| With the government's emphasis on ecological environmental protection and the increasing awareness of environmental protection among the people,energy conservation and environmental protection have become the consensus of the Chinese people.Thermal insulation,especially at high temperatures,is an important aspect of energy conservation and environmental improvement.For many years,thermal insulation materials are generally used only in permanent linings of high temperature furnaces due to raw materials,price or mechanical strength and low operating temperatures,and are rarely used directly as working linings.With the continuous development of high temperature work in China,the development of a refractory material that can be directly used as a working lining and has thermal insulation properties has attracted more and more attention.To this end,the research team of this research group and the company have jointly developed a mullite microsphere refractory raw material,and hope to use this raw material to develop a high-strength,high working temperature thermal insulation refractory material.Therefore,in this paper,under the premise of comprehensive analysis of the performance of mullite microspheres,mullite microsphere insulation refractories were prepared in the laboratory using mullite microspheres as the main raw materials,and the types of binders and additives were studied.The effect of the pore former on its properties is as follows:1.The chemical composition of the mullite microspheres is basically the same,and the microstructure is different:the surface of the mullite microsphere 1#is well developed,no glass phase exists;the surface of the mullite microsphere 2#is covered with a layer,thinner glass phase;mullite microsphere 3#surface covers thicker glass phase,effectively reducing the thermal conductivity of the microsphere.Mullite microsphere 3#has the lowest thermal conductivity and the best thermal shock resistance,and is more suitable as a raw material for use in insulating refractories.2.When calcium aluminate cement,silica sol and aluminum sol are used as binders,the mechanical properties at room temperature and high temperature mechanical properties increase with the increase of binder content,and the thermal conductivity increases accordingly.As a binder,when the addition amount is 8 wt%,the comprehensive performance of the sample is the best.At this time,the sample has a bulk density of 1.52 g/cm~3,apparent porosity of 48.1%,a normal temperature flexural strength of 3.6 MPa,and a normal temperature withstand voltage.The strength is 13.0MPa,the high temperature compressive strength is 2.6 MPa,and the thermal conductivity is 0.232 W/(m·K).3.Adding AlF3·3H2O can effectively increase the density,normal temperature strength and high temperature strength of the sample.When the addition amount of AlF3·3H2O is 4 wt%,the comprehensive performance of the sample is the best,and the volume density of the sample is 1.85 g/cm~3,the apparent porosity is 38.5%,the normal temperature flexural strength is 30.5 MPa,the normal temperature compressive strength is 152.4 MPa,the high temperature flexural strength is 11.3 MPa,and the thermal conductivity is 0.661 W/(m·K).4.Starch is added as a pore-forming agent to the sample,which can effectively reduce the bulk density of the sample,increase the apparent porosity of the sample,and reduce the thermal conductivity.However,the shrinkage rate of the sample after burning is increased,and the strength is significantly decreased.Among them,when the4 wt%starch was added,the performance of the sample was the best.At this time,the bulk density of the sample was 1.72 g/cm~3,the apparent porosity was 44.9%,the normal temperature flexural strength was 13.2 MPa,and the room temperature compressive strength was 64.3 MPa,the high temperature flexural strength at 1300°C is 4.9 MPa,and the thermal conductivity at 900°C is 0.497 W/(m·K). |
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