Zoran Samardžija’s research while affiliated with Jožef Stefan Institute and other places

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Publications (116)


Electrochemical cell with Pt mesh as counter electrode (CE), Ag/AgCl reference electrode (RE) and copper tape with Nd-Fe-B powder as working electrode (WE).
CV of the Cu-plate in copper-containing solution (a) and copper-free solution (b).
CVs of the Nd-Fe-B-bulk electrode (a) in copper-free (light grey) and copper-containing solution (black), started at 0 V, and (b) in iron(II)-containing (dark grey), copper-free (light grey) and copper-containing solution (black), started at −0.6 V.
SEM images of Cu deposits on Nd-Fe-B electrodes after 30 s of deposition under various applied potential conditions: (a) BSE image, bulk Nd-Fe-B electrode, −1.05 V; (b) BSE image, bulk Nd-Fe-B electrode, −0.5 V; (c) SE image, powdered Nd-Fe-B electrode (Nd₂Fe₁₄B grains), −0.5 V; (d) BSE image, Nd₂Fe₁₄B grains in cross-section, −0.5 V; (e) SE image, powdered Nd-Fe-B electrode (Nd₂Fe₁₄B grains), −0.25 V; (f) BSE image, Nd₂Fe₁₄B grains in cross-section, −0.25 V; (g) SE image, powdered Nd-Fe-B electrode (Nd₂Fe₁₄B grains), −0.5 V ultrasonic agitation; (h) BSE image, Nd₂Fe₁₄B grains in cross-section, −0.5 V, ultrasonic agitation.
Chronoamperometric data for Cu deposition at E = −0.25 V for 30 s (a) without agitation (black line) and with US agitation (grey line). In the bottom right the total negative charge passed within the 30 s deposition period is presented for both cases (a). Current–time curves for Cu deposition at E = −0.5 V for 30 s (b) without agitation (black line) and with agitation (grey line). In the bottom right the total negative charge passed within the 30 s deposition period is presented for both cases (b).

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Electrochemical Insights into Copper Electrodeposition on Nd2Fe14B Grains: A Proof-of-Concept Study
  • Article
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February 2025

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33 Reads

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Mihaela Rebernik

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Kristina Žužek

This study explores Cu electrodeposition from a near-neutral sulphate bath onto Nd-Fe-B bulk and powder electrodes. The former served for the preliminary electrochemical tests, while the latter was used for Cu coating of the corrosion-sensitive powdery raw material. Cyclic voltammetry established the potential intervals for Cu deposition (at least −0.1 V and below) and the Nd-Fe-B oxidation (above −0.5 V). Cu electrodepositions were performed on both electrodes in potentiostatic mode for 30 s. Scanning electron microscopy/energy-dispersive spectroscopy showed that Cu deposited at high overpotentials (−1.05 and −0.5 V) had a dendritic structure mainly due to mass transport limitations. A chronoamperometric study on Nd2Fe14B powder electrodes at −0.25 V resulted in a positive current, indicating the Nd-Fe-B oxidation dominance. At −0.5 V, the current remained negative, but showed diffusion limitations. The latter was improved by using ultrasonic agitation, which resulted in a higher total negative charge and more uniform Cu deposits on Nd2Fe14B grains. Cu-coated Nd₂Fe₁₄B grains showed a mass magnetization decrease from 137 to 127 emu g⁻¹, corresponding to a ∼9% Cu mass increase determined via gravimetry. The study demonstrates successful Cu electrochemical deposition with no magnetization loss beyond the paramagnetic Cu phase, paving the way for grain-boundary engineering of novel Nd-Fe-B magnets.

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Electrochemical Detection of Benzenediols using Carbon-Supported Catalysts

May 2024

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12 Reads

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2 Citations

Electrochimica Acta

A novel implementation of an electrochemical sensors making use of Screen-Printed Electrodes (SPE) has been discussed. SPE's modified with Carbon-supported Platinum (Pt/C) and Gold (Au/C) were used to detect the three benzenediol isomers, Catechol (CC), Hydroquinone (HQ) and Resorcinol (RS) in acidic media using traditional electrochemical analytical methods such as Cyclic Voltammetry (CV), Chronoamperometry (CA) and Differential Pulse Voltammetry (DPV). Detection of each benzenediol in isolation was possible by CV measurements, and peak oxidation potentials for each isomer were noted. Simultaneous detection of more than one, or all analytes in the same solution was also observed through DPV, once again noting the peak oxidation potentials. Quantification limits were observed using CA's across concentration values ranging from close to saturation down to 1 mM for CC and HQ, and 100 nM for RS, until the recorded current values were nearly indistinguishable to a blank 1 M HCl solution containing no analyte(s), and also evaluating the maximum possible linear range of sensing. The analytes were introduced to the sensor elements in controlled amounts and the electrochemical responses of the sensor elements were recorded and processed. Measurements were repeated across two potentiostats to ensure reproducibility. With these results, successful detection of benzenediols in acidic environment was possible using modified SPE's, proving a potential viable mechanism for quick, simple and inexpensive Volatile Toxic Organic Compounds (VTOC) detection and monitoring.



Effect of Al-Cu-Fe Quasicrystal Particles on the Reinforcement of a Polymer–Matrix Composite: From Surface to Mechanical Properties

February 2024

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114 Reads

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4 Citations

We examined the effect of Al59Cu25Fe13B3 (at.%) quasicrystalline (QC) reinforcement particles on the mechanical and surface properties of a polymer-matrix composite by applying a technical polymer polyphthalamide (PPA). The observed increase in the tensile Young’s modulus ranged from 1810 MPa for the pure polymer to 4114 MPa for the composite with a QC filling of 35 vol.%. The elongation at fracture decreased with the filling fraction, being equal to 16.9% for a pure polymer and dropping to 4.8% for the composite with a QC filling of 35 vol.%. The same trend was noticeable with flexural Young’s modulus, which ranged from 100 MPa for a pure polymer to 125.5 MPa for the composite with 35 vol.% of QC. It was found that the increase in the mechanical strength led to a simultaneous increase of brittleness, which was reflected in a decrease of the impact strength for a pure polymer from 98.5 kJ/m2 to 42.4 kJ/m2 for composites with a QC filling of 35 vol.%. In contrast, when filled with 5 vol.% of QC, the impact strength increased by 8%. The friction coefficient against 100C6 steel dropped from 0.15 for pure PPA down to 0.10 for 5 vol.% of the QC filling, followed by an increase to 0.26 for further QC fillings up to 35 vol.%. Interestingly, a local minimum of friction was achieved at filling factors between 5 to 20 vol.% of QC. Independently, a clear surfenergy minimum was also found for the composite material with 20 vol.% of QC filling associated with a net drop in the polar component of the surfenergy. Surfenergy refers to the surface energy related to the top of the oxide layer under ambient conditions. We hypothesise that this is related to the percolation threshold at about 13 vol.% QC, reflected in the observed behaviour of both the friction coefficient and surfenergy. For the pure QC annealed in air for 1 h at 500 °C significant wear tracks were observed accompanied by a wear debris formation. On the other hand, a pure polymer exhibited slightly visible wear tracks with no apparent debris formation, and for the composites with different QC filling factors, the wear traces were barely visible with negligible debris formation.



Environmentally Friendly Approach for Nd2Fe14B Magnetic Phase Extraction by Selective Chemical Leaching: A Proof-of-Concept Study

July 2023

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135 Reads

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4 Citations

The green transition initiative has exposed the importance of effective recycling of Nd-Fe-B magnets for achieving sustainability and foreign independence. In this study, we considered strip-cast, hydrogenated, jet-milled Nd-Fe-B powder as a case study to explore the potential for selective chemical leaching of the Nd-rich phase, aiming to extract the Nd2Fe14B matrix phase. Diluted citric and nitric acids at concentrations of 0.01, 0.1, and 1 M were considered potential leaching mediums, and the leaching time was 15 min. Microstructural investigation, magnetic characterization, and elemental compositional analysis were performed to investigate leaching efficiency and selectivity. Based on SEM analysis, Nd/Fe ratio monitoring via ICP-MS, and the high moment/mass value at 160 emu/g for the sample leached with 1 M citric acid, 1 M citric acid proved highly selective toward the Nd-rich phase. Exposure to nitric acid resulted in a structurally damaged Nd2Fe14B matrix phase and severely diminished moment/mass value at 96.2 emu/g, thus making the nitric acid unsuitable for selective leaching. The presence of hydrogen introduced into the material via the hydrogen decrepitation process did not notably influence the leaching dynamics. The proposed leaching process based on mild organic acids is environmentally friendly and can be scaled up and adopted for reprocessing industrial scrap or end-of-life Nd-Fe-B magnets to obtain single-phase Nd-Fe-B powders that can be used for novel magnet-making.


Impact of Tuned Oxidation on the Surface Energy of Sintered Samples Produced from Atomised B-Doped Al-Cu-Fe Quasicrystalline Powders

May 2023

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112 Reads

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5 Citations

Super-hydrophobic surfaces and coatings have stimulated a great deal of research, with the aim being to achieve better wetting properties. Factors such as surface chemistry and roughness play an important role in changing the surface energy, which in turn leads to changes in the wettability. Here, we have analysed the time dependence of the oxide layer and possible surface adsorbates on the surface topography of an Al59Cu25Fe13B3 quasicrystalline material in relation to changes in the wettability. The quasicrystalline matrix phase was 94% of the sample volume, and it was covered by a very smooth, amorphous oxide layer. The AlB12 and AlFe2B2 boron-rich phases were embedded in the quasicrystalline material as a result of the 3 at.% boron addition, which made atomisation of the material a simpler process. Under ambient conditions, the sample was naturally covered by an oxide layer; therefore, it is referred to as “surfenergy” to distinguish it from the conventional surface energy of a bare quasicrystal surface. The growth of the oxide layer with atmospheric ageing and annealing at 500 °C in air for various times was investigated for both cases. The phase most prone to oxidation was the boron-rich AlFe2B2, which influenced the topography of the surface and accordingly the wetting behaviour of the specimen. We demonstrated that the surfenergy depends on the polar component, which is the most sensitive to the operating conditions. A correlation between the surfenergy components and the surface roughness was found. In addition, theoretical models to determine the wettability were included.


Figure 1. Sketch of a sessile drop, vapour/liquid/solid system. The contact angle is shown (í µí»©í µí»©). (a) the shape of a water droplet as a polar liquid on a QC surface, and the shape of a diiodomethane droplet as an apolar liquid on a QC surface with associated components. (b) The plot of cos í µí»©í µí»© versus í µí±¥í µí±¥ = �í µí»¾í µí»¾ í µí±™í µí±™ í µí±™í µí±™ í µí±‘í µí±‘ í µí»¾í µí»¾ í µí±™í µí±™ í µí±™í µí±™ � parameter for pure water (labelled by a full circle) and diiodomethane (labelled by a diamond) for our quasicrystalline sample.
Figure 3. XPS spectra C 1s, Al 2p/Cu 3p, Fe 2p and Cu 2p with indicated oxidation states measured on the sample surface after ageing for 0.5h.
Figure 8. TEM images of the QC annealed at 500 °C for 1 h in air. (a) Overall image with the presented phases in the bulk, (b) High-magnification image of the oxides on the surface labelled as 1 and 2 with associated FFT pattern of the oxide layer. The insets show the electron-diffraction patterns of the elongated ternary AlFe2B2 phase (up) and the i-phase along the 2-fold axis (down). (c) shows the EDXS mapping of the high-magnification oxide layer above the AlFe2B2 phase and the i-phase.
Impact Of Tuned Oxidation on the Surface Energy of Sintered Samples Produced from Atomised B-Doped Al-Cu-Fe Quasicrystalline Powders

April 2023

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115 Reads

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1 Citation

Super-hydrophobic surfaces and coatings have stimulated a great deal of research, with the aim to achieve better wetting properties. Factors such as surface chemistry and roughness play an important role in changing the surface energy, which in turn leads to changes in the wettability. Here, we have analysed the time dependence of the oxide layer and possible surface adsorbates on the surface topography of an Al59Cu25Fe13B3 quasicrystalline material for changes to the wettability. The quasicrystalline matrix phase was 94 % of the sample volume, and covered by a very smooth, amorphous oxide layer. The AlB12 and AlFe2B2 boron-rich phases were embedded in the quasicrystalline material as a result of a 3 at.% boron addition, which makes atomisation of the material a simpler process. Under ambient conditions the sample was naturally covered by an oxide layer; therefore, it is referred to as “surfenergy”, to distinguish it from the conventional surface energy of a bare quasicrystal surface. The growth of the oxide layer with atmospheric ageing and annealing at 500° C in air for various times was investigated for both cases. The phase most prone to oxidation was the boron-rich AlFe2B2, which influenced the topography of the surface and accordingly the wetting behaviour of the specimen. We demonstrated that the surfenergy depends on the polar component, which is the most sensitive to the operating conditions. A correlation between the surfenergy components and the surface roughness was found. In addition, theoretical models to determine the wettability were included.


Fig. 4a). These results show that the unit cell dimensions of all samples are larger in comparison to the bulk PMN-33PT. As the c/a ratios calculated from the RSMs vary, this may indicate a variation in the domain structure/orientation. The structure of bulk PMN-33PT at room temperature is monoclinic.[37] Different orientations of the monoclinic structure would
Figure 4: a) Pseudocubic lattice parameters of the PMN-PT layers. b) FWHM of the PMN-PT layers along the ω and θ-2θ direction.
Figure 7: Longitudinal piezoelectric coefficients.
Chemical compositions of the samples prepared from targets with different excess of Pb and Mg compared to the stoichiometric composition (bottom row). The numbers of decimal places for individual elements are defined by the measurement errors.
Non-stoichiometry and its implications for the properties of PMN-PT thin films

January 2023

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69 Reads

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3 Citations

Journal of Materials Chemistry C

0.67[Pb(Mg 1/3 Nb 2/3 )O 3 ]-0.33[PbTiO 3 ] (PMN-33PT) epitaxial thin films were prepared by pulsed-laser deposition (PLD) using ceramic targets, enriched with PbO (and MgO). The phase composition and crystal structure were analyzed by high-resolution X-ray...



Citations (78)


... This is evident in Figure 5, comparing analogue and digital CVs at different scan rates. In both the analogue and digital CVs, we can see that increasing the scan rates produces a higher overall measured output current as we go from 10 mVs −1 to 25 mVs −1 , 50 mVs −1, and 100 mVs −1 despite having the same concentration of hydroquinone (5 mM) [23]. This agrees with the theory that the increase in current is due to the increase in the capacitive current only, with no contribution from the faradaic current of the redox of hydroquinone. ...

Reference:

Influence of Potentiostat Hardware on Electrochemical Measurements
Electrochemical Detection of Benzenediols using Carbon-Supported Catalysts

Electrochimica Acta

... Nevertheless, their inherent brittleness [53,54] limits their application as single-phase materials, while they hold substantial potential when employed as reinforcements [55]. Spark plasma sintering [56], hot press sintering [57], injection moulding of polymer reinforced QC [58] are several examples of successful incorporation of QC into the matrix with improved mechanical properties. Cold spraying, in particular, has also been implemented to fabricate wear-resistant Ti/Al-Cr-Fe(QC) [59] and CuSn/AlCuFeB(QC) [60]. ...

Effect of Al-Cu-Fe Quasicrystal Particles on the Reinforcement of a Polymer–Matrix Composite: From Surface to Mechanical Properties

... Store-bought fabric was used for the colonization study and characterized by Fourier-transform infrared spectroscopy (FTIR) as polyethylene terephthalate (PET), as described in Matjašič et al. (2020). The fabric was washed in a washing machine at 40 • C and exposed to sunlight for about a month. ...

Preliminary experiments into colonization of microorganisms from activated sludge on different types of plastics

Acta Biologica Slovenica

... [20][21][22] Those were later stripped chemically for our study to remove the Nd-rich grainboundary phase. 17,23 The process resulted in a Nd₂Fe₁₄B main matrix phase on which the Cu was deposited. ...

Environmentally Friendly Approach for Nd2Fe14B Magnetic Phase Extraction by Selective Chemical Leaching: A Proof-of-Concept Study

... However, the formation of oxides on the surface might have smoothing effects, further enhancing the appearance of rounded shapes [97,98]. Oxidation might also alter the surface energy and interactions between particles, influencing how they aggregate and adhere [99,100]. It's possible that the combined effects of the ball mill and subsequent oxidation were responsible for the observed rounded or circular shapes in the resultant ball-milled powder. ...

Impact of Tuned Oxidation on the Surface Energy of Sintered Samples Produced from Atomised B-Doped Al-Cu-Fe Quasicrystalline Powders

... To uncover the origin of the enhanced capacitive energy density in Sm-PMN-30PT thin films, we investigated the structural properties of the grown film, including in-plane cell parameters, strain state, and domain structures. As shown in Fig. 1f, bottom electrodes [39]. Furthermore, the in-plane (ε-xx) and out-of-plane (ε-yy) strains from the TSO substrate across the SRO electrode and in the first ~60 nm of the Sm-PMN-30PT layer were analyzed using geometric phase analysis (GPA), as shown in Fig. 5b. ...

Non-stoichiometry and its implications for the properties of PMN-PT thin films

Journal of Materials Chemistry C

... Additionally, the ability of PANI to store NH 4 + makes it suitable for application as an NH 4 +attracting and -storing material [70]. Inspired by these properties, Korent et al. developed an Au-decorated polyaniline-based sensing platform for aqueous ammonia monitoring ( Figure 4A) [44]. The sensor was operated using an amperometric method. ...

Au-decorated electrochemically synthesised polyaniline-based sensory platform for amperometric detection of aqueous ammonia in biological fluids

Electrochimica Acta

... The scientific and practical fascination with REE-containing magnets continues to grow [3,17], leading to ongoing research on their doping with REE and other chemical elements. The non-stereotypical and multicomponent nature of this material presents a From Table 1, it is observed that the waste from magnetic materials may include zirconium and copper at the whole percent level and iron at the level of tens of percent; there are also significant amounts of nickel and hafnium. ...

Electrochemical routes for environmentally friendly recycling of rare-earth-based (Sm–Co) permanent magnets

Journal of Applied Electrochemistry

... However, most studies addressing the microbial communities in streams have investigated benthic or epilithic biofilms that include photoautotrophic microorganisms (e.g. Ylla et al. 2012Ylla et al. , 2014Oest et al. 2018;Romero et al. 2019;Dang et al. 2021; Thomas et al. 2021;Zhang et al. 2021), while fewer studies have focused on predominantly heterotrophic microbial communities from the hyporheic zones, i.e. hyporheic biofilms (but see Nogaro et al. 2010;Wagner et al. 2014;Mori et al. 2019;Matjašič et al. 2021). ...

Presence of polyethylene terephthalate (PET) fibers in hyporheic zone alters colonization patterns and seasonal dynamics of biofilm metabolic functioning
  • Citing Article
  • July 2021

Water Research

... Goodfellow Cambridge Ltd.) were used as the working and counter electrodes, respectively. A detailed description of the experimental setup can be found in our previous work [24]. The electrochemical surface treatment was performed at 50 V for 15-30 min in 20 mL of ethylene glycol (EG) (99.5%, Carlo Erba Reagents) electrolyte containing 0.1-0.45 ...

The Influence of a Surface Treatment of Metallic Titanium on the Photocatalytic Properties of TiO2 Nanotubes Grown by Anodic Oxidation

Catalysts