The manufacture of ductile ceramics is a difficult task. Plasticity in ceramics is rarely seen and usually requires special conditions such as temperature extremes to be achievable. Therefore, instead of denting, a typical ceramic coffee mug will shatter into pieces when dropped on a hard floor.
In his commentary, Dr. Erkka J. Frankberg, an expert in plasticity of ceramics, evaluates some of the latest findings regarding room temperature plasticity in ceramics reported by J. Zhang et al. in Science. In his commentary, Frankberg paints a larger picture of the potential benefits of these ductile ceramics, if they were to be made possible and scaled up for commercial use, perhaps ushering in a new Stone Age.
Why would it be important to develop ceramics that are ductile at room temperature? This is due to the atoms themselves and the bond between them. Ceramics have ionic and covalent bonds between atoms that differ significantly from bonds (for example) in metal alloys. A major difference is that ionic and covalent atomic bonds are among the strongest we know. As a result, in theory, ceramics should be among the strongest engineering materials available.
“The catch is that if the bonds are strong, they also prevent atoms from moving easily through the material, and this movement is necessary to create plasticity, or in other words, a permanent change in the perceived shape of the material. Without plasticity, unfortunately, ceramics fracture well below their theoretical strength and, in practice, often have a lower ultimate strength than many metal alloys commonly used in engineering,” says Frankberg.
To demonstrate the potential of ductile ceramics, Zhang et al. show that if silicon nitride (Si3NOT4), a ceramic material, is designed to exhibit plasticity, it can exhibit an enormous ultimate strength of around 11 GPa before fracture. It is about 10 times stronger than some common grades of high tensile steel.
What could ultra-resistant ductile ceramics bring us?
“Higher strength means less material needed to build moving machines such as vehicles and robots. Less material means lower inertia, which means lower energy consumption and higher efficiency for all machinery in motion. Greater resistance to wear and corrosion of ceramics would allow greater availability of these machinery applications, which enables economic benefits,” Frankberg points out.
Humanity has a constant need for ever stronger engineering materials, due to the significant cross-cutting impact they would have, improving the energy efficiency of society.
“Because of the softer bond, there is a hard limit to the strength of materials we can create from metals. To achieve the next level of strength, ceramic is a good candidate,” Frankberg says.
While the results of Zhang et al. are a spectacular demonstration of the potential of ductile ceramics, the results are demonstrated at the nanometer scale, like most similar results in the field. Therefore, a long and winding road remains to be traveled to realize the dream of flexible ceramics, which essentially requires that these results be repeated in a larger material.
“But every discovery of a new room-temperature plasticity mechanism, like the one presented by Zhang et al., keeps us in the dream of flexible ceramics,” Frankberg concludes.
New technique to improve the ductility of ceramic materials for missiles, engines
Erkka J. Frankberg, A ceramic that bends instead of breaking, Science (2022). DOI: 10.1126/science.ade7637. www.science.org/doi/10.1126/science.ade7637
Jie Zhang et al, Plastic deformation in silicon nitride ceramics via bond switching at coherent interfaces, Science (2022). DOI: 10.1126/science.abq7490
Provided by the University of Tampere
Quote: Assessing the Latest Findings Regarding Room Temperature Plasticity in Ceramics (2022, October 27) Retrieved October 27, 2022 from https://phys.org/news/2022-10-latest-room-temperature-plasticity-ceramics. html
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