Sintering Conditions and their Effect on Alumina's (α-Al2O3) Mechanical Properties

The current study explores the influence of sintering conditions on alumina derived through natural sintering. The nanopowder employed as the starting material was α-alumina (α-Al2O3), sourced from Baikowski (Baikalox-BMA15, France), boasting a purity of 99.99 % and an average particulate size of 150 nm. A wet process was utilized to prepare the slip, with 24 hours facilitating the deagglomeration of 50 g of Alumina powder. To eliminate potential contamination, the slip was cast within PVC molds and positioned on an alumina support. A comprehensive drying cycle was meticulously conducted to reduce the likelihood of cracking. This included steps such as boiling water, silica gel, dry medium exposure, oven treatment, and finally, a furnace. To negate the influence of organic additions and remnant gaseous species, the slip underwent a debinding process at 600 °C.The sintering process was executed at varying temperatures ranging from 1200-1500 °C, with 100 °C intervals, and holding durations of 1h and 3 h. The Grindo-Sonic device was applied to measure Young’s modulus using a dynamic method, whereas the mechanical strength was ascertained through a four-point bending test. Samples sintered for 3h and 1h demonstrated breaking strengths of 352 and 641 MPa and 164 to 528 MPa respectively. Additionally, porous samples were fabricated using 5 % wheat starch as a porogen. The porosity within 1 h and 3 h varied between 0.01 %-0.18 %, and 0.01%- 0.1% respectively, whereas, for porous samples, the porosity fluctuated between 0.1%-0.35%. The results showed that the samples sintered for a holding time of 3 h were denser than those sintered for 1 h. A 100% dense sample was achieved at 1400°C for 3h. The analysis revealed that a longer holding duration of 3h resulted in superior mechanical properties.