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Ultra-high-temperature ceramics (UHTCs) are a type of refractory ceramics that can withstand extremely high temperatures without degrading, often above 2,000 °C. [1] They also often have high thermal conductivities and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking.
SiC–SiC composites have a relatively high thermal conductivity and can operate at very high temperatures due to their inherently high creep and oxidation resistance. Residual porosity and stoichiometry of the material can vary its thermal conductivity, with increasing porosity leading to lower thermal conductivity and presence of Si–O–C ...
The European Commission funded a research project, C 3 HARME, under the NMP-19-2015 call of Framework Programmes for Research and Technological Development in 2016-2020 for the design, manufacturing and testing of a new class of ultra-refractory ceramic matrix composites reinforced with silicon carbide fibers and Carbon fibers suitable for applications in severe aerospace environments.
Conventional ceramics are very sensitive to thermal stress because of their high Young's modulus and low elongation capability. Temperature differences and low thermal conductivity create locally different elongations, which together with the high Young's modulus generate high stress. This results in cracks, rupture, and brittle failure.
Thermal conductivity is a common property targeted for maximization by creating thermal composites. In this case, the basic idea is to increase thermal conductivity by adding a highly conducting solid (such as the copper mesh or graphite [25]) into the relatively low-conducting PCM, thus increasing overall or bulk (thermal) conductivity. [26]
Very high thermal conductivity measurements up to 22,600 w m −1 K −1 were reported by Fenton, E.W., Rogers, J.S. and Woods, S.D. in reference 570 on page 1458, 41, 2026–33, 1963. The data is listed on pages 6 through 8 and graphed on page 1 where Fenton and company are on curves 63 and 64.
Design variables are limits imposed on the design, such as how thick the beam can be or how much it can deflect; Next, an equation for the performance index is derived. This equation numerically quantifies how desirable the material will be for a specific situation. By convention, a higher performance index denotes a better material.
The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by , , or and is measured in W·m −1 ·K −1. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity.