Прегледај по Аутор "Bučko, Mihael"

Сада се приказује 1 - 3 од 3
  • Сличица
    Ставка
    Ceria Particles as Efficient Dopant in the Electrodeposition of Zn-Co-CeO2 Composite Coatings with Enhanced Corrosion Resistance: The Effect of Current Density and Particle Concentration
    (MDPI, 2021) Riđošić, Marija; Bučko, Mihael; Salicio-Paz, Asier; García-Lecina, Eva; Živkovic, Ljiljana S.; Bajat, Jelena B.
    Novel Zn-Co-CeO2 protective composite coatings were deposited successfully from chloride plating solutions. Two different types of ceria sources were used and compared: commercial ceria powder and home-made ceria sol. Electrodeposition was performed by a direct current in the range of 1–8 A dm􀀀2. Two different agitation modes were used and compared, magnetic stirring and ultrasound-assisted stirring (US). The influence of magnetic stirring on the stability of the related plating baths was evaluated via a dynamic scattering method. The results pointed to better stability of the prepared ceria sol. The morphology of the composite coatings was examined by scanning electron microscopy (SEM), and particle content was determined by energy-dispersive X-ray spectroscopy (EDS). The results showed that the increase in the deposition current density was not beneficial to the coating morphology and particle content. The corrosion behavior of the Zn-Co-CeO2 composite coatings was analyzed and compared by electrochemical impedance spectroscopy and polarization resistance. The ultrasound-assisted electrodeposition at small current densities was favorable for obtaining composite coatings with enhanced corrosion stability. The protection was more effective when US was applied and, additionally, upon utilization of ceria sol as a particle source, which was revealed by higher polarization resistance and greater low-frequency impedance modulus values for sol-derived composite coatings deposited under ultrasound.
  • Сличица
    Ставка
    Hardness and corrosion resistance of Zn−Mn/Al2O3 composite coatings produced by electrochemical deposition
    (National Institute of Science Communication and Policy Research (CSIR-NIScPR), 2022) Bučko, Mihael; Riđošić, Marija; Kovačina, Jovanka; Tomić, Milorad V.; Bajat, Jelena B.
    The aim of this study is development and characterization of the novel Zn-Mn/Al2O3 composite coatings. The coatings were electrodeposited with constant current density on steel, from chloride solution, without any commercial additives. The Zn−Mn alloy coatings that show high corrosion resistance, may be used in future as an alternative to cadmium coatings. However, the pure Zn and Zn alloy coatings are characterized with poor mechanical properties. Therefore, in this work the alumina particles were incorporated into the Zn-Mn matrix, and the hardness and corrosion resistance of the obtained composite coatings were tested. The mechanical and ultrasound agitation were used to achieve good dispersion of plating solution and homogeneous co-deposition of second phase. The goal was to examine the effect of the agitation type in bath, on the attributes of the deposited composite coatings. The incorporation of Al2O3 particles was enhanced when the mechanical agitation of the solution was applied. However, in case that this agitation method was used, the agglomeration of the alumina particles occurred. In contrast, when an ultrasonic agitation of the plating solution was applied, the uniform distribution of the alumina particles could be achieved. The presence of particles in the matrix, along with applied ultrasound, resulted in grain refinement and homogeneous microstructure. The Al2O3 nanoparticles incorporated in Zn-Mn alloy matrix, resulted in a significant increment in the indentation hardness and a modest increase in the coating corrosion resistance. However, the coating hardness increased with alumina addition, only in case when an ultrasonic agitation of the electrodeposition solution was used.
  • Сличица
    Ставка
    Vibration and Temperature Measurement Based Indicator of Journal Bearing Malfunction
    (Faculty of Mechanical Engineering in Slavonski Brod; Faculty of Electrical Engineering, Computing and Information Technologies Osijek; Faculty of Civil Engineering and Architecture Osijek, 2018) Antunović, Ranko; Halep, Amir; Bučko, Mihael; Perić, Sreten; Vučetić, Nikola
    This paper aims to present the development and implementation of the new malfunction indicator in journal bearings, based on vibrational and thermal records, called DFJB-Defect Factor Journal Bearing. Briefly, the indicator contains the specifically processed information about the bearing vibrations and temperature, on the basis of which the DFJB is calculated using fuzzy logic, and thus the state of the journal bearing may be determined. It should be pointed out that the DFJB is developed in a manner that besides the temperature and the total number of absolute vibrations, it may also integrate following parameters of monitoring: the parameters of rotating vibrations, vibrations spectrum, the thickness of oil film in the journal bearing, the intensity of the ultrasound emission of the bearing etc. These parameters may in certain cases offer more reliable malfunction identification. Experimental investigations conducted in this work, on real machine equipment and in real exploitation conditions, have shown this method to be reliable in the identification of malfunctions in journal bearings. As a result of implementation of DFJB, the time necessary to collect measuring data is significantly shortened, whereas the diagnosis procedure for journal bearings is highly simplified. This is particularly important in complex technical systems with a vast number of measuring points, which often result in the overload of the operator.