<![CDATA[Considering that the theme still lacks activity on issues related to the thermodynamic evaluation of UHTCs based on a comprehensive approach, the main objective of this review is to analyze the thermodynamic modeling of different types of UHTCs using the CALPHAD techniques and tools to ensure the presence of high-temperature properties, such as high melting points, high hardness, thermal shock resistance, etc. These properties are necessary requirements for UHTCs to be used for high-temperature aerospace missions and scientific instrumentation. Besides, our target is to evaluate the phase relationships in both the Zr/B, Hf/B, Ta/B, and Mo/B systems, as well as the Zr/C, Hf/C, Ta/C, Mo/C, and Zr/Hf/(Ta,Mo)/C systems. This evaluation aims to give new impetus to experimental research for new UHTCs in the above-mentioned binary and ternary systems to optimize the phase relations. It is important to note that the searches of systems using the CALPHAD technique for these systems are not included in the most known databases, and there is a current lack of experimental data in the Zr/Hf/(Ta,Mo)/C system. To achieve concrete accomplishments, the technical and specific aim of this review is to evaluate the thermodynamic properties, such as data of formation and heat capacity, and Gibbs energy of formation, as well as phase stability in various systems based on ZrC, HfC, TaC, MoC, and UHTCs. This evaluation will be done utilizing the CALPHAD techniques, such as calculations of activities of binary and ternary systems and section-type mapping of the phase equilibria.]]>
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