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Microstructure and fracture mechanism investigation of porous silicon nitride-zirconia-graphene composite using multi-scale and in-situ microscopy

: Liao, Zhongquan; Standke, Yvonne; Gluch, Jürgen; Balazsi, Katalin; Pathak, Onkar; Höhn, Sören; Herrmann, Mathias; Werner, Stephan; Dusza, Jan; Balazsi, Csaba; Zschech, Ehrenfried

Fulltext ()

Nanomaterials 11 (2021), No.2, Art. 285, 13 pp.
ISSN: 2079-4991
Deutsche Forschungsgemeinschaft DFG
FLAG-ERA JTC 2017; 397380564
Multifunctional Ceramic/Graphene Thick Coatings for New Emerging Applications
Journal Article, Electronic Publication
Fraunhofer IKTS ()
EN; porous ceramic composite; contact-damage resistance; In-situ microscopy; multi-scale microscopy; GPS; high graphene content

Silicon nitride-zirconia-graphene composites with high graphene content (5 wt% and 30 wt%) were sintered by gas pressure sintering (GPS). The effect of the multilayer graphene (MLG) content on microstructure and fracture mechanism is investigated by multi-scale and in-situ microscopy. Multi-scale microscopy confirms that the phases disperse evenly in the microstructure without obvious agglomeration. The MLG flakes well dispersed between ceramic matrix grains slow down the phase transformation from α to β-Si3N4, subsequent needle-like growth of β-Si3N4 rods and the densification due to the reduction of sintering additives particularly in the case with 30 wt% MLG. The size distribution of Si3N4 phase shifts towards a larger size range with the increase of graphene content from 5 wt% to 30 wt%, while a higher graphene content (30 wt%) hinders the growth of the ZrO2 phase. The composite with 30 wt% MLG has a porosity of 47 %, the one with 5 wt% exhibits a porosity of appr. 30 %. Both Si3N4/MLG composites show potential resistance to contact or indentation damage. Crack initiation and propagation, densification of the porous microstructure, and shift of ceramic phases are observed using in-situ transmission electron microscopy. The crack propagates through the ceramic/MLG interface and through both the ceramic and the non-ceramic components in the composite with low graphene content. However, the crack prefers to bypass ceramic phases in the composite with 30 wt% MLG.