Microstructure Investigation of Cu-Ni Base Al 2 O 3 Nanocomposites: From Nanoparticles Synthesis to Consolidation
- PDF / 3,740,616 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 55 Downloads / 188 Views
INTRODUCTION
ALLOYS of Cu-Ni system have attracted both industrial and scientific community attention because of its remarkable chemical and physical properties.[1–4] Some applications, however, require improvements in mechanical properties which are conventionally achieved by means of thermomechanical processes, reaching a limited reduction in grain size and, thereby, increasing its yield strength.[5] On the other hand, metal-matrix composites with a fine dispersion of ceramic particles have been widely produced as an alternative for alloy hardening.[6–9] Reports in metal-matrix composites with ceramic reinforcing phase describe optimum volume fractions, as high as 10 to 15 pct, resulting in improved hardness, as is the case for Cu-CNT nanocomposites.[10,11] However, even lower volume fractions of ceramic component, as low as 1 pct, can significantly improve hardness.[12] Specific applications of this type of composites can be either in welding or electronic devices as the presence of alumina in the metal matrix can improve mechanical and thermal
M.I. RAMOS, N.M. SUGUIHIRO1, E.A. BROCCHI, R. NAVARRO, and I.G. SOLORZANO are with the Department of Chemical and Materials Engineering, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro, RJ, 22451-900, Brazil. Contact e-mail: [email protected] METALLURGICAL AND MATERIALS TRANSACTIONS A
properties, respectively, without prejudicing the necessary electrical behavior. An important factor in successfully producing good performance metal-matrix composites is the homogeneity of the dispersive phase. In order to obtain an isotropic composite material, it is mandatory to develop production routes which enable the hard ceramic phase to be distributed in an entirely random fashion within the metallic matrix. Among known synthesis methods for producing nanocomposites, the ones based on heterogeneous reactions (liquid–solid, gas–solid) are attractive for leading to a fully homogeneous dispersion of second phases in nanostructured metallic matrix, which, in turn, heavily depends on the careful control of the process conditions. In this approach, recent results support the possibility for alloy production starting from decomposition of water solution of metallic nitrates, followed by reduction in proper atmospheres, as reported for several alloy systems, such as Cu-Ni,[13–15] Ni-Co,[16,17] Fe-Ni.[18] Therefore, in order to obtain nanostructured Cu-Ni alloy with improved mechanical properties, CuNi-Al2O3 nanocomposites were prepared by thermal decomposition of Cu, Ni, and Al nitrates solution, followed by selective hydrogen reduction of the formed Cu and Ni oxides and finally by consolidation under pressure. Since microstructure governs the materials physical properties, a systematic microstructural characterization was carried out with intermediate and final compounds obtained at each processing step. Alongside some data
obtained from thermodynamic and kinetic studies, the consistent results served to select some variables used in the synthesis process. X-ray diffraction (XR
Data Loading...
