Chinese scientists have managed to create a strong, flexible ceramic
Chinese researchers have created the first ceramic substance in the world that can flex like metal. This development, if true, could improve artificial joints and engine performance.
Before this discovery, it was commonly believed that a ceramic's flexibility and strength were opposites and that either would worsen if the other improved.
Chen Kexin, a materials scientist who led the research, says that the new material is the first time scientists have made both stronger and lighter at the same time. It has the hardness of ceramic and the flexibility of metal.
“This ceramic can bring technological revolutions to many industries,” said Chen, a professor at the department of engineering and material sciences at the National Natural Science Foundation of China.
On October 27, Chen and associates from Tsinghua University published their findings in the journal Science. In an opinion piece in the same issue of Science, Erkka Frankberg of Tampere University in Finland said that the discovery "could lead to materials that are lighter and stronger than even the best metal alloys of today."
“There has been research on plasticity of ceramics around the world since I started my career 30 years ago. It can be said that today we have finally achieved a breakthrough on that topic,” Chen said.
The new ceramic uses nanotechnology to make it flexible
The scientists created nanopillars with two different crystal formations using silicon nitride. When an outside force is put on one crystal structure, it can change into another type. This lets the material bend before going back to its original shape.
The substance may be particularly advantageous for creating aeronautical engines. Ceramic materials are durable, lightweight, and heat-tolerant. Flexible ceramic engines might function at significantly greater temperatures and with far better fuel efficiency than typical alloy engines.
A ceramic engine could move much faster than an alloy engine because it would be much lighter. Stress on other components is reduced by lightening the engine.
The substance might also be applied to car engines. A ceramic engine might have a smaller coolant tank due to ceramic materials' superior heat resistance to alloys. A ceramic engine's higher combustion temperatures might produce more thrust and less pollution.
Ceramics made of silicon nitride can replace metal in joint replacements because they are biocompatible, light, and resistant to bacteria. Most prosthetic joints made of metal have to be replaced every ten years, which is expensive and painful.
“Artificial joints made with ceramics can last a lifetime after implantation,” Chen explained.
Chen also said that the material could be used to make bearings, an essential part of wind turbines connecting the generator to the fan blades. The durability of each bearing, which must sustain several tons of pressure while in use, affects the system's overall service life.
"Our flexible silicon nitride ceramics could be used to make bearings that last longer, which would lower the cost of wind power on average," Chen explains.
“It is possible to produce this flexible ceramic material on a large scale based on our experiments. There is an obvious price advantage in the field of high-end equipment,” he added.
He gave the example of the expensive rare earth minerals used to make the single-crystal turbine blades used in jet engines. At the same time, the most expensive silicon nitride sells for roughly $200 per kilogram.
“We will keep improving this ceramic material on the basis of our current work. Once you open a door, there is a broad world behind,” Chen said.
You can view the study for yourself in the journal Science.
"Covalently bonded ceramics exhibit preeminent properties—including hardness, strength, chemical inertness, and resistance against heat and corrosion—yet their wider application is challenging because of their room-temperature brittleness. In contrast to the atoms in metals that can slide along slip planes to accommodate strains, the atoms in covalently bonded ceramics require bond breaking because of the strong and directional characteristics of covalent bonds. This eventually leads to catastrophic failure on loading. We present an approach for designing deformable covalently bonded silicon nitride (Si3N4) ceramics that feature a dual-phase structure with coherent interfaces. Successive bond switching is realized at the coherent interfaces, which facilitates a stress-induced phase transformation and, eventually, generates plastic deformability."
Professor Gretchen Benedix is an astrogeologist and cosmic mineralogist who studies meteorites and figures the forming stages of the solar system.