Fine-grained fly dense alumina ceramics acquired by two-step sintering in SPS

The article discusses a complex method for producing fine-grained, full-density ceramics based on aluminum oxide with a relative density of 99.9 % using Spark Plasma Sintering. A slightly agglomerated mesoporous γ-Al2O3 nanopowder with a crystallite size of 3 – 7 nm and a high specific surface area was synthesized using a modified sol-gel technique. Dense ceramic samples, with a relative density of 99.9 %theor, where obtained after sintering the obtained γ-Al2O3 nanopowders by the SPS technique. The sintered samples were obtained after a two-step sintering at 1500°C with an applied pressure of 80 MPa, and dwell time of 3 minutes. It has been observed that two-step sintering of the obtained materials using the SPS method allows the material to be densified not only at the macro level, but also at the scale of the α-Al2O3 crystal lattice. The method developed in this work for the production of dense alumina ceramics with a fine-grained microstructure is a combined process, which includes both the process of synthesis of weakly agglomerated γ-Al2O3 nanopowders, and an approach to their compaction after two-step sintering by the SPS technique. The following research methods were used to identify the resulting powders and ceramics samples: XRD, TEM, electron diffraction, SEM, N2 adsorption-desorption, BET, aerosol diffusion spectrometry, and SPS method.