EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Novel eco-friendly method of preparation of Al2O3-AlN (AlON) composite ceramics was investigated using Hot isostatic pressing (HIP) technique. AlON ceramics are being investigated since 1980’s for their high strength and optical properties. Traditional synthesis of AlON ceramics include reactive sintering, carbothermal synthesis or spark plasma sintering. However, these technologies fail yielding a denser and transparent AlON ceramics. As an alternative pressing technology was employed and HIP technique was used in the present study to obtain better quality AlON ceramic. HIP requires shorter processing times and lower temperatures compared to sintering techniques and provides an exciting prospect. The precursor materials – AlN powder (0.80 – 1.8 µm diameter) was oxidized in ambient atmosphere for 3, 6 and 10 hours respectively. The oxidized powder was then subjected to HIP at 20 MPa, 1700 °C under N2 environment for 5 hours. The sintered samples were investigated using TEM and XRD for qualitative analysis. The phase transformation of AlN powder to Al2O3 during oxidation was observed proportional to the oxidation time. XRD analysis of the oxidized powders identified formation of α-Al2O3 and θ-Al2O3 phases. HIP Sintering has resulted in increasing the apparent density of the samples. Mechanical tests were also conducted on the sintered samples. Both 3-point and 4-point bending tests have shown an increase in the mechanical strength of the substrates with increasing oxidation time. Hardness of the substrates was also shown to be increased when compared to reference AlN with the highest hardness value obtained for the substrate with 10 hours oxidation time.