Tansy fruit mediated greener synthesis of silver and gold nanoparticles

Metal matrix composites consist of a metal or an alloy as the continuous matrix and a reinforcement that can be particle, short fiber or whisker, or continuous fiber. In this chapter, we first describe important techniques to process metal matrix composites, then we describe the interface region and its characteristics, properties of different metal matrix composites, and finally, we summarize different applications of metal matrix composites.

Metal Matrix Composites

Preparation and properties of Al2O3 nanoparticle reinforced copper matrix composites by in situ processing

Compressive and wear resistance of nanometric alumina reinforced copper matrix composites

In the present work, accumulative roll bonding (ARB) process was used as an effective alternative method for manufacturing high-strength, finely dispersed and highly uniform copper/alumina metal matrix composite (MMC). The microstructural evolution and mechanical properties of the Cu/15 vol.% Al 2 O 3 composite during various ARB cycles are reported. The produced MMC by nine ARB cycles showed a homogeneous distribution and strong bonding between particles and matrix without any porosity. Also, it was found that when the number of cycles increased, not only did elongation increase but also the tensile strength of the composite improved by 2.5 times compared to that of the annealed copper used as the original raw material. Strengthening in the produced composites was explained by strain hardening, grain refinement, reinforcing role of particles, uniformity, bonding quality and size of particles. The findings also revealed that after the first cycle, hardness rapidly increased, then dwindled and finally saturated by further rolling.

Application of ARB process for manufacturing high-strength, finely dispersed and highly uniform Cu/Al2O3 composite

Characterization of Cu–Al2O3 nano-scale composites synthesized by in situ reduction

Nanocomposite of Cu–Al 2 O 3 have been prepared through their nitrates by two processes, namely: (1) addition of CuO to aqueous solution of aluminum nitrate, and (2) dissolution of the nitrates of copper and aluminum in water, followed by decomposition to their oxides and then preferential hydrogen reduction of CuO for both processes 1 and 2. The composite powders (containing 0.5–5 wt.% of Al 2 O 3 ), prepared by both the routes have been found to have nanoparticles. The composite powders have been cold pressed into briquettes and sintered at 950 °C for 2 h. Studies on their microstructures have been carried out through X-ray diffraction (XRD), conventional and high-resolution transmission electron microscopy (CTEM and HRTEM) and quantitative scanning transmission electron microscopy (STEM) X-ray mapping. The composites prepared through both routes, have been found to contain a third phase (Cu x Al y O z ), possibly CuAlO 2 and/or CuAl 2 O 4 along with Cu and Al 2 O 3 phases. However, in the composite prepared by process 2, the Al and O were dispersed more homogeneously, maintaining a continuity in the matrix.

Identification of a third phase in Cu–Al2O3 nanocomposites prepared by chemical routes

Different nano-scale particles have been synthesized by alternative routes: nitrates dehydratation and oxide, or co-formed oxides, reduction by hydrogen. Chemical-based synthesis routes are described and thermodynamics studies and kinetics data are presented to support the feasibility for obtaining single-phase oxides and co-formed two-phase oxides. In addition, the reduction reaction has been applied to successfully produce metal/ceramic nanocomposites. Structural characterization has been carried out by means of X-ray diffraction and, more extensively, transmission electron microscopy operating in conventional diffraction contrast mode (CTEM) and high-resolution mode (HRTEM). Nano-scale size distribution of oxide particles is well demonstrated together with their defect-free structure in the lower range, around 20 nm, size. Structural features related to the synthesized nano-composites are also presented.

Alternative chemical-based synthesis routes and characterization of nano-scale particles

The effect of TIG welding on the mechanical behavior of Al–Li alloy 2091-T851 has been investigated by means of tensile and fatigue testing. Compared to the base alloy, as-welded joints were found to display significant reductions in both tensile and fatigue strengths and to suffer a drastic degradation in ductility. Such behavior is primarily related to the presence of large elongated R phase precipitates at the weld metal grain boundaries, which leads to intergranular crack propagation through that part of the joint. Substantial microstructural changes, though, can be induced in the weld metal by subjecting the welded joints to a post-weld T6 type heat treatment. This promotes dissolution of the R phase, thus enhancing the tensile properties as well as the fatigue strength, consistent with the predominance of transgranular fracture of the weld metal in the heat treated joints. Finally, the microstructural aspects presented above indicate that the weld metal is plastically more heterogeneous than the base alloy and therefore is expected to work-harden faster, which is borne out by the tensile test results.

I. G. Solórzano

Papers

Characterization of Cu–Al2O3 nano-scale composites synthesized by in situ reduction

Identification of a third phase in Cu–Al2O3 nanocomposites prepared by chemical routes

Alternative chemical-based synthesis routes and characterization of nano-scale particles

Effect of weld metal microstructure on the monotonic and cyclic mechanical behavior of tig welded 2091 Al–Li alloy joints

TEM Microstuctural Characterization of a 2091 (Al-Li-Mg-Zr) Alloy Subjected to Welding Operations