Optimization Design Of Thermal Shock Properties Of Porous Alumina Ceramics With Different Pore Matching

Porous Al₂O₃ceramics with its low density and high heat preservation properties are gradually emerging in the field of high temperature applications.However,when the temperature rises rapidly or falls rapidly,the impact of thermal shock may make the strength of the material drop significantly or even cause destructive damage to the material,so it is of great significance to improve the thermal shock performance of ceramic materials.The porosity of porous Al₂O₃material has great influence on the properties of materials.For this purpose,the gel casting plus pore forming method is used to introduce the hole into Al₂O₃ceramics,and the mechanical,thermal and thermal shock properties of materials are improved by adjusting the matching of ceramic pores.Firstly,the effect of different solid content?30-50 vol%?on Al₂O₃ceramics was studied by gel casting without adding pore forming agent.Porous Al₂O₃ceramics with porosity of 13.86-28.62%were prepared.The effects of different porosity on the mechanical/thermal properties and thermal shock properties of porous Al₂O₃ceramics were analyzed in detail.Then,by means of gel casting and pore forming agent,by adding different content?10-50 vol%?of polymethyl methacrylate?PMMA?as pore forming agent,porous Al₂O₃ceramics with different porosity and porosity and 24.42-41.10%porosity were prepared.The effects of different porosity and pore matching on the mechanical/thermal properties and thermal shock properties of porous Al₂O₃ceramics were studied.With the increase of porosity of porous Al₂O₃ceramics,the flexural strength,the modulus of elasticity,the modulus of elasticity and the thermal conductivity of the samples without pore forming agent decreased from 143.92 to 87.14 MPa,2.22 to 1.43 MPa·M^1/2,91.94 to 37.98 GPa and 19.43 to 14.89 W/?m·K?.The residual strength retention of porous Al₂O₃ceramics increases with the increase of porosity,and the critical temperature difference decreases with the increase of porosity.With the increase of the porosity of porous Al₂O₃ceramics,the bending strength,the modulus of elasticity,the thermal conductivity and the flexural strength of Al₂O₃ceramics decreased from 116.4 to 88.69 MPa,from 1.80 to 1.40MPa·M^1/2,from 74.81 to 42.78 GPa and from 14.02 to 10.35 W/?m·K?.The residual strength retention of porous Al₂O₃ceramics is the highest when the porosity is 33.45%,that is to say,the thermal shock damage resistance is the best when the porosity is 33.45%.The critical temperature difference of porous Al₂O₃ceramics increases first and then decreases with the increase of porosity,that is to say,the thermal shock fracture resistance increases first and then decreases with the increase of porosity.When the total porosity is 33.45%,porous Al₂O₃ceramics have good thermal shock damage resistance and thermal shock fracture resistance at the same time.In the case of the same total porosity,the introduction of foreign pores improves the mechanical properties and critical temperature difference,reduces the thermal conductivity and fracture surface energy and affects the thermal stability of the material.