SiO2 Nanopowder Research Articles

Kinetics of formation, microstructure, and properties of monolithic forsterite (Mg2SiO4) produced through solid-state reaction of nano-powders of MgO and SiO2

The synthesis of forsterite can be challenging because the initial oxides react slowly and undesirable compounds like enstatite (MgSiO3) can form instead of forsterite (Mg2SiO4). Although several methods have been developed to overcome these challenges, the synthesis of forsterite using the solid-state reaction of nanopowders has not been investigated. This study aims to explore the possibility of producing forsterite by reacting MgO and SiO2 nano-powder. The initial oxides were wet ball milled, dried, and reaction sintered. Spectroscopy and microscopy methods were used to analyze the formed phases and study the formation kinetics. The density, coefficient of thermal expansion (CTE), and hardness of sintered samples were measured using a densimeter, a dilatometer, and a hardness tester, respectively. The results demonstrated that it is possible to synthesize forsterite by solid state reaction of pure MgO and SiO2 nano-powders. The reaction between the two compounds begins at a temperature as low as 860 °C and leads to the formation of forsterite by a two-step formation mechanism. The first reaction involves the reaction of MgO and SiO2 to form enstatite, and the second one produces forsterite as a result of enstatite reacting further with MgO. The activation energy values ranged from 1028.89 to 1105.655 kJ/mol for the formation of forsterite, and from 456.316 to 488.08 kJ/mol for the formation of enstatite. Monolithic forsterite was completely formed at a low temperature of 1200 °C for a relatively short duration of 2 h. The sample sintered at 1400 °C for 2 h, had a density of 2.96 g/cm3, a Vickers hardness of 7.64 GPa, and a coefficient of thermal expansion of 10.24 × 10−6/K measured in the temperature range of 200–1300 °C.

Radiation resistance of polypropylene modified with nanoparticles of oxide compounds

The results of studies of optical properties in UV, visible and IR spectral regions, and radiation resistance of nanocomposites based on polypropylene modified with nanoparticles of oxide compounds (ZrO2, Al2O3, SiO2, MgO, TiO2, ZnO) are presented. Diffuse reflectance spectra were recorded under 2 ∙ 10−6 torr vacuum before and after electron irradiation (in situ, Е = 30 keV, F = 2 ∙ 1016 cm−2). According to research findings, modification of polypropylene with nanoparticles leads to an increase in radiation resistance, which depends on the structure of the nanopowders, their size and specific surface area. The SiO2 nanopowder, characterized by its amorphous nature, the largest specific surface area, and the smallest particle size, stands as the most effective modifier for enhancing radiation resistance. The IR-Fourier spectra of electron-irradiated samples are similar to the original spectra. A slight decrease in transmission across all characteristic bands compared to the non-irradiated samples indicates minor structural changes as a result of irradiation.

The effect of SiO2 nano-powders on energy storage properties of the PLZST antiferroelectric ceramics

(1-x)(Pb0.97La0.02)(Zr0.46Sn0.48Ti0.06)O3-xSiO2 ((1-x)PLZST-xSiO2, x = 0-0.025) thick film antiferroelectric ceramics were preapred by a traditional solid-state reaction method. The structure and dielectric properties related to the energy storage density in the (1-x)PLZST-xSiO2 system were investigated in detail. PLZST with 0.5%SiO2 content is superior to other SiO2 contents samples in terms of the structure, dielectric properties and phase transition modulation. The energy storage density reaches the maximum value of 1.66 J/cm3 accompanied by the energy efficiency of 86.92% in 0.995 PLZST-0.005SiO2. The results suggest that high energy storage density of PLZST system can be improved with phase transition modulation using SiO2.

Solidification and Super-cooling Behaviors of Silica Nanofluids based on the Molten Eutectic Nitrate Salt

SiO2 nano-powders with different particle sizes were used to fabricate nitrate-based nanofluids with the nano-particle concentration arranged from 0.5-4.0 wt.%. The crystallization process of the as-prepared composite and the influence of nanoparticles on the cooling kinetics was analyzed based on experimental data. The research results show that Johnson-Mehl-Avrami equation can be only used to describe the crystallization process of pure eutectic salt, but not suit for nanofluids since the nanoparticles addition can alter the crystallization kinetics of the composites. Depending on the particle size and concentration, nanoparticles addition was found to be able to improve the degree of supercooling and reduce the crystallization completion time by varying degrees. Further verification by a modified JMAK equation shows that with the nanoparticle addition, the component ‘n’ would fluctuate within a certain range, which indicates that the nanoparticles can improve the crystallization process by altering the nucleation mechanism and adjusting the cooling rate resulted from the increased thermal conductivities of the nano-fluids.

Preparation of Li2Si2O5 fibers and their toughening effects on lithium disilicate glass-ceramics

To address the challenge of poor fracture toughness of lithium disilicate glass-ceramics, which hinders their application as posterior single crowns and three-unit fixed bridges, the concept of fiber toughening was employed. In this study, Li2Si2O5 fibers were successfully prepared through an electrospinning technology combined with sol-gel followed by a heat treatment. The fibers could be further densified by adding SiO2 nano-powder to partially replace TEOS as a silicon source and the possible mechanism was put forward. By using the fibers as the reinforcement phase, the uniform fiber-toughened Li2Si2O5 glass-ceramic composites were successfully produced by hot pressing sintering. These composites exhibited significant enhancements in mechanical properties, including a flexural strength of 315 ± 10 MPa, fracture toughness of 4.57 ± 0.35 MPa m1/2, and Vickers hardness of 5.61 ± 0.28 GPa, respectively. Notably, the highest fracture toughness of the composite increased by 41 % compared to the samples without fiber reinforcement, which was attributed to the toughening mechanisms including crack deflection, fiber bridging, and fiber pull-out. The results demonstrated the advantages of Li2Si2O5 fibers in toughening glass-ceramic materials, thereby expanding the application areas of this material.

Synthesis and characterization of single-phase X2-Lu2SiO5 nanostructured feedstocks for advanced plasma-sprayed environmental barrier coatings

The objective of this work is to synthesize the single-phase X2-Lu2SiO5 nanostructured feedstocks for plasma-sprayed environmental barrier coatings (EBCs). Generally speaking, high-performance feedstocks are a prerequisite for obtaining high-performance coatings. The single-phase X2-Lu2SiO5 nanostructured feedstocks were fabricated by a nanopowder reconstitution method for the first time. The morphology and phase structure of X2-Lu2SiO5 nanostructured feedstocks were examined. The physical properties of X2-Lu2SiO5 feedstocks were evaluated. In addition, the thermal conductivity of nanostructured X2-Lu2SiO5 coatings was measured. Results show that the single-phase X2-Lu2SiO5 nanostructured feedstocks are successfully synthesized when the mole ratio of Lu2O3 and SiO2 nanopowder is 1:1.1 and the agglomerated powders are sintered at 1300 °C for 2 h. The nanocrystalline size of the X2-Lu2SiO5 feedstocks ranges from 40 to 70 nm. Moreover, the d10, d50 and d90 of X2-Lu2SiO5 feedstocks are 24.69 μm, 37.78 μm and 54.75 μm, respectively. The apparent density and tap density of X2-Lu2SiO5 feedstocks are 1.76 g/cm3 and 2.09 g/cm3, respectively. The thermal conductivity of as-deposited Lu2SiO5 coating is 0.78–1.20 W m−1 K−1 (30–1200 °C). Overall, the single-phase X2-Lu2SiO5 nanostructured feedstocks are the most promising feedstocks for advanced EBCs system in the future.

Photodegradation of Rhodamine B and Phenol Using TiO2/SiO2 Composite Nanoparticles: A Comparative Study

Organic pollutants found in industrial effluents contribute to significant environmental risks. Degradation of these pollutants, particularly through photocatalysis, is a promising strategy ensuring water purification and supporting wastewater treatment. Thus, photodegradation of rhodamine B and phenol under visible-light irradiation using TiO2/SiO2 composite nanoparticles was within the main scopes of this study. The nanocomposite was synthesized through a wet impregnation method using TiO2 and SiO2 nanopowders previously prepared via a facile sol–gel approach and was fully characterized. The obtained results indicated a pure anatase phase, coupled with increased crystallinity (85.22%) and a relative smaller crystallite size (1.82 nm) in relation to pure TiO2 and SiO2 and an enhanced specific surface area (50 m2/g) and a reduced energy band gap (3.18 eV). Photodegradation of rhodamine B upon visible-light irradiation was studied, showing that the TiO2/SiO2 composite reached total (100%) degradation within 210 min compared to pure TiO2 and SiO2 analogues, which achieved a ≈45% and ≈43% degradation rate, respectively. Similarly, the composite catalyst presented enhanced photocatalytic performance under the same irradiation conditions towards the degradation of phenol, leading to 43.19% degradation within 210 min and verifying the composite catalyst’s selectivity towards degradation of rhodamine B dye as well as its enhanced photocatalytic efficiency towards both organic compounds compared to pure TiO2 and SiO2. Additionally, based on the acquired experimental results, ●O2−, h+ and e− were found to be the major reactive oxygen species involved in rhodamine B’s photocatalytic degradation, while ●OH radicals were pivotal in the photodegradation of phenol under visible irradiation. Finally, after the TiO2/SiO2 composite catalyst was reused five times, it indicated negligible photodegradation efficiency decrease towards both organic compounds.

Preparation of Photoresponsive Nanosilica Powder

In order to obtain photoresponsive silicon dioxide nanopowders, fluoropolymer/SiO2 composite microspheres were prepared with a thiol-terminated fluoropolymer and with SiO2 microspheres grafted by acrylate via the thiol-ene click reaction; then, photoresponsive SiO2 nanopowders were synthesized by grafting azobenzene monomers on the surface of the SiO2 composite microspheres by esterification. The fluoropolymer and SiO2 composite microspheres were characterized via proton nuclear magnetic resonance, scanning electron microscopy, contact angle tests, dynamic light scattering, and UV-Vis absorption spectroscopy. The surface of the coating prepared using SiO2 nanopowders exhibited a high contact angle up to 130.9°. When the surface was irradiated with UV light, the contact angle decreased to 104.1°. Reversible changes in the surface wettability could be realized under the alternate irradiation of ultraviolet and visible light, thus achieving excellent photoresponsiveness.

The development of sulfonated polyether ether ketone (sPEEK) and titanium silicon oxide (TiSiO4) composite membranes for DMFC applications

This work aims to develop composite membranes based sPEEK polymer matrix with TiSiO4 for direct methanol fuel cell (DMFC) applications. The sPEEK having 53% of degree of sulfonation (DS) was preferred to avoid dissolution and high-swelling problems of the polymer matrix at the operating conditions. The various content of TiSiO4, prepared by the calcination reaction of TiO2 and SiO2 nano-powders, was placed into the sPEEK matrix using the solution-casting method. The thermal and physicochemical properties of the composite membranes were characterized. AC impedance spectroscopy and methanol diffusivity measurements were conducted to determine the fuel cell characteristics of the membranes. The composite sPEEK membrane with 2.5 wt% TiSiO4 performed the highest single-cell DMFC test performance compared with sPEEK and Nafion™ 117 membranes. It can be concluded that the composite sPEEK membranes with TiSiO4 can be promising and low-cost alternative membranes for DMFC applications.

An indigenous tool for the adsorption of rare earth metal ions from the spent magnet e-waste: An eco-friendly chitosan biopolymer nanocomposite hydrogel

Recently, polymer nanocomposite hydrogel (PNC-hydrogel) has attracted the focus and attention of young and dynamic researchers in water remediation and purification due to its cost effectiveness, high processability, modified surface area, and enhanced absorptivity for the elimination of toxic ions of heavy metals and for its tunable properties as well as reusability. Chitosan (Cs), a deacetylated product of chitin, is the most promising and prospective biopolymer for adsorbing toxic heavy metallic ions from wastewater in diluted form. But when it is functionalized with any of its copolymers, its effectiveness and usability capacity are enhanced bythousand times in comparison to the virgin biopolymer, as it is less soluble in acidic aqueous medium. The functionalization of the biopolymer is proficient enough to bind the rare earth ions from the wastewater solution, and it is done by grafting the biopolymer with a variety of co-polymers. Herein, SiO2 nanopowder along with chitosan biopolymer based bionanocomposite hydrogel (SCB-hydrogel) has been prepared. This grafted biopolymer-based SCB-hydrogel was investigated by various techniques such as FTIR, XRD, FESEM, TEM, and UV-spectroscopy. The impact of numerous parameters including pH, adsorbate doses, time of contact, concentration of metallic ions, kinetic parameters with proper isotherms, desorptivity, and reusability of the PNC was studied in batch adsorption mode. The adsorption efficiency by the SCB-hydrogel with increasing concentration of lanthanide ions was observed to be 99 % from the waste diluted water followed by the Langmuir adsorption model along with kinetics of pseudo second order. Desorption of the lanthanides was also carried out by using 1 M H2SO4 and HCl solution. The adsorption efficiency of these PNC didn’t alter much as with the original in reusability of maximum three times. Keeping in view of cost effectiveness and adsorption efficiency of the SCB-hydrogel we have used it in a maximum of three times availing its uses as well as reusability for a maximum limit of adsorption of the REEs onto its surface.Thus, in conclusion, the PNC can be effectively used as a novel bio-adsorbent for treatment of wastewater containing pollutants along with transition rare earth metal ions (Nd+3, Pr+3).

Effect of multiphase Nb2O5 on morphology and luminescence outcomes of Er3+-doped SiO2 nanopowder

Effect of multiphase Nb2O5 on morphology and luminescence outcomes of Er3+-doped SiO2 nanopowder

Enhanced Thermo-Fluidic Performance of Aqueous SiO2 Nanofluid Flow Through a Horizontal Tube—An Experimental Investigation

The thermo-fluidic performance of SiO2-water nanofluid (NF) flow inside a horizontal tube of circular cross section were examined applying constant heat flux. An aqua based dispersion of SiO2 nanopowders with 16.58 nm average particle diameter were used as the working fluid with 0.15–0.35 vol.%. Experiments are conducted in the Reynolds number (Re) range of 2798.96–27989.62 maintaining the bulk temperature of the flow at 45 °C. Thermo-physical properties namely conductivity (k) and viscosity (μ) of NF were determined at various temperatures range of 25–65 °C. Maximum 13% enhancement in k and a maximum of 20% enhancement in μ were obtained at 0.35 vol.% as compared to basefluid. Heat transfer and friction factor (f) were increased with enhancing concentration and Re. The Nusselt number (Nu) increased upto 40% along with a maximum increase of 28.57% in f as compared to their basefluid. New empirical correlations for Nu and f of nanofluids were developed. Finally, a figure of merit (FOM) was determined, which reveals the potency of nanofluids as working fluid for rapid cooling applications.

Three-Dimensional Smooth Particle Hydrodynamics Modeling and Experimental Analysis of the Ballistic Performance of Steel-Based FML Targets.

In this paper, shields made of 1.3964 stainless steel bonded to a fiber laminate were subjected to ballistic impact response of 7.62 × 51 mm ŁPS (light projectile with a lead core) projectiles. Additionally, between the steel sheet metal and the laminate, a liquid-filled bag was placed, which was a mixture of ethylene glycol (C2H6O2) with 5 wt.% SiO2 nanopowder. Numerical modeling of the projectile penetrating the samples was carried out using the finite element method in the Abaqus program. The elasto-plastic behavior of the projectile material and the component layers of the shields was taken into account. Projectile penetration through glycol-filled bag has been performed using the smooth particle hydrodynamics technique. The morphology of the penetration channel was also analyzed using a scanning electron microscope. For the shield variant with a glycol-filled bag between the steel and laminate plates, the inlet speed of projectile was 834 m/s on average, and 366 m/s behind the sample. For the variant where there was no glycol-filled bag between the steel and laminate plates, the inlet and outlet average velocities were 836 m/s, after 481 m/s, respectively. Referring to the steel-glycol-laminate and steel-laminate variants, it can be concluded that the laminate-glycol-laminate is more effective.

Testing the Physical and Mechanical Properties of Polyacrylonitrile Nanofibers Reinforced with Succinite and Silicon Dioxide Nanoparticles

In this research, we focused on testing the physical and mechanical properties of the developed polyacrylonitrile (PAN) composite nanofibers with succinite (Baltic amber) and SiO2 particles using standard methods of nanofiber testing (physical and mechanical properties). Polyacrylonitrile composite nanofibers (based on the electrospinning method) were coated on an aluminum substrate for structural investigation. SEM was used to determine the average fiber diameter and standard deviation. The mechanical properties of the fibers were determined using a universal testing machine (NANO, MTS). We observed that constant or decreased levels of crystallinity in the ultrafine composite nanofibers led to the preservation of high levels of strain at failure and that the strength of nanofibers increased substantially as their diameter reduced. Improvements in PAN composite nanofibers with succinite and SiO2 nanopowder are feasible with continuous decreases in diameter. The drastically decreased strain at failure demonstrated a substantial reduction in viscosity (toughness) of the annealed nanofibers. Large stresses at failure in the as-spun nanofibers were a result of their low crystallinity. As a result, decreasing the diameter of PAN nanofibers from approximately 2 micrometers to 139 nanometers (the smallest nanofiber tested) resulted in instantaneous increases in the elastic modulus from 1 to 26 GPa, true strength from 100 to 1750 MPa, and toughness from 20 to 604 MPa.

Fabrication of Fe-Si-B Based Amorphous Powder Cores by Spark Plasma Sintered and Their Magnetic Properties

Mechanical ball milling was used to coat SiO2 nanopowder on a Fe-Si-B amorphous powder in this study. The Fe-Si-B/SiO2 core–shell amorphous composite powder was obtained after 6h of ball milling. At 490 °C, the amorphous powder is thermally stable. Discharge plasma sintering was used to create a Fe-Si-B/SiO2 magnetic powder core (SPS). At a sintering temperature of 420 to 540 °C, the phase composition and magnetic characteristics of the magnetic particle core were investigated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to examine the structural features of the magnetic particle core. A precision resistance tester and a vibrating sample magnetometer were used to assess the resistivity and magnetic characteristics of the magnetic particle core. The findings showed that Fe3Si and Fe2B are the phases generated during spark plasma sintering. High-frequency power loss increases as density rises. However, at the measured frequency, the magnetic permeability of the magnetic particle core changes slightly and has excellent frequency characteristics, making it appropriate for use in high-frequency components.

Impact of Annealing on Structure, Morphology, Bandgap, Optical and Dielectric Behavior of Er3+ Doped SiO2 Nanopowder Useful for Photonic Devices

Impact of Annealing on Structure, Morphology, Bandgap, Optical and Dielectric Behavior of Er3+ Doped SiO2 Nanopowder Useful for Photonic Devices

Nano-materials enhanced protectants for natural stone surfaces

Most heritage buildings and monuments are constructed out of natural stones which suffer irrevocable degradation when undergoing wet weathering, bowing, and dissolution in outdoor conditions. Self-cleaning treatments are effective for stone protecting. Herein, nano-materials which provide enhanced protectants for Marble, Qingshi and Hedishi were prepared. Inherent microscale interstices and holes exist on polished natural stone surfaces. When treated by a commercial protectant, 101S, the surfaces were hydrophobic but not self-cleaning. Colloidal protectants were prepared by dispersion of Al2O3 and SiO2 nano-powder in 101S, respectively. Self-cleaning stone surfaces were achieved after treated by the protectants, meanwhile, the interstices and holes were reserved as much as possible. The principle of the as- prepared protectants is penetrating and crosslinking on the stone surfaces as well as the inner surfaces of the interstices and holes. The reserving of the micro interstices and holes is important since the breathability of the stones is remained. The self-cleaning surfaces showed good thermal stability below 250 °C. Meanwhile, changes of color and gloss of the treated stone surfaces are in the acceptable range.

Enhancement of Condensation Heat Transfer, Anti-Frosting and Water Harvesting by Hybrid Wettability Coating

Hydrophilic–hydrophobic hybrid wettability structures, inspired by desert beetles, have been widely designed to enhance the dewdrops’ migration under subcooled or/and high-humidity environment. However, it is still a challenge to regulate the graded distribution of the hydrophilic micro-regions for condensation applications. In this paper, we design a simple spray method to prepare the superamphiphilic–superamphiphobic hybrid wettability coatings by controlling the mass ratio (MR) of superamphiphobic SiO2 nano-powder and superamphiphilic gypsum micro-powder. We compare the macroscopical wettability, condensation heat transfer efficiency, frosting delayed time and water harvesting rate to demonstrate the unique advantage of hybrid wettability structures. The results show that the condensation heat transfer efficiency, frosting delayed time and water harvesting rate can be respectively promoted to about 131.50% [Formula: see text], 134.74% [Formula: see text] and 135.62% [Formula: see text], although their macroscopical wettability will gradually reduce with the MR increase. This work will provide substantial insights into the fabrication of efficient superhydrophilic–superhydrophobic hybrid wettability surfaces for condensation heat transfer, anti-frosting and water harvesting applications.

SiO2 nanoparticles effect to the Mahua oil for friction and wear characterization

In this research work, SiO2 nanoparticles were added to the Mahua oil and tribological analysis was done. The SiO2 nanopowder were added to the Mahua oil in different concentrations i.e. 0.3%, 0.9% and 1.5%. The addition of the nanoparticles oil lubricant was done using magnetic stirrer and proper mixing was attained. The reduction in friction was attained at 0.3% and it increases during the addition of 0.9% and 1.5%. The wear of the pin was obtained and maximum wear was obtained at higher concentration of nanoparticles. The Wear scar diameter was also gets minimized at 0.3% addition and after this concentration it was observed more.

Effect of hydrothermal nanosilica on the performances of cement concrete

A new technological method for producing a nano-modifier for cement concretes from renewable source of hydrothermal solution using the processes of polycondensation of orthosilicic acid and ultrafiltration membrane concentration is proposed. According to the data of dynamic light scattering, tunneling electron microscopy, and low-temperature nitrogen adsorption, it is shown that in sol samples the average diameters of amorphous SiO2 nanoparticles can be varied in the range 10–100 nm, the specific surface area of ​​SBET is 50–500 m2 / g, the density of chemically active surface silanol Si-OH groups up to σ = 4.9 nm−2. Increasing the compressive strength of concrete specimens modified with SiO2 sol (0.5–3.0 wt%) and polycarboxylate superplasticizer (0.2–3.98 wt%), liquid-binder ratio L/B = 0.5–0.7, with normal hardening and with accelerated hardening with heat-moisture treatment, it reached 128% at the age of 1 day, and up to 40% at the age of 28 days. According to the kinetic curves of water absorption, a significant decrease in the volume, average pore diameter and an increase in the uniformity of the distribution of pores along the diameter of the modified concrete were established, which led to an increase in its water impermeability. The kinetics of the pozzolanic reaction with the formation of crystalline calcium hydrosilicates has been studied by the methods of X-ray diffraction analysis, energy-dispersive spectroscopy, scanning electron microscopy, and thermogravimetry. The chemo-sorption capacity of hydrothermal SiO2 nanoparticles for binding Ca(OH)2 in CaO solution and cement matrice was determined, which, due to the high SBET and σ values ​​for the first 24 h of the reaction, is many times higher than that of silica fume. In modified Portland cement matrice at the age of 1 day, the δCaO value was 750 [mg CaO / g SiO2], which corresponded to a response of 60–70% of the introduced nano-SiO2 and an increase in the rate of alite hydration by 20–30%, and rised at the age 100 days to 1200 [mg CaO / g SiO2]. Hydrothermal sols and SiO2 nanopowders have prospects for the creation of cement composites.