Pure Silicon Dioxide Research Articles

Characterization of algerian desert sand as a raw material for solar-grade silicon production

The transition from fossil to clean power requires pure materials and technology. Silicon has semiconductor properties, it is the most important element in producing solar panels for electrical production, the high amount of pure silicon dioxide in the sand makes it a good raw material, economically rentable, and fewer procedures to refine it. The southwest of Algeria which has a hot, dry climate is categorized as a desert, representing an important reservoir of sunlight and an abundance of dunes, to explore and valorization of the potential of sand in this region as a raw material for solar-grade silicon production, the sand sample was gathered from Adrar province. Conventional physical and chemical characterization methods used to determine the nature and amount of existing oxides: X-ray diffraction, X-ray fluorescence to determine the rate of silicon dioxide existing in the sample, microscopy, and sieve analysis to find the shape of the grain. The results show that the ADRAR deposit has significant-quality silica sand due to its considerable silicon dioxide (SiO2) content, reaching 96%. However, it still requires extra mechanical and chemical processing, rendering it a valuable raw resource for the renewable energy industry.

SYNTHESIS AND CHARACTERIZATION OF PURE AMORPHOUS SILICON OXIDE FROM TREATED KAOLINITIC CLAY USING CHEMICAL EXTRACTION

Pure silicon oxide was produced in this study utilizing a sodium silicate solution made from Kankara clay as a precursor. The Kankara clay that was obtained from Nigeria was first beneficiated to produce pure dried powder clay. After that, the dried powdered clay was treated with heat activation and acid leaching, respectively. In a 500 mL Erlenmeyer flask, appropriate amounts of each clay (raw, thermally treated clay, and leached clay) were reacted with 3M NaOH solution. The flask was heated to 200°C and stirred continuously for 3 hours on a magnetic stirring hot plate connected to a reflux condenser. The solution was filtered to yield sodium silicate solution, which was then precipitated with 3M HCl while constantly stirring to produce a gelly-like white substance. The gel was aged for 18 hours, then washed with de-ionized water several times before being dried at 80°C for 12 hours to get pure white silica particles, which were subsequently described. The XRD analysis revealed that the silicon oxide synthesized is amorphous, but the microstructure evaluation revealed particles aggregation, which is usual in sol-gel synthesized powder.

High-temperature resistant, low dielectric SiO2@Quartz fiber composites for high fidelity communication cables

High-fidelity communication in extreme environments has attracted significant attention due to its potential applications in aerospace, polar, deep-sea exploration, fire rescue, and nuclear industries. Yet, challenges persist in constructing dielectric layers with both low dielectric constant and high-temperature stability in communication cables. Herein, low-dielectric inorganic composites utilizing pure silicon oxide (SiO2) are employed as a substitute for conventional organic materials or their composites. By incorporating the in-situ growth of SiO2 microspheres (m-SiO2) on the quartz fiber structure, the composites exhibit a reduced dielectric constant while improving mechanical performance. The flexural stress of the m-SiO2@quartz fiber composites is twice as high as that of the composites prepared by the ex-situ synthesis method. Furthermore, the m-SiO2@quartz fiber composites display high-temperature resistance up to 800 °C with a mass loss less than 1 %. With 30 wt% of quartz fibers, 20 nm of m-SiO2, and 6 wt% of the foaming agent, the composites exhibit a dielectric constant of 1.95. Based on the low-dielectric m-SiO2@quartz fiber composites, the cable demonstrates a voltage standing wave ratio (VSWR) of 1.46, an attenuation of 1.22 dB, and a characteristic impedance of 48 Ω.

Silica particles convert thiol-containing molecules to disulfides

Synthetic amorphous silica is a common food additive and a popular cosmetic ingredient. Mesoporous silica particles are also widely studied for their potential use in drug delivery and imaging applications because of their unique properties, such as tunable pore sizes, large surfaces areas, and assumed biocompatibility. Such a nanomaterial, when consisting of pure silicon dioxide, is generally considered to be chemically inert, but in this study, we showed that oxidation yields for different compounds were facilitated by simply incubating aqueous solutions with pure silica particles. Three thiol-containing molecules, L-cysteine, glutathione, and D-penicillamine, were studied separately, and it was found that more than 95% of oxidation happened after incubating any of these compounds with mesoporous silica particles in the dark for a day at room temperature. Oxidation increased over incubation time, and more oxidation was found for particles having larger surface areas. For nonporous silica particles at submicron ranges, yields of oxidation were different based on the structures of molecules, correlating with steric hindrance while accessing surfaces. We propose that the silyloxy radical (SiO•) on silica surfaces is what facilitates oxidation. Density functional theory calculations were conducted for total energy changes for reactions between different aqueous species and silicon dioxide surfaces. These calculations identified two most plausible pathways of the lowest energy to generate SiO• radicals from water radical cations H2O•+ and hydroxyl radicals •OH, previously known to exist at water interfaces.

Investigation of optical properties and radioactive attenuation parameters of doped tungsten oxide soda lime silica SLS waste glass

The optical properties and radioactive attenuation parameters of doped tungsten oxide soda-lime-silica (SLS) waste glass were investigated in the current work. A novel series of lead-free transparent glass samples were manufactured with the possibility of developing radiation-absorbing glass shielding materials. The glass composition is WO3–Bi2O3–ZnO–B2O3-SLS. A new approach was employed in the utilization of soda-lime-silica (SLS) glass as an alternative for pure silicon dioxide having 74.1% of SiO2 and other elements in it. The optical properties were investigated with the help of a UV–Visible Spectrophotometer. The results for the optical properties showed that when WO3 content is increased in the glass structure, the Urbach energy ΔE and refractive index n, increase from 0.337 to 0.431 and 2.84 to 2.94 respectively, the optical basicity Λ also increase with the increase in WO3 while the energy optical band gap Eopt registered a decrease. The metallization criterion (M) confirmed that the current glass samples are nonmetallic (insulator) because Rm/Vm < 1 which is confirmed in the condensed matter theory in the Lorentz–Lorenz equations. Moreover, the theoretical radiation shielding parameter results indicate that the linear attenuation coefficient μ and Zeff were increased with an increase in WO3. It can be seen also that the relationship between the μ and HVL is an inverse one; larger values of μ result in lesser thickness of the HVL. Whereas, as the WO3 concentration increases, the half-value layer HVL decreases. The results of this study demonstrate that the glass samples are harmless, transparent to visible light, and effective radiation shielding materials.

Structure and properties of silicon nano- and microparticles obtained by electric-spark dispersion method

Silicon nano- and microparticles obtained using electric-spark dispersion of silicon electrodes and granules in 40 wt% solution of methyl alcohol in water were investigated by ultrasoft X-ray emission spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning and transmission electron microscopies. In addition, the SiLα spectra of obtained silicon particles were modeled by superimposing the spectra of pure silicon and silicon oxide taken in certain weight ratios. It was found that the surfaces of Si nano- and microparticles obtained in 40 wt% solution of methyl alcohol in water are covered with silicon oxide and chemisorbents, while the core consists of crystalline silicon with a cubic face-centered lattice. The silicon nano- and microparticles show potential as an anode material to replace commonly used graphite electrodes. The charge capacity of the electrode based on mixture of Si nano- and microparticles with graphite powder was about 1272 mAh/g after ten cycles.

Production of Amorphous Silicon Dioxide Derived from Aluminum Fluoride Industrial Waste and Consideration of the Possibility of Its Use as Al2O3-SiO2 Catalyst Supports

This paper presents the results of the study on the development of a methodology for the production of pure amorphous silicon dioxide containing up to 99.8 wt.% of SiO2. As a starting material, a silica gel with a moisture content of up to 55 wt.% and an SiO2/AlF3 ratio of 4 was used. The silica gel was purified using alkaline and acidic solutions in concentrations ranging from 0.1 to 25 wt.%. The analysis of the experimental data allowed to identify the most suitable purification parameters of the starting material. The initial silica gel and the reaction products were studied using the methods of X-ray fluorescence, X-ray phase analysis, electron scanning microscopy, EDS microanalysis, and particle-size analysis. Amorphous silicon dioxide obtained according to the methodology developed by the authors forms agglomerates of spherical silicon dioxide particles up to 1 μm in size. Amorphous silicon dioxide was involved in the preparation of catalyst supports in order to consider the possibility of replacing part of the expensive raw material in the form of aluminum hydroxide. In the work, the characteristics of the addition of this amorphous silicon dioxide and the supports obtained from the traditionally used raw materials were evaluated.

Осаждение планарных волноведущих структур со фторсиликатной оболочкой на кремниевые и кварцевые подложки в локальном СВЧ-разряде пониженного давления.

An efficient method of gas-phase multilayer heterogeneous deposition of quartz and fluorosilicate glass in a non-isothermal plasma of a resonant local low pressure microwave discharge on quartz glass substrates and silicon wafers for the optical structures formation of waveguides and other waveguide elements based on them, is presented. It is shown that the nonisothermal plasma of a resonant local low pressure microwave discharge is an effective tool for the films formation on silicon and quartz substrates, both pure silicon dioxide and doped with fluorine. The cracks presence in films doped with fluorine is not observed even at their considerable thicknesses (20…60 µm). Deposition high rates and efficiency of silica glass doped with fluorine have been achieved (up to 7 wt.% of glass doping with fluorine at a film deposition rate of more than 3 μm/min). Planar and strip multimode and single-mode optical waveguides have been created. They are the basic structures of various fiber-optic components of local information transmission systems.

Synthesis and characterization of SrO-containing bioglass-ceramic from rice husk silicon dioxide

Abstract Rice husk is an abundant waste at the Rio Grande do Sul, Brazil, and it can be used to produce pure silicon dioxide, which is the main component of bioglass-ceramics. The addition of compounds, such as SrO, can improve the biocompatibility of these biomaterials. Therefore, the goal of this paper was to use rice husk silicon dioxide as a cheap precursor to obtaining bioglass-ceramics of the system 50%SiO2-25%Na2O-(25-x)%CaO-x%SrO (mol%) by sol-gel and investigate its potential use as a biomaterial. Two samples (BGC blank and BGC-5%Sr) were synthesized and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and elemental carbon analysis by the combustion method. Scanning electron microscopy (SEM) was used to investigate the morphology of the bioglass-ceramics, while MTT assay of cell viability was used for in vitro characterization. The obtained silicon dioxide was amorphous and presented a small carbon content. Also, the bioglass-ceramics showed main phases with Si, Ca, Na, and Sr on their structure. Both samples were not cytotoxic against peripheral blood mononuclear cells (PBMC), and the incorporation of 5% SrO improved biocompatibility.

Sir Charles Kuen Kao. 4 November 1933—23 September 2018

Charles Kao was the pioneer who suggested using glass fibre waveguide as a means of carrying laser-light over long distances for telecommunications traffic. In his seminal paper published in 1966, he spelled out the appropriate design parameters and performance characteristics that would be needed for a successful system to emerge. At the time, the idea was widely ridiculed. Within a few years, however, in a brilliant set of spectrophotometric experiments, Kao demonstrated that pure silicon dioxide materials exist that have the required very low attenuation. In due course, the problems of creating optical fibres of the required dimensions and strength were solved and optical fibres now dominate telecommunications worldwide. Without them, contemporary communications would be unthinkable. Kao was awarded the 2009 Nobel Prize in Physics for his ‘groundbreaking achievements concerning the transmission of light in fibres for optical communication’.

Analysis and characterization of SiO2 nanowires via electrospinning technique

The aim of the study was the production of ceramic SiO2 nanowires using the sol-gel and electrospinning methods from solution of PVP/TEOS/AcOH/EtOH. The obtained fibrous mats was subjected to preliminary drying at room temperature and next was subjected the calcination process in air to obtain pure amorphous silicon dioxide nanowires. Analysis of the morphology and chemical composition of the resulting nanowires was carried out using a scanning electron microscope (SEM) with energy dispersive spectrometer (EDS). In order to analyze the structure of the obtained materials were used high-resolution transmission electron microscope (TEM) and X-ray diffraction analysis (XRD). The analysis of the optical properties and the energy band gap of prepared nanowires was determined by spectral analysis of the absorbance in the function of the energy of radiation obtained using a UV-Vis spectrophotometer

Analysis of the morphology, structure and optical properties of 1D SiO2 nanostructures obtained with sol-gel and electrospinning methods

Abstract The aim of the study was the production of ceramic SiO2 nanowires using the sol-gel and electrospinning methods from a PVP/TEOS/AcOH/EtOH solution. The obtained fibrous mats underwent preliminary drying at room temperature. Then, they were subjected to the calcination process in air to obtain pure amorphous silicon dioxide nanowires. A scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) was used in order to carry out an analysis of the morphology and chemical composition of the resulting nanowires. A high-resolution transmission electron microscope (TEM) was used along with X-ray diffraction analysis (XRD) in order to analyse the structure of the obtained materials. Besides, thermogravimetric analysis (TGA) was performed to show polymer concentration loss in the function of temperature in the obtained two types of PVP/SiO2 nanofibers. The analysis of the optical properties and the energy band gap of the prepared nanowires was determined by spectral analysis using a UV–Vis spectrophotometer. Using the method proposed by the authors and the recorded absorbance spectra determined the banded refractive index n, real n′ and imaginary k part of the refractive index as a function of the wavelength, complex dielectric constant e, real and imaginary part er and ei of the dielectric constant as a function of the wavelength of the SiO2 nanowires. The obtained results, which were as follows: energy band gap of 3.93–3.97 eV, complex refractive index coefficient values of 1.52–1.65 and dielectric constant in the range of 2.30–2.73, suggest the possibility to control the morphology and optical properties of the produced nanomaterial.

Machining and Characterization of Channels and Textures on Quartz Glass Using μ-ECDM Process

Applications of various glass materials like sodalime, borosilicate and pyrex are growing in the field of micro-electro mechanical systems. Quartz glass composes of pure silicon dioxide which is well- known for its hardness and processing of it would widen the scope of its application in product miniaturization. Micro-Electro Chemical Discharge Machining (μ-ECDM) is a non-conventional hybrid technique which combines the features of Electro Chemical Machining (ECM) and Electro Discharge Machining (EDM). In the present paper, channels are machined using μ-ECDM on 4 mm thick quartz glass with 370 μm diameter stainless steel (SS) tool. Experiments are designed at various levels of voltage (V), electrolyte concentration (wt%C) and duty factor (%DF) for parametric study. Signal to Noise (S/N) ratio and Grey Relational Analysis (GRA) are used to optimize the process parameters to enhance responses individually and simultaneously. The obtained S/N ratio optimized parameters to maximize Material Removal Rate (MRR) are - 60 V, 30 wt%C, 60 %DF resulted in 753 μg/min, to minimize Tool Wear Rate (TWR) are – 40 V, 20 wt%C, 50 %DF resulted in 2.99 μg/min and to minimize width of the channel are- 40 V, 20 wt%C, 60 %DF resulted in 500 μm. The GRA optimized parameters are- 40 V, 20 wt%C and 50 %DF resulting in 81 μg/m of MRR, 2.99 μg/m of TWR and 557.6 μm of width with entropy technique- equal weightage. Further an attempt has been made to machine texture on the quartz surface which is still in its early stages of research. GRA optimized parameters as detailed above are used to machine channels and generate textures of 45° hatch, square hatch and 45° criss-cross hatch on quartz glass.

Ловушки в нанокомпозитном слое кремний-диоксид кремния и их влияние на люминесцентные свойства

The traps in thermal films of silicon dioxide and silicon dioxide with a nanocomposite layer on the surface were investigated by Kelvin-probe microscopy and cathode luminescence. In the layers, both electron traps and hole traps are observed. The effect of the charge state of electron traps on the luminescent properties of films is demonstrated. It is shown that in the presence of a nanocomposite layer in silicon dioxide films, the number of electron traps increases, but their activation energy remains close to the activation energy of traps in pure silicon dioxide, which suggests that the nature of the traps in such layers is similar.

Absence of free carriers in silicon nanocrystals grown from phosphorus- and boron-doped silicon-rich oxide and oxynitride.

Phosphorus- and boron-doped silicon nanocrystals (Si NCs) embedded in silicon oxide matrix can be fabricated by plasma-enhanced chemical vapour deposition (PECVD). Conventionally, SiH4 and N2O are used as precursor gasses, which inevitably leads to the incorporation of ≈10 atom % nitrogen, rendering the matrix a silicon oxynitride. Alternatively, SiH4 and O2 can be used, which allows for completely N-free silicon oxide. In this work, we investigate the properties of B- and P-incorporating Si NCs embedded in pure silicon oxide compared to silicon oxynitride by atom probe tomography (APT), low-temperature photoluminescence (PL), transient transmission (TT), and current–voltage (I–V) measurements. The results clearly show that no free carriers, neither from P- nor from B-doping, exist in the Si NCs, although in some configurations charge carriers can be generated by electric field ionization. The absence of free carriers in Si NCs ≤5 nm in diameter despite the presence of P- or B-atoms has severe implications for future applications of conventional impurity doping of Si in sub-10 nm technology nodes.

Composition, Mixing State and Water Affinity of Meteoric Smoke Analogue Nanoparticles Produced in a Non-Thermal Microwave Plasma Source

Abstract The article reports on the composition, mixing state and water affinity of iron silicate particles which were produced in a non-thermal low-pressure microwave plasma reactor. The particles are intended to be used as meteoric smoke particle analogues. We used the organometallic precursors ferrocene (Fe(C5H5)2) and tetraethyl orthosilicate (TEOS, Si(OC2H5)4) in various mixing ratios to produce nanoparticles with radii between 1 nm and 4 nm. The nanoparticles were deposited on sample grids and their stoichiometric composition was analyzed in an electron microscope using energy dispersive X-ray spectroscopy (EDS). We show that the pure silicon oxide and iron oxide particles consist of SiO2 and Fe2O3, respectively. For Fe:(Fe+Si) ratios between 0.2 and 0.8 our reactor produces (in contrast to other particle sources) mixed iron silicates with a stoichiometric composition according to FexSi(1−x)O3 (0≤x≤1). This indicates that the particles are formed by polymerization of FeO3 and SiO3 and that rearrangement to the more stable silicates ferrosilite (FeSiO3) and fayalite (Fe2SiO4) does not occur at these conditions. To investigate the internal mixing state of the particles, the H2O surface desorption energy of the particles was measured. We found that the nanoparticles are internally mixed and that differential coating resulting in a core-shell structure does not occur.

SiGe-on-insulator fabricated via germanium condensation following high-fluence Ge+ ion implantation

Germanium condensation is demonstrated using a two-step wet oxidation of germanium implanted Silicon-On-Insulator (SOI). Samples of 220 nm thick SOI are implanted with a nominal fluence of 5 × 1016 cm−2 Ge+ at an energy of 33 keV. Primary post-implantation wet oxidation is performed initially at 870 °C for 70 min, with the aim of capping the sample without causing significant dose loss via Ge evaporation through the sample surface. This is followed by a secondary higher temperature wet oxidation at either 900 °C, 1000 °C, or 1080 °C. The germanium retained dose and concentration profile, and the oxide thickness is examined after primary oxidation, and various secondary oxidation times, using Rutherford backscattering analysis. A mixed SiGe oxide is observed to form during the primary oxidation followed by a pure silicon oxide after higher temperature secondary oxidation. The peak germanium concentration, which varies with secondary oxidation condition, is found to range from 43 at. % to 95 at. %, while the FWHM of the Ge profile varies from 13 to 5 nm, respectively. It is also observed that both the diffusion of germanium and the rate of oxidation are enhanced at 870 and 900 °C compared to equilibrium expectations. Transmission electron microscopy of a representative sample with secondary oxidation at 1080 °C for 20 min shows that the SiGe layer is crystalline in nature and seeded from the underlying silicon. Raman spectroscopy is used to determine residual strain in the SiGe region following secondary oxidation. The strain is compressive in nature and increases with Ge concentration to a maximum of approximately 1% in the samples probed. In order to elucidate the physical mechanisms, which govern the implantation-condensation process, we fit the experimental profiles of the samples with a model that uses a modified segregation boundary condition; a modified linear rate constant for the oxidation; and an enhanced diffusion coefficient of germanium where the enhancement is inversely proportional to the temperature and decays with increasing time. Comparison of the modeled and experimental results shows reasonable agreement and allows conclusions to be made regarding the dominant physical mechanisms, despite the semi-empirical nature of the model used.

Optical, structural, and mechanical properties of silicon oxynitride films prepared by pulsed magnetron sputtering.

Silicon oxynitride films were deposited by reactive pulsed magnetron sputtering. The optical, structural, and mechanical properties of silicon oxynitride films with different nitrogen proportions were analyzed via spectroscopy, atomic force microscopy, Twyman-Green interferometer, and nanoindentation. The refractive indices of the silicon oxynitride films were adjusted from 1.487 to 1.956 with the increase in nitrogen proportions. The surface roughness decreased from 1.33 to 0.97nm with the increase in nitrogen proportions. The residual stress of the silicon oxynitride films was higher than for pure silicon nitride and silicon dioxide films. The hardness and Young's modulus increased from 13.51 to 19.74GPa and 110.41 to 140.49GPa with the increase in nitrogen proportions, respectively. The hardness and Young's modulus of antireflection coatings using silicon oxynitride film were 13.64GPa and 102.11GPa, respectively. Silicon oxynitride film could be used to improve the hardness of antireflective coatings.

Silicon Crystals Formation Using Silicatein-Like Cathepsin of Marine Sponge &lt;I&gt;Latrunculia oparinae&lt;/I&gt;

The cDNA fragment encoding the catalytic domain of the new silicatein-like cathepsin enzyme LoCath was expressed in a strain Top10 of Escherichia coli, extracted and purified via nickel-affinity chromatography. Recombinant enzyme performed silica-polymerizing activity when mixed with water-soluble silica precursor-tetrakis-(2-hydroxyethyl)-orthosilicate. Scanning electron microscopy revealed hexagonal, octahedral and β-tridimit crystals. Energy dispersion fluorescence X-ray spectrometry analysis showed that all these crystals consist of pure silicon oxide. It is the first report about the ability of marine sponge's cathepsin to polymerize silicon, as well as about the structure and composition of the silicon oxide crystal formed by recombinant cathepsin. Further study of the catalytic activity of silicatein and cathepsin will help to understand the biosilification processes in vivo, and will create basis for biotechnological use of recombinant proteins for silicon polymerization.

Silicon sensitisation using light harvesting layers

Langmuir–Blodgett monolayers of a cyanine dye mixed with stearic acid were deposited on glass and silicon substrates with spacer layers of pure stearic acid monolayers or silicon dioxide films deposited by PECVD. By using the time correlated single photon counting technique, time resolved emission spectra (TRES) and decay curves were measured to characterise the dependence of energy transfer rate on the separation between the dye monolayer and the silicon surface and also for the dye concentrations in the monolayers. We observe interlayer energy transfer between monomers, dimers and higher aggregates present in the monolayer deposited on glass but also competing directly with energy transfer to silicon at close distances. We find that the fluorescence lifetime of the dye monolayer is significantly shortened when deposited close to the silicon surface signifying efficient energy transfer. The dissipation of the excitation energy near silicon is explained using the classical theory developed for metals and a deviation is observed for monolayers deposited at distances close to the silicon surface.