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Densification Behavior and Mechanical Properties of Niobium-Oxide-Doped Alumina Ceramics
A.M. Hassan1, M. Awaad2, F. Bondioli3, S.M. Naga2
1 Zagazig Uni., Faculty of Engineering, Materials Engineering Dept, 44519 - Zagazig, Egypt
2 National Research Center, Ceramics Dept, El-Bohous Str., 12622 - Cairo, Egypt
3 Department of Industrial Engineering, Parco delle Scienze 181/A, 43124 - Parma, Italy
received December 10, 2013, received in revised form January 10, 2014, accepted January 24, 2014
Vol. 5, No. 1, Pages 51-56 DOI: 10.4416/JCST2013-00045
Abstract
The densification behavior, microstructure and mechanical properties of high-purity α-Al2O3 doped with 0.25, 0.5 and 0.75 wt% Nb2O5 were investigated. The batches were uniaxially pressed at 220 MPa into discs and rectangular bars and pressureless-sintered at temperature ranging between 1500º and 1650 °C for 1 h. The phase composition of the sintered bodies was followed up with an x-ray diffractometer, while their microstructure was characterized with a scanning electron microscope. The mechanical properties in terms of Vickers hardness (HV1), three-point bending strength and fracture toughness were also measured. The results showed that the addition of Nb2O5 accelerated the densification parameters, reinforced and toughened the obtained bodies. The maximum values for the mechanical properties of the Nb2O5-doped alumina-based ceramics were 34.4, 35.5 and 29.5 % for bending strength, fracture toughness and Vickers hardness respectively, which are higher than those of the undoped and doped technical alumina.
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Keywords
Doping, alumina, niobia, microstructure, mechanical properties
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