ANALYSIS OF THE EFFECT OF POWDER SURFACE TREATMENT AND GRAPHENE OXIDE ADDITION ON AN Al2O3-BASED CERAMIC COMPOSITE SINTERED BY PECS
Name: MATHEUS RODRIGUES FURLANI
Publication date: 25/02/2026
Examining board:
Name |
Role |
|---|---|
| CARLOS ALBERTO FORTULAN | Examinador Externo |
| MARCELO BERTOLETE CARNEIRO | Presidente |
| SÉRGIO FRANCISCO DOS SANTOS | Examinador Externo |
Summary: Alumina-based ceramics are widely used in structural applications, such as cutting tools, due to their high hardness and chemical stability at high temperatures. However, their low fracture toughness and the difficulty in obtaining homogeneous microstructures limit their applicability. In this context, this work aimed to evaluate processing strategies to improve the microstructural homogeneity and toughness of Al2O3+3Y-ZrO2 (ZTA) composites sintered by pulsed electric current sintering (PECS). The study was divided into three stages. Stage 1 aimed to evaluate the effectiveness of oleic acid (OA) and ultrasonic bath treatment in improving the homogeneity of a powder composed of 80 vol.% Al2O3 and 20 vol.% 3Y-ZrO2. Surface modification of the powders was confirmed by FTIR through the identification of oleate groups. The powders were sintered at 1400 °C under 50 MPa, resulting in relative densities ranging from 97.76% to 98.56%. The sample treated with OA exhibited the best performance,
with a hardness of 1740 HV10, representing a 1% increase over the unmodified sample. Stage 2 aimed to evaluate microstructural homogeneity in ZTA composites containing 91 vol.% Al2O3 and 9 vol.% 3Y-ZrO2. After sintering, the samples exhibited relative densities above 98%, indicating full densification. The OA+US route was selected for Stage 3 because it presented the most homogeneous microstructure and, compared to the reference, increased the fracture toughness (KIC) from 3.22 to 3.43 MPa.m1/2, despite a reduction in hardness from 1750 to 1701 HV10. Stage 3 aimed to evaluate the effect of adding reduced graphene oxide (rGO) in contents ranging from 0.10 to 1.00 vol.% on ceramic properties. Raman spectroscopy showed an ID/IG ratio of 0.93 in the as-received rGO, increasing slightly to 1.01 after deagglomeration and remaining at 1.00 after PECS sintering, indicating no additional graphene structure degradation. The samples achieved full densification. Hardness reached 1779 HV10 for the 0.50 vol.% rGO sample, and KIC peaked at 4.18 MPa.m1/2 for the 1.00 vol.% rGO sample. These results indicate that surface modification and the addition of rGO improve the densification, hardness, and fracture toughness of ZTA composites sintered by PECS.
Keywords: ZTA; rGO; surface modification; PECS; hardness; fracture toughness.
