Preparation Of Magnesia Insulation Materials With Adjustable Pore Characteristic By Foaming Method

Porous insulation refractories have the advantages of light weight and low thermal conductivity in addition to the excellent high-temperature resistance of traditional refractories,and are widely used in the insulation layer of high-temperature kilns.At present,the raw materials of porous insulation refractories are mainly alumina and silica,which will react with the alkaline working liner and reduce the service life of the working liner when the temperature is high,so it is important to prepare a novel magnesia insulation refractories.In this thesis,using industrial grade magnesia powder with different particle sizes as raw materials,cationic surfactant cetyltrimethyl ammonium bromide（CTAB）and anionic surfactant sodium dodecyl benzene sulfonate（SDBS）as foaming agents,sodium carboxy methyl cellulose（CMC）as foam stabilize,isobutylene maleic anhydride copolymer（Isobam-104）and Al N as curing agent,the effects of additive content,curing process on the properties,phase composition and microstructure of the slurry and the prepared samples are investigated,and the results shows that:（1）Using magnesia powder(D₅₀≤74μm)as raw material with a solid content of60wt%,the slurry expansion ratio and viscosity increase and the surface tension decrease as the CTAB content increase;the slurry viscosity and volume holding rate increase as the CMC content increase;（2）When CTAB content is 0.3wt%and CMC content is 0.8wt%,the viscosity of slurry decrease and then increase with the increase of Isobam-104 content,when the Isobam-104 content is 0.2wt%and the sintering temperature is 1350°C,the sample porosity is 65.19%,the compressive strength is 7.8MPa,the average pore size is 31.4μm,and the thermal conductivity is 0.481W·m^-1·K^-1（350℃）;With the increase of Al N content,the viscosity of the slurry gradually becomes larger,the porosity and spinel phase content of the sample increases,and the pore size becomes smaller,the demoulding time becomes shorter and the thermal conductivity decreases compared with Isobam-104 as curing agent;（3）The foaming capacity is weak when anionic foaming agent SDBS is compared to cationic surfactant CTAB,the viscosity of the slurry is higher,the sample is not easy to remove from the mold,the amount of Isobam-104 and Al N is higher;（4）When magnesia powder(D₅₀≤3μm)is raw material,the solid content is 65wt%,with the increase of SDBS content,the surface tension of the slurry decrease,the expansion ratio and the contact angle increase;when the content of SDBS is 0.3wt%and the sintering temperature is 1350℃,with the increase of Isobam-104 content,the porosity decrease and the compressive strength increase.Maximum compressive strength is 25.26MPa,thermal conductivity is 0.196W·m^-1·K^-1（350℃）when porosity is 70.16%.