摘要
A kind of silicon-and-boron-modified phenolic-formaldehyde resin(SBPF)with excellent thermal stability was fabricated via a simple two-step method and used for the matrix of ablation materials.The structure and thermal stability of the modified phenolic-formaldehyde resins(PFs)were characterised.The results showed that boron and silicon e lements have been incorporated into SBPF in the form of a chemical bond.Meanwhile,the cured products showed an increase in graphite structure and a decrease in disordered structure due to the incorporation of boron and silicon.Compared with the ordinary phenolic resin,the initial thermal degradation temperature and charring yield at 800℃ of SBPF increased by 73℃ and 15 wt%,respectively.Further,the modified PFs,nano-Al_(2)O_(3) powders,glass powders and vitreous silica fibres were used to obtain a novel cer amizable phenolic mou lding com posite.The morphology,chemical composition and ablative characteristics of the composites were explored.The results showed that a compact and homogeneous SiO_(2)-Al_(2)O_(3) layer formed on the ablated surface and protected the carbonised matrix and fibres from further oxidation.Compared with the ordinary PF composites,the SBPF composites showed a highly decreased linear/mass ablation rates,indicating the synergistic effect of boron and silicon modification on the enhanced ablation property.
基金
the research by N ational Natural Scientific Foundation of China(grants no.51522510,51675513 and 51735013).
