Ultra-high temperature ceramics (UHTC) are materials rarely found in nature, characterized by high melting points, hardness, thermal conductivity (when compared to other ceramics), good resistance wear and mechanical resistance.1,2,3 Additionally, they are chemically and thermally stable under a variety of conditions due to their high negative free energy of formation.1,3Materials that fall within these criteria are ceramic compounds consisting of borides , nitrides and carbides. Due to such properties, this class of materials can be applied in extreme environments such as extreme temperatures, chemical reactivity and erosive attacks. For this reason, in the 1950s, studies began to analyze the possibility of using them to coat nuclear reactors but they also have the ability to function as an electrode for electric arc furnaces, manipulation of molten metals and for aerospace use (e.g. re-entry, hypersonic flight), the latter application has led to further investigation of UHTCs.3,4,5Nitrides and carbides tend to have lower thermal conductivity than borides (diborides have similar thermal conductivity to copper at room temperature), which means that boride compounds usually have higher thermal shock stability and good thermal stress response, so this essay will focus on this type of UHTC.3ZrB2 is a UHTC diboride which has a hexagonal crystal structure, as shown in figure 1. According to Fahrenholtz et al al., the crystal is organized by hexagonally packed layers of Zr alternating with layers of B atoms arranged in 2D graphite-like rings.1Figure 1 – Representation of the crystal structure of ZrB21A summary of the properties of ZrB2 is presented in Table 1.Table 1 – Prope ...... middle of sheet ......M. Gasch, JW Lawson, MI Gusman, MM Stackpoole, “Recent Developments in Ultra High Temperature Ceramics at NASA Ames” American Institute of Aeronautics and Astronautics (2009).4 A. Paul, DD Jayaseelan, S. Venugopal, E. Zapata-Solvas , J. Binner, B. Vaidhyanathan, A. Heaton, P. Brown, W. E. Lee, “UHTC composites for hypersonic applications” American Ceramics Society Bulletin, 91 [1] 22–30 (2012).5 E. Wuchina, E. Opila, M. Opeka, W. Fahrenholtz, I. Talmy, "UHTC: ultrahigh-temperature ceramic materials for extreme environment applications" The Electrochemical Society, 30-37 (2007).6 J.R. Fenter, ''Refractory Diborides as Engineering Materials ,'' SAMPE Quarter., 2, 1–15 (1971).7 AL Chamberlain, W. G. Fahrenholtz, GE Hilmas, and DT Ellerby, ''High Strength ZrB2-Based Ceramics,'' Journal of the American Ceramics Society, 87 [6] 1170–2 (2004).