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Ayşe Şentürk_edited.jpg

Ayşe ŞENTÜRK, BSc. Student 

Metallurgical and Materials Engineering

Yıldız Technical University

 

aysesentrkk@gmail.com

 https://www.linkedin.com/in/ayşe-şentürk-530114196

 

Synthesis of ZrB2 Powders

Co-Supervisors: Oğuz Karaahmet & Emirhan Karadağlı

ZrB2 is one of the ultra-high temperature ceramic materials. ZrB2’s physical and mechanical properties are also anisotropic because of its anisotropic crystal structure. Strong covalent bonding makes its young moduli and hardness higher. [1] This ceramic can be used as metal crucibles and refractory lining metal owing to its chemical inertness and corrosion resistance to the molten metal attack. [1] ZrB2 has high hardness and this property makes it a good choice for cutting tools applications. Owing to its electrical conductivity it can be used as a high temperature electrode for aluminum electrolysis and semiconductor devices. [2] [3] ZrB2 powders can be synthesized by using three ways; reduction processes, chemical routes and reactive processes. [4] The limiting factor of commercial synthesis of the zirconium diboride powders are the high cost of elemental boron and the low production capacity. [5] According to the technique that is used for synthesis, the synthesis of several grams to kilograms of powders can be produced in a few minutes to hours. Also, in ZrB2 powders which are produced in laboratories via reaction route occur greater content of oxygen impurity (~2.4 wt.%), when compared to commercially available powders (0.9 wt.% for H.C. Starck Grade B). [6] [7]  In this study, we aimed to produce ZrB2 powders with optimum properties by using carbothermal and borothermal methods. Carbothermal reaction produces carbon-contaminated powders and is appropriate for materials with a C concentration of < 3wt.%. ZrB2 powders can be produced using this technique. This reaction is endothermic and it is only favorable thermodynamically (ΔG° < 0) at temperature greater than 1500°C. (ZrO2(c) + B2O3(l) + 5C(g) → ZrB2(cr) + 5CO(g)). If we consider the Borothermal reduction, at temperatures above 1600°C, borothermic reduction of ZrO2 yields pure ZrB2. Because it requires the loss of expensive boron in the form of boron oxide, this process is not cost-effective for commercial production. To achieve stoichiometric ZrB2, further boron must be supplied. (ZrO2(c) + 4B(c) → ZrB2(c) + B2O2(g))

 

[1]       M. R. Mirza, M. Asim, M. A. Mehmood, N. Tariq, and R. Muhammad, “Development of ZrB2 ultra high temperature ceramic (UHTC),” Proc. 2018 15th Int. Bhurban Conf. Appl. Sci. Technol. IBCAST 2018, vol. 2018-Janua, pp. 74–78, 2018, doi: 10.1109/IBCAST.2018.8312208.

[2]       W. G. Fahrenholtz and G. E. Hilmas, “Ultra-high temperature ceramics: Materials for extreme environments,” Scr. Mater., vol. 129, pp. 94–99, 2017, doi: 10.1016/j.scriptamat.2016.10.018.

[3]       E. Wuchina, E. Opila, M. Opeka, W. Fahrenholtz, and I. Talmy, “UHTCs: Ultra-High Temperature Ceramic materials for extreme environment applications,” Electrochem. Soc. Interface, vol. 16, no. 4, pp. 30–36, 2007, doi: 10.1149/2.f04074if.

[4]       W. G. Fahrenholtz, G. E. Hilmas, I. G. Talmy, and J. A. Zaykoski, “Refractory diborides of zirconium and hafnium,” J. Am. Ceram. Soc., vol. 90, no. 5, pp. 1347–1364, 2007, doi: 10.1111/j.1551-2916.2007.01583.x.

[5]       B. R. Golla, A. Mukhopadhyay, B. Basu, and S. K. Thimmappa, “Review on ultra-high temperature boride ceramics,” Prog. Mater. Sci., vol. 111, no. December 2015, p. 100651, 2020, doi: 10.1016/j.pmatsci.2020.100651.

[6]       R. Telle, “Boride and Carbide Ceramics,” Mater. Sci. Technol., 2006, doi: 10.1002/9783527603978.mst0120.

[7]       J. Zou, H. Bin Ma, A. D’Angio, and G. J. Zhang, “Tungsten carbide: A versatile additive to get trace alkaline-earth oxide impurities out of ZrB2 based ceramics,” Scr. Mater., vol. 147, pp. 40–44, 2018, doi: 10.1016/j.scriptamat.2017.12.033.