Preparation and characterization of polymer-derived SiBONC bulk ceramics by polymer-drived precursor method

SiBONC ceramic powders with specific structural characteristics and free boron oxide were designed at atom level, The preparation of polymer precursors synthesized by chloro-polysiloxane, alkyl-amine and boron trichloride to ceramic composite can provide control of the resulting microstructure as well as the desired uniform distribution of phase. Organo-polymeric precursors prepared by polymer precursor method are used to produce ceramic nano-powders through pyrolysis. The ratio of the Si:B is 80:20. The nano-powders was anneal through the hot-pressing method to form the composite ceramics. The features and morphologies of the produced ceramics were investigated by means of mechanics analysis, XRD, FT-IR, SEM and TEM techniques. Experimental results: the density of SiBONC ceramics is between 1.95 g/cm³ and 2.15 g/cm³, the flex strength maximizing 150.50 MPa, the Vickers-hardness is 3.78 GPa, the fracture toughness is 2.10 MPa.m^1/2. SiBONC ceramics can keep the amorphous state at 1700°C, even at 1800°C, the α-SiC can be crystallized from the matrix, the mean grain size is about 100 nm, which indicates that adulterates B, C, N at atom level can obvious increase the crystallize temperature and mechanical property of SiBONC ceramics. Therefore the thermal stability of SiBONC ceramics can be extraordinary increased.