Journal of the Chinese Ceramic Society, Volume. 53, Issue 2, 437(2025)
Research Progress on Design, Preparation and Influential Mechanism of Prestressed Ceramics
It is well known that the compressive stress in surface layer can significantly improve the flexural strength and impact resistance of brittle materials, such as prestressed concrete and tempered glass. For the past century, many prestressed concrete and tempered glass have been manufactured successfully and widely used in various fields. However, little progress has been made for ceramic materials because of the high melting temperature and the intrinsic brittleness of ceramics. How to achieve the preset compressive stress on the ceramic surface is the key issue for prestressed ceramic research. This work introduces two ways for the formation of compressive stress on ceramic surface, namely surface coating method and surface extrusion method. Both advanced ceramics and traditional ceramics can use prestressing reinforcement to significantly improve the strength and durability of ceramic components. For advanced oxide ceramics, prestressing can increase the flexural strength by 40%–50%, while for traditional ceramics, the strength can be doubled. In addition, the structural-functional integration of the alumina ceramic substrate was achieved, i.e. both the strength and thermal conductivity of alumina sample were improved through the mixed coating. Besides, prestress strengthening method was applied to prepare the high-performance and mechanically stable solid electrolyte. Due to the sufficiently high compressive stress in the surface layer of solid electrolyte, cracks and dendrite penetration were restrained. Therefore, a controllable and long-life solid electrolyte was obtained. In general, by introducing compressive stress in the surface layer of ceramics, the fracture energy and impact resistance of ceramics were improved effectively.The main factors affecting surface prestressing by coating method are the ratio of expansion coefficient and the ratio of elastic modulus between the coating and the substrate material, as well as the ratio of cross-sectional area. It was found that, to generate the compressive stress on ceramic surface by coating method, it is required that the coating material has a lower coefficient of thermal expansion (CTE) and similar sintering temperature relative to the substrate. The optimal CTE condition for a pre-stressed ceramic component was described as αc/αs<0.83. Besides, both theoretical analysis and experimental results show that the compressive stress and crack resistance in the surface layer increase with the increasing ratio of the cross-sectional area of substrate to coating. While the main influencing factors of surface extrusion method are the temperature and time of ion exchange. As the temperature and the time of ion exchange increasing, the effect of prestress reinforcement improved firstly and then remained unchanged.Furthermore, inspired by the design of pre-stressed ceramics, the sintering deformation of Al2O3 components would be controlled by taking advantage of the difference in shrinkage between substrate and coating. By adjusting the composition and the position of coating, the Al2O3 ceramics with different shapes can be fabricated successfully. Besides, according to the deformation level, this method can be used to select the suitable coating raw materials. Generally, the way to fabricate the shape controlled ceramic components by the gradient shrinkage is a novel and effective method, which can be used for the plate and shell products with complex shapes.It is well known that the residual stress is not a constant. It is related to the position, the ratio of CTE of substrate to coating, interface bonding, and so on. The form and the magnitude of residual stress affect the mechanical properties of specimens. Hence, the evaluation of residual stress in prestressed ceramics is very important for their engineering applications. To evaluate the residual stress in prestressed ceramics, indentation deformation was used to illuminate the effect of residual stress on crack propagation. By comparing the length and the expanded direction of crack in ceramics with and without coating, the form of residual stress was cleared. Results show that the compressive stress could hinder the crack extension, while the tensile stress could promote the crack extension. Besides, the residual stress could be calculated via relative method. The formula derivation and experimental results show that the residual stress is determined by the elasticity modulus, the coefficient of thermal expansion, the cross-sectional ratio of the coating to the substrate and the temperature and the temperature. And it decreases with increasing temperature because of the stress relaxation.Summary and prospectsBy introducing preset compressive stress on the ceramic surface through the surface coating method or the surface extrusion method, the flexural strength and impact resistance of pre-stressed ceramics could be improved significantly. The relative research shows that the flexural strength of structural ceramics, architectural ceramics and domestic ceramics prepared by this new method could increase by 50%, 70% and 100%, respectively. The simple and economical pre-stressing design has shown great application prospects in the architectural ceramics, domestic ceramics, structural ceramics and structural–functional integration ceramics. Moreover, there is no limitation of size and shape in the fabrication of pre-stressed ceramic components, which is suitable for production of industrialization.
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BAO Yiwang, LI Yueming, WAN Detian, LI Haiyan, ZHANG Xiaona, FU Shuai, SUN Yi, LI Kai. Research Progress on Design, Preparation and Influential Mechanism of Prestressed Ceramics[J]. Journal of the Chinese Ceramic Society, 2025, 53(2): 437
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Received: Sep. 20, 2024
Accepted: Feb. 20, 2025
Published Online: Feb. 20, 2025
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