预氧化对zrb2-sic-g超高温陶瓷材料力学性能及抗热震性影响word论文.docx

Abstract
As one of non-ablative ultra-high temperature materials, ZrB2-based ultra-high temperature ceramics (UHTCs) which have excellent performance such as good oxidation resistance and low density, have been widely used in nose-cone, wing leading edge and other key parts of hypersonic vehicle. However, as one kind of ceramic materials, its ings of brittleness and low toughness affect the strength and thermal shock resistance of the material. Taking the application environment of hypersonic vehicle into account, there's a urgent need to improve the performance of materials.
The material used in this study was ZrB2-SiC-G ultra-high temperature ceramic. As the phenomenon of the different products and surface structures from the oxidation reactions of ZrB2-based UHTCs at different temperatures for research background, combined with the thermal shock theory, using the test and analysis method of three-point bending test, scanning electronic microscope(SEM) and water quenching-residual strength method, this paper analyses the effect of pre-oxidation treatment on the mechanical properties and thermal shock resistance of the materials, furthermore, we explore the process condition of pre-oxidation treatment.
First of all, we studied the effect of pre-oxidation temperature on the strength of materials. In the pre-oxidation temperature regions of 800~1100℃ and 1200~1500℃,
the products of oxidation healing the cracks were respectively B2O3 and SiO2, the best pre-oxidation temperatures were respectively 900℃ and 1400℃, the strength was
respectively increased by 56MPa and 24MPa. Then we studied the effect of pre-oxidation time (15min~2h) on the strength of materials. The samples pre-oxidized for 1h performed best. Based on the research on the effect of pre-oxidation on the mechanical properties, this paper further discussed the effect of pre-oxidation on the thermal shock resistance of materials. We studied the effect of pre-oxidation
temperature (1200~1500℃) on the the