Tempering Methods for High Performance Ceramic Composites

A recent study published in the journal Materials Today Physics focuses on the development of bio-inspired, extremely hard quaternary nanocomposites to increase the toughness of ceramic composites.

Study: Macro-micro-nano multi-step quenching in nano-laminated graphene ceramic composites. Image Credit: BONNINSTUDIO/Shutterstock.com

Although conventional techniques such as particle distribution, phase transition, and flake hardening can be used to harden ceramics, these methods often have a detrimental effect on the durability and strength of composites. This problem can be solved by using structural principles from research on biomaterials such as bamboo and beads.

Ceramics: applications and limits

High thermal consistency, abrasion resistance and remarkable tensile characteristics are some of the advantages of ceramics over other materials. These characteristics make it the material of choice for advanced structural and functional applications such as high-speed milling equipment, medical instruments and systems, gasoline components, aviation components, and high-voltage batteries. Ceramic is also used in mass transit systems and for energy storage.

However, there is still a mismatch between the qualities of commercially available ceramics and the attributes required for next-generation applications. Ceramics are prone to cracking due to their ionic and/or covalent bonding, resulting in high defect susceptibility and low durability. As a result, the ceramic industry requires materials that are more resistant to damage, making the development of advanced ceramic materials critical.

When it comes to advanced ceramic composites, quenching is always required to increase efficiency and durability. Tempering techniques can be divided into two categories: internal and external. Internal processes have the greatest effect on fracture initiation toughness because they act upstream of the crack tip. In contrast, external mechanisms have a large impact on the resistance to crack growth because they act behind the tip of the crack.

Traditional ceramic tempering techniques

Particle dispersion quenching, phase transition quenching, whisker quenching, and synergistic quenching are some of the traditional ceramic quenching techniques used in industry. Particle dispersion hardening is achieved by inhibiting crack initiation and propagation through proper distribution of second phase nanoparticles, including metal matrix phase and ceramic phase particles.

Transformation hardening improves the hardness of ceramic materials by refining the ceramic structure to produce stress-induced transitions at room temperature. Tempering the whiskers/fibers increases the toughness of the matrix by incorporating high modulus whiskers into the ceramic phase.

Through the use of multiple reinforcements, synergistic quenching also improves die toughness because combining multiple quenching techniques produces better results than a single method.

New concept ceramic tempering techniques

Nanofiber reinforcement, CNT quenching, in-situ self-hardening and laminated structural quenching are examples of new concept quenching processes. Nanofiber reinforcement significantly improves the toughness of ceramic composites by introducing a second phase at the nanoscale.

CNT quenching 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, which results in a significant increase in toughness. In-situ self-hardening approaches attempt to increase the hardness of the ceramic phase by using self-hardening elements such as extended grains, fractal grains, and fibers.

Layered structural tempering increases the strength of the ceramic phase by producing compressive forces on the top layer and changing the interlocking dispersion using the difference in coefficient of expansion between adjacent layers in the ceramic particles.

Research Methodology

With the advancement of nanomaterials and related fields, work on strong and tough ceramics has shifted from conventional quenching to new concept quenching. Graphene has emerged as the most potential reinforcement material for hardening ceramics, due to its small size, intrinsic 2D sheet composition, high abundance, and environmental friendliness.

In this study, researchers used graphene to design and develop complex designs spanning multiple sizes inside the ceramic phase using a bottom-up construction strategy. Multi-step curing methods have been established by combining components and layered structural approaches to achieve the best performance for advanced ceramic composites.

conclusion and perspectives

At different time and space scales, all of the suggested macro-micro-nano multi-stage hardening processes were successful in dispersing energy, transferring applied load and attenuating high local pressures, thereby increasing resistance to rupture without losing the rigidity of nanocomposites. To produce an improved ceramic nanocomposite, these findings focus on the importance of careful material design and selection to uncover the important processes leading to improved mechanical efficiency.

This study provides a suitable approach to develop tough ceramic materials for applications in optoelectronics, information technology, industrial production, navigation, healthcare, defense and space travel by successfully developing a combination of hardening methods ranging from nanoscale to macroscale.

Read on: The role of structural engineering in nanotechnology.

Reference

Sun, J. et al. (2021) Multi-step macro-micro-nano tempering in nano-laminated graphene ceramic composites. The physics of materials today. Available at: https://www.sciencedirect.com/science/article/abs/pii/S254252932100256X

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