Papers by Keyword: Silicon Dioxide

Abstract: Paper investigates the possibility of producing silicon from silica contained in Shoda-Kedela (Oni-Gebi district, Georgia) quartz deposition. Characterization of silica from Shoda-Kedela quartz rock is carried by its crushing, grinding, thermal analysis, studying composition and density. Metallurgical grade silicon (MG-Si) is obtained by reducing Shoda-Kedela quartz in its reaction with coke in an electric arc furnace at temperature of ~1800°C. The obtained in this way material reveals that Shoda-Kedela silica containing of 99.58% SiO₂ would be useful for developing the silicon high-technology production.

Abstract: The manuscript investigates the leaf-shaped nanostrip-fed graphene plasmonic nanopatch on a silicon dioxide surface for optical near-field applications. The dispersion properties of graphene and silicon dioxide are demonstrated through Drude and Lorentz modeling to examine the suitability of the materials for the plasmonic nano-antenna design. The nano-antenna parameters T_SUB (substrate thickness), W (width of the nanostrip feed line) and R_L (nano-antenna size) are adjusted to modify the plasmonic resonance frequency from 7.9 THz to 40.9 THz. The proposed leaf-shaped nanostrip-fed graphene plasmonic nanopatch exhibits a reflection of -43.27 dB at 36 THz with a gain of 8.19 dB at T_SUB =125 nm, W = 40 nm and R_L = 50 nm.

Abstract: A study on the impact of different growth and deposition techniques on the reliability of silicon dioxide (SiO₂) layers on silicon carbide (SiC) metal-oxide-semiconductor capacitors (MOSCAPs) is presented and compared to channel mobilities that were extracted from lateral metal-oxide-semiconductor field-effect transistors (LMOSFETs). Oxide layers were formed using atomic layer deposition (ALD), low pressure chemical vapour deposition (LPCVD) and direct thermal growth, including post-deposition anneals (PDAs) in nitrious oxide and forming gas (FG) for the ALD-and LPCVD-deposited oxides. Electrical characterisation results at elevated temperatures show that a PDA in FG leads to the highest average breakdown electric field of 10.08 MV/cm, outperforming all other device splits. Time-dependent dielectric breakdown (TDDB) results showed that the time to failure of 63% of the investigated samples at 9MV/cm in the FG-annealed samples was about 50% higher than in LPCVD-deposited oxides that had undergone an N₂O PDA. Channel mobilities of the FG-treated samples averaged about three to four times higher than in other datasets, showing excellent peak field-effect mobilities of 60 cm²/V.s and 108 cm²/V.s at room temperature and 175°C, respectively.

Abstract: This work is focused on the preparation and characterization of poly (vinyl alcohol)/silica gel/Nano-TiO₂, and the study of titanium dioxide (TiO₂) nanoparticles (from 1 to 5%) on the properties of poly (vinyl alcohol) (PVA)/silica films. This new material was prepared by the sol-gel method using poly (vinyl alcohol) powder with Tetraethyl Orthosilicate (TEOS) as a precursor source of silica. TEOS was hydrolyzed and condensed in water and ethanol in the presence of hydrochloric acid (HCl) used as a catalyst. Fourier transform infrared (FT-IR), water absorption, water contact angle, ultraviolet-visible spectrometry (UV-VIS), and thermogravimetric analysis (TGA) were used to characterize the hybrid films obtained. The PVA/SiO₂/Nano-TiO₂ films were successfully synthesized. Owing to the FT-IR Analysis, the chemical bonds have clearly shown that the PVA backbone is linked to the (SiO₂-TiO₂) network. UV-VIS tests indicated that the hybrid films' UV shielding properties were drastically enhanced as a result of the addition of TiO₂. According to the TGA tests, the hybrid films are more heat tolerant than neat PVA films. The water contact angle results revealed that TiO₂ nanoparticles used as a doping compound possess an important influence on the hydrophilicity of PVA/SiO₂ as thin films. The film's water resistance has also been enhanced.

Abstract: The article presents the results of silicon dioxide leaching from quarry waste dumps with silicon content of 50% and more. NaOH solution was used as a leaching agent and H2SO4 solution as a precipitant. The influence of basic parameters on the leaching process (concentration of leaching agent, operating temperature, ratio of liquid phase to solid phase, stirring speed) and on the precipitation process (concentration of the precipitant and temperature) was investigated. As a result of using the optimal parameters a high efficiency of silica powder production of 98.7 % was achieved. The powder is presented mainly in the form of particle agglomerates. The average particle size is 300-700 nm, the size of agglomerates is more than 700 nm. The structure is predominantly porous.

Abstract: There is presented the method of silicon dioxide obtaining by its extraction from silica-containing solution from nepheline decomposition with the acetone and ethanol help with organic phase subsequent gelatinisation. Structural and surface properties of the obtained SiO₂ samples were investigated. The specific surface area of the obtained samples depends on the preparation method and varies in the range from 559 to 626 m²/g. The particles average diameter varies in the given series of samples from 2.26 to 6.68 nm. It has been found that the use of extraction has no destructive effect on the SiO₂ specific surface area and maintains its original microporous structure.

Abstract: Intumescent fire-retardant coatings based on epoxy resins, compared to traditional fire-retardant compositions, have improved performance properties – high strength, chemical and atmospheric resistance, adhesion to many materials. However, unmodified epoxy polymers are combustible and to obtain IFR based on them, flame retardants and mineral fillers are added to their composition. Intumescent systems for flame retardant coatings based on epoxy oligomers (non-halogen-containing) usually consist of ammonium or ammophos polyphosphate as an acidic agent and a wide range of fillers, both inert and gaseous, or which are an additional source of carbon. Each component of the fire-retardant intimate coating in different ways affects the processes of coke formation, which determines the requirements for their choice. Thus, the aim of this work is to conduct experimental studies of the dependence of the characteristics of the expanded coke layer on the composition of the intumescent epoxyamine composition. The results of experimental studies of the effect of ammonium polyphosphate and binary mixtures of ammonium polyphosphate (APP) with aluminum hydroxide (AH), sodium tetraborate decahydrate (STD), titanium oxide TiO₂ (TO), pentaerythritol (P), aerosil (A) and expandable graphite are presented (EG) on the multiplicity of expanding and weight loss of epoxy compositions at study temperatures of 350, 400 and 450°C. Studies have shown that the production of intumescent flame retardant coatings based on epoxy oligomers is possible provided they are filled with ammonium polyphosphate in an amount of more than 20 mass parts. The most effective in terms of expanding are additives titanium oxide and aluminum hydroxide in an amount of 20 mass parts, which allows to obtain intumescent fire-retardant coatings with a linear coefficient of expanding 30-32 and 24-27, respectively, throughout the range of temperatures. The obtained data are useful in the development of fire-retardant coatings based on epoxy oligomers.

Abstract: Ultrasonic dispersion of a silica hydrosol is compared with the effects of mechanical activation through the combined action of high shear stresses, ultrasound and cavitation. This action leads to breaking the siloxane bonds and increasing the content of silanol groups. The mechanical activation of binary silica system with acrylate dispersion promotes a chemisorption of oligoacrylate with the formation of Si – O – C and Si – C bonds. The effect of modification of oligoacrylate on the formation of a graft-copolymer and the stiffness of a composite material was evaluated.

Abstract: The optical properties of silicon dioxide hollow particles with different size were investigated in UV/visible/near-IR region, as well as X-ray photoelectron spectra were analyzed. Synthesis of SiO2 hollow particles was carried out using a template method. It was established that hollow particle reflectance lower than bulk microparticles. Absorptance in the red and near infrared spectral ranges increases with decreasing size of hollow particles, but in the UV-region conversely. This is due to different absorption centers.

Abstract: The paper investigates the influence of an electrophilic agent in the inorganic polysulfide technology. A tight contact between the modified silicate filler and sulfur (when heated and then pressed) results in the appearance of new interatomic bonds and interphase interaction forces to ensure the best possible structure formation in a system in the micro and macro level. Cross-linking of silica gel by disulfide fragments shows greater stability. The activation energies were calculated for insertion of diatomic sulfur (singlet and triplet) by an oxygen atom and a silicon atom, with the substitution of OH-group, as well as for addition of diatomic sulfur to the surface of silica gel modified with aluminum chloride. Aluminum chloride acts as an activator for both a silica-containing material and sulfur, and encourages the chemical interaction between the components, and formation of polysulfides and sulfur materials from them, which have high physical mechanical properties.