Volume 54, Nº 5 (2018)

Calix[4]arenesulfonic acid complexation with perchloric acid is studied. The stoichiometric composition of the complex is shown to be calix[4]arene/HClO₄ = 1/1. The complex is most stable against humidity changes as far as its proton-conducting properties are concerned. Its specific proton conductivity varies from 3 × 10^–3 to 5 × 10^–2 S/cm; the conductivity activation energy is 0.16 ± 0.04 eV. The studying of the effect of HClO₄ amount on the samples’ physico-chemical properties at low humidity showed the proton transfer in the material to be determined by the crystallites’ bulk, rather than surface, characteristics.

The effect of electrochemical and gas-phase activation of high-surface-area carbon black Ketjen Black EC 600 DJ on its stability and electrochemical capacitance is studied. The electrochemical activation is carried out according to the “start–stop” protocol (1–1.5 V, 0.5 V/s). The stability of samples is assessed based on variation of their effective resistance (based on the results of cyclic voltammetry (CVA)) and electrochemical capacitance (based on CVA and galvanostatic data) with the cycle number. The changes in the texture and surface properties of activated samples are studied by the methods of nitrogen low-temperature adsorption and X-ray photoelectron spectroscopy. The gas-phase activation of high-surface-area carbon black Ketjen Black EС 600 DJ is shown to impair its stability, while the electrochemical oxidation of carbonblack samples leads to a considerable (two-fold) increase in their electrochemical capacitance.

Olivine-structured LiFe_0.97Ni_0.03PO₄/C/Ag nanomaterials of varying dispersibility are prepared by using sol–gel synthesis with subsequent milling. The materials are certified using X-ray diffraction analysis, scanning electron microscopy, low-temperature nitrogen adsorption, and electrochemical testing under the lithium-ion battery operating conditions. The LiFe_0.97Ni_0.03PO₄/C/Ag cathode material primary particles’ size was shown to decrease, under the intensifying of ball-milling, from 42 to 31 nm, while the material’s specific surface area increased from 48 to 65 m²/g. The discharge capacity, under slow charging–discharging (C/8), approached a theoretical one for all materials under study. It was found that under fast charging–discharging (6 C and 30 C) the discharge capacity is inversely proportional to the particles’ mean size. The discharge capacity under the 6 С current came to 75, 94, 97, and 106 mA h/g for the initial material and that milled at a rotation velocity of 300, 500, and 700 rpm, respectively. An increase in the lithium diffusion coefficient upon the samples’ intense milling is noted.

A method for the analysis of corrosion process involving two cathodic reactions and one anodic reaction is proposed. By way of example, this method is used to calculate a particular cathodic polarization curve with two Tafel portions. The calculated polarization curve coincides with the experimental curve measured on stainless steel in 0.5 M HCl solution.