Since the brittle characteristics of porous ceramics, high mechanical strength is the most important prerequisite among the fundamental requirements especially when used as the supports. Particle grading strategy has been intensively extended in the preparation of porous ceramics to improve the mechanical strength. Unfortunately, this usually accompanies with the notable sacrifice in porosity. The trade-off between the mechanical strength and porosity is well recognized in the field of porous ceramics, and attempts have been increasingly devoted to overcome the issue.
Recently, a research team led by Prof. Weihong Xing from Nanjing Tech University, Jiangsu Province, China proposed a reverse particle grading strategy based on the linear packing model, which enabled the preparation of porous ceramic with both high porosity and mechanical strength. They developed the strategy to prepare single-channel tubular supports and investigated the effect of reverse particle grading strategy on the ceramic paste, macroscopic properties, and microstructure of supports. Also, the strategy was proved to be feasible in the fabrication of 19-channel SiC tubular ceramic supports.
The team published their work in Journal of Advanced Ceramics on May 22, 2024.
"Particle size gradation is a common practice in the fabrication of advanced ceramics, which can regulate the mobility, plasticity and viscosity of the ceramic powder and pastes. While most of them prefers to the addition of fine particles into the coarse powder matrix. This usually results in the simultaneous increase in mechanical strength and density, which is evidently not the target of porous ceramics. In our recent work, a new concept-reverse particle grading strategy was developed based on the linear packing model by unusually introducing coarse particles into fine particles matrix. Tubular porous SiC ceramic supports with improved mechanical strength and maximum porosity were realized." Said Dr. Qilin Gu, the corresponding author of the paper, a professor in State Key Laboratory of Materials-Oriented Chemical Engineering, National Engineering Research Center for Special Separation Membrane, Nanjing Tech University.
With the increasing content of coarse SiC particles to 30 wt%, the pressure generated in extrusion process decreased from 5.5 ± 0.2 MPa to 1.3 ± 0.1 MPa. Notably, the bending strength of tubular supports increased from 36.6 ± 5.6 MPa to 49.1 ± 4.5 MPa when incorporating 20 wt% of coarse powders. The notable improved mechanical strength was attributed to the distribution of coarse particles that prolonged the route of crack deflection. Also, the optimized tubular supports showed an average pore size of 1.2 ± 0.1 μm and open porosity of 45.1 ± 1.6 % and water permeability of 7163 ± 150 L·m-2·h-1·bar-1 and good alkali and acid corrosion resistances. "We believe that the concept-reverse particle grading strategy will serve as a cost-efficient alternative to prepare porous ceramics with high mechanical strength and porosity." Qilin Gu said.
In the future, their efforts will be devoted to further optimize the recipe and processing parameters for scalable fabrication of SiC tubular porous ceramic supports. It is believed that the concept of reverse particle grading strategy can benefit the development of other porous ceramics.
Other contributors including Zheng Liang, Han Zhang, Yichuan Li, Wenkang Zhang, Jian Zhou, Zhaoxiang Zhong are all from Nanjing Tech University, Nanjing, China.
This work was financially supported by the National Key Research and Development Project of China (2022YFB3805002), the Natural Science Foundation of China (22308150), the Research Programs of the Science and Technology of Guangxi Zhuang Autonomous (GUIKE-AA22117015-1), the Natural Science Foundation of Jiangsu Province (BK20220345), Key Research and Development Program of Jiangsu Province (No. BE2023360), Key Research and Development Project of Nanjing Jiangbei New Area (ZDYF202203) and Youth Science and Technology Talents Lifting Project of Jiangsu Association of Science and Technology (105019ZS_007).
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press on behalf of the State Key Laboratory of New Ceramics and Fine Processing (Tsinghua University) and the Advanced Ceramics Division of the Chinese Ceramic Society, and exclusively available via SciOpen. JAC has been indexed in SCIE (IF = 16.9, top 1/28, Q1), Scopus, and Ei Compendex.
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