Advanced Materials Research Vols. 123-125

Abstract: The microstructures and magnetic properties of CoPt thin films with thicknesses between 1 and 20 nm deposited on amorphous glass substrate and post-annealing at 600°C for 30 min were investigated. The morphology of CoPt thin film would change from a discontinuous nano-size CoPt islands into a continuous film gradually as the film thickness was increased from 1 to 20 nm. The formation mechanism of the CoPt islands may be due to the surface energy difference between the glass substrate and CoPt alloy. Each CoPt island could be a single domain particle. This discontinuous nano-island CoPt recording film may increase the recording density and enhance the signal to noise ratio while comparing with the continuous film. The as-deposited 5 nm CoPt film revealed the separated islands morphology after annealing at 600°C for 30 min. This nano-size CoPt thin film may be a candidate for ultra-high density magnetic recording media due to its discontinuous islanded nanostructure.

Abstract: In this paper, we report a simple method to fabricate lead oxide nanostructure by electrochemical deposition. In our experiment, the electrolyte was lead nitrate aqueous solution containing some drops of concentrated hydrochloric acid. ITO was employed as both cathode and substrate. The controlled current that was supplied by a direct current power supply passed through the electrolyte to deposit the PbO nanostructure on the surface of ITO at room temperature. The morphology of lead oxide was affected by the concentration of electrolyte. So the impact of the electrolyte concentration on the synthesis of PbO nanostructure was discussed. The as-synthesized products were characterized by scanning electron microscopy and X-ray diffraction. Our results indicate that different PbO nanostructure could be formatted with different electrolyte concentration at current densities in the range of 5-10mA/cm2.

Abstract: Synthesis of PbO nanorods on an ITO glass by electrochemical deposition was reported. Compared with previous report on the electrochemical deposition of PbO nanorods on stainless steel substrates, massive PbO nanorods were obtained with good reproducibility. The PbO nanorods have a length of several tens of micrometers and a diameter of about 100-200nm. The process for electrochemical deposition of PbO nanorods on ITO glass was investigated.

Abstract: Polymer nanocomposite was synthesized through the intercalation and exfoliation of organoclay in an epoxy matrix. The epoxy matrix was composed of diglycidyl ether of bisphenol A (DGEBA, epoxy base resin), 4,4'-methylene dianiline (MDA, curing agent) and malononitrile (MN, chain extender) and organoclay was prepared by treating the montmorillonite with octadecyltrimethylammonium bromide (ODTMA). The intercalation of the organoclay was estimated by wide angle X-ray diffraction (WAXD) and transmission electron microscope (TEM) analyses. In order to measure the cure rate of DGEBA/MDA (30 phr)/MN (5 phr)/Organoclay (5 phr), differential scanning calorimetry (DSC) analysis were performed at the heating rates of 5, 10, 15 and 20 oC/min, and the data was interpreted by Kissinger equation. Thermal degradation kinetics of the epoxy nanocomposite was also studied by thermogravimetric analysis (TGA). The epoxy sample was decomposed in the TGA furnace at the heating rates of 5, 10, 15 and 20 oC/min with nitrogen atmosphere of 50 ml/min. The TGA data was introduced to the Ozawa equation and the degradation activation energy was calculated according to the degradation ratio. The activation energy for cure kinetics was 43.3 kJ/mol and that for thermal degradation was 171.5 kJ/mol.

Abstract: Because the complete restoration of graphene oxide into graphene is unsuccessful, the “direct” exfoliation of graphite into graphene is still remaining challenge. Here, we report in-situ grafting of carboxylic acid-terminated hyperbranched poly(ether-ketone) (HPEK) onto the edge of graphite to afford “edge-functionalized” HPEK grafted graphite (HPEK-g-graphite). The HPEK plays as a macromolecular wedge to exfoliate graphite. The degree of exfoliation of the resultant HPEK-g-graphite was estimated by wide-angle x-ray diffraction (WAXD), transmission electron microscopy (TEM). Due to the macromolecular wedge effect, the resultant HPEK-g-graphite was dispersible well in common organic solvents. Hence, HPEK-g-graphite could be potentially useful for graphene-based materials.

Abstract: Ag nanoparticles colloids have been fabricated by pulsed laser ablation in various liquids. The particle size, morphology and absorption spectroscopy of the obtained nanoparticles colloids were characterized by ultraviolet to visible (UV-Vis) spectrophotometer and transmission electron microscopy (TEM), the average diameter and its distribution were analyzed by Image-ProPlus software. The results showed that the Ag nanoparticles with best characterization are those produced at the repetition rate of 10Hz and laser fluence of 4.2J/cm2 by ablating for 7.5min in the distilled water, with the least average diameter(D=14.48 nm), the narrowest distribution of particles size (=25.8 nm) and more homogeneous morphologies. The effects of experimental conditions on the silver nanoparticles colloid can be explained by fragmentation and melting induced aggregation of colloidal particles by self-absorption of laser pulses.

Abstract: Arrays of zinc oxide (ZnO) micro/nano pillars have been synthesized on indium-tin-oxide (ITO) substrates by a solution route under an external electric current. They were pillar-like morphologies and grew along the c-axis. Some comparative experiments showed that applying the external electric current effectively improved the alignment of the product in a short time. It was indicated that the micro/nano pillars can be obtained in a short time under an external electric current.

Abstract: Nanostructured vanadium pentoxide films have been synthesized by using a sol–gel technology from V2O5 powder and hydrogen peroxide. The V2O5 powder was dissolved in hydrogen peroxide solution, agitated and heated up to 65oC to form gel by the dissociation of the peroxide complexes. The obtained gel was deposited by dip coating technique and dried in air at room temperature. Structural, morphological and compositional analyses were carried out on the prepared samples using X-Ray Diffractometer (XRD), Raman spectrometer and scanning electron microscopy (SEM). The as-prepared films show an amorphous nature, while those annealed at 400oC exhibit orthorhombic structures. The films seem to have grain like structures on annealing which are expected to help the gas sensing properties of the V2O5 films. The annealed films were connected with copper electrodes and used as sensing element. The change in the resistance of the sensing element with respect to the test gas concentration was measured by noting down the resistance at each concentration. Sensitivity of the material linearly increased with different concentrations of ethanol and ammonia. It is clearly seen that the material has more sensing response for ethanol when compared to that of ammonia.

Abstract: GeCu(6 nm)/Si(6 nm) bilayer recording thin film was deposited on nature oxidized silicon wafer and polycarbonate substrate by magnetron sputtering. The ZnS-SiO2 films were used as protective layers. We have studied the thermal property, crystallization mechanism, and recording characteristics of the GeCu/Si bilayer thin film. Thermal analysis shows that the GeCu/Si bilayer film has two reflectivity changes with the temperature ranges, 120 °C ~ 165 °C and 310 °C ~ 340 °C. The results of dynamic tests show that the optimum jitter values at recording speeds of 1X and 4X are 5.8% and 5.9%, respectively. The modulations at 1X and 4X recording speeds are all larger than 0.4.

Abstract: In this paper, zinc oxide nanorods were prepared on many different substrates in the aqueous solution without adding alkali solution at 60°C. A layer of ZnO particles as the seeds for the growth were not needed to be coated on the substrates beforehand. A higher uniform and denser packed array of hexagonal ZnO nanorods forms on the glass substrate than that on the other substrates in our experiments. This technique is applicable for the preparation and patterning of functional ZnO films at low temperature. The growth mechanisms of the as-synthesized ZnO nanorods were also proposed.