Ambient Pressure Drying of Freeze-Cast Ceramics from Aqueous Suspension

Abstract

Freeze-casting has been wildly exploited to construct porous ceramics but usually requires costly and demanding freeze-drying (high vacuum, size limit, and supercooled chamber), which can be avoided by the ambient pressure drying (APD) technique. However, applying APD to freeze-cast ceramic based on an aqueous suspension is still challenging due to inert surface chemistry. Herein, a modified APD strategy is developed to improve the drying process of freeze-cast ceramics by exploiting the simultaneous ice etching, ionic cross-linking, and solvent exchange under mild conditions (−10–0 °C, ambient pressure). This versatile strategy is applicable to various ceramic species, metal ions, and freezing techniques. The incorporated metal ions not only enhance liquid-phase sintering, producing ceramics with higher density and mechanical properties than freeze-cast counterparts, but also render customizable coloration and antibacterial property. The cost-/time-efficient APD is promising for mass production and even successive production of large-size freeze-cast ceramics that exceed the size of commercial freeze-dryers.

An Anisotropic Noncombustible Nanocomposite Based on a Fiberglass–Chitosan 3D Network for Building Insulation

“…A great interface between organic/inorganic parts is critical and has a direct influence on materials’ mechanical properties and construction performance. , Introducing inorganic materials with functional groups such as hydroxyl into organic substances can effectively improve the interface and enhance the mechanical properties of the composite materials. − However, the extremely high interface can lead to the interlocking of inorganic components, forming thermal bridges and thus leading to an increase in the thermal conductivity. − Therefore, preparing porous materials with high mechanical performance, high fire resistance, and high thermal insulation performance is of great significance but faces significant challenges. Constructing anisotropic porous organic/inorganic composites with oriented hierarchical porous structures could be an approach to address the aforementioned issues. − The organic component forms the material framework, while the inorganic component imparts excellent fire resistance to the composite material. , The anisotropic porous structure could be obtained by freeze orientation processes. , An excellent dispersion of solutes in low-temperature aqueous solvents is critical for the freeze orientation processes to obtain oriented hierarchical porous structures in anisotropic materials. − …”

Engineering High-Performance Composite Cellulose Materials for Fast Hemostasis

“…In fact, the drying step significantly affects the crystallinity and porosity of regenerated cellulose materials (e.g., cellulose aerogel). Various drying methods have been attempted, including freeze drying, supercritical fluid drying, ambient pressure drying, vacuum drying, and microwave drying . Among these, freeze drying and supercritical fluid drying are popular.…”