Study On Al₂o₃ Fiber Reinforced Porours Ceramics Prepared By Freeze Drying

Because of its low thermal conductivity and chemical stability,Al2O3 porous ceramics are widely used in filter materials and thermal insulation materials.The introduced porosity phase can improve the filtration performance and thermal insulation performance of Al2O3 porous ceramics,but the strength of the ceramics decreases sharply with the increase of porosity.Improving the preparation process of Al2O3 porous ceramics and adding fibers are the main ways to increase its strength.In this paper,the freeze-drying method was used to prepare Al2O3 porous ceramics.By changing the solid content of the slurry,freezing temperature,fiber addition,sintering aid types and sintering process parameters,the influence of the parameters on the structure and performance of the porous ceramics was analyzed,using SEM and XRD to Characterize the micro-morphology and phase composition of the sample,and use a mercury intruder and a universal testing machine to evaluate the pore structure and mechanical properties of the sample.At the same time,the compression mechanism of porous ceramics and the strengthening mechanism of Al2O3 fiber-reinforced porous ceramics are discussed.Research indicates:Compared with other sintering aids,using CuO-TiO2(1:2)as a sintering aid,the Al2O3 porous ceramic with a solid phase content of 25 vol.%prepared by sintering process at 1400?:for 2h,the pore wall particles are tightly bound,The particle size is uniform and the compressive stren gth(10.58 MPa)is high;when the solid content increases from 20 vol.%to 30 vol.%,the pore size distribution of the sample is bim odal distribution,and the average pore size decreases from 51.02 ?m to 34,15?m.The porosity decreased from 68.1%to 48.0%,and the compressive strength of Al2O3 porous ceramics increased from 5.1MPa to 20.1 MPa.Comparing the structural performance constants of different solid phase contents,it is found that when the solid phase content is 25vol.%,the Al2O3 porous ceramic has the most reasonable porous structure,with porosity and compressive strength of 60.7%and 10.58 MPa,respectively;the freezing temperature is from-When the temperature decreased from 10? to-50?,the average pore diameter decreased from 66.9?m to 31.14?m,and the compressive strength increased from 9.7 MPa to 12.7 MPa.Compared with the samples without fibers,the strength of Al2O3 porous ceramics reinforced with Al2O3 fibers was greatly improved.When the fiber addition amount was 15 vol.%,the porosity and compressive strength of Al2O3 porous ceramics were increased by 8.2%and 35.3%,respectively.