Phase Reconstruction And Preparation Technology Of Microcrystalline-ceramics Prepared By Asbestos Tailings Of Mangya In High Temperature

Asbestos tailings are the solid waste from asbestos mining,which not only occupy a lot of land resources,but also included in the national hazardous solid waste list due to asbestos tailings contain a lot of asbestos fibers.Based on the unique chemical composition and mineral composition of asbestos tailings,this paper takes asbestos tailings of Mangya as the research object.Microcrystalline ceramics using asbestos tailings as raw materials was synthesized by using direct sintering method.The influence of heat treatment conditions and content of asbestos tailings on the crystal phase composition,microscopic morphology,mechanical properties of microcrystalline ceramics were studied.Then,the sintering process of asbestos tailings was studied through use sintering kinetics,and the sintering activation energy of different body compositions was calculated by theoretical model.The main results are as follows:(1)MgO,SiO₂ and Fe₂O₃are the main chemical composition of mangya asbestos tailings with a loss on ignition of 13.78%.Serpentine,talc and a small amount of magnesite were the main mineral composition of asbestos tailings and serpentine will transform to harmless forsterite at 700?.(2)Microcrystalline ceramics with forsterite as the main crystal phase and enstatite as the secondary crystal phase was synthesized by direct sintering using pre-heated asbestos tailings as the main raw material.When the heat treatment conditions changed,the kind of crystal phase remains unchanged,but the relative content of the crystal phase has changed.The bulk density,linear shrinkage,water absorption,and flexural strength of the microcrystalline ceramic samples sintered at 1225?for 2h are 2.64 g·cm^-3,10.12%,0.92%,and 45.13 Mpa,respectively.(3)Microcrystalline ceramics with forsterite and magnesioferrite as the crystalline phase was synthesized by using pre-heated asbestos tailings as raw materials and a small amount of Na₂CO₃ as fluxing agent.The increase of Na₂CO₃ in the raw materials will promote the formation of forsterite and magnesioferrite.High content Na₂CO₃ will cause the formation of intergranular pores in the sample and reduce the properties of microcrystalline ceramics.When the sintering temperature is 1150?,the bulk density of sample with 4wt.%Na₂CO₃ can reach2.87 g·cm^-3,and the linear shrinkage,water absorption,flexural strength of sample are 11.33%,0.51%and 64.57 Mpa,respectively.(4)Microcrystalline ceramics with forsterite and enstatite as the crystal phase was synthesized by using pre-heated asbestos tailings and fly ash as main raw material.The improvement of fly ash content is conducive to the formation of enstatite.The content of enstatite in the sample will increases with the content of fly ash increases.When the sintering temperature is 1190?,the bulk density,linear shrinkage,water absorption and flexural strength of the sample with 8 wt.%fly ash can reach 2.29 g·cm^-3,9.03%,0.77%,51.76 Mpa,respectively.(5)Microcrystalline ceramics with forsterite as the main crystal phase and diopside as the secondary crystal phase was synthesized by using pre-heated asbestos tailings and marble tailings as main raw material.The content of diopside increases with the addition of marble tailings.When the sintering temperature is 1190?,the bulk density,linear shrinkage,water absorption and flexural strength of the sample with 10 wt.%marble tailings can reach 2.29g·cm^-3,0.35%,9.81%,64.46 Mpa,respectively.(6)The result of the sintering kinetics study shows that as the content of marble tailings from 5 wt.%to 15 wt.%,the sintering activation energy of microcrystalline ceramics will change,and the sintering activation energy of the sample with 10 wt.%marble tailings is the lowest.It shows that adding proper marble tailings can promote the sintering and densification of microcrystalline ceramics.