SiBCN ceramic aerogels have emerged as a new generation of integrated thermal insulation and microwave absorption materials but face great challenges in terms of mechanical properties,high-temperature stability,and ab...SiBCN ceramic aerogels have emerged as a new generation of integrated thermal insulation and microwave absorption materials but face great challenges in terms of mechanical properties,high-temperature stability,and absorption bandwidth in practical applications.Herein,SiBCN/SiOC composite ceramic aerogels were prepared by solvent thermal crosslinking,freeze-drying,and pyrolysis of precursors.Polyhydromethylsiloxane(PHMS)was introduced in situ by the hydrosilane addition reaction during the solvothermal process,which endowed the precursor aerogel with a complex and robust three-dimensional network structure and further resulted in a 260%improvement in the compressive strength of the SiBCN/SiOC composite aerogel compared with that of the pure SiBCN aerogel.Additional investigations revealed that the SiBCN/SiOC composite aerogel enjoyed a low thermal conductivity(0.044-0.051 W·m^(-1)·K^(-1))and a light weight(0.13-0.16 g·cm^(-3)),which was favorable for thermal barrier material.Notably,the SiBCN/SiOC composite aerogel exhibited excellent microwave absorption performance with an effective absorption bandwidth of 6.7 GHz and a reflection loss of−43.89 dB at a thickness of 2.5 mm due to improved impedance matching,multiple reflections,and enhanced interfacial polarization.Furthermore,the introduction of SiOC significantly inhibited the crystallization of SiBCN at high temperatures.After heat treatment at 1600℃,the composite aerogel retained its amorphous nanoparticle pearl-chain-like structure,with thermal conductivity remaining as low as 0.052 W·m^(-1)·K^(-1).The in situ introduction of PHMS provided novel insight and a promising strategy for enhancing the overall performance of SiBCN ceramic aerogels,expanding their application in hightemperature environments.展开更多
Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures ...Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures were prepared through digital light processing(DLP)3D printing,polymer-derived ceramics(PDCs),chemical vapor infiltration(CVI),and oxidation technologies.The incorporation of the CVISiC phase effectively increases the dissipation capability,while the synergistic interaction between the gyroid structure and SiO_(2)phase significantly improves impedance matching performance.The SiOC/SiC/SiO_(2)composite achieved a minimum reflection loss(RL min)of-62.2 d B at 4.3 mm,and the effective absorption bandwidth(EAB)covered the X-band,with a thickness range of 4.1 mm-4.65 mm.The CST simulation results explain the broadband and low-frequency absorption characteristics,with an EAB of 8.4 GHz(9.6-18 GHz)and an RL min of-21.5 dB at 5 GHz.The excellent EM wave attenuation performance is associated primarily with polarization loss,conduction loss,the gyroid structure's enhancement of multiple reflections and scattering of EM waves,and the resonance effect between the structural units.The SiOC/SiC/SiO_(2)composite also demonstrated strong mechanical properties,with a maximum compressive failure strength of 31.6 MPa in the height direction.This work opens novel prospects for the development of multifunctional structural wave-absorbing materials suitable for broadband microwave absorption and load-bearing properties.展开更多
基金financially supported by the National Key R&D Program of China(No.2023YFB3711200)the National Natural Science Foundation of China(No.52572081).
文摘SiBCN ceramic aerogels have emerged as a new generation of integrated thermal insulation and microwave absorption materials but face great challenges in terms of mechanical properties,high-temperature stability,and absorption bandwidth in practical applications.Herein,SiBCN/SiOC composite ceramic aerogels were prepared by solvent thermal crosslinking,freeze-drying,and pyrolysis of precursors.Polyhydromethylsiloxane(PHMS)was introduced in situ by the hydrosilane addition reaction during the solvothermal process,which endowed the precursor aerogel with a complex and robust three-dimensional network structure and further resulted in a 260%improvement in the compressive strength of the SiBCN/SiOC composite aerogel compared with that of the pure SiBCN aerogel.Additional investigations revealed that the SiBCN/SiOC composite aerogel enjoyed a low thermal conductivity(0.044-0.051 W·m^(-1)·K^(-1))and a light weight(0.13-0.16 g·cm^(-3)),which was favorable for thermal barrier material.Notably,the SiBCN/SiOC composite aerogel exhibited excellent microwave absorption performance with an effective absorption bandwidth of 6.7 GHz and a reflection loss of−43.89 dB at a thickness of 2.5 mm due to improved impedance matching,multiple reflections,and enhanced interfacial polarization.Furthermore,the introduction of SiOC significantly inhibited the crystallization of SiBCN at high temperatures.After heat treatment at 1600℃,the composite aerogel retained its amorphous nanoparticle pearl-chain-like structure,with thermal conductivity remaining as low as 0.052 W·m^(-1)·K^(-1).The in situ introduction of PHMS provided novel insight and a promising strategy for enhancing the overall performance of SiBCN ceramic aerogels,expanding their application in hightemperature environments.
基金financially supported by National Natural Science Foundation of China(Grant Nos.12141203,52202083,W2421013)the Natural Science Foundation Project of Shaanxi Province(Grant No.2024JC-YBMS-450)+1 种基金the Sichuan Science and Technology Program(Grant No.2024YFHZ0265)the Open Project of High-end Equipment Advanced Materials and Manufacturing Technology Laboratory(Grant No.2023KFKT0005)。
文摘Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures were prepared through digital light processing(DLP)3D printing,polymer-derived ceramics(PDCs),chemical vapor infiltration(CVI),and oxidation technologies.The incorporation of the CVISiC phase effectively increases the dissipation capability,while the synergistic interaction between the gyroid structure and SiO_(2)phase significantly improves impedance matching performance.The SiOC/SiC/SiO_(2)composite achieved a minimum reflection loss(RL min)of-62.2 d B at 4.3 mm,and the effective absorption bandwidth(EAB)covered the X-band,with a thickness range of 4.1 mm-4.65 mm.The CST simulation results explain the broadband and low-frequency absorption characteristics,with an EAB of 8.4 GHz(9.6-18 GHz)and an RL min of-21.5 dB at 5 GHz.The excellent EM wave attenuation performance is associated primarily with polarization loss,conduction loss,the gyroid structure's enhancement of multiple reflections and scattering of EM waves,and the resonance effect between the structural units.The SiOC/SiC/SiO_(2)composite also demonstrated strong mechanical properties,with a maximum compressive failure strength of 31.6 MPa in the height direction.This work opens novel prospects for the development of multifunctional structural wave-absorbing materials suitable for broadband microwave absorption and load-bearing properties.
基金National Natural Science Foundation of China((51172279,51302317)Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan ProvinceAid Program for Innovative Group of National University of Defense Technology
