Caslav Lacnjevac

Fast Fourier Transform IR Characterization of Epoxy GY Systems Crosslinked with Aliphatic and Cycloaliphatic EH Polyamine Adducts

The use of fast FT-IR spectroscopy as a sensitive method to estimate a change of the crosslinking kinetics of epoxy resin with polyamine adducts is described in this study. A new epoxy formulation based on the use of polyamine adducts as the hardeners was analyzed. Crosslinking reactions of the different stoichiometric mixtures of the unmodified GY250 epoxy resin with the aliphatic EH606 and the cycloaliphatic EH637 polyamine adducts were studied using mid FT-IR spectroscopic techniques. As the crosslinking proceeded, the primary amine groups in polyamine adduct are converted to secondary and the tertiary amines. The decrease in the IR band intensity of epoxy groups at about 915 cm−1, as well as at about 3,056 cm−1, was observed due to process. Mid IR spectral analysis was used to calculate the content of the epoxy groups as a function of crosslinking time and the crosslinking degree of resin. The amount of all the epoxy species was estimated from IR spectra to changes during the crosslinking kinetics of epichlorhydrin.

Synergetic electrocatalytic effect of d metals for the hydrogen evolution reaction on gold substrates

Abstract An electrocatalytic method developed previously for the depolarization of the hydrogen evolution reaction (HER) on graphite, iron, steel, nickel and titanium substrate surfaces was employed to improve the polarization characteristics of gold. The combination of two d metals from two branches of Balandins “volcano” curve for the HER creates a marked electrocatalytic effect, particularly for molybdenum and cobalt which are added in situ as their anionic or complex species during the electrolytic process. The alloy activity appears to be shifted to potential values that are representative of precious metals and even exceeds these values at higher current densities; the shift is more than 700 mV over the current density range important for similar industrial applications. The synergetic electrocatalytic effects and the improvements in the polarization are illustrated by linear potential sweep voltammograms and steady state Tafel lines. The duration (the lifetime) of the electrocatalytic coating was about 4 months with simple reactivation by means of the in situ addition of negligible amounts of cheap and available cobalt and molybdenum species.

INTERACTIVE SUPPORTED ELECTROCATALYSTS AND SPILLOVER EFFECT IN ELECTROCATALYSIS FOR HYDROGEN AND OXYGEN ELECTRODE REACTIONS

The aim of the present paper has been to introduce the electron conductive and d-d-interactive individual and composite hypo-d-oxides of the increased altervalent capacity, or their suboxides (Magneli phases), as catalytic supports and therefrom provide: (i) The Strong Metal-Support Interaction (SMSI) effect, and (ii) the Dynamic spillover interactive transfer of primary oxides (M-OH) for further electrode reactions, and thereby advance the overall electrocatalytic activity. The d-band has been pointed out as the bonding, adsorptive and catalytic orbital. In the same context, the phenomenon and significance of the d-d-correlations both in heterogeneous catalysis and electrocatalysis are displayed and inferred. Since hypo-d-oxides feature the exchange membrane properties, the higher the altervalent capacity, the higher the spillover effect. Potentiodynamic experiments have shown that the reversible peak of the primary oxide growth on Pt, Ru and Au supported upon hypo-d-oxides and suboxides becomes distinctly increased in the charge capacity and shifts to remarkably more negative potential values, so that it starts even within the range of H-adatoms desorption, while its reduction extends until and merge with the UPD of hydrogen atoms. With wet tungstenia doped titania supported Pt catalyst in membrane cells these peaks dramatically increase in their charge capacity and reversibly become shrunk with a decreased moisture content in the feeding inert gas mixture, and vice versa. Such distinct potentiodynamic scans, in conjunction with some broaden complementary kinetic electrocatalytic improvements rising from the same hypo-d-oxide and/or suboxide interactive support effects, have been proved to be the best and comparable experimental evidence for the spillover effect of primary oxides.

Sustainable conversion of waste biomass using hydrothermal carbonization method

Hydrothermal carbonization represents a process for converting a wet organic material at elevated temperature and pressure in hydro char, coal-like product. The resulting hydro char, depending on the nature of biomass, can be used as a substitute for fossil coal, adsorbent of various pollutants, soil fertility supplement and others. This paper provides insight into the reaction mechanisms, as well as the influence of process parameters. It also highlighted the importance and advantage of the process of hydrothermal carbonization of biomass compared to traditional methods of conversion, as well as the actual implementation of the product.