msepostdoc-list Seminar Reminder for Kiettipong Banlusan's Ph.D. Final, Friday, July 14, at 2:00 p.m., in ARMS 1028. " Relaxation Mechanisms Under Dynamical Loading of Metal-Organic Frameworks"

[Son, Rosemary E]

Please consider attending the following:


MATERIALS ENGINEERING
SEMINAR


"Relaxation Mechanisms under Dynamical Loading of Metal-Organic Frameworks"


By
Kiettipong Banlusan
Purdue MSE Ph.D. Final Exam

Advisor: Professor Alejandro Strachan


ABSTRACT

Metal-organic frameworks (MOFs) are a class of nano-porous crystalline solids consisting of inorganic units coordinated to the organic linkers. The unique molecular structures with ultra-high porosity, outstanding properties, and tunable chemical functionality by various choices of metal clusters and organic ligands make this class of materials attractive for many applications. The possible collapse of the large free volume fraction makes MOFs appealing for the applications that require dissipating mechanical energy, e.g. shock-wave energy dissipation. However, the deformation mechanisms beyond elastic regime and the dynamical effects of MOFs have not been well understood yet. Under shock compression materials can undergo various deformation processes including elastic deformation, plastic deformation, phase transition, and structural decomposition. Thus, understanding of mechanical properties is the key first step towards the shock wave investigation. We use density functional theory (DFT) to calculate the elastic stiffness coefficients of various types of MOFs to establish relationships between the structure and their elastic properties including anisotropy and temperature dependences. The mechanical properties of MOFs beyond elastic regime have been investigated using large-scale molecular dynamics (MD) simulations in order to capture the nucleation and propagation of plastic deformation under quasi-static compression. We use MD simulations with reactive ReaxFF force field that enables us to capture the chemical processes to study the dynamical effects of MOFs under shock loading. We find that MOFs exhibit two-wave structure with elastic precursor followed by the second wave corresponding to structural transition. A combined experimental and computational study shows that shock-wave energy flux generated from the impact of a flyer plate is attenuated via large volume collapse of MOFs structure, and the lower energy (~50%) is transmitted to the object in front of the wave. Finally, the simulations with reactive ReaxFF force field show that MOF undergoes chemical decomposition into small molecules with higher energy. This is an indication of possible endothermic chemical reaction, which could also absorb the shock-wave energy.



Date: Friday, July 14, 2017

Time: 2:00 P.M.
Place: ARMS 1028

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