New research by Danish and Chinese scientists could help revolutionize the way nanometals are understood and used in daily life.
The Danish-Chinese Center for Nanometals, founded in 2009, facilitates academic cooperation between Danish and Chinese scientists in the area of nanoscience and technology with a focus on metals.
It believes nanometals are an important research field with great potential benefit for individuals and society as it has many applications in industry.
"Research has shown that, when the interior structure of the metal is reduced to nanometer scale, not only can the properties of metals be improved but also completely new properties and behaviors may be achieved in these new materials," explained Dr. Grethe Winther, a key scientist and Danish coordinator at the center, in an interview with Xinhua.
All metals are composed of 'crystal grains' or regularly arranged structures of atoms. A metal is considered 'nanostructured' when the grain size within the metal is below a few hundredths of a nanometer, a unit measuring one millionth of a millimetre, or around 100,000 times thinner than a human hair. In an ordinary metal, the grain size is typically in the range of a few to hundreds of micrometers.
Moreover, nanometals respond in unexpected ways depending on how they are treated.
"Our common knowledge about metal is that it gets harder when it is deformed and on the other hand, it becomes softer by being heated up," Dr. Huang Xiaoxu, a senior scientist at the center, told Xinhua.
"However, we found that the nanostructured metals are softened by being deformed and hardened by annealing," he added.
Annealing refers to a heat treatment that changes the properties of a metal, such as its strength, hardness and ductility, by altering its microstructure.
When asked about the industrial implications of this discovery, Huang replied, "our findings and the suggested new strategy for optimizing the strength and ductility of nanostructured metals may be an inspiration in the application and development of industrial processes."
Indeed, nanomaterials are well known for their strength and resistance to wear and tear. This suggests applications in the automobile industry where car components made of nanometals would be lighter in comparison to conventional materials, thereby reducing the energy spent on transporting the weight of the vehicle.
However, to tailor nanometals for wide use in industrial applications, it is necessary to understand how the internal structures of nanometals affect their properties.
One particular challenge is that the size of metal grains can expand even at room temperature, as the boundaries between these grains can move. This could lead to a coarsening of the structure and consequently, a weakening of the nanometal.
"A doctoral student of our center, Tianbo Yu, who was a former student of Tsinghua University, has shown that the boundaries of the grains can be locked," Grethe said.
As such, Yu's research result has paved the way for car components to be made of nanometals.
The Danish-Chinese Center for Nanometals is a collaboration between China's Tsinghua and Chongqing universities, the Institute of Metals Research of the Chinese Academy of Science in Shenyang (IMRSYNL), and the Materials Research Division at Risoe Technical University of Denmark.
It is also supported by the Danish National Research Foundation and the Chinese Natural Science Foundation.
While cooperation between Danish and Chinese researchers involved at the Center began more than a decade ago, it has gathered pace since the Center was established.
"The center is a synergy of complementary scientific skills and equipment from both sides, and provides a solid and efficient platform which allows a closer and more productive cooperation between Danish and Chinese researchers," Huang said.
In the past two years, the center has held three international workshops in tandem with its Chinese partners, and published more than 20 original research papers in international academic journals, including three in Science, and one in Nature.
Recently, Huang and a research team at IMRSYNL have developed an x-ray method that can be used to look inside a given material and obtain a three-dimensional (3D) map of its crystal structure and of how it appears as it changes.
As such, the technique helps explore and understand the special properties of nanometals. Moreover, the resolution provided by this new technique is 100 times better than existing, non-destructive 3D techniques.
"Over the last several years, the potential of nanotechnology has been taken seriously by the public. (Normally) it would take 10 to 15 years to apply our research results in industrial use," Huang said.
"However, this research center has already created strong collaboration between Chinese and Danish scientists focusing on fundamental research in the field of nanoscience and technology with an emphasis on metals and has demonstrated its ability to compete globally," he added.