Single-source-precursor Synthesis And Properties Of SiC-based Ceramic Nanocomposites

The nanocomposites have received increasing interest in recent years,because an enormous improvement in their properties(e.g.mechanical,electrical,etc.)can be achieved when reducing the size of the components within the composite materials towards the nanoscale.One of the most suitable preparative routes towards ceramic nanocomposites was shown to rely on the polymer-derived ceramic(PDC)route since the chemical composition,phase composition and even the microstructures of ceramic nanocomposites can be designed and tailored.In this article,based on the polymer-derived ceramic route,the preceramic precursor allylhydridopolycarbosilane(AHPCS)were modified by both boron and transition metal through chemical reaction,the high temperature stability and electromagnetic microwave absorption properties of final ceramic nanocomposites were investigated.The synthesis of single-source-precursor,polymer-to-ceramic transformation of the resultant single-source-precursor as well as crystallization,microstructure,high temperature stability and the electromagnetic microwave absorption properties of final nanocomposites were investigated.The main results are as follows:Firstly,a series of ATP precursors with different Ti and B contents were synthesized by using AHPCS,pyridine borane(PB)and tetrabutyl titanate(TBT)as raw materials,and then TiB2-TiC-SiC ceramic nanocomposites were fabricated by PDC route.Result shows that the ceramic nanocomposites have a uniform microstructure.However,the high oxygen content results in the significant weight loss after aneanlling the ceramic at high temperature.It is worth mentioning that the ceramic nanocomposites are promising electromagnetic absorbing materials,with a-39dB minimum reflection loss coefficient and a narrow effective absorption bandwidth.Secondly,the ZrC-ZrB2-SiC nanocomposites were synthesized by a single-source-precursor route starting from the AHPCS as a SiC precursor and the TEAB as a source of B and Cp2ZrCl2 as a source of Zr.Result shows that ABZ precursor is a high ceramic yield precursor,with a 85wt%ceramic yield at 1000?.The ZrC-ZrB2-SiC nanocomposites have a uniform microstructure.Morever,the nanocomposites showed good high temperature stability,only 7.7wt%weight loss after annealing the nanocomposites at 1800? for 2h.However,ceramic nanocomposites do not perform well in microwave absorption.Thirdly,a series of ATPD precursors with different diethylbenzene(DVB)amount were synthesized by using AHPCS,DVB,PB and TBT as raw materials,and then the carbon rich TiB2-TiC-SiC-C ceramic nanocomposites were fabricated by PDC route.Result shows that the introduction of DVB reduces the weight loss of final ceramics.And the microstructure shows that the structure of ceramic nanocomposites is uniform,and the ordered nano-carbon phase is distributed uniformly in the ceramic matrix,which could form the conductive network structure.The introduction of DVB greatly improves the microwave absorption properties of ceramic nanocomposites,with a-55dB minimum reflection loss coefficient and a wide effective absorption bandwidth(4.54GHz).