Current Nanoscience - Volume 8, Issue 4, 2012

Fe3O4 nanoparticles were successfully synthesized using electrooxidation of iron by a chronoamperometric technique in the presence of tetramethylammoniumchloride surfactant in an aqueous medium. The effect of surfactant concentration and ultrasonic excitation on the structural properties of the nanoparticles we studied using XRD, AES, FT-IR, TEM, and UV-visible spectroscopy. XRD results clearly showed the formation of the spinel phase of Fe3O4. The purity of the nanoparticles was confirmed by AES. FT-IR spectroscopy results confirmed that the surface of the Fe3O4 nanoparticles was covered by surfactant molecules due to electrostatic attraction. The resultant TEM images showed that the particle size and their size dispersion can be controlled by surfactant concentration and ultrasonic treatment. According to these images, an increase in surfactant concentration leads to a reduction in the particle size, a narrower size distribution, and also the particle shape changing from cubic, tetragonal, hexagonal, and triangular to quasi-spherical. Electron diffraction results show that the particles have polycrystalline structure. UV-vis spectroscopy, indicating that their maximum absorption wavelength and peak width decrease with increasing surfactant concentration and ultrasonic treatment.

In this paper, the influence of nickel silicide thin film on series resistance of silicon solar cells is investigated. The frontside two-layer electrodes are fabricated by the light induced electroless plating of nickel and light-induced plating of silver. The nickel films are deposited onto the silicon wafers surface by light induced electroless plating in the nickel-plating bath containing main nickel source. The nickel film thicknesses of 200 nm, 400 nm and 600 nm are identified by the SEM observations. The formation of nickel silicide thin films are obtained after the thermal annealing process for 1 min, 3 min and 5 min. The nickel silicide thin film reduces the series resistance mainly due to the decrease of contact resistance between metal electrode and silicon substrate. The reduction in contact resistance and series resistance are confirmed by using transmission line model analysis and dark current-voltage characteristics in experiment. The improvement of series resistance extracted from the dark current-voltage curve in the upper voltage range is observed. The minimum series resistances of silicon solar cells with different nickel film thicknesses are obtained after different thermal annealing periods, respectively. The silicon solar cell with nickel film of 400 nm thick after thermal annealing process of 3 min possesses the minimum series resistance of 0.66 Ω cm2.

Size-selected palladium nanoclusters have been produced by dc sputtering and inert gas condensation technique using mixtures of argon and helium gases. By controlling the source parameters, it was possible to produce Pd nanoclusters with size in the range of 2-10 nm. Transmission electron microscopy (TEM) images were used to confirm the produced sizes of nanocluster. It was found that increasing the percentage of helium to argon have two main effects: i) decreases the nanocluster size as a result of the high drift velocity of helium, and ii) decreases the number of measured nanoclusters due to the low sputtering yield of helium. Since He gas is primarily responsible for the cluster-condensation process, its partial pressure can be used to control the nanoclusters growth. The source parameters and their effects on the size and number of nanoclusters are of great importance in understanding the Pd nanoclusters growth mechanism.

The present study is aimed at the effect of heat treatment on nanosilver-impregnated Populus nigra, Fagus orientalis, and Abies alba to find out nail and screw withdrawal resistance. Treatments included control, heat-treated, and nano-silver-impregnated heattreated specimens. Empty-cell process was used for impregnation with a 200 ppm aqueous dispersion of silver nanoparticles with the size range from 10 to 80 nm under 3 bars in a pressure vessel for 20 minutes. For heat treatment, both seasoned nano-silver-impregnated and heat-treatment specimens were kept for 24 hours at 135°C. The nails and screws were installed according to ASTM D 1761-88 specifications. Results showed that the maximum nail and screw withdrawal resistance was closely related to the density. The difference between longitudinal and radial withdrawal resistance in both nail and screw was significantly influenced by the species as a softwood or hardwood. Regardless of the species, heat treatment was more influenced by the density rather than species. However, nano-silverimpregnation of the specimens aggravated the effects of heat treatment in hardwoods (more increasing in poplar and more decreasing in beech), but it decreased the withdrawal resistance in fir.

ZnFe2O4 and CdS nanoparticles were loaded onto TiO2 nanotubes (NTs) formed on Ti-5Zr alloy. The ZnFe2O4 and CdS nanoparticles were obtained by electrodeposition and chemistry bath deposition (CBD) methods, respectively. For the electrodeposition of Fe-Zn alloys, transitional steady current density decreased while the concentration of Zn ion in the electrolyte increased. Meanwhile, Fe/Zn ion ratio in the electrolyte determined the composition of Fe-Zn alloys; optimum electrodeposited Fe-Zn alloys for ZnFe2O4 formation were obtained by tuning the deposition variables. The mean diameters of ZnFe2O4 and CdS were about 160 nm and 25 nm, respectively. Study on scanning electron microscopy (SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) indicated that the prepared samples were highly ordered TiO2 NTs composite with ZnFe2O4 and CdS nanoparticles loading on.