High-temperature wave-absorbing ceramic containing hafnium, silicon, boron, carbon and nitrogen and preparation method and application of high-temperature wave-absorbing ceramic

The invention provides a preparation method of wave-absorbing ceramic containing hafnium, silicon, boron, carbon and nitrogen, and belongs to the technical field of wave-absorbing materials. The preparation method comprises the following steps: firstly preparing a hyperbranched polymer, then crosslinking with tetra (diethylamino) hafnium, introducing hafnium element into the hyperbranched polymer to form a hafnium-containing polyborosilazane precursor, and finally realizing conversion from the precursor to ceramic through pyrolysis. The hafnium-containing polyborosilazane precursor obtained by the method is controllable in structure, and the hafnium-containing silicon boron carbon nitrogen ceramic obtained by pyrolysis can generate an HfC phase, an SiC phase and an HfB2 phase during high-temperature annealing. The in-situ generated multiphase ceramic integrates high temperature resistance and wave absorbing performance. The minimum reflection coefficient of the SiBCNHf (25) ceramic is 11.1 GHz, the thickness