H.M. Chen

Two-glassy-phase bulk metallic glass with remarkable plasticity

Using the computational-thermodynamic approach, the potential compositions of Zr–Cu–Ni–Al alloy system exhibiting the two-liquid miscibility phase equilibrium in the liquid temperature region have been identified. The resulting Zr base bulk metallic glasses show a microstructure of two microscaled glassy phases. The glass possesses a remarkable macroscopic plastic strain of 30% at room temperature. The gain of mechanical properties is attributed to the unique glassy structure correlated with the chemical inhomogeneity on the micron scale, the hard phases surrounded by the soft phases, leading extensive shear-band formation, interactions, and multiplication.

Flow serration and shear-band propagation in bulk metallic glasses

Flow serration in bulk metallic glasses (BMGs) was analyzed using high-sensitivity strain gauges. Based on the displacement-time profile for one serration, shear-band propagating speed was determined and found to be insensitive to the applied strain rates. The disappearance of serration at high strain rates is a result that the signal of displacement burst was overwhelmed by the applied strain rate. In comparison with the ductile Pd-based and brittle Mg-based BMGs, the ductility of BMGs appears to be closely related to the dynamics during shear-band propagation.

Molecular dynamics simulation of the dynamical behaviors of an aromatic carboxylic acid molecule with different conformations on a Au (111) surface

In this study, the behavior of a single tricarboxylic acid derivative, 1,3,5-tris(carboxymethoxy) benzene [TCMB, C6H3(OCH2COOH)3] on a Au (111) substrate at 50K has been investigated by molecular dynamics simulation. Four possible conformations of the TCMB molecule adsorbed on the Au (111) substrate are found and which display different trajectories of movement and dynamical behaviors. The lock-and-key geometry between the TCMB molecule of different conformations and atomic arrangement of the Au (111) surface was also observed.

Lock and key behaviours of an aromatic carboxylic acid molecule with differing conformations on an Au (111) surface

Tricarboxylic acid derivative with three-fold symmetry in physisorbed monolayers is an important organic molecule for applications in nanotechnology. In this paper, the behaviour of a single tricarboxylic acid derivative, 1,3,5-tris(carboxymethoxy)benzene (TCMB, C6H3(OCH2COOH)3) on an Au (111) substrate at 50 K is investigated by molecular dynamics simulation. Four possible conformations of the TCMB molecule adsorbed on the Au (111) substrate are found, the difference of which is the orientation of the CH2 chain. They also display different trajectories of movement and dynamical behaviours. As the molecule migrates across the Au (111) surface, the translational motion of TCMB is always accompanied by rotational motion. The lock-and-key (LAK) geometry between the TCMB molecule of different conformations and atomic arrangement of the Au (111) surface was also observed in this study, and the result has been verified by an ab initio calculation.