Journal of Nano Research Vol. 26

Abstract: Fine SiO₂ nanosphericals (2-5nm) and new various stable nanofluids including Tween 80, Span 80, Lauric alcohol-3EO, CTAB, SDS and K-Laurate surfactants in water or paraffin based solution were used as new SiO₂ nanoproducts in oil recovery. These nanofluids can strongly change oil-wet carbonate reservoir rock to complete water-wet wettability and showed an excellent trend of surface tension (S.T) and IFT (interfacial tension) reduction in comparison with pure water and reference solutions. The CaCO₃ plates reservoir was then aged for 2, 5 and 8 days into the 1, 3 and 8% of different concentrations of synthesized SiO₂ nanofluids (effect of various concentrations via different aging time). Air/water and n-decane/water contact angles on oil-wet and clean carbonate rock aged in designed SiO₂ nanofluids were measured and the pH value as a significant factor estimated. The interesting influence of microwave irradiation on surface tension and IFT including various SiO₂ nanofluids was investigated after 12 min which some of the especial nanofluid concentrations showed successful reduction. Our findings indicated the important effect of temperature over decreasing of surface tension and IFT between oil and water interface including SiO₂ nanofluids after annealing at 70°C. Therefore, this phenomenon can be significantly capable and valuable in applying of new technology in the fabrication of novel nanofluids in EOR processes and saving source of energy regarding to conventional production.

Abstract: ZnO nanosphericals and nanorods have interesting potential applications in various fields such as antibacterial and enhanced oil recovery process. In this work, it was shown that 30 ml of a water-based solution containing 3% of ZnO nanofluids could significantly change the wettability of a carbonate reservoir rock from a strongly oil-wet alter to a strongly water-wet condition, after 3 days aging of the rock at 70°C in the designed solution. Moreover, we have studied air-water and oil-water interfacial tensions of system containing nanofluids. Fluids included ZnO nanoparticles and quantum dots nanostructures (QDOTs ZnO) could effectively decrease the n-decane/water interfacial tension and air/water surface tension. So their efficiency is much higher in comparison with distilled water.The stabilization of various aqueous ZnO nanostructured in mixtures of NaCl, CaCl₂, MgCl₂ and Na₂SO₄ salts were investigated, and 50000-163000 ppm transparent and stable nanosalt fluids were fabricated. Wettability of an oil-wet carbonate rock aged for 3 days at 70°C in the designed ZnO nanosalt fluids was studied by measuring the contact angles. The results show a strong change in wettability of carbonate rocks from oil-wet to more water-wet condition. These nanosalt fluids performed an excellent trend of surface tension and IFT reduction in comparison with distilled water too.

Abstract: We are able to produce nanoscale rutile TiO₂ product from titanium mineral via a modified hydrothermal synthesis method, with the inclusion of an alkaline fusion stage. The mineral was totally dissolved in an acidic solution, and is followed by the nucleation reaction, producing anatase having a crystallite size of 15.4nm. Annealing of the nanoanatase resulted in a phase transformation process, and the rutile phase was detected when annealed at 800°C. Single rutile phase was achieved when the anatase sample was annealed at 1,000°C. As the starting mineral contains a significant amount of Nb and Zr impurities, these elements are naturally doped into the nanosized rutile. A paint formulation was then produced by adding 2g of this nanoanatase/nanorutile into the paint. Using this nanotitania added paint under visible light source, a photocatalytic study on the degradation of methylene blue was conducted. A comparative study was also carried out with commercial grade pure nanorutile under similar condition. The result showed that our nanorutile managed to degrade the methylene blue to almost a similar 85% degradation compared to the commercial pure nanoanatase. A pure nanorutile product resulted in a much lower photodegradation rate, standing at 77%. Tests on the photodegradation of nitrous oxide gas also reveals that the nanorutile paint was able to degrade the VOC in much shorter times compared to the other nanotitania added paints.

Abstract: In the present work, zirconia-based nanomaterials with various stabilizers were prepared by a co-precipitation technique. Defects in these nanomaterials were characterized by positron annihilation spectroscopy which is a non-destructive technique with a high sensitivity to open volume defects and atomic scale resolution. It was found that zirconia-based nanomaterials contain vacancies and also nanoscale and meso-scale pores. Diffusion processes which occur in the nanomaterials sintered at elevated temperatures were investigated by depth sensitive positron annihilation studies on a variable energy slow positron beam. It was found that sintering causes intensive grain growth and residual porosity is removed from samples by diffusion to the surface.

Abstract: Magnesium (Mg)-doped zinc oxides (ZnO) have been prepared on a silicon substrate by using the solution-immersion method. The nanorods films were annealed at different temperature 0°C, 250°C, 500°C respectively for 1 hour. The XRD diffraction indicated that the Mg-doped ZnO nanorods have good crystallinity with a hexagonal wurzite structure preferentially oriented along the (002) direction. PL spectroscopy at room temperature shows strong UV peaks appearing at 383 nm when annealed at 250°C. The intensity of broad emission peaks increases with increasing annealing temperature to 500°C which is possibility attributed to intrinsic defects.

Abstract: Synthesis of nanostructured ZnO by an environmentally-friendly method thus applying water as the major media is the aim in solution-immersion method. In this paper, the effect of three types of seeded template to the structural and optical properties of ZnO nanostructures grown by the Solution-Immersion method is investigated. The primary template is glass, seeded with three types of thin films i.e. TiO₂ by radio-frequency (RF) magnetron sputtering at 200 W (ZnO/TiO₂), a layer of PMMA by spin-coating (ZnO/PMMA) and ZnO grown by the mist-atomization method (ZnO/ZnO). The morphology and optical properties will be investigated by FESEM, PL and UV-Vis.

Abstract: To the best of our knowledge, this work presents the first successful effort to fabricate and study nanostructured Ni-based composite coatings using the electrophoretic deposition method with nanostructured SiO₂ particles. In this work, Ni/SiO₂ nanoparticle composite coatings were prepared by electrophoretic deposition (EPD) [ and their hardness, wear and corrosion resistances [ were examined. After studying the morphology of the coatings and finding the optimum conditions for uniform coating, in order to improve the mechanical properties as well as resistance to corrosion, sintering was performed. The Ni/SiO₂ nanocomposite coatings show excellent hardness (~376 HV), reduced Youngs modulus (~180 GPa), contact stiffness (~110 μN/Nm) as well as the wear and corrosion resistances which are considered in the different SiO₂ concentrations and particle sizes. In addition, by controlling the size of the SiO₂ particles, in optimum coating voltage and proper time duration, hardness and wear resistance of nanocomposite coatings were controlled.

Abstract: Friction stir processing (FSP) has been found as a promising method for surface modification of materials such as grain refinement and hardness increment. FSP is also widely used for fabrication of in situ micro-and nanocomposites on the surface of materials. In this research FSP is used for inserting the nanosized SiC particles into the copper matrix. Subsequently, 4-pass FSP is applied to obtain good dispersion of SiC particles in copper matrix leading to improve the mechanical properties of the fabricated composite. The optical microscopy and scanning electron microscopy are used for microstructural evaluation. Results show that an increase in the number of FSP passes considerably enhances the dispersion of the SiC particles in the stir zone and also breaks down the SiC particles. These phenomena lead to reduction of the grain size and improvement of mechanical properties in 4-pass composite compared to that of fabricated by 1-pass FSP.

Abstract: Amorphous Si/SiO₂ quantum wells have been obtained at room temperature with atomic precision using magnetron sputtering. The Si/SiO₂ layer structure induces the higher optical transmittance at the visible wavelength region with increasing layer numbers. The tentative absorption coefficients are evaluated for integrated Si thicknesses. The absorption edge energy dependency on Si layer thickness E₀ = 1.61 + 0.75d^-2 is in accordance with effective mass theory for thicknesses 0.5 < d < 6nm. Quantum confinement effects of the Si/SiO₂ nanostructure layer are confirmed from optical transmittance and reflectance spectra.