Study On Process And Properties Of Foamed Glass-ceramics Prepared By Iron Tailings From Beijing Area

Tailings is an industrial solid waste,and its large stockpiling seriously affects the sustainable development of Chinese mining industry.In this paper,foamed glass ceramics were prepared by tailings,which could be applied in the field of building thermal insulation.It could not only reduce environmental pollution,but also improve the technical reliability and added value of materials.In this paper,the glass ceramics of iron tailings were prepared by sintering method using the muddy fine grain iron tailings of Miyun first cloud mining group,Beijing.On this basis,the foamed glass ceramics were prepared by the high temperature foaming process,and the phase composition,microstructure,physical properties and mechanical properties of the samples were studied.Firstly,on the basis of the analysis of the composition of iron tailings,the basic glass formula was designed with iron tailings as the main raw material.The base glass powder was obtained through high temperature melting,water quenching and grinding.The glass ceramics were prepared by sintering,and the effect of crystallization temperature on the preparation and properties of glass ceramics was studied.The results showed that the crystallization temperature of glass ceramics begined at 800 ℃ and the main crystal phases were augite and diopside.With the increase of crystallization temperature,the number of grain increased and tended to regularization,and the trends of the grain formation and aggregation were obvious.The volume density,linear shrinkage,compressive strength and Vickers hardness of the glass ceramics increased first and then decreased with the increase of crystallization temperature.The best heat treatment system in the test range was 1000 ℃ crystallization temperature.The bulk density,the line shrinkage,the compressive strength and Vickers hardness were 2.54 g/cm3,14.08%,282 MPa and 4.43 GPa,respectively.The grain shape was regular columnar crystal and the arrangement was close.Secondly,Foamed glass ceramics were prepared by high temperature foaming process with iron tailings as the main raw material.The effects of foaming agent content,foaming temperature and foaming time on the structure and properties of foamed glass ceramics were studied.The results showed that with the increase of the foaming agent content from 2 wt.%to 4 wt.%,the compressive strength and volume density of the foamed glass ceramics reduced.The porosity and water absorption increased.When the foaming agent content was 3 wt.%,its comprehensive performance was the best.When the foaming agent content was 3 wt.%and the foaming time was 30 min,the volume density and compressive strength of the foamed glass ceramics decreased with the foaming temperature rising from 825 ℃ to 900 ℃,and the porosity and water absorption increased.The foamed glass ceramics had the best comprehensive properties when the foaming temperature was 875 ℃.When the foaming agent content was 3 wt.%and the foaming temperature was 875 ℃,the volume density and compressive strength of the foamed glass ceramics reduced with the foaming time from 20 min to 50 min,and the porosity and water absorption increased.When the foaming time was 30 min,the synthetic performance of the foamed glass ceramics was the best.The volume density,total porosity,compressive strength and water absorption of the foamed glass ceramics were 0.76 g/cm3,71.31%,13.46 MPa and 7.85%,respectively.Finally,the thermal conductivity of the foamed glass ceramics was measured and calculated.The results showed that there was a good consistency between the measured value and the calculated value.The thermal conductivity of the foamed glass ceramics was low,which met the requirements of the building thermal insulation materials.