| The structure of the ceramic membrane tube consists of three parts: the support,the transition layer and the filter layer.In this paper,the ceramic membrane tube supports were prepared from high-alumina fly ash by adding pore-forming agent,and the coating and sintering process of the membrane layer(intermediate transition layer and the filter layer)on the support were investigated.The flexural strength,porosity,pore size distribution and microstructure of the composites were characterized and tested by means.The sintering kinetics was analyzed by Makipirtti-Meng empirical rate equation.The filtration performance and mechanical strength of high-alumina fly ash porous ceramic are close to those of traditional alumina porous ceramic,but the manufacturing cost is greatly reduced,it can not only solve the problem of environmental pollution caused by solid waste,but also can be used to treat waste,which shows high social significance and certain economic value.In this paper,high-alumina fly ash was used as raw material with starch and magnesium carbonate as pore forming agent,adding polymer binder.The mixed powder respectively heated at 1200-1500? for preparing 5 groups of different content of ceramic membrane supports,and its porosity,shrinkage,gas flux,water flux,flexural strength and other properties has been tested.The results show that the sintering temperature and the pore forming agent have significant effect on the properties of porous ceramics.The pore forming effect of basic magnesium carbonate was better than that of starch.With the increase of pore forming agent content,porosity,gas flux and water flux increased gradually,and the flexural strength decreased slightly.With the increase of sintering temperature,the air flux and water flux increased first and decreased in the late time,reaching a maximum value of 4854.24m3/(m2·h·bar)?48.61 m3/(m2·h·bar)at 1350?.With the comprehensive consideration,the pore forming agent is 20% basic magnesium carbonate sintering at 1350? for 2h has the best performance in the high-alumina fly ash porous ceramic support.We used a dip coating method to coat a ceramic powder particle layer with diameter of 5?m on a high-alumina fly ash support to obtain an intermediate transition layer with average pore diameter of 1.22?m;the filter layer ceramic membrane with the average pore diameter of 0.45 nm was obtained from the ceramic particle layer coated with a particle size of 500 nm.The mechanical properties,filtration properties and morphology of the composites were studied,the interlayer ceramic coatings were sintered at 1400 ? for 2h,and the alumina ceramic films sintered at 1000? for 2h shows good mechanical properties,bending strength of 8.31 MPa,which can meet the need of daily work.At the same time,it also has good permeability(the air flux of 2222.2 m3/(m2·h·bar))and high filtration accuracy(narrow pore size distribution).The activation energy of high-alumina fly ash porous ceramics was calculated by the stepwise isothermal shrinkage(SID)analysis using the Makipirtti-Meng empirical rate equation.The results show that there is only one stage in the sintering process: 1250-1400 ?,the activation energy is about 679.28 kJ / mol,and the sintering mechanism can be regarded as the sintering process from Al2O3 and SiO2 to Mullite(3Al2O3 · 2SiO2).In addition,the results show that the more complex phase of the raw material,the higher the impurity and the higher the activation energy. |
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