2020 年 67 巻 7 号 p. 381-390
In order to fabricate dense ZrO2-Al2O3 ceramics by pressure-less sintering, three kinds of granules of calcined neutralization co-precipitated 75 mol% ZrO2(2.0 mol%Y2O3)-25 mol%Al2O3 powders added with a small amount of cellulose nanofiber (CNF), i.e., (2, 2, 6, 6-tetramethylpiperidine 1-oxyl)-oxidized (TEMPO) CNF, non-oxidized CNF and polyvinyl alcohol (PVA) were prepared and compacted. Then, they were sintered at 1523 K for 8.64·104 s in air. The granules prepared via the addition of 0.15 mass% TEMPO-CNF revealed a low relative density Dr for powder compacts (43.0%), however, they showed the highest Dr (99.8%) of sintered ceramics with the excellent mechanical properties, i.e., Vickers hardness Hv of 15.4 GPa, fracture toughness KIC of 18.2 MPa·m1/2 and bending strength σb of 882 MPa. These properties are almost the same as those fabricated by pulsed electric-current pressure sintering (PECPS). This might be explained in terms of i) the charged 1st particles induced by TEMPO-oxidized CNF addition could form the nano meter-gap between the primary particles in the granules, and then ii) this nano meter-gap could suppress the particle-sintering at relatively low temperatures, and then much densification at high temperatures could be achieved.
