The 292nd MANA & the 127th ICYS Joint Seminar
Dr. Dai-Ming Tang & Dr. Cesar Moreno
| Date | October 19, Friday |
| Time | 15:30-16:30 |
| Place | Auditorium, 1F, WPI - MANA Bldg., NAMIKI Site, NIMS |
Download PDF file for seminar info.
15:30-16:00
Mechanical Properties of 1-D Materials by In Situ Transmission Electron Microscopy
One dimensional (1-D) materials, such as carbon nanotubes, silicon nanowires and many others, are the potential building blocks for future nanodevices. Due to the strong dependence of mechanical properties on the length scale, it is crucial to clarify the nanomechanics of single nanostructures. Among various techniques in situ transmission electron microscopy (TEM) is a unique method which provides direct correlation between the structure and properties with atomic resolution.
In our recent studies, it was demonstrated that besides the well-known size effects, the connection geometry, inter-wall interactions and external loading conditions have important influences on the deformation mechanisms and fracture strengths of the 1-D materials. For example, the forces withstood by WS2 nanotubes were enhanced up to ~6000 nN because of the strong inter-layer interactions.1 And bamboo shaped boron nitride nanotubes composed of short nanotube-segments showed high tensile fracture strength and Young's modulus up to 8.0 and 225 GPa, respectively, due to the interlocked joint interfacial structures and compressive interfacial stresses, and corresponding switch of deformation mechanism from an interplanar sliding mode to an in-plane tensile elongation mode.2 In another example, it was revealed that the mechanical behaviors of Si NWs had closely been related to the wire diameter, loading conditions and stress states. Under tension, Si NWs deformed elastically until abrupt brittle fracture with the highest strength up to 11.3 GPa, while under bending they demonstrated considerable plasticity.3
References
- Tang, D.-M.; Wei, X.; Kawamoto, N.; Nethravathi, C.; Bando, Y.; Mitome, M.; Tenne, R.; Golberg, D., Mechanical properties of WS2 nanotubes by in situ TEM. 2012. In preparation.
- Tang, D. M.; Ren, C. L.; Wei, X. L.; Wang, M. S.; Liu, C.; Bando, Y.; Golberg, D., Mechanical Properties of Bamboo-like Boron Nitride Nanotubes by In Situ TEM and MD Simulations: Strengthening Effect of Interlocked Joint Interfaces. ACS Nano 2011, 5 (9), 7362-7368.
- Tang, D.-M.; Ren, C.-L.; Wang, M.-S.; Wei, X.; Kawamoto, N.; Liu, C.; Bando, Y.; Mitome, M.; Fukata, N.; Golberg, D., Mechanical Properties of Si Nanowires as Revealed by in Situ Transmission Electron Microscopy and Molecular Dynamics Simulations. Nano Lett. 2012, 12 (4), 1898-1904.
Speaker
Dr. Dai-Ming Tang, ICYS-MANA Researcher, NIMS
Chair
Dr. Kenjiro Miyano, NIMS Invited Researcher, Fellows,, NIMS
16:00-16:30
Towards a tunable superconductivity transition in small molecule organic compounds by combined scanning probe microscopies
Organic superconductors are presented as cost-effective and large-area scalable superconductor materials. This kind of superconductors has recently gained greater appeal than their ceramic and metallic counterparts due to their fine-tailoring of electrical and structural properties, and because they offer a simple system to advance the fundamental understanding of superconductivity.
The recent opportunities provided by the simultaneous combination of STM and AFM to manipulate atoms and molecules and to simultaneously characterize their electronic structural and charge states opens new ways to explore classical concepts still not yet well understood at the nanoscale. To that effect, local manipulation of molecules or atoms may enable new methods to discriminate which parameters govern the superconductivity transition and creates new opportunities to control critical temperature in organic superconductors in an attempt to reach higher critical temperatures.
In this talk, I will describe an approach to characterize and manipulate electronic, chemical and structural properties at molecular and atomic scale of small molecule organic superconductors. .
Speaker
Dr. Cesar Moreno, ICYS-Sengen Researchder, NIMS
Chair
Dr. Oscar Custance, Group Leader, Atomic Force Probe Group, Nano Characterization Unit, Advanced Key Technologies Division NIMS