Electron paramagnetic resonance in organic binder aging in dispersely reinforced substructures

Purpose: To study the intensity of binder aging in organo-mineral mixtures using electron paramagnetic resonance. The aging intensity of the organic binder is provided by its concentration in paramagnetic centers, since asphaltenes are almost one hundred percent of paramagnet concentration and indicate to the aging intensity of the petroleum dispersion system.Approach: Dispersed reinforcement of substructures with chemical fibers made of spent sorbents containing a controlled amount of absorbed oil products allows to partially solve the problem of crack formation and fracture of road pavements designed in accordance with the regulatory documents.Research implications: The service life of substructure made of dispersely reinforced organo-mineral mixtures reduces owing to organic binder aging, which begins at the stage of preparation of organo-mineral mixtures and continues during the substructure operation. Organic binder ageing results in the formation of solvation layers on the surface of mineral materials that become more viscous and brittle.Findings: The substructure dispersed reinforcement with chemical fibers made of spent sorbents containing a controlled amount of absorbed oil products decreases the concentration of paramagnetic centers. This indicates to a decrease in the asphaltene concentration, thereby reducing the aging intensity of the oil dispersion system.

Synthesis and Characterisation of Cobalt Ferrite Coatings for Oxygen Evolution Reaction

In this paper, two novel procedures based on powder sedimentation, thermal treatment, and galvanostatic deposition were proposed for the preparation of porous cobalt ferrite (CoFe2O4) coatings with a metallic and organic binder for use as catalysts in the oxygen evolution reaction (OER). The electrochemical properties of the obtained electrode materials were determined as well, using both dc and ac methods. It was found that cobalt ferrite coatings show excellent electrocatalytic properties towards the oxygen evolution reaction (OER) with overpotential measured at a current density of 10 mAcm−2 from 287 to 295 mV and a Tafel slope of 35–45 mVdec−1. It was shown that the increase in the apparent activity of the CoFe2O4 coatings with an organic binder results mainly from a large electrochemically active area. Incorporation of the nickel binder between the CoFe2O4 particles causes an increase in both the conductivity and the electrochemically active area. The Tafel slopes indicate that the same rate-determining step controls the OER for all obtained coatings. Furthermore, it was shown that the CoFe2O4 electrodes exhibit no significant activity decrease after 28 h of oxygen evolution. The proposed coating preparation procedures open a new path to develop high-performance OER electrocatalysts.

Materials and Techniques of Selected Mural Paintings on the “Gothic Road” around 1400 (Slovakia)

Mural cycles in the churches of Plešivec, Čhyžné, and Štitnik from around 1400 were studied from the material and technical point of view. Stylistically, they show a mixture of Northern and Southern European stylistic currents, which were characteristic for the time around 1400 in East Central Europe. After a precise study in situ, an analysis of extracted samples was conducted by OM, SEM-EDX, and XRD. The plasters used for these murals were all made of lime and sand with different impurities; importantly, they different among each other in terms of their quality and stability. The pigments that were used in these murals were natural and organic: lime white, yellow and red earths, malachite, and azurite were identified, and some pigment degradations were also pointed out. The principal technique is a fresco, but all murals were finished a secco in different proportions, using an organic binder. Painting procedures and modelling were also studied, revealing a strong difference among all three cycles. The painting technique does not always correspond to the style.

Study of an Organic Binder of Cold-Bonded Briquettes with Two Different Iron Bearing Materials

The aim of this study was to investigate the properties of an organic binder used in cold-bonded briquettes (CBBs) prepared from two different iron bearing materials. The applied binder is a type of starch as indicated by chemical analysis, iodine-starch staining and Fourier transform infrared analyses. Thermogravimetric differential scanning calorimetry showed that the binder pyrolysis undergoes four stages: moisture desorption, ash volatilization, pyrolysis of organic matter and decomposition of materials with high activation energy. The difference between the dry and heat-treated samples during the macroscopic failure process is the instability propagation of the crack. The CBB shows a low decrepitation index at 700 °C. The returned fines of CBBs used with the organic binder were applied in two blast furnaces. The industrial trials showed that the CBBs do not influence the performance of the blast furnace and can reduce the fuel consumption rate. The curing rate of the binder decreases, and the growth rate of compressive strength decreases during the curing process. Iron ore particles are bonded together and exist in the form of aggregation after mixing with water and binder. The edges and corners of the particles become blurred, and the original surfaces of the particles are covered with binder film, the surface of which is covered with fine particles. The multi-branched structure of amylopectin provides omnibearing adhesion sites, thus forming binder agglomeration and film leading to a strong adhesion between binder and iron ore particles. Binder film and binder agglomeration work together to make the CBB perform well.