Preparation Of Magnesium Foam Ceramics

Foam ceramics can be widely applied as energy saving heat insulation materials,sound absorption materials,catalyst support materials,and food and medicine industry and filter fields.With the wider applications of foam ceramics,it is very necessary to prepare foam ceramics with controllable structure,uniform pore diameter and stable performance.In this research study,middle-grade magnesia powder was selected as raw material,and sodium dodecyl benzene sulfonate(SDBS),sodium dodecyl sulfate(SDS),dodecyl trimethyl ammonium bromide(DTAB),hexadecyl trimethyl ammonium bromide(CTAB)as foaming agent.Foaming method and polystyrene ball as pore-forming agent of pore-forming agent method were used to produce magnesia ceramic foam.The foaming mechanism of different foaming agent and stabilizing mechanism of bubble foam agent,and the influence of magnesium process parameters on the properties and structures of foam ceramics were studied.The results showed that magnesium foam ceramicsprepared by two-step foaming method,the foaming ability was improved by adding SDBS,SDS,CTAB and DTAB.foaming volume of SDBS > DTAB > SDS> CTAB;When the concentration of SDBS is 10 g·L-1,the foam volume is 115 ml and the half-life is 97 min at most.Stability ability of three foam stabilizers:corn dextrin > potato starch > calcium stearate;when the concentration of corn dextrin was 16 g·L-1,the foam volume was 132 ml,and the half-life was 122 min at most.When the stirring time was 10 min,and the stirring speed was 2100 r/min,the number of bubble apertures was relatively small and evenly distributed.Then,magnesium oxide slurry was prepared.The order of pore size of magnesium oxide foam ceramics was DTAB >CTAB >SDS >SDBS.Stomatal distribution uniformity was SDBS >SDS >DTAB > CTAB.When 90 g oxide slurry with 64% solid content was added into 120 ml foam,the maximum compressive strength of the sample was 5.6 Mpa,at room temperature.Magnesium foam ceramics were prepared by one-step foaming method.The maximum porosity of samples was68.2% when using SDS as foaming agent.The sample using DTAB as foaming agent has the maximum compressive strength of 25.8 MPa at room temperature.Compared with one-step and two-step foaming method,the apparent porosity of magnesium foam ceramics prepared by one-step foaming method was lower than that of two-step foaming method.The compressive strength at room temperature is greater than that of two-step foaming method.The sample prepared by one-step foaming method has smaller pore diameter,more pores and thicker pore wall.When magnesium foam ceramics were prepared by pore-forming agent method,the maximum porosity was78.2% when polystyrene spheres were added as pore-forming agent,and the compressive strength at room temperature was 1.7 MPa.After pretreatment of the polystyrene spheres with aluminum sol,the apparent porosity increased from 72% to78.5%.After the spheres were dried for 9 h,the maximum compressive strength of the samples was 4.5 MPa at room temperature.