Fig. 5: Sintering of the nanograined alumina ceramics.
From: High-surface-area corundum nanoparticles by resistive hotspot-induced phase transformation
a Picture of the carbon papers during heating, sintering, and cooling. b Real-time temperature measurement during the alternating current sintering (ACS) process. c Grain size distribution of the alumina ceramic by ACS sintering using the α-Al2O3 NPs as precursor. Inset, scanning electron microscopy (SEM) image of the ceramic. d Grain size distribution of the alumina ceramic by two-step pressureless sintering (TS-PS) using the α-Al2O3 NPs as precursor. Inset, SEM image of the ceramic. e Grain size distribution of the alumina ceramic by TS-PS using the commercial α-Al2O3 nanopowders as precursor. Inset, SEM image of the ceramic. f Hardness distribution of the alumina ceramics by TS-PS process using the α-Al2O3 NPs (red) and commercial α-Al2O3 nanopowders (blue) as precursors. The dot within the box indicates the median, and the range indicates the 1.5IQR. The hardness of commercial standard alumina46 (10.5–12.7 GPa, lower band) and single-crystal sapphire50 (15.2–17.4 GPa, upper band) are labeled as reference.
