RESUMEN
Carbon fiber composites have great application prospects as a potential electromagnetic (EM) wave-absorbing material, yet it remains extremely challenging to integrate multiple functions of EM wave absorption, mechanical strength, thermal insulation, and flame retardancy. Herein, a novel carbon fiber reinforced C/SiOC aerogel (CF/CS) composite is successfully prepared by sol-gel impregnation combined with an ambient drying process for the first time. The density of the obtained CF/CS composites can be controlled just by changing sol-gel impregnation cycles (original carbon fiber felt (S0), and samples with one (S1) and two (S2) impregnation cycles are 0.249, 0.324, and 0.402 g cm-3, respectively), allowing for efficient tuning of their properties. Remarkably, S2 displays excellent microwave absorption properties, with an optimal reflection loss of -65.45 dB, which is significantly improved than S0 (-10.90 dB). Simultaneously, compared with S0 (0.75 and 0.30 MPa in the x/y and z directions), the mechanical performance of S2 is dramatically improved with a maximum compressive strength of 10.37 and 4.93 MPa in the x/y and z directions, respectively. Moreover, CF/CS composites show superior thermal insulation capability than S0 and obtain good flame-retardant properties. This work provides valuable guidance and inspiration for the development of multifunctional EM wave absorbers.
RESUMEN
In this study, a heat-resistant adhesive was prepared using molybdenum-phenolic (Mo-PF) resin as the matrix and TiB2 particle as the ceramizable filler for bonding Al2O3 ceramic substrates. Firstly, Fourier transform infrared (FTIR) was used to characterize the chemical structure of the Mo-PF. Subsequently, thermo gravimetric analysis (TGA) and shear strength testing were employed to investigate the effects of heat treatment in different atmospheres on the thermal stability and residual bonding properties of the adhesive. To further explore the bonding mechanism of the adhesive after heat treatment in different atmospheres, scanning electron microscopy (SEM), compressive strength testing, and X-ray diffraction (XRD) were utilized to analyze the microstructure, mechanical strength, and composition evolution of the adhesive at different temperatures. The bonding strength of Al2O3 joints showed a trend of initially decreasing and then increasing after different temperature heat treatment in air, with the shear strength reaching a maximum value of 25.68 MPa after treatment at 1200 °C. And the bonding strength of Al2O3 joints decreased slowly with the increase of temperature in nitrogen. In air, the ceramicization reaction at a high temperature enabled the mechanical strength of the adhesive to rise despite the continuous pyrolysis of the resin. However, the TiB2 filler in nitrogen did not react, and the properties of the adhesive showed a decreasing tendency with the pyrolysis of the resin.