Rok: 2023

Influence of process and heat input on the microstructure and mechanical properties in wire arc additive manufacturing of hot work tool steels

Posted on by Mária Čaplovičová

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.

Ag2O nanocrystals prepared by mechanochemical decomposition of Ag7O8NO3

Posted on by Mária Čaplovičová

Martin Škrátek, Mária Čaplovičová, Ľubomír Čaplovič, Patrícia Petrisková, Erik Šimon, Erik Rakovský, Peter Billik

In: Materials Letters. Vol. 348, (2023)

https://doi.org/10.1016/j.matlet.2023.134680

Abstract

Our work focuses on the preparation of nanocrystalline Ag2O (n-Ag2O) by mechanochemical decomposition (MCD) of a paramagnetic compound of an empirical formula Ag7O8NO3. Electrochemically prepared millimetre-long needles of Ag7O8NO3 were high-energy ball milled (HEM) for 1 min, 3 min and 5 min. A gradual decomposition of Ag7O8NO3 to n-Ag2O and AgNO3 was observed. Ag2O nanocrystals form in an aggregated and spherical morphology with crystallite sizes ranging from ∼10 – 30 nm. n-Ag2O displayed weak ferromagnetism with the saturation magnetisation of 5×10–3 emu/g. The MCD of Ag7O8NO3 can be estimated as follows: 2Ag7O8NO3 → 6Ag2O + 2AgNO3 + 5O2.

Green Colloidal Synthesis of MoS2 Nanoflakes

Posted on by Viliam Vretenár

Filip Zechel, Peter Hutár, Viliam Vretenár, Karol Végsö, Peter Šiffalovič, and Milan Sýkora

In: Inorg. Chem. 2023, 62, 40, 16554–16563

https://doi.org/10.1021/acs.inorgchem.3c02420

Abstract

Currently, two approaches dominate the large-scale production of MoS2: liquid-phase exfoliation, referred to as the top-down approach, and bottom-up colloidal synthesis from molecular precursors. Known colloidal synthesis approaches utilize toxic precursors. Here, an alternative green route for the bottom-up synthesis of MoS2 nanoflakes (NFs) is described. The NFs were synthesized by colloidal synthesis using [Mo(CH3COO)2]2 and a series of sulfur (S)-precursors including thioacetamide (TAA), 3-mercaptopropionic acid (3-MPA), l-cysteine (L-CYS), mercaptosuccinic acid (MSA), 11-mercaptoundecanoic acid (MUA), 1-dodecanethiol (DDTH), and di-tert-butyl disulfide (DTBD). While TAA, an S-precursor most commonly used for MoS2 NF preparation, is a known carcinogen, the other investigated S-precursors have low or no known toxicity. High-resolution scanning transmission electron microscopy (HR-STEM) and grazing incidence wide-angle X-ray scattering (GIWAXS) confirmed that in all cases, the syntheses yielded single-layer MoS2 NFs with lateral sizes smaller than 15 nm and a well-defined crystal structure. Electronic absorption and Raman spectra showed characteristic features associated with the MoS2 monolayers. The evolution of the absorption spectra of the growth solution during the syntheses reveals how the kinetics of the NF formation is affected by the S-precursor as well as the nature of the coordinating ligands.

Application of MXene for remediation of low-level radioactive aqueous solutions contaminated with 133Ba and 137Cs

Posted on by Mária Čaplovičová

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.

Tailoring the electronic properties of the SnO2 nanoparticle layer for n-i-p perovskite solar cells by Ti3C2TX MXene

Posted on by Mario Kotlár

Muhammad Faraz Ud Din, Shima Sousani, Mário Kotlár, Sami Ullah, Maros Gregor, Tomas Scepka, Yaryna Soyka, Anastasiia Stepura, Ashin Shaji, Femi Igbari, Karol Vegso, Vojtech Nadazdy, Peter Siffalovic, Matej Jergel, Maria Omastova, Eva Majkova

In: Materials Today Communications, Volume 36, (2023)

https://doi.org/10.1016/j.mtcomm.2023.106700

Abstract

The effect of the Ti3C2Tx MXene modification of the SnO2 electron transport layer (ETL) was studied for the concentration range 0–7.4 wt% MXene. The electronic properties of the MXene-modified ETL were studied by the electrical conductivity measurements, density of states mapping by the energy-resolved electrochemical impedance spectroscopy, ultraviolet photoelectron spectroscopy, and photoluminescence. The structure and morphology of the MXene-modified ETL and the top perovskite layer were analyzed by the scanning electron microscopy (SEM), scanning transmission electron microscopy, grazing-incidence X-ray diffraction and in situ grazing-incidence wide-angle X-ray scattering (GIWAXS). The increased electrical conductivity and electron selectivity for the MXene-modified SnO2 ETL was confirmed up to 1 wt% MXene. For 7.4 wt% MXene, significant suppression of the hole blocking property of the ETL was found. The in situ GIWAXS was performed during the post-deposition annealing of the perovskite layer. The increased perovskite grain size on the SnO2 ETL modified by MXene compared to the pure SnO2 ETL visible by SEM was confirmed. The uniaxial texture of the perovskite crystals was revealed in both cases with an increased misorientation angle for the MXene-modified ETL. The grain size and misorientation angle do not exhibit any systematic temporal changes during the post-deposition annealing. The increasing number of the grains during the annealing was observed. These results are explained using the nucleation and growth model. The increased power conversion efficiency from 17.4% to 18.3% of the archetypal methylammonium-lead-iodide perovskite solar cell after the modification of the SnO2 ETL with 0.1 wt% MXene is the effect of two contributions – increased electrical conductivity of the ETL and improved crystallinity and larger grain size compared to the pure SnO2 ETL, which lowers the total boundary area and charge recombination at trap states typically formed at grain boundaries.

Thermoplastic starch/bentonite clay nanocomposite reinforced with vitamin B2: Physicochemical characteristics and release behavior

Posted on by Mario Kotlár

Abolfazl Heydari, Milad KhajeHassani, Haniyeh Daneshafruz, Sepideh Hamedi, Faeze Dorchei, Mário Kotlár, Fahimeh Kazeminava, Samahe Sadjadi, Farideh Doostan, Ivan Chodak, Hassan Sheibani

In: International Journal of Biological Macromolecules. Vol. 242, (2023)

Abstract

This study presents the development and characterization of a nanocomposite material, consisting of thermoplastic starch (TPS) reinforced with bentonite clay (BC) and encapsulated with vitamin B2 (VB). The research is motivated by the potential of TPS as a renewable and biodegradable substitute for petroleum-based materials in the biopolymer industry. The effects of VB on the physicochemical properties of TPS/BC films, including mechanical and thermal properties, water uptake, and weight loss in water, were investigated. In addition, the surface morphology and chemical composition of the TPS samples were analyzed using high-resolution SEM microscopy and EDS, providing insight into the structure-property relationship of the nanocomposites. The results showed that the addition of VB significantly increased the tensile strength and Young’s modulus of TPS/BC films, with the highest values observed for nanocomposites containing 5 php of VB and 3 php of BC. Furthermore, the release of VB was controlled by the BC content, with higher BC content leading to lower VB release. These findings demonstrate the potential of TPS/BC/VB nanocomposites as environmentally friendly materials with improved mechanical properties and controlled release of VB, which can have significant applications in the biopolymer industry.

GaAs ablation with ultrashort laser pulses in ambient air and water environments

Posted on by Mária Čaplovičová

Edgaras Markauskas,  Laimis Zubauskas, Arnas Naujokaitis, Bronislovas Čechavičius, Martynas Talaikis, Gediminas Niaura, Mária Čaplovičová, Viliam Vretenár, Tadas Paulauskas

In: Journal of Applied Physics. Vol. 133, iss. 23 (2023)

https://doi.org/10.1063/5.0152173

Abstract

Water-assisted ultrashort laser pulse processing of semiconductor materials is a promising technique to diminish heat accumulation and improve process quality. In this study, we investigate femtosecond laser ablation of deep trenches in GaAs, an important optoelectronic material, using water and ambient air environments at different laser processing regimes. We perform a comprehensive analysis of ablated trenches, including surface morphological analysis, atomic-resolution transmission electron microscopy imaging, elemental mapping, photoluminescence, and Raman spectroscopy. The findings demonstrate that GaAs ablation efficiency is enhanced in a water environment while heat-accumulation-related damage is reduced. Raman spectroscopy reveals a decrease in the broad feature associated with amorphous GaAs surface layers during water-assisted laser processing, suggesting that a higher material quality in deep trenches can be achieved using a water environment.

Performance assessment of a triple-junction solar cell with 1.0 eV GaAsBi absorber

Posted on by Viliam Vretenár

Tadas Paulauskas, Vaidas Pačebutas, Viktorija Strazdienė, Andrejus Geižutis, Jan Devenson, Mindaugas Kamarauskas, Martynas Skapas, Rokas Kondrotas, Mantas Drazdys, Matas Rudzikas, Benjaminas Šebeka, Viliam Vretenár, Arūnas Krotkus

In: Discover Nano. Vol. 18, iss. 1 (2023)

 doi: 10.1186/s11671-023-03865-x

Abstract

Group III-V semiconductor multi-junction solar cells are widely used in concentrated-sun and space photovoltaic applications due to their unsurpassed power conversion efficiency and radiation hardness. To further increase the efficiency, new device architectures rely on better bandgap combinations over the mature GaInP/InGaAs/Ge technology, with Ge preferably replaced by a 1.0 eV subcell. Herein, we present a thin-film triple-junction solar cell AlGaAs/GaAs/GaAsBi with 1.0 eV dilute bismide. A compositionally step-graded InGaAs buffer layer is used to integrate high crystalline quality GaAsBi absorber. The solar cells, grown by molecular-beam epitaxy, achieve 19.1% efficiency at AM1.5G spectrum, 2.51 V open-circuit voltage, and 9.86 mA/cm2 short-circuit current density. Device analysis identifies several routes to significantly improve the performance of the GaAsBi subcell and of the overall solar cell. This study is the first to report on multi-junctions incorporating GaAsBi and is an addition to the research on the use of bismuth-containing III-V alloys in photonic device applications.

Polycaprolactone–MXene Nanofibrous Scaffolds for Tissue Engineering

Posted on by Mária Čaplovičová

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, Mária 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 Ti3C2Tx 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.

Electrochemical modified Pt nanoflower @ rGO for non- enzymatic electrochemical sensing of glucose

Posted on by Mario Kotlár

Saravanan Gengan, R.M. Gnanamuthu, Sanjay Sankaranarayanan, Venumbaka Maneesh Reddy, Bhanu Chandra Marepally, Ravi Kumar Biroju

In: Sensors and Actuators A: Physical, Volume 353, (2023)

https://doi.org/10.1016/j.sna.2023.114232

Abstract

Since lower danger of biorecognition element degradation, enzymes-less glucose have the potential for more reliable in vivo activity, but it suffers due to lack of linear response and poor selectivity. We made attempt to improve selectivity, linear response and stability, environmentally benign electrochemical method adopted to fabricate Pt nanoflowers (PtNF) anchored on rGO modified GCE (PtNF-rGO/GCE). The PtNF-rGO/GCE electrode demonstrated good glucose electrooxidation in alkaline solution, with a linear range, sensitivity and detection limit are up to 3.5 mM, 335.5 μA mM−1 cm−1 and 53 μM (S/N = 3) respectively. The PtNF-rGO/GCE electrode is not only selective also inhibit interfering molecules like uric, dopamine, ascorbic acid. This allows for broadly sensitive, work at low-potential, stable, and quick glucose current detection, which is capable for the expansion of non-enzymatic glucose detectors.