Preparation For MgO Foam Ceramic And Study On Properties

The foam ceramic of MgO is the ideal materials for melting and purifying magnesium alloy melt for it has overcome the problem of the reaction between the traditional foam ceramic filter and the magnesium melt.As for the difficulty in the sintering and poor thermal shock resistance caused by the high sintering temperature and thermal expansion coefficient of MgO,in this paper,MgO solid ceramics were prepared by slurry injection molding method.The effects of Al₂O₃ content and sintering temperature on the microstructure and properties of MgO ceramics were investigated.The corrosion mechanism of Mg/Al alloy with different Al₂O₃ content of MgO was studied by using MgO ceramics prepared in the actual filtering environment.Using organic foam impregnation for MgO foam ceramic filter,and the filtration effect of MgO foamed ceramics was compared with that of wire mesh filtration in the laboratory,and the filtration mechanism of MgO foam ceramic filter was analyzed theoretically.The results show that Al₂O₃ improved sinterability of MgO ceramics;during the sintering process,Al₂O₃ reacted with MgO to form MgAl2O4 ceramic phase around the MgO grain,the particles combined closely and filled the pore,so as to reduce the porosity and enhance the density.The sample sintered at 1500 ? for 2 h had linear shrinkage ratio of 20.93%,volume density of 1.4995 g·cm–3,porosity of 12.41% and the bending strength of 45.6 MPa,when the adding amount of Al₂O₃ was 20%.The thermal shock resistance of MgO ceramics was improved with the addition of Al₂O₃,and the thermal shock resistance of MgO ceramics achieved the optimal value when the content of Al₂O₃ was 10 %.The quantity and size of pores in MgO ceramic with 10% addition of Al₂O₃ increased with increasing of sintering temperature,meanwhile the grain size of ceramic material increased obviously and the bonding between grains was more and more closely.When the sintering temperature increased from 1400 ? to 1500 ?,the volumetric density,volume shrinkage and flexural strength of MgO ceramics showed a trend of increasing,which had a reverse rule to the change of porosity.The MgO ceramics with different addition of Al₂O₃ in magnesium melt is stable,compared with the original structure of ceramic material,the corrosion layer has a less porosity and higher density which prevented the further spread of the magnesium melt into the ceramic material.The MgO ceramic is easy to appear crack and breakage with no Al₂O₃ added,while the MgO ceramic with 10% or 20% Al₂O₃ added can remain its perfect form and has an erosion resistance performance for magnesium melt.MgO ceramic material is stable in the ADC12 Aluminum Alloy melt,and the corrosion resistance of aluminum alloy melt for MgO ceramic material is irrelevant to the Al₂O₃ addition and the corrosion time,meanwhile the Aluminum Alloy melt does not invade the ceramic material and without capillary and chemical reaction.After alkali treatment,the diaphragm for Polyurethane sponge is reduced to avoid the clogging phenomenon effectively,and the surface roughness is increased the adhesion for slurry.The porosity for as-prepared MgO foam ceramics is 83%,the bulk density is 0.4 g/cm3,the bending strength is 1.08 Mpa,and the the as-prepared MgO foam ceramic has a good thermal shock resistance,which can basically satisfy the filtration for magnesium alloy melt.By using the as-prepared MgO foam ceramic to filtrate waste magnesium,we found that the MgO foam ceramic not only has good interception effect for large size impurities,but also has good filter and adsorption effect for the small size of impurities and liquid inclusions.