In Situ Synthesis of ZrN(ZrO2)/Si2N2O Composite Materials from Zircon by Carbothermal Reduction-Nitridation Process

Abstract

ZrN(ZrO2)/Si2N2O composite materials were synthesized by in-situ carbothermal reduction-nitridation process, with zircon and carbon black as raw materials. The influences of heating temperature and carbon content on synthesis process were investigated, the phase composition and microstructure of the synthesized materials were characterized by X-ray diffraction and scanning electronic microscope. It was found that the decomposition of ZrSiO4 as well as the formation of ZrN and Si2N2O could be promoted by increasing heating temperature and carbon content. ZrN(ZrO2)/Si2N2O composite materials could be synthesized at 1480°C for 6h by heating the sample with ZrSiO4/C mass ratio of 100/40. The ZrN and Si2N2O in the synthesized materials existed in particle shape with an average grain size of about 1–2μm. Introduction Recently, an important research trend of refractories is to develop non-oxides materials such as nitrides, carbides, borides and silicides as well as their composites [1,2]. Among them, zirconium nitride (ZrN) and Silicon oxynitride (Si2N2O) display many outstanding properties, such as high melting points, hardness and strength, excellent corrosion and oxidation resistance [3-5]. zirconium oxide (ZrO2) also exhibits high toughness and strength, excellent corrosion and thermal shock resistance[6]. It is believed that combining ZrN, ZrO2 and Si2N2O into composite materials might yield excellent high temperature combination properties. In the present work, ZrN(ZrO2)/Si2N2O composite materials were synthesized by in-situ carbothermal reduction-nitridation process, with zircon and carbon black as raw materials. The influences of heating temperature and carbon content on synthesis process of the materials were investigated. The carbothermal reduction-nitridation reaction process was also discussed.