Glass infiltration in an experimental ATZ ceramic composite reinforced with Al2O3 whiskers

Abstract

This study evaluated the development and characterization of alumina-toughened zirconia (ATZ) composites containing 10 wt% Al₂O₃ whiskers subjected to the glass infiltration. To obtain ATZ 90/10 composites, the commercial 3Y-TZP powder was mixed with synthesized alumina whiskers and subsequently compacted. Discs (n = 210) were pre-sintered at 1000 °C for 1 h. The infiltration of glass (68SiO₂-11.7Al₂O₃-3CaO-7.3Na₂O-10K₂O) was developed by mixing glass and propylene glycol, which was then applied onto ATZ pre-sintered specimens. For infiltration, the graded discs were divided into two different sintering protocols: protocol 1 (1550 °C for 2 h) and protocol 2 (1350 °C for 1 h followed by 1550 °C for 2 h). As a control group, non-infiltrated specimens were sintered using protocol 1. The specimens were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. Hardness, fracture toughness, and biaxial flexural strength tests followed by fractographic analysis were performed. Statistical analyses were conducted using Weibull distribution to calculate the material's modulus (m) and characteristic strength (95% CI), as well as ANOVA tests. High-aspect ratio alumina whiskers (10 μm × 200 nm) were synthesized. While the control group's XRD patterns evidenced only characteristic tetragonal zirconia and α−alumina peaks, the glass-infiltrated groups did not present characteristic peaks of crystalline materials. ATZ with alumina whiskers showed higher fracture toughness and characteristic strength compared to conventional ATZ. Furthermore, glass-infiltration improved the characteristic strength of conventional ATZ with no significant differences observed in the Weibull modulus. For W-G-2, C, and W groups the fractures originated at the zirconia surface, while for C-G-1-, C-G-2, and W-G-1 the origins were inside the ceramic microstructure. In conclusion, the development of ATZ with alumina whiskers increased the biaxial flexural strength and fracture toughness compared to conventional ATZ. The glass gradation significantly improved the characteristic strength of conventional ATZ regardless of the sintering protocol used, whereas it only improved the characteristic strength of whisker-reinforced ATZ when a single sintering was performed. Additionally, the sintering protocol influenced the thickness and amount of glass gradation in the composites.