To meet the emerging demands for thermal protection materials for hypersonic aircraft,developing porous ultrahigh-temperature ceramics with both robust mechanical properties and superior thermal insulation performance...To meet the emerging demands for thermal protection materials for hypersonic aircraft,developing porous ultrahigh-temperature ceramics with both robust mechanical properties and superior thermal insulation performance is a critical challenge.Herein,we report novel porous(Ta_(0.2)Nb_(0.2)Ti_(0.2)Zr_(0.2)Hf_(0.2))C high-entropy carbide(PHEC)ceramics fabricated by a self-foaming method using commercially available metal chloride and furfuryl alcohol(FA)as precursors.The PHEC ceramics are constructed of microspheres with a size of 2µm,leading to a high porosity of 91.3%and an interconnected frame.These microspheres consist of high-entropy carbide grains(20 nm),resulting in abundant interfaces and nanosized pores in the PHEC ceramics.Due to its unique hierarchical structure,the prepared PHEC ceramics have outstanding compressive strength(28.1±2 MPa)and exceptionally low thermal conductivity(κ_(T),0.046 W·m^(-1)·K^(-1))at room temperature.This makes it a promising thermal insulation materials for ultrahigh temperature applications.This work provides a cost-effective and facile strategy for producing porous ultrahigh-temperature ceramics.展开更多
The quest for lightweight and functional materials poses stringent requirements on mechanical performance of porous materials.However,the contradiction between high strength and elevated porosity of porous materials s...The quest for lightweight and functional materials poses stringent requirements on mechanical performance of porous materials.However,the contradiction between high strength and elevated porosity of porous materials severely limits their application scenarios in emerging fields.Herein,high-strength multifunctional mullite-based porous ceramic monoliths were fabricated utilizing waste fly ash hollow microspheres(FAHMs)by the protein gelling technique.Owing to their unique shell-pore structure inspired by shell-protected biomaterials,the monoliths with porosity of 54.69%–70.02% exhibited a high compressive strength(32.3–42.9 MPa)which was 2–5 times that of mullite-based porous ceramics with similar density reported elsewhere.Moreover,their pore structure and properties could be tuned by regulation of the particle size and content of the FAHMs,and the resultant monoliths demonstrated superior integrated performances for multifunctional applications,such as broadband sound insulation,efficient thermal insulation,and high-temperature fire resistance(>1300℃).On this basis,mullite-based porous ceramic lattices(porosity 68.28%–84.79%)with a hierarchical porous structure were successfully assembled by direct ink writing(DIW),which exhibited significantly higher compressive strength(3.02–10.77 MPa)than most other ceramic lattices with comparable densities.This unique shell-pore structure can be extended to other porous materials,and our strategy paves a new way for cost-effective,scalable and green production of multifunctional materials with well-defined microstructure.展开更多
基金This research was supported by the National Natural Science Foundation of China(Nos.52173299 and 52372087)the Natural Science Foundation of Shaanxi Province(No.2021JZ-51).
文摘To meet the emerging demands for thermal protection materials for hypersonic aircraft,developing porous ultrahigh-temperature ceramics with both robust mechanical properties and superior thermal insulation performance is a critical challenge.Herein,we report novel porous(Ta_(0.2)Nb_(0.2)Ti_(0.2)Zr_(0.2)Hf_(0.2))C high-entropy carbide(PHEC)ceramics fabricated by a self-foaming method using commercially available metal chloride and furfuryl alcohol(FA)as precursors.The PHEC ceramics are constructed of microspheres with a size of 2µm,leading to a high porosity of 91.3%and an interconnected frame.These microspheres consist of high-entropy carbide grains(20 nm),resulting in abundant interfaces and nanosized pores in the PHEC ceramics.Due to its unique hierarchical structure,the prepared PHEC ceramics have outstanding compressive strength(28.1±2 MPa)and exceptionally low thermal conductivity(κ_(T),0.046 W·m^(-1)·K^(-1))at room temperature.This makes it a promising thermal insulation materials for ultrahigh temperature applications.This work provides a cost-effective and facile strategy for producing porous ultrahigh-temperature ceramics.
基金financially supported by the National Natural Science Foundation of China(Grant No.51802347)the Natural Science Foundation of Hubei Province(Grant No.2022CFB939).
文摘The quest for lightweight and functional materials poses stringent requirements on mechanical performance of porous materials.However,the contradiction between high strength and elevated porosity of porous materials severely limits their application scenarios in emerging fields.Herein,high-strength multifunctional mullite-based porous ceramic monoliths were fabricated utilizing waste fly ash hollow microspheres(FAHMs)by the protein gelling technique.Owing to their unique shell-pore structure inspired by shell-protected biomaterials,the monoliths with porosity of 54.69%–70.02% exhibited a high compressive strength(32.3–42.9 MPa)which was 2–5 times that of mullite-based porous ceramics with similar density reported elsewhere.Moreover,their pore structure and properties could be tuned by regulation of the particle size and content of the FAHMs,and the resultant monoliths demonstrated superior integrated performances for multifunctional applications,such as broadband sound insulation,efficient thermal insulation,and high-temperature fire resistance(>1300℃).On this basis,mullite-based porous ceramic lattices(porosity 68.28%–84.79%)with a hierarchical porous structure were successfully assembled by direct ink writing(DIW),which exhibited significantly higher compressive strength(3.02–10.77 MPa)than most other ceramic lattices with comparable densities.This unique shell-pore structure can be extended to other porous materials,and our strategy paves a new way for cost-effective,scalable and green production of multifunctional materials with well-defined microstructure.
