NANOscientific

Dr. Xiaming Chen received his B.S. and M.S. degree in Mechanical Manufacturing and Automation from Xi’an Jiaotong University in China, and Ph.D. degree in Mechanical Engineering from State University of New York. Dr. Chen’s research focuses on investigating the mechanical properties of carbon and boron nitride nanotubes and their polymer nanocomposites, part of a broad effort to develop next-generation, light-weight and high-strength multifunctional engineering materials, particularly for aerospace applications. In collaboration with NASA and the National Institute of Aerospace, and financially supported by the Air Force Office of Scientific Research, he tackles very challenging problems and has made several breakthroughs using state-of-the-art nanomechanical testing techniques. His research findings help to better understand the mechanical strength of nanotube structures and the local stress transfer on the nanotube-polymer interfaces, both critical for design and optimization of innovative nanotube-based material systems. He has published nineteen articles and has two book chapters to his credit. He has made morethan 20 conference presentations and holds one patent. Dr. Xiaoming Chen received several awards and honors from State University of New York at Binghamton, National Science Foundation and American Society of Mechanical Engineers.

Here we present an in situ electron microscopy nanomechanical study of t nanotubepolymer interfaces between individual CNTs/BNNTs and polymers in conjunction with atomistic simulations. By pulling out individual nanotubes from polymer films inside a high resolution electron microscope, the nanomechanical measurements capture the shear lag effect on nanotube–polymer interfaces. Our nanomechanical measurements reveal that BNNTs can form much stronger binding interfaces with polymers than comparable CNTs and that the interfacial strength of BNNT-epoxy interfaces is higher than that of BNNT-PMMA interfaces. The observed superior load transfer capacity of BNNT-polymer interfaces is ascribed to both the polarized nature of B-N bonds and the high bonding potentials of B and N atoms, which are supported by molecular dynamics (MD) simulations. The findings contribute to a better understanding of the local load transfer on the tube–polymer interface and the tube’s reinforcing mechanism. In addition, the extraordinary load transfer capacity of BNNT-polymer interfaces suggests that BNNTs are excellent reinforcing nanofiller materials for light-weight and highstrength polymer nanocomposites.

1.  How do you think your research will impact society in a positive way?

The researchobjective of this project is to investigate the mechanical properties of carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) and their polymer composites by using multi-scale experimental approaches. This study will focus on the quantitative experimental characterization of (1) mechanical properties of CNTs and BNNTs in three structural forms (i.e. individual tubes, thin-bundles and yarns) and the interfacial binding strength of the respective tube-tube interactions; and (2) mechanical properties of CNT and BNNT-based polymer composites and the interfacial shear strength of the respective tube-polymer interfaces. Our proposed nanotube-reinforced polymer composite study will employ epoxy and polyimide as matrix materials because they are widely used for structural applications in aerospace industries. The elastic moduli and yield strengths of CNT and BNNT nanostructures and the respective tube-tube and tube-polymer interfacial strengths will be characterized by using the state of the art in-situscanning electron microscopy (SEM) and atomic force microscopy (AFM) mechanical characterization techniques. Both of our proposed nanoscale experimental techniques uniquely enable the high-resolution concurrent measurements of the applied load and the mechanical response of the nanostructure under a variety of testing conditions (e.g. tensile, peeling and pull-out tests). The mechanical properties of CNT and BNNT-based yarns and thin-film polymer composite will be characterized by using micro/meso-scale tensile testing techniques. Using our multi-scale experimental platforms, we will systematically investigate the effects of harsh environments (e.g. high temperature and strong radiation) on the tube-tube interfacial strength and mechanical properties of CNTs and BNNTs, and the effect of the surface functionalization on the tube-polymer interfacial stress transfer and mechanical properties of CNT and BNNT-reinforced polymer composites. The impact of this project includes significant advances of the nanoscale mechanical characterization technique and our knowledge of the mechanical properties of CNTs and BNNTs in various structural forms and the interfacial strength of the respective tube-tube and tube-polymer interactions. This study will provide critical insights into the role of the interfacial interaction in the mechanical properties of CNTs and BNNTs and their polymer composites, and will directly contribute to the optimal design, modeling and manufacturing of novel multi-material and multi-functional light-weight highstrength materials systems, which are critically demanded for manyaerospace and automobile industriesapplications.

2.  What is the best or most useful part of using Park AFM for your research?

As a leading provider of atomic force microscopy, Park systems provides powerful functions and tools for nanoscale research and engineering. The most useful part of Park system in my research is Lateral Force Microscopy (LFM), which not only provides accurate topographic measurements, but also gives the surface frictional information of our nanoscale research samples. When the AFM cantilever scan the sample, the cantilever can move even cut the sample with specific normal load and scanning velocity, meanwhile the morphology and lateral force will be recorded. By using LFM, we already successfully investigate the dynamic and frictional properties of carbon nanotubes, boron nitride nanotube, graphene and boron nitride nanosheets.