Hexavalent chromium (Cr(Ⅵ)) is a highly toxic and carcinogenic heavy metal pollutant, posing serious threats to the environment and human health. The development of efficient and cost-effective adsorbents is crucial for treating Cr(Ⅵ)-containing wastewater. In this study, porous carbon aerogels (CAs) with a three-dimensional network structure were prepared using resorcinol-formaldehyde as precursors and polydiallyldimethylammonium chloride (PDADMAC) as a soft template via sol-gel method, ambient pressure drying, and high-temperature carbonization. The regulation of PDADMAC dosage on the microporous structure of the carbon aerogels was systematically investigated, and their performance as adsorbents for the removal of Cr(Ⅵ) from water, as well as their compressive properties, were thoroughly evaluated. The results demonstrated that by adjusting the amount of PDADMAC, the pore structure of the carbon aerogels could be effectively tailored, achieving a transition from microporous to mesoporous structures. Adsorption experiments revealed that the abundant mesoporous structure provided low-resistance mass transfer channels for Cr(Ⅵ) compounds, resulting in an adsorption capacity of 102.34 mg·g^-1 while maintaining compressive strength up to 7.08 MPa. The adsorption kinetics followed the pseudo-second-order model and the intra-particle diffusion model, which indicated that the process was dominated by chemical adsorption and exhibited multi-stage adsorption characteristics. This study demonstrates the preparation of high-performance carbon aerogels through structural regulation, offering a feasible strategy for the efficient adsorption of heavy metal Cr(Ⅵ).

The aircraft engine firewall prevents the spread of flames and high temperatures to other parts of the aircraft, curbing fire escalation and buying critical time for crew members to respond to emergencies, thereby reducing risks to aircraft structures and personnel. It also effectively blocks heat transfer from the engine, avoiding performance degradation and material aging in adjacent structures due to prolonged thermal exposure, thus ensuring the stability and safety of surrounding equipment and structures. This study addresses issues such as heavy weight, installation challenges, high production and maintenance costs, and lengthy cycles associated with existing aviation engine firewall materials by developing and evaluating the properties of Al₂O_3f/Al₂O₃-SiC ceramic matrix composites. Experimental results demonstrate that the Al₂O_3f/Al₂O₃-SiC composite exhibits excellent mechanical properties, including a tensile strength of 103 MPa, tensile modulus of 45.2 GPa, compressive strength of 256 MPa, compressive modulus of 106 GPa, flexural strength of 189 MPa, flexural modulus of 106 GPa, and interlaminar shear strength of 12.1 MPa. Damage modes involve matrix cracking, interfacial layer delamination, fiber pull-out, and fiber bundle fracture. Additionally, the composite demonstrates superior flame penetration resistance. Compared to conventional titanium alloy firewall materials, it achieves a weight reduction exceeding 40%.

the development of radar detection technology puts forward higher stealth requirements for the hot-end components of weapons and equipment, and high-temperature absorbing composite materials are the key materials to solve the problem of radar stealth, which have important application prospects and strategic significance. Therefore, domestic and foreign researchers have conducted a lot of research on absorbing materials. This paper introduces the different absorption principles of electromagnetic waves, including magnetic loss type, dielectric loss type and electric loss type. The latest research progress of common high-temperature absorbing materials such as carbon-based, metal-based, ternary layered compounds and ceramic-based absorbing composites is reviewed. Carbon-based materials (graphite, carbon black, graphene, carbon nanotubes, etc.) mostly use composite high temperature resistant materials to exert their absorbing properties and solve the problem of high temperature oxidation. Metal oxide materials (ZnO, MnO₂, Fe₃O₄, etc.) increase the interfacial polarization loss by adjusting the microstructure of the material. Ternary layered compound materials (mainly Ti₃SiC₂) are mainly used in different thermal stability matrices such as Al₂O₃ and cordierite to solve the problems of purity and high temperature oxidation. Due to the excellent thermal stability, Ceramic absorbing materials have become the most studied category at relatively high temperatures. This paper summarizes the latest research progress of SiC binary and SiCN, SiOC, SiBCN multi-ceramic absorbing materials. SiC binary absorbing materials mostly use element doping and microstructure control to improve the absorbing properties. SiCN ternary absorbing materials have excellent dielectric properties. At present, most of the research adopts the method of composite magnetic particles (Fe, Co, Ni). SiOC ternary absorbing materials have low cost and good electrical conductivity. Researchers have further developed their absorbing properties by adding ultra-high temperature ceramics, BN and other second-phase components. The measures to improve the absorbing properties of SiBCN quaternary absorbing materials mainly include material compounding (high dielectric constant materials or transition metals) and precursor molecular structure adjustment. Finally, the development trend of high temperature absorbing composites is prospected from the aspects of absorbing bandwidth, temperature resistance and multi-frequency compatible stealth, aiming to provide new research ideas for the development of new absorbing materials in the future.

SiC/SiC composites were prepared by precursor infiltration and pyrolysis process combined with three matrix modification methods. The effect of matrix modification on the high temperature oxidation resistance of SiC/SiC composites was analyzed by morphology analysis and mechanical property test. The results showed that the flexural strength of the matrix-modified composites hardly decreases after 100h static oxidation at 1200℃. After 200h oxidation, the retention rates of flexural strength reached 80%. After 300h oxidation, the internal structure of the composites was not oxidized and the oxidation degree of the interface layer in the surface area decreases. The B element in the modified matrix was oxidized to form liquid phase to seal the surface of SiC coating, which delayed the oxidation process of SiC coating, preventing the oxidation medium from entering the interior of the compo-site and protects the fiber and interface layer, so that the long-term static oxidation resistance of SiC/SiC composites was improved significantly.