Key Engineering Materials Vols. 336-338

Abstract: Monodispersed Cu powders were prepared in aqueous solution through a wet-reduction process with hydrazine hydrate (N2H4·H2O). In particular, the effect of the dispersant such as sodium pyrophosphate decahydrate (Na4O7P2·10H2O), carboxymethyl cellulose sodium salt (CMC) in water solvent on the particle size for the prepared Cu powders was investigated. The Cu powders essentially were monodispersed and irregular in shape regardless of reaction temperature and dispersant. In the case of adding the Na4O7P2·10H2O, the particle size of Cu powders increased with the increase of reaction temperature, which the particles were agglomerated in irregular shape and became to be large. The particle size distributions was asymmetry and to be broad regardless of reaction temperature. On the other hand, when the CMC was added, the particle size of Cu powders, which were much finer compared with adding the Na4O7P2·10H2O as a dispersant, was not much changed with reaction temperature. The particle size distribution of Cu powder was much narrow regardless of reaction temperature. As a result, it would be suggested that the CMC was more effective dispersant reagent to produce the monodispersed and fine Cu powders with narrow size distribution using the wet chemical reduction process

Abstract: This paper introduces a process for the growth of oxide nanorod, nanotube, and nanocable arrays that combines sol preparation and template-based electrophoretic deposition. Examples are shown that the sol electrophoretic deposition is an effective method for the formation of polycrystalline and single crystal oxide nanorod arrays, nanotube arrays and conformal coating of thin films of oxides on metal nanorods to produce metal-oxide core-shell nanocable arrays.

Abstract: This article introduces a process for the growth of one-dimensional oxide nanomaterials that combines rheological phase reaction and hydrothermal self-assembling process. Fundamentals and practical approaches of hydrothermal self-assembling process and rheological phase reaction are briefly described. Particular attention is devoted to the rheological self-assembling for the growth of low dimensional oxide nanomaterials. Many examples are shown that the rheological self-assembling is an effective method to prepare one-dimensional nanomaterials, organic-inorganic hybrids and 1-D nanomaterial array for optical-electronic and electrochemical devices and catalysis. Morphologies, microstructures, properties, and application of one-dimensional oxide nanomaterials are reviewed.

Abstract: In this seminar, I will present our recent work on the growth and electrochemical properties of single crystalline vanadium pentoxide (V2O5) nanorod and Ni-V2O5·nH2O nanocable arrays. These nanostructures were prepared by solution synthesis and template-based electrodeposition. Processing, morphology, structure and electrochemical properties of these nanostructures will be discussed. These nanostructured electrodes of vanadium pentoxide demonstrate significantly enhanced intercalation capcity and charge/discharge rate compared to the plain film electrodes, due to the high surface area and short diffusion distance offered by nanostructure.

Abstract: The carbon nanotube reinforced Ni-P matrix composite coating on 45# steel has been prepared by electroless plating method in this study. The microstructure and the corrosion properties of the composite coating were investigated systematically using SEM and a potentiostat. SEM results show that the carbon nanotube was uniform embedded in the crystal grains of Ni-P. The polarization curves indicate that the composite coating exhibit excellent corrosion resistance properties which is superior to that of the conventional Ni-P coating.

Abstract: Surface-enhanced Raman scattering (SERS) integrates high levels of sensitivity with spectroscopic precision and thus has tremendous potential for chemical and biomolecular sensing. The key to the wider application of Raman spectroscopy using roughened metallic surfaces is the development of highly enhancing substrates for analytical purposes, i.e., for better detection sensitivity of tracing contaminants and pollutants. Controlled methods for preparing nano-structured metals may provide more useful correlations between surface structure and signal enhancement. Here, we self-assembled silver nanorods on glass substrates for sensitive SERS substrates. The enhanced surface Raman scattering signals were observed and mainly attributed to the local field enhancement.

Abstract: La2(MoO4)3 microcrystals with rodlike morphology have been successfully grown through hydrothermal microemulsion process at 180°C, pH =9 and 12 h. Quaternary microemulsion is composed of CTAB/water/hexane/n-pentanol. The obtained sample is characterized by means of XRD, FESEM, TEM. Formation mechanism is preliminarily discussed.

Abstract: Yttrium oxide hydroxide nitrate nanorods were prepared via a facile hydrothermal method using PEG-6000 as template in Y(NO3)3 and KOH reactant system. The effect of hydrothermal treatment time on the crystallite structure, the crystallite shape and size was investigated by XRD and FE-SEM measurements. XRD results showed that the main phase of the as-prepared product was Y4O(OH)9NO3 crystal of monoclinic phase. FE-SEM images displayed that the size of the nanorods grows large with increasing time from 5h to 24h. Furthermore, no shape change was found, demonstrating that the as grown nanorods are stable when the reaction time increased from 1h to 24 h. Dissolution recrystallization process was proposed to explain the growth process of Y4O(OH)9NO3 nanorods.

Abstract: Polypyrrole(PPy) nanowires were prepared by template-free method electrochemically. The effect of process parameters on the morphology of PPy was investigated. The electrocatalytic effect of PPy nanowire modified electrodes was characterized by its amperometetric response toward nitrate ions. The experimental results indicated that the process parameters of the modified electrodes such as concentration of pyrrole monomer, concentration of support electrolyte (LiClO4), and the pH of buffer solution have significant effects on the diameter the length and smooth of PPy nanowires, and thus have obviously effects on electroreduction current density of nitrate ions. Under the optimized conditions, the PPy nanowire modified electrodes have high electrocatalytic activity toward nitrate electroreduction.