Research On The Preparation Of Silicon Nitride/Titanium Nitride Bonded Silicon Carbide

In this work,silicon nitride/titanium nitride bonded silicon carbide ceramic materials were prepared by reaction sintering in buried carbon and nitrogen atmosphere respectively,using silicon carbide,elemental silicon powder and titanium ferrosilicon alloy extracted from high titanium blast furnace slag as the main raw materials.The effects of titanium ferrosilicon alloy's content,the carbon sources and the atmosphere on the physical properties,the phase composition and the microstructure of the silicon nitride/titanium nitride bonded silicon carbide products,and oxidation resistance and corrosion resistance of silicon nitride/titanium nitride bonded silicon carbide products were characterized,The experimental results show that:?1?The addition of Ti-Si-Fe alloy could improve the combination of matrix and aggregate and promote the growth and development of nitride crystal in the sample.The TiN,formed by nitridation of Ti in the alloy could effectively improve the densification of the sample and improve the mechanical properties of the product.When the amount of the alloy is in the range of 0%to 9wt%,with the increase of the additon of the alloy,the samples showed as follows,the apparent porosity decreased;the bulk density,the flexural and compressive strength increased.When the amount of the alloy is more than9wt%,the apparent porosity of the sample increased with the increase of bulk density,but the mechanical property of the sample was reduced under the nitrogen atmosphere.?2?The effective nitriding of Si and Ti in the product could be realized by the carbon-buried sintering.Fiber-like and cylindrical Si₃N₄ were formed under both buried carbon and nitrogen firing conditions,and well-developed Si₃N₄,TiN particles were observed under buried carbon firing compared with nitrogen atmosphere.Therefore,the properties of the samples sintered in nitrogen atmosphere are slightly better than those of the samples sintered in nitrogen atmosphere.?3?The addition of Ti-Si-Fe alloy could obviously improve the oxidation resistance of the products.The oxidation behavior of the product was related to the apparent porosity of the product.The addition of alloy reduced the apparent porosity of the product,and thus improved the oxidation resistance of the product.The results of XRD and SEM showed that the main products after oxidation were SiO₂,TiO₂ and Si₂N₂O.In addition,the surface that generated SiO₂ and TiO₂ can also hinder the further diffusion of oxygen,and the antioxidant ability was better.The corrosion of cryolite melt to the sample mainly occurs in the matrix part,the surface erosion is serious,and SiO₂,NaAlSi₂O₆ and other substances are formed,Na₂O-Al₂O₃-SiO₂ melt could also hinder the erosion reaction to the inside to a certain extent.The internal of the sample were mainly F ion and Na ion's penetration.