Visualization of the Final Stage of Sintering in Nanoceramics with Atomic Resolution

Abstract

The deep understanding of the sintering mechanism is pivotal to optimizing denser ceramics production. Although several models explain the sintering satisfactorily on the micrometric scale, the extrapolation for nanostructured systems is not trivial. Aiming to provide additional information about the particularities of the sintering at the nanoscale, we performed in situ experiments using high-resolution transmission electron microscopy (HRTEM). We studied the pore elimination process in a ZrO2 thin film and identified a high anisotropic pore elimination. Interestingly, there is a redistribution of the atoms from the rough surface in the solid–gas surface, followed by the atom attachment in a faceted surface. Finally, we found evidence of the pore acting as a pin, reducing the GB mobility. These findings certainly can contribute to enhance the kinetic models to describe the densification process of systems at the nanoscale.

Influences of powder morphology on the densification and microstructure of a ZrO2‐based nanocrystalline glass–ceramic

“…The driving force of sintering is the reduction of free energy of the material system, 1 that is, the free energy of raw powder is higher than that of the sintered body, and free energy of the material system can be reduced by sintering process 30 . Raw powder with higher specific surface area (higher surface energy) can be densified at lower temperature compared with that with lower specific surface area (lower surface energy) 31 . The specific surface area of the 600°C‐calcined particle powder and 1100°C‐calcined fiber powder was 166.8 and 3.5 m 2 /g, respectively.…”

“…30 Raw powder with higher specific surface area (higher surface energy) can be densified at lower temperature compared with that with lower specific surface area (lower surface energy). 31 The specific surface area of the 600 • C-calcined particle powder and 1100 • C-calcined fiber powder was 166.8 and 3.5 m 2 /g, respectively. The particle powder had higher sintering driving force than that of the fiber powder, which resulted in lower T start and T end temperatures of the particle powder.…”