Lightweight electromagnetic interference (EMI) shielding materials under harsh environments are in urgent need to tackle the increasing electromagnetic pollution and hazards. Herein, carbon nanofiber aerogel (CNFA) modified silicon oxycarbide (CNFA/SiOC) composites were prepared following a precursor infiltration pyrolysis procedure by using three-dimensional CNFA as a skeleton. Their structures and mass densities (0.28-1.35 g cm−3) were tunable by adjusting the content of polysiloxane precursor in impregnating solution. The lightweight CNFA/SiOC composite featured with continuous conductive network and highly porous structure in SiOC matrix, resulting in high specific shielding effectiveness (up to 68.9 dB·cm3 g−1 with SETotal of 19.3 dB) due to enhanced conductance loss and multi reflection/scattering. When increasing the density, the CNFA/SiOC composite can deliver EMI shielding effectiveness as high as 27.5 dB due to the generation of defective carbon and carbon dangling bonds as well as abundant interfaces between CNFs and SiOC which induce polarization loss. Moreover, the CNFA/SiOC composite exhibits good oxidation resistance with SETotal retention of above 98% after heat treatment at 600°C for 2 h in air, which arises from the effective protection of CNFs by SiOC.

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Polymer-derived ceramic (PDC) coatings of considerable thickness can offer promising protection for metallic and superalloy substrates against oxidation and corrosion, yet the preparation remains challenging. Here, a SiOC/Al2O3/YSZ coating was prepared on a nickel alloy with a spraying method using Al2O3 and yttria-stabilized zirconia (YSZ) as passive fillers. The thickness can reach up to 97 μm with the optimal mass fraction and particle sizes of the passive fillers. A small or isolated SiOC phase is formed in the coating, which can effectively alleviate the shrinkage and cracking during the pyrolysis. The SiOC/Al2O3/YSZ coating exhibits low thermal conductivity and high bonding strength with the substrate. Moreover, the coating shows good thermal shock resistance between 800 °C-room temperature cycles and oxidation resistance at 1000 °C for 36 h. This work provides an effective guide for the design of thick PDC coatings to further promote their application in the thermal protective field.