Preparation Of SiC Fiber/Cordierite Based Tailing Glass Ceramic Composite

Cordierite glass-ceramic is a kind of multiphase material with a serious of excellent properties.Its dielectric constant and loss are low,its thermal expansion coefficient can be adjustable;It is a good electrical insulator,and it can be quite stable under chemical or thermal attacks.Therefore,cordierite glass-ceramics can not only be used to manufacture insulators,filters,capacitors,etc in the field of electrical industry,but also be utilized to fabricate radar antenna protective cover.In addition,this special glass-ceramic material can also be used in the fields of biology,filtration and catalyst support.Our research group used Bayan Obo tailings and fly ash as the main raw materials,and successfully prepared a kind of cordierite-based glass-ceramics with high mechanical strength,excellent dielectric properties and low thermal expansion coefficient by melting method.However,the brittleness of these glass-ceramics limits its application.It has been proved that high modulus fibers can be used to strengthen and toughen cordierite glass-ceramics.However,such composites are normally prepared by the hot pressing method.This issue is in fact the main obstacle to further the application of such composite materials.Therefore,fabricating such composite material through a pressure-less route has become as a worthwhile research topic.However,its related study is still in its primitive stage.Therefore,this paper first attempts to prepare cordierite glass-ceramics by the traditional oxide ceramic process.Then,similar method,which requires no pressure-sintering procedure,will be used to prepare Si C fibers/cordierite-based tailing glass-ceramic composites within an embedment of graphite powders.Based on the obtained composite materials,the effect of varying Si C fiber content with the 0-40 wt%,sintering temperature and soaking time on the microstructure composition and properties of the prepared composites will be studied.The following results are obtained.Cordierite glass-ceramics were prepared from Bayan Obo tailing by the traditional ceramic preparation process ended by sintering within the temperature range of 1100 to1180°C for 4 to 12 hours.The obtained cordierite glass shows its optimum properties,which is characterized by a 1.92g/cm~3 density and a 5.22GPa Vickers hardness,when sintered at1100°C for 8 hours.Further increase of sintering temperature will lead the sintered samples to deform.Based on the above results,silicon carbide fiber/cordierite-based tailings glass-ceramics composites were prepared.Graphite powder embedment was used to prevent Si C fiber from decomposing through over-oxidization.The formation of cordierite was enhanced by increasing Si C fiber content up to 20 wt%,upon which the crystallization of cordierite was inhibited.The pores formed with the Si C-free cordierite glass ceramic were most eliminated by the addition of 10wt%Si C fiber.Then,the further increase in Si C fiber addition led the density of the composite samples to decrease.Meanwhile,the cross section surface roughness of final composite increased with the rise of Si C fiber concentration,indicating the the fracture toughness of the sample increased.At 10 MHz,the dielectric constant(41-48)and dielectric loss(0.06-0.25)of the Si C/cordierite glass-ceramic composite samples were higher than those of those fiber-free samples(34,0.008).The results of this paper can be a good reference for the development of such composite materials and their application in clean-utilizing various mining and metallurgy wastes for high added value.