Elastic strain engineering (ESE)means to tune the properties of a material by imposing an elastic strain on it. As “smaller is stronger” tells, nanostructured materials such as nanowires, thin films, atomic sheets etc. can sustain uch higher non-hydrostatic (tensile, compressive, or shear) stresses than their bulk counterpart, up to a significant fraction of its ideal strength without inelastic relaxation by plasticity or fracture. By varying the 6-dimensional elastic strain as continuous variables, he physical and chemical (e.g. electronic, optical, magnetic, thermal, mechanoelectrical, catalytic) properties of a material can be tailored in a large range. To achieve rational ESE, investigation is carried out in CAMP-Nano in the following directions.
Ø Elastic strain generation: It is the precondition for the success of ESE to apply elastic strain onto nanomaterial precisely, reversibly, and controllably. Therefore, efforts are made to develop MEMS-based elastic strain generators and electron microscope based elastic strain measurement techniques.
Ø Strain effect prediction: It will be time and energy efficient if one can predict the effects of elastic strains on the properties of a material, therefore various simulation approaches are employ for ESE study, from ab initio to continuum scale modeling.
Ø Strain effect measurement: To prove and improve thetheory and modeling of ESE, it is essential to study experimentally the property evolution as a function of elastic strain. Due to the characteristics of elastic strain (dynamical and reversible), in situ multi-field (mechano-thermo-electrical for example) measurement techniques are being developed.
Ø Elastic strain relaxation: To understand the limit and reliability of ESE, it is necessary to answer the following question: at what level and for how long time the elastic strain applied on nanomaterials will be relaxed. Consequently the mechanism of plastic deformation and defect evolution need to be investigated.
References:
H. Guo, K. Chen, Y. Oh, K. Wang, C. Dejoie, S.A. Syed Asif, O.L. Warren, Z.W. Shan, J. Wu & A.M. Minor, Mechanics and dynamics of the strain-induced M1-M2 structural phase transition in individual VO2 nanowires. Nano Letters 11, 3207-3213, (2011).
L. Tian, J. Li, J. Sun, E. Ma & Z.W. Shan, Approaching the ideal elastic limit of metallic glasses. Nature Communications3, 609, (2012).
Z.W. Shan, In Situ TEM Investigation of the Mechanical Behavior of Micronanoscaled Metal Pillars. JOM 64, 1229-1234 (2012).
L. Tian, J. Li, J. Sun, E. Ma & Z.W. Shan, Visualizing size-dependent deformation mechanism transition in Sn. Scientific Reports 3, 2113, (2013).
C.C. Wang, Y.W. Mao, Z.W. Shan, M. Dao, J. Li, J. Sun, E. Ma & S. Suresh, Real-time, high-resolution study of nanocrystallization and fatigue cracking in a cyclically strained metallic glass. Proceedings of the National Academy of Sciences of the United States of America 110, 19725-19730, (2013).
J. Li, Z.W. Shan & E. Ma, Elastic strain engineering for unprecedented materials properties. MRS Bulletin39, 108-114, (2014).
