Synthesis Of Silica Particles Research Articles

Synthesis of Silica Particles with Controlled Microstructure via the Choline Hydroxide Cocatalyzed Stöber Method.

This study investigates the utilization of choline hydroxide as a cocatalyst in the Stöber method to synthesize silica particles with controlled microstructure. Under low ammonia concentration, we add a robust organic base choline hydroxide and systematically explore the influence of choline hydroxide concentration on the hydrolysis and condensation equilibrium of tetraethyl orthosilicate (TEOS). Through the rational control of the water content, we significantly enhance both the size range and polydispersity of the resulting silica particles. Taking advantage of the regulated microstructure induced by controlled hydrolysis and condensation catalyzed by choline hydroxide, we achieved silica particles with hollow structures through hot water etching, exhibiting significantly enhanced surface area. These findings demonstrate the versatility of choline hydroxide as a cocatalyst in tailoring the microstructure of silica particles. In addition, due to its reducing ability and biocompatibility, which are not shared by other reported catalysts, the use of choline hydroxide opens up opportunities for applications in catalysis, sensing, and drug delivery.

In-situ two-dimensional temperature measurements using x-ray fluorescence spectroscopy in laminar flames with high silica particle concentrations

X-ray fluorescence spectroscopy (XRF) was used to measure temperatures and study mixing, for the first time in silica particle synthesis flames. Hexamethyldisiloxane (HMDSO) and trimethylsilanol (TMSO) were the particle precursors. A multi-element diffusion burner was used to produce a flat methane flame, and the precursors, dilute in inert gas, were injected via a central jet. Krypton was the fluorescent medium at 3.2 % concentration by volume. Scans with Kr in the central flow and not in the main flow were made to assess the mixing effects between the central and main gas flows. When HMDSO or TMSO were added, a secondary diffusion flame formed between the jet and the main methane flame. The results revealed a dramatic change in the centerline temperature profile of the jet gases when HMDSO or TMSO were added. The main methane flame stoichiometry also affected the temperature profiles. The results show HMDSO and TMSO reactions are initiated in a low-temperature and low-oxygen concentration region of the jet where thermal decomposition is not expected to be significant. Reaction of the particle precursors is therefore attributed to radical transport from the main methane flame. In the current work, particle number densities of up to 270 g/m3 locally are estimated. Thus, the study also demonstrates the capability of the XRF technique for high spatial fidelity measurements in flames with high concentrations of condensed-phase particles, leveraging the attribute that the XRF signal is generally not impacted by condensed-phase interferences. The observations and data obtained in this study inform likely reaction pathways for this important class of siloxane compounds.

Synthesis and characterization of monodispersed silica‐based shear thickening fluid for impact resistance applications

AbstractShear thickening fluid (STF), a highly concentrated mixture of nanosized silica particles in polyethylene glycol (PEG) is characterized by its quick transition to a stiff, solid‐like form under high shear rates. In this study, the modified Stöber synthesis approach was used for synthesizing the monodispersed spherical 300 nm silica nanoparticles. The rheological properties of the STF formulated using different silica loading were characterized. The Takshak model was tested to assess the rheological properties. The effect of the STFs on the impact resistance and yarn pull‐out force of the Kevlar® 802 fabric was determined. The uniformity in size of the silica nanoparticles facilitated more efficient packing within the fluid matrix, resulting in the formation of networks or structures that enhance shear thickening behavior. The STF with 70% silica exhibited the best peak viscosity of 45.8 Pa.s. Upon impregnation of this STF onto the Kevlar, a significantly high energy absorption (478.4%) compared to neat Kevlar, was observed. Moreover, the yarn pull‐out force for this system was found to be very high (435.8%). The reasons for the enhancement of the properties are explained. The novelty of this work lies in the synthesis of silica particles, analysis of the rheological properties, and interrelating the rheological properties with the characteristic parameters to define the impact characteristics. The improved properties underscore the suitability of synthesized STF for impact resistance applications.

From silica colloidal particles to photonic crystals: Progress in fabrication and application of structurally colored materials

Photonic crystals have attracted extensive attention because of their wide application in optics and photonics. These structures can be made by “top-down” or “bottom-up” self-assembly methods. Self-assembly methods have received particular attention due to their low cost, simple manufacturing process, relatively easy scaling, and ease of creating complex structures with nanometer precision. Self-assembled colloidal crystals play an essential role in the formation of photonic crystals. In this article, the assembly of colloidal crystals-silica particles, the synthesis of silica particles, and the assembly of three-dimensional photonic crystals based on inorganic/inorganic and inorganic/organic composites are introduced in detail. The formation of silica based bionic structure material can produce different optical properties of conventional materials. It provides unprecedented opportunities for textiles, pigments, sensing, information encryption, stealth materials, anti-counterfeit marks, energy collection, environmental remediation, and a variety of other application fields.

Подготовка тетраэтоксисилана для получения сферических частиц кремнезема. Часть 1. Ультрафильтрация

The paper considers the problem of instability of tetraethoxysilane hydrolysis in an ethanol medium in the presence of ammonia as a catalyst to obtain monodisperse spherical silica particles of a given size. This problem is associated with the presence of various impurities affecting rate of particle formation and, as a consequence, their size, monodispersity and shape. To solve this problem, we present novel studies of possible application of ultrafiltration for hydrolysis of initial tetraethoxysilane and ethanol through hydrophobic filters with a pore size of 50 nm. In both cases, we noted a decreasing intensity of light scattering after filtration. The elemental analysis of filtered impurities showed a significant content of SiO2 solid phases in tetraethoxysilane, and a number of impurities in ethanol. The experiments on the synthesis of silica particles from pre-filtered components showed that the resulting silica particles had a greater degree of monodispersity, and their sizes were much more reproducible, regardless of the used tetraethoxysilane. Thus, according to the obtained data, ultrafiltration is one of the effective ways to solve the problem of instability in the synthesis of monodisperse spherical silica particles.

Synthesis of silica particles through conventional sol-gel and sonochemistry methods and the effect of catalyst, water concentration and sample environment to the particle size

Various methods have been carried out in an effort to obtain SiO2 (Silica) particles with relatively the same grain size distribution and a uniform shape. This fine Silica particle size will be useful in the formation of SiC in the next stage. In this works, Silica particles has been synthesized through two different methods: conventional sol-gel and sonochemistry (using ultrasonic probe). Silica was synthesized by mixing TEOS, ethanol, ammonia, and D.I water with the molar ratio of 1 : 75.9 : x : y respectively. In sol-gel method, x was varied with 2.85, 5.7, and 8.54 M while y was fixed at 61.6 M. In sonochemistry method, y was varied with 6.69, 12.3, and 75.9M while x was fixed at 2.85 M Additional variation of sample environment including with and without ice has also been done in sonochemistry method. Amorphous phase was found in all samples from the XRD profiles. FT-IR results showed that the IR spectral peaks of all samples match the FT-IR spectrum of SiO2 with symmetric and asymmetric stretching mode of Si-O functional groups at 802 – 810 cm−1 and 1093 – 1103 cm−1 wavenumber. SEM images indicated that the average of SiO2 particle size tends to increase with the higher amount of ammonia concentration used and lesser concentration of water used results in smaller particle size. The influence of sample environment in sonochemistry method showed an interesting phenomenon where a lot of small particles sticked with bigger particles.

Bisphenol A Adsorption on Silica Particles Modified with Beta-Cyclodextrins.

This study presents the synthesis of silica particles bearing two beta-cyclodextrin (BCD) (beta-cyclodextrin-BCD-OH and diamino butane monosubstituted beta-cyclodextrin-BCD-NH2). The successful synthesis of the BCD-modified silica was confirmed by FT-IR and TGA. Using contact angle measurements, BET analysis and SEM characterization, a possible formation mechanism for the generation of silica particles bearing BCD derivatives on their surface was highlighted. The obtained modified silica displayed the capacity to remove bisphenol A (BPA) from wastewater due to the presence of the BCD moieties on the surface of the silica. The kinetic analysis showed that the adsorption reached equilibrium after 180 min for both materials with qe values of 107 mg BPA/g for SiO2-BCD-OH and 112 mg BPA/g for SiO2-BCD-NH2. The process followed Ho’s pseudo-second-order adsorption model sustaining the presence of adsorption sites with different activities. The fitting of the Freundlich isotherm model on the experimental results was also evaluated, confirming the BCD influence on the materials’ adsorption properties.

Bio-inspired formation of silica particles using the silica-forming peptides found by silica-binding motif sequence, RRSSGGRR

Silica particles are widely used as versatile materials with applications in catalyst support, biomedical materials, drug delivery systems, coatings, and cosmetics. Silica particle formation by biological catalysts could be more suitable for biotechnological applications. Although silicatein (protein) and R5 (peptide) are well-known as silica-forming biomolecular agents, new biocatalysts which can mediate silica particle synthesis under mild conditions are still needed. Here, we introduced three new silica-forming peptides (SFPs) found by BLASTp search using silica binding motif (RRSSGGRR) as a query. The three peptides were found to mediate biosilica formation under microbial culture conditions at pH 6−7. Among them, the peptide from Winogradskyella arenosi (Wa-RSG) exhibited better performance than other SFPs in the generation of silica particles at pH 6, at which silica is not easily formed. We investigated the optimal amount and reaction time of Wa-RSG for biosilica particle formation at pH 6−7. In addition, we demonstrated that Wa-RSG adsorbed on Escherichiacoli cell surfaces could induce silica shell coating of E. coli at pH 6–7, and the biosilica-coated microbes showed stability against harsh UV treatment. These results will be useful for the preparation of bio-integrated silica materials such as biomolecule-containing silica particles or silica-coated industrial microbes.

Synthesis and Characterization of Biosilica from Rice Husks as a Catalyst for the Production of Biodiesel

The synthesis of silica particles from rice husk is a research based on natural materials and is classified as green material. Preparation of biosilica catalyst from calcined rice husk ash was carried out by the hydrothermal method using rice husk ash mixed with NaOH solution at a ratio of 1:5 (w/v) with the reaction temperature of 110-120°C, the pressure of 0.15-0.2 MPa for 15-30 minutes. Biosilica results are then continued with the calcination process at a temperature of 200-500°C for one hour. Biosilica with calcination is then compared to biosilica without calcination. These two kinds of biosilica are then characterized to determine their performance. The biosilica characteristic test that was carried out included X-Ray Fluorescence (XRF), Scanning Electron Microscopy(SEM), and Brunauer-Emmett-Teller (BET). The XRF test results show that biosilica with calcination process has higher silica and silica oxide content than that without calcination. The surface morphology of biosilica with calcination and without calcination gives an uneven surface and consists of lumps and with uneven distribution on the surface of the biosilica sample. Biosilica with calcination process has a larger surface area, pore volume, and radius than biosilica without calcination process.

Synthesis of Silica Particles Using Ultrasonic Spray Pyrolysis Method

Silica has sparked strong interest in hydrometallurgy, catalysis, the cement industry, and paper coating. The synthesis of silica particles was performed at 900 °C using the ultrasonic spray pyrolysis (USP) method. Ideally, spherical particles are obtained in one horizontal reactor from an aerosol. The controlled synthesis of submicron particles of silica was reached by changing the concentration of precursor solution. The experimentally obtained particles were compared with theoretically calculated values of silica particles. The characterization was performed using a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). X-ray diffraction, frequently abbreviated as XRD, was used to analyze the structure of obtained materials. The obtained silica by ultrasonic spray pyrolysis had an amorphous structure. In comparison to other methods such as sol–gel, acidic treatment, thermal decomposition, stirred bead milling, and high-pressure carbonation, the advantage of the ultrasonic spray method for preparation of nanosized silica controlled morphology is the simplicity of setting up individual process segments and changing their configuration, one-step continuous synthesis, and the possibility of synthesizing nanoparticles from various precursors.

Gear-shaped micromixer for synthesis of silica particles utilizing inertio-elastic flow instability.

Mixing in microscale flows, where turbulence is inherently difficult to generate, has been a challenging issue owing to its laminar flow characteristics. Either the diffusion-based mixing process, or the convective mixing based on the cross-stream secondary flow, has been exploited as a passive mixing scheme that does not require any external force field. However, these techniques suffer from insufficient mixing or complicated channel design step. In this study, we propose an efficient mixing scheme by combining inertio-elastic flow instability in a viscoelastic dilute polymer solution and a modified serpentine channel, termed a gear-shape channel, which has side wells along the serpentine channel. We achieved highly efficient mixing in the gear-shaped channel for a significantly wider range of flow rates than in a conventional serpentine channel. Further, we applied our novel mixing scheme to the continuous synthesis of silica nanoparticles, which demonstrated the synthesis of nanoparticles with more uniform size distribution and regular shape, than those in a Newtonian fluid. In addition, the adsorption of inorganic materials on the channel walls was significantly suppressed by the flow instability of the viscoelastic dilute polymer solution in the gear-shaped channel.

Hollow Silica Particles: Recent Progress and Future Perspectives.

Hollow silica particles (or mesoporous hollow silica particles) are sought after for applications across several fields, including drug delivery, battery anodes, catalysis, thermal insulation, and functional coatings. Significant progress has been made in hollow silica particle synthesis and several new methods are being explored to use these particles in real-world applications. This review article presents a brief and critical discussion of synthesis strategies, characterization techniques, and current and possible future applications of these particles.

Numerical studies on SiO2 generation in swirling turbulent non‐premixed flames using SiCl4 as the precursor

AbstractSilica nanoparticles have been widely applied in many fields due to their excellent properties. SiO2 generation is crucial for silica particle formation, but in a swirling reactor the SiO2 generation is still unclear. In this study, numerical simulations are performed to investigate the SiO2 generation and distributions of temperature and velocity during silica particle synthesis using a swirling reactor. A computational model is first developed to describe the heat and mass transport in the swirling turbulent flame. Simulation models are validated with experimental data in the case without SiO2 chemistry. Then, effects of the fuel velocity and swirl number on SiO2 generation are investigated. Results show that most of the SiO2 molecules are generated in the region far away from reactor inlets and a relatively high SiO2 generation efficiency is obtained for a fuel velocity of 32.7 m/second. Distributions of the flame temperature, velocity and SiO2 concentration are found to vary with the swirl number and high chemical reaction rates for SiO2 generation are obtained when a swirl number of 0.5 is employed. Uncertainty analysis shows that the average relative errors of the results from different models are within 18%.

Polyacrylate/silica hybrid materials: A step towards multifunctional properties

Organic/Inorganic hybrid systems present a promising alternative for the creation of high-performance materials due to their biphasic structure that imparts multifunctional properties. The sol-gel process which initiated with the synthesis of inorganic glasses has now become a synthetic route for organic-inorganic assemblies due to several advantages such as mild processing conditions and the freedom to play with the structures of precursors. This versatility of the low-temperature sol-gel process provides an opportunity to engineer both the phases resulting in a synergistic combination or entirely new set of properties fruitful for different applications. This review highlights the several pathways for synthesis of silica particles, the interfacial modification and the classification of hybrid materials based on the method of incorporation of an inorganic moiety in the organic matrix along with the structure-property relationship, and the characterization to develop a fundamental understanding of the process. The nature of bonding between the two different species greatly affects the hybrid nanostructure and thus, the bulk properties of the system. In particular, acrylate/silica system has been focused due to its distinctive properties such as transparency, gloss, and strength that find large-scale application in the field of coatings, plastics and rubbers.Abbreviations: °: Degree; °C: Degree Celsius; 1H NMR: Proton nuclear magnetic resonance; A°: Angstrom; AHAS: N-(3-acryloxy-2-hydroxyl propyl)-3-amino-propyltriethoxysilane; AIBA: 2,2′-Azobis(2-methylpropionamidine) dihydrochloride; AIBN: 2,2′-Azobis(2-methylpropionitrile); Al: Aluminium; APDMES: Aminopropyldimethylethoxysilane; APTES: 3-Aminopropyltriethoxysilane; ATRP: Atom transfer radical polymerization; CERAMERS: Ceramically Modified Monomers; CTAB: Cetyltrimethylammonium bromide; DFMA: Dodecafluoroheptyl methacrylate; DMF: Dimethylformamide; DPSD: Diphenylsilanediol; FESEM: Field Emission Scanning Electron Microscope; FTIR: Fourier-transform infrared spectroscopy; GPTMS: 3-Glycidoxypropyltrimethoxysilane; HDTMS: Hexadecyltrimethoxysilane; HEMA: 2-Hydroxyethyl methacrylate; HLB: Hydrophilic-Lyophilic Balance; HMDS: Hexamethyldisilazane; HPC: Hydroxypropyl Cellulose; IPN: Interpenetrating Network; KPS: Potassium persulfate; LCST: Lower critical solution temperature; McPTMS: 3-Mercaptopropyltrimethoxysilane; MOI: 2-(methacryloyloxy)ethyl isocyanate; MPEGMA: Monomethoxy-capped poly(ethylene glycol) methacrylate; MPTMS: 3-methacryloxypropyltrimethoxysilane; MTC: 2-(methacryloyl) ethyltrimethylammonium chloride; MTES: Methyltriethoxysilane; MTMS: Methyltrimethoxysilane; NMP: Nitroxide-Mediated Polymerization; ORMOCERs: Organically Modified Ceramics; ORMOSILs: Organically Modified Silica; OTES: Octyltriethoxysilane; OTMS: Octadecyltrimethoxysilane; PAA: Poly(acrylic acid); PDMS: Polydimethylsiloxane; PEO-PPO-PEO: Poly (ethylene oxides)-b-poly (propylene oxides)-b-poly (ethylene oxides); PHPS: Perhydropolysilazane; PMMA: Poly(methyl methacrylate); POSS: Polyhedral Oligomeric Silsesquioxane; PTMO: Poly(tetramethylene oxide); PTMS: Phenyltrimethoxysilane; PTMS: Phenyltrimethoxysilane; PVP: Poly (vinylpyrrolidone); RAFT: Reversible addition- fragmentation chain transfer; Si: Silicon; Sn: Tin; Ta: Tantalum; TBN: 4-(triethoxysilyl)butyronitrile; TEM: Transmission Electron Microscopy; TEMED: N,N,N′,N′-tetramethylethylenediamine; TEOS: Tetraethoxysilane; Tg: Glass-Transition Temperature; THF: Tetrahydrofuran; Ti: Titanium; TMOS: Tetramethoxysilane; UV: Ultraviolet; VTES: Vinyltriethoxysilane; VTMS: Vinyltrimethoxysilane; Zr: ZirconiumHighlightsAdvantages of hybrid systems over the conventional materialsDiscusses the fundamental aspects of sol-gel chemistryFocusses on a detailed classification of hybrid polymersCovers different synthetic strategies, properties, and applications in diverse fields

Sol-Gel Synthesis of Amorphous Silica Nanoparticles: Study of the Process Parameters Influence on Structure and Particle Size Distribution

The synthesis of silica particles at the nanoscale through the sol-gel method is of great interest due to their potential use in industrial applications. The Stöber method is the most used method for the silica nanoparticles production using ammonia as a catalyst. This work studied the sol-gel synthesis of amorphous silica nanoparticles described by Stöber, in order to evaluate the influence of the variation of the process parameters (molar ratio water/TEOS = 25 and 55, reagent feed rate = 0.6 mL/min and 18 mL/min, pH = 12 and 9 and reaction time of 0, 5, 30, 60 and 120 minutes) on the particle size distribution and structural functional groups. The particle size distribution was analyzed by dynamic light scattering (DLS) and the structural functional groups was analyzed by infrared spectroscopy through Fourier transform (FTIR). The molar ratio water/TEOS influenced the functional groups presents and the time influenced the particle diameter distribution. It was not possible to identify the influence of the feed rate and pH in the results. The particle diameters found were between 200-500nm. This result may be occurred due to mass diffusion and/or nanoparticles aggregation.

Controlling morphology and particle size of hollow poly(styrene-divinylbenzene) microspheres fabricated by template-based method

Hollow poly(styrene–divinylbenzene) (P(S-DVB)) microspheres were fabricated via template-based method including synthesis of silica particles by sol-gel method, preparation of silica/P(S-DVB) particles by dispersion polymerization and chemical etching of silica cores by NaOH solution. TEM, FTIR and TG analyses confirmed that the hollow P(S-DVB) microspheres were successfully obtained. The morphology of hollow P(S-DVB) microspheres could be controlled by adjusting the amounts of DVB, AIBN and VTES, and the round-ball-like hollow P(S-DVB) microspheres were fabricated when the amount of DVB, AIBN and VTES was 30.0 wt%, 5.0 wt% and 30.0 vol% respectively. Both the size of silica particles and amount of monomers were regarded as the two key factors to control the particle size of the round-ball-like hollow P(S-DVB) microspheres.

Green Synthesis and Characterization of Biosilica Produced from Sugarcane Waste Ash

In this study, ash from sugarcane waste was used in the synthesis of biosilica using alkaline extraction followed by acid precipitation. Different parameters that could influence the silica particle synthesis were evaluated. The ash and synthesized biosilica were characterized by a combination of spectroscopic and chemical techniques such as XRD, XRF, SEM, particle size analyser, N2 adsorption analysis, TGA, and FTIR. The best condition for biosilica production was achieved with fusion method and aging temperature of 80°C for 1 h during gel formation. X-ray powder diffraction pattern confirms the amorphous nature of synthesized silica. The purity of the prepared silica was 99% silica which was confirmed by means of XRF. The experimental data suggest that the sugarcane waste ash could be converted into a value-added product, minimizing the environmental impact of disposal problems.

Colloidal Silica Particle Synthesis and Future Industrial Manufacturing Pathways: A Review

Colloidal silica is used in many applications including catalysis, pharmaceuticals, and coatings. Although naturally formed silica materials are widely available, they are often in forms that are difficult to process or are even harmful to health. Therefore, uniform colloidal silicas are generally manufactured using synthetic chemical processes. While established high temperature gaseous synthesis methods fall out of favor in our energy conscious society, liquid synthesis methods are current industrial leaders. The precipitated silica method provides the majority share of commercially produced specialty silicas with its economic advantages predicted to continue to grow in the future. The biomimetic method and microemulsion methods of synthesis provide a superior level of surface chemistry and morphological control than current industrial processes and are the major focus of current silica synthesis research. Movement toward more tailor-made products and ecologically friendly production methods will likely...

A comparative study of hydrophobic silica particle synthesis

The process to commercially synthesise silica particles with specific properties is a topic of ongoing research since their use in industrial applications including catalysis, coatings and separation materials has dramatically increased in the last decade. Here, silica particles were made using hydrolysed trimethoxymethylsilane (TMOMS) in the presence of either polyethyleneimine or aqueous sodium hydroxide catalysts. This work presents the first in depth study of the effect of TMOMS concentration on silica particles produced by both of these synthetic methods by comparing their size, morphology and chemical structure. The PEI-silica particles were larger in size and greater in yield than the NaOH-silica particles. It was also determined that both species of silica particles are hydrophobic without requiring further surface modification; and that those made with PEI have a higher contact angle, perhaps due to more complete polymerisation. The results demonstrate how relatively facile synthesis routes can wield a high degree of control over the physicochemical properties of silica particles, which is of paramount importance in silica production process intensification.

Synthesis of silica particles from rice straw waste using a simple extraction method

The purpose of this study was to synthesize silica particles from rice straw waste using a simple extraction method. The experiment was conducted by heating and extracting rice straw waste into basic solution. To get silica particles, the extracted solution was then put into acid solution and heated to remove the remained solvent. The experimental results showed that the aggregated silica particles with sizes of about 200 nm were successfully produced. The XRD and FTIR analysis showed that the final product was silica and free of graphite. However, we found that some KCl component in the final product in which this was possibly from the use of KOH as the extraction agent. Therefore, further studies are still required to synthesize high purity silica particles from rice straw waste.