Sintering and densification behavior of nanoparticle-infiltrated alumina scaffolds

This study explores high-purity Alumina's sintering and densification behavior, specifically the CT3000 SG variation, which traditionally requires high temperatures for full densification. The goal is to lower processing costs by achieving densification at lower temperatures through nanoparticle infiltration. The process involves a two-step heat treatment and infiltration technique. Alumina scaffolds are initially bisque-fired at 1100 °C and then infiltrated with a polymer precursor solution containing Al+3 ions, followed by decomposition at 400 °C to precipitate alumina nanoparticles in the scaffold pores. Multiple infiltration cycles are performed to enhance density. The relative density of furnace-sintered pellets increases with decreasing heating rate and increasing sintering temperature in reference samples. Infiltrated samples and "P" pellets (formed by washing CT3000 SG Alumina loose powder with the polymer precursor solution) follow a similar trend, with higher infiltration numbers leading to increased relative density. However, "P" samples have lower relative densities than reference samples. In-depth analysis using a horizontal dilatometer reveals that the 15 times infiltrated scaffolds exhibit better densification due to early activation of nanoparticles, leading to neck formation, reduced porosity, and altered particle shape. On the other hand, "P" pellets fail to achieve sufficient densification compared to reference samples. In summary, this study investigates lowering the sintering temperature of Alumina by nanoparticle infiltration. It involves bisque firing, multiple infiltration cycles, and a polymer precursor solution. Results indicate that 15 times infiltrated scaffolds achieve better densification, while "P" pellets fall short of achieving adequate densification compared to reference samples.