Showing papers on "Silicon dioxide published in 2020"

Distinct Behaviors between Gypsum and Silica Scaling in Membrane Distillation

Abstract: Mineral scaling constrains membrane distillation (MD) and limits its application in treating hypersaline wastewater. Addressing this challenge requires enhanced fundamental understanding of the scaling phenomenon. However, MD scaling with different types of scalants may have distinctive mechanisms and consequences which have not been systematically investigated in the literature. In this work, we compared gypsum and silica scaling in MD and demonstrated that gypsum scaling caused earlier water flux decline and induced membrane wetting that was not observed in silica scaling. Microscopic imaging and elemental mapping revealed contrasting scale morphology and distribution for gypsum and silica, respectively. Notably, while gypsum crystals grew both on the membrane surface and deep in the membrane matrix, silica only formed on the membrane surface in the form of a relatively thin film composed of connected submicrometer silica particles. We attribute the intrusion of gypsum into membrane pores to the crystallization pressure as a result of rapid, oriented crystal growth, which leads to pore deformation and the subsequent membrane wetting. In contrast, the silica scale layer was formed via polymerization of silicic acid and gelation of silica particles, which were less intrusive and had a milder effect on membrane pore structure. This hypothesis was supported by the result of tensile testing, which showed that the MD membrane was significantly weakened by gypsum scaling. The fact that different scaling mechanisms could yield different consequences on membrane performance provides valuable insights for the future development of cost-effective strategies for scaling control.

Siliplant1 protein precipitates silica in sorghum silica cells

Abstract: Silicon is absorbed by plant roots as silicic acid. The acid moves with the transpiration stream to the shoot, and mineralizes as silica. In grasses, leaf epidermal cells called silica cells deposit silica in most of their volume by unknown mechanism. Using bioinformatics tools, we identified a previously uncharacterized protein in sorghum (Sorghum bicolor), which we named Siliplant1 (Slp1). Slp1 is a basic protein with seven repeat units rich in proline, lysine, and glutamic acid. We found Slp1 RNA in sorghum immature leaf and immature inflorescence. In leaves, transcription was highest just before the active silicification zone (ASZ). There, Slp1 was localized specifically to developing silica cells, packed inside vesicles and scattered throughout the cytoplasm or near the cell boundary. These vesicles fused with the membrane, releasing their content in the apoplastic space. A short peptide that is repeated five times in Slp1 precipitated silica in vitro at a biologically relevant silicic acid concentration. Transient overexpression of Slp1 in sorghum resulted in ectopic silica deposition in all leaf epidermal cell-types. Our results show that Slp1 precipitates silica in sorghum silica cells.

A Novel Correlation to Calculate Thermal Conductivity of Aqueous Hybrid Graphene Oxide/Silicon Dioxide Nanofluid: Synthesis, Characterizations, Preparation, and Artificial Neural Network Modeling

Abstract: Graphene oxide is generally used in hydrogen storage, energy conversion, lens, and flexible rechargeable battery electrode. Silica is one of the most plentiful families of materials, which has potential to be an excellent choice for industrial applications due to its low-cost production, high specific surface area, and also its hydrophilicity. Hybrid nanofluid (HN) is one of nanofluid types in which more than one solid particle dispersed in a fluid. In this paper, after preparation of graphene oxide/silicon dioxide/water hybrid nanofluid, thermal conductivity (TC) was studied and numerically modeled. Then, to study phase and structural analysis, X-ray diffraction analysis and dynamic light scattering analysis were employed. After that, scanning electron microscope was used to study microstructural observation of nanoparticles. TC measurements of HN were taken at volume fractions of 0.05–1.0% and at temperature ranges of 25–50 °C. Thermal conductivity enhancement of 26.93% was measured at 1.0 vol.% fraction in 50 °C temperature. For numerical modeling, new correlation has been offered (R2 = 0.9), and further, artificial neural network has been modeled (R2 = 0.999). For offered correlation, 1.48% deviation and for trained model, 1.26% deviation were calculated. Totally, GO–SiO2–H2O HN has acceptable heat transfer potential.

Effect of ZnO on the phase transformation and optical properties of silicate glass frits using rice husk ash as a SiO2 source

Abstract: This research attempts to propose the fabrication and characterization of highly amorphous zinc silicate glasses derived from zinc oxide (ZnO) and white rice husk ash (WRHA). Three zinc silicate glasses were produced based on empirical formula (ZnO)x(WRHA)1−x where x = 0.50, 0.55 and 0.60 wt.% by using melt-quenching methods. When ZnO increased, the transparency of the three glasses increased. Meanwhile, X-ray diffraction (XRD) analysis of the zinc silicate glasses revealed that the glassy state of the zinc silicate glasses increased along with the increment of ZnO, and at lowest ZnO (0.50 wt.%), the presence of silicon dioxide (SiO2) peak were observed showing uncomplete melted of silica. Additional vibrational band due to the presence of tridymite was found in the Fourier transform infrared spectroscopy (FTIR) at lowest ZnO content supporting the XRD result while other glasses showed the formation of zinc silicate glasses with the presence of SiO4 and ZiO4 vibrational band. The zinc silicate absorption also increased as the ZnO increased as a result from the formation of non-bridging oxygen (NBO's). Hence, optical band gap of zinc silicate glasses was decreased from 4.35 to 4.23 eV as the ZnO increased due to increment of NBO's. All zinc silicate glasses showed three different emission peaks which is at 535, 596 and 728 nm correspond to green, yellow and red emission respectively. This luminescence properties of zinc silicate were attributed to the defect inside the ZnO particle.

Hybrid flat sheet cellulose acetate/silicon dioxide ultrafiltration membranes for uremic blood purification

Abstract: Monophasic hybrid cellulose acetate/silica (CASiO2) integrally skinned membranes with tailored hemocompatible surfaces and permeation properties that assure the kidney metabolic functions of preferential permeation of urea and the retention of albumin were synthesized by an innovative method which combines the phase inversion and sol–gel techniques. The morphological and topographical characterization of the hybrid CASiO2 membranes with silica contents between 5 and 18 wt% was performed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Static contact angles were measured through the sessile drop method and permeation experiments were performed to determine the hydraulic permeability and rejection coefficients to reference solutes pertaining to the metabolic functions of the kidney. SEM confirmed asymmetric membrane cross-section structures and AFM showed that the introduction of silica reduced the submicron surface roughness at least 3 times when compared to the pure CA membrane, reaching a roughness mean value below 2.5 nm. Contact angles revealed that the wettability increased for membranes containing 11 and 18 wt%. Permeation studies show that the integration of silica into CA membranes increased the hydraulic permeability of the hybrid CASiO2 membranes by a factor of ~ 2 and that all hybrid membranes fully permeated urea and completely rejected albumin. In terms of hemocompatibility, all CASiO2 membranes were non-hemolytic, low thrombogenic and did not promote the highest stages of platelet activation.

Manipulation of thin silver film growth on weakly interacting silicon dioxide substrates using oxygen as a surfactant

Abstract: The authors study the morphological evolution of magnetron-sputtered thin silver (Ag) films that are deposited on weakly interacting silicon dioxide (SiO2) substrates in an oxygen-containing (O-2) ...

Unique lignin modifications pattern the nucleation of silica in sorghum endodermis.

Abstract: Silicon dioxide in the form of hydrated silica is a component of plant tissues that can constitute several percent by dry weight in certain taxa. Nonetheless, the mechanism of plant silica formation is mostly unknown. Silicon (Si) is taken up from the soil by roots in the form of monosilicic acid molecules. The silicic acid is carried in the xylem and subsequently polymerizes in target sites to silica. In roots of sorghum (Sorghum bicolor), silica aggregates form in an orderly pattern along the inner tangential cell walls of endodermis cells. Using Raman microspectroscopy, autofluorescence, and scanning electron microscopy, we investigated the structure and composition of developing aggregates in roots of sorghum seedlings. Putative silica aggregation loci were identified in roots grown under Si starvation. These micrometer-scale spots were constructed of tightly packed modified lignin, and nucleated trace concentrations of silicic acid. Substantial variation in cell wall autofluorescence between Si+ and Si- roots demonstrated the impact of Si on cell wall chemistry. We propose that in Si- roots, the modified lignin cross-linked into the cell wall and lost its ability to nucleate silica. In Si+ roots, silica polymerized on the modified lignin and altered its structure. Our work demonstrates a high degree of control over lignin and silica deposition in cell walls.

Silicon-Based Anode of Lithium Ion Battery Made of Nano Silicon Flakes Partially Encapsulated by Silicon Dioxide

Abstract: Ubiquitous mobile electronic devices and rapidly increasing electric vehicles demand a better lithium ion battery (LIB) with a more durable and higher specific charge storage capacity than traditional graphite-based ones. Silicon is among the most promising active media since it exhibits ten times of a specific capacity. However, alloying with lithium by silicon and dissociation of the silicon-lithium alloys induce high volume changes and result in pulverization. The loss of electrical contacts by silicon with the current collector of the anode causes rapid capacity decay. We report improved anode cycling performance made of silicon flakes partially encapsulated by silicon dioxide and coated with conductive nanocarbon films and CNTs. The silicon dioxide surface layer on a silicon flake improves the physical integrity for a silicon-based anode. The exposed silicon surface provides a fast transport of lithium ions and electrons. CNTs and nanocarbon films provide electrical connections between silicon flakes and the current collector. We report a novel way of manufacturing silicon flakes partially covered by silicon dioxide through breaking oxidized silicon flakes into smaller pieces. Additionally, we demonstrate an improved cycling life and capacity retention compared to pristine silicon flakes and silicon flakes fully encapsulated by silicon dioxide. Nanocarbon coatings provide conduction channels and further improve the anode performance.

Improved impact strength of poly(lactic acid) by incorporating poly(butylene succinate) and silicon dioxide nanoparticles

Abstract: The surface of silicon dioxide (SiO2) nanoparticles was treated with oleic acid, and the resulting surface properties were characterized. Bio-based poly(lactic acid) (PLA)/poly(butylene succinate)/SiO2 nanocomposites were fabricated via solution blending. The influence of the SiO2 content on the thermal stability, flexural properties, impact strength, and morphology of the prepared nanocomposites was investigated using several techniques. The impact strength of the nanocomposites with surface treated SiO2 (O-SiO2) nanoparticles substantially increased with increasing O-SiO2 content from 0 to 3 wt%. Scanning electron microscopy imaging revealed that the nanocomposites with O-SiO2 nanoparticles exhibited numerous tortuous cracks and ridges, indicating ductile deformation prior to fracturing.

Covalent Grafting of Polyoxometalate Hybrids onto Flat Silicon/Silicon Oxide: Insights from POMs Layers on Oxides

Abstract: Immobilization of polyoxometalates (POMs) onto oxides is relevant to many applications in the fields of catalysis, energy conversion/storage, or molecular electronics. Optimization and understandin...

Experimental Investigation for Performance Study of Wire Electrochemical Spark Cutting of Silica Epoxy Nanocomposites

Abstract: Polymer Nanocomposites are advanced engineering composites with enhanced properties. These materials play a central role in various industrial sectors. The growing awareness of the key parameters (which influence the physical properties) with different combination of matrix-reinforcement, are making them more attractive in various applications. Machining of these materials is a challenging task for engineers with their properties (hardness and brittleness) due to various combinations of matrix-reinforcement. Therefore, the aim of present work is to investigate the machining behaviour of Silicon Dioxide (silica) Epoxy Nanocomposite due to straight cutting by using Wire Electrochemical Spark Cutting (WECSC) process. A specific number of experiments were conducted based on one parameter at-a-time approach to study the effect of influencing input parameters. The effect of various process parameters namely voltage supply, electrolyte concentration, wire velocity, pulse-on time and silica particle concentration (Cp) such as 3%, 4% and 5% (weight percent) on performance measures such as material removal rate (MRR) and surface roughness were demonstrated experimentally. WECSC has been found effective technique for cutting of Silicon Dioxide Epoxy Nanocomposite. It is reported that MRR increases with decrease in silica particle concentration in Silicon Dioxide Epoxy Nanocomposite.

Physico-chemical properties of biogenic SiO 2 nanoparticles obtained from agriculture residue

Abstract: Plant-based biogenic silicon dioxide nanoparticles are used to produce catalysts, additives, templates for deposition of other semiconductors and metals, nanomaterials with novel properties, bio-nanocomposites for biomedical, energy and environmental fields. There are too many ways of bio-SiO2 production. Dependent on the way and obtaining condition some properties of the plant-based biogenic silicon dioxide nanoparticles can be changed. The most amount of silicon is accumulated in stalks and husk biomass of rice, buckwheat and oats. The aim of our work was the investigation of physic-chemical properties of the biogenic silicon dioxide obtained from the rice husk by both ecologically- and economically-friendly technology. The fluoric technology was used for silicon dioxide isolation. Our technology allows us to restore used catalysts. Thus this technology is ecologically and economically efficient. The synthesised SiO2 was studied by using the following methods: low-temperature nitrogen sorption–desorption, XRD, XRF, ICP-MS, AFM, FTIR-ATR, SEM-EDS, TGA. It was established that obtained samples had a specific surface area 107 m2/g. The XRD of the powdered SiO2 showed 100% amorphous characteristics of the material. FTIR, XRF SEM-EDS, ICP-MS and X-ray diffraction indicated that samples contain only SiO2. AFM results show obtained silica particles were having shape from spherical to lamellar. According to SEM investigated sample consists of spherical small aggregates.

Biosilica Properties from Rice Husk using Various HCl Concentrations and Frequency Sources

Abstract: Rice husk is a by-product of rice milling with more than 90% of silicon dioxide. The objective of this research was to characterize the purity and electricity as well as structure property and surface morphology of silicon dioxide depending on different concentration of chloride acid (HCl). The experimental consisted of leaching the rice husk using HCl solutions of 1%, 3%, and 5% for 2 hours and burning it at several annealing temperatures and times with temperature rate of 1 °C.min-1. The analysis included purity and morphology, structure property, and electricity of silicon dioxide using EDX-SEM, XRD, and LCR meter, respectively. The EDX measurement indicated that the higher the concentration of HCl, the higher the purity of silicon dioxide. Additionally, the higher the concentration of HCl led to the higher the electrical conductance, conductivity, and dielectric constant. While, the higher the frequency led to the higher the electrical conductance and conductivity but the lower the dielectric constant. Based on these electrical properties, silicon dioxide from rice husk can be applied as both an insulator and semiconductor materials on electronic devices.

Enhanced green photoluminescence and dispersion of ZnO quantum dots shelled by a silica shell

Abstract: Zinc oxide (ZnO) quantum dots (QDs) stabilized/functionalized with oleic acid and core-shelled with silicon dioxide (SiO2) are presented A colloidal route, free surfactant was followed to synthesize ZnO QDs with an average size of 5 nm After, the ZnO QDs were stabilized with oleic acid to avoid aggregation followed by (3-aminopropyl) trimethoxysilane functionalization The X-ray diffraction patterns and transmission electron microscopy results indicated that the ZnO QD size and morphology did not suffer any change after functionalization In addition, the photoluminescence measurements showed a strong green emission band related to particle size and the shell formation Moreover, the quantum yield and z potential values were determined and the results showed an enhanced for those ZnO@SiO2 samples with 10 wt% of shell precursor In this research, we report a high relationship between the stability and photoluminescence properties with the shell precursor concentration Furthermore, we have developed a reliable method to obtain functionalized ZnO QDs which offer a great potential for future use as photoemission devices such as photonics, photocatalytic activities, biomedicine, optoelectronic devices, and chemical sensing

Anisotropic Etching of Pyramidal Silica Reliefs with Metal Masks and Hydrofluoric Acid.

Abstract: This work describes the fabrication of anisotropically etched, faceted pyramidal structures in amorphous layers of silicon dioxide or glass. Anisotropic and crystal-oriented etching of silicon is well known. Anisotropic etching behavior in completely amorphous layers of silicon dioxide in combination with purely isotropic hydrofluoric acid as etchant is an unexpected phenomenon. The work presents practical exploitations of this new process for self-perfecting pyramidal structures. It can be used for textured silica or glass surfaces. The reason for the observed anisotropy, leading to enhanced lateral etch rates, is the presence of thin metal layers. The lateral etch rate under the metal significantly exceeds the vertical etch rate of the non-metallized area by a factor of about 6-43 for liquid and 59 for vapor-based processes. The ratio between lateral and vertical etch rate, thus the sidewall inclination, can be controlled by etchant concentration and selected metal. The described process allows for direct fabrication of shallow angle pyramids, which for example can enhance the coupling efficiency of light emitting diodes or solar cells, can be exploited for producing dedicated silicon dioxide atomic force microscopy tips with a radius in the 50 nm range, or can potentially be used for surface plasmonics.

Effect of K2CO3 as an Additive Agent on the Carbothermic Reduction Process of Silicon Production

Abstract: The effect of K2CO3 as an additive agent in the carbothermic reduction process of silicon production is investigated in this study. Using a thermogravimetric analyzer (TGA) in argon atmosphere, different proportions of petroleum coke (PC) and pomelo peel (PP) are used as the carbonaceous reducing agent. Findings show that the additive displays catalytic activities for reductant composition of PC and PP in solid state under high temperature. The maximum mass loss rate of samples with additive is found to increase by 13.7% in the same conditions, compared to samples without the additive. In addition, a homogenous model (HM) is studied as a kinetic model using the Coats-Redfern method to observe and determine the kinetic parameters of all samples. High correlation coefficient values for the pyrolysis stages (R2 > 0.99) and the carbothermic reduction stage of silicon dioxide (R2 > 0.98) are obtained for all samples, illustrating that the kinetic model is applicable to this reaction process. According to findings in this study, the additive K2CO3 is determined to positively impact reaction activity, speeding up the rate of pyrolytic reaction and the carbothermic reduction of silica.

Chemical mechanical polishing solution and application thereof

Abstract: The invention provides a chemical mechanical polishing solution that comprises silicon dioxide grinding particles, a nitrogen-containing heterocyclic compound containing one or more carboxyl groups, and ethoxylated butoxylated alkyl alcohol. The invention further provides application of the chemical mechanical polishing solution in polishing of silicon dioxide, polycrystalline silicon and siliconnitride. The polishing speed of the polishing solution on silicon nitride is far higher than that on silicon dioxide and polycrystalline silicon, so that the polishing solution can be well applied tochemical mechanical polishing with silicon dioxide/polycrystalline silicon as a stop layer; therefore, the removal amount of oxide and polycrystalline silicon on the surface of a substrate in the polishing process can be well controlled.

Submicron inorganic particles as an additional filler in hybrid epoxy matrix composites reinforced with glass fibres

Abstract: In this study, the effect of selected submicron metal oxide (zinc oxide, titanium oxide) or non-metal oxide (silicon dioxide) particles on mechanical and thermo-mechanical properties of epoxy/glass...