mohsenzaeem's blog

Open Access
A. Emdadi, J. Watts, W.G. Fahrenholtz, G.E. Hilmas, and M. Asle Zaeem. Predicting effective fracture toughness of ZrB2 based ultra-high temperature ceramics by phase-field modeling.  Materials & Design 192 (2020) 108713 (11 pages).

Thomas, M.S. Manju, K.M. Ajith, S.U. Lee and M. Asle Zaeem. Strain-induced work function in h-BN and BCN monolayers.  Physica E: Low-dimensional Systems andNanostructures 123 (2020) 114180 (9 pages).  

Abstract

C. Cissé and M. Asle Zaeem. A phase-field model for non-isothermal phase transformation and plasticity in polycrystalline yttria-stabilized tetragonal zirconia.  Acta Materialia 191 (2020) 111-123. 

S. Thomas, A. Kulangara Madam, and M. Asle Zaeem. Stone-Wales defect induced performance improvement of BC3 monolayer for high capacity lithium-ion rechargeable battery anode applications. The Journal of Physical Chemistry C (2020) (10 pages). 

N. Zhang and M. Asle Zaeem. Nanoscale flaw tolerance behaviour of polycrystalline tetragonal zirconia nanopillars. International Journal of Mechanical Sciences 173 (2020) 105405 (7 pages). 

A. Mahata, M. Asle Zaeem. Size effect in molecular dynamics simulation of nucleation process during solidification of pure metals: investigating modified embedded atom method interatomic potentials.

Directional solidification of Al-11 at % Cu is investigated by molecular dynamics (MD) simulations utilizing second nearest neighbor modified embedded atom method (2NN-MEAM) interatomic potential. The condition for directional solidification is produced by imposing dissimilar temperatures at the model boundaries along the [1 0 0] solidification direction to create a temperature gradient. During solidification, the solid-liquid front travels through the Al-Cu liquid along the [1 0 0] direction towards the high temperature end.

Shape memory ceramics, such as yttria-stabilized tetragonal zirconia (YSTZ), offer unique properties including ultra-high operating temperatures and high resistance to oxidation. However, they are susceptible to formation of defects during manufacturing and/or by mechanical deformation. To completely take advantage of their shape memory properties, it is necessary to fully understand the nano-structural evolution of defects under external stimuli. In this study, defect evolution behaviors in YSTZ nanopillars are investigated by atomistic simulations.

We studied the oxidation behavior of face-centered cubic Al0.3CoCrCuFeNi high entropy alloy through first-principles calculations. Three surface orientations were chosen for oxidation, and all the possible combinations of atomic positions at these surfaces were considered. The adsorption energy of oxygen adhesion to the studied surfaces was the lowest for the sites with more neighboring Cr atoms, and the second most favorite site for oxygen adsorption had more neighboring Al atoms.

Formation of solidification defects and their evolution in uniaxial tensile deformation of solidified polycrystalline aluminum (Al) were investigated by molecular dynamics (MD) simulations. First, solidification process was simulated both isothermally and with different quench rates. At the initial stages of nucleation, coherent twin boundaries and/or fivefold twins formed depending on the quench rate or the undercooling temperature.

A PostDoc/Research Assistant Professor Position is available immediately on DFT/Phase Field Modeling at the Colorado School of Mines. The applicants should have a PhD degree in Mechanical Engineering, Materials Science or in a relevant field, with a strong background in DFT calculations and phase-field modeling. The project involves simulating structures/phases, kinetics and nano/microstructural evolution in advanced manufacturing. Please send your CV with 2-3 of your recent and reverent publications to zaeem@mines.edu (Prof. Asle Zaeem).

Shape memory ceramics are a unique family of shape memory materials with a wide variety of applications, such as ultra-high energy dissipation and high-temperature actuation. Along with significant progress in the experimental study of zirconia-based shape memory ceramics in recent years, computational simulations have exhibited powerful capabilities in revealing nano/microstructure-dependent deformation and failure mechanisms in these materials.

N. Zhang, Y. Hong, S. Yazdanparast, and M. Asle Zaeem. Superior structural, elastic and electronic properties of 2D titanium nitride MXenes over carbide MXenes: A comprehensive first principles study. 2D Materials 5 (2018) 045004

Homogeneous nucleation from aluminum (Al) melt was investigated by million-atom molecular dynamics (MD) simulations utilizing the second nearest neighbor modified embedded atom method (MEAM) potentials. The natural spontaneous homogenous nucleation from the Al melt was produced without any influence of pressure, free surface effects and impurities. Initially isothermal crystal nucleation from undercooled melt was studied at different constant temperatures, and later superheated Al melt was quenched with different cooling rates.

The compressive mechanical responses of silicon nanoparticles with respect to crystallographic orientations are investigated by atomistic simulations. Superelastic and abrupt hardening-stiffening behaviors are revealed in [110]-, [111]- and [112]-oriented nanoparticles. The obtained hardness values of these particles are in good agreement with the experimental results. In particular, [111]-oriented particle is extremely hard since its hardness (∼33.7 GPa) is almost three times greater than that of the bulk silicon (∼12 GPa).

Mechanical properties of yttria-stabilized tetragonal zirconia (YSTZ) bicrystals under compressive loading are investigated by atomistic simulations. Previous studies on deformation of single-crystal YSTZ showed that some specific orientations promote dislocation emission, tetragonal to monoclinic phase transformation, or both. In this work, nanograins with different orientations are selectively combined to generate bicrystals with various grain boundaries (GBs).

Effects of Cu, Mn, Al, Ti, Mo on generalized stacking fault energies, Rice-criterion ductilities, and twinabilities of CoCrFeNi-based face-centered cubic high entropy alloys were investigated using density functional theory calculations. The calculated barrier energies and twinnabilities revealed that the addition of Ti or Mo increased the tendency of dislocation glide and deformation twinning, while addition of Mn, Cu and relatively high amount of Al facilitated dislocation gliding and martensitic transformation. Low amount of Al resulted in only dislocation gliding.

The nanoscale plastic deformation of yttria-stabilized tetragonal zirconia (YSTZ) is highly dependent on the crystallographic orientations, i.e., dislocation is induced when the loading direction is 45° tilted to {111} and {101} slip planes, while tetragonal to monoclinic phase transformation dominates the plastic deformation when loading direction is perpendicular to the slip planes.

Selection and thermal stability of phases are important in design of high entropy alloys (HEA). In this study, phase formations in cast AlFeCoNiCu HEA were investigated. Ab-initio molecular dynamics (AIMD) simulations were used to determine crystal structures of phases at different temperatures in equiatomic composition of AlFeCoNiCu. The AIMD results showed a possible coexistence of a face-centered cubic (fcc) phase and a bodycentered cubic (bcc) phase at the room temperature and indicated stabilization of a single fcc phase above 1070 K at the equiatomic composition of AlFeCoNiCu.