SiO2 Particle Size Research Articles

Enhanced high-temperature thermal conductivity of the reduced graphene oxide@SiO2 composites synthesised by liquid phase deposition

Liquid phase deposition was developed to synthesise thermally conductive reduced graphene oxide@SiO2 (rGO@SiO2) composites for use in aerobic environments above 600 °C. This method is a mild, controllable reaction, good repeatability, easy operation, and low cost. The composition, morphology, oxidation resistance property, thermal conductivity (TC) property, and deposition dynamics of the rGO@SiO2 composites were systematically investigated in this study. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and high-resolution X-ray photoelectron spectroscopy (XPS) measurements proved that SiO2 particles were synthesised on the rGO. Spherical SiO2 particles were uniformly dispersed on both sides of the rGO, the SiO2 particle size was relatively uniform (∼500 nm), and there was no excessive aggregation. Isothermal oxidation and TC analyses showed that the rGO@SiO2 composite possessed better high-temperature and oxidation-resistance properties compared to pristine rGO, while still exhibiting excellent TC in the out-of-plane direction (k⊥) at 650 °C after 24 h. Moreover, the deposition dynamics of the rGO@SiO2 composite were established based on the analysis results. The synthesis method, liquid phase deposition, provides a promising route for the mild and controllable synthesis of rGO-ceramic composites for thermal management materials.

Biomimetic Growth of Hydroxyapatite on SiO2 Microspheres to Improve Its Biocompatibility and Gentamicin Loading Capacity.

The interest in multifunctional biomaterials to be implanted are also able to release drugs that reduce pain and inflammation or prevent a possible infection has increased. Bioactive materials such as silica (SiO2) containing surface silanol groups contribute to the nucleation and growth of hydroxyapatite (HAp) in a physiological environment. Regarding biocompatibility, the spherical shape of particles is the desirable one, since it does not cause mechanical damage to the cell membrane. In this work, the synthesis of SiO2 microspheres was performed by the modified Stöber method and they were used for the biomimetic growth of HAp on their surface. The effect of the type of surfactant (sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB), and polyethylene glycol (PEG)), and heat treatment on the morphology and size of SiO2 particles was investigated. Monodisperse, spherical-shaped SiO2 microparticles with an average particle size of 179 nm, were obtained when using PEG (SiO2-PEG). The biomimetic growth of HAp was performed on this sample to improve its biocompatibility and drug-loading capacity using gentamicin as a model drug. Biomimetic growth of HAp was confirmed by FTIR-ATR, SEM-EDX and TEM techniques. SiO2-PEG/HAp sample had a better biocompatibility in vitro and gentamicin loading capacity than SiO2-PEG sample.

Au-doped mesoporous SiO2 scattering layer enhances light harvesting in quasi Solid-State dye-sensitized solar cells

This study investigates the morphological effect of different Au-doped SiO2 scattering layers on the performance of dye-sensitized solar cells (DSSCs). Particularly, the SiO2 sources were varied to yield different geometries, i.e., tetraethyl orthosilicate (TEOS) templated SiO2, Sidoarjo mud (LuSi) extracted SiO2, and commercial silica glass sphere. The microstructure, as well as physical, electronic, and optical properties of different Au-doped SiO2 particles, were characterized using SEM-EDX, TEM, BET, XRD, and various spectroscopy techniques. The photoelectrochemical performance of quasi-solid state DSSCs was indicated by current density–voltage (J-V) response, external quantum efficiency spectra, and the impedance response. The results indicate that the performance of TiO2-based DSSCs is enhanced quite significantly due to the improved photocurrent generation and fill factor. The short circuit current density is found up to 370% higher (and hence, the conversion efficiency) than the reference cell upon incorporating Au-doped crystalline SiO2 extracted from LuSi (Voc = 0.89 V, Jsc = 1.28 mA‧cm−2, FF = 0.65, and η = 0.75%). This substantial photocurrent enhancement stems from the combined effect of efficient light scattering by submicron SiO2 particles, surface plasmon resonance, and reduced interfacial recombination by SiO2 insulation. In addition, the optimum size of SiO2 particles is deduced as the results indicate the size-scattering dependency which controls the gain and loss of photocurrent due to the type of scattering.

Electron paramagnetic resonance of sonicated powder suspensions in organic solvents

The chemical effects of the acoustic cavitation generated by ultrasound translates into the production of highly reactive radicals. Acoustic cavitation is widely explored in aqueous solutions but it remains poorly studied in organic liquids and in particular in liquid/solid media. However, several heterogeneous catalysis reactions take place in organic solvents.Thus, we sonicated trimethylene glycol and propylene glycol in the presence of silica particles (SiO2) of different sizes (5–15 nm, 0.2–0.3 µm, 12–26 µm) and amounts (0.5 wt% and 3 wt%) at an ultrasound frequency of 20 kHz to quantify the radicals generated. The spin trap 5,5-dimethyl-1-pyrrolin–N-oxide (DMPO) was used to trap the generated radicals for study by electron paramagnetic resonance (EPR) spectroscopy. We identified the trapped radical as the hydroxyalkyl radical adduct of DMPO, and we quantified it using stable radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a quantitation standard. The concentration of DMPO spin adducts in solutions containing silica size 12–26 µm was higher than the solution without particles. The presence of these particles increased the concentration of the acoustically generated radicals by a factor of 1.5 (29 µM for 0.5 wt% of SiO2 size 12–26 µm vs 19 µM for 0 wt%, after 60 min of sonication). Ultrasound produced fewest radicals in solutions with the smallest particles; the concentration of radical adducts was highest for SiO2 particle size 12–26 µm at 0.5 wt% loading, reaching 29 µM after 60 min sonication. Ultrasound power of 50.6 W produced more radicals than 24.7 W (23 µM and 18 µM, respectively, at 30 min sonication). Increased temperature during sonication generated more radical adducts in the medium (26 µM at 75 °C and 18 µM at 61 °C after 30 min sonication). Acoustic cavitation, in the presence of silica, increased the production of radical species in the studied organic medium.

Preparation and properties of UV-curable polyurethane acrylate / SiO2 composite hard coatings

To achieve the high dispersion of SiO2 nanoparticles in polyurethane acrylate resin, the titanate coupling agent, PN-102, was used as the surface modifier to prepare the modified SiO2 nanoparticles (Si-PN102-5) with small particle size and good dispersion ability in PUA-6 resin. Accordingly, hydrophilic SiO2 (Si-380) and hydrophobic SiO2 (Si-115) were introduced into PUA-6 resin to prepare the corresponding composite coatings, so as to investigate the effects of SiO2 nanoparticles modified with different surface modifiers on the properties of PUA / SiO2 composite coatings. The properties of PUA / SiO2 composite coatings were characterized by the tests of FT-IR, AFM, SEM, DMA, TG and so on. The FT-IR and XPS results show that PN-102 had functionalized the Si-PN102-5 particle surface successfully. The TEM test displays that the particle size of SiO2 was almost unchanged before and after modification, maintaining at about 20–30 nm. The SEM, DMA and tensile test reveal that Si-PN102-5 not only blocks the interaction and accumulation of nanoparticles, but also enhances the interface interaction with polymer chains through chain entanglement, which endows Si-PN102-5-5% composite coatings with highest mechanical strength among the other prepared coatings, reaching to 11.0 ± 0.1 MPa in tensile strength and 9.4 ± 3.0% in elongation at break. The pencil hardness of the prepared Si-PN102-5-5% composite coating could reach to 5H which is higher than the commercial PUA-6 based coating, and it also displayed good adhesion (4B) and flexibility (3 mm). The TG results show that all of prepared composite coatings display good thermal stability with a decomposition temperature of higher than 250 °C.

Tribological Properties of Complex Calcium Sulfonate Grease with Ultrafine SiO<sub>2</sub>/MoS<sub>2</sub> Powders

For the development of complex calcium sulfonate grease containing ultrafine SiO2/MoS2 powders with self-reparing performance. On the basis of the dispersion of the nanoSiO2 particles, the effects of particle size,addition amount,load and the mass ratio of nanoSiO2 to ultrafine MoS2 powders on the tribological properties of commercial No.2 complex calcium sulfonate grease were systematically studied by four ball friction and wear tester. The results show that suitable particle size and addition amount of single SiO2 and MoS2 powders can significantly reduce the coefficient of friction (COF) and the wear scar diameter (WSD) of the grease. The composite of nanoSiO2 and MoS2 powder can broaden the load range of base grease and further improve the tribological properties of complex calcium sulfonate grease. When the mass ratio of nanoSiO2 powder to MoS2 powder is 3:7 and the total addition amount is 0.8wt%, the COF and the WSD of the grease are decreased by 53.64% and 27.08%, respectively, compared with the base grease. The two powders in the composite grease have synergy effect for improving the tribological performance and the friction stability of the grease during the process of long friction.

Recent Advances in SiO2 Based Composite Electrodes for Supercapacitor Applications

Supercapacitors (SCs) have been widely exploited as a promising energy storage system due to their unique merits, including fast charge/discharge rates, long-term cycling stability and low maintenance cost. Therefore, researchers are focused on designing novel nanostructures with high surface area, optimum pore size and volume, and porous structure are highly desirable. Silicon dioxide (SiO2) has recently attracted enormous research attention as the electrode materials for SCs due to ease fabrication and integration possibility. However, due to the intrinsically poor electrical conductivity of metal oxides and the short diffusion distance of electrolytes into pseudocapacitor electrodes, only the surface of electroactive materials can effectively contribute to the total capacitance, while the large portion of material underneath the surface could hardly participate in the electrochemical charge storage process, leading to areal specific capacitance (ASC) values lower than expected. The coating of SiO2 has been recognized as a possible route to reduce the resistance and increase durability. Still, even for coated electrodes, the performance has always been several orders of magnitudes below that of carbon-based SCs. The morphology, structure, and particle size of SiO2 are related to the synthesis conditions and electrochemical performances. The thin films of SiO2 nanostructures deposited on conductive substrates and their composites both shows good performance (binder free electrodes). SiO2 and its composites display a large potential window for asymmetric SCs, delivering high energy density. More importantly, the design and development of composite materials with novel nanostructures are also effective ways to enhance the electrochemical properties of SCs. In this review, the research progress of SiO2 based composite electrodes for SCs are briefly reviewed. Consequently, the possible developmental direction, challenges, and opportunities for SiO2 based composite are also discussed.

Improvement of the fabricated and application of aluminosilicate-based microfiltration membrane

Aluminosilicate composite materials are characterized by their low cost, nontoxicity and facilely shaped. Membrane prepared using aluminosilicate composites have the following disadvantages: large mean pore size and low mechanical strength. To address these limitations, flat microfiltration membranes were fabricated using SiO2 powder and aluminosilicate composite as raw materials. The membrane performance was optimized by regulating the particle size of SiO2, the ratio of SiO2 to aluminosilicate composite (s/a), and the type of chemical admixture. The X-ray diffraction results indicated that the crystalline SiO2 particles were favorable for the preparation of membranes with higher bending strengths. The decreasing particle sizes of SiO2 (1.33–0.15 μm) decreased the pore size distribution. The bending strength of the membrane reduced with an increase in s/a, while was effectively enhanced by adding dissolved Na2SiO3. The optimized inorganic microfiltration membrane could also catalyze ozone to remove 100% of benzophenone-4 with an initial concentration of 10 mg L−1 within 15 min, and TOC removal by 52.67%. This paper presents a revised method for preparing an inorganic microfiltration membrane, which is an increasingly promising material for water treatment because of its low cost, low energy consumption, and high catalytic performance.

Adjustable color and emissivity based on amorphous arrays composed of SiO2@ZnO

SiO2@ZnO amorphous photonic crystals (APCs) were mainly manufactured by cladding and self-assembling. In this work, the SiO2 APCs framework are contributed to the desired structural color and the coated ZnO particles are served for reducing the infrared emissivity in 3–5 µm waveband. The effects of SiO2 particle size and ZnO adhesion amount on the visible light properties have been investigated as well as the infrared performance. The results show that with the diminution of SiO2 particles size, the packing quality of SiO2@ZnO is constantly improved since the smaller particle possesses higher electric density and surface energy. In the effects of nuclei size, SiO2@ZnO APCs with different size of building units display different color and low emissivity, and the sample with 250 nm core and 1:2 SiO2/ZnO mass ratio has blue structure and emissivity of 0.303. Meanwhile, the increasing ZnO adhesion amount can also alter the structural color due to the red shift of photonic pseudogap, and the minimum emissivity values keep dropping from 0.496 to 0.236. Finally, the SiO2@ZnO APCs with SiO2 core size of 250 nm and SiO2/ZnO mass ratio of 1:4 exhibit prominent performance with light green and low emissivity of 0.236 which contributes to the compatibility in green vegetation camouflage background and infrared stealth.

‘Synthesis and properties of amorphous nanosilica from rice husk and its composites

Amorphous nanosilica (SiO2) was prepared from rice husk by a cost-effective and environment-friendly method. Magnetic nanocomposite has been prepared by using injection molding equipment from amorphous nanosilica, ferrites, and PVDF. The XRD pattern analysis reveals the amorphous nature of the silica. The particle size of SiO2 was observed from the SEM and TEM analysis and found to be very small, which suggests the formation of amorphous nanosilica from the rice husk. FTIR spectra show the absorption peaks of SiOiSi (silanol) functional group. The photoluminescence spectrum reveals the broad excitation of radiation in the visible region. A characteristics peak in UV–Vis absorption spectra occurs at 365 nm, and the optical band gap was found to be 3.35 eV. Magnetic study shows the diamagnetic nature of amorphous nanosilica. The nanocomposite of amorphous nano silica-Ferrite-PVDF exhibits ferromagnetic nature due to the presence of ferrite in the nanocomposite. The magnetic hysteresis loop of nanocomposite reveals that the materials can be used as polymer magnet. The physical properties of amorphous nansilica and its composite with PVDF and ferrite have been explored in the present article. The present study may help to use prepared nanosilica materials in technological applications.

Investigation of thermo-mechanical properties of surface treated SiO2/epoxy nanocomposite

The present work investigates the effect of surface-treated SiO2 nanoparticles on the thermo-mechanical property of epoxy-composites. The surface interactions between the SiO2 nanoparticles and epoxy matrix were improved by surface treatment of SiO2 nanoparticle with different functionalization agents. Four functionalization agents namely 3-glycidyloxypropyltrimethoxy silane (GPTMS), 3-aminopropyltriethoxy silane (APTES), 3-(2-aminoethyl amino)-propyl trimethoxy silane (AEAPTMS), and 3-(trimethoxysilyl) propyl methacrylate (TMPM) were employed for the surface-treatment of SiO2 nanoparticles. No significant change in particle size of SiO2 was observed after surface-treatment, however significant improvement in mechanical properties was observed. It was observed that the percentage elongation and fracture toughness improved significantly with surface modification of the nanoparticles. Fracture toughness (K1C) and fracture energy (G1C) were calculated to be 5.62 MPa.m1/2 and 65.81 KJ/m2, respectively, for pristine silica-epoxy nanocomposite, whereas these values increase to 9.3 MPa.m1/2 and 124.27 kJ/m2 with the dispersion of GPTE treated 1 wt% SiO2 nanoparticles. The value of storage modulus was increased by 159.64% for GPMT modified SiO2 nanoparticles. Thus, surface-treated SiO2-epoxy nanocomposites exhibited improved thermo-mechanical properties.

Effect of Size and Content of SiO2 Nanoparticle on Corona Resistance of Silicon–Boron Composite Oxide/SiO2/Epoxy Composite

Corona discharge always threatens the safe and long-term operation of electrical equipment. Therefore, it is imperative to improve the corona resistance of electrical insulation materials. In this research work, fumed silica (SiO2) with different particle sizes and self-made organic silicon–boron composite oxide (Si–B) are used to modify epoxy resin (EP) for enhancing the corona resistance. Si–B/SiO2/EP nanocomposites with different SiO2 content series and 4 kinds of SiO2 particle size series are prepared by grinding machine dispersing and thermal curing. A strong dependence of the corona resistance on SiO2 filler size in nano-scale and content is revealed experimentally. The filler combination of Si–B and nano-SiO2 can reduce the relative permittivity of the Si–B/SiO2/EP nanocomposites and inhibit the increase of dielectric loss. With the particle size of SiO2 filler increases, the space charge suppression effect and the thermal stability are reduced, but corona resistance life is improved.When the 15-nm SiO2 content is 15 wt%, the corona resistance life of the Si–B/SiO2/EP nanocomposites can reach 8.99 h under 90 °C and 80 kV/mm electric field strength, while pure epoxy is only 0.86 h. The degradation path through the material is the more important factor affecting corona resistance performance–large particle size and well dispersion state can effectively extend the degradation path through the material.

Study on the effect of particle size and dispersion of SiO2 on tribological properties of nitrile rubber

BackgroundThe friction and wear of water-lubricated bearings has always been an engineering problem that we need to solve urgently. ObjectTo investigate the influence of SiO2 particle size and dispersion on the friction and wear properties of nitrile rubber. MethodThe friction and wear performance of rubber compounds (SiO2(nano)/NBR, SiO2 (micr)/NBR and SiO2 (TESP)/NBR) was tested by American Rtec multifunctional friction and wear test machine under the conditions of water lubrication and constant temperature. ResultsThe results showed that the particle size of SiO2 has a great impact on its dispersion in nitrile rubber, and the surface modification of SiO2 can significantly improve its dispersion. SiO2 (TESPT)/NBR showed a good friction coefficient under low-speed and high-load conditions. The wear of SiO2 (nano)/NBR and SiO2 (micr)/NBR, which was mainly the fatigue wear, was relatively serious. In contrast, the modified SiO2 had a smaller particle size, better dispersion and stronger interfacial bonding with the nitrile rubber matrix. This significantly reduced the wear of SiO2 (TESPT)/NBR, which was mainly the abrasive wear, and improved its wear resistance.

Effect of different particle size of silica on structure, morphology, and properties of thermoplastic cassava starch

Thermoplastic cassava starch (TPS)/silica (SiO2) composites were prepared through melt-mixing, and the effect of different SiO2 particle size (20 nm, 200 nm, and 23 µm) on the structure, morphology, and properties of TPS/SiO2 composites was investigated. TPS/SiO2 composite containing 200 nm SiO2 has the lowest plasticizing time and torque, and the highest tensile and impact strength. The 23 µm SiO2 particle has the strongest effect on promoting retrogradation of starch, while the 200 nm SiO2 particle could inhibit the retrogradation of starch. TPS/SiO2 composite containing 200 nm SiO2 has the highest thermal stability, resistant water absorption, and light transmittance. The 200 nm SiO2 particle could be uniformly and finely dispersed in the starch matrix, however 20 nm SiO2 particle easily aggregated in TPS. The spherulites size was uniform in TPS/SiO2 composite containing 200 nm SiO2. TPS/SiO2 composite indicates the mixture of A + V types of crystalline structure, and TPS/SiO2 composite containing 23 µm SiO2 had the largest crystal size.

Three-dimensional ordered macroporous magnetic photonic crystal microspheres for enrichment and detection of mycotoxins (I):Droplet-basedmicrofluidicself-assemblysynthesis.

Ordered porous materials are attracting enormous attention due to their uniform pore structures, particularly the magnetic photonic crystal microspheres (PCMs) which not only possess unique photonic crystal structure but also can achieve separation easily based on magnet. Here, a two-phase microfluidic self-assembly synthetic system was established simply and employed for the preparation of three dimensional PCMs (3DPCMs) by using the emulsion droplet approach. One phase (dispersed phase) was an aqueous emulsion containing Fe3O4, silica (SiO2) and polystyrene (PS) nanoparticles; another phase (continuous phase) was pure silicone oil. The droplets were formed by introducing the dispersed phase into the continuous phase through a tee valve. By heating the droplets, the water would evaporate and the nanoparticles would finally assemble into solid microspheres, which could be changed into macroporous 3DPCMs after removal of the PS nanoparticles by calcination. The contents and particle sizes of Fe3O4, SiO2 and PS nanoparticles in the dispersed phase were investigated in detail and optimized to prepare macroporous magnetic 3DPCMs with high quality. The morphologies, surface crystal structure, magnetic property, particle size distribution, specific surface area and pore size of the macroporous magnetic 3DPCMs were characterized. The expected 3DPCM displayed regular and uniform photonic crystal structure, narrow particle size distribution and strong magnetic property. The macroporous magnetic 3DPCMs grafted with vomitoxin (DON)-antibodies could be applied for selective enrichment of DON in real samples.

PVA/Pt/N-TiO2/SrTiO3 porous films with adjustable pore size for hydrogen production under simulated sunlight

In this study, poly(vinyl alcohol)/platinum/nitrogen-doped titanium dioxide/strontium titanate composite (PVA/Pt/NT/STO) porous films with adjustable pore sizes were successfully synthesized using the facile etching SiO2 method. This enhanced the light transmittance and contact rate between the photocatalyst and solution. The effects of the size and number of the pores on the hydrogen production rate were studied under simulated sunlight. The pore size of the PVA/Pt/NT/STO film increased with increasing particle size of the as-prepared SiO2, and the photocatalytic hydrogen production efficiency increased with increasing pore size and number. Due to the formation of pores on the film, the light transmittance and charge separation of the film increased. Owing to the good light transmittance and charge separation of the porous PVA/Pt/NT/STO film, the optimal photocatalytic hydrogen production rate of the PVA/Pt/NT/STO-8S-I-20 reached 34,895 μmol/h/g when the alcohol solvent, synthesis time, and SiO2 concentration were isopropanol, 20 h, and 8 wt%, respectively. Furthermore, the photocatalytic hydrogen production rate was approximately three times higher than that of the dense PVA/Pt/NT/STO film.

Process parameter effects on particle size reduction of sol-gel synthesized silica nanoparticles

Abstract In present study, SiO2 nanoparticle was prepared using sol-gel method. Tetraethyl orthosilicate (TEOS) was chosen as a silica precursor, ethanol as a solvent, water as co-solvent and ammonia as a catalyst. The effects of most influencing process parameters molar ratio (0.5, 1 and 2) of tetra-(ethyl)-orthosilicate (TEOS) to ammonia (NH3) with respect to particle size variation was investigated experimentally in detail. The size of SiO2 particles was controlled by tuning the NH3 concentration with respect to TEOS. Scanning electron microcopy (SEM) studies were performed for understanding the size of SiO2 nanoparticles while surface functional groups was determine by Fourier transform infrared (FTIR). The amorphous phase and purity of particles was identified by X-ray diffraction (X-RD) and energy dispersive spectroscopy (EDS) respectively. This work demonstrates the molar ratio variation had the noticeable effect on particle size reduction of SiO2 particles. it was found that the particle size decreases with increases of NH3 concentration with respect to TEOS (molar ratio = 1) and found lowest particle size of 40 nm (TEOS: NH3) with fixed amount of TEOS, ethanol, water and reaction time

Phosphoric acid induced homogeneous crosslinked phosphorus doped porous Si nanoparticles with superior lithium storage performance

The high volume expansion and low electrical conductivity issues severely limit practical application of Si-based materials for Li ion batteries (LIBs). Here we prepare the homogeneous crosslinked phosphorus (P) doped porous Si nanoparticles (P doped pSi) via magnesiothermic reduction of P contained nanosize SiO2 (P-SiO2). Phosphoric acid (H3PO4) acts as a bifunctional additive to reduce particle size of SiO2 and achieve P doping of porous Si. The employment of this modified nanosize SiO2 as precursor effectively alleviates the agglomeration of Si grains. Besides, the P doping characteristic is quite effective to promote the charge transfer performance of Si anode. Finally, P doped pSi anode displays superior cycle capacity and rate capability in half cells with 1761 mAh g−1 at 0.5 A g−1 after 80 cycles and 700 mAh g−1 at 5 A g−1 even after 400 cycles. Furthermore, the electrochemical performance of P doped pSi//LiFePO4 full cell is also evaluated. All the results indicate that P doped pSi is an excellent competitor to replace traditional graphite anode for LIBs.

Investigation on mechanical, thermal, and flame retardant properties of particulate SiO2 reinforced cardanol based composites

AbstractCardanol based epoxy thermosets and particulate SiO2 incorporated composite systems were developed by blending various ratios of commercial diglycidyl ethers of bisphenol‐A (DGEBA) with epoxidized cardanol (EPC) using melt mixing method followed by sonication. Physico chemical properties of the prepared resins were studied. Various percentage of SiO2 was incorporated in to the resin system [15% EPC + 85% DGEBA] (BEPC1)] to improve their thermo mechanical properties. The effect of loading content on the curing behavior, mechanical, and thermal properties were investigated by FT‐IR, mechanical tests, differential scanning calorimetry, and thermogravimetric analysis (TGA). Particle size and dispersion probability of SiO2 in the composites were studied by field emission scanning electron microscope. These studies showed that 1% SiO2 reinforced BEPC1 matrix system were effective in enhancing mechanical strength and thermal stability of composites. The prominent char residue value obtained in the TGA analysis predicted the good flame retardant property of the developed composite. This was evidenced in UL‐94 test and limited oxygen index (LOI) determination.

Nanoporous silicon spheres preparation via a controllable magnesiothermic reduction as anode for Li-ion batteries

Magnesiothermic reduction is a facile and utility method for scalable synthesis of porous silicon. However, the severe heat accumulation during this process can lead to the porous structure collapse. In this work, we present an applied method for achieving a controllable magnesiothermic reduction through regulating the reaction rate by merely adjusting the particle size of magnesium. The impact effect of magnesium size on the reaction process is also systematically studied. It is found that the heat accumulation can be relieved when the size of magnesium is > 800 μm (l-Mg). The obtained reduced silicon (l-rSi) can basically maintain the spherical shape and particle size of raw SiO2 and form a highly-developed nano-porous structure. It exhibits a high initial discharge capacity of 3191 m Ah g−1 and coulombic efficiency of 80.9% with superior cycling stability and rate capability. Moreover, when the obtained l-rSi is added in commercial graphite with only 10 wt%, the capacity of l-rSi/commercial graphite composite increases to 670 m Ah g−1, which is about 2 times that of commercial graphite, manifesting great potential for industrial application. Our work can be a guide to fabricate nanostructure silicon materials through magnesiothermic reductions for the silicon-based anode of lithium-ion batteries.