The Preparation Of Porous Alumina Ceramics With Solid Particle-Stabilized Form

Environmental pollution and resource exhaustion is threatening the sustainabledevelopment of China, how to solve the energy wastage of the high temperaturefurnace, industrial furnace and other thermal equipment has always been an importantsubject of chemical engineering, metallurgical industry and other large energyconsumption. Traditional refractories are gradually being replaced by lightweightinsulation materials which has high porosity, low thermal conductivity, small volumedensity and heat capacity.Alumina porous material was fabricated using Al2O3powder and silica powderas raw material, water as solvent medium, Propyl Gallate (PG) as foam stabilizer,dextrin and gelatin as a mixed binder and forming by freeze-drying. The optimalingredient was determined according to orthogonal experiment. The stable effect wascompared between PG and traditional surfactant sodium dodecyl sulfate. The effect ofPG content and slurry solid content on the properties of materials was researchedrespectively. The DTA-TG curves of green bodies and the XRD curves of the sampleswhich sintered at different temperatures were analyzed to determine the best sinteringtechnology. The influence of porosity, PG content and testing temperature on thermalconductivity of the samples were analyzed by researching the influence factors ofmaterial thermal conductivity. The main results were as follows:The stable effect of PG was better than traditional surfactant sodium dodecylsulfate. When PG content was below0.2wt%, ceramic slurry could not sufficientlyfoaming. When PG content was0.2wt%, the apparent porosity significantlyincreased to76%. With the increase of PG content, the apparent porosity declinedslightly and compressive strength increased and reached12.5MPa (0.6g/cm3) whichis the maximum when PG content was1.5wt%. Pore diameter of samples was30~100μm.When PG content was1.5wt%, particles on the pore wall surface were tightlystacked, pore diameter was small and fewer open pores appeared. Particles on the pore wall surface were loosely arranged when PG content was0.8wt%, porediameter was big and more open pores appeared. With the increase of solid content,apparent porosity and linear shrinkage decreased obviously, volume density andcompressive strength increased, the best solid content within the scope of experimentwas58wt%.The main weightlessness time of sample was room temperature to550℃,mullite phase appears when the sintering temperature was1400℃, the main phase ateach sintering temperature were all alumina phase. Increasing the sinteringtemperature and heating rate could do better to increase the compressive strength ofsamples, But it is easy to cause the sample cracking deformation when heating ratewas too fast.The linear change on reheating was below0.3%when sinteringtemperature was1500℃, indicating that the sample has better volume stability underthe environment of high temperature.The thermal conductivity of the samples waslower when the porosity was higher, pole wall was more completed or the testingtemperature was lower.The thermal conductivity of the samples which was sintered at1500℃was aslow as0.128W·(m·k)-1(400℃)when the PG content was1.5wt%, the solid contentwas58wt%, the porosity was71%and the compressive strength was12.5MPa.