High-strength and multi-functional gypsum with unidirectionally porous architecture mimicking wood

Abstract Porous gypsum materials are of notable significance and demonstrate a broad application in construction and biomedical engineering; nevertheless, it is challenging to simultaneously enhance their mechanical and functional properties. Here by replicating the designs of natural wood, new gypsum materials containing unidirectional micro-pores were fabricated by employing a modified ice-templating technique. The retention of ice-templated architectures was realized based on the hydration-induced self-hardening characteristic of gypsum without using the traditionally long-time freeze drying treatment. The porosities of the wood-like gypsum can be readily adjusted in wide ranges from lower than 60 vol.% to over 80 vol.% by controlling the solid loads in initial slurries. The wood-like gypsum exhibits a notable improvement in compressive strength and energy absorption efficiency along the lamellar direction by more than twofold compared to the unfrozen gypsum materials containing random pores of similar porosity. Additionally, it displays the lowest level of thermal conductivity among gypsum materials along the normal direction of lamellae, which ranges from above 0.21 to ∼0.1 W (m K)−1 depending on porosity, thereby demonstrating an outstanding effectiveness for thermal insulation. It can also be easily modified from hydrophilic to hydrophobic towards enhanced water resistance. The high strength and multi-functionalities along with the feasible fabrication approach make the wood-like gypsum appealing for applications, e.g., as construction and biomedical materials. The unidirectionally open pores may also provide new possibilities for regulating the cell behavior in gypsum-based bone implants.