Autor: ROBERTO MARTINEZ SANCHEZ

Carbon-coated silver nanoparticles dispersed in a 2024 aluminum alloy produced by mechanical milling

ROBERTO MARTINEZ SANCHEZ (2009)

Aluminum-based nanocomposites were produced by dispersing different contents of carbon-coated silver nanoparticles (Ag-C NP) into a 2024 aluminum alloy (Al2024). After milling nanostructures about 100 nm grain sizes were obtained. Increment in mechanical properties was observed in all composites synthesized. The reinforcement nanoparticles were distributed homogeneously into the Al2024 matrix by mechanical milling process. The yield strength (σy) and Brinell hardness (HB), of the nanocomposites increased as the nanoparticles content was increased as well.

Artículo

BIOLOGÍA Y QUÍMICA QUÍMICA

Simultaneous effect of mechanical alloying and arc-melting processes in the microstructure and hardness of an AlCoFeMoNiTi high-entropy alloy

ROBERTO MARTINEZ SANCHEZ (2015)

A nanostructured AlCoFeMoNiTi high entropy alloy was synthesized through the mechanical alloying process. Bulk samples were obtained by two different routes to compare the microstructural evolution and hardness behavior: sintering and arc melting. Through electron microscopy analyses the formation of Mo-rich and Ti-rich phases were identified in the melted sample, while Ti-rich nano-precipitates were observed in the sintered sample. A higher microhardness value was achieved on the sintered sample than for the melted sample. The disadvantage of porosity in the sintered sample in comparison to the melted one was overcome by the hardening effect produced by the mechanical alloying.

Artículo

High entropy alloys; Mechanical alloying; Arc melting; Microstructure BIOLOGÍA Y QUÍMICA QUÍMICA

Microstructural and hardness behavior of graphene-nanoplatelets/aluminum composites synthesized by mechanical alloying

ROBERTO MARTINEZ SANCHEZ (2014)

Graphene can be considered as an ideal reinforcement for the production of composites due to its outstanding mechanical properties. These characteristics offer an increased opportunity for their study in the production of metal matrix composites (MMCs). In this research, the studied composites were produced by mechanical alloying (MA). The employed milling times were of 1, 3 and 5 h. GNPs were added in 0.25, 0.50 and 1.0 wt% into an aluminum powder matrix. Milled powders were cold consolidated and subsequently sintered. Composites were microstructurally characterized with Raman spectroscopy and electron microscopy and X-ray diffraction. The hardness behavior in composites was evaluated with a Vickers micro-hardness test. A homogeneous dispersion of graphene during MA and the proper selection of sintering conditions were considered to produce optimized composites. The obtained results with electron microscopy indicate a homogeneous dispersion of GNPs into the aluminum matrix. Analyses showed GNPs edges where the structure of the graphene layers conserved after MA is observed.

Artículo

BIOLOGÍA Y QUÍMICA QUÍMICA

Metastability of Mechanically Alloyed and Spark Plasma Sintered Co50soTi50 Powder

ROBERTO MARTINEZ SANCHEZ (2000)

High purity cobalt titanium were equiatomically mixed and mechanically alloyed.

The microstructure and phase transformation occurred on the powder product during its

densification using the spark plasma sintering SPS technique were analyzed. CoTi and

CoTi2 intermetallic compounds formed after fast sintering. Although metastable CoTi2

undergoes partial CoTi transformation the lattice parameter and micro-Vickers hardness

of these sintered compounds show high stability when annealing from 973 to 1273 K.

The material thus prepared can be reliably used at these temperatures showing

excellent mechanical behavior.

Artículo

Mechanical Alloying Sintering Ti CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA OTRAS ESPECIALIDADES FÍSICAS OTRAS