| The directed metal oxidation (DIMOX$sp{rm TM}$) technique produces strong, fracture-tough and low-porosity polycrystalline ceramic-containing composites via oxidation or nitridation processes. The DIMOX$sp{rm TM}$ or nitridation process, as in the present study, was performed in oxygen or nitrogen. Aluminum was the parent metal, with additions of various elements to produce alloys which formed $alpha$-alumina or aluminum nitride as a ceramic matrix for residual Al.;The reaction rates of oxidation and nitridation are affected by dopants, temperatures and partial pressures of the vapor-phase reactants. Thermogravimetric analysis was used to assess the kinetics of oxidation. The microstructures of the reaction products were characterized by optical and scanning electron microscopy. The reaction products were identified by X-ray diffractometry. The growth process, revealed by an environmental scanning electron microscope, was recorded on a video tape. The products were tested for hardness. The physical properties of the doped aluminium alloys are considered in the explanation of possible reaction mechanisms. |
