffusion coefficients were 1.18 and 1.22 × 10−6 cm2 s−1, respectively. Nanoscale spherical silicon was deposited between potentials of −1.0 to −1.6 V (vs Pt) with support of X-ray diffraction patterns, Raman spectra, and scanning electron microscopy analysis. Combining the fabricated silicon with carbon, a Si@C composite anode material for lithium-ion batteries was prepared, and its specific capacity reached 1260 mA·h g−1. Notably, a capacity of 200 mA·h g−1 was maintained over 100 cycles.

A solid-state approach for the low temperature synthesis of Cr3Si hollow particles

Abstract In this paper, pure cubic chromium silicide (Cr3Si) hollow particles have been successfully synthesized through the solid-state reaction of chromium sesquioxide, silicon powder and metallic lithium in an autoclave at 600 °C for 10 h. The as-prepared samples were characterized by means of X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy, which showed that the as-prepared samples were cubic phase Cr3Si hollow particles. Furthermore, the oxidation resistance of the obtained Cr3Si sample was also investigated.

A nanosilver-actuated high-performance porous silicon anode from recycling of silicon waste

The global need for improved fuels has promoted the development of the renewable photovoltaic industry. However, a significant amount of diamond wire saw silicon powder (DWSSP, ∼300,000 t/a) is produced during the process of solar cell manufacturing. Thus, there is a significant need for strategies to recycle and use DWSSP for increased sustainability and protection of the environment. Here, nanoporous silicon (PSi) composites materials derived from silicon cutting waste were used to fabricate lithium-ion anodes with high capacity and stable cycling performance. DWSSP was chemically crushed using nanocopper-assisted etching. Next, porous PSi/Ag composites were prepared by nanosilver-assisted etching, using dopamine as a source of organic for surface coating. Carbon-coated PSi/Ag nanocomposites (PSi/Ag/C) exhibited excellent cycling performance with a retained discharge capacity of 1092.9 mAh g−1 after 300 cycles at 1000 mA/g, with a capacity retention rate of 80%. These results indicate that PSi/Ag/C from DWSSP can be used to prepare functional lithium-ion battery anodes. This work describes the high-value utilization of an abundant waste material produced in the solar industry and provides an effective strategy to produce porous materials for energy storage.

Hydrogen storage capability of porous silicon powder fabricated from Al–Si alloy

Porous silicon powder has been fabricated from an Al–Si alloy by etching in strong acids, and its hydrogen storage capacity has been studied. Double acid etching in the fabrication and nickel blending have been proposed to further enhance the hydrogen storage capacity of the etched powder. The etching effectively removed the aluminum from the Al–Si alloy to form a porous Si structure, with a large increase in surface area. After charging under a hydrogen pressure of 3.7 MPa at 150 °C, the hydrogen uptake of double-etched and Ni-blend porous silicon samples was 0.81 wt%, which was >13 times higher than that of the as-received Al–Si alloy (0.06 wt%). The percentage of retained hydrogen after desorption was also largely decreased. The results of this study provide strong evidence on the potential of using porous silicon powder from Al–Si alloy as a cost-effective solid-state storage material for hydrogen.

Experimental Investigation on Silicon Powder Mixed-EDM of Nimonic-90 Superalloy

Powder mixed electrical discharge machining (PM-EDM) is a technological advancement in electrical discharge machining (EDM) processes where fine powder is added to dielectric to improve the machining rate and surface quality. In this paper, machining of Nimonic-90 was carried out using fabricated PM-EDM, setup by adding silicon powder to kerosene oil. The influence of four input process parameters viz. powder concentration (PC), discharge current (IP), spark on duration (SON), and spark off duration (SOFF) has been investigated on surface roughness and recast layer thickness. L9 Taguchi orthogonal and grey relational analysis have been employed for experimental design and multi-response optimization, respectively. With the addition of silicon powder to kerosene oil, a significant decrease in surface roughness and recast layer thickness was noticed, as compared to pure kerosene. Spark on duration was the most significant parameter for both surface roughness and the recast layer thickness. The minimum surface roughness (3.107 µm) and the thinnest recast layer (14.926 μm) were obtained at optimum process parameters i.e., PC = 12 g/L, IP = 3 A, SON = 35 μs, and SOFF = 49 μs using grey relational analysis.

Solid State NMR Analysis for Hide Powder Tanned by Aluminum, Silicon and Phosphorus Tanning Agents before and after Hydrothermal Denaturation

In order to investigate the change of chemical bonds between tanning agents and collagen molecules directly, hide powder tanned by aluminum, silicon and phosphorus tanning agents were prepared. The chemical shifts of Al, Si and P in tanned hide powder were analyzed by solid-state 27Al NMR, 29Si NMR and 31P NMR. The results showed that, the chemical shift of Al in aluminum tanned hide powder which interacted with collagen molecules through coordination bond could be regarded as unchanging after hydrothermal denaturation (only slightly moved to high field area). The chemical shift of Si in silicon tanned hide powder which interacted with collagen molecules through hydrogen bond did not change after hydrothermal denaturation. The chemical shift of P in phosphorus tanned hide powder, which interacted with collagen molecules through covalent bond, was obviously shifted to the high field area after hydrothermal denaturation.

Use of the active-phase Cu3Si alloy as superior catalyst to direct synthesis of trichlorosilane via silicon hydrochlorination

Here we report the first synthesis of nearly pure-phase Cu3Si alloy that can be a highly efficient catalyst in the hydrochlorination of silicon reaction. This material was prepared by a high-temperature (1050 ​°C) calcination method in which copper and silicon powders were used as the reactants. The X-ray photoelectron spectroscopy (XPS) study revealed that the Cu and Si atoms in the Cu3Si alloy carried part of positive and negative charge, respectively. When employed as the catalyst in the silicon hydrochlorination to SiHCl3 (TCS) for the production of Si polycrystals for Solar cell, the sample Cu3Si exhibited excellent low-temperature catalytic performance: the Si conversion and TCS selectivity respectively achieved 41.1% and 96.1% at 250 ​°C. Notably, its TCS yield at 250 ​°C was 1.2 times higher than that of the industrial catalyst-free system at 350 ​°C. Detailed analysis of the reaction process showed that the positively charged Cu atoms and negatively charged Si atoms in Cu3Si alloy could cleave the H–Cl bond in the reactant HCl and make the combination of H and Cl atom with Si atoms easier. Meanwhile, the reaction between the remaining Cu atom and Si was accelerated, leading to the generation of more active Cu6.69Si and ultimately superior catalytic performance. This work deepens the fundamental understanding of the hydrochlorination of silicon reaction, and provides an avenue for the synthesis of Si-based alloy catalysts.

Lanthanum/titanium dioxide immobilized onto industrial waste with enhanced photocatalytic activity, and the degradation of dimethyl phthalate

Titanium dioxide (TiO2) is an effective photocatalyst for organic removal. However, its efficacy is hampered by the recombination of photogenerated electrons and holes. This paper presented an eco-friendly, synthetic lanthanum (La)/TiO2 supported on lithium silicon powder (L) to significantly improve photocatalysis. The results showed that 74.4% dimethyl phthalate (DMP) removal was achieved in the ultraviolet (UV)-La-TiO2/L (LTL1) system, which was considerably higher than UV-TiO2/L (TL) (60.1%) and UV-L (18.3%). The enhanced LTL1 photocatalysis was based on the synergic effect between TiO2 and La with L matrix. The photocatalysis efficiency was further improved by hydrogen peroxide (H2O2), while the DMP removal rate reached 100% in the UV-LTL1-H2O2 system. The DMP activation mechanisms and degradation pathways in the UV-LTL1-H2O2 system were carefully examined, revealing that increased hydroxyl free radical (OH•) and superoxide ion radicals (O2−•) were pivotal to the higher degradation rate. Overall, the findings suggested that LTL1 showed considerable application promise for the low-cost and eco-friendly organic removal from water.

Metallic Silicon Powder Produced by Vacuum Decomposition of Magnesium Silicide Prepared by Magnesiothermic Reduction

Metallic Silicon Powder Produced by Vacuum Decomposition of Magnesium Silicide Prepared by Magnesiothermic Reduction

DESIGN AND PRODUCTION OF MULTI MATERIAL 3D PRINTER FOR SOFT ROBOTIC STRUCTURAL ELEMENTS

With the latest technology, the development and interest in soft robots have gained speed. Flexible robots are generally produced by the casting method. This traditional production method cannot meet the required quality and production speed. For this, it is aimed to solve the problem by accelerating the production of robots without decreasing the quality. The most successful method for solving this problem is 3D printers, which could print multiple materials. It was decided to be used multi-materials printing, and the system design was carried out. This study aims to design and produce a multi-material 3D printer capable of printing non-conductive and conductive rapidly curing silicone that can be used in soft robotics and medical simulators. The electrical conductivity was achieved by mixing silicone and graphite powder. The parts in the designed system are also obtained by the additive manufacturing method. Test pieces were printed using the produced 3D printer. Specific tests have been carried out on the produced parts. Technical data such as strength, elasticity, electrical conductivity have been obtained.

Binder Jetting of Custom Silicone Powder for Direct Three-Dimensional Printing of Maxillofacial Prostheses.

Recent advances in digital workflow have transformed clinician's ability to offer patient-specific devices for medical and dental applications. However, the digital workflow of patient-specific maxillofacial prostheses (MFP) remains incomplete, and several steps in the manufacturing process are still labor-intensive and are costly in both time and resources. Despite the high demand for direct digital MFP manufacturing, three-dimensional (3D) printing of colored silicone MFP is limited by the processing routes of medical-grade silicones and biocompatible elastomers. In this study, a binder jetting 3D printing process with polyvinyl butyral (PVB)-coated silicone powder was developed for direct 3D printing of MFP. Nanosilica-treated silicone powder was spray dried with PVB by controlling the Ohnesorge number and processing parameters. After printing, the interconnected pores were infused with silicone and hexamethyldisiloxane (HMDS) by pressure-vacuum sequential infiltration to produce the final parts. Particle size, coating composition, surface treatment, and infusion conditions influenced the mechanical properties of the 3D-printed preform, and of the final infiltrated structure. In addition to demonstrating the feasibility of using silicone powder-based 3D printing for MFP, these results can be used to inform the modifications required to accommodate the manufacturing of other biocompatible elastomeric materials.

Reversible kinetics and rapid tunnelling characteristics of silicon doped magnesium-titanium nanocomposites prepared by mechanical alloying route for nickel-metal hydride batteries

Magnesium-Titanium-Silicon (Mg-Ti-Si) hybrid nanocomposites have been synthesized by using high energy ball milling. Magnesium, titanium and silicon powder mixtures are taken in the stoichiometric molar ratio of Mg0.8-xTi0.2Six (x = 0, 0.10, 0.15, 0.20 and 0.25) and mechanically milled for 30 h. The phase transformation, micro-strain and microstructural changes during mechanical alloying are examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). Band gap engineering is a process done by high energy ball milling of Mg0.8Ti0.2, Mg0.8-xTi0.2Six powders, which have been tailored from 0.629 to 1.685 eV, which are obtained from the optical absorption spectra. The band gap energy is the most substantial parameter to understand the electrochemical charge-discharge activation behaviour. The high planar diffusion with high reversible reaction has been occurred only for the 30 h ball milled Mg0.70Ti0.20Si0.10 and Mg0.65Ti0.20Si0.15 powders. During the oxidation behaviour, they have been gained the higher diffusion coefficient (1.87 × 10−08 cm2 s−1 and 1.53 × 10−08 cm2 s−1), high exchange ion current density (1841 mA g−1 and 1113 mA g−1), the patronizing maximum discharge capacity (329 mAh g−1 and 307 mAh g−1), maximum energy density (0.265 Wh g−1 and 0.219 Wh g−1) with high quasi-reversible coulombic efficiency (65.80% and 61.40%) and high cyclic stability (87.23% and 82.08%) respectively. The addition of silicon concentration increases (i.e. x = 0.10–0.25) in magnesium-titanium based ball milled powders enhance the activation behaviour and robustly reduce the Gibbs free energy from −127 to −64 kJ mol−1.

Carbonization Behavior in Microwave Heating of Silicon Powder

Carbonization Behavior in Microwave Heating of Silicon Powder

Certification of a Natural Silicon Reference Material with SI‐Traceable Isotopic Composition

Silicon (Si) is the second most abundant element in the continental crust. Studies have illustrated that silicon isotopes have a potential to be tracers in the biogeochemical silica cycle. This paper details a developed method for the production and certification of a new Si reference material with natural‐like isotopic composition using a fully calibrated multi‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS). To correct for the mass bias effect, three blend solutions were gravimetrically prepared with isotopically enriched 28Si, 29Si and 30Si materials. Homogeneity and stability tests were performed, and no significant influences were found. Uncertainties of property values were evaluated, and the traceability to the International System of Units (SI) was established. The developed certified reference material (GBW04503) is a silicon powder (≈ 300 mesh) with high purity (≈ 0.999 99 kg kg−1), which can be used in silicon isotopic measurement to support validation of analytical procedures and/or quality control of gas source mass spectrometry (GS‐MS) or MC‐ICP‐MS. The certified isotope amount ratios of n(29Si)/n(28Si) and n(30Si)/n(28Si) are 0.050291(12) mol mol−1 and 0.033397(16) mol mol−1, respectively, (k = 2), and the certified isotope amount fractions of silicon are 92.2776(20)% (28Si), 4.6407(10) % (29Si) and 3.0818(14)% (30Si) (k = 2). Meanwhile, the delta value of δ30/28SiNBS 28 = 1.679(17)‰ was obtained (k = 2).

Beyond Thin Films: Clarifying the Impact of c-Li15Si4 Formation in Thin Film, Nanoparticle, and Porous Si Electrodes

The formation of the c-Li15Si4 phase has well-established detrimental effects on the capacity retention of thin film silicon electrodes. However, the role of this crystalline phase with respect to the loss of capacity is somewhat ambiguous in nanoscale morphologies. In this work, three silicon-based morphologies are examined, including planar films, porous planar films, and silicon nanoparticle composite powder electrodes. The cycling conditions are used as the lever to induce, or not induce, the formation of c-Li15Si4 through application of constant-current (CC) or constant-current constant-voltage (CCCV) steps. In this manner, the role of this phase on capacity retention and Coulombic efficiency can be determined with few other convoluting factors such as alteration of the composition or morphology of the silicon electrodes themselves. The results here confirm that the c-Li15Si4 phase increases the rate of capacity decay in planar films but has no major effect on capacity retention in half-cells based on porous silicon films or silicon nanoparticle composite powder electrodes, although this conclusion is nuanced. Besides using a constant-voltage step, formation of the c-Li15Si4 phase is influenced by the dimensions of the Si material and the lithiation cutoff voltage. Porous Si films, which, in this work, comprise primary Si particle sizes that are smaller than those in the preformed Si nanoparticle slurries, do not undergo the formation of c-Li15Si4 at 50 mV, whereas Si nanoparticle slurries are accompanied by the formation of c-Li15Si4 up to 80 mV. The solid-electrolyte interphase (SEI) formed from reaction of the c-Li15Si4 with the carbonate-based electrolyte causes polarization in both nanoparticle and porous film silicon electrodes and lowers the average Coulombic efficiency. A comparison of the cumulative irreversibilities due to SEI formation between different lithiation cutoff voltages in silicon nanoparticle slurry electrodes confirmed the connection between higher SEI buildup and formation of the c-Li15Si4 phase. This work indicates that concerns about the c-Li15Si4 phase in silicon nanoparticles and porous silicon electrodes should mainly focus on the stability of the SEI and a reduction of irreversible electrolyte reactions.

Study on the preparation technology and high temperature oxidation characteristics of SiB4 powders

High purity SiB4 powder is the key raw materials for high temperature resistant coating of rigid ceramic insulating tile, which plays the role of forming a dense coating and self-healing in the coating. Therefore, to obtain SiB4 powders with high performance and high purity at the same time can solve the problem of raw materials for high temperature resistant coating in China. However, the preparation process of SiB4 powder is complex, and no domestic manufacturer can produce it, which greatly limits the development of related industries in China. The relationship between SiB4 phase purity and boron-silicon ratio of raw materials, particle size and sintering process parameters in the synthesis of high-purity SiB4 powders was explored. The experimental results show that the yield of SiB4 can be significantly improved and the decomposition of SiB4 can be inhibited by adjusting the crystallinity of boron powder, particle size of raw material, sintering process parameters and the ratio of boron to silicon. When 1μm boron powder and 1μm silicon powder are used, the ratio of boron to silicon is 3.5:1, and the sintering process is 1320 °C - 2h, the high purity sib4 powder with only SiB4 phase detected by XRD phase analysis can be prepared after acid washing. On this basis, the high temperature oxidation characteristics of the prepared SiB4 powder were studied. The experimental results show that SiB4 powder can be oxidized at 1100 °C to form B2O3-SiO2 glass phase, which proves that it has better high temperature oxidation performance. In conclusion, it was proved that the prepared SiB4 powder had high purity and excellent high temperature resistance, which could be used for further production research.

Nano-Porous-Silicon Powder as an Environmental Friend.

Nano-porous silicon (NPS) powder synthesis is performed by means of a combination of the ultra-sonication technique and the alkali chemical etching process, starting with a commercial silicon powder. Various characterization techniques {X-ray powder diffraction, transmission electron microscopy, Fourier Transform Infrared spectrum, and positron annihilation lifetime spectroscopy} are used for the description of the product’s properties. The NPS product is a new environmentally friendly material used as an adsorbent agent for the acidic azo-dye, Congo red dye. The structural and free volume changes in NPS powder are probed using positron annihilation lifetime (PALS) and positron annihilation Doppler broadening (PADB) techniques. In addition, the mean free volume (VF), as well as fractional free volume (Fv), are also studied via the PALS results. Additionally, the PADB provides a clear relationship between the core and valence electrons changes, and, in addition, the number of defect types present in the synthesized samples. The most effective parameter that affects the dye removal process is the contact time value; the best time for dye removal is 5 min. Additionally, the best value of the CR adsorption capacity by NPS powder is 2665.3 mg/g at 100 mg/L as the initial CR concentration, with an adsorption time of 30 min, without no impact from temperature and pH. So, 5 min is the enough time for the elimination of 82.12% of the 30 mg/L initial concentration of CR. This study expresses the new discovery of a cheap and safe material, in addition to being environmentally friendly, without resorting to any chemical additives or heat treatments.

Removal of As(V) Based on Amino-Group Surface-Functionalized Porous Silicon Derived from Photovoltaic Silicon Cutting Powder

In this study, amino group surface-functionalized porous silicon adsorbent was successfully prepared for the first time using diamond wire saw silicon powder (DWSSP) as raw material through copper-assisted chemical etching (Cu-ACE) and organic functional group grafting. Amino-functionalized porous silicon adsorbent (TEPA-GTS-NPSi) can be used for removing As(V) from water. The properties and mechanism of the new adsorbent were characterized by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (FE-SEM), Brunauer–Emmett–Teller analysis (BET), and thermogravimetric analysis (TGA). The concentration of metal ions in the solution was determined by inductively coupled plasma spectrometry. Meanwhile, the effects of initial pH, adsorption time, initial concentration and adsorbent dosage on the removal of As(V) in an aqueous solution were studied by intermittent adsorption experiments. The results showed that the adsorption equilibrium could be reached rapidly after 30 min soaking. Under the optimized pH of 7, the maximum adsorption capacity was 13.2 mg/g, and the minimum adsorption limit was 3 mg/L. The adsorbent shows good adsorption performance after five successive regenerated cycles. Based on the density functional theory (DFT) analysis results, the adsorption mechanism is attributed to hydrogen bond interaction between the NH2 group and As(V) ions.

Anisotropic wet etching of a novel micro-texture structure for an Al/n-Si/Al metal–semiconductor–metal photodetector fabrication

Micro-electro-mechanical system fabrication involves molding on a single substrate. Chemical wet etching is common in these systems because it can provide a very high etch rate and selectivity. This optical device has been successfully completed fabrication by using the single-step lithography process. The surface was coated with PR and patterned using a single mask to create U-shaped structures by a wide electrode gap on a silicon substrate. Then it was etched using anisotropic wet etching process in potassium hydroxide, tetramethylammonium hydroxide (TMAH), silicic acid and dissolved silicon powder. The etchant created a 58% increase in the light sensitive area of the U-shaped trench in the structure higher compared to the planar structure. Random micro-pyramids, formed on the silicon surface in the U-shaped structure by the silicic acid-added TMAH solution, led to a ∼254 times higher ratio between photon generated current and dark current at reverse bias. This processing technique is a promising technology for improving performance for next-generation optical sensors or silicon photodetector.

PP/POE thermoplastic elastomer prepared by dynamic vulcanization and its flame retardant modification

Flame retardant thermoplastic elastomer (TPE) with excellent mechanical properties and thermal oxidative aging resistance was prepared by dynamic vulcanization technology with ethylene-octene copolymer (POE) and polypropylene (PP) as raw materials. The paper first discussed the effect of the amount of vulcanizing agent on the properties of PP/POE TPE. Based on the study of tensile strength, elongation at break, cross-section morphology, processability and aging properties of TPE, it was found that the TPE prepared with 0.6 phr of bis(1-(tert-butylperoxy)-1-methylethyl)-benzene (BIPB) and 40/60 of PP/POE had the best properties. Then silicone powder (GM) is added to the traditional low-halogen bromine-phosphorus flame retardant system for flame retardant modification. The results show that the addition of GM can effectively enhance the stability of the carbon layer, prevent the material from dripping during combustion, and increase the residual carbon content of TPE at 800°C. When 3 phr of GM is combined with a bromine-phosphorus system. The comprehensive performance is the best, the limiting oxygen index (LOI) of TPE increased to 29.8%, reaching the V-0 level. At the same time, the processing fluidity and aging resistance of TPE materials have also been improved.