Preparation of porous magnesium-aluminate spinel materials by foaming-spontaneous solidification casting method
To improve the thermal efficiency of thermal kilns and reduce the thermal energy loss,porous magnesium-aluminate spinel materials were prepared by the foaming-spontaneous solidification casting method,using industrial-grade medium-grade magnesia fine powder(d50=34.2 μm)and calcined alumina powder(d50=3.4 μm)as raw materials,potassium oleate as a foaming agent,sodium carboxymethyl cel-lulose as a foam stabilizer,and an alternating copolymer of isobutylene and maleic anhydride(ISOBAM-104,referred to as"IB")as a curing agent.The effects of the IB extra-addition(0,0.1％,0.2％,0.3％,and 0.4％,by mass)on the properties of the slurry and the specimens after firing at 1 500 ℃ for 3 h were stud-ied.The results show that:(1)with the increase of the IB addition,the expansion ratio of the slurry decrea-ses,and the absolute value of the Zeta potential firstly increases and then decreases;after firing,the appar-ent porosity of the specimen decreases,the bulk density increases,the cold compressive strength first in-creases and then decreases,the distribution of pores changes from closely packed to independently dis-persed,the pore wall thickens,and the thermal conductivity firstly increases and then decreases;(2)when the IB addition is 0.3％,the Zeta potential is-52.6 mV and the slurry is the most stable;the fired specimen has the maximum cold compressive strength of 32.7 MPa,the apparent porosity of 54.4％,the bulk density of 1.63 g·cm-3,the thermal conductivity of 0.205 W·m-1·K-1at 350 ℃,and the minimum average pore size of 46.8 μm,the comprehensive properties are the best.
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