Carbonized Composites Containing Silica Aerogels with Enhanced Hydrophobicity and Thermal Insulation via Glass Fiber and Hollow Microsphere Reinforcement

Facing the increasingly severe energy challenges and environmental problems, the development of thermally stable, lightweight, and thermal insulating materials is critical. Herein, we report an organic-inorganic composite strategy combined with a high-temperature carbonization step to fabricate aerogel-containing composites synergistically reinforced with chopped glass fibers and hollow glass microspheres. By systematically varying the ratio of acrylic emulsion to potassium silicate solution, we investigated the effects on the forming behavior, microstructure, hydrophobicity, thermal stability, and thermal insulation performance. Increasing the acrylic emulsion fraction substantially enhanced hydrophobicity, yielding a maximum water contact angle of 129.3°. Concurrently, the apparent density decreased from 0.18 g/cm3 to 0.09 g/cm3 and the thermal conductivity dropped from 57.9 mW/(m·K) to 29.0 mW/(m·K). Mechanical testing revealed that the compressive Young’s modulus decreased with increasing acrylic content, from 3.6 MPa for the purely inorganic sample to 0.55 MPa at 70% acrylic content, reflecting a trade-off between stiffness and organic-derived porosity. Microstructural characterization revealed a hierarchical porous network in which uniformly dispersed hollow glass microspheres and the aerogel-derived silica network form an efficient thermal barrier system. Thermogravimetric analysis demonstrated excellent thermal stability, with total weight loss below 5% up to 800 °C. Infrared thermography analysis showed that, after unilateral heating at 300 °C and 400 °C for 10 min, the backside surface temperature of the composites decreased as the acrylic emulsion content increased. At 300 °C, the temperature decreased from 176.1 °C for AP-1 to 151.0 °C for AP-4, while at 400 °C, it decreased from 228.5 °C to 199.3 °C. These results indicate that the composites exhibit effective thermal insulation and maintain structural stability under high-temperature exposure. Taken together, this facile and scalable approach yields these aerogel-containing composites that combine low density, low thermal conductivity, robust structural integrity, and good environmental resistance, as evidenced by a water contact angle of 129.3°, making them promising candidates for aerospace, building, and industrial high-temperature insulation applications.