Hindered molecular reorientation of lithium ion doped succinonitrile in the terahertz range
The THz range permittivity of succinonitrile exhibits Debye-like behavior in its plastic-crystal phase, with a characteristic Cole-Cole relaxation time of 65ps ±17ps which increases considerably in the presence of ionic dopants.
Dielectric relaxation spectroscopy for evaluation of the influence of solvent dynamics on ion transport in succinonitrile-salt plastic crystalline electrolytes.
Influence of succinonitrile (SN) dynamics on ion transport in SN-lithium perchlorate (LiClO(4)) electrolytes is discussed here via dielectric relaxation spectroscopy. Dielectric relaxation spectroscopy (∼2×10(-3) Hz to 3 MHz) of SN and SN-LiClO(4) was studied as a function of salt content (up to 7 mol % or 1 M) and temperature (-20 to +60 °C). Analyses of real and imaginary parts of permittivity convincingly reveal the influence of trans-gauche isomerism and solvent-salt association (solvation) effects on ion transport. The relaxation processes are highly dependent on the salt concentration and temperature. While pristine SN display only intrinsic dynamics (i.e., trans-gauche isomerism) which enhances with an increase in temperature, SN-LiClO(4) electrolytes especially at high salt concentrations (∼0.04-1 M) show salt-induced relaxation processes. In the concentrated electrolytes, the intrinsic dynamics was observed to be a function of salt content, becoming faster with an increase in salt concentration. Deconvolution of the imaginary part of the permittivity spectra using Havriliak-Negami (HN) function show a relaxation process corresponding to the above phenomena. The permittivity data analyzed using HN and Kohlrausch-Williams-Watta (KWW) functions show non-Debye relaxation processes and enhancement in the trans phase (enhanced solvent dynamics) as a function of salt concentration and temperature.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.