Scientists develop innovative method to simplify production process of cellular ceramics

Cellular ceramics are widely used ceramic materials known for their stable performance, erosion resistance and long service life. A research team led by Associate Professor YANG Zhengbao from the Department of Mechanical and Aerospace Engineering at HKUST designed a two-step surface tension-assisted processing strategy (STATS) to fabricate cellular ceramics with programmed 3D cell-based configurations. The approach involves two key steps: (1) preparing organic cellular networks aided by additive manufacturing to build the basic configurations and (2) filling the precursor solution with the required component in the designed network.

One of the biggest challenges was controlling the geometry of the liquid. To overcome this, the team used surface tension, a natural phenomenon, to trap the precursor solution in engineered cellular networks. By using the ability of surface tension to trap and pin liquids in the prepared networks, they were able to effectively control the geometry of the liquid and produce cellular ceramics with high precision.

The team further investigated the geometric parameters for architectural trusses assembled by unit cells and unit columns, both theoretically and experimentally, to guide the formation of a 3D fluid interface in ordered configurations. After drying and high-temperature sintering, the architectural cellular ceramics were obtained. Using the new STATS approach, the synthesis of components was decoupled from the architecture building, enabling the programmable production of cellular ceramics with different cell sizes, geometries, densities, meta-structures, and building blocks. Due to its high programmability, the method is applicable to both structural ceramics (e.g. Al2O3) and functional ceramics (e.g. TiO2, BiFeO3, BaTiO3).

To verify the superiority of this method, the researchers also investigated the piezoelectric performance of cellular piezoceramics. They found that the proposed approach can reduce micropores and improve local compactness in the sintered cellular ceramics due to the significantly reduced organic content in the raw material. This process is beneficial in producing globally porous and locally compact cellular piezoceramics, achieving a relatively high piezoelectric constant d33 (~200 pC N-1) even at very high overall porosity (>90%).

Prof. Yang revealed that the method was inspired by diatoms, which are algae commonly found in sediments or attached to solids in water and serve as food directly and indirectly for many animals. Unicellular diatoms are characterized by a distinct siliceous frustule or outer cell wall. Through a genetically programmed biomineralization process, their frustules are built into highly precise structures that exhibit a variety of morphologies, shapes, geometries, pore distributions, and assembly.

“Our strategy overcomes the limitations of conventional manufacturing methods and enables the creation of programmable, geometrically complex ceramic architectures. This novel approach can help process numerous structural and functional cellular ceramics, contributing to applications including filters, sensors, actuators, robotics, battery electrodes, solar cells, and germicidal devices. Furthermore, the fluid-to-solid interface engineering philosophy also provides a new solution for combining interface processing with innovative manufacturing, illuminating the synergistic development of advanced design and smart materials,” explained Prof. Yang.