Combustion Synthesis of Mullite/Metal Boride Composites
Formation of composite materials composed of mullite (3Al2O3×2SiO2) and transition metal borides (NbB2 and TaB2) was studied by self-propagating high-temperature synthesis (SHS). Starting materials included not only metal oxides (Nb2O5 and Ta2O5) and boron oxide (B2O3) as the sources of metallic elements and boron, but also Al and Si powders as the reducing agents. The evolution of mullite from in situ formed SiO2 and Al2O3 and synthesis of NbB2 and TaB2 were investigated. The effect of excess Si addition was studied on the combustion temperature, flame-front propagation velocity, and phase composition of the final product. For formation of the NbB2/mullite composites, the combustion velocity about 2.5 mm/s and reaction temperature around 1500 oC decreased slightly as the Si content increased. However, a considerable decrease in combustion front velocity from 2.74 to 1.43 mm/s and in reaction temperature from 1600 to 1250 oC was observed for the production of the TaB2/mullite composites. The XRD patterns of the final products confirmed the role of excess Si in the improvement of silicothermic reduction of B2O3 and subsequent evolution of NbB2, TaB2, and mullite. The EDS analysis indicated an atomic proportion close to that of 3Al2O3×2SiO2 for the mullite grains synthesized in this study.
H. Schneider, J. Schreuer, and B. Hildmann, “Structure and properties of mullite-A review,” Journal of the Euro. Ceramic Society, vol. 28, no. 2, pp. 329-344, 2008.
I. Zake-Tiluga, V. Svinka, R. Svinka, and L. Grase, “Thermal shock resistance of porous Al2O3-mullite ceramics,” Ceramics International, vol. 41, no. 9, part A, pp. 11504-11509, November 2015.
N. M. Rendtorff, S. Gómez, M. R. Gauna, M. S. Conconi, G. Suarez, and E. F. Aglietti, “Dense mullite-zirconia -zirconium titanate ceramic composites obtained by reaction sintering,” Ceramics International, vol. 42, no. 1, part B, pp. 1563-1572, January 2016.
D. Ghahremani, T. Ebadzadeh, and A. Maghsodipour, “Densification, micro- structure and mechanical properties of mullite-TiC composites prepared by spark plasma sintering,” Ceramics International, vol. 41, no. 2, part A, pp. 1957-1962, March 2015.
Z. I. Zaki, “Combustion synthesis of mullite-titanium boride composite,” Ceramics International, vol. 35, no. 2, pp. 673-678, March 2009.
A. G. Merzhanov, “Combustion and explosion processes in physical chemistry and technology of inorganic materials,” Russian Chem. Rev., vol. 72, pp. 289-310, 2003.
K. Morsi, “The diversity of combustion synthesis processing: a review,” Journal of Materials Science, vol. 47, no. 1, pp. 68-92, January 2012.
C. L. Yeh and J. Z. Lin, “Combustion synthesis of Cr-Al and Cr-Si intermetallics with Al2O3 additions from Cr2O3-Al and Cr2O3-Al-Si reaction systems,” Inter- metallics, vol. 33, pp. 126-133, February 2013.
Copyright (c) 2016 Proceedings of Engineering and Technology Innovation
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
Submission of a manuscript implies: that the work described has not been published before that it is not under consideration for publication elsewhere; that if and when the manuscript is accepted for publication. Authors can retain copyright in their article with no restrictions. Also, author can post the final, peer-reviewed manuscript version (postprint) to any repository or website.
From Oct. 01, 2015, PETI will publish new articles with Creative Commons Attribution Non-Commercial License, under Creative Commons Attribution 4.0 International Public License.
The Creative Commons Attribution Non-Commercial (CC-BY-NC) License permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes