Analysis of Thermal Explosion Process for Preparing Ferromagnetic Al₂O₃-based Cermets

Abstract

Ferromagnetic Al₂O₃-based cermets characterized by homogeneous dispersion of Co-Ni alloy particles were successfully prepared via thermal explosion. The differential scanning calorimeter (DSC) analysis was employed to investigate the reaction process of Al-CoO-NiO system. X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis on water-quenched samples were carried out for phase identification and microstructure observation, respectively. The results show that a solid state reaction between Al and CoO (NiO) occurs at about 939 K and the reaction of Al melt and CoO (NiO) leads to the ignition of thermal explosion. The Al₂O₃ initially added into the compact cannot only prevent the as-synthesized product from splashing under high combustion temperature, but also react with CoO (NiO) to form intermediate spinel phase (Co, Ni)Al₂O₄. The measured saturation magnetization and coercive force of synthesized ferromagnetic (Co, Ni)-Al₂O₃ cermets are 29 emu/g and 31 Oe, respectively.

Keywords:

• Cermet
• Magnetic
• Microstructure
• Phases
• Process
• Reaction
• Synthesis
• Thermochemical