Mario Miki-Yoshida

Structural analysis and growing mechanisms for long SnO2 nanorods synthesized by spray pyrolysis

Flat-surfaced, rod-like materials were obtained by synthesizing long one-dimensional SnO2 structures using a new spray pyrolysis method. The structure and growing mechanisms were evaluated by using scanning and transmission electron microscopy and atomic force microscopy. Molecular simulation tools and high resolution transmission electron microscopy images allowed the analysis of a dynamic behaviour for energy release which determines how the structures are formed by searching for an axial energy release direction.

Microstructural study of ZnO nanostructures by rietveld analysis

ZnO nanorods were synthesized by induced seeds by chemical bath deposition using hexamethylenetetramine (HMT) as a precipitant agent and zinc nitrate (ZN) as Zn2+ source at 90°C. The influence of reactants ratio was studied from2 to 0.25 ZN/HMT molar. The results obtained by scanning electron microscopy confirm that the diameter of nanorods was affected directly by the concentration of both zinc and OH- sources. Nanotubes (hollow nanorods) were obtained with high HMT concentrations and were turning over nanorods as HMT concentration decreased. Microstructural information was obtained by Rietveld refinement of grazing incidence X-ray diffraction data. These results evidence low-textured materials with oriented volumes less than 18% coming from (101) planes in Bragg condition.

Functional nanostructured oxides: synthesis, properties, and applications

Abstract This chapter presents a brief description of basic concepts of nanostructured materials, with a focus on metal oxides, including its synthesis, microstructure, properties, and applications. Nanostructured metal oxides represent one of the most important and studied class of materials, because they offer a broad range of unique properties, which differ to a great extent to those observed in their bulk analogues. As examples of nanostructured metal oxides, case studies are included: Fe3O4 hollow nanospheres, ZnO and CuO nanorods, and CuFeO2 thin films. Their synthesis conditions via aerosol-assisted chemical vapor deposition (CVD), their characterization and applications for water remediation and H2 generation are also depicted.

Microstructural Evolution of (Al2024-CNTs)-T6 Composites Produced by Mechanical Alloying and Hot Extrusion.

R. Perez-Bustamante,* N. Anaya-Muro,** R. Cruz-Garcia,** M. J. Gonzalez-Ibarra,** J. Gonzalez-Cantu,** I. Estrada-Guel,* O. Solis-Canto,* J. M. Herrera-Ramirez,* M. Miki-Yoshida,* R. Martinez-Sanchez* *Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia. Miguel de Cervantes No. 120, C.P. 31109, Chihuahua, Chih., Mexico. **Universidad Autonoma de Chihuahua (UACH), Facultad de Ingenieria, Circuito No. 1 Nuevo Campus Universitario, C.P. 31125, Chihuahua, Chih., Mexico. The use of carbon nanotubes (CNTs) as raw material for the production of metal matrix composites has attracted the attention of crescent numerous or researchers. This is due to the exceptional mechanical properties that CNTs possess [1]. Their use in the production metal-based composites is being widely investigated. Several routes for the CNTs dispersion into aluminum matrix composites have been employed, nevertheless, it is by mechanical milling (MM) process that a well dispersion has been achieved [2]. In this work, an Al-2024 (Al

Dispersion of CNTs in Aluminum 2024 Alloy by Milling Process

Elemental powders and carbon nanotubes (CNTs) were mixed and milled in a high energy shaker mill (SPEX-8000M), to produce 2024 aluminum (Al2024) matrix composites reinforced with CNTs. Milled products were consolidated by uniaxial load pressing followed by pressure-less sintering under argon atmosphere for 2 h at 773 K. The effect of CNTs concentration and milling time on Vickers microhardness (µHV) was studied. Scanning electron microscopy (SEM) micrographs show that by milling process it is possible to obtain a homogeneous dispersion of CNTs into the aluminum matrix. The mechanical properties of the composites show an important improvement with respect to reference samples. The possible strengthening mechanisms are discussed in the present work.

Mechanical Study on Al-based Composites Synthesized by Mechanical Milling and Hot Extrusion

Al-based composites were fabricated by solid-state route and were characterized by optic and scanning electron microscopy in order to follow their microstructural evolution. Composites were prepared using powder metallurgy techniques in order to obtain samples to carry out mechanical tests on hot extruded and machined samples. Microstructural characterization reveals that, by milling, a homogeneous dispersion of insoluble particles into Al matrix is obtained; this produced an important improvement on hardness and strength compared with the reference. Milling intensity and particle concentration have an important effect on the mechanical properties of composites.

Microstructural Characterization in Al-C-Al2O3 Composites Produced by Mechanical Milling

Aluminum-graphite-copper (Al-C-Cu) novel micro-composites have been produced using the Mechanical Alloying process (MA). The mechanical properties of the obtained composites have been evaluated. Yield strength (σy) values reached in the composites are considerably higher than those reported for pure aluminum. There is a direct relationship between σy and final graphite content in the composite. σy values increase as the nominal C content increases as well. We found that the most important hardening element was the graphite. We found that the optimal ratio Cu/C correspond to 0.33% for different volume fractions of graphite and cooper. There is an apparent synergy effect in σy between Cu and C. Results of TEM analysis have shown the presence of alumina particles in fiber shape from oxide surface of powder. Presence of alumina fibers in the composite improves the mechanical properties.