| Abstract |
| The alloying behavior of Ni-Co-Cr nano-sized powders was studied via a polymer solution approach as a substitute method for mechanical alloying processes. Metal nitrate salts were dissolved in distilled water with a 5 wt% polyvinyl alcohol (PVA) solution, and the homogeneous sols were dried to gels and heated under a reducing atmosphere consisting of an argon-hydrogen (Ar-N2) gas mixture. In this study, the effects of processing parameters, specifically PVA content, composition of the gas mixture, and heating temperature, on alloying behavior were examined. The PVA ensured a homogeneous distribution of metal ions in the solution and it resulted in nano-sized metal particles after heating at 500 ℃. In particular, nano-sized Ni particles were oxidized when they were exposed to air after the heat treatment. However, a Ni-Co alloy was observed at higher heating temperature of 700 ℃, showing significant particle growth. Nano-sized Cr particles were not alloyed and instead oxidized to Cr2O3, showing a relative smaller particle size when they were exposed to air after heating at 700℃ and higher. In general, the metal particle sizes decreased as the H2 concentration increased in the gas mixture. (Received December 08, 2014) |
|
|
| Key Words |
| alloys, powder processing, crystallization, transmission electron microscopy, TEM, polymer solution route |
|
|
 |
|
