Publikační činnost Katedry chemie / Publications of Department of Chemistry (617)

Permanent URI for this collectionhttp://hdl.handle.net/10084/64746

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry chemie (617) v časopisech registrovaných ve Web of Science od roku 2003 do roku 2022.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

Browse

Now showing 1 - 20 out of 205 results

Highly carbonized Prunus dulcis shell-derived activated carbon for high-performance supercapacitor applications
(Springer Nature, 2022) Kandasamy, Senthil Kumar; Ravindaran, Ramyea; Michalska, Monika; Muthusamy, Suresh; Almutairi, Tahani Mazyad; Panchal, Hitesh; Gorji, M. R.; Alrubai, Ali Jawad; Mohamed, Mohamed A.; Jaber, Mustafa Musa
Recently, the supercapacitor has gained more consideration due to its speedy charging and discharging, high power density, and stability compared to the existing batteries. Activated carbon-based electrodes for the supercapacitor provide higher specific capacitance. In this research, activated carbon was obtained from Prunus dulcis (almond fruit) shell by carbonization using a muffle furnace. Carbonized Prunus dulcis fruit shells were chemically activated by potassium hydroxide (KOH). X-ray diffraction (XRD) patterns of KOH-activated carbon derived from Prunus dulcis shell evident that the activated carbon samples are amorphous. The scanning electron microscope (SEM) images of activated carbon derived from Prunus dulcis exhibited a 2D sheet-like morphology and a smooth surface. Energy-dispersive X-ray spectroscopy (EDX) detected oxygen, chloride, and potassium peaks with 85.2% carbon. The addition of KOH helped to increase the porosity of the fruit shells and enhanced the absorption of the electrolyte. The supercapacitor electrode was prepared by coating activated carbon on a graphite pencil lead. The performance of the electrode was evaluated using a 6 M KOH electrolyte at various current densities and scan rates. The prepared sample was electrochemically characterized by cyclic voltammetry, galvanostatic charge and discharge measurements, and electrochemical impedance spectroscopy. From the analysis, the suitability of the material as an electrode can be understood. The specific capacitance of the samples was measured as 434, 237, 105.9, and 50.5 F g(-1) at 1, 2, 4, and 10 A g(-1), respectively. The higher specific capacitance is ascribed to the high specific surface area, electrolyte, and pore volume. And also, at an energy density of 0.28 Wh g(-1), the power density of 100 kW g(-1) is obtained. The electrode has a series resistance of 10.51 omega and a charge transfer resistance of 1.12 ohm.
Electrochemical characterization of leached steel-making sludge
(Springer Nature, 2022) Langová, Šárka; Kostura, Bruno; Raška, Pavel; Matýsek, Dalibor; Novák, Vlastimil; Ritz, Michal; Krčmář, Jiří
In this work, the electrochemical properties of the leached sludge, magnetite and zinc ferrite were studied. Acetic acid was used as a leaching reagent because, in recent years, there has been a surge of interest in using zinc-containing materials as photocatalysts, with acetic acid finding application in their preparation. Various methodological approaches were used, but the best results were achieved with a combination of 1-3 h leaching in 0.01 M acetic acid with a solid/liquid ratio of 500. In this arrangement, zincite was almost completely removed from the sludge, while zinc ferrite and magnetite remained in the solid residue. Ex situ analyses of the main leaching products were performed by X-ray diffraction, infrared spectroscopy, and thermogravimetry. The electrochemical behaviour of solid residue and model systems, that are micromagnetite and zinc ferrite, was studied in alkaline media by means of modified carbon paste electrodes, cyclic voltammetry, and chronocoulometry, with a suitable potential window ranging from 0 to 1.5 V. In summary, a linear dependence of the anodic and cathodic peak height on the square root of the scan rate was found. The position of the anodic and cathodic peaks shifted slightly with scan rate, only at low rates, up to 25 mV/s, the individual peaks coincided. The electrochemical response suggested a quasireversible process.
Removal of amoxicillin and ampicillin using manganese dioxide/montmorillonite composite
(Wiley, 2022) Valovičová, Věra; Plevová, Eva; Vallová, Silvie; Vaculíková, Lenka; Smýkalová, Aneta; Napruszewska, Bogna D.; Serwicka, Ewa M.; Dolinská, Silvia
BACKGROUND Clay-based materials represent great potential for the development of efficient and environmentally friendly sorbents. The study focuses on a laboratory-obtained manganese dioxide/montmorillonite (MnO2/MMT) composite for removal of two types of antibiotics - amoxicillin (AMX) and ampicillin (AMP) - from aqueous solution. RESULTS The composite was successfully prepared using a reduction procedure involving the reaction between potassium permanganate (KMnO4) and hydrochloric acid (HCl) to form MnO2 followed by the addition of MMT. X-ray analysis, scanning electron microscopy, X-ray fluorescence and Fourier transform infrared spectroscopy were performed for characterization of physicochemical and structural properties, simultaneous thermogravimetry and differential scanning calorimetry for estimation of thermal stability and high-performance liquid chromatography for determination of antibiotic equilibrium concentrations in aqueous solution. The precipitated MnO2 component, manifested by long fibers, corresponded to the tunnel structure of cryptomelane. In the case of MnO2/MMT it is evident that MnO2 developed short fibers with the participation of the MMT matrix. The thermal data suggested that the MnO2 phase upon contact with the clay support showed better thermal stability. The final decomposition of Mn2O3 was shifted to higher temperature of 985 degrees C. Adsorption procedure in a batch regimen showed sufficient sorption ability for both antibiotics with over 90% efficiency. For AMP the value of q(max) was about 45 mg g(-1) and for AMX it was only 21 mg g(-1). CONCLUSIONS The results provided valuable information for the design of a potentially inexpensive clay-based adsorbent and demonstrated the removal of two types of broad-spectrum beta-lactam antibiotics from aqueous solution to a sufficient degree.
Solution combustion synthesis of a nanometer-scale Co3O4 anode material for Li-ion batteries
(Beilstein-Institut, 2021) Michalska, Monika; Xu, Huajun; Shan, Qingmin; Zhang, Shiqiang; Dall'Agnese, Yohan; Gao, Yu; Jain, Amrita; Krajewski, Marcin
A novel solution combustion synthesis of nanoscale spinel-structured Co3O4 powder was proposed in this work. The obtained material was composed of loosely arranged nanoparticles whose average diameter was about 36 nm. The as-prepared cobalt oxide powder was also tested as the anode material for Li-ion batteries and revealed specific capacities of 1060 and 533 mAh.g(-1) after 100 cycles at charge-discharge current densities of 100 and 500 mA.g(-1), respectively. Moreover, electrochemical measurements indicate that even though the synthesized nanomaterial possesses a low active surface area, it exhibits a relatively high specific capacity measured at 100 mA.g(-1) after 100 cycles and a quite good rate capability at current densities between 50 and 5000 mA.g(-1).
The influence of structural properties on the adsorption capacities of microwave-assisted biochars for metazachlor removal from aqueous solutions
(Elsevier, 2022) Bednárek, Jan; Matějová, Lenka; Jankovská, Zuzana; Vaštyl, Michal; Sokolová, Barbora; Peikertová, Pavlína; Šiler, Pavel; Verner, Adam; Tokarský, Jonáš; Koutník, Ivan; Šváb, Marek; Vráblová, Martina
Biochars, carbonaceous materials prepared without the usage of chemical agents, are porous materials capable of adsorbing pollutants from ground-and surface waters. In this study, biochars prepared from various types of agricultural biomass were tested for the adsorptive removal of herbicide metazachlor from an aqueous environment. Banana wastes, red mombin seeds, corncob, cocoa pod husk, and coffee husk were used as precursors. Biochars were prepared with the aid of microwave treatment. The effect of precursor type on structure and adsorption was examined. Adsorption was controlled by a multistep mechanism, adsorption kinetics followed predominantly the pseudo-second-order model, adsorption isotherms suited to both Langmuir and Freundlich isotherms, depending on the particular biochar. Significant differences between the structural properties and adsorption capacities of the examined biochars were observed. The best adsorption properties for metazachlor uptake were observed for banana waste-based biochar, which had large, elongated pores, highest volume of micropores and one of the highest contents of polar functional groups. The maximum adsorption capacity, calculated from Langmuir isotherm, was 146.01 mg.g(-1), The adsorption capacity at equilibrium, obtained by kinetic measurements, was 27.25 mg.g(-1), the kinetic constant was 5.14.10- 3 dm3.min(-1) (both calculated from pseudo-second order model). Molecular modeling revealed that metazachlor molecules preferably entered two layer wide cavities containing one COOH group with their pyrazole rings.
The role of the g-C3N4 precursor on the P doping using HCCP as a source of phosphorus
(Elsevier, 2022) Matějka, Vlastimil; Škuta, Radim; Foniok, Kryštof; Novák, Vlastimil; Cvejn, Daniel; Martaus, Alexandr; Michalska, Monika; Pavlovský, Jiří; Praus, Petr
This work describes the doping of graphitic carbon nitride (g-C3N4) with phosphorus performed by 2-h heat treatment of a mechanical mixture of g-C3N4 precursor (urea, dicyandiamide, and guanidine hydrochloride) with hexachlorocyclotriphosphazene at 525 degrees C. The amount of fixed phosphorus in the resulting g-C3N4 structure reached approximately 10 wt% in the case of the urea precursor. For the other two precursors, the fixed phosphorus content in the final products was less than 5 wt%. Several experimental techniques (SEM, XRFS, TG, XRD, FTIR, physisorption of nitrogen, UV-VIS DRS, PL spectroscopy, and electrochemical analysis) were used to characterize the prepared samples. The photodegradation activity of the samples was determined by degradation of Rhodamine B under irradiation with visible light (420 nm). In general, the photodegradation activity of the samples was dependent on the phosphorus content. The highest photodegradation activity was obtained for urea-based g-C3N4 doped with the lowest phosphorus content, with a threefold increase in calcination product yield. The mechanism of incorporation of phosphorus into the final g-C3N4 structure was explained as a two-phase process.
Photochemical stability of g-C3N4 in the gas phase
(Elsevier, 2022) Paušová, Šárka; Baudys, Michal; Kosina, Jiří; Praus, Petr; Pintar, Albin; Žerjav, Gregor; Roškarič, Matevž; Finšgar, Matjaž; Krýsa, Josef
For the successful environmental applications of g-C3N4 photocatalyst, sufficient photochemical stability is an important parameter. The present work is thus devoted to the investigation of the photostability of g-C3N4 materials in terms of production of organic compounds under UV and VIS light irradiation; for the purpose of comparison, TiO2 material was also investigated. The measurement of total organic compounds in air shows the production of organic compounds when g-C3N4 materials are irradiated with UV or VIS light. Detailed analysis of organic compounds present in the air was performed using GC-MS. When both materials (TiO2 and g-C3N4) were exposed in the dark, the air contained traces of ordinary solvents (acetone, hexane, ethyl acetate). In the case of TiO2, after 1 day of UV irradiation, all organic compounds were removed. Contrary to it, in the case of exfoliated g-C3N4, the concentration of acetone after UV or VIS irradiation increased. The solid-state measurements indicate that after UV/VIS light exposure, there are no changes either in the surface layers or in the bulk of the g-C3N4 photocatalyst. However, based on the observed mass decrease and elemental analysis, the material is oxidised on the surface, and it seems that this surface reaction leads to the disruption of the C-N bonds and the formation of organic compounds, which are released into the atmosphere. But, no compounds containing nitrogen were determined by MS, so nitrogen is most probably released in the form of NOx.
Comparative studies on the dry sliding behavior of a low-metallic friction material with the addition of graphite and exfoliated g-C3N4
(MDPI, 2022) Jayashree, Priyadarshini; Matějka, Vlastimil; Foniok, Kryštof; Straffelini, Giovanni
This study compares the effect of the addition of two types of lubricants on the dry sliding behavior of a simplified Cu-free phenolic resin-based composite material. The lubricants were commercial graphite and exfoliated graphitic carbon nitride (codenamed: TEX6). The graphite particles were rounded and of 'flaky' character. The TEX6 particles were not only flaky, but also irregular in shape, and 'fluffy'. Both lubricants were added individually in the basic formulation and subjected to dry sliding tests on pin-on-disc testing equipment in mild conditions and against a grey cast-iron counterface. The tests with TEX6 observed a stable steady state in the friction coefficient (CoF) with lower scatter and lower average friction coefficient and pin wear magnitude when compared to samples containing graphite. Additionally, the worn surfaces of the TEX6-containing samples had extremely smooth, compact, and continuous secondary plateau coverage when compared to the graphite-containing samples. The counterface paired with the TEX6-containing samples observed much lower abrasive action compared to the graphite-containing samples. Through the wear testing and further evaluation of the secondary plateaus, the possible addition of TEX6 as a lubricant in friction material composition was explained, making it a promising component for automotive braking applications.
Alkali activation of ground granulated blast furnace slag and low calcium fly ash using "one-part" approach
(Springer Nature, 2022) Matějková, Petra; Matějka, Vlastimil; Sabovčík, Tomáš; Gryžbon, Luděk; Vlček, Jozef
The utilization of the solid powder activator for the activation of the ground granulated blast furnace slag (GGBFS) and its mixtures with low calcium fly ash (FA) was tested. Utilizing the activator in a powder form enabled to obtain ready-to-use dry mixtures, which, after the addition of mixing water, molding, and hydration, created compact solid samples. The selected procedure known as "one-part" or "just-add water" approach is beneficial with respect to the traditional two parts approach based on the utilization of the liquid alkali activators. The experiments were subdivided into two parts. The first part was focused on the selection of the solid alkali activator for GGBFS activation. In this stage, two solid powder activators: (i) sodium metasilicate (NS) and (ii) disodium silicate pentahydrate in amounts that carry 2.5, 5, and 7 wt% of Na2O, were tested. The second part was focused on the verification of the suitability of selected solid alkali silicate for the activation of the mixtures of GGBFS with low calcium FA (80:20 and 60:40). The evolution of the compressive strength of the prepared alkali-activated materials was studied after 2, 7, 28, and 56 days of hydration. The raw materials and hydrated samples were examined by XRFS, XRD, FTIR, and SEM techniques. The positive effect of the thermal treatment at 400 degrees C on the compressive strength of the prepared samples was observed. The obtained results indicate the "one-part" method as suitable for the activation of low calcium fly ash in combination with GGBFS.
A brief review of s-triazine graphitic carbon nitride
(Springer Nature, 2022) Praus, Petr
Graphitic carbon nitride (C3N4) has been intensively studied in the last 25 years. Although the number of papers about C3N4 published per year has been growing exponentially, there are still some unclear issues with this material. One of them is s-triazine C3N4 (s-C3N4), which is an allotrope of C3N4. The theoretical computational as well as experimental synthetic results are not unambiguous. The properties of s-C3N4 have been described only in two papers, and no similar and reproducible results have been obtained so far. This paper provides a brief overview of s-C3N4 to bring attention to this material, for example, as a potential photocatalyst.
The role of graphitic carbon nitride in the formulation of copper-free friction composites designed for automotive brake pads
(MDPI, 2022) Matějka, Vlastimil; Leonardi, Mara; Praus, Petr; Straffelini, Giovanni; Gialanella, Stefano
In this study, graphitic carbon nitride (g-C3N4, labelled as gCN) was tested in the formulation of copper-free (Cu-free) friction mixtures, which are potentially interesting for brake pad manufacturing. Three formulations of friction composites were prepared starting from a common Cu-free master batch: (i) without graphite, (ii) with graphite and (iii) with gCN. The mixtures were pressed in the form of pins by hot-press moulding. The friction-wear performance of the prepared pins was investigated using a pin-on-disc (PoD) test at room temperature (RT), high temperature (HT) (400 degrees C) and, again, at room temperature (H-RT). The values of the friction coefficient (mu) for the composites with gCN (or graphite) were as follows: (i) RT test, mu(RT) = 0.52 (0.47); (ii) HT test, mu(HT) = 0.37 (0.37); (iii) RT after the HT tests, mu(H-RT) = 0.49 (0.39). With respect to wear resistance, the samples with graphite performed better than the samples without this solid lubricant. To the best of our knowledge, this is the first report regarding the evaluation of the role of gCN in friction composites designed for automotive brake lining applications. The results indicate the main role of gCN as a soft abrasive.
Graphitic carbon nitride as a platform for the synthesis of silver nanoclusters
(Springer Nature, 2021) Starukh, Halyna; Koštejn, Martin; Matějka, Vlastimil; Praus, Petr
Graphitic carbon nitride (CN) synthetized by the thermal polycondensation of melamine at 550 degrees C for 4 h was further exfoliated by heating at 500 degrees C for 3 h. Silver cations were adsorbed on the exfoliated graphitic carbon nitride (CNE) and then reduced by sodium borohydride forming silver nanoclusters (NCs) with a size of less than 1 nm.The NCs were located on the CNE surface and did not change the CNE properties except for its pore size distribution and thereby specific surface area (SSA).The Ag NCs were able to collect the photoinduced electrons of CNE and thus reduce their recombination with the holes. It was also documented by the increase in the CNE photocatalytic activity in terms of the degradation of antibiotic Ofloxacin.This study demonstrates the ability of CNE to serve as a platform for a simple and fast synthesis of Ag NCs without any stabilizing compounds.
The role of guanidine hydrochloride in graphitic carbon nitride synthesis
(Springer Nature, 2021) Smýkalová, Aneta; Foniok, Kryštof; Cvejn, Daniel; Górecki, Kamil Maciej; Praus, Petr
Graphitic carbon nitride (CN) was synthesized from guanidine hydrochloride (G), melamine (M) and dicyandiamide (DCDA). The CN materials synthetized from the pure precursors and their mixtures were characterized by common methods, including thermal analysis, and their photocatalytic activities were tested by the degradation of selected organic pollutants, such as amoxicillin, phenol, Rhodamine B (RhB). Remarkable changes in their texture properties in terms of particle sizes, specific surface areas (SSA) and consequently their photocatalytic activity were explained by the role of guanidine hydrochloride in their synthesis. The SSA increased due to the release of NH3 and HCl and its complex reactions with melamine and DCDA forming structure imperfections and disruptions. The photocatalytic activity of the CN materials was found to be dependent on their SSA.
Organobeidellites for removal of anti-inflammatory drugs from aqueous solutions
(MDPI, 2021) Plevová, Eva; Vallová, Silvie; Vaculíková, Lenka; Hundáková, Marianna; Gabor, Roman; Smutná, Kateřina; Žebrák, Radim
Diclofenac (DC) and ibuprofen (IBU) are widely prescribed non-steroidal anti-inflammatory drugs, the consumption of which has rapidly increased in recent years. The biodegradability of pharmaceuticals is negligible and their removal efficiency by wastewater treatment is very low. Therefore, the beidelitte (BEI) as unique nanomaterial was modified by the following different surfactants: cetylpyridinium (CP), benzalkonium (BA) and tetradecyltrimethylammonium (TD) bromides. Organobeidellites were tested as potential nanosorbents for analgesics. The organobeidellites were characterized using X-ray powder diffraction (XRD), Infrared spectroscopy (IR), Thermogravimetry and differential thermal analysis (TG/DTA) and scanning microscopy (SEM). The equilibrium concentrations of analgesics in solution were determined using UV-VIS spectroscopy. The intercalation of surfactants into BEI structure was confirmed both using XRD analysis due to an increase in basal spacing from 1.53 to 2.01 nm for BEI_BA and IR by decreasing in the intensities of bands related to the adsorbed water. SEM proved successful in the uploading of surfactants by a rougher and eroded organobeidellite surface. TG/DTA evaluated the decrease in dehydration/dehydroxylation temperatures due to higher hydrophobicity. The Sorption experiments demonstrated a sufficient sorption ability for IBU (55-86%) and an excellent ability for DC (over 90%). The maximum adsorption capacity was found for BEI_BA-DC (49.02 mg & BULL;g(-1)). The adsorption according to surfactant type follows the order BEI_BA > BEI_TD > BEI_CP.
Surface plasmon resonance: An innovative method for studying water permeability of plant cuticles
(Elsevier, 2021) Vráblová, Martina; Marková, Dominika; Vrábl, Daniel; Koutník, Ivan; Sokolová, Barbora; Hronková, Marie
The cuticle forms an effective barrier protecting plants from water loss. Its permeability to water and other compounds significantly differs between species, types of cuticle (stomatous, astomatous), and can be affected by a wide variety of ambient conditions. Enzymatic isolation of the leaf cuticle allows obtaining intact cuticles for permeability measurements. However, the most available gravimetric method, which is used for the assessment of water permeability of isolated cuticles, requires a relatively large area of the cuticle and does not allow the determination of membrane heterogeneity. We propose a new method for the determination of water permeance based on an on-line detection of water flux from a liquid phase to the atmosphere through isolated leaf cuticles in semi-flow chambers. This approach is new in using the phenomenon of surface plasmon resonance for the detection of the liquid phase refractive index affected by water vapor. Isolated cuticles of the leaves of Ficus elastica and an artificial polyethersulfone membrane were used for method evaluation. The composition of cuticular wax and its influence on cuticular permeability was also studied. It has been confirmed that the application of the surface plasmon resonance principle can be used for the assessment of leaf cuticle water permeability and heterogeneity.
Distribution of As within magnetic and non-magnetic fractions of fluidized-bed coal combustion ash
(MDPI, 2021) Kovár, Filip; Bartoňová, Lucie
Separation of coal ash into magnetic and non-magnetic fractions facilitates their utilization when processed separately. Due to desulphurization additives added to coal during the fluidised-bed combustion, non-magnetic fractions often contain elevated CaO levels (while magnetic concentrates are typically rich in Fe2O3). Both CaO and Fe2O3 are known for their ability to bind As during the combustion, whose distribution is a crucial parameter in terms of proper utilization of these fractions. Therefore, the study deals with the As partitioning within magnetic and non-magnetic fractions of fluidized-bed coal combustion ashes. Two different (successive) procedures of dry magnetic separation were used to separate each ash into strongly magnetic, less magnetic, and a non-magnetic fraction. Due to their optimal utilization, the concentrations of As and other target elements in these fractions were evaluated and compared. Magnetic concentrates from the first separation step (in vibrofluidized state) contained 60-70% Fe2O3, magnetic concentrates separated manually out of the residues after the first separation contained 26-41% Fe2O3, and the non-magnetic residues contained 2.4-3.5% Fe2O3. Arsenic levels were the highest in the non-magnetic residues and gradually decreased with the increasing Fe2O3 content in the magnetic fractions. The dominant As association in the studied samples was to CaO (r = +0.909) and with SO3 (r = +0.906) whereas its joint occurrence with Fe2O3 was improbable (r = -0.834).
Uptake of phosphates from water solutions on metallurgical sludge
(Wroclaw University of Technology. Department of Environmental Engineering, 2021) Kostura, Bruno; Huczala, Radim; Klika, Zdeněk; Ritz, Michal; Bartoňová, Lucie; Matýsek, Dalibor
Steel-making dust slurry (SS) and convertor dust slurry (CS) were tested for uptake of phosphates from aqueous solutions. The adsorption of phosphates on SS and CS corresponded well with both Langmuir and Freundlich adsorption isotherms, which indicated the combination of physical and chemical processes. The maximum adsorbed amount of phosphates on both dust slurry samples was ca. 11 mg P/g. The study evaluates also the effect of acidic leaching on the retention characteristics of both dust slurry samples. From the slurry samples prepared by acidic leaching, the leached convertor dust slurry (CSL) was the only sample capable to retain phosphates. To reveal the retention mechanisms of phosphates, the original and leached dust slurry samples were analyzed by IR and Raman spectroscopy. Co-precipitation of Ca and Fe phosphates, or surface complexation of phosphates were evaluated as the retention mechanisms of CS and CSL while the retention of phosphates by zincite in the case of SS is probably based on their adsorption.
Inhibition of steel corrosion with imidazolium-based compounds – Experimental and theoretical study
(Elsevier, 2021) Legut, Dominik; Kadzielawa, Andrzej Piotr; Pánek, Petr; Marková, Kristýna; Váňová, Petra; Konečná, Kateřina; Langová, Šárka
This work aims to investigate the corrosion inhibition of the mild steel in the 1 M HCl solution by 1-octyl-3-methylimidazolium hydrogen sulphate 1-butyl-3-methylimidazolium hydrogen sulphate, and 1-octyl-3-methylimidazolium chloride, using electrochemical, weight loss, and surface analysis methods as well as the full quantummechanical treatment. Polarization measurements prove that studied compounds are mixed-type inhibitors with a predominantly anodic reaction. The inhibition efficiency obtained from the polarization curves is about 80-92% for all of the 1-octyl-3-methylimidazolium salts with a concentration higher than 0.005 mol/l, while it is much lower for 1-butyl-3-methylimidazolium hydrogen sulphate. The values measured in the weight loss experiments (after seven days) are to some extent higher (reaching up to 98% efficiency). Furthermore, we have shown that the influence of the alkyl chain length on the inhibition efficiency is much larger than that of the anion type. Furthermore, we obtain a realistic model of a single molecule on iron surface Fe(110) by applying the Density Functional Theory calculations. We use the state-of-the-art computational approach, including the meta-GGA strongly-constrained and appropriately normed semilocal density functional to model the electronic structure properties of both free and bounded-to-surface molecules of 1-butyl-, 1-hexyl-, and 1-octyl-3-methylimizadolium bromide, chloride, and hydrogen sulphate. From the calculations we extract, the HOMO/LUMO gap, hardness, electronegativity, and charge transfer of electrons from/to molecules-in-question. It supports the experimental findings and explains the influence of the alkyl chain length and the functional group on the inhibition process.
Ultrafine-grained W-Cr composite prepared by controlled W-Cr solid solution decomposition
(Elsevier, 2021) Veverka, Jakub; Lukáč, František; Kądzielawa, Andrzej P.; Koller, Martin; Chlup, Zdeněk; Hadraba, Hynek; Karlík, Miroslav; Legut, Dominik; Vontorová, Jiřina; Chráska, Tomáš; Vilémová, Monika
The application of non-equilibrium methods such as Mechanical Alloying and Field Assisted Sintering enables the formation of a single solid solution in immiscible systems, or the ones characterized by a miscibility gap. This work shows that W-Cr solid solution can be used as an intermediate step to produce ultrafine-grained composite alloys with rod-like microstructural features. It is shown that a significant increase in strength can be achieved without an increase in hardness using this top-down material design.
Solidification microstructures of multielement carbides in the high entropy Zr-Nb-Hf-Ta-Cx system produced by arc melting
(Elsevier, 2021) Biesuz, Mattia; Saunders, Theo G.; Veverka, Jakub; Bortoloti, Mauro; Vontorová, Jiřina; Vilémová, Monika; Reece, Michael J.
Multielement, high entropy carbides are a new class of refractory materials typically manufactured by solid-state synthesis. Although high entropy alloys are usually produced by solidification of a melt, the solidification of high entropy carbides has not been investigated to date. Herein, we report the first arc melting study of the solidification microstructures of the Zr-Nb-Hf-Ta-C-x system. The results highlight the presence of elemental segregation in interdendritic regions whose composition depends on the carbon load (i.e., the composition of the primary solidification phase changes with the amount of carbon in the melt). Duplex microstructures containing two distinct multielement carbides, possessing hardness as high as 30 GPa, are obtained. Interestingly, under certain conditions, there is a perfect "crystallographic continuity"(no grain boundaries and cell parameter variations) between the two phases, though their composition differs. Arc melting produces new and exotic microstructures not observed in materials processed in the solid state.

Browse

Recent Submissions