Logo

Amorphous Diamond: From Conjecture to Reality

Speaker

Qiaoshi(Charles) Zeng, Center for High Pressure Science & Technology Advanced Research

Time

2017.10.09 14:00-15:00

Venue

601, Pao Yue-Kong Library

Abstract

Diamond, as an important Carbon allotrope, is well known for its unparalleled properties such as the highest hardness, highest thermal conductivity among all materials. These properties are originated from the extremely strong sp3 bonding between carbon atoms. Actually, in the Group-14 elements, Carbon, Silicon and Germanium all have sp3-bonded crystalline phases with the same diamond-cubic structure. Silicon and Germanium both also have well-known sp3-bonded tetrahedral amorphous forms which have widespread applications. However, the counterpart in Carbon, an amorphous form of diamond, was conspicuously missing and remained a puzzle. Therefore, the search for the same sp3-bonded tetrahedral amorphous carbon which would have properties complementary to diamond has been a long-sought after yet elusive goal.

By combining high pressure with in situ laser heating at an unexplored specific pressure-temperature regime (~50 GPa and ~1800 K), we successfully synthesized a completely sp3-bonded tetrahedral amorphous carbon, i.e., “amorphous diamond”, for the first time. Moreover, this amorphous diamond obtained under high pressure can be recovered to ambient conditions. We preformed comprehensive studies including x-ray diffraction, high-resolution transmission electron microscopy, electron energy-loss spectroscopy experiments and ab initio molecular dynamics simulations on the amorphous diamond. The results suggest that the amorphous diamond has a three dimensional sp3-bonded network structure similar to crystalline diamond, but lacking long-range periodic order. Therefore, our study finds this missing member of the carbon allotrope family. Moreover, in our in situ high pressure x-ray diffraction experiment, this amorphous diamond showed ultrahigh incompressibility (bulk modulus) comparable to diamond. More follow-up studies on the mechanical, thermal, optical, electrical, and chemical properties of amorphous diamond are being explored.

Bio

Dr. Qiaoshi(Charles) Zeng currently is a “National Youth 1000 Talents” staff scientist at “Center for High Pressure Science & Technology Advanced Research” (HPSTAR). His research interest is mainly focused on the amorphous materials, especially the structure and properties of amorphous materials, and new materials synthesis. He has extensive experience in developing and utilizing various amorphous materials dedicated in situ high pressure and/or high temperature techniques including synchrotron radiation x-ray diffraction, imaging and spectroscopy etc. Dr. Zeng has published 43 papers in international journals (3 in Science, 3 in PNAS, 4 in PRL, 3 in Nature Communications). In addition, Dr. Zeng has been serving as a referee for many prestigious journals, such as PRL, JACS, Nano Lett., Nature communications, etc.

Dr. Zeng earned his B.S. in Materials Science and Engineering at Zhejiang University in 2005, and his Ph.D. in Materials Science and Engineering at Zhejiang University in 2010. After his postdoctoral research at Stanford Univeristy, in 2014 he became a research scientist at Carnegie Institution of Washington. Then, he joined HPSTAR in 2015. He is the recipient of a number of honors including the National Science and Technology Innovation Award for Youth in China in 2009, and the National Excellent Doctoral Dissertation Award in China in 2012.