Modeling of Formation of Nanostructured Metal Surfaces by Electrodeposition through a Monolayer Colloidal Crystal Mask

AbstractElectrochemical deposition is a feasible and well-controlled method for the formation of various micro- and nanostructures. A rich variety of periodical nanostructures of functional materials with multi-shaped and tunable morphologies can be fabricated by the electrochemical deposition, in particular, using monolayer colloidal crystal (MCC) mask. A mathematical model of the mass-transfer processes and deposit surface evolution during the metal electrodeposition through MCC mask is presented. The mathematical model involves the equations for the potential and deposit surface evolution. The problem was solved numerically by the boundary element method, and the “Level Set” method. The numerical experiments were used to study the effect of parameters, which characterize the mask geometry and the process conditions, on the initial distribution of current density over the deposit surface and the variation of current density distribution in the course of the deposition

Effect of Current Efficiency on Electrochemical Micromachining by Moving Electrode

AbstractIn this work, the effect of current efficiency on the electrochemical micromachining by moving electrode is studied theoretically. The Laplace equation for the electric potential and the equation of workpiece surface evolution are used as the mathematical model of the process. A new scheme of solution of free boundary problem for steady-state electrochemical micromachining is proposed. According to the scheme, the initial approximation of the workpiece surface is prescribed. In the course of modeling, the workpiece surface moves in the normal direction at a rate proportional to the discrepancy of the steady-state condition. The effect of various dependences of current efficiency on the local current density is analyzed. As a result of simulation, the dependences of the shape and sizes of machined surface on the current efficiency and the machining parameters are obtained

Computer simulations of the heat-resistant polyimides ULTEM and EXTEM using Gromos53a6 and Amber99 force fields

An atomistic computer simulation was performed for the polyimides ULTEM™ and EXTEM™ via the molecular-dynamics method with the use of Gromos53a6 and Amber99 force fields. For parameterization of electrostatic interactions, the partial atomic charges were calculated through quantum-chemical methods. The temperature dependence of density and the thermal-expansion coefficients for the polyimides were obtained. The calculated density values of the polyimides at room temperature and their coefficients of thermal expansion in the glassy state are in agreement with available experimental data. It is shown that inclusion of electrostatic interactions is necessary for simulation of the thermophysical characteristics of the considered polyimides

Molecular dynamics simulation of poly(3-hexylthiophene) helical structure in vacuo and in amorphous polymer surrounding

The stability of poly(3-hexylthiophene) (P3HT) helical structure has been investigated in vacuo and in amorphous polymer surrounding via molecular dynamics-based simulations at temperatures below and above the P3HT melting point. The results show that the helical chain remains stable at room temperature both in vacuo and in amorphous surrounding, and promptly loses its structure at elevated temperatures. However, the amorphous surrounding inhibits the destruction of the helix at higher temperatures. In addition, it is shown that the electrostatic interactions do not significantly affect the stability of the helical structur