Nanomechanical and microstructural characterization of a zirconia-toughened alumina composite after aging

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Lopes, A. C. O. ; Coelho, P. G. ; Witek, L. ; Benalcazar Jalkh, E. B. ; Genova, L. A. ; Monteiro, K. N. ; Cesar, P. F. ; Lisboa Filho, P. N. ; Bergamo, E. T. P. ; Ramalho, I. S. ; Bonfante, E. A.

• Document type: Journal article
• Source: CERAMICS INTERNATIONAL; v. 45, n. 7, p. 7-pg., 2019-05-01.

Abstract

This study's objective was to mechanically characterize and validate the synthesis method of a polycrystalline composite comprised of 80% alumina reinforced with 20% translucent zirconia (zirconia-toughened alumina, ZTA) and compare to an experimental translucent zirconia. Experimental ZTA (ZTA ZPEX 80/20) and translucent Y-TZP (ZPEX) green-state disc-shaped specimens were obtained via uniaxial/isostatic ceramic powder pressing technique. The discs were sintered using a predefined protocol after both sides of the discs were polished. The specimens were subjected to nanoindentation testing to acquire their elastic modulus (E) and hardness (H) before and after a simulated low temperature degradation (LTD) challenge. Subsequently, the fabricated discs had their 3D surface topographical (Sa/Sq) parameters assessed via interferometry before and after exposure to a simulated LTD aging protocol. The specimens were evaluated using X-ray diffraction (XRD) to assess the tetragonal-monoclinic phase transformation and via scanning electron microscopy (SEM) to evaluate the homogeneity of the surfaces and distribution of the grains. The apparent density was measured using Archimedes' principle. All of the data were statistically evaluated through repeated measures ANOVA following post-hoc comparisons using the Tukey test (p < 0.05). The XRD patterns indicated a higher increase in the monoclinic peak for ZPEX compared to ZTA ZPEX 80/20 aged. LTD aging did not have an effect on the surface roughness (Sa/Sq) for both groups (p > 0.05). A significant decrease in the E values after the aging protocol was observed for both groups (p < 0.01). While ZTA ZPEX 80/ 20 did not show statistically significant differences in the hardness values after the aging protocol (p = 0.36), ZPEX demonstrated a significant decrease in the H values (p = 0.03). For ZTA ZPEX 80/20, simulated LTD aging did not affect the tested properties, except for the E values. Although artificial aging did not affect the surface roughness of ZPEX, the E and H values significantly decreased after aging. (AU)

• FAPESP's process: 12/19078-7 - Development and processing of Al2O3-ZrO2 translucent composite for CAD/CAM monolithic prostheses: the effect of aging on biaxial flexural strength
• Grantee: Estevam Augusto Bonfante
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 16/18818-8 - Multi-User Equipment approved in grant 2012/19078-7: ElectroPuls E3000 Linear-Torsion All-Electric dynamic test instrument package
• Grantee: Estevam Augusto Bonfante
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 18/03072-6 - Experimental 70% Al2O3-30% ZrO2 composites: structural characterization and survival probability before and after aging
• Grantee: Ernesto Byron Benalcazar Jalkh
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 17/19362-0 - DEVELOPMENT, MECHANICAL AND OPTICAL CHARACTERIZATION OF 80% AL2O3 AND 20% ZRO2 ZTA COMPOSITES FOR CAD/CAM PROSTHESES
• Grantee: Adolfo Coelho de Oliveira Lopes
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• FAPESP's process: 16/17793-1 - Development and mechanical and optical characterization of 80% Al2O3 and 20% ZrO2 translucent composites for CAD/CAM monolithic prostheses
• Grantee: Adolfo Coelho de Oliveira Lopes
• Support Opportunities: Scholarships in Brazil - Master