Centrum pre nanodiagnostiku materiálov

Andrii Lys, Viktor Zabolotnii, Mária Čaplovičová, Iryna Tepliakova, Agris Berzins, Martin Sahul, Ľubomír Čaplovič, Alexander Pogrebnjak, Igor Iatsunskyi, Roman Viter

In: Journal of Alloys and Compounds, Volume 984, 15 May 2024, 173885

https://doi.org/10.1016/j.jallcom.2024.173885

Abstract

Recent research places significant importance on the development of innovative nanocomposites for photoelectrochemical applications. This paper presents the fabrication, characterization, and possible photoelectrochemical applications of novel ZnFe₂O₄/ZnO core-shell nanofibers. These core-shell nanofibers were fabricated through co-axial electrospinning using PVP solutions containing iron and zinc nitrate precursors for the core and shell. The structural and optical properties of ZnFe₂O₄/ZnO core-shell nanofibers were examined through TEM, SEM, XRD, FTIR, Raman spectroscopy, and diffuse reflectance spectroscopy. This comprehensive analysis unveiled that the development of core and shell characteristics was notably influenced by the interdiffusion of [Fe]/[Zn] during the annealing process. The photoelectrochemical properties of ZnFe₂O₄/ZnO core-shell nanofibers were assessed through electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and the Mott-Schottky method. These core-shell nanofibers demonstrated a robust electrochemical response to visible light. Photocurrent and photoconversion efficiency of the core-shell nanofibers were calculated and compared with the corresponding values for core-shell nanoparticles. The mechanisms underlying the structural, optical, and photoelectrochemical properties of ZnFe₂O₄/ZnO core-shell nanofibers were discussed. These advanced nanofibers hold potential applications in photocatalysis, photovoltaics, and energy storage, making this research timely and crucial for advancing sustainable energy technologies and environmental remediation efforts.

Florian Pixner, Ricardo Buzolin, Fernando Warchomicka, Mária Dománková, Mária Čaplovičová, Florian Riedlsperger, Sebastian Fritsche, Marta Orłowska, Josef Domitner, Michael Lasnik, Norbert Enzinger 

In: Materials Science and Engineering: A, Volume 888, 17 November 2023, 145799

https://doi.org/10.1016/j.msea.2023.145799

Abstract

The present study demonstrates the suitability of wire arc additive manufacturing (AM) for hot work tool steel processing. Different arc welding techniques and energy inputs were applied and systematically compared to determine the deposition characteristics, microstructure and mechanical properties. All AM deposits show a sound visual appearance and full density without macroscopic imperfections, i.e. cracking. By adhering to a pre-defined interpass strategy, the cold metal transfer process can be used to achieve higher weld beads with lower dilution and faster build-up rates than the metal active gas process. The microstructure of the AM parts is comparable for all process configurations and consists of an α/α′-matrix with a finely dispersed vermicular and polygonal δ-ferrite network; no notable amount of retained austenite could be measured, but it could be observed by transmission electron microscopy embedded within the laths. Intensive precipitation of multiple molybdenum-based precipitates is observed along the interface matrix to δ-ferrite. In contrast, iron-based precipitates are predominantly found inside and at the boundaries of the laths of the matrix. Similarities are also evident in the mechanical properties, resulting in an average hardness of 380–390 HV1 and absorbed impact energy of 10–12 J at room temperature. High yield strength values of 1000–1100 MPa and ultimate tensile strength of 1200–1400 MPa were obtained. No significant differences in the measured mechanical properties could be noted regarding the specimen orientation, indicating the isotropy of the properties.

Vipul Vilas Kusumkar, Shalu Atri, Süleyman İnan, Maros Gregor, Tomas Roch, Hryhorii Makarov, Maria Caplovicova, Michal Galambos, Eva Viglasova, Gustav Plesch and Olivier Monfort

In: Chem. Commun., 2023,59, 12007-12010

https://doi.org/10.1039/D3CC02147E

Abstract

MXene is an innovative multilayered material that has been prepared by an acid-salt (HCl + NH₄F) etching route and tested for the removal of ¹³³Ba and ¹³⁷Cs in radioactive conditions for the first time. MXene has exhibited high uptake capacity of about 154.9 and 121.5 mg g⁻¹ for ¹³³Ba and ¹³⁷Cs, respectively, in 0.01 mol L⁻¹ solution and using 5 g L⁻¹ of adsorbent at natural pH.

Kateryna Diedkova, Alexander D. Pogrebnjak, Sergiy Kyrylenko, Kateryna Smyrnova, Vladimir V. Buranich, Pawel Horodek, Pawel Zukowski, Tomasz N. Koltunowicz, Piotr Galaszkiewicz, Kristina Makashina, Vitaly Bondariev, Martin Sahul, Maria Čaplovičová, Yevheniia Husak, Wojciech Simka, Viktoriia Korniienko, Agnieszka Stolarczyk, Agata Blacha-Grzechnik, Vitalii Balitskyi, Veronika Zahorodna, Ivan Baginskiy, Una Riekstina, Oleksiy Gogotsi, Yury Gogotsi, and Maksym Pogorielov

In: ACS Applied Materials & Interfaces. Vol. 15, iss. 11 (2023)

https://doi.org/10.1021/acsami.2c22780

Abstract

New conductive materials for tissue engineering are needed for the development of regenerative strategies for nervous, muscular, and heart tissues. Polycaprolactone (PCL) is used to obtain biocompatible and biodegradable nanofiber scaffolds by electrospinning. MXenes, a large class of biocompatible 2D nanomaterials, can make polymer scaffolds conductive and hydrophilic. However, an understanding of how their physical properties affect potential biomedical applications is still lacking. We immobilized Ti₃C₂T_x MXene in several layers on the electrospun PCL membranes and used positron annihilation analysis combined with other techniques to elucidate the defect structure and porosity of nanofiber scaffolds. The polymer base was characterized by the presence of nanopores. The MXene surface layers had abundant vacancies at temperatures of 305–355 K, and a voltage resonance at 8 × 10⁴ Hz with the relaxation time of 6.5 × 10⁶ s was found in the 20–355 K temperature interval. The appearance of a long-lived component of the positron lifetime was observed, which was dependent on the annealing temperature. The study of conductivity of the composite scaffolds in a wide temperature range, including its inductive and capacity components, showed the possibility of the use of MXene-coated PCL membranes as conductive biomaterials. The electronic structure of MXene and the defects formed in its layers were correlated with the biological properties of the scaffolds in vitro and in bacterial adhesion tests. Double and triple MXene coatings formed an appropriate environment for cell attachment and proliferation with mild antibacterial effects. A combination of structural, chemical, electrical, and biological properties of the PCL–MXene composite demonstrated its advantage over the existing conductive scaffolds for tissue engineering.

BAKARDJIEVA, Snejana – MAREŠ, Jakub – KOCI, Eva – TOLASZ, Jakub – FAJGAR, Radek – RYUKHTIN, Vasyl – KLEMENTOVÁ, Mariana – MICHNA, Štefan – BIBOVÁ, Hana – HOLMESTAD, Randi – TITORENKOVA, Rositsa – ČAPLOVIČOVÁ, Mária.

In Nanomaterials. Vol. 12, iss. 5 (2022)

https://doi.org/10.3390/nano12050750

Abstract

Ag-decorated TiO₂ nanostructured materials are promising photocatalysts. We used non-standard cryo-lyophilization and ArF laser ablation methods to produce TiO₂ nanosheets and TiO₂ nanostructured thin films decorated with Ag nanoparticles. Both methods have a common advantage in that they provide a single multiply twinned Ag⁽⁰⁾ characterized by {111} twin boundaries. Advanced microscopy techniques and electron diffraction patterns revealed the formation of multiply twinned Ag⁽⁰⁾ structures at elevated temperatures (500 °C and 800 °C). The photocatalytic activity was demonstrated by the efficient degradation of 4-chlorophenol and Total Organic Carbon removal using Ag-TiO₂ nanosheets, because the multiply twinned Ag⁽⁰⁾ served as an immobilized photocatalytically active center. Ag-TiO₂ nanostructured thin films decorated with multiply twinned Ag⁽⁰⁾ achieved improved photoelectrochemical water splitting due to the additional induction of a plasmonic effect. The photocatalytic properties of TiO₂ nanosheets and TiO₂ nanostructured thin films were correlated with the presence of defect-twinned structures formed from Ag⁽⁰⁾ nanoparticles with a narrow size distribution, tuned to between 10 and 20 nm. This work opens up new possibilities for understanding the defects generated in Ag-TiO₂ nanostructured materials and paves the way for connecting their morphology with their photocatalytic activity.