Effect of starting powders on the sintering of nanostructured ZrO₂ceramics by colloidal processing

Abstract

The effect of starting powders on the sintering of nanostructured tetragonal zirconia was evaluated. Suspensions were prepared with a concentration of 10 vol.% by mixing a bicomponent mixture of commercial powders (97 mol.% monoclinic zirconia with 3 mol.% yttria) and by dispersing commercially available tetragonal zirconia (3YTZ, Tosoh). The preparation of the slurry by bead-milling was optimized. Colloidal processing using 50 µm zirconia beads at 4000 rpm generated a fully deagglomerated suspension leading to the formation of high-density consolidated compacts (62% of the theoretical density (TD) for the bicomponent suspension). Optimum colloidal processing of the bicomponent suspension followed by the sintering of yttria and zirconia allowed us to obtain nanostructured tetragonal zirconia. Three different sintering techniques were investigated: normal sintering, two-step sintering and spark plasma sintering. The inhibition of grain growth in the bicomponent mixed powders in comparison with 3YTZ was demonstrated. The inhibition of the grain growth may have been caused by inter-diffusion of cations during the sintering.

Two-Step Sintering of Ceramics

“…Fully dense ceramics with uniform microstructure and fine grain size is essential to stabilize the tetragonal phase as well as to improve the mechanical properties such as hardness and toughness. There are many TSS profiles conducted to control the grain growth of Y-TZP ceramics [1,4,5,8,[24][25][26][27][28][29][30][31]61]. Only few researchers successfully obtained fully dense ceramics with controlled grain growth (<5 times of powder size) [1,4,5,25,28,29,31,62].…”

“…Only few researchers successfully obtained fully dense ceramics with controlled grain growth (<5 times of powder size) [1,4,5,25,28,29,31,62]. Among these studies, Binner et al [31] and others [1,29] successfully sintered nanostructured zirconia ceramics. Binner et al [31] achieved fully dense (99% of TD) nanoceramics with the application of hybrid radiant and microwave sintering.…”

Highly Transparent Pure Alumina Fabricated by High‐Pressure Spark Plasma Sintering

“…Kim et al ., 4 in the case of alumina sintered at 1150°C under an applied pressure of 80 MPa, obtained an in‐line transmittance of 47% at a wavelength of 640 nm. As SPS typically operates with punches and die in graphite, the maximum pressure in the SPS method is generally limited by the compressive strength of the material used for the dies, which is 140 MPa for high‐strength graphite 8–10 …”

“…As SPS typically operates with punches and die in graphite, the maximum pressure in the SPS method is generally limited by the compressive strength of the material used for the dies, which is 140 MPa for high-strength graphite. [8][9][10] In 2006, Anselmi-Tamburini et al 11 reported a method for preparing dense functional oxide compacts with a crystallite size in the range of 10-20 nm. They used relatively short thermal cycles (o10 min) coupled with a progressive increase in pressure (up to 1 GPa) to promote a high degree of compaction and very limited grain growth.…”

Materiales nanoestructurados de zirconia: Materiales densos y compositos con nanotubos de carbono (NTC)

“…Con respecto a esto, los polvos con dimensiones de partícula del orden de los nanómetros están en desventaja debido a la facilidad a aglomerarse que tienen los mismos. Esto conduce a que en el material final existan poros intra e inter aglomerados, siendo los primeros a nanoescala, mientras que los últimos están a nivel submicrónico o incluso del orden del micrón, en especial cuando los polvos se aglomeran en diferentes escalas (Kim y Han, 2004;Suárez et al, 2009b).…”