| Thermo-structure parts of ultra high temperature ceramic(UHTC) matrix composites have the advantages of high melting point, high conductivity, good mechanical properties and better anti-oxidation capabilities than that of C/C composites in the aerospace and weapon equipment fields. The thermal radiation properties of UHTC matrix composites are the most important reference datum for use and the key parameters for the design of the thermal protect systems. It will severely influence the working efficiency and using life of UHTC matrix composites.In this paper, the effects of temperature, surface behavior, component of the material, heat treatment and oxidation at high temperature on UHTC matrix composites were studied. Theoretical calculations of the emissivity of material surface were shown that the emissivity of material surface decreases with the temperature increases.The emissivities of ZrB2+20vol%SiC, ZrB2+20vol%SiC+3vol%Si3N4 composites on different bands were tested. The effects of surface attribute on the heat radiation of UHTC were analyzed. It is shown that after polished, the reflection of composites increased and the emissivity decreased obviously. After heat treatment , there was ZrO2,SiO2 film formed on the material surface. Meanwhile, the total emissivity of UHTC composites increased. The emissivity of ZS, ZSN composites in the range of 0.75~1.1μm infrared band were measured. It was indicated that the emissivity of ZSN was much lower than that of ZS composites.On the base of lots of experiments and theoretical derivation, the radiation mechanics of UHTC material was analyzed. In the preselected temperature ranges, the radiation properties of materials were studied by using dynamic and static test. The conclusions of the factors of the radiation properties were gained. On the analysis of the radiation for releasing heat, the mechanism of the thermal exhaustion of the material was demonstrated. And the heat-protection efficiency of the material was measured and evaluated.
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