External magnetic field-guided fabrication of gelatin/gellan gum gradient aerogels for efficient thermal insulation.

Abstract

This study developed a magnetic-field-assisted strategy to fabricate aerogels with position-dependent pore structures and enhanced freeze-drying stability. Amino-functionalized Fe3O4 nanoparticles were electrostatically complexed with gelatin chains to form a magnetically responsive network. Heat-responsive gellan gum was then introduced as a second physical network to help preserve the field-associated structural heterogeneity. The regional differences in gelatin content, apparent magnetic recovery, and cross-sectional pore morphology are consistent with field-associated redistribution or local enrichment of the Fe3O4-NH2-gelatin phase. Such redistribution, if it occurs, may contribute to the cross-sectional pore-size changes observed after freeze-drying. Across the tested nominal field conditions, higher field settings were associated with progressively larger descriptive differences in the SEM-derived apparent pore-size metric among the sampled positions. However, the limited number of independently prepared specimens did not support a reliable field condition × position interaction analysis. The dual-network aerogel exhibited low density, orientation-dependent transient thermal responses, and apparent surface-temperature attenuation. Compared with single-network aerogels, the gellan gum network improved skeletal integrity and structural stability after freeze-drying. This strategy offers a potentially simple approach to preparing bio-based aerogels with position-dependent pore structures. The resulting aerogels show preliminary potential for thermal management and infrared thermal-signature attenuation under controlled conditions. However, the environmental stability and moisture resistance of these aerogels, as well as their long-term aging behavior and durability under repeated thermal cycling, require further evaluation before practical deployment.