| 1. |
- Wrzesińska, Angelika, et al.
(author)
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Structural, electrical, and magnetic study of La-, Eu-, and Er- doped bismuth ferrite nanomaterials obtained by solution combustion synthesis
- 2021
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In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:22746
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Journal article (peer-reviewed)abstract
- In this work, the multiferroic bismuth ferrite materials Bi0.9RE0.1FeO3 doped by rare-earth (RE = La, Eu, and Er) elements were obtained by the solution combustion synthesis. Structure, electrical, and magnetic properties of prepared samples were investigated by X-ray photoelectron spectroscopy, Mössbauer spectroscopy, electrical hysteresis measurement, broadband dielectric spectroscopy, and SQUID magnetometry. All obtained nanomaterials are characterized by spontaneous electrical polarization, which confirmed their ferroelectric properties. Investigation of magnetic properties at 300.0 K and 2.0 K showed that all investigated Bi0.9RE0.1FeO3 ferrites possess significantly higher magnetization in comparison to bismuth ferrites obtained by different methods. The highest saturation magnetisation of 5.161 emu/g at 300.0 K was observed for the BLaFO sample, while at 2.0 K it was 12.07 emu/g for the BErFO sample. Several possible reasons for these phenomena were proposed and discussed.
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| 2. |
- Ali, Sharafat, Associate Professor, 1976-, et al.
(author)
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Investigation of the structural and thermal properties of aluminum-rich Ca–Al–Si–O–N glasses
- 2023
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In: Progress in Solid State Chemistry. - : Elsevier. - 0079-6786 .- 1873-1643. ; 71
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Journal article (peer-reviewed)abstract
- In this paper, we investigate the structure and thermal properties of aluminum-rich transparent Ca–Al–Si–O–N glasses. The obtained glasses were prepared by a traditional melt-quenching technique at 1650 °C using AlN as the nitrogen source. The obtained glasses have a nAl/nSi>1 and contain up to 17 eq.% of N. The structure of the glasses was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, infrared, and Raman spectroscopy techniques. The structure analysis shows a higher preference for Si–N bond formation relative to Al–N bond formation and aluminum is predominately present in tetrahedral coordination as AlO4 units. The thermal properties of samples were studied by differential thermal analysis and the obtained glass transition temperature ranges from 875 °C to 950 °C, and is primarily influenced by the N content. The glass stability can be correlated with both the N and Al contents in the studied glasses. It is improved due to the increased degree of network polymerization by the incorporation of nitrogen.
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| 3. |
- Kharitonov, Dmitry S., et al.
(author)
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Aqueous molybdate provides effective corrosion inhibition of WE43 magnesium alloy in sodium chloride solutions
- 2021
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In: Corrosion Science. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0010-938X .- 1879-0496. ; 190
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Journal article (peer-reviewed)abstract
- Corrosion and corrosion inhibition of WE43 magnesium alloy were investigated in NaCl solutions containing different amounts of sodium molybdate. Electrochemical, microscopic, and spectroscopic experiments were utilized to examine the mechanism of corrosion inhibition by molybdates. Electrochemical data showed that Na2MoO4 inhibitor provides reliable inhibition at concentrations at and above 100 mM. Raman and XPS spectroscopy demonstrated that the formed surface layer consists of mixed Mo(V, IV) species. This layer provided inhibition with an efficiency of 91-99 % after 24 h of exposure. A two-step oxidation-reduction mechanism of corrosion inhibition of the WE43 alloy by aqueous molybdates was proposed.
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| 4. |
- Kharitonov, Dmitry S., et al.
(author)
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Corrosion inhibition of aluminium alloy AA6063-T5 by vanadates : Local surface chemical events elucidated by confocal Raman micro-spectroscopy
- 2019
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In: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 148, s. 237-250
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Journal article (peer-reviewed)abstract
- Chemical interactions between aqueous vanadium species and aluminium alloy AA6063-T5 were investigated in vanadate-containing NaCl solutions. Confocal Raman and X-ray photoelectron spectroscopy experiments were utilised to gain insight into the mechanism of corrosion inhibition by vanadates. A greenish-grey coloured surface layer, consisting of V+4 and V+5 polymerized species, was seen to form on the alloy surface, especially on top of cathodic micrometre-sized IMPs, whereby suppressing oxygen reduction kinetics. The results suggest a two-step mechanism of corrosion inhibition in which V+5 species are first reduced to V+4 or V+3 species above cathodic IMPs, and then oxidized to mixed-valence V+5/V+4 polymerized compounds.
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| 5. |
- Kharitonov, Dmitry S., et al.
(author)
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Surface and corrosion properties of AA6063-T5 aluminum alloy in molybdate-containing sodium chloride solutions
- 2020
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In: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 171
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Journal article (peer-reviewed)abstract
- Corrosion properties of aluminum alloy AA6063-T5 were investigated in molybdate-containing NaCl solutions. Electrochemical, microscopic, and spectroscopic experiments were utilized to examine the mechanism of corrosion inhibition by molybdates. SEM-EDX, magnetic force, and intermodulation electrostatic force microscopy data suggested that the inhibition initiation preferentially occurred over Fe-rich cathodic IMPs. Spectroscopic measurements demonstrated that the formed surface layer consists of mixed Mo(VI, V, IV) species. This layer provided inhibition with an efficiency of ∼90% after 4 h of exposure. High efficacy of ∼70% was achieved even after one week of exposure. A two-step oxidation-reduction mechanism of corrosion inhibition by aqueous molybdates was proposed. © 2020 The Authors
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| 6. |
- Makarava, Iryna, et al.
(author)
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Influence of CeO2 and TiO2 Particles on Physicochemical Properties of Composite Nickel Coatings Electrodeposited at Ambient Temperature
- 2022
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In: Materials. - : MDPI. - 1996-1944. ; 15:16
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Journal article (peer-reviewed)abstract
- The Ni-TiO2 and Ni-CeO2 composite coatings with varying hydrophilic/hydrophobic characteristics were fabricated by the electrodeposition method from a tartrate electrolyte at ambient temperature. To meet the requirements of tight regulation by the European Chemicals Agency classifying H3BO3 as a substance of very high concern, Rochelle salt was utilized as a buffer solution instead. The novelty of this study was to implement a simple one-step galvanostatic electrodeposition from the low-temperature electrolyte based on a greener buffer compared to traditionally used, aiming to obtain new types of soft-matrix Ni, Ni-CeO2, and Ni-TiO2 coatings onto steel or copper substrates. The surface characteristics of electrodeposited nickel composites were evaluated by SEM, EDS, surface contact angle measurements, and XPS. Physiochemical properties of pure Ni, Ni-CeO2, and Ni-TiO2 composites, namely, wear resistance, microhardness, microroughness, and photocatalytic activity, were studied. Potentiodynamic polarization, EIS, and ICP-MS analyses were employed to study the long-term corrosion behavior of coatings in a 0.5 M NaCl solution. Superior photocatalytic degradation of methylene blue, 96.2% after 6 h of illumination, was achieved in the case of Ni-TiO2 composite, while no substantial change in the photocatalytic behavior of the Ni-CeO2 compared to pure Ni was observed. Both composites demonstrated higher hardness and wear resistance than pure Ni. This study investigates the feasibility of utilizing TiO2 as a photocatalytic hydrophilicity promoter in the fabrication of composite coatings for various applications.
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| 7. |
- Makarova, Irina, et al.
(author)
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Nickel-nanodiamond coatings electrodeposited from tartrate electrolyte at ambient temperature
- 2019
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 380
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Journal article (peer-reviewed)abstract
- In this study, nanocrystalline Ni and Ni-diamond coatings were obtained by electrodeposition from tartrate electrolyte at ambient temperature aiming at improving corrosion and wear properties of the material. The created surfaces were investigated with regard to microhardness, adhesion, wear- and corrosion-resistance. The various methods such as atomic force microscopy, scanning electron microscopy, electrochemical impedance spectroscopy and linear polarization technique were applied to study the coating surface properties. The introduction of nanodiamond particles into the coating led to a rougher surface structure and a bigger grain size in comparison to bare nickel coating. Our study shows that the addition of 5·10−2 (g dm−3) of nanodiamonds to the plating bath is enough to obtain composite coatings with a clear increase in microhardness and wear resistance. The slightly improved corrosion resistance of the coating, decrease in corrosion current density from 0.41 to 0.14 μA cm−2 in neutral chloride-containing medium, and nobler values of the corrosion potential were also observed.
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| 8. |
- Milewczyk, Zuzanna, et al.
(author)
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Correlations of structural, thermal and electrical properties of sodium doped complex borophosphosilicate glass
- 2024
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In: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 50:17, s. 29937-29946
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Journal article (peer-reviewed)abstract
- Borophosphosilicate glasses with varying sodium ion concentrations were investigated for their, structural, thermal, and electrical properties. All the obtained glasses were transparent except the glass with the highest sodium content, which exhibited translucency due to inhomogeneities. Increasing sodium content led to reduced boron and silicon content while maintaining a constant B/Si ratio, indicating progressive depolymerization of the glass network. Confocal microscopy, scanning electron microscopy, and atomic force microscopy showed homogeneous and granular structure for samples with lower sodium content, but higher sodium content resulted in visible agglomeration/nanocrystallization. X-ray diffractograms showed amorphous nature for most samples, with samples doped with the highest concentrations of Na2O showing several broad reflections suggesting nanoscale crystallinity. Fourier -transform infrared spectroscopy revealed shifts in dominant bands with increasing sodium content, indicating depolymerization of the borate network. An observed decrease in glass transition temperature and thermal stability with increasing sodium content was attributed to depolymerization and formation of non -bridging oxygens. Impedance spectroscopy revealed two relaxation processes associated with the transport of Na+ ions through two different regions. DC conductivity and activation energy predominantly increased with the sodium ion content at high temperatures.
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| 9. |
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| 10. |
- Wojcik, Natalia Anna, et al.
(author)
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Effect of crystallinity on structural, thermal, and in vitro dissolution properties of Na2O-CaO-Nb2O5/MgO-P2O5 glass-ceramics
- 2023
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In: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 43:5, s. 2234-2244
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Journal article (peer-reviewed)abstract
- The impact of the crystallinity on structural, thermal, and in vitro dissolution properties were examined for Na2O-CaO-Nb2O5/MgO-P2O5 glasses/glass-ceramics. Glass-ceramics were synthesized via a spontaneous crystallization process. The Nb content in the materials increased with melting temperature, furthermore, the crystallinity is proportional to the Nb content. The presence of crystalline niobates and phosphates is confirmed by FTIR analysis which is consistent with XRD. The FTIR results indicate that the phosphate network is built of different proportions of Q2, Q1, and Q0 units, depending on the amount and type of crystalline phase. Most of the samples show an improvement in thermal stability. The in vitro dissolution test showed that the highest mass loss for most of the samples occurred during the first 6 days of immersion in the PBS solution. The presence of small phosphate crystals favors the deposition of hydroxyapatite on samples' surfaces while the larger niobate crystals dissolve more readily.
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| 11. |
- Wójcik, Natalia A., et al.
(author)
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Mechanism of hopping conduction in Be-Fe-Al-Te-O semiconducting glasses and glass-ceramics
- 2022
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In: Journal of Materials Science. - : Springer Nature. - 0022-2461 .- 1573-4803. ; 57, s. 1633-1647
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Journal article (peer-reviewed)abstract
- Electrical properties of beryllium-alumino-tellurite glasses and glass-ceramics doped with iron ions were studied using impedance spectroscopy. The conductivity was measured over a wide frequency range from 10 mHz to 1 MHz and the temperature range from 213 to 473 K. The D.C. conductivity values showed a correlation with the Fe-ion concentration and ratio of iron ions on different valence states in the samples. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity parameters were determined and compared to theoretical models collected by Elliott. In glasses, the conduction process was found to be due to the overlap polaron tunneling while in glass-ceramics the quantum mechanical tunneling between semiconducting crystallites of iron oxides is proposed. The D.C. conductivity was found not to follow Arrhenius relation. The Schnakenberg model was used to analyze the conductivity behavior and the polaron hopping energy and disorder energy were estimated. Additionally, the correlation between alumina dissolution and basicity of the melts was observed.
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