Microstructure and properties of mullite–ZrO2 ceramics with silicon nitride additive prepared by spark plasma sintering
The process of densification and development of the microstructure of mullite–ZrO2/Y2O3 ceramics from mixture of Al2O3, SiO2, ZrO2 and Y2O3 by gradually adding of α–β Si3N4 nanopowder from1 to 5 wt% by traditional and spark plazma sintering were investigated by mean sof differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and some ceramic and mechanical properties. The processes of DTA for all samples are characterised by alow-pitched endo-effect, when gradual mullite formation and notice able densification at temperatures of 1200–1400 ⁰C is started. It is testified by shrinkage and density both for traditionally and by SPS-sintered samples. The influence of the Si3N4 additive on the density characteristics is insignificant for both sintering cases. For SPS samples, the density reaches up to 3.33 g/cm3, while for traditionally sintered samples, the value is 2.55 g/cm3, and the compressive strength for SPS grows with Si3N4 additives, reaching 600N/mm2. In the case of traditional sintering, it decreases to approximately100 N/mm2. The basic microstructure of ceramic samples sintered in a traditional way and by SPS is created from mullite (orpseudo-mullite) crystalline formations with the incorporation of ZrO2 grains. The microstructure of ceramic samples sintered by SPS shows that mullite crystals are very densely arranged and they do not have the characteristic prismatic shape. The traditional sintering process causes the creation of voids in the microstructure, which, with an increasing amount of Si3N4 additive, are filled with mullite crystalline formations.
Date
04.01.2019.
Keywords
SPS, Microstructure-final, Mechanical properties, Mullite, ZrO2, Y2O3, Si3N4
DOI
10.1016/j.ceramint.2015.10.112
Hyperlink
www.elsevier.com/locate/ceramint
