Fabrication of translucent tetragonal zirconia by gelcasting of thin zirconia nano-slurry

Abstract

Microstructural evolution during the sintering of nanoceramics was investigated in the compacts prepared by gelcasting of tetragonal zirconia nano-slurry with the solid loading of 7 vol %. The initial compact prepared by the gelcasting in this study had the densely packed structure with a narrow pore-size distribution and high connectivity in the particle network. Special attentions were paid to the evolutions of pore structures in the initial and intermediate stage sintering. It was found that the coarsening of the pores, which is thought to be the important obstacle of the densification in nanoceramics, was not remarkable in the sintering of the densely packed compact. The suppression of the pore coarsening resulted in the lowering the sintering temperature. Almost fully dense sample with 99.5% of theoretical density was successfully obtained at the sintering temperature of 1373 K for 2 h. The sample sintered at 1373 K maintained the nanometric structure with the grain size of 79 nm and exhibited the optical translucency.

Pressureless low temperature sintering of nanocrystalline zirconia ceramics via dry powder processing

“…[36][37][38][39] Another approach employs wet ball milling to break up hard agglomerates, but dries the powder before compacting it leaving behind carbon-based molecules on the surface of the powder. 30,[37][38][39][40][41] While the application of pressure during sintering can alleviate the need for careful green body formation, powders sintered using Spark Plasma Sintering (SPS), Hot Press sintering, or post sintering Hot Isostatic Pressing often suffer discoloration and/or retain carbon in the final product as a result of the interaction between the ceramic and tooling of the apparatus. [42][43][44][45][46] In these cases, the powder processing or sintering technique can add contaminants, which can be retained in the dense ceramics and impact the bulk properties.…”

“…A common nanopowder processing technique for zirconia based samples is to disperse powder in water with or without dispersants to separate the nanoparticles and then slip cast the slurry into a shape which is slowly dried to remove the water . Another approach employs wet ball milling to break up hard agglomerates, but dries the powder before compacting it leaving behind carbon‐based molecules on the surface of the powder . While the application of pressure during sintering can alleviate the need for careful green body formation, powders sintered using Spark Plasma Sintering (SPS), Hot Press sintering, or post sintering Hot Isostatic Pressing often suffer discoloration and/or retain carbon in the final product as a result of the interaction between the ceramic and tooling of the apparatus .…”