RESUMEN
The electrical conductivity, density and diffusion coefficients of trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide ([P66614][NTf2]) ionic liquid and its binary solutions in acetonitrile, propionitrile, dimethyl and diethyl carbonates were measured in the temperature range of 293-348 K. The electrical conductivity - ionic liquid mole fraction dependencies for the binary solutions were fitted with the empirical Casteel-Amis equation. The temperature dependencies of electrical conductivity were analyzed using the Arrhenius, Litovitz and Vogel-Fulcher-Tammann approaches. The dependences of the Arrhenius activation energy and pre-exponential factor on the mole fraction of ionic liquid in the solutions were fitted with the empirical equations proposed in the literature. The thermo-gravimetric analysis combined with mass spectrometry demonstrated the high thermal stability of [P66614][NTf2] up to 600 K. At higher temperatures the decomposition of [P66614][NTf2] proceeded via the elimination of alkyl radicals as a result of the nucleophilic attack of reactive intermediates to the [P66614]+ cation with the formation of trialkylphosphines. The activation energies of the thermal destruction of [P66614][NTf2] were calculated using the Kissinger equation and non-linear integral isoconversional model.
RESUMEN
The paper proposes a technology based on UV-LIGA process for microoptoelectromechanical systems (MOEMS) manufacturing. We used the original combination of materials and technological steps, in which any of the materials does not enter chemical reactions with each other, while all of them are weakly sensitive to the effects of oxygen plasma. This made it suitable for long-term etching in the oxygen plasma at low discharge power with the complete preservation of the original geometry, including small parts. The micromembranes were formed by thermal evaporation of Al. This simplified the technique compared to the classic UV-LIGA and guaranteed high quality and uniformity of the resulting structure. To demonstrate the complete process, a test MOEMS with electrostatic control was manufactured. On one chip, a set of micromembranes was created with different stiffness from 10 nm/V to 100 nm/V and various working ranges from 100 to 300 nm. All membranes have a flat frequency response without resonant peaks in the frequency range 0-200 kHz. The proposed technology potentially enables the manufacture of wide low-height membranes of complex geometry to create microoptic fiber sensors.
RESUMEN
Thermal defunctionalization of oxidized jellyfish-like few-layer graphene nanoflakes was studied under non-isothermal conditions by simultaneous thermal analysis. Activation energies for thermal decomposition of different oxygen functional groups were calculated by the Kissinger method and compared with those for oxidized carbon nanotubes. Oxygen content in graphene nanoflakes was found to significantly affect the decomposition activation energies of carboxylic and keto/hydroxy acids because of their acceptor properties and strong distortion of the graphene layers at the edges of the nanoflakes. The structure of the carbon material and the oxygen chemical state significantly influence the decomposition kinetics of thermally stable oxygen-containing groups. The activation energy for thermal decomposition of phenol groups (110-150 kJ mol-1) is close to that for graphene oxide reduction.