Review article
Comparison of Mechanical Properties of Conventionally and Non-Conventionally Sintered Cold Isostatically Pressed Al2O3 Ceramics
Lidija Ćurković
; Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb
Ivana Ropuš
; Energoatest zaštita d.o.o., Potočnjakova 4, 10000 Zagreb, Croatia
Irena Žmak
; Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb
Ivana Gabelica
; Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb
Zrinka Švagelj
; Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb
Abstract
The objective of this study was to investigate and compare the morphology and mechanical properties of cold
isostatically pressed (CIP) alumina (Al2O3) samples sintered by conventional (electrical) and non-conventional
(hybrid microwave) techniques. Scanning electron microscopy (SEM) was used to examine the morphology of the
Al2O3 ceramics sintered by both sintering techniques. Following mechanical properties of CIP alumina ceramics were
analysed: (i) Vickers hardness, (ii) Vickers indentation fracture toughness (VIF), (iii) the indentation size effect (ISE)
using Vickers method, and (iv) the brittleness index. The ISE is analysed using (i) the Meyer’s law, (ii) the proportional
specimen resistance (PSR) model, and (iii) the modified proportional specimen resistance (MPSR) model. It was found
that alumina samples sintered in the electric kiln obtained higher density and lower porosity compared to the samples
sintered in the hybrid-microwave kiln. The obtained values of the Meyer’s index n are less than 2 for alumina ceramics
sintered by both sintering methods, which indicates that the hardness is dependent on the test load. High correlation
coefficients confirm that all applied mathematical models are suitable. However, true Vickers hardness obtained by the
PSR model was found to be nearer to the measured Vickers hardness of alumina samples regardless of the sintering
method applied. Furthermore, it was found that the fracture toughness was higher for alumina ceramics sintered in
the hybrid microwave kiln (MK-Al2O3) than the one sintered in the electric kiln (EK-Al2O3). In contrary, the brittleness
index was found to be higher for alumina ceramics sintered in the electric kiln (EK-Al2O3) than in the hybrid microwave
kiln (MK-Al2O3). Both Vickers hardness and brittleness index values might be correlated to the microstructure of the
sintered samples, e.g. finer for non-conventionally sintered alumina.
Keywords
alumina ceramics, sintering, mechanical properties
Hrčak ID:
270509
URI
Publication date:
1.11.2021.
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