Abstract: Composites based on silica and glass fibers conventionally contain fibers with dimension in the range of a few micrometers to millimeters. Electrospinning technique allows fabrication of fibers in the submicron length scale. With smaller dimension, these fibers when applied as reinforcement in composites may yield interesting composite properties. In this paper, silica fibers fabricated via electrospinning were utilized as reinforcement in polypropylene-matrixed composites. The silica precursor was prepared by sol-gel reaction of tetraethyl orthosilicate, ethyl alcohol, de-ionized water and hydrochloric acid. Viscous silica precursor was made into fibers by electrospinning with electric field of 1 kV/cm. Electrospun non-woven fiber mats were stabilized at 200°C and calcined at 800°C to remove remaining organic residues. The fiber diameter average was 279±40 nm. In the process of making composites, the silica fiber mats were sandwiched between polypropylene sheets, and the layers were compression-molded together. The composite samples with varied silica fiber contents up to 2 wt% were mechanically tested. Tensile tests demonstrate slight increases in tensile modulus, tensile strength with increasing silica fiber content. However, silica fiber content within the experimental range does not have prominent effects on yield strength and strain at break.
Abstract: We developed formation technology of composition "steel - material with shape memory effect - high-temperature ceramic wear layer" by means of high-velocity oxygen-fuel spraying in the protective environment of mechanically activated powders TiNiTa and cBN-Co-NiAl-Y. We determined optimal processing parameters. We revealed regularities in the formation of nanosized state composition on the basis of the complex X-ray diffraction and electron microscopy studies. We carried out tests om steel 1045 with a surface-modified layer TiNiTa + cBN-Co-NiAl-Y in high-cycle fatigue, which confirmed the increase in endurance limit.
Abstract: Lead free Multiferroic composites that comprise Co0.6Zn0.4Fe1.7Mn0.3O4 (CZFMO) and 72.5(Bi1/2Na1/2TiO3)-22.5(Bi1/2K1/2TiO3)-5(BiMg1/2Ti1/2O3) (BNT-BNT-BMgT) were synthesized using sol-gel method and it’s structural, ferroelectric and magnetic properties were studied. The X-ray diffraction displayed the single phase formation of parent phases and the presence of two phases in the composites. The samples showed a well saturated polarization-electric field hysteresis loops. The remnant polarization and saturation polarization values are decreased with increasing ferrite content. Room temperature (RT) magnetic measurements show that composites are soft magnetic. The composite with x = 0.2, showed the enhanced magnetic and ferroelectric properties. Moreover, these ME composites provide a great opportunity as potential lead free systems for multifuntional device applications.
Abstract: In this paper the contribution of heterocoagulation of silica sols on powder materials to the formation of nanostructured forms of silicon oxide is presented. To a greater extent heterocoagulation is more appeared on the advanced surfaces of refractory particles and clay, and to a lesser extent on the particles of alumina and silica oxide, the surfaces of which contained significantly fewer active centers. Silica sols have positive effect on drying and firing modes of ceramic materials. It was established that the application of silica sol as binder in the preparation of aluminum silicate ceramics allows to reduce the firing temperature to 150-200oC with a simultaneous increasing of strength characteristics.
Abstract: One-dimensional CdZnS nanostructures have been synthesized through the sublimation. Effect of high substrate temperature on morphology, structural and optical properties of these nanostructures has been studied. X-Ray diffraction peak intensity, lattice parameters, crystallite size decreased with an increase in substrate temperature. The morphology changed with the increase in the substrate temperature. Raman Spectroscopy confirmed the existence of constituent elements in CdZnS solid solution and an increase of Zn concentration with the rise in substrate temperature. The nanostructures exhibited strong photoluminescence emission in the green light region with a substrate temperature-dependent blue shift of 53 meV in emission energy. The Stoke’s shift energy raised from 45 meV to 302 meV as the substrate temperature increased from 510 °C to 550 °C. The stoichiometric deviancies, crystallite size, and quantum confinement effects resulted into an increase in the optical band gap from 2.4 eV to 2.71 eV. The results showed that CdZnS nanostructures could be potential candidates for nanostructure based optoelectronics and photovoltaic devices.
Abstract: The scales of porous carbon materials usage are constrained by their considerably high cost. Therefore, development of new methods for production of porous carbon with the necessary complex of properties from cheap raw materials is actual. Also, porous carbon materials can be used for growth of carbon nanotubes as a matrices of catalyst particles. Herein, the method of fabrication porous carbon materials from waste of oil industry and their use as a matrices of catalyst particles to growth of CNT was developed. CNTs was synthesized by CVD using as hydrocarbon source - propan-butane gas mixture, as catalyst - Ni particles at 650°C, 700°C, 750°C, 800°C. Obtained carbon materials was investigated by Raman spectroscopy and by scanning electron microscope. Investigations on the properties of the obtained porous materials show soot particles sedimented in pores reduce well nanoparticles of metals from salts which act as nuclei for the growth of multiwall carbon nanotubes during pyrolysis of hydrocarbons by CVD method.
Abstract: In this research work, copper sulphide was deposited on glass substrate using spray pyrolysis deposition. The precursors were dissolved in deionized water (DIW) and ethanol, mixed at a ratio of 7:3. The distance between nozzle and substrate was 30 cm and the substrate temperature was maintained at 200 °C. XRD spectra analysis showed four distinctive peaks of high intensity, which indicate pure CuS covellite phase with average crystallite size of 28.3 nm. FESEM characterization of the thin film structure showed a mixture of very small nanoplates and larger square-and triangular-shaped particles. The application of the film as pH sensor showed it has exceptional qualities that include sensitivity and linearity of 22.9 mV/pH and 93.8%, hysteresis of 23.75 mV, repeatability (C.V.) of 0.11% for pH7, stability and reliability (C.V.) of 0.13%, 0.12% and 0.08% for pH 4, 7 and 10, respectively. This research work confirms the feasibility of using CuS thin film as extended membrane in pH sensor and biosensor applications.
Abstract: The effect of alkaline solvent of NaOH and NH3 in the synthesis of nanostructured titania (TiO2) has been studied. Powder of anatase titania as the precursor was mixed with various volume ratios of 10 M of NaOH and 15 M of NH3. The mixture was heated in Teflon-lined autoclave at 150 °C for 24 h. The as-synthesized TiO2 powders were then washed with 0.1 M HCl and calcined at 300 °C. The calcined samples were characterized using TEM (transmission electron microscope), and XRD (X-Ray diffraction). Raman spectroscopy was further used to determine the contributing crystalline phases for the synthesized TiO2. It is shown that varying the solvent ratios of NOH to NH3 resulted in nanotubes, nanosheets, and nanoparticle morphology of TiO2. The TEM images showed the formation of nanotube structure in alkaline ratio NaOH:NH3 of 1:0 and 3:1, with diameter of about 10 nm. At volume ratio of 1:1, the nanosheets and nanotubes both were formed and at volume ratio of NaOH:NH3 of 1:3, nanosheets contributed as its main morphology. While, at fully NH3 solvent, the nanospheres with anatase domain were produced. Raman spectra confirmed that the major contributor for hydrothermal synthesis employing less NaOH for volume ratio of NaOH:NH3 of 3:1 was predominantly anatase with slight presence of titanate. For volume ratio at higher NH3 the presence of titanate is not prominent, but the morphology has already changed into more nanosheet and then nanospheres. The crystallinity of TiO2 anatase crystalline phase was enhanced as more NH3 utilized.
Abstract: Pt-based nanoparticles (NPs) have numerous applications, such as, as catalyst, in car exhaust systems, gas sensors, biosensors and cancer therapy. One of the Pt based NPs which has been successfully produced is core-shell Ag@Pt NPs. Numerous methods for the synthesis of this material have been reported. This paper reports a fully new approach of chemical mediated synthesis for core-shell Ag@Pt NPs. Characterization process for the synthesized Ag@Pt NPs, carried out by the UV-vis Spectroscopy, Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM) showed that the core AgNPs have approximate sizes of 18 nm in diameter are shelled with Pt and the sizes of core-shell Ag@Pt NPs were estimated to be around 29 nm in diameter.