RESUMO
In the present study, combustion synthesis of zinc oxide and zinc sulfide nanoparticles as well as their composite was studied using zinc nitrate and thioacetamide as starting materials, and ethylene glycol as fuel. The influence of different parameters such as oxidizer to fuel (O:F) ratios and calcination process on the structure, microstructure, photoluminescence and optical properties was studied. X-ray diffraction (XRD) patterns showed different combinations of wurtzite structure for zinc oxide and zinc sulfide phases obtained using different O:F ratios of 1:1 and 2:3. Scanning electron microscopy (SEM) micrographs revealed that particles with different morphologies were synthesized depending on the O:F ratio. Besides, nanometer particles, or even quantum dots, could be obtained. Transmission electron microscopy (TEM) micrographs also showed the formation of zinc oxide/ zinc sulfide quantum dots composite using ethylene glycol fuel with O:F ratio of 2:3. Fourier transformed infrared (FTIR) analysis of samples showed carbon bonds of carbonaceous matters in addition to Zn-O and Zn-S bonds due to incomplete combustion. Photoluminescent emission spectra indicated that the highest intensity of emission in blue-green region was obtained from the particle synthesized using ethylene glycol and O:F ratio of 2:3, which may be related to the high density of lattice defects. Band gaps estimated using UV-visible (UV-Vis) spectra were 3.4 and 5.4 eV which can be assigned to the dual nature of particles: in some parts quantum size and in the other parts nanosize particles.
RESUMO
Nanoparticles of Europium oxide doped with Zinc oxide were synthesized via microwave-assisted combustion method. Citric acid as a simultaneous fuel and chelating agent and glycine as a fuel and mixture of these fuels were sleeted. X-Ray diffraction patterns (XRD) indicated the formation of ZnO structure with a few amount of Eu2O3 phase. Fourier transformation infra red (FTIR) spectra reveal the increase of ZnO4 bonds with glycine content of fuels mixture. Scanning electron microscope (SEM) images showed the conversion of nanosphere to spongy-like structure with respect to change of fuel mixtures from citric to glycine. From transmission electron microscopy (TEM) nanoparticles of a mean size 30 nm are observed Green fluorescence emission of different samples was due to activation of self activated center of ZnO structure through transition of electron from Eu3+ to Vzn sites.
RESUMO
In this work, an electrophoretic deposition (EPD) technique has been used for deposition of carbon nanotubes (CNTs) on the surface of glass fiber textures (GTs) to increase the volume conductivity and the interlaminar shear strength (ILSS) of CNT/glass fiber-reinforced polymers (GFRPs) composites. Comprehensive experimental studies have been conducted to establish the influence of electric field strength, CNT concentration in EPD suspension, surface quality of GTs, and process duration on the quality of deposited CNT layers. CNT deposition increased remarkably when the surface of glass fibers was treated with coupling agents. Deposition of CNTs was optimized by measuring CNT's deposition mass and process current density diagrams. The effect of optimum field strength on CNT deposition mass is around 8.5 times, and the effect of optimum suspension concentration on deposition rate is around 5.5 times. In the optimum experimental setting, the current density values of EPD were bounded between 0.5 and 1 mA/cm². Based on the cumulative deposition diagram, it was found that the first three minutes of EPD is the effective deposition time. Applying optimized EPD in composite fabrication of treated GTs caused a drastic improvement on the order of 108 times in the volume conductivity of the nanocomposite laminate in comparison with simple GTs specimens. Optimized CNT deposition also enhanced the ILSS of hierarchical nanocomposites by 42%.
