Key Engineering Materials Vol. 903

Abstract: In this paper, the influence of the modification method applied to ground vulcanizate (GV) on the properties of elastomeric compositions based on nitrile rubber is discussed. Modified GV has been mixed with the elastomeric composition, which is used for the manufacturing of oil-petroleum-resistant rubber products.The work takes into consideration two types of GV with different chemical nature. The first GV type is rubber crumb produced from end-of-life tires. The second GV type was obtained from rubber wastes based on nitrile rubber. Three methods of the modification are compared in the research: mechanical activation in a planetary ball mill, swelling in a Polyethylene glycol (PEG-400) medium, and the mechano-chemical transformation of GV with PEG-4000. It is shown that depending on the dosage addition of GV modified with PEG-4000 reduce the compression set up for (16.1±0.7%), the strength decreases only by 2.1–8.3%, and the elongation at break increases by 0.8–10.3% compared to rubber without additives.

Abstract: Investigation presents an experimental study of mechanical properties of hybrid bio-composites made from man-made cellulose fibres and soft wood microfiller embedded into polypropylene homopolymer matrix at different weight contents. Mechanical properties such as elastic modulus, tensile strength, and impact resistance of the reinforced composites determined for various total weight contents of both biobased fillers were used as the design parameters. The problem was solved by planning the experiments and response surfaces method. The results demonstrate that using the both filler types enhance the mechanical properties. The tensile modulus increases by ~115%. The bio-composite with the highest weight content of man-made cellulose fibres and the lowest content of soft wood microfibers possesses maximum tensile strength (more 66 MPa). Addition of man-made cellulose fibres demonstrate a significant influence on the impact resistance of the investigated composites.

Abstract: Supported 3wt%Pd/α-Al₂O₃ catalyst was tested in selective oxidation of 1,2-propanediol by molecular oxygen. It was found that the catalyst is active in an alkaline water solution. Lactic acid was obtained as the main product of the reaction. Influence of different reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. Partial kinetic orders of the reaction with respect to 1,2-propanediol, c₀(NaOH), p(O₂), n(1,2-PDO)/n(Pd)) were determined and an experimental kinetic model of the catalytic oxidation reaction was obtained. Activation energy of the process was calculated and was found to be about 53 ± 5 kJ/mol.

Abstract: Due to its to its optical, thermal, photocatalytic and electrophysical properties, nanocrystalline titanium oxide (TiO₂) is widely used in various fields. In the present work, a series of pure and Gd-modified (0.5, 5, 50 mol%) TiO₂ nanocrystalline powders were prepared by a novel synthesis approach – extraction-pyrolytic method (EPM). Metal containing extracts on the basis of valeric acid were used as precursors. Thermal behavior of produced individual and mixed precursors were investigated by thermogravimetric analysis (TGA) and high temperature differential scanning colometry (HDSC). Phase composition of pure and Gd-modified TiO₂ powders were studied as a function of pyrolysis temperature (450^o -850°C ) and gadolinium content by X-ray diffraction (XRD) method. Photocatalytic activity of produced powders was studied by photocatalytic degradation of methylene blue (MB) under UV/VIS light irradiation.

Abstract: Electron donating phenoxazine and phenothiazine groups were introduced in an electron deficient purine structure through a benzene ring bridge to facilitate thermally activated delayed fluorescence. Mitsunobu and Suzuki-Miyaura reactions were used to synthesize the target compounds. Photophysical properties of target compounds were explored and quantum yields in the thin layer film reached up to 8 % and in the PMMA doped thin layer film up to 15 %.

Abstract: The effect of 6 MeV gamma photons on thermally stimulated exoelectron emission (TSEE) spectra of MgO films was studied. The films were fabricated on Si/SiO₂ substrates using the extraction-pyrolytic method. The crystalline structure and surface morphology of the films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). TSEE spectra of MgO films had emission peaks at about 450 oC and 525 oC. The area under the TSEE peaks increased after repeated TSEE measurements. In the case of gamma-irradiated films, the percentage increase in the area depended on the radiation dose, decreasing linearly with an increase in the radiation dose from 0 to 80 Gy. The results suggest that gamma radiation reduced the density of trapped electrons present in the as-grown MgO films or created competing hole traps that inhibited TSEE from the films.

Abstract: In order to develop reliable methods for the synthesis of various 5-substituted-8-oxyquinoline derivatives for the preparation of Alq3-type complexes, we have improved the reaction conditions on some syntheses described in the literature, successfully synthesized new ligands based on quinolin-8-ol and characterized their chemical structures by NMR. Some of the synthesized quinolin-8-ol derivatives containing incorporated bulky triphenyl or tert-butyl groups showed blue luminescence in the solid state due to the possible aggregation induced emission enhancement (AIEE) with a maximum wavelength around 510 nm. More detailed light-emission property investigation of the mentioned bulky group containing compounds is currently underway.

Abstract: Nanostructured smart coatings (NSC) based on the TiAlSi-CN composite structure elements were deposited using reactive high-power physical vapor deposition (PVD) technique. The advanced modular deposition system included up to 8 high-power magnetron sputtering devices (MSD) allowing operate them simultaneously and exceed power density of 120 W/cm² within each device erosion zone. The novel designed NSC on bearing steel 100Cr6 substrates demonstrated enhanced mechanical and tribological properties comparably with bearing steel ones required for multifunctional high-tech applications. The deposited NSC containing TiAlSi-CN nanoparticles strengthened by elemental additives Cr and Nb exhibited microhardness as high as 2500 HV values in comparison with 750 HV of 100Cr6 steel substrates. Load-displacement curves obey Meyer’s power-law surprisingly well because power-trendline fitted ones by R-squared value of 0.9999 for all the film-samples. Tribological properties were measured under dry friction conditions between the bearing steel ball of Ø 6 mm and the film-samples’ flat surface. Coefficient of friction (CoF) ranges between 0.22-0.56 depending on a sample and load. Tribotracks worn under the friction indenter were too shallow to evaluate them by Mitutoyo profilometer SJ-500. Therefore, the wear rate was estimated as ball wear of the friction indenter.

Abstract: The features of the structure formation of diffusion layers obtained by technology, including preliminary surface treatment of steel products made of U8 steel and subsequent boriding in powder media, have been investigated. The pretreatment consisted of dynamic alloying in the superdeep penetration (SDP) mode with a SiC-based powder composition. As a result, the thickness of the diffusion layer increases, its porosity decreases, and the proportion of the high-boron FeB phase in the layer increases.

Abstract: When using binders in coatings, whose film formation process relays on the oxygen uptake to start the cross-linking reaction, the use of special metal salts, so called driers, can catalyze the process, accelerating the curing of the film and reducing the waiting time between the applications of the next layers of paint. In this work, three primary driers, based on cobalt, iron and manganese are compared, to determine which one is more efficient in drying of alkyd and boiled linseed oil based coating. The study has been done using FTIR spectroscopy to investigate the rate of drying for each drier. The obtained results confirm that using the cobalt drier, the film formation is faster than with the other two alternative driers.