HK Tech Forum on Advanced Matter and Materials

HK Tech Forum on Advanced Matter and Materials

Date & Time: 19 to 20 September 2022

Venue: Virtual

Website: https://www.cityu.edu.hk/hktechforum/cof-advanced-matter-materials-desc.htm

Registration here (https://cityu.zoom.us/webinar/register/WN_wu7WvktWT4a4T6pIah4w0A)

Objective

A two-day Forum on “Advanced Matter and Materials” is planned to focus on microelectronic packaging and mechanical behaviour of materials. In Day-1, the great potential in linking microelectronic devices to biomedical applications will be emphasized and explored, including the utilization of copper cloth with (111) uni-directionally oriented nano-twin copper as a new electronic packaging matter to inactivate Covid-19 virus rapidly. In Day-2, innovative approaches in alloy design to overcome the limitation of materials performances will be the focus. Eminent scholars from academia to industry will share their findings and explore ways on the development of advanced materials.

Featured Speaker

Ke Lu

Chinese Academy of Sciences, China

Professor Ke Lu (B. S. in materials science and engineering, Nanjing University of Science & Technology, 1985; PhD in MSE, Institute of metal Research of CAS, 1990) is a professor and the founding director of Shenyang National Laboratory for Materials Science (SYNL). He was a visiting professor in Max-Planck-Institut für Metallforschung (Stuttgart, Germany) and in University of Wisconsin-Madison (USA).

The Schwarz Crystal Structure: A Metastable Structure in Polycrystalline Metals with Extremely Fine Grains

The Schwarz Crystal Structure: A Metastable Structure in Polycrystalline Metals with Extremely Fine Grains

Metals usually exist in form of polycrystalline solids with crystalline grains separated by networks of grain boundaries (GBs) that are structurally disordered. The GBs are unstable and tend to get eliminated through grain coarsening upon heating or straining, or to transform into metastable amorphous states when the grains are extremely fine. This is why nano-grained metals have a much reduced stability relative to their coarse-grained counterparts, which is the major bottleneck limiting their processing and technological applications. Through experiments and MD simulations, we recently discovered a novel metastable state for extremely fine-grained metals (typically below 10 nm), namely Schwarz crystal structure. The GB-network of the metal is characterized by 3D minimal interfaces structure (with a zero-mean-curvature) constrained by twin boundaries. The unique structure is thermally stable against grain coarsening even close to the equilibrium melting point and exhibits a hardness in vicinity of the theoretical value. The across-boundary diffusion is so effectively suppressed that the diffusion-controlled processes such as intermetallic precipitation are inhibited. In this presentation, I will introduce the formation process, structure characteristics, and some properties of the Schwarz crystal structures in a number of pure metals and alloys.

References

1. X.Y. Li, Z.H. Jin, X. Zhou, K. Lu, Science, 370, 831-836 (2020).
2. W. Xu, B. Zhang, X.Y. Li, K. Lu, Science, 373, 683-687 (2021).
3. Z.H. Jin, X.Y. Li, K. Lu, PRL, 127, 136101 (2021).

Presented by: HK Tech Forum, Hong Kong Institute for Advanced Study, and Department of Materials Science and Engineering, City University of Hong Kong