Study on Lubrication Characteristics of Metal Liquid Film Based on Electromagnetic-Elastic Mechanics-Hydrodynamics Multiphysics Coupling Model.

In an electromagnetic rail launcher, a metal liquid film is created at the armature/rail (A/R) contact interface. It has a significant impact on electromagnetic launch performance. In this paper, an electromagnetic-elastic mechanics-hydrodynamics multi physics coupling model is established in consideration of the metal liquid film's own acceleration, magnetic pressure and dynamic changes in film thickness. Based on this model, the lubricating characteristics of magnetic pressure and fluid pressure distribution, film thickness distribution and velocity distribution of the metal liquid film were studied. When the velocity of the metal liquid film is very fast, and the magnetic pressure is reduced, it may fail to maintain stability and rupture, which may be an important reason for the transition. Finally, this paper analyzes the lubrication effect of the metal liquid film, and points out that when we want strictly to control the muzzle velocity, the lubrication effect of the metal liquid film must be considered.

Conformal Shell Amorphization of Nanoporous Ag-Bi for Efficient Formate Generation.

Simultaneous attainments of high conductivity and superior catalysis are major challenges for amorphous electrocatalysts in carbon dioxide electroreduction at high overpotential. In this study, one protocol is first demonstrated to drive the shell amorphization of nanoporous Ag-Bi (a-NPSB) catalyst with the spatially interconnected ligament during the initial stage of CO2ER. This newborn a-NPSB bestows the outstanding catalysis, evidenced by a Faradaic efficiency of 88.4% for formate production at -1.15 V vs RHE, specific current density of 21.2 mA cm-2, and mass specific current density of 321 mA mg-1. The unique catalysis is considered as the collective contribution of the conductive ligament internally and amorphous Bi2O3 shell with about 3.2 nm thickness externally. Simultaneous obtaining of the conductivity of inner metals and catalytic activity of the amorphous shell will pave a new avenue for designing a robust electrode during electrochemical reaction.

Electrostatic properties of maghemite (γ- Fe(2)O(3)) nanocrystalline quantum dots determined by electrophoretic deposition.

We applied a DC electric field between two flat electrodes to attract thermally charged maghemite (γ-Fe(2)O(3)) nanocrystalline quantum dots dissolved in hexane to form smooth, robust, large area and apparently identical films of equal thickness on both electrodes. Visible microscopy, scanning electron microscopy, atomic force microscopy and profilometry showed that the electrophoretically deposited dot films were very smooth with an rms roughness of ∼10 nm for ∼0.2 µm thick films. The films were of high quality. They did not re-dissolve in hexane (as do those formed by dry casting), which is a good solvent for these dots, or in common cleaning solvents such as water, alcohols and acetone. The deposition on both electrodes implies there are both positively and negatively thermally charged dots, unlike conventional electrophoretic deposition. We used simple thermodynamics to explain the results of electrophoretic deposition macroscopically. To connect the macroscopic nature of the deposition to the microscopic nature of the dots we performed electrophoretic mobility measurements of the dots and the results seem to complement the thermodynamic treatment.