| In order to reduce the accumulations of iron tailings as well as the resulting ecological problems and get its new ways of recycling.In this paper,tailings is used as base materials in the field of thermal insulation materials for the first time.Asimple method of micronanorization was established,and prepared a new thermal insulation composites by drying and curing at room temperature,which is based on micro-nano tailings,supplemented by SiO2aerogel,cellulose and glass fiber.Taking the thermal conductivity as the criterion,four factors and three levels orthgonal test were selected to carry out the orthogonal optimization of the four main influencing factors（the particle size of micro-nano iron tailings,the content of SiO2aerogel、hydroxypropyl methyl cellulose and glass fiber）of the micro-nano iron tailings/SiO2aerogel composites,and the influence factor primary and secondary and optimal formula were obtained.By virtue of microscopic image analysis,the change of microstructure of iron tailings before and after micro-nano were contrasted and the influence of additives on the internal structure of composites based on micro-nano tailings,the obtained image was quantitatively analyzed with the help of Matlab and image pro-plus 6.0（hereinafter referred to as IPP6.0）,feasibility comparison verification with the real data measured in the experiment was carried out.The effects of micro-nano on the physical and thermal insulation performance of iron tailings and the improvement of thermal insulation performance by SiO2aerogel were discussed.And on the basis of the optimal formula of orthgonal test,a series of speciments of micro-nano tailings/SiO2aerogel composites were prepared.Compared microscopic analysis,the influence law of particle size of micro-nano iron tailings,the content of SiO2aerogel、hydroxypropyl methyl cellulose and glass fiber on the density,porosity,thermal conductivity and compressive strength of micro-nano tailings/SiO2aerogel composites were experimentally studied,and many well-fitted relationship functions were obtained.The main finding are as follows:（1）Based on the analysis of main component content,iron tailings can be used as new resource of cheap cementing materials in practical engineering.The final grinding median particle size d（0.5）of iron tailings is appropriate to be controlled at about0.2μm or so,and the correspongding grinding time is 120mins,at which the optimal benefits can be obtained.（2）The results of the orthogonal experiment were as follows:The fomula is optimal when the The formula is optimal when the particle size of iron tailing sand is0.2μm and the content of aerogel,hydroxypropyl methyl cellulose and glass fiber is20%,0.6%and 1%,respectively.,At this time,the composite material had the minimum thermal conductivity of was 0.065 W/（m·K）,the compressive strength was1.938 MPa.The primary and secondary influencing factors are as follows:The particle size of iron tailing sand had the greatest influence,followed by SiO2aerogel content,the influence of cellulose ether and glass fiber content were relatively small.（3）The results of the experiment had confirmed that the specific surface area of iron tailings increased greatly and thermal conductivity decreased dramatically due to the micronanorization.The specific surface area of iron tailings with particle size of about 0.2μm increased by 28.05m2/g,and the thermal conductivity decreased by0.5748W/（m·K）compared with that of iron tailings with initial particle size of27μm.This phenomenon provided a new thought for the application of iron tailings in the field of thermal insulation applications.（4）The iron tailing sand has a compact internal structure with grinding,diferent from a large number of lumps before grinding,there are no lumps with grinding and the surface is smooth and flat.In terms of color,the color of iron tailings before grinding was yellowish,while the color of micro-nano iron tailings tends to be black gray due to the decrease of particle size.In terms of water retention,the water retention of micro-nano iron tailings was significantly enhanced compared with the initial iron tailings.（5）The admixture improves the compact structure of matrix,the material became loose and porous,besides more holes and gaps appeared.The existence of each component in the composite material was observed by scanning electron microscopy,and it was found that SiO2aerogel was scattered on the matrix and the surface was smooth and complete,which was not affected by the hydration stage of the tailing sand.The porous structure of the aerogel greatly improved the compact matrix.（6）When 20%aerogel was added,the thermal conductivity of 0.2μm,0.6μm and1.0μm iron tailings/SiO2aerogel composites decreased by 85.58%,74.77%and20.52%,respectively.It can be seen that the addition of SiO2aerogel can improve the thermal conductivity of micro-nano iron tailings with different particle sizes to a certain extent,but the improvement of iron tailings with smaller particle sizes can be more significant.（7）The porosity quantified by magnification of 1000～5000 times of the images were in good agreement with the measured porosity.Therefore,the image magnification selected in the quantitative analysis of the image should not be too large or too small,and the most appropriate magnification should be controlled between1000～5000 times.（8）The micro-nano iron tailings/SiO2aerogel composite material had the advantages of thermal insulation,low cost and light weight,so it is of great value in energy saving,low cost and increasing volume ratio when used in building partition structure.（9）The density of composites based on iron tailing sand decreased with the decrease of the particle sizes of iron tailing sand,and the porosity gradually increased with the decrease of iron tailing sand particle size.The particle size of iron tailings decreased from 2.0μm to 0.2μm,the density decreased by 23.75%,and the porosity increased by 15.8%.The thermal conductivity decreased with the decrease of particle size,that is,the smaller the particle size of the iron tailings,the smaller the thermal conductivity and the better the thermal insulation effect.The compressive strength increased with the increase of iron tailing particle size.（10）The density,thermal conductivity and compressive strength of composites based on iron tailing sand decreased with the increase of SiO2aerogel content,but the porosity increased with the increase of aerogel content.Therefore,the addition of SiO2aerogel can effectively improve the thermal insulation effect of composites based on iron tailings.but in terms of the strength of material,only a small amount of SiO2aerogel should be added.When the content of SiO2aerogel was 25%,the compressive strength of composites decreased by 57.48%compared with the control group without SiO2aerogel.When the contents of SiO2aerogel were between 10%and 20%,the influence of SiO2aerogel on the porosity of composites were the greatest,at which the density decreased by 14.78%,the porosity increased by 27.47%,and the thermal conductivity decreased by 76.53%. |
