Characteristics of UHTC composites and coatings fabricated by reactive melt infiltration method

Reference	Presenter	Authors (Institution)	Abstract
14-062	Shaoming Dong	Dong, S.(Shanghai Institute of Ceramics, Chinese Academy of Sciences); Chen, X.(Shanghai Institute of Ceramics, Chinese Academy of Sciences); Xue, C.(Shanghai Institute of Ceramics, Chinese Academy of Sciences); Kan, Y.(Shanghai Institute of Ceramics, Chinese Academy of Sciences); Zhou, H.(Shanghai Institute of Ceramics, Chinese Academy of Sciences); Ni, D.(Shanghai Institute of Ceramics, Chinese Academy of Sciences);	Carbon fiber reinforced ultra high temperature ceramic matrix composites (Cf/UHTC) are candidate materials for thermal structural elements using in extreme environment, such as nozzles, nose tips and leading edges for hypersonic vehicles. As well, UHTC coatings are considered to be promising solution to improve oxidation resistance and high temperature resistance of some structure materials, such as C/SiC and C/C composites. In present study, Cf/ZrB2-ZrC-SiC ternary UHTC system composites were prepared by an improved reactive melt infiltration (RMI) method, which included a sol-gel process for preparing porous B-C preform and ZrSi2 melt infiltration process. It was found that the porosity and pore size of the preform showed significant effect on the RMI process and the properties of the composites. Lower porosity and smaller pore size led to better mechanical properties. The microstructures, phase assemblages and ablative properties of the materials were studied. Also, ZrB2-ZrC-SiC ternary system coatings on C/C composites were prepared by reactive melt infiltration (RMI) of ZrSi2 alloy into porous B-C pre-coatings fabricated by slurry dip. The coating presents a flat and smooth surface morphology with three layers cross structure namely interior SiC transition layer, gradient ZrB2-ZrC-SiC layer and ZrB2-ZrC exterior layer. Formation mechanisms of the specific microstructure of the coatings were investigated and discussed in detail.
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