Search

Cu–Ni/Al 2 O 3 nanocomposite powders were manufactured using an in situ chemical reaction technique. This technique provides improved wettability and adhesion between the matrix and reinforcement phases. Aluminum nitrate, copper nitrate and nickel nitrate were used as start materials for the production of the composites. The powders were sintered in a hydrogen environment at 900 °C for 2 h after being cold pressed at 700 MPa. To determine the effect of Al 2 O 3 on electrical and thermal conductivities and thermal expansion behaviors, the Cu–Ni matrix was supplemented with 3, 5, and 8 wt% Al 2 O 3. The findings revealed that Al 2 O 3 nanoparticles (20 nm) were dispersed uniformly throughout the copper-nickel matrix. Microhardness was improved from 53.3 HV for Cu–Ni matrix to 92.7 HV for Cu–Ni/8%Al 2 O 3 nanocomposites. The electrical and thermal conductivities and thermal expansion coefficient were reduced as the amount of Al 2 O 3 in the Cu–Ni matrix increased. The electrical conductivity was reduced by 38.7% by addition 5% Al 2 O 3 nanoparticles to Cu–Ni matrix. The high interfacial bonding between Cu–Ni and Al 2 O 3 nanoparticles was the main reason of the hardness improvement and maintaining relatively good electrical and thermal properties. [ABSTRACT FROM AUTHOR]

Chemical-based synthesis of co-formed oxide (CuO–NiO–Al 2 O 3) nanoparticles, followed by selective hydrogen reduction of the Cu and Ni oxides and ultimately consolidation into pellets, produced various compositions of Cu–Ni/Al 2 O 3 nanocomposites. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy analyses were used to characterize the powders. The generated powders ranged in size from 20 to 70 nm, with a considerable presence of agglomerates. According to SEM examination, the powders were homogeneous in shape and particle size. Cold pressed nanocomposite powders were sintered for 2 h at 950 °C. SEM with energy dispersive spectroscopy (EDS) was also used to study the microstructure of the sintered specimens. In addition, the physical and mechanical properties of sintered specimens were studied. When the Al 2 O 3 content increased, a more uniform distribution of nanosized Al 2 O 3 particles in the Cu–Ni matrix was attained, resulting in a reduction in particle size. The results also demonstrated that as the Al 2 O 3 concentration was raised, the microhardness and compressive strength of the nanocomposites rose by 74% and 67% compared to pure alloy, with the exception of fracture strain, which decreased dramatically. [ABSTRACT FROM AUTHOR]