Strong hydrogen-bonding network-induced crystal growth and microstructural consolidation of bamboo fiber/MOC thermal insulation composites

Abstract

Driven by the low-carbon economy, the development of high-performance bamboo fiber-based magnesium oxychloride (MOC) composites offers significant potential for reducing energy consumption in modern manufacturing, yet the effective regulation of crystal structure of strengthening phase within the composites system remains challenge. Here, we developed high-performance bamboo fiber/MOC lightweight composites using a polyhydroxy-compound-induced crystallization strategy. Beyond improving the macroscopic properties of the composites, this study provided molecular-level insight into a possible mechanism underlying the induced crystallization of MOC hydrates. The combined experimental and simulation results suggest that hydrogen bonding and Mg²⁺ coordination between the polyhydroxy modifier and hydration species create a favorable local environment for hydrate association and 5-Phase crystallization. On this basis, we propose that the modifier acts as a molecular template that organizes hydration species in the vicinity of growing 5-Phase (5 Mg(OH)₂·MgCl₂·8H₂O) crystals. The resulting hydrogen-bonding interactions may stabilize local crystal assembly and suppress defect formation, thereby favoring the development of a denser and more stable crystalline architecture. Compared with conventional bamboo-fiber/MOC composites, our composites contained substantially fewer loose and defective crystal structures, leading to a 62% increase in compressive strength, a 35% increase in specific strength and an approximately 50% decrease in water absorption. They nevertheless remained ultralight inorganic foams, with a bulk density of 0.42 g cm⁻³, and maintained excellent thermal insulation, with a thermal conductivity of 0.079 W m⁻¹ K⁻¹. These findings offer a strategy for precise control over the crystal structure of composites and provide a foundation for the development of advanced functional biomass-based inorganic composites.