Silica Powder Research Articles

Removal Efficiency of Cd (II) from Water using Silica Powder as Adsorbent

Removal Efficiency of Cd (II) from Water using Silica Powder as Adsorbent

A green and multi-win strategy for coal fly ash disposal by CO2 fixation and mesoporous silica synthesis

Coal combustion provides plenty of energy, along with enormous coal fly ash (CFA) and CO2 emission. CFA could be recycled for mesoporous silica synthesis, but expensive templates are usually needed. In this work, we proposed a multi-win strategy using CO2 as the precipitator and template. Mesoporous silica powders, with a maximum specific surface area of 355.45 m2/g, a pore volume of 0.73 cm3/g, and an average pore size of around 7.67 nm, were synthesized. The influences of silicon concentration, CO2 flow rate, and ultrasound were investigated. In addition, the Na2CO3 by-product was produced with a purity of over 92 %. By averagely calculating, 1 ton CFA could generate 285 kg mesoporous silica and 1.02 t crude Na2CO3. Around 433 kg of CO2 could be absorbed. Therefore, multi-goals of CFA disposal, CO2 storage, and valuable silica materials production were realized, and the study could pave the way for large-scale industrial applications.

Analysis of the slurry and ceramic properties for investment casting obtained with domestic colloidal silica binders

The quality of cast parts produced by investment casting is largely determined by the quality of the ceramic molds. Currently, aircraft and engine building enterprises are switching to an environmentally friendly colloidal silica binders for the manufacture of ceramic molds. In this work, the dynamic and relative viscosity of slurries prepared using fused silica powder and colloidal silica binders of the VT13-02U (Vakuumteh LLC), Stavroform VS (Polymet LLC), UltraCast One + and UltraCast Prime (both Technopark LLC) manufacturers were determined. It is shown that the slurries prepared on the considered binders have similar viscosity values, and in their rheological properties they are close to Newtonian liquids. The values of dynamic and relative viscosity at a binder content of 400 mL per 1 kg of fused silica powder were ~732 mPa·s and ~380 s, respectively. With an increase in the binder content to 600 mL per 1 kg of fused silica powder, the dynamic and relative viscosity decreased to ~70 mPa·s and ~16 s, respectively. An equation was also found that relates the dynamic viscosity determined using a rotational viscometer and the relative viscosity determined using the VZ-4 viscosimeter. The mechanical properties were determined during three-point bending tests on ceramic samples obtained using slurries on the above-mentioned colloidal silica binders and fused silica stucco. Samples obtained on binders VT13-02U, Stavroform VS and UltraCast One+ showed very similar bending strength values, namely 3.5–4.3 MPa after drying and 5.8–6.1 MPa after firing. Due to the presence of a polymer addition in the binder, the ceramic samples obtained on the UltraCast Prime binder had higher values of bending strength after drying and after firing – 6.4 and 7.2 MPa, respectively. It was also shown that with an increase in the viscosity of the slurry and a decrease in the fraction of fused silica stucco, the strength of the samples increases. The lowest surface roughness was observed for samples obtained with UltraCast grade binders.

ИЗУЧЕНИЕ ПОРОШКОВ НАНОДИСПЕРСНОГО ДИОКСИДА КРЕМНИЯ, ПОЛУЧЕННЫХ ИЗ ПОБОЧНЫХ ПРОДУКТОВ ПЕРЕРАБОТКИ РУДНОГО СЫРЬЯ, В КАЧЕСТВЕ ДОБАВОК В БЕТОН

Nanodisperse silica powders obtained from eudialyte, nepheline and nepheline-aegirine concentrates have been studied. Powders with a specific surface area of up to 520 m2/g, containing 71–81 wt. % SiO2, were investigated as silica-containing additives in concrete. It is shown that the silica powder isolated from the sulfate solution from the decomposition of nepheline concentrate has the greatest specific surface area and porosity. Optimal dosages of additives from various concentrates in concrete within 0,5–1,0% of the cement weight have been established.

Characterization, Modeling, Experimental Validation and Dielectric Properties Studies of a Ternary Composite (RE-BaTiO3-SiO2) Using Time Domain Spectroscopy

This study aim is to investigate the ternary composites dielectric behavior and experimentally validate the predictive model that simplifies ternary models into binary ones using time domain spectroscopy (TDS). The scattered white silicon dioxide (SiO2) powder was evenly mixed with barium titanate (BaTiO3 or BT) powder in the same epoxy resin (RE) matrix. Over a frequency range from DC to 30 GHz, the dielectric behavior of these composite samples is examined, adding in particular a low frequency study at 500 MHz. The BT addition grew the mixture dielectric permittivity from 3.6063 to 8.2313 and moving the resonance frequency (ƒr) in the direction of the low frequency from 26.245 GHz until 17.09 GHz. By improving the shape factor smoothing and bringing theoretical and experimental results closer together, this seeks to optimize the modified Lichtenecker's law (MLL). These findings comparison demonstrates that the MLL model applies to ternary composites (RE-BT-SiO2) with an acceptable accuracy level. Another numerical method was used to evaluate the RE-[RE-BT-SiO2] composites employing a binary mixing model based on an MLL equation that is identical to the former ternary. This model results correlate well with binary composites experimental values as well as ternaries that are modeled using this law. This research perspective lies on the production of new materials for use in microelectronics and particularly on the MOS structure oxides improvement.

Constructing a Low-Cost Si-NSs@C/NG Composite by a Ball Milling-Catalytic Pyrolysis Method for Lithium Storage.

Silicon-based composites are promising candidates as the next-generation anode materials for high-performance lithium-ion batteries (LIBs) due to their high theoretical specific capacity, abundant reserves, and reliable security. However, expensive raw materials and complicated preparation processes give silicon carbon anode a high price and poor batch stability, which become a stumbling block to its large-scale practical application. In this work, a novel ball milling-catalytic pyrolysis method is developed to fabricate a silicon nanosheet@amorphous carbon/N-doped graphene (Si-NSs@C/NG) composite with cheap high-purity micron-size silica powder and melamine as raw materials. Through systematic characterizations such as XRD, Raman, SEM, TEM and XPS, the formation process of NG and a Si-NSs@C/NG composite is graphically demonstrated. Si-NSs@C is uniformly intercalated between NG nanosheets, and these two kinds of two-dimensional (2D) materials are combined in a surface-to-surface manner, which immensely buffers the stress changes caused by volume expansion and contraction of Si-NSs. Attributed to the excellent electrical conductivity of graphene layer and the coating layer, the initial reversible specific capacity of Si-NSs@C/NG is 807.9 mAh g-1 at 200 mA g-1, with a capacity retention rate of 81% in 120 cycles, exhibiting great potential for application as an anode material for LIBs. More importantly, the simple and effective process and cheap precursors could greatly reduce the production cost and promote the commercialization of silicon/carbon composites.

Mechanochemical dehalogenation of brominated flame retardants and preliminary application for recycling BFR-containing plastic waste

Hexabromocyclododecane (HBCD) is one of the most widely used brominated flame retardant (BFR), which has attracted increasing attention due to the persistence, bioaccumulation and adverse effect to wildlife and human. Considering the strong need for the disposal of HBCD containing waste, mechanochemical (MC) pretreatment technology was investigated to destroy BFRs as a dehalogenation method in this study. Silica and aluminium powders were used as additives, and mechanochemical method was applied to degrade BFRs for both HBCD powder and waste plastics. The results showed that HBCD was effectively degraded during mechanochemical treatment with the aid of Si-Al-based additives. The optimized condition was determined to be a SiO2/Al ratio = 7:2 with a reagent ratio of 15:1. The optimized mechanochemical method was applied to dispose BFRs contained waste plastics. The results showed that dehalogenation of plastics occurs during mechanochemical destruction and that smaller plastic particles accelerated dehalogenation. Finally, the reaction process and intermediates were studied to provide insight into the mechanochemical degradation mechanism of HBCD, and a possible reaction pathway was proposed.

Experimental and simulation study of rubber/cement paste interface modified by waste paint and silica in two stages

The processing of waste tires as one of the raw materials into rubber cement-based materials is gradually developing as an effective method for waste disposal, but the addition of rubber particles can adversely affect the mechanical properties of concrete, and a large number of studies have shown that the weak interfacial transition zone (ITZ) between rubber and cement matrix is one of the key factors limiting the material properties. To address this problem, this paper adopts a bottom-up investigation of the interfacial modification mechanism of rubber cement paste from molecular to macro scales, so as to evaluate the effects of one-stage and two-stage modification of the rubber surface using polyacrylic paint and silica powder on the mechanical properties of rubber-cement paste. Mechanical property tests show that the modified rubber cement paste increased the flexural strength by 13%-34% and the compressive strength by 12%-27% at 28 d age. Contact angle tests and SEM-EDS analysis verify the bridging effect of the modifiers on the interface between rubber and cement paste. Finally, molecular dynamics (MD) simulations reveal that the modified interfacial models have a maximum increase of 38% in pullout force and 71.8% in adhesion energy. Combined with RDF analysis, the modification mechanism is found to enhance interfacial bonding mainly through non-bonding interactions, which explains the mechanism of the one-stage and two-stage modifications from the molecular scale.

The Waterborne Superamphiphobic Coatings with Antifouling, High Temperature Resistance, and Corrosion Resistance.

Water-based superamphiphobic coatings are environment-friendly, which have attracted tremendous attention recently, but the performances are severely limited by the dispersibility of hydrophobic particles. To solve the poor dispersibility of modified silica powder with hydrophobicity, silica dispersion was blended with polytetrafluoroethylene (PTFE) emulsion and modified aluminum tripolyphosphate (ATP) dispersion to successfully prepare water-based coatings. Multifunctional coatings were prepared by one-step spraying. It possessed good adhesion (grade 1), excellent antifouling, impact resistance, chemical stability (acid and alkali resistance for 96 h of immersion), and corrosion resistance (3.5 wt % NaCl solutions for 20 days). More importantly, the superamphiphobic coatings had high contact angles (CAs) and low slide angles (SAs) for ethylene glycol (CAs = 154 ± 0.8°; SAs = 13 ± 0.7°) and water (CAs = 158 ± 0.7°; SAs = 4 ± 0.3°). Furthermore, the composite coating was still hydrophobic after 35 cycles of wear with high roughness sandpaper (120 mesh) under three different loads, which maintained superamphiphobicity at 425 °C. This work is expected to provide a facile idea and method for the preparation of waterborne superamphiphobic coatings.

Durability assessment of quaternary blended recycled aggregate concrete under chloride environment

This article describes the durability of Normally Vibrated Concrete (NVC) containing Recycled Coarse Aggregate (RCA) using different mineral admixtures under extreme chloride environment. Further, to make concrete more sustainable by replacing cement and Natural Coarse Aggregates (NCA) with supplementary cementitious materials and RCA respectively without compromising the performance of concrete. For this, cement is replaced partially with Fly Ash (FA), Silica Powder (SP) and Ground Granulated Blast Furnace Slag (GGBS). The percentage of admixtures (FA, GGBS and silica powder) are decided based on the fresh) and hardened (compressive - strength) properties. M30 concrete is prepared using binary mix (OPC + FA), (OPC + GGBS), ternary mix (OPC + FA + GGBS) and quaternary mix (OPC + FA + GGBS + silica powder). Fresh and mechanical properties of concrete prepared from these mixes are determined. Further the best result of the outcomes based on the above mechanical properties is opted as optimum proportion of (FA, GGBS and silica powder) and is replaced in conventional mix to make concrete more sustainable. This optimum proportion is now used as a new conventional mix for replacing natural coarse aggregate with RCA by % weight varying in proportion 0%, 20%, 40%, 60%, 80% and 100%. For the assessment of durability of concrete Rapid Chloride Permeability Test (RCPT) is carried out. Charge passed through the concrete mix, ingress depth, migration coefficient is noted and relationship between compressive - strength and total charge passed for varying percentage of RCA with optimum proportion of admixtures is analysed. From experimental results it is observed that fly ash, GGBS and silica powder significantly improve the mechanical and durability properties of concrete. Moreover, it is also concluded that up to some extent RCA can be used as alternative of coarse aggregate.

Design and Performance Evaluation of Integrating the Waste Heat Recovery System (WHRS) for a Silicon Arc Furnace with Plasma Gasification for Medical Waste.

A hybrid scheme integrating the current waste heat recovery system (WHRS) for a silicon arc furnace with plasma gasification for medical waste is proposed. Combustible syngas converted from medical waste is used to drive the gas turbine for power generation, and waste heat is recovered from the raw syngas and exhaust gas from the gas turbine for auxiliary heating of steam and feed water in the WHRS. Meanwhile, the plasma gasifier can also achieve a harmless disposal of the hazardous fine silica particles generated in polysilicon production. The performance of the proposed design is investigated by energy, exergy, and economic analysis. The results indicate that after the integration, medical waste gave rise to 4.17 MW net power at an efficiency of up to 33.99%. Meanwhile, 4320 t of the silica powder can be disposed conveniently by the plasma gasifier every year, as well as 23,040 t of medical waste. The proposed design of upgrading the current WHRS to the hybrid system requires an initial investment of 18,843.65 K$ and has a short dynamic payback period of 3.94 years. Therefore, the hybrid scheme is feasible and promising for commercial application.

Microstructure and properties of silica-based ceramic cores by laser powder bed fusion combined with vacuum infiltration

The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability. In this paper, the silica-based ceramic cores reinforced with ZrSiO4 were prepared by laser powder bed fusion (LPBF) combined with vacuum infiltration (VI). To enhance the infiltration effect, the pre-sintered bodies with high porosity and hydrophilicity were obtained by pre-sintering at 1100 °C. Results showed that a large number of silica particles infiltrated into the pre-sintered bodies. The infiltrated silica promoted the generation of liquid phase in sintering, thereby promoting the removal of pores and the connection of grains. Nevertheless, the dispersed ZrSiO4 grains prevented the viscous flow of the liquid phase, thereby increasing the porosity. ZrSiO4 grains could hinder the propagation of cracks due to their high strength. When the addition of ZrSiO4 was 10 wt.%, room-temperature flexural strength of silica-based ceramic cores infiltrated with slurry S1 (the mass ratio of silica sol to silica powder was 10:1) reached 17.21 MPa due to the reinforcement of sintering necks. Moreover, high-temperature flexural strength reached 13.90 MPa. Therefore, the pre-sintering process could greatly improve the mechanical properties of silica-based ceramic cores prepared by LPBF-VI technology.

Effects of nano-fumed silica and carbonyl iron powder of different particle sizes on the rheological properties of shear thickening fluids

Effects of nano-fumed silica and carbonyl iron powder of different particle sizes on the rheological properties of shear thickening fluids

Removal of Manganese Ion Using Integral Membrane Incorporated with Rice Husk Ash

Wastewater treatment is a method of ensuring that the water supply is clean and free from contaminants. Manganese is a pollutant that needs to be removed from the water as it is harmful and usually triggers concern about water quality and water distribution system issues. Besides the adsorption method, membrane technology is efficient due to its mild and environmentally friendly process. This research focused on the production of integral membranes from a blend of polyvinyl alcohol/chitosan/polysulfone/polyethylene glycol cross-linked with silica extracted from rice husk ash (RHA) by using the phase inversion method. The silica was incorporated into the membrane formulation through a sol-gel reaction. The goal of this research was to determine the potential utilization of silica from RHA in the membrane’s formulation to remove manganese ions from various concentrations of manganese solutions. The loadings of RHA were varied at 2, 3 and 5 % wt./wt. polymer. The formulated membranes were then characterized in terms of thermal stability by Thermogravimetric analysis, functional group by Fourier Transform Infrared Spectroscopy, and surface morphology by Scanning Electron Microscopy. The performances of the membranes were tested through filtration of manganese ions solutions and antifouling analysis. The results showed that all membranes including membranes from the polymer blend were able to remove more than 94 % manganese ions. However, the membrane incorporated with 2 % RHA portrayed the best performance in terms of obtaining the highest flux for both water and manganese as feed solution respectively, which also resulted in the highest relative flux recovery ratio at 62.50 % from the antifouling analysis. These findings have proven the successful incorporation of RHA in the form of silica powder, which shows the potential utilization of RHA in membrane fabrication.

Effect of silica powder on microbial-induced carbonate precipitation improvement of medium-coarse sand

Effect of silica powder on microbial-induced carbonate precipitation improvement of medium-coarse sand

Properties Optimization of Soft Magnetic Composites Based on the Amorphous Powders with Double Layer Inorganic Coating by Phosphating and Sodium Silicate Treatment

Core-shell structured amorphous FeSiBCr@phosphate/silica powders were prepared by phosphating and sodium silicate treatment. The soft magnetic composites (SMCs) were fabricated based on these powders. The effects of phosphoric acid (H3PO4) concentration and annealing temperature on their properties were investigated. During the phosphating process, the powder coated with a low concentration of H3PO4-ethanol solution leads to uneven phosphate coating, while the peeling of phosphate coating occurs for the high H3PO4 concentration. Using 0.5 wt.% phosphoric solution, a uniform and dense insulation layer can be formed on the surface of the powder, resulting in increased resistivity and the reduced eddy current loss of the amorphous soft magnetic composites (ASMCs). This insulation layer can increase the roughness of the powder surface, which is beneficial to the subsequent coating of sodium silicate. By optimizing sodium silicate treatment, a complete and uniform SiO2 layer can be formed on the phosphated powders well, leading to double layer core-shell structure and excellent soft magnetic properties. The magnetic properties of amorphous SMCs can be further improved by post annealing due to the effectively released residual stress. The enhanced permeability and greatly reduced core loss can be achieved by annealing at 773 K, but the deterioration of magnetic properties occurs as the annealing temperature over 798 K, mainly due to the increase of α-Fe(Si) and Fe3B phases, which hinder the domain wall displacement and magnetic moment rotation. The excellent soft magnetic properties with permeability μe = 35 and core loss Ps = 368 kW/m3 at 50 mT/200 kHz have been obtained when the SMCs prepared with the powders coated by 0.5 wt.% H3PO4 and 2 wt.% sodium silicate were annealed at 773 K.

An investigation on mechanical and microstructural properties of hybrid fiber reinforced concrete with manufactured sand and recycled coarse aggregate

The emergence of Manufactured Sand (M-Sand) as an alternative to River Sand (R-Sand) and efforts for Recycled Coarse Aggregates (RCA) has opened new opportunities for sustainable growth in urban cities. As a result, M-Sand (100%) and RCA (25%) as sustainable replacement constituents for R-sand and natural coarse aggregates in concrete were utilized to study the mechanical and microstructural properties. The fiber-reinforced concrete with hybrid fibers (steel fiber (SF) + polypropylene fiber (PPF)) was characterized under compression, tension, and flexure. The M-Sand was procured from the local supplier whereas the RCA was prepared in the laboratory employing the treatment using micro silica powder after the mechanical treatment. Overall, it was observed that the synergic use of M-Sand and RCA reduced the workability of concrete. The highest percentage enhancement in compressive and tensile strength on the mix containing M-sand and hybrid (SF (0.75% + PPF (0.1%)) was 27.91% and 57%, respectively as compared to the control mix. The highest flexural toughness (1735%) was observed for concrete containing M-sand and hybrid (SF (0.75% + PPF (0.2%)). The static and dynamic modulus of elasticity of concrete was found to increase with the increase of the percentage of hybrid fiber in the concrete along with M-Sand and RCA. The microstructural analysis indicates significant enhancements for the concrete mix containing M-Sand and treated RCA. Also, it was observed from X-ray diffraction analysis that the peak intensity of quartz in the mix combination of M-Sand and RCA was found to be higher as compared to other mixes which contribute to the higher strength. It is concluded that M-sand contributes to the performance equivalent to the natural fine sand and is found to be a more economical concrete mix with similar Global warming potential and embodied energy characteristics.

Study on Nonlinear Dielectric Properties of Micro Silica

Inorganic insulating powder can potentially be used in nuclear power plant cables, fire-resistant cables, and so on due to its high heat resistance and radiation resistance. It is of great academic and engineering value to study the dielectric properties of inorganic insulating powder. In this paper, we aim to study the nonlinear dielectric properties via the measurement of the time-domain polarization current spectrum under the application of a DC electric field. Three kinds of silica powders are measured by a measurement system with adjustable pressure. The effects of powder shape, particle size, and packing pressure and temperature on the dependence of relaxation polarization and electrical conductivity on the applied electric field are studied. The experimental results show that the relationship between electrical conductivity and the electric field of inorganic insulating powder presents two different characteristics, i.e., field-induced enhancement and field-induced weakening. The relationship between conductance and temperature shows an increase with temperature. That is, the electrical conductivity increases or decreases with the increase in temperature. The inorganic powder insulation can be regarded as a composite, which is composed of inorganic powder particles and air gaps. The interface between the powder particles and air gaps contributes a lot to the polarization of inorganic insulating powder. The phenomena (including the field-induced weakening characteristic between relaxation polarization and electric field and the decrease characteristic of polarization with increasing temperature) can be explained by a simplified interface polarization mechanism.

Using Nicotine in A Silica-Exposed Mouse Model to Promote Lung Epithelial-Mesenchymal Transition.

Smoking and exposure to silica are common among occupational workers, and silica is more likely to injure the lungs of smokers than non-smokers. The role of nicotine, the primary addictive ingredient in cigarettes, in silicosis development is unclear. The mouse model employed in this study was simple and easily controlled, and it effectively simulated the effects of chronic nicotine ingestion and repeated exposure to silica on lung fibrosis through epithelial-mesenchymal transition in human beings. In addition, this model can help in the direct study of the effects of nicotine on silicosis while avoiding the effects of other components in cigarette smoke. After environmental adaptation, mice were injected subcutaneously with 0.25 mg/kg nicotine solution into the loose skin over the neck every morning and evening at 12 h intervals over 40 days. Additionally, crystalline silica powder (1-5 µm) was suspended in normal saline, diluted to a suspension of 20 mg/mL, and dispersed evenly using an ultrasonic water bath. The isoflurane-anesthetized mice inhaled 50 µL of this silica dust suspension through the nose and were awoken via chest massage. Silica exposure was administrated daily on days 5-19. The double-exposed mouse model was exposed to nicotine and then silica, which matches the exposure history of workers who are exposed to both harmful factors. In addition, nicotine promoted pulmonary fibrosis through epithelial-mesenchymal transformation (EMT) in mice. This animal model can be used to study the effects of multiple factors on the development of silicosis.

Shaping metal-organic framework (MOF) with activated carbon and silica powder materials for CO2 capture

Metal-organic framework (MOF) UTSA-16 (Co) was shaped into pellets with diameters of 0.2 mm using activated carbon (AC), silica, and 8% polyvinyl butyral (PVB)/ethanol solution as a binder. A series of AC and silica pellets was prepared with different percentages of the UTSA-16 (Co) MOF. As the percentage of UTSA-16 (Co) increased, the CO2 adsorption capacity and CO2/N2 selectivity of the AC and silica pellets increased. AC/UTSA-16 (Co)− 30% pellets showed 83% enhancement in CO2 adsorption capacity and 800% improvement in CO2/N2 selectivity at 298 K compared to the AC pellet. The stability of AC-UTSA-16 (Co) pellets was analyzed by exposing them to SO2 and NO2 for 2 days. The performance of AC was further investigated by preparing an AC composite pellet using UTSA-16 (Zn). AC/UTSA-16 (Zn)− 30% pellets showed 75% enhancement in CO2 adsorption capacity and 1000% improvement in CO2/N2 selectivity than parent AC pellet. CO2 adsorption–desorption cycles were performed to examine the long-term stability of the pellet composites. The pellets were characterized by scanning electron microscopy (SEM) for particle morphology, thermogravimetric analysis (TGA) for thermal stability, and Brunauer–Emmett–Teller (BET) method for structural properties.