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Characterization of magnetic biochar amended with silicon dioxide prepared at high temperature calcination

Abstract

Calcination is considered to increase the hardness of composite material and prevent its breakage for the effective applications in environmental remediation. In this study, magnetic biochar amended with silicon dioxide was calcined at high temperature under nitrogen environment and characterized using various techniques. X-ray diffraction (XRD) analysis revealed elimination of Fe3O4 peaks under nitrogen calcination and formation of Fe3Si and iron as major constituents of magnetic biochar-SiO2 composite, which demonstrated its superparamagnetic behavior (>80 A2·kg−1) comparable to magnetic biochar. Thermogravimetric analysis (TGA) revealed that both calcined samples generated higher residual mass (>96 %) and demonstrated better thermal stability. The presence of various bands in Fourier transform infrared spectroscopy (FT-IR) was more obvious and the elimination of H–O–H bonding was observed at high temperature calcination. In addition, scanning electron microscopy (SEM) images revealed certain morphological variation among the samples and the presence of more prominent internal and external pores, which then judged the surface area and pore volume of samples. Findings from this study suggests that the selective calcination process could cause useful changes in the material composites and can be effectively employed in environmental remediation measures.

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Agglomeration of Silicon Dioxide Nanoscale Colloids in Chemical Mechanical Polishing Wastewater: Influence of pH and Coagulant Concentration

Abstract

Chemical mechanical polishing (CMP) wastewater generated from semiconductor manufacturing industries is known to contain residual organic and inorganic contaminants, i.e. photoresists, acids, including silicon dioxide (SiO2), nanoparticles (NPs) and others. Nanoscale colloids in CMP wastewater have strong inclination to remain in the suspension, leading to high turbidity and chemical oxygen demand (COD). Although various types of pre-treatment have been implemented, these nanoparticles remain diffused in small clusters that pass through the treatment system. Therefore, it is crucial to select suitable pH and coagulant type in the coagulation treatment process. In this research zeta potential and dynamic light scattering measurements are applied as preliminary step aimed at determining optimum pH and coagulant dosage range based on the observation of inter particle-particle behavior in a CMP suspension. The first phase of the conducted study is to analyze nanoscale colloids in the CMP suspension in terms of zeta potential and z-average particle size as a function of pH within a range of 2 to 12. Two types of coagulants were investigated - polyaluminum chloride (PACl) and ferrous sulfate heptahydrate (FeSO4·7H2O). Similar pH analysis was conducted for the coagulants with the same pH range separately. The second phase of the study involved evaluating the interaction between nanoscale colloids and coagulants in the suspension. The dynamics of zeta potential and corresponding particle size were observed as a function of coagulant concentration. Results indicated that CMP wastewater is negatively charged, with average zeta potential of -59.8 mV and 149 d.nm at pH value of 8.7. The interaction between CMP wastewater and PACl showed that positively charged PACl rapidly adsorbed colloids in the wastewater, reducing the negative surface charge of nanoscale clusters. The interaction between CMP wastewater and FeSO4·7H2O showed that larger dosage is required to aggregate nanoscale clusters, due to its low positive value to counter negative charges of CMP wastewater.

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Combined Effects of 50 Hz Electromagnetic Field and SiO2 Nanoparticles on Oxidative Stress in Plant’s Gametic Cells / Zemfrekvences (50 Hz) Elekromagnētiskā Lauka Un SiO2 Nanodaļiņu Kombinētā Ietekme Uz Augu Gametisko Šūnu Oksidatīvo Stresu

Abstract

The paper presents the results of combined effects of an extremely low frequency electromagnetic field (50 Hz) (ELF EMF) and SiO2 nanoparticles on fluorescence of plant gametic cells (immature microspores). The data were recorded by a BD FACSJazz® cell sorter after cell irradiation by blue laser (488 nm). A significant difference of fluorescence was observed between gametic cells after 1 hour incubation in suspension of SiO2 nanoparticles and the control gametic cells. It was observed that fluorescence intensity of gametic cell was higher with ELF EMF treatment in comparison to control cells, but it was statistically significant only for cells treated with electromagnetic radiation field with density 100 μT (ρ < 0.01) and 400 μT (ρ < 0.01). A different effect of ELF EMF were observed in cells incubated in SiO2 nanoparticle suspension; interaction of the factors resulted in lower cell fluorescence in comparison to control cells. The present study showed that SiO2 nanoparticles may be a source of oxidative stress, but jointly with 50 Hz electromagnetic field they can serve as an efficient antioxidant

Open access
Determination of growth kinetics and size dependent structural, morphological, optical characteristics of sol-gel derived silica nanoparticles in silica matrix

Abstract

Nanocomposite silica thin films made using the sol-gel method were studied. The nano-silica films were prepared using a mixture of tetraethyl orthosilicate (TEOS), deionized water, ethanol, and ammonia solution. To control the growth of the particles inside the film, the nanocomposite silica film was prepared using a mixture of the nano-silica sol and the silica sol. The change in the particle size with the heat treatment temperature ranging from 450 °C to 1100 °C was investigated. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), NKD (refractive index-N, extinction coefficient-K, and thickness-D) and ultraviolet-visible (UV-Vis) spectrophotometry were used for characterization purposes. The XRD studies showed that the nano-silica thin films were amorphous at all annealing temperatures except for 1100 °C. The_-cristobalite crystal structure formed at the annealing temperature of 1100 °C. Optical parameters, such as refractive indices and extinction coefficients, were obtained using the NKD analyzer with respect to the annealing temperature of the films. The activation energy and enthalpy of the nanocomposite silica film were evaluated as 22.3 kJ/mol and 14.7 kJ/mol, respectively. The cut-off wavelength values were calculated by means of extrapolation of the absorbance spectra estimated using the UV-Vis spectroscopy measurements. A red shift in the absorption threshold of the nanocomposite silica films indicated that the size of the silica nanoparticles increased with an increase of the annealing temperatures from 450 °C to 900 °C, and this confirms the quantum confinement effect in the nanoparticles.

Open access
Application of Aloe vera gel instead of silicon dioxide as organic dielectric material in microelectronics

Abstract

Organic materials are now being used in a wide range of microelectronic applications in parallel with inorganic materials, because of their superior properties, environmental safety, and low cost. This paper describes the characterization of Aloe vera gel (AVG), a new organic dielectric material. The surface morphology, spatial distribution of elements, and structural characteristics of an AVG layer were examined using scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD), respectively. The resistance of the AVG layer, determined using a four-probe station, was 640 Ω EDX showed that the elements contained in the layer were carbon, oxygen, aluminum, silicon, calcium, potassium, and copper. The XRD results suggested that the sample primarily consisted of bornite (Cu5FeS4), geerite (Cu8S5), sal ammoniac (NH4Cl), and carobbite (KF).

Open access
Evaluation of Genetic Damage in Oreochromis mossambicus Exposed to Selected Nanoparticles by Using Micronucleus and Comet Bioassays

.C. (2017b): Assessment of acute toxicity (LC 50 96 h) of aluminium oxide, silicon dioxide and titanium dioxide nanoparticles on the freshwater fish, Oreochromis mossambicus (Peters, 1852). International Journal of Fisheries and Aquatic Studies. 5, 1, 327-332. Vidya, P.V., Chitra, K.C. (2018a): Aluminium oxide nanoparticles induced irreversible alterations in the antioxidant defense system of the fish, Oreochromis mossambicus (Peters, 1852). European Journal of Biomedical and Pharmaceutical Sciences. 5, 2, 1162-1170. Vidya, P.V., Chitra, K.C. (2018b

Open access
Effect of nano-silicon foliar application on safflower growth under organic and inorganic fertilizer regimes

., H en Y., L eshem Y., L andau Y.S., B rukenta l I., 2002: A note on ensiling safflower forage. – Grass and Forage Science, 57(2): 184–187. X ie Y., L i B., Z hang Q., Z hang C., 2012: Effects of nano-silicon dioxide on photosynthetic fluorescence characteristics of Indocalamus barbatus McClure. – Journal of Nanjing Forestry University (Natural Science Edition), 2: 59–63. X ie Y., N iu J., G an Y., G ao Y., L i A., 2014: Optimizing phosphorus fertilization promotes dry matter accumulation and P remobilization in oilseed flax. – Crop Science

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Deposition of gold nanoparticles from colloid on TiO2 surface

Abstract

In this paper, experimental results are presented on the deposition of colloidal gold nanoparticles on the surfaces of TiO2 prepared on silicon/silicon dioxide. Important procedures, such as titanium dioxide surface hydrophilization as well as functionalization by an organosilane coupling agent (3-aminopropyl) trimethoxysilane and (3-mercaptopropyl) trimethoxysilane were investigated in order to obtain a metal oxide surface with the most convenient properties for immobilization of gold nanoparticles having a dense and uniform distribution. TiO2 nanotips prepared by reactive ion etching of oxide surface covered with self-mask gold nanoparticles are demonstrated.

Open access
Pulmonary silicotuberculosis in an electrician male - Case report and literature review

Abstract

This is a case report of a pulmonary silicotuberculosis in a former smoker, male, 43 years old, having 21 years of occupational exposure to particulate coniotic-free crystalline-silicon dioxide as an electrician, developing symptoms as fever higher than 38°C, dry cough and diffuse chest pain, being diagnosed with miliary of the lung in 2002. Silicosis was confirmed later by histological exam obtained through an exploratory thoracotomy and it was included in the transient first to second stage of pneumoconiosis. Three years later, in July 2005, Pulmonary Tuberculosis was diagnosed by acid-fast stains positive smears. The evolution of the case was to a progressive deterioration till 2008, leading to silicosis stage III. Silicosis is a pulmonary fibrosis which must be always suspected in persons working in conditions of occupational exposure to dust of silicon dioxide, having suggestive radiological changes including micronodular radiological pattern or pseudotumoral one. Once the diagnosis of silicosis is confirmed, tuberculosis may be frequently associated. The more advanced silicosis is, the more the combination of the two diseases is commonly revealing and, often, the TB morbidity among workers in the silica industry exceeds that of general population. A hint orientation for the silicotuberculosis’ diagnosis, in this reported case, was represented by the radiological dynamic of the lesions. Tuberculosis lesions are less dense and imprecisely defined, located in upper lobes and develop necrotic centers.

Open access
Influence of dielectric coverage on photovoltaic conversion of silicon solar cells obtained by epitaxial lateral overgrowth

Abstract

This work presents an analysis of the influence of SiO2 dielectric coverage of a Si substrate on the solar-cell efficiency of Si thin layers obtained by epitaxial lateral overgrowth (ELO). The layers were obtained by liquid phase epitaxy (LPE). All experiments were carried out under the following conditions: initial temperature of growth: 1193 K; temperature difference ΔT = 60 K; ambient gas: Ar; metallic solvent: Sn+Al; cooling rates: 0.5 K/min and 1 K/min. To compare the influence of the interior reflectivity of photons, we used two types of dielectric masks in a shape of a grid etched in SiO2 along the 〈110〉 and 〈112〉 directions on a p+ boron-doped (111) silicon substrate, where silicon dioxide covered 70 % and 80 % of the silicon surface, respectively. The results obtained in this work depict the correlation between the interior efficiency and percentage of SiO2 coverage of the substrate of the ELO solar cells.

Open access