Papers by Keyword: Silicon Dioxide

Abstract: Carboxylic acids of various carbon chain lengths (C_n); i.e. butanoic acid (C₄), octanoic acid (C₈), dodecanoic acid (C₁₂) and hexadecanoic acid (C₁₆) have been used to organically modify silicon dioxide (SiO₂). The acid modification involve replacing the hydrogen atom of the silanol group (Si-OH) of SiO₂ with the R_nCOO-of the acid via esterification technique. SiO₂ and acid modified SiO₂ (MoC_n-SiO₂) were used as filler in preparation of polymethyl methacrylate/50% epoxidized natural rubber electrolytes containing SiO₂ (PEL-SiO₂) and MoC_n-SiO₂ (PEL-MoC_n-SiO₂) via solvent casting method with lithium tetrafluoroborate (LiBF₄) as dopant salt. Field-emission scanning electron microscopy (FESEM) analysis of PEL-SiO₂ and PEL-MoC_n-SiO₂ films show LiBF₄ accumulated to the fillers. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed formation of hydrogen bonding between LiBF₄ with fillers and polymers in the polymer electrolyte films. Interestingly, the ionic conductivity of PEL-MoC_n-SiO₂ films increases as the C_n of acids increased with the highest ionic conductivity of 5.56 x 10^-7 Scm^-1 was achieved in PEL-MoC₁₂-SiO₂ film.

Abstract: The paper is devoted to studying the effect of the specific surface area (SSA) of SiO₂ nanopowders (3 wt.%) added to BaSO₄ powders of a micron size on grain size distribution and diffuse reflectance spectra (ρ_λ) within the UV, visible, and near IR regions. Additionally, the authors have examined the spectra alteration (Δρ_λ) after irradiating with electrons (E=30 KeV). It has been established that mere mixing of the powders at a low concentration of nanoparticles leads to the post-irradiation decrease in the reflective power and to the subsequent increase in the reflectance coefficient stability.

Abstract: The survey of modern methods of silumins obtaining has been conducted. The prospects of silumins obtaining using amorphous silica caused by, firstly, with a high yield of silicon production waste; secondly, with the lost profit from their industrial use and, thirdly, with the increasing of efficiency of silumins production process by omitting partially the energy-consuming stage of metallurgical silicon production. Thermodynamic possibility of silicon dioxide reduction in aluminum melt has been determined. The method of aluminum-silicon alloys production by introducing preheated amorphous silica into the aluminum melt together with argon stream (with subsequent intensive mixing and casting into the electromagnetic crystallizer) has been studied. It has been determined that this method can allow to produce pre-eutectic aluminum-silicon alloys with more than 5 wt.% of silicon.

Abstract: The paper investigates the recovery problem of waste sulfur from metallurgical, oil and gas plants. The method was developed to synthesize inorganic sulfides and sulfur concretes from them using the activating agent – titanium chloride and different silica-containing raw materials. The chemical interaction between sulfur, titanium tetrachloride and silicon dioxide encourages the formation of a strong and compact structure in the material. The physical chemical and quantum chemical calculations confirmed the formation of titanium silicate sulfide and made it possible to suggest the concept of sulfur concrete synthesis. It was found how the amorphous component in the filler influenced the properties of sulfur concrete. The physical mechanical tests were performed on the specimens of sulfur concrete, based on opal crystobalite rock from the different fields. The optimum sulfur concrete formulation was determined. The specimens with the optimum composition have high coefficient of resistance to HCl, H₂SO⁴, CaCl₂, NaCl, MgSO₄ solutions, high impact resistance, freeze resistance and density to meet GOST concrete standard. The resulting materials can be used for production of some construction materials: paving slabs and blocks, road building materials.

Abstract: A technology for the production of sulfur composite materials based on waste from BaCl₂ at Karpov Mendeleyevsk Plant (Russia) was developed. The physical chemical and quantum chemical studies were performed for the “sulfur – sulfide containing industrial waste–filler” system. The usage of sulfide ion CaS enables sulfur activation to promote the chemical interaction between the components and synthesis of sulfides and sulfur materials with high physical mechanical properties from them.

Abstract: This paper presents a study on monitoring the native oxide growth on silicon micro-pillars. It also presents a comparison between the rates of oxide growth on pillars fabricated using the reactive ion etching (RIE) approach and the metal assisted chemical etching (MACE) approach. The native oxide growth is monitored using photoluminescence (PL) measurements. PL measurements showed that native silicon oxide grows at a higher rate on MACE pillars compared to RIE pillars. SEM images showed that the MACE pillars exhibit a porous outer layer while the RIE pillars show a dense outer layer. It is concluded that the porosity of the pillars enhances the native oxide growth.

Abstract: In this paper, the effect of ratio of silicon dioxide and graphite for the synthesis of silicon carbide nanowhiskers by microwaves heating was reported. The mixtures of SiO₂ and graphite with different ratio were prepared by ultrasonic mixing using ethanol as medium. The mixtures were dried on hotplate and cold pressed by using hydraulic hand press uniaxially into a pellet die. The mixture in the form of pellet were heated up to 1400 °C at heating rate of 20 °C/min and soaked for 30 minutes. Scanning electron microscopy was used to study the morphology of sample of each different ratio of mixture. It was found that almost complete conversion of graphite and silica to silicon carbide nanowhiskers was observed for sample of mixture SiO₂ and graphite in the ratio of 1:3. Result from x-ray diffraction analysis also indicated that single β-SiC phase was present in the diffractogram of silicon carbide nanowhiskers synthesized from mixture SiO₂ and graphite in the ratio of 1:3.

Abstract: SiO₂ compound was introduced into zinc ferrite using formula (1-x)ZnFe₂O₄ – xSiO₂ synthesized by sol-gel method where distilled water and citric acid was used as a solvent and binder agent. The produced samples were annealed at 450 °C for 1h. The AFM result analysis show that the average surface roughness and particle size decreased as the compositions of x was increased. XRD results analysis confirmed the formation of spinel structures with crystallite size within range 11.27 – 4.72 nm. UV-Vis analysis to determine the energy band gap of the (1-x)ZnFe₂O₄ – xSiO₂ samples. It shows that the energy band gap increased as the composition of SiO₂ was increased due to the dielectric properties of silicon dioxide. FTIR results analysis exhibit common band in the range of 400 – 4000 cm^-1. The observed band near 2350 cm^-1 shows the presence of oxygen-oxygen bond in the face centered cubic (fcc) crystal lattice of oxygen atoms. The addition of SiO₂ into ZnFe₂O₄ will help to enhance the morphological structures and optical properties. This new proposed dielectric material can be used as dielectric substrate microstrip patch antenna.

Abstract: Zinc aluminate (ZnAl₂O₄) and zinc ferrite (ZnFe₂O₄) nanocrystalline structures dispersed into SiO₂ matrix were prepared by sol-gel method. Phase formation of ZnAl₂O₄ and ZnFe₂O₄ was confirmed by X-ray diffraction (XRD) analysis. The crystallite sizes was determine using Scherer’s equation from the broadening of dominant peak at (311) plane. It was found the crystallite size of both compound decreased due to the decrement compositions of Zn²⁺ ion and Al³⁺ / Fe³⁺ ions. The crystallite sizes for ZnAl₂O₄ and ZnFe₂O₄ was calculated to be around ~ 14.16 – 11.27 nm and ~ 11.27 – 4.72 nm, respectively. FTIR analysis was done to determine the formation of spinel structures. FTIR results analysis confirmed that the formation of spinel structure where it has been observed that the bands around 800 cm^-1 was associated to the vibrations of aluminum-oxygen and metal-oxygen-aluminum bonds. This characteristic was identified to the formation of zinc aluminate spinel structure. The optical properties have been done to determine the energy bandgap of ZnAl₂O₄ and ZnFe₂O₄ samples. The Uv-Visible absorption spectra have been done within wavelength 300 – 800 nm and the graph was plotted into the Tauc plot. This new dielectric material was purposed to improve the value of dielectric permittivity with addition of SiO₂ where it can be applied as microwave dielectric material without changing the original spinel structures.

Abstract: Varistor with TiO₂ as the base and SiO₂, WO₃ and Bi₂O₃ as dopants were investigated to create a low voltage varistor. The physical, mechanical, microstructural and electrical properties were studied where the concentration of SiO₂ was varied but the concentration of WO₃ and Bi₂O₃ was fixed. Physical and mechanical characterization consisted of green and fired density, axial and radial shrinkage and Vickers Hardness. Electrical evaluation on the other hand consisted of non-linear coefficient, breakdown voltage, power loss and clamping ratio. Non-linear coefficient of 2.16, very low breakdown voltage of 5.538V/cm and minimal power loss of 0.0124mW was achieved. It was found that optimum results were achieved with 98.3% TiO₂, 0.7% SiO₂, 0.5%Bi₂O₃ and 0.5%WO₃.