Abstract: Carbon nanofibers (CNFs) were grown in situ on porous glass at different temperatures and times using a Ni acetate catalyst and CH4/N2 as a carbon source. The porous glass was obtained by acid leaching of phase separated borosilicate glass, which generates a broad size distribution of mesopores (≈20 nm). Subsequent impregnation with Ni acetate reduces the pore size to ≈ 4 nm but also creates new micropores, thus increasing the surface area. During thermal treatment the surface area decreases as temperature rises, mainly due to shrinkage of the glassy matrix; however new pores are created at ≈ 70 nm (mainly at 600 oC) associated to the generation of CNFs on the glass surface, indicating this temperature offers the best conditions. The CNFs grow inside and fill in the micro-mesopores in the porous glass. They do not grow at 500 oC as the Ni acetate is not transformed into metallic Ni. Ni deactivation occurs at temperatures over 700 oC, thus reducing the formation of CNFs. At 1000 oC the degradation of CH4 leads to a thickening of the CNFs. The thermal degradation of the CNFs occurs in two steps, the first (360-416oC) corresponding to CNFs grown on the glass surface and the second (518-649oC) to CNFs grown inside the glass pores. Treatment times over 2 h lead to the deactivation of Ni, pore shrinkage and hence lower CNF yields.
Abstract: The paper presents the synthesis and investigation of zirconium oxide (ZrO2) nanoparticles that were synthesised by precipitation method with the effects of the temperatures of reaction on the particles size, morphology, crystallite sizes and stability at high temperature. The reaction temperature effect on the particle size, morphology, crystallite sizes and stabilized a higher temperature (tetragonal and cubic) phases was studied. Thermal decomposition, band structure and functional groups were analyzed by Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Thermo-gravimetric analysis (TGA) and Fourier transform infrared (FT-IR). The crystal structure was determined using X-ray diffraction. The morphology and the particle size were studied using (SEM) and (TEM). The shaped particles were confirmed through the SEM analysis. The transmission electron microscopic analysis confirmed the formation of the nanoparticles with the particle size. The FT-IR spectra showed the strong presence of ZrO2 nanoparticles.
Abstract: Nanodispersed rutile with rod-like particles is synthesized by hydrolysis of TiCl4 in hydrochloric acid - ethanol alcohol aqueous solution. It is found that the specific surface area, crystallite size and degree of agglomeration are determined by molar ratio of ethanol in reaction medium. According to HR-TEM images and XRD data rutile crystallites are preferred oriented along the  axis. The analysis of the Raman spectra for samples with different morphology is performed. The model of rutile nanorods nucleation and growth is proposed.
Abstract: Powders consisting of nanoparticles of zinc peroxide were prepared via a simple hydrothermal process using zinc acetate dihydrate and hydrogen peroxide precursors. The size of the crystallites was determined using x-ray powder diffraction. Over a period of 5 hours the crystallite radius increased from 4 nm – 9 nm at a temperature of 68 °C ± 5 °C, with growth rate constant of 0.23 nm3 min−1 calculated using the Lifshitz, Slyozov, and Wagner model. The powders were further characterised with High Resolution Transmission Electron Microscopy, Energy Dispersive X-ray analysis, and Small Angle X-ray Scattering, showing well-crystallised ZnO2 nanoparticles.
Abstract: Cadmium telluride CdTe QDs was prepared by chemical reaction and used to fabricate electroluminescence quantum dot hybrid junction device. QD-LED was fabricated using TPD: PMMA/CdTe/Alq3 device which synthesized by phase segregation method. The hybrid white light emitting devices consists, of three-layers deposited successively on the ITO glass substrate; the first layer was of Tetra-Phenyl Diaminobiphenyl (TPD) polymer mixed with polymethyl methacrylate (PMMA) polymers, while the second layer was 0.5wt% of the (CdTe) QDs for hybrid device, whereas the third layer was Tris (8-hydroxyquinoline) aluminium (Alq3). The optical properties of CdTe QDs were considered by UV-Vis. and photoluminescence (PL) spectrometer. The results show that the prepared QDs were nanocrystalline with defects formation. The Eg calculated from PL were 2.25 eV for Cadmium telluride CdTe QDs was prepared by chemical reaction and used to fabricate electroluminescence quantum dot hybrid junction device. QD-LED was fabricated using TPD: PMMA/CdTe/Alq3device which synthesized by phase segregation method. The hybrid white light emitting devices consists, of three-layers deposited successively on the ITO glass substrate; the first layer was of Tetra-Phenyl Diaminobiphenyl (TPD) polymer mixed with polymethyl methacrylate (PMMA) polymers, while the second layer was 0.5wt% of the (CdTe) QDs for hybrid device, whereas the third layer was Tris (8-hydroxyquinoline) aluminium (Alq3). The optical properties of CdTe QDs were measuredby UV-Vis. and photoluminescence (PL) spectrometer. The results show that the prepared QDs were nanocrystalline with defects formation. The Eg calculated from PL were 2.25 eV for CdTe QDs. The generated white light properties with acceptable efficiency using confinement effect that makes the energy gap larger, thus the direction of the light sites are toward the center of white light color. The organic light emitting device (OLED) wasconsidered by room temperature PL and electroluminescence (EL). Current-voltage (I–V) characteristics indicate that the output current is good compared to the few voltage (6 V) used which gives good results to get a generation of white light. The electroluminescence (EL) spectrum of hybrid deviceshows a wide emission band covering the range from 350 - 700 nm. The emissions causing this white luminescence were identified depending on the chromaticity coordinates (CIE 1931) was found (x=0.32, y=0.33). The correlated color temperature (CCT) was found to be about 5886 K. Fabrication of EL-devices from semiconductors material (CdTe QDs) between two layers organic polymer (TPD) and organic molecules (Alq3) were effective in white light generation. The recombination processes and I-V characteristics gives rises to the output current is good compared to the few voltages used which gives good results to become a generation of light.
Abstract: Utilizing zinc acetate as precursor, and monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) as stabilizers, respectively, ZnO nanoparticles with uniformly distributed grains were synthesized by sol-gel method at different sintering temperatures. Analysis of the degradation of methyl orange by photocatalysis shows that utilizing MEA as the stabilizer and 550°C as the sintering temperature results in smaller grain size, greater surface-to-volume ratio, and a density of surface defects suitable for a photocatalyst. The greatest photocatalytic degradation of methyl orange was achieved under UV irradiation. Based on our microstructural analysis and photocatalysis, the microstructure of ZnO particles and, in turn, their photocatalytic effect are affected significantly by the stabilizer type and the sintering temperature.
Abstract: The almost monodisperse cobble-like CeO2 nanostructures with many pores and a diameter of 50-100 nm have been successfully synthesized by a smart hydrothermal route. XRD, SEM, XPS, BET, and in situ DRIFT were employed to characterize the samples. The results showed that the cobble-like CeO2 owned a fluorite cubic structure and there are Ce3+ ions and oxygen vacancies in surface of samples. Its catalytic activity was investigated by selective catalytic reduction of NOx with NH3. The results showed that cobble-like CeO2 nanostructures exhibit excellent catalytic performance, which can be attributed to the much larger surface areas, novel morphology and the best redox behaviour of surface oxygen on the CeO2 surface.
Abstract: In the present study, the effects of different parameters of needleless electrospinning systems on polyacrylonitrile (PAN) nanofibers morphology and diameter were studied. The electric field profile at the surface of the spinneret and electrospinning zone was evaluated by Finite Element Method. The PAN nanofibers were used as the precursor to fabricate carbon nanofibers. Scanning electron microscope (SEM), X-ray diffraction and Raman spectroscopy were used for electrospun nanofibers analysis. The results of electric field analysis indicated, in the spinning direction, the electric field was concentrated at the surface of the spinneret and decayed rapidly toward the surface of the collector. Increasing polymer solution concentration from 7.00 to 11.00 wt.% resulted increasing nanofibers diameter form 77.76 ± 19.44 to 202.42 ± 36.85. The results of X-ray diffraction and Raman spectroscopy show that heat treatments could convert needleless electrospun PAN nanofibers to carbon nanofibers.
Abstract: This paper presents the results of the development of nanoscale multi-layered composite coatings for improving the contact performance of ceramic cutting tools. These nanocoatings help reducing brittle fracture of cutting edges and ensure a balanced wear of tool contact areas during dry high-speed machining of hardened steels. A filtered cathodic vacuum arc deposition process was used to generate the nanoscale multi-layered composite coatings (NMCC) with improved physical and mechanical properties and adhesion strength to ceramic substrate. In this work, thermodynamic criteria were used to evaluate the selected composition of NMCC, and the crystal-chemical, physical, mechanical and cutting properties and wear mechanisms were studied. Ti-(TiAl)N-(ZrNbTiAl)N coating was deposited on Al2O3, Al2O3-TiC and Si3N4 ceramic substrates. Test results showed that the wear mechanism of the coated tool was predominantly due to adhesive-fatigue processes. The development of wear was observed to be centered on the rake and flank faces of the tool without brittle chipping. The results of high-speed longitudinal turning of hardened steel X153CrMoV12 showed an increase in tool life by a factor of 1.5 against the uncoated tools and a factor of 1.3 compared with standard PVD coating Ti-(TiAl)N.
Abstract: In recent days nanotechnology has become one of the most excellent escalating technologies in the field of engineering and scientific areas. During the last decade there are numerous experimental analysis was carried out by many scholars on nanoparticles. This research work was carried out through different samples with varied composition of the nano-materials and the results were found on the optimisation of machining parameters of copper-multiwalled carbon nanotubes-graphene hybrids. The machining parameters of the hybrid composites were optimized using Taguchi method after the hybrid composite was made by stir casting process and analysis of variance (ANOVA) was used to analyse data and find the most influencing factor. The Taguchi’s signal to noise ratio was used is ‘smaller is better’. Confirmatory examinations were also performed for the purpose of validation after obtaining the optimized results. The hybrid nanocomposite specimens thus prepared were characterized by scanning electron microscope. From the results it was found that the addition of carbon nanotubes and graphene into copper leads to lower surface roughness values compared to pure copper.