No abstract

Cu-TiO 2 nanocomposite powders were synthesised by thermochemical process. The composite powders (containing 0, 2.5, 5 and 7 wt-% of TiO 2 ), prepared by spray drying of the (aqueous) solution of copper nitrate and titanium nitrate followed by heat treatment at 9008C for 1 h and reduction in hydrogen atmosphere at 5008C for 1 h. The composite powders were prepared by cold pressing and then sintering at 9008C for 1 h. Studies on their microstructures have been carried out through X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties and electrical conductivity of sintered specimens were measured, and the effect of TiO 2 content on these properties was investigated. The results showed that the nanosized TiO 2 particles (with a diameter of about 10-30 nm) was successfully formed and dispersed within the copper matrix. By introducing TiO 2 particles up to 2.5 weight percept, the electrical conductivity wastage is very high.

Alumina dispersion hardened copper-base composite was fabricated by internal oxidation method. The high temperature tensile fracture of Cu-Al2O3 composite was studied and tensile strengths were determined at different temperatures of 600, 680 and 780 °C. Microstructure was investigated by means of optical microscope and field emission scanning electron microscope (FESEM) with energy dispersive spectroscopy (EDS). Results show that, ultimate tensile strength and yield strength of copper alumina nanocomposite decrease slowly with increasing temperature. The yield strength reaches 119 MPa and ultimate tensile strength reaches 132 MPa at 780 °C. Surface fractography shows a dimple-type fracture on the fracture surface of the tensile tests where dimple size increases with increasing testing temperature and in some regions brittle fracture characteristics could be observed in the fracture surface.