A recent study published in the journal Materials Today Physics focuses on the development of bio-inspired, extremely hard quaternary nanocomposites for increasing the toughness of ceramic composites.
Study: Macro-micro-nano multistage toughening in nano-laminated graphene ceramic composites. Image Credit: BONNINSTUDIO/Shutterstock.com
While conventional techniques such as particulate distribution, phase transition, and flake hardening can be used to toughen ceramics, these methods often have a detrimental effect on the durability and strength of the composites. This issue can be resolved by using structural principles derived from research on biomaterials such as bamboo and pearls.
Ceramics: Applications and Limitations
High thermal consistency, abrasion resistance, and remarkable tensile characteristics are some of the advantages that ceramics have over other materials. These characteristics make them the preferred material for cutting-edge structural and functional applications such as high-speed milling equipment, medical instruments and systems, gasoline components, aviation components, and high-voltage batteries. Ceramics are also used in mass transit systems and for power storage.
However, there is still a mismatch between the qualities of commercially available ceramics and the attributes required for next-generation applications. Ceramics are likely to crack because of their ionic and, or, covalent bonding, leading to high defect sensitivity and low durability. As a result, the ceramic industry requires more damage-resistant materials, making the development of advanced ceramic materials critical.
When it comes to advanced ceramic composites, toughening is always needed to increase efficiency and durability. Toughening techniques can be divided into two categories: internal and external. Internal processes have the most significant effect on fracture onset toughness because they work ahead of the crack tip. In contrast, external mechanisms greatly impact crack growth resistance because they work behind the crack tip.
Traditional Ceramic Toughening Techniques
Particulate-dispersion toughening, phase transition toughening, whisker toughening, and synergic toughening are some of the traditional ceramic toughening techniques used in the industry. Toughening by particle-dispersion is done by inhibiting crack initiation and propagation through proper distribution of second-phase nanoparticles, including metal matrix phase and ceramic phase particulates.
Transformation toughening improves the hardness of ceramic materials by fine-tuning the ceramic structure to produce stress-induced transitions at ambient temperatures. Whisker/fiber toughening increases the matrix's toughness by incorporating high-modulus whiskers into the ceramic phase.
Through the use of several reinforcements, synergic toughening also improves matrix toughness because combining multiple toughening techniques produces better results than a single method.
New-Concept Ceramic Toughening Techniques
Nanofiber reinforcement, CNT toughening, in-situ self-toughening, and laminated structural toughening are examples of new-concept toughening processes. Nanofiber reinforcement greatly improves the toughness of ceramic composites by introducing a second phase at a nanometer scale.
CNT toughening is a technique that uses carbon nanotubes as a reinforcing agent to increase the toughness of a ceramic matrix. CNTs have a large aspect ratio and remarkable thermophysical characteristics, resulting in a significant increase in toughness. In-situ self-toughening approaches attempt to increase the hardness of the ceramic phase using self-toughening elements such as extended grains, fractal grains, and fibers.
Laminated structural toughening increases the strength of the ceramic phase by producing compressive forces on the top layer and by altering the interlace dispersion using the difference in coefficient of expansion between adjacent layers in the ceramic particles.
With the advancement of nanomaterials and associated areas, work on strong and tough ceramics has progressed from conventional toughening to new-concept toughening. Graphene has emerged as the most potential reinforcement material for hardening ceramics, owing to its tiny size, intrinsic 2D sheet composition, high abundance, and environmental friendliness.
In this study, the researchers used graphene to design and develop complex designs spanning multiple sizes inside the ceramic phase by using a bottom-up construction strategy. Multiple stage toughening methods were established by combining components and laminated structural approaches to achieve the highest performance for advanced ceramic composites.
Conclusion and Prospects
At varying time and spatial scales, all of the suggested macro-micro-nano multistage toughening processes successfully dispersed energy, transferred the load applied, and alleviated high local pressures, boosting fracture toughness without losing the nanocomposites' rigidity. To produce an improved ceramic nanocomposite, these findings focus on the importance of careful design and selection of materials to discover the important processes leading to enhanced mechanical efficiency.
This study provides a suitable approach for developing tough ceramic materials for applications in optoelectronics, information technology, industrial production, shipping, healthcare, defense, and space travel by successfully developing a combination of toughening methods ranging from nanoscopic to macroscopic scale.
Continue reading: The Role of Structural Engineering in Nanotechnology.
Sun, J. et al. (2021) Macro-micro-nano multistage toughening in nano-laminated graphene ceramic composites. Materials Today Physics. Available at: https://www.sciencedirect.com/science/article/abs/pii/S254252932100256X
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