EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Objetive
The main goal of this study is the analysis of the mechanical enhancement of creep resistance in reduced graphene-oxide (rGO) reinforced alumina ceramic composites and compare the results with those found in the same ceramics without this secondary phase.
Materials and methods
The materials studied have been: Al2O3, Al2O3 + 2 vol.% rGO and Al2O3 + 6.7 vol.% rGO.
All the materials have been prepared by a colloidal processing route and freeze drying in order to optimize the distribution of the secondary phase in the ceramic matrix and subsequently sintered by spark plasma sintering at 1300 ºC.
Raman spectroscopy was carried out in order to study the integrity of reduced graphene-oxide (rGO) before and after sintering and after the creep experiments. The microstructure of the samples was examined by high-resolution scanning electron microscopy (HRSEM).
The creep experiments of the specimens were performed in argon atmosphere using temperatures between 1200-1250 ºC and stresses between 9-300 MPa.
Results
Homogeneous dispersions of the powders have been obtained. The integrity of the rGO in these composites was proved. The average grain size was between ~ (0.5-1.0) μm and the shape factor in all the cases was equal to ~ 0.7.
The stress exponents were around 2, so grain boundary sliding (GBS) was identify as the main deformation mechanism in this kind of materials. All the composites of alumina exhibited systematically lower creep resistance compared to the pure alumina.
Conclusions
Fully-dense Al2O3 + rGO composites have been fabricated by SPS.
The analysis of the high-temperature mechanical properties allows conclude that rGO provided a lost in the creep resistance of materials.