September 24, 2019
In a flash: New technique to improve ductility of ceramic materials for missiles, engines, drinking mugs
WEST LAFAYETTE, Ind. – Something as simple as an electric field could soon make wartime missiles or drinking mugs easier to produce and more resilient for fracture.
Items such as drinking mugs, missile heads, thermal barrier coatings on engine blades, auto parts, electronic and optic components are commonly made with ceramics. The ceramics are mechanically strong, but tend to fracture suddenly when just slightly strained under a load unless exposed to high temperatures.
Purdue University researchers have developed a new process to help overcome the brittle nature of ceramics and make it more ductile and durable. The Purdue team calls the 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 temperatures, ceramics sintered with the electric field surprisingly deform plastically before fracture when compressed at high strain,” said Haiyan Wang, the Basil S. Turner Professor of Engineering in Purdue’s College of Engineering.
A study published in Science Advances demonstrates that applying an electric field to the formation of ceramics makes the material almost as easily reshaped as metal at room temperature. The Purdue team specifically applied its technique to titanium dioxide, a widely used white pigment.
“Nanotwins have been introduced in various metallic materials to improve strength and ductility. However, there are little prior studies that show nanotwins and stacking faults can significantly improve the plasticity of ceramics,” said Jin Li, a postdoctoral fellow and researcher on the research team.
The significantly enhanced room temperature ductility in titanium dioxide is attributed to the unusually high-density defects, such as stacking faults, twins and dislocations, formed through the flash sintering process.“The existence of these defects remove the need for defect nucleation in ceramics, which typically requires a large nucleation stress, greater than the fracture stress of ceramics,” Wang said.
Li, the first author of the article from Purdue, said, “Our results are important because they open the door for using many different ceramics in new ways that can provide more flexibility and durability to sustain heavy loads and high temperatures without catastrophic brittle failure.”
Improved plasticity for ceramics means more mechanical durability during operation at relatively low temperatures. The sample also could withstand almost as much compression strain as some metals do before cracks started to appear.
“These ductile ceramics find many technologically important applications,” said Xinghang Zhang, professor of materials engineering and co-principle investigator on the research team. “It can be applied to defense operations, automobile manufacturing, nuclear reactor components and sustainable energy devices.”
This Purdue-led research is supported by the Office of Naval Research in collaboration with the University of California, Davis, Rutgers University and Naval Research Laboratory.
Their work aligns with Purdue's Giant Leaps celebration of the global advancements in sustainability as part of Purdue’s 150th anniversary. Sustainability is one of the four themes of the yearlong celebration’s Ideas Festival, designed to showcase Purdue as an intellectual center solving real-world issues.
The research team is working with the Purdue Research Foundation Office of Technology Commercialization to patent their work. They are looking for partners for continued research. For more information on licensing and other opportunities, contact D.H.R. Sarma from OTC at firstname.lastname@example.org.
About Purdue Research Foundation Office of Technology Commercialization
The Purdue Research Foundation Office of Technology Commercialization operates one of the most comprehensive technology transfer programs among leading research universities in the U.S. Services provided by this office support the economic development initiatives of Purdue University and benefit the university's academic activities through commercializing, licensing and protecting Purdue intellectual property. For more information on licensing a Purdue innovation, contact the Office of Technology Commercialization at email@example.com. For more information about funding and investment opportunities in startups based on a Purdue innovation, contact the Purdue Foundry at firstname.lastname@example.org.The Purdue Research Foundation is a private, nonprofit foundation created to advance the mission of Purdue University.
Xinghang Zhang, email@example.com
Nanoscale stacking fault–assisted room temperature plasticity in flash-sintered TiO2
Jin Li, Jaehun Cho, Jie Ding, Harry Charalambous, Sichuang Xue, Han Wang, Xin Li Phuah, Jie Jian, Xuejing Wang, Colin Ophus, Thomas Tsakalakos, R. Edwin García, Amiya K. Mukherjee, Noam Bernstein, C. Stephen Hellberg, Haiyan Wang and Xinghang Zhang
Ceramic materials have been widely used for structural applications. However, most ceramics have rather limited plasticity at low temperatures and fracture well before the onset of plastic yielding. The brittle nature of ceramics arises from the lack of dislocation activity and the need for high stress to nucleate dislocations. Here, we have investigated the deformability of TiO2 prepared by a flash-sintering technique. Our in situ studies show that the flash-sintered TiO2 can be compressed to ~10% strain under room temperature without noticeable crack formation. The room temperature plasticity in flash-sintered TiO2 is attributed to the formation of nanoscale stacking faults and nanotwins, which may be assisted by the high-density preexisting defects and oxygen vacancies introduced by the flash-sintering process. Distinct deformation behaviors have been observed in flash-sintered TiO2 deformed at different testing temperatures, ranging from room temperature to 600°C. Potential mechanisms that may render ductile ceramic materials are discussed.