Volume 18 (2018): Issue 4 (December 2018)

Activated carbons and carbon nanotube were synthesized with chemical and microwave processes of olive leaf in media with and without ultrasonic waves, and chemical vapor deposition method, respectively. The samples were characterized by x-ray diffraction, calorimetry, Brunauer, Emmett and Teller method, scanning electron microscopy/energy-dispersive X-ray, and zetasizer nano S90 instruments. The activated carbon synthesized in the ultrasonic bath had a higher surface area. The hydrogen adsorption capacity of carbon structures including activated carbons and carbon nanotube was measured as a function of pressure at 77 K. The hydrogen storage capacity of the carbon nanotube is 300% and 265% higher than the hydrogen storage capacity of activated carbons synthesized in medium without and with ultrasonic waves, respectively. Results showed the correlation between hydrogen storage capacity and specific surface area. The highest H₂ storage value was obtained with carbon nanotube at 77 K. As a result, activated carbon and carbon nanotube can be used in hydrogen storage and therefore, the olive leaf can be converted into a high added value product in the energy field.

The surface condition of an implant has a significant impact on response occurring at the implant-biosystem border. The knowledge of physical-chemical and biological processes allows for targeted modification of biomaterials to induce a specified response of a tissue. The present research was aimed at development of technology composing of obtaining the nanotube oxide layers on a porous titanium alloy Ti13Nb13Zr, followed by the deposition of phosphate coating. The porous substrate (porosity about 50%) was prepared by a selective laser melting of the Ti13Nb13Zr powder with the SLM Realizer 100 equipment. The nanotubular oxide layers were fabricated by electrochemical oxidation in H₃PO₄ + 0.3% HF mixture for 30 min. at a constant voltage of 20V. The calcium phosphate coatings were formed by the electrochemically assisted deposition (ECAD). The presence of nanotubular oxide layers with their internal diameters ranging from 30 to 100 nm was observed by SEM (JEOL JSM-7600F). The nanotubes have dimensions that facilitated the deposition of hydroxyapatite.

The paper presents results of investigations of the microstructure and selected properties of improved composite coatings consisting mainly of nickel matrix reinforced by WC particles. The coatings were obtained by flame spraying of powders mixture on non-alloy steel substrates with following material remelting. Structural investigations were performed using both optical and electron microscopy. The distribution of microhardness and abrasion resistance of deposited coatings were also determined. The complex structure of coatings and resulting high wear withstand are the consequence of an intensive action of liquid matrix with dissolving tungsten carbide particles and formation of secondary phases.

Bismuth niobate (BiNbO₄) has attracted attention as a low-fired ceramics with promising microwave application potential. BiNbO₄ ceramics was fabricated by mixed oxide method and sintered at temperature T<1000°C. As the sintering aids a small amount of CuO oxide was used. The crystalline structure of the ceramic samples was examined by X-ray diffraction method at room temperature. The Rietveld refinement method was used for analysis of diffraction data. As a result an influence of dopants on crystal structure of bismuth niobate (BiNbO₄) ceramics was revealed. It was found that fabricated BiNbO₄ ceramics adopted the orthorhombic symmetry (α-BiNbO₄ phase, Pnna (52) space group). Small differences in elementary cell parameters were found.

This article presents the results of an examination of the properties of thermal flame sprayed coatings produced by material in the form of four powders (two polymers: PA11 and PA12 CastoPlast, and two high purity: tin and aluminum) on the substrate of the unalloyed structural steel of S235JR grade. Investigations of coating properties are based on metallography tests (SEM and CLSM), measurement of microhardness (acc. to PN-EN ISO 6507-1:2007), anticorrosive (acc. to PN-EN ISO 9227:2017-06) and bend testing. Results demonstrate properties of flame sprayed coatings that are especially promising in the industrial applications where corrosion-resistant coating properties are required. Consequently, performed experiments show that the highest corrosion resistance is demonstrated by steel samples with a polyamide anti-corrosion system. Accelerated corrosion tests showed the lowest corrosion resistance of the tin coating system, however, they do not fully correspond to the corrosion processes in operating conditions.