Advanced Materials Research Vol. 1119

Abstract: The nanocomposite of polyaniline (PANI) and bimetallic nanoparticles of silver and iron were prepared by the oxidative polymerization of aniline and the reduction process of bimetallic compound with the presence of nitric acid and PVA. The nanocomposite thin films in various compositions were deposited using spin-coating technique. The films were characterized by UV-visible spectroscopy to study the optical and structural properties. The microphotograph from TEM image shows the nanospherical of Ag-Fe alloy particles in 5 – 25 nm diameter size. The sensitivity performance was tested using I-V measurement to obtain the changes of resistivity before and after the incubation with E. coli bacteria in water. UV-visible absorption bands show the single absorbance peak at 422 – 424 nm in each band indicating the Ag-Fe alloy nanoparticles form. I-V characteristic shows the sample which contains Fe-rich Ag-Fe alloy performed high sensitivity on E. coli.

Abstract: A new lithium cobalt oxyhydroxide compound has been successfully synthesized. This new compound has been found to be related to the low temperature LiCoO₂ (LT-LiCoO₂) spinel structure formed at low processing temperatures. With the use of a modified sol-gel approach, this compound with the composition of LiCo₂O₃(OH) can be successfully synthesized at around 150 °C. Structural analyses using powder X-ray diffraction (XRD) and selected area electron diffraction (SAED) suggest a cubic-spinel structure, which is also supported by FT-IR and TG/DTA analyses. In addition, from the TEM morphological analysis, a very fine nanograined LiCo₂O₃(OH) powder with an average grain size of 5 nm has been obtained. From these results, the presence of OH or water at low processing temperatures promotes a favorable formation of this structure. At higher temperatures (>400 °C), the phase transforms to a layered high-temperature LiCoO₂ (HT-LiCoO₂) structure with the excess cobalt precipitated as Co₃O₄ as suggested by the in-situ high temperature XRD analysis.

Abstract: This study was conducted to investigate the effect of nanoclay on hardness, pull off and blistering effect of polyester based coating. Polyester coat, nanoclay and hardener (MEKP) were mixed and mechanically stirred for one hour at ambient temperature at a shear rate of 1000 rpm. Prepared coating was then applied on the surface of plywood for the characterization of the hardness and pull off strength and for the observation of blistering effect towards sea and distilled water. As a result, 6% nanoclay loading gives better hardness strength which is 65% increment from unmodified polyester. However, the pull off strength shows that 2% of nanoclay loading gives higher strength among others with 114% increment compared to unmodified polyester coating. Blister was mostly observed at samples without nanoclay loading for both sea water and distilled water. While the less blistering effect was present at 2% nanoclay loading for sea water and 4% nanoclay loading for distilled water. The presence of nanoclay within the coating improves its bonding ability and the decreasing the micro space within the polymer. Blistering effect for highest and lowest frequency was observed by electron scanning microscope (SEM).

Abstract: This paper describes the experimental procedures for developing and testing of a new class of hybrid nanocomposites, the neuron-synapse configuration ones. Two carbon based nanostructures, multiwall carbon nanotubes and multi-layered graphene, were incorporated to carbon epoxy laminated. The processing technique employed which includes a combination of sonication and high shear mixing allows the formation of a neuron-synapse nanostructure. X-ray diffractometry indicates that multi-layer graphene (MLG) has an average diameter close to 22 nm. TEM observations and raman spectroscopy revealed a thickness of 10 graphene layers, and a hybrid nanostructure where MWNT interpenetrated the MLG nanostructure. The hybrid nanostructure seems to be linked by Van der Walls bonds. This could be the reason for large crack density generated during short-beam bending tests. No significant stiffness changes were observed in both, tensile and bending, tests, while tensile strength were improved by 19% with 1 wt.% addition of graphene the interlaminar shear strength, was increased by 22% with the addition of MWNTs and 2.5% with the graphene (1 wt.%) and MWNT (0.3 wt.%) together.

Abstract: Highly-ordered TiO₂ nanotube arrays were fabricated by electrochemical anodizing, using titanium foils as the anode and cathode and changing the amount of fluoride (NH₄F) in the solution. The effect of synthesis parameters, such as, ethylene glycol solutions containing different amounts of water, NH₄F, anodizing voltage, and current density were studied on the optical and morphological properties. It was observed from XRD espectra, that Anatase and Rutile phases were influenced by annealing, between 300 and 723 K, for all the samples, while morphological changes were not observed. Nanotubes diameters varying beteween 20 and 50 nm with diferent length sizes were observed from SEM micrographics. A high absorption for the UV region and a gap band round of 3.1 eV were obtained from spectrophotometry measurements. The correlation between the synthesis parameters and the optical properties presented are an excellent indicator for the TiO₂ nanotubes application as optical sensors.

Abstract: This article deals with a development of new filtration materials for respirators. Contemporary used filters with charged microfibers are not sufficiently stable in all conditions and not efficient for all types of particles and that is the reason why the requirement for new generation of filtration materials is rising up. The research was focused on the development of nanofibrous filters that have a great precondition to be used as filters for respirators. The filtering material was designed as a multilayer sandwich consisting of spundbound, meltblown and nanofibrous layers. For the evaluation of final properties and filtering performances different 3D structures were also created.

Abstract: SnO₂ nanowires have been fabricated using thermal evaporation of the mixed powders of SnO₂ and active carbon with Au catalysts. The morphology and structure of the prepared nanowires are determined on the basis of field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometer (EDS), x-ray diffraction (XRD) and transmission electron microscopy (TEM). The comb-shape interdigitating electrode made by MEMS technology is used to auxiliary investigating the gas sensing performance of the synthesized SnO₂ nanowires. The SnO₂ nanowires have sensing response to acetylene concentration of 1000 ppm under operated temperature of 300°C. The gas sensing mechanism is attributed to the gas adsorption and desorption processes occurring on the surface of the gas sensing material.

Abstract: Highly oriented and well-aligned ZnO nanorod arrays were synthesized by low-temperature solution phase method on copper substrate under different conditions. Results illustrated that dense ZnO nanorods were vertically and uniformly distributed on the substrate. The effects of precursor concentration, growth temperature and time on the morphologies of nanorod arrays were investigated systematically. It is demonstrated that the controllable growth of well-aligned ZnO nanorods can be realized by readily adjusting the preparation parameters. The high quality ZnO nanorod arrays could be achieved via the chemical approach at low temperature.

Abstract: To improve the fuel efficiency of automobile internal combustion engines, we investigated the fundamental mechanism of friction reduction within engine moving parts. A new coating was designed by introducing SiO₂ nanoparticles in FEP film. The SiO₂ nanoparticles were functionalized with hydrophobic fluoroalkyl units on their surface to create additional low friction property. Universal Surface Tester friction measurements revealed a significant reduction of the friction coefficient with increasing number of hydrophobic fluoroalkyl units for SiO₂ surface functionalization. To clarify the friction reduction mechanisms by the functionalization of SiO₂ nanoparticles, a quantum chemical calculation was carried out. The result indicates that an attractive force occurs between nanoparticle Si atoms and polymer F atoms, while by adding fluoroalkyl units on the SiO₂ nanoparticle surface, this force changes to repulsive. By performing a molecular dynamics simulation of a shear model between FEP film and SiO₂ nanoparticles, we observed a decrease of friction force with increasing fluoroalkyl units which lead smooth rolling motion of nanoparticles, thus confirming the repulsive effect of nanoparticle functionalization. We conclude that fluoroalkyl units on the SiO₂ surface play an important role in creating a repulsive force between nanoparticle and FEP film which lead to low friction coefficient.

Abstract: A microwave assisted precipitation method has been used for the synthesis of ZnO nanorods by reacting zinc nitrate hexahydrate and sodium hydroxide. Polyacrylic acid (PAA) uses as a polymeric additive in process. The synthesized ZnO is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser light scattering technique. It is found that ZnO nanorods exhibit a crystalline structure with hexagonal structure of the wurtzite. Primary size of the synthesized ZnO nanorods can be controlled by PAA concentrations. Increasing of PAA concentrations provide ZnO nanorods with smaller and shorter size.