Preparation Of SiC Fiber/Diopside-based Tailing Glass-ceramic Composite

Glass ceramic is one kind of material of many good properties.It has strong tolerance to the variations in raw materials.Its phase constituents,microstructure and properties can be adjusted simply through varying parameters of its fabrication procedures.Because of this feature,glass ceramic materials can find their application in all kinds of different fields,such as electric sealing,biology,high-temperature insolating,aerospace,and even in the field of the mining and metallurgy solid wastes utilization for high added value.However,the inherent brittleness of glass ceramic has become the major obstacle to its further application.Numerous studies have shown that integration with fiber is an effective to toughen glass ceramics.The hot-press procedure is the most method for the fabrication of such composite.As a result,the obtained material is always anisotropic in its properties.Meanwhile,the hot-press method cannot be used to fabricate materials of complex shape.These weaknesses contribute mainly to the now limited application of fiber-glass ceramic composites.And pressure free fabricating techniques are always a desirable goal that motivates relevant researches.Unfortunately,these researches are generally in their primary stages.Therefore,this paper aims to develop a pressure free technique for the fabrication of Si C fiber-diopside glass ceramic composite.Then,methods,such as DSC,XRD,SEM,EDS,mechanic property measurement and high precision impedance analysis,will be used to study the effect of Si C fiber concentration,variations in the temperatures for crystallization heat-treatment and final sintering procedure on the microstructure and properties of the fabricated composites.The results of this study show the increase of Si C fiber addition from 0 to 40 wt.%inhibits the formation of diopside by enhancing the formation of wollastonite.Phenomenon,such as Fiber pulling-out,bridging and crack defecting,have all been be observed within the fractured composite samples.The Vickers hardness,fracture strength and toughness of the composite all reached to their highest levels,which are 7.02±0.4GPa,268.2±7.3MPa and 1.93±0.2MPa×m^1/2 respectively.In addition,the increase of Si C fiber caused the dielectric constant and loss of the composite to increase at the whole testing frequency range.The study using the composite with 30wt.%Si C fiber as the model material showed the increase of crystallization temperature from 850 to 910°C had no influence on the crystalline phase constituents.However,the crystallization of diopside has been enhanced.The optimum temperature for crystallization heat-treatment was 890°C.The fracture strength and toughness of the sample crystallized at this temperature were measured at275.5±8.2MPa and 1.99±0.18MPa×m^1/2 respectively.These two values were 43%and 56%larger than those of Si C-free glass ceramic sample.The dielectric constant showed a parabola variation with the increase of the temperature for crystallization heat-treatment,while the dielectric loss only showed a continuous increase.The study using the composite with 30 wt.%Si C fiber as the model material also showed the increase of sintering temperature from 1030 to 1090°C caused the content of Si C to decrease remarkably.Meanwhile,the crystallization of diopside was enhanced and the formation of wollastonite was inhibited.The optimum sintering temperature was determined at 1050°C.The fracture strength and toughness of the composite sample sintered at the optimum temperature were measured at 268.2±7.3MPa and1.93±0.2MPa×m^1/2 respectively.Similar parabola variation was observed within the changing process of dielectric constant with the increase of sintering temperature.And the dielectric loss decreased at the same time.The optimum parameters for the fabricating of Si C-diopside glass ceramic composite were finalized as:30 wt.%for the addition of Si C fiber,890°C for the temperature for crystallization heat-treatment,and 1050°C for sintering temperature.The result of this paper can be a good reference for the comprehensive utilization of Bayan Obo tailing and other similar mining and metallurgy solid wastes,therefore paved a new way for environment engineering.