Solid solution formation during spark plasma sintering of ZrB2–TiC–graphite composites. Issue 3 (15th February 2020)

• Record Type: Journal Article
• Authors: Istgaldi, Hamid; Shahedi Asl, Mehdi; Shahi, Peyman; Nayebi, Behzad; Ahmadi, Zohre
• Is Part Of: Ceramics international. Volume 46:Issue 3(2020)
• Page Start: 2923
• Page End: 2930
• Publication Date: 2020-02-15
• Subjects: Ultrahigh temperature ceramics -- Zirconium diboride -- Titanium carbide -- Spark plasma sintering -- In-situ reinforcement -- Nano-graphite; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2019.09.287
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Densification and mechanical behavior of graphite-free and graphite-doped ZrB2 –TiC composites were investigated. Spark plasma sintering was used to achieve near fully-dense composites. Microstructural and phase analysis were carried out via scanning electron microscopy and X-ray diffraction spectroscopy, to illustrate the sintering and toughening mechanisms in the fabricated samples. Results indicated that 1 wt% graphite nano-flakes can improve the hardness of the composite. However, 3% drop in relative density and ~6% decrease in indentation fracture toughness were observed. The formation of TiB2 and ZrC was verified in both TiC-contained composites, although B4 C was recognized as the byproduct of reactive sintering in graphite-doped composite. Moreover, the microstructural analysis and the peak shifts in XRD pattern indicated the formation of a solid solution between the ZrB2 and TiB2 phases. Higher hardness of the graphite-doped sample was also attributed to the formation of B4 C as a superhard interfacial phase. Toughening mechanisms as well as possible chemical reactions which result in the in-situ formed reinforcement phases were also discussed.