Seminar & Colloquium
[세미나: 9월 4일(수), 오후 2시] Prof. Tanguy Rouxel, University of Rennes
Title
What we can learn from the mechanical behavior of glasses about their atomic and molecular structures
Speaker
Prof. Tanguy Rouxel, Glass and Mechanics Department, Physics Institute, University of Rennes
* Biography
Prof. Rouxel is a Mechanical Engineer (ENSAM, Paris), a Doctor in Ceramic Science (ENSCI, Limoges) and full Professor of Glass Science and Solid Mechanics at the University of Rennes 1. After obtaining an engineering diploma from the Ecole Nationale Supérieure d’Arts et Métiers, Rouxel gained his Bachelor of Science degree (French DEA) from the University of Paris XIII, and his Ph.D (French Doctorate) from the University of Limoges.
After graduating he became a post-doctoral Fellow in the Government Industrial Research Institute of Nagoya (then the NIRIN, Japan) for one year and a half. He then held a position as a CNRS Researcher in Ceramics Science for four years, during which he spent several periods of study leave in the department of Materials Science at the University of Tokyo. In 1997, he was appointed Professor at the University of Rennes, where he founded a laboratory (LARMAUR) devoted to the study of surface mechanics problems, and flow and fracture in advanced glasses and ceramics. He is the author of approximately 150 papers in scientific journals, four patents, and five book chapters. He is also an associate editor of the Journal of the American Ceramic Society.
| Date | Wednesday, September 4th, 2024
| Time | 14:00 ~
| Venue | 33동 125호(WCU 다목적실)
[Abstract]
The mechanical properties of glasses from different chemical systems were studied in the light of the atomic packing density (Cg), medium range order and atomic bonding character. The elastic moduli reflect the volume density of energy, and are thus directly correlated to Cg and to the bond strength. Nevertheless, the packing density has actually the greater influence on the final result. The same conclusion is drawn for hardness. As a matter of fact, the hardest and stiffest glasses are not those with the strongest interatomic bonding! In the case of metallic glasses, we found that the electronegativity mismatch between the host- and the major solute - elements provides a plausible explanation to the large variation observed for Poisson's ratio (ν) notwithstanding a similar Cg. This correlation also holds for monoconstituent oxide glasses and hence provides an explanation to the variation of ν observed for seemingly "isostructural" glasses. In the search for more ductile glasses, the bond directionality and the sensitivity to volume change are key parameters. The energy required for a stable crack propagation through the system, where the crack tends to follow the easy paths, provides some insight into the energy landscape, with a remarkable consistency between the energy as calculated from the bond density and from self-consistent fracture toughness measurements. The presence of weak channels favoring shear flow can also be invoked to interpret the temperature sensitivity of the viscous flow (fragile versus strong liquids). Finally, the problem of crack initiation from a sharp contact loading is also discussed with respect of the possible deformation mechanisms, which are further correlated with the atomic organization.
[1] T. Rouxel, “Elastic properties and short-to-medium range order in glasses”, J. Am. Ceram. Soc., 90 [10] 3019-3039 (2007).
[2] G.N. Greaves, A.L. Greer, R. S. Lakes, and T. Rouxel, "Poisson’s Ratio and Modern Materials", Nat. Mat., 10 823-837 (2011).
[3] T. Rouxel, "Driving force for indentation cracking in glass: composition, pressure and temperature dependence", Phil. Trans. R. Soc. A, 373 20140140 (2015).
[4] T. Rouxel and Y. Yokoyama, "Elastic properties and atomic bonding character in metallic glasses", J. App. Phys., 118 044901 (2015).
[5] T. Rouxel and S. Yoshida, "The fracture toughness of inorganic glasses", J. Am. Ceram. Soc., 1 1-23 (2017).
[6] T. Rouxel, “Some strange things about the mechanical properties of glass”, Compte-Rendus de l’Académie des Sciences, Physique, 24 (S1) 1-14 (2023).
| Host | 최인석 교수(02-880-1712)