New technique to improve the ductility of ceramic materials in missiles and engines

Something as simple as an electric field could soon make war missiles or drinking cups easier to produce and more resistant to fractures.

Items such as drinking cups, missile heads, thermal barrier coatings on engine blades, auto parts, electronic and optical components are typically made of ceramic.

Ceramics are mechanically strong, but tend to break suddenly when they are lightly stressed under a load, unless exposed to high temperatures.

Researchers at Purdue University have developed a new process to overcome the fragility of ceramics and make it more ductile and durable. The Purdue team calls this process "flash sintering", which adds an electric field to the conventional sintering process used to form bulk components from ceramics.

"We have been able to show that even at room temperature, sintered ceramics with the electric field deform surprisingly plastically before fracturing when they are compressed to high stress," said Haiyan Wang, a professor of electrical engineering. Engineering at Basil S. Turner at Purdue's College of Engineering.

A study published in Progress of science demonstrates that the application of an electric field to ceramic formation makes the material almost as easily remodeled as the metal at room temperature. The Purdue team has specifically applied its technique to titanium dioxide, a widely used white pigment.

"Nanotwins have been introduced into various metal materials to improve strength and ductility.However, there are few previous studies showing that nanotwins and stacking defects can significantly improve the plasticity of the ceramic, "said Jin Li, postdoctoral researcher and research team researcher. .

The ductility at room temperature significantly increased in titanium dioxide is attributed to defects of unusually high density, such as stacking defects, twins and dislocations, formed by the process of flash sintering.

"The existence of these defects removes the need for nucleation of defects in ceramics, which typically requires significant nucleation stress, higher than the fracture stress of ceramics," Wang said.

Li, the first author of the Purdue article, said, "Our results are important as they open the door to the use of many new ceramics, offering more flexibility and durability to support heavy loads and high temperatures without catastrophic brittle failure. "

Improved plasticity for ceramics results in greater mechanical durability when operating at relatively low temperatures. The sample could also withstand almost as many compression stresses as some metals before cracks began to appear.

"These ductile ceramics are finding many technologically important applications," said Xinghang Zhang, professor of materials engineering and researcher co-leader within the research team. "It can be applied to defense operations, automotive construction, nuclear reactor components and sustainable energy devices."