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.
Fast ion conduction in molecular plastic crystals
Doping of lithium salts and acids into the plastic crystal phase of succinonitrile has shown for the first time of the possibility of creating solid state electrolytes based on plastic crystalline solvents where the matrix itself is neutral and hence not intrinsically conductive. These materials illustrate the concept of a solid state electrolyte solvent. Room temperature conductivities up to 3.4×10−4 S cm−1 were obtained with 5 wt.% lithium bis(trifluoromethanesulfonylamide) in succinonitrile. Pulsed field gradient NMR measurements indicate that both cation and anion are mobile in this lattice. Proton conductivity was also observed when methane sulfonic acid or glacial acetic acid was used as dopants, however, the conductivity in these systems is limited by the poor dissociating ability of these acids.
Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet
In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.