Study On The Preparation And Properties Of SiCw/ZrBr₂Ceramic Composite

As a special ultra high temperature ceramic material, Zirconium diboride （ZrB2）was paid more attention gradually by the scientists in the world due to its high meltingpoint, high strength, high hardness, good electrical and thermal conductivity, flameresistance, heat resistance, oxidation resistance, corrosion resistance and catchingneutron etc. Silicon carbide whisker （SiCw） is a popular material used in reinforcewith high intensity, highly elastic modulus. SiCw whisker reinforced ZrB2ceramicmatrix composite materials has broad application prospects in the field of ultra-hightemperature.In this paper, ZrB2diboride and SiCw were used as the main raw materials. Thewhisker microstructure was improved by added the Silicon carbide whisker soaked inthe Mixture of HF and concentrated HNO₃which Volume ratio is1︰1. The Siliconcarbide whiske was distributed by using the mixed solvent. The results showed that:the crystalline phase of whiske was single and surface of the whiske was smooth. Thebest dispersion effect was adding40vol%ethanol and60vol%PEG.The acidifed SiCw/ZrB2composites were prepared by hot-pressing sintering, therelative density, microstructure and mechanical properties of ZrB2-SiCw were testedand analysised. The optimal comprehensive mechanical properties of sample S10which were obtained by orthogonal was prepared by adding20wt%SiCw, sintering in1800℃for30minutes and molding pressure under25MPa. The bending strength,vickers hardness and fracture toughness of S10were811.86MPa,21.24GPa and8.4MPa·m^1/2,respectively. The transgranular fracture and intergranular fracture werethe fracture mode of composites through reseaching the toughening mechanism of thesample S10. Whisker bridging, whisker pull out and crack deflection were the maintoughening mechanism.The oxidation experiment of sample S₁0was carried out by the static oxidationmethod at1200℃and1500℃. The oxidation oxide across section was alsocharacterized by means of XRD and SEM.The results indicated that in the surface ofsample, the oxidation film which is a dense layer of boron silicate glass is formedafter high temperature oxidation reaction, and the thickness of oxidation film is9.5μm at1200℃and94.2μm at1500℃. The surface of sample could be effectivelycovered. Thus, the material was prevented from further oxidation, which showed itsfine oxidation resistance in the high temperature.