High strength SiC porous ceramics fabricated by digital light processing
image: SiC powder was oxidized to formed a SiO2 shell with low refractive index, which was mixed with white-colored Al(OH)3-Y2O3-CaF2 complex additives to enhance the light curing performance of deep-colored SiC slurries. The solid content of the slurry can reach 55vol% with acceptable low viscosity. Complex structured SiC lattices were successfully printed and its flexural strength (even with an apparent porosity of ~40%) is dramatically enhanced by converting SiO2 into mullite bond phase via rational design of sintering additives and sintering process in air.
Credit: Journal of Advanced Ceramics, Tsinghua University Press
Silicon carbide (SiC) ceramics are widely used in a variety of applications such as thermal insulation, filters, catalyst carriers, biological and aerospace due to their excellent properties. Different application environments have more stringent requirements for ceramic structures in usual, and photocuring 3D printing technology enables the preparation of ceramic parts with complex structures, paving the way for the promotion of SiC ceramics in a wide range of applications.
Recently, Guifang Han's team at Shandong University prepared SiC components with complex shapes by introducing a pre-oxidation treatment assisted by light-curing 3D printing and a composite sintering additive system of Al(OH)3-Y2O3-CaF2, which transformed the SiO2 introduced by oxidation into a mullite reinforcing phase, and sintered them in air atmosphere. This study aims to explore the low-cost preparation of complex ceramic structural components, which provides a feasible strategy to achieve dark-coloured ceramics by light curing 3D printing.
The team published their work in Journal of Advanced Ceramics on January 18, 2024.
“In this work, we have systematically investigated the influence laws of the pre-oxidation treatment regime and sintering additives addition on the properties of SiC pastes, and the mullite-bonded SiC ceramics prepared by sintering in air atmosphere have excellent flexural strength, and complex shaped SiC building blocks have been successfully prepared. This study provides a feasible strategy to enhance the photocuring ability of SiC slurry and their strength.” said Guifang Han, corresponding author of the article and a professor at Shandong University's School of Materials Science and Engineering.
Dark-coloured SiC is highly light-absorbing and its refractive index is much higher than that of the resin, which severely reduces the depth of light penetration and the amount of light available to the photosensitive resin. To solve this problem, researchers have been oxidizing SiC powders at high temperatures to improve the curing properties of SiC slurry by in-situ generating a SiO2 shell layer on their surface. However, the low strength of SiO2, the phase transition and accompanying 4.5% volume change during cooling, and the large difference in the coefficients of thermal expansion between SiO2 and SiC make for weak bonding, and poor performance of the printed SiC ceramics greatly limit their practical application.
The research team has made progress in improving the performance of SiC ceramic slurry by forming a SiO2 shell, and then convert this shell into high strength mullite. "The excellent properties of SiC ceramics are due to their very strong Si-C covalent bonds, but they also make them equally difficult to sinter. In addition, the high strength and hardness of SiC ceramics make them difficult to machining, which limits the complexity of the shape of SiC components," said Guifang Han.
The research team expects that the study will facilitate the realization of new usage requirements for traditional ceramic materials in multiple applications, responding to complex environmental and usage requirements in material application scenarios." Ceramic materials prepared based on light-curing 3D printing can directly meet the requirements for material structure and performance. High-performance materials that are structurally designable are the way forward for traditional materials to take on a new lease of life. " Han Guifang said.
Other contributors include Jingde Zhang, Xu Zhang, Zihe Li, Sijie Wei, Weibin Zhang, Weili Wang from the School of Materials, Shandong University, China, and Jianzhang Li from the National Engineering Research Centre for Ceramic Matrix Composites Manufacturing Technology.
This work was supported by Shandong University-MSEA International Institute for Materials Genome Joint Innovation Center for Advanced Ceramics, and the Key Research and Development Projects of Shaanxi Province (Nos. 2018ZDCXLGY-09-06 and 2021ZDLGY14-06)
About Author
Prof. Guifang Han is currently a full professor in Shandong University, China. Her current research interests are high temperature structural ceramics, composites, environmental barrier coatings, integration of structures and functions, as well as advanced fabrication technologies including additive manufacturing, fast sintering and so on. Prof. Han has published more than 90 papers. For more details, please refer to her profile at http://www.en.cmse.sdu.edu.cn/info/1007/1096.htm and publication list at https://orcid.org/0000-0001-6220-6424.
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic 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, and exclusively available via SciOpen. JAC’s 2023 IF is 18.6, ranking in Top 1 (1/31, Q1) among all journals in “Materials Science, Ceramics” category, and its 2023 CiteScore is 21.0 (top 5%) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
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