Advanced Materials Research Vol. 979

Abstract: ZnO nanoparticles were synthesized from PEG600 diacid modified-Zn (CH₃COO)₂.2H₂O solution by precipitation method and an aqueous NaOH solution was used as precipitating agent. The crystal structure, morphology and optical property of ZnO nanoparticles were characterized by XRD, SEM and UV-Vis spectrophotometer, respectively. The crystallinity increased while the E_g value decreased as a function of PEG600 diacid concentrations. The ZnO nanoparticles that had the highest crystallinity and lowest E_g value exhibited the highest efficiency of photocatalytic degradation of about 90% when irradiating with a UV light for 3 h.

Abstract: The (1-x)[(Na_0.515K_0.485)_0.94Li_0.06(Nb_0.8Ta_0.2)O₃]-xYMnO₃ (x = 0, 0.005, 0.01, 0.015 and 0.02) lead-free ceramics were synthesized by solid-state reaction sintering method. It was found that the addition of YMnO₃ affected on the grain size, phase structure and electrical properties of (Na_0.515K_0.485)_0.94Li_0.06(Nb_0.8Ta_0.2)O₃ ceramics. The grain size decreased with increasing YMnO₃ content (x ≥ 0.01) and led to poor densification. The ceramic doped with 0.5 mol% YMnO₃ showed good electrical properties such as d₃₃ = 195 pC/N, k_p = 43.9 %, T_c = 292 °C, T_O−T = 35 °C, ε_r = 820 and rather low dielectric dissipation factor = 2.1%. This indicates that 0.5 mol% YMnO₃ -doped (Na_0.515K_0.485)_0.94Li_0.06(Nb_0.8Ta_0.2)O₃ piezoceramic is an alternative lead-free piezoelectric material for the development of piezoelectric devices working at high temperature.

Abstract: The lithium lanthanum borate glasses doped with Dy₂O₃ were prepared by the melt quenching technique. The Dy₂O₃ doped concentration has been increased and substituted B₂O₃ from 0.00 to 1.50 mol% in the glasses. The photoluminescence, optical absorption and physical properties of these glasses have been investigated in this work. The experimental results show that, the molar volume of glasses tended to increase with increasing of Dy₂O₃ concentration, but the density were not depending on the concentration of Dy₂O₃. The UV-Vis-NIR spectra, absorption bands at 451, 798, 894, 1085 1264 and 1676 nm have been observed. For Dy³⁺ doped glasses, emission bands centered at 483, 575 and 664 nm have been observed with 388 nm excitation wavelength. The emission spectra have shown the strongest band in the glasses with 0.50 mol% Dy₂O₃ concentration.

Abstract: This work studied about the angular and intensity distributions on multiple scattering gamma energy 662 keV, obtained from ¹³⁷Cs source. The gamma photons are incident on aluminium scatterer of varying thickness is studied experimentally in both the forward and backward hemispheres. The observed spectra recorded by a properly shielded NaI(Tl) scintillation detector. To extract the contribution of multiply scattered photons having same energy as in the singly scattered distribution from the measured spectra, a singly scattered distribution is reconstructed analytically. We observed that the number of multiply scattered photons also increases and saturates at a particular value of the scaterrer thickness and determined at different scattering angles.

Abstract: Ag/ZnO powders were synthesized through hydrolysis of Zn²⁺ in an alkaline solution at various mole ratios of Zn²⁺:OH^- without any stabilizer. At a mole ratio of Zn²⁺:OH^- = 1:1.5, the ZnO particles showed as bi-hexagonal prisms. At higher OH^- concentrations, the shape became spherical and then finally transformed to an agglomeration of platelet like-shapes at mole ratios of Zn²⁺:OH^- = 1:5. The photocatalytic activity was investigated through degradation of a methylene blue solution. Under irradiation from blacklight fluorescence tubes, ZnO prepared from Zn²⁺:OH^- = 1:1.5 was the best photocatalyst compared with those prepared from different mole ratios of Zn²⁺:OH^-. This could be due to a high area of hexagonal facets as represented by the (0002) plane. By varying the amount of added Ag between 1-5 mol%, the ZnO prepared from 3 mol% of Ag showed the highest efficiency for photocatalytic degradation of methylene blue and its activity was also better than for pure ZnO.

Abstract: Zinc sulfide (ZnS) nanostructures are important materials for many technologies such as sensors, infrared windows, transistors, LED displays, and solar cells. However, many methods of synthesizing ZnS nanostructures are complex and require expensive equipment. In this study, a liquid-solid chemical reaction without surfactant was used to synthesize ZnS at room temperature. In addition, commercial grade zinc oxide (ZnO) particles were used as a precursor. The effect of the addition of acids and inorganic salts were investigated. The products were characterized by field emission scanning electron microscopy (FESEM) coupled with energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results show that the nanoparticles of ZnS were obtained in hydrochloric acid and acetic acid addition. The diameters were in the range of 10 to 20 nm and 50 to 100 nm, respectively. In the case of a sodium chloride salt addition, a ZnS structure was obtained with a particle size of approximately 5 nm and a flake-like morphology.

Abstract: nanosized zinc sulfide (ZnS) is a special property semiconductor material widely used in many applications such as catalyst, light emitting diode, transistor, gas sensors, biosensors, UV-light sensors, and photovoltaic cell. The wet chemical method is a simple and low-cost method to prepare nanosized zinc sulfide. However, the wet chemical reaction using sodium sulfide without surfactant or template has rarely been reported. In the present work nanosized zinc sulfide particles were synthesized by simple wet chemical reaction method at room temperature and without any surfactant. The influence of sulfur source, sodium sulfide and potassium sulfide used as the reactant were investigated. The samples were characterized by scanning electron microscopy coupling with energy-dispersive X-ray spectroscopy (FESEM-EDX), and transmission electron microscopy (TEM). The results show that the nanoparticles of zinc sulfide were obtained from sodium sulfide and potassium sulfide with particles sizes are in the range of 10 to 50 nm and 25 to 50 nm respectively. In addition, from FESEM microphotograph the primary ZnS particles size of around 5 nm and 25 nm were obtained by 10% salt (sodium chloride, potassium chloride, sodium acetate) addition with sodium sulfide and potassium sulfide reactant respectively.

Abstract: In this study, we controlled nanostructure and morphologies of the vertically aligned zinc oxide nanowires (ZnO NWs) on 200 nm-thick zinc oxide seed layer. The ZnO nanowires were synthesized by the hydrothermal method at 90°C for 6 hours in the precursor solutions. The solutions with four different precursor concentrations of zinc nitrate and hexamethylenetetramine (HTMA) in distilled water were prepared at 5 to 20 mM. The effect of the precursor concentrations were systematically investigated based on the structural and morphologies of ZnO NWs. Most physical investigations were performed with grazing-incidence X-ray diffraction (GIXRD) and field-emission scanning electron microscopy (FE-SEM). From GIXRD, the peak intensity and full width at half maximum (FWHM) of the ZnO (002) were both increased as the precursor concentration was increased. It was also found that the diameter and length of the ZnO nanowires were increased with the increased precursor solution concentration. The average diameter and length of the ZnO NWs could be controlled from 60 to 135 nm and 0.39 to 1.73 μm, respectively.

Abstract: This study investigates tantalum oxide (Ta₂O₅) nanorods prepared by the dc magnetron sputtering with the glancing angle deposition (GLAD) technique. Silicon (100) wafer and glass slides were used as the substrates. The effect of the glancing angle varying from 73-87°, on the structural and optical properties were investigated by field-emission scanning electron microscopy (FE-SEM), atomic force microscope (AFM) and spectrophotometry. The results show that the deposition rate and diameter of Ta₂O₅ nanorod films were decreased with the increase in the glancing angle. At the highest glancing angle of 87°, the prepared Ta₂O₅ nanorod yielded the highest porosity from the vertically aligned columnar structure, and were must suitable for many functional applications.

Abstract: The strontium hexaferrite (SrFe₁₂O₁₉) and Co-substituted strontium hexaferrite (SrCoFe₁₁O₁₉) were prepared by ceramic method. The milled mixture of Fe₂O₃, SrCO₃ and CoO powders were calcined at 1100°C and pellets sintered at 1300°C in air. The crystal structure, morphology and magnetic properties of samples have been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM), respectively. The crystal structure of SrFe₁₂O₁₉ was hexaferrite with the crystallite size and the lattice constants a and c of 59.6 nm, 5.8 Å, and 23.0 Å, respectively. Also, the crystal structure of SrCoFe₁₁O₁₉ was hexaferrite with the crystallite size and the lattice constants a and c of 63.7 nm, 5.9 Å and 23.0 Å, respectively. The morphology of obtained samples changed from hexagonal rods to discs shape and grain sizes increased with the increase of doped Co in SrFe₁₂O₁₉. SrFe₁₂O₁₉ with the coercive force (Hc) of 2,133 Oe was classified as hard ferrite magnetic. While, Co-substituted strontium hexaferrite (SrCoFe₁₁O₁₉) was soft ferrite magnetic with coercive force of 64 Oe. Results indicated that magnetic properties of samples such as hard ferrite magnetic and soft ferrite magnetic showed great dependence on the cobalt additive in strontium.