Technological Sciences
Yongjun Tian

Synthesis of artificial materials harder than natural diamond

Abstract:Understanding and approaching to the limits of materials properties are important subjects of materials science. Natural diamond has been considered as the hardest material in nature since its discovery more than 6000 years ago. Searching artificial materials harder than natural diamond has been a pursued goal of human beings. This is truly a challenge in materials science, and many researchers have argued that it is impossible to achieve this goal. Tian and his colleagues have systematically investigated the hardening mechanisms of covalent materials and established a hardening model of polycrystalline covalent materials. They found that polycrystalline covalent materials can be continually hardened with the microstructural characteristic size down to nanoscale, which designates a brand-new direction to greatly enhance the hardness of covalent materials. Based on this model, they proposed a novel idea to significantly enhance the performance of superhard materials diamond and cubic boron nitride (cBN) through forming ultrathin nanotwinned microstructures. They synthesized nanotwinned diamond and cBN from onion-structured carbon and boron nitride precursors, respectively, via direct phase transformations under high pressure and high temperature. Nanotwinned microstructure simultaneously improves the hardness, toughness and thermal stability of both materials. Hardness and toughness of nanotwinned diamond are twice as high as those of natural diamond, which is a great promotion to the research of high performance superhard materials and may produce technological innovations in processing industry and high pressure science.

Awardee:Yongjun Tian, Professor of College of Materials Science and Engineering, Yanshan University. He was born in 1963, received his Ph.D. from Institute of Physics, Chinese Academy of Science in 1994. He worked in Friedrich-Schiller-Universit?t Jena, Germany from 1996 to 1998 as an Alexander von Humboldt Research Fellow. In 2001, he was appointed as a Cheung Kong Scholar Professor by Chinese Ministry of Education. Tian was elected as an academician of Chinese Academy of Sciences in 2017. From 1999 to 2015, he was the dean of College of Materials Science and Engineering, Yanshan University. He serves as Associate Editor of Science China Materials, and Editorial Board Members of Journal of Materials Science & Technology and Journal of Materiomics. Prof. Tian’s laboratory focuses on the design and synthesis of novel metastable materials, and made significant contributions on superhard materials research. He published more than 290 papers in peer-reviewed journals including Nature, Physical Review Letters, Journal of American Chemical Society, etc. He was awarded the National Outstanding Young Scientist Fund (2003-2007) and Foundation for Innovative Research Groups (2009-2017) from the National Natural Science Foundation of China. He has been the recipient of several awards for his work including National Natural Science Award of China (Second Prize, 2011) and Natural Science Awards of Chinese Ministry of Education (First Prize, 2000 and 2008). His research works were selected into Top Ten Advances in Chinese Science (2013 and 2014) and Ten Grand Progress on Science and Technology of Chinese Universities (2013 and 2014).