Preparation Of Foam Glass Ceramics From Tungsten Tailings

As of 2020,the total amount of tungsten tailings in China has reached more than10 million tons,and a large number of them are still piled on the surface.The effective utilization of tungsten tailings has become an urgent problem to be solved.This subject prepared tungsten tailings as the main raw material and prepared foamed glass-ceramic materials.The samples were characterized using modern analytical testing techniques such as differential thermal analysis,X-ray diffractometer,scanning electron microscope and infrared spectroscopy.The application of tungsten tailings in the field of foam crystallites can not only realize the high-value and large-volume utilization of tungsten tailings,but also effectively solve the environmental problems caused by the massive storage of tailings,and at the same time bring considerable economic benefits to mining enterprises.The foam glass ceramics prepared in this study are divided into two parts.Namely:preparation of tungsten tailings foam glass ceramics and rare earth doped tungsten tailings glass ceramics.The first part is the preparation of foam glass ceramics from tungsten tailings.The effects of the addition of tungsten tailings and the heat treatment process on the properties of foam glass ceramics were studied.First,based on the analysis of the composition of tungsten tailings,the basic glass formula was designed with tungsten tailings as the main raw material.The basic glass powder was obtained by high temperature melting,water quenching and grinding.Then,the optimal addition amount of tungsten tailings was obtained by DTA-TG testing the crystallization temperature curve of the basic glass,and the heat treatment process conditions were determined by combining the DTA curve of previous literature and foaming agent CaCO₃.The results show that the optimum addition amount of tungsten tailings is50%;the addition amount of additives are respectively 3wt%of foaming agent calcium carbonate,4wt%of stabilizing agent trisodium phosphate,10wt%of cosolvent borax;the heat treatment system is:foaming temperature 800?,crystallization temperature 950?.The foam glass ceramics samples from tungsten tailings were prepared by one-step and segmented sintering process respectively,and their properties were compared.The results show that the performance of foam glass ceramics prepared by segmented sintering method is better.The bulk density of the sample is 0.768 g/cm³,the porosity is 68.43%,and the compressive strength is6.67MPa.The second part:on the basis of the first part of the tungsten tailings foam glass ceramics,the incorporation of rare earth yttrium oxide and optimization of heat treatment process parameters are studied.Firstly,the orthogonal method is used to determine the heat treatment process parameters,and then the single factor test is used to optimize the detection to obtain the optimal process parameters of heat treatment process.The results show that the foaming time has the greatest influence on the compressive strength,followed by foaming temperature,crystallization temperature and crystallization time.If the foaming time is too long,it is easy to produce connected pores,and if it is too short,the pore size will be too low.The foaming temperature mainly affects the bulk density of the sample.T he crystallization temperature and time should not be too high or too long,otherwise the compressive strength of the sample will be adversely affected.The best heat treatment system is:foaming time 30min,foaming temperature 880?,crystallization temperature 950?,crystallization time 30min.Foam glass ceramic samples were prepared by piecewise heat treatment with different yttrium oxide content.The performance of 2wt%glass ceramics with yttrium oxide content is the best.Its bulk density is about 0.5-0.6g/cm³,porosity is 77%,water absorption is about 7.5%,average pore diameter is about1.02-1.44mm,and compressive strength is 10MPa.It can meet the performance requirements of building wall insulation materials.To sum up,the foam glass ceramics made from tungsten tailings have good properties and simple process.The utilization rate of tungsten tailings is more than50%.Without adding nucleating agent,the products with excellent properties can be obtained.The firing temperature is not high and the cost is low.Finally,the influence of yttrium oxide content on the structure of glass matrix,the crystallinity of precipitated crystal phase,the pore size distribution of pores and the distribution of bubbles and crystal phase were studied by means of XRD,SEM,pore size and bulk density.The new surface growth rate of the foamed glass ceramics was calculated,and the foam microcrystallization process was compared with the one step sintering method.The results show that when the foaming process and crystallization process are carried out at one time,the crystallization behavior of foam glass ceramics inhibits the growth of bubbles.However,the porous structure with moderate size and uniform distribution can be obtained when the foaming process and crystallization process are separated by the segmented sintering method and the foaming process is carried out under the condition of low viscosity of glass melt.The growth of bubble promotes the precipitation of crystal phase in the process of crystallization.The piecewise sintering method of yttrium doped with uniform distribution of porous structure promotes the crystallization process and avoids the inhibitory effect of crystallization behavior on the growth of bubbles in the process of foaming and crystallization.It has a better effect on the performance of foam glass ceramics than the one-step process.