Publikační činnost Katedry fyzikální chemie a teorie technologických procesů / Publications of Department of Physical Chemistry and Theory of Technological Processes (619)

Permanent URI for this collectionhttp://hdl.handle.net/10084/64744

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry fyzikální chemie a teorie technologických procesů (619) 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.

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Now showing 1 - 20 out of 146 results

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.
Size-resolved, quantitative evaluation of the magnetic mineralogy of airborne brake-wear particulate emissions
(Elsevier, 2021) Gonet, Tomasz; Maher, Barbara A.; Nyirő-Kósa, Ilona; Pósfai, Mihály; Vaculík, Miroslav; Kukutschová, Jana
Exposure to particulate air pollution has been associated with a variety of respiratory, cardiovascular and neurological problems, resulting in increased morbidity and mortality worldwide. Brake-wear emissions are one of the major sources of metal-rich airborne particulate pollution in roadside environments. Of potentially bioreactive metals, Fe (especially in its ferrous form, Fe2+) might play a specific role in both neurological and cardiovascular impairments. Here, we collected brake-wear particulate emissions using a full-scale brake dynamometer, and used a combination of magnetic measurements and electron microscopy to make quantitative evaluation of the magnetic composition and particle size of airborne emissions originating from passenger car brake systems. Our results show that the concentrations of Fe-rich magnetic grains in airborne brake-wear emissions are very high (i.e., -100-10,000 x higher), compared to other types of particulate pollutants produced in most urban environments. From magnetic component analysis, the average magnetite mass concentration in total PM10 of brake emissions is -20.2 wt% and metallic Fe -1.6 wt%. Most brake-wear airborne particles (>99 % of particle number concentration) are smaller than 200 nm. Using low-temperature magnetic measurements, we observed a strong superparamagnetic signal (indicative of ultrafine magnetic particles, < -30 nm) for all of the analysed size fractions of airborne brake-wear particles. Transmission electron microscopy independently shows that even the larger size fractions of airborne brake-wear emissions dominantly comprise agglomerates of ultrafine (<100 nm) particles (UFPs). Such UFPs likely pose a threat to neuronal and cardiovascular health after inhalation and/or ingestion. The observed abundance of ultrafine magnetite particles (estimated to constitute -7.6 wt% of PM0.2) might be especially hazardous to the brain, contributing both to microglial inflammatory action and excess generation of reactive oxygen species.
Polypyrrole/montmorillonite and polypyrrole/ghassoul intercalates as a source of graphite and multi-layer graphene: Preparation of nanocomposites exhibiting strongly anisotropic electrical conductivity
(Elsevier, 2021) Tokarský, Jonáš; Mamulová Kutláková, Kateřina; Peikertová, Pavlína; Řeháčková, Lenka; Kormunda, Martin; Matějková, Petra; Študentová, Soňa; Kulhánková, Lenka
Nanocomposite tablets containing graphite and multi-layer graphene formed from polypyrrole (PPy) in the presence of Na-montmorillonite (Mt) and Moroccan clay ghassoul (Gha) were prepared by the calcination of PPy/Mt and PPy/Gha intercalates in argon at 1300 degrees C. XPS, XRD, Raman, and TEM analyses confirmed that PPy can serve as a precursor of graphite and multi-layer graphene. Although the calcined tablets PPy/Mt(c) and PPy/Gha(c) contain similar to 1/3 of the carbon content compared to a calcined PPy tablet (PPy(c)), the mean values of inplane electrical conductivity (2476 S/m for PPy/Mt(c) and 2289 S/m for PPy/Gha(c)) are higher than 1837 S/m obtained for PPy(c). Strong anisotropy in electrical conductivity (three orders of magnitude) was achieved for PPy/Mt(c) and PPy/Gha(c) tablets. The similar conductivity, as well as density, porosity, and hardness of PPy/Mt (c) and PPy/Gha(c), demonstrate that Mt and Gha in conjunction with PPy are suitable for the preparation of nanocomposites with strongly anisotropic electrical conductivity.
Doping of graphitic carbon nitride with oxygen by means of cyanuric acid: Properties and photocatalytic applications
(Elsevier, 2021) Praus, Petr; Smýkalová, Aneta; Foniok, Kryštof; Novák, Vlastimil; Hrbáč, Jan
Bare and oxygen doped graphitic carbon nitride were synthetized by the thermal polymerization of melamine (CN-M) and the mechanical mixtures of melamine and cyanuric acid, respectively, at 550 degrees C for 4 h. The ratios of melamine and cyanuric acid were 1:0.5, 1:1 and 1:2 (CN-MCA1, CN-MCA2 and CN-MCA3). The content of oxygen increased from 1.88 wt% (CN-M) to 3.93 wt% (CN-MCA3) and the specific surface area increased from 14 to 41 m(2) g(-1). The prepared CN materials were characterized by the elemental analysis, UV-Vis diffuse reflectance, X-ray diffraction, Fourier transform infrared spectrometry, the physisorption of nitrogen, scanning electron and high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, the determination of zeta potentials, and the Mott-Schottky method. The addition of cyanuric acid led to partial changes in the CN morphology, as documented by occurrence of CN tubes, increase in the specific surface area and was a source of additional -O- and -OH moieties which modified the CN surface in addition to the spontaneous oxygenation observed in CN-M. The above effects positively influenced photocatalytic activity of the CN materials as demonstrated using Rhodamine B (RhB) and the Ofloxacin antibiotics. The photocatalytic decomposition of Ofloxacin was more efficient than that of RhB and differed in kinetics (first-order vs. zero-order reaction). The reusability and stability of the CN materials was verified by repeating batch photocatalytic decompositions of Ofloxacin experiments for five times.
On P-doping of graphitic carbon nitride with hexachlorotriphosphazene as a source of phosphorus
(Elsevier, 2021) Škuta, Radim; Matějka, Vlastimil; Foniok, Kryštof; Smýkalová, Aneta; Cvejn, Daniel; Gabor, Roman; Kormunda, Martin; Smetana, Bedřich; Novák, Vlastimil; Praus, Petr
The synthesis of P-doped graphitic carbon nitride (PCN) by in situ doping via co-pyrolysis of melamine and hexachlorocyclotriphosphazene (HCCP) is being investigated. The amount of HCCP varies between 2 and 40 wt% and the results show continuous enrichment of graphitic carbon nitride (CN) by phosphorus. The detailed characterization of prepared samples leads to the proposition of the occurrence of phosphorus in synthesized samples as well as to the proposition of a P-doping mechanism. The results of the characterization techniques used indicate that with up to 1.2 wt% of phosphorus in final PCN, phosphorus predominantly substitutes carbon in the structure. An increase of the phosphorus content to 2.44 wt% causes its incorporation into substitutional positions and part of the phosphorus occurs in other forms. PCN with 2.44 wt% of phosphorus obtained from the mixture of melamine with 20 wt% of HCCP thermally treated at 525 ?C shows the highest photodegradation activity under VIS irradiation.
On the constitution and thermodynamic modeling of the phase diagrams Nb-Mn and Ta-Mn
(Elsevier, 2021) Yan, Xinlin; Brož, Pavel; Vřešťál, Jan; Vlach, Jiří; Buršík, Jiří; Mazalová, Martina; Pavlů, Jana; Smetana, Bedřich; Rogl, Gerda; Eiberger, Markus; Grytsiv, Andriy; Michor, Herwig; Müller, Herbert; Giester, Gerald; Rogl, Peter
The constitution of the two phase diagrams Nb-Mn and Ta-Mn has been determined from light optical and transmission and scanning electron microscopy (LOM, TEM and SEM) with energy dispersive (EDX) as well as wavelength dispersive (WDX) X-ray spectroscopy, X-ray powder (XPD) and single crystal diffraction (XSCD), differential thermal analysis (DTA) and/or differential scanning calorimetry (DSC). The Laves phases NbMn2 and TaMn2 are the only binary compounds in these systems. High-temperature differential thermal analyses revealed congruent melting for NbMn2 with T,(NbMn2) = 1515 +/- 15 degrees C, whereas TaMn2 melts incongruently with T-m(TaMn2)= 1797 +/- 40 degrees C close to a depleted peritectic reaction. Both Laves phases engage in eutectic reactions l <-> (Mn) + Nb(Ta)Mn-2 (T-eut = 1220 +/- 10 degrees C at 4.9 at% Nb and T-eut = 1234 +/- 10 degrees C at 0.7 at% Ta, respectively). NbMn2 also forms a eutectic with (Nb): l <-> (Nb) + NbMn2 at T-eut = 1493 +/- 15 degrees C and 53.2 at% Nb. Mn shows remarkably large maximum solid solubilities of 19.4 at% Mn in (Nb) as well as of 21.3 at% Mn in (Ta). Detailed atom site distribution has been established for the Laves phases by means of temperature dependent X-ray single crystal data (both C14 - MgZn2-type). Combined data from XPD, EDX/WDX and SEM microstructure indicate that for both Laves phases extended homogeneity regions exist: Nb1+xMn2+x (62.5-73.0 at% Mn at 950 degrees C: -0.19 <= x <= 1.125) and Ta1+xMn2-x (59.5-68.5 at % Mn: -0.055 <= x <= 1.215). Density functional theory (DFT) calculations favor Nb(Ta)/Mn antisite occupation rather than defects. The phases, "NbMn" and "TaMn", adopted earlier in the literature as binary system inherent compounds, were shown (TEM, WDX electron microprobe data and X-ray Rietveld refinements) to be oxygen stabilized phases of the Ti4Ni2O type (so-called eta(eta)-phases) with modified Nb(Ta)/Mn site substitution to comply with the formula Nb(Ta)(3-x)Mn3+xO1-y (defect eta-W3Fe3C-type). From magnetic susceptibility and magnetization measurements, both oxide stabilized eta phases eta-Nb3Mn3O1-y and eta-Ta3Mn3O1-y were found to order ferromagnetically below T-c similar to 77 K, but the Laves phases NbMn2, TaMn2 reveal weakly temperature dependent paramagnetism. No trace of the rhombohedral kyphase (W6Fe7-type) has been encountered in our investigation of the two binary phase diagrams. Thermodynamic and transport properties (specific heat, electrical resistivity and magnetic susceptibility/magnetization) classify the Laves phases with metallic behavior whilst mechanical properties (elastic moduli from DFT and nanoindentation as well as hardness and thermal expansion) group both Laves phases among rather hard and brittle intermetallics. Based on (i) the experimentally derived constitution of the Nb-Mn and Ta-Mn systems, and (ii) on new own DFT data of the energy of formation of the Laves phases, a CALPHAD (CALculation of PHAse Diagrams) calculation of both systems was made providing a complete set of optimized thermodynamic data. Furthermore, the DFT calculations provided information on the instability of the eta-Ta3Mn3 structure and the atom-site specific stabilization effect of oxygen.
High–temperature interaction of molten Fe–C–O–Cr alloys with corundum
(Elsevier, 2021) Řeháčková, Lenka; Novák, Vlastimil; Váňová, Petra; Matýsek, Dalibor; Konečná, Kateřina; Smetana, Bedřich; Dobrovská, Jana
The interaction of Fe-C-O-Cr alloys varying in chromium (0.924-4.760 wt%) and carbon (0.042-1.378 wt%) content with a ceramic substrate having a high content of Al2O3 was studied by experimental wettability tests up to 1600 degrees C. The degree of interaction was assessed based on changes in contact angles (wetting angles) between the above systems, and through Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) analyses and Scanning Electron Microscopy (SEM). The increasing trend of wetting angles with increasing content of chromium and carbon was found. The results of the analyzes confirmed the effect of carbon (>0.1 wt%) contained in the alloys on the structural changes in substrate surface within the area under the alloy. The original corundum phase was replaced by new ones (hibonite, grossite, larnite), of which hibonite was present to the highest degree. Furthermore, in the case of low carbon alloy (0.042 wt% C), hibonite was not detected on the substrate surface contrary to chromium-doped corundum.
Investigation of Fe–C–Cr and Fe–C–Cr–Ni-based systems with the use of DTA and HT-LSCM methods
(Springer Nature, 2020) Drozdová, Ľubomíra; Smetana, Bedřich; Presoly, Peter; Novák, Vlastimil; Machů, Mario; Bernhard, Michael; Francová, Hana; Zlá, Simona; Řeháčková, Lenka; Bernhard, Christian
Three Fe-C-Cr and three Fe-C-Cr-Ni-based alloys containing carbon between 0.318 and 0.410 mass%, chromium and nickel between of 0.001 and 4.990 mass% were studied. Original temperatures of solidus, liquidus and peritectic transformation were determined and clarified for all six specific alloys. Phase transition temperatures were experimentally obtained using differential thermal analysis (DTA), and the start of melting of alloys was investigated using the high-temperature laser scanning confocal microscopy. Additionally, experimental data were compared and discussed with calculation results using SW IDS and Thermo-Calc operating with commercially available thermodynamic database TCFE8. The combination of both experimental methods contributed substantially to investigate more clearly the start of melting. Determination of solidus temperatures/incipient melting point temperatures on DTA curves is often challenging, and there are significant differences when compared with the determination of liquidus and peritectic transformation temperatures. HT-LSCM method brings an improvement in that regard because it can reveal thermal events which are hardly identified on DTA curves. The relation between homogeneity/inhomogeneity of investigated alloys and the initiation of their melting was observed depending mainly on the state of alloys.
The presence and effect of oxygen in graphitic carbon nitride synthetized in air and nitrogen atmosphere
(Elsevier, 2020) Praus, Petr; Smýkalová, Aneta; Foniok, Kryštof; Matějka, Vlastimil; Kormunda, Martin; Smetana, Bedřich; Cvejn, Daniel
Two types of bulk graphitic carbon nitrides (CN) were synthetized by heating melamine at 550 degrees C for 4 h in the air (CN/air) and nitrogen (CN/N-2) atmosphere for us to find the effect of present oxygen on their properties. Bulk CN was exfoliated by further heating at 500 degrees C for 1-3 h in air and nitrogen as well. The obtained materials were studied in terms of structural, textural and physico-chemical properties including photocatalytic activity. The CN/air materials contained less oxygen (2.3-5.0 wt%) than the CN/N-2 ones (about 7 wt%) due to decarboxylation during their synthesis and exfoliation in air. The CN/N-2 materials had more structural defects, which were attacked by oxygen from the moment the materials came into contact with air. In both types of materials oxygen was supposed to be present mostly in the form of hydroxyl groups. As a result, the CN/N-2 materials were slightly exfoliated and their surfaces were more hydrophilic than the CN/air ones. The photocatalytic activity of CN materials was dependent on their specific surface area (SSA). It was found that native oxygen existed in the CN materials and was important for their properties.
Surface and interfacial properties of Fe-C-O-Cr alloys in contact with alumina
(Technical Faculty, Bor, 2020) Novák, Vlastimil; Řeháčková, Lenka; Váňová, Petra; Smetana, Bedřich; Konečná, Kateřina; Drozdová, Ľubomíra; Rosypalová, Silvie
In this paper, temperature and concentration dependencies on density and surface tension of liquid Fe-C-O-Cr alloys (1.93 - 4.80 wt.% Cr) were investigated in high-temperature resistance observation furnace by a sessile drop method during heating from liquidus temperature to 1600 degrees C. The interfacial characteristics (interfacial tension, wetting angle, work of adhesion, and spreading coefficient) of liquid alloy/alumina system were also determined depending on temperature. The effect of temperature and chromium content on surface and interfacial properties was proven in case of all examined alloys. Based on the fact that the content of surface-active elements such as oxygen (up to 195 ppm) and sulfur (up to 545 ppm) was higher; the influence of activities of both mentioned elements on surface tension of alloy samples was assessed. Particular attention was paid to the dependence of the surface tension temperature coefficient on oxygen and sulfur activity.
Blending powder process for recycling sintered Nd-Fe-B magnets
(MDPI, 2020) Prokofev, Pavel A.; Kolchugina, Natalia B.; Skotnicová, Kateřina; Burkhanov, Gennadij Sergeevich; Kursa, Miroslav; Zheleznyi, Mark V.; Dormidontov, Nikolay A.; Čegan, Tomáš; Bakulina, Anna S.; Koshkid'ko, Yury S.; Smetana, Bedřich
The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdHx. Composition inhomogeneity in the Nd2Fe14B-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and Nd-depleted (Dy-enriched) shell are demonstrated. The formation of this structure results from the grain boundary diffusion process of Dy that occurs during the sintering of magnets prepared from a mixture of Dy-free (N42) and Dy-containing magnets. The increase in the coercive force of the N42 magnet was shown to be 52%. The simultaneous retention of the remanence, and even its increase, were observed and explained by the improved isolation of the main magnetic phase grains as well as their alignment.
Effect of support on the catalytic activity of Co3O4-Cs deposited on open-cell ceramic foams for N2O decomposition
(Elsevier, 2020) Pacultová, Kateřina; Klegová, Anna; Kiška, Tomáš; Fridrichová, Dagmar; Martaus, Alexandr; Rokicińska, Anna; Kuśtrowski, Piotr; Obalová, Lucie
Cobalt mixed oxide with cesium promoter was deposited on different ceramic open-cell foams (Al2O3 + SiO2, ZrO2 and SiO2 + Al2O3 + C-graphite, Lanik Ltd., Czech Republic) by wet impregnation method. The catalysts were tested for N2O decomposition and characterized by AAS, XRD, TPR-H-2, FTIR, Raman, XPS, SEM and nitrogen adsorption. The same impregnation procedure resulted in different amounts of deposited Co3O4-Cs on each support and different dispersion of Co3O4 and Cs on the surface. The Al2O3 + SiO2 (Al-Si) based ceramic foam was recognized as the most suitable support. The difference in the catalytic activity of unsupported Co3O4 Cs and Co-Cs/Al-Si could be explained in terms of different dispersion levels of individual components on the support, leading to changes in the Cs/Co surface molar ratio of atoms in close contact and subsequent changes in reducibility. Direct correlation of specific rate constant for N2O decomposition and surface Cs/Co molar ratio was found.
Metallurgical preparation of Nb-Al and W-Al intermetallic compounds and characterization of their microstructure and phase transformations by DTA technique
(MDPI, 2020) Čegan, Tomáš; Petlák, Daniel; Skotnicová, Kateřina; Juřica, Jan; Smetana, Bedřich; Zlá, Simona
The possibilities of metallurgical preparation of 40Nb-60Al and 15W-85Al intermetallic compounds (in at.%) by plasma arc melting (PAM) and vacuum induction melting (VIM) were studied. Both methods allow easy preparation of Nb-Al alloys; however, significant evaporation of Al was observed during the melting, which affected the resulting chemical composition. The preparation of W-Al alloys was more problematic because there was no complete re-melting of W during PAM and VIM. However, the combination of PAM and VIM allowed the preparation of W-Al alloy without any non-melted parts. The microstructure of Nb-Al alloys consisted of Nb2Al and NbAl3 intermetallic phases, and W-Al alloys consisted mainly of needle-like WAl4 intermetallic phase and Al matrix. The effects of melting conditions on chemical composition, homogeneity, and microstructure were determined. Differential thermal analysis was used to determine melting and phase transformation temperatures of the prepared alloys.
The relationship between nil-strength temperature, zero strength temperature and solidus temperature of carbon steels
(MDPI, 2020) Kawulok, Petr; Schindler, Ivo; Smetana, Bedřich; Moravec, Jan; Mertová, Andrea; Drozdová, Ľubomíra; Kawulok, Rostislav; Opěla, Petr; Rusz, Stanislav
The nil-strength temperature, zero strength temperature and solidus temperature are significant parameters with respect to the processes of melting, casting and welding steels. With the use of physical tests performed on the universal plastometer Gleeble 3800 and calculations in the IDS software, the nil-strength temperatures, zero strength temperatures and solidus temperatures of nine non-alloy carbon steels have been determined. Apart from that, solidus temperatures were also calculated by the use of four equations expressing a mathematical relation of this temperature to the chemical composition of the investigated steels. The nil-strength and zero strength temperatures and the solidus temperatures decreased with increasing carbon content in the investigated steels. Much higher content of sulfur in free-cutting steel resulted in a decrease of all the temperatures investigated. The zero strength temperatures determined by calculation in the IDS software during solidification were approximately 43-85 degrees C higher than the nil-strength temperatures determined experimentally during heating of the investigated steels. The linear dependence of experimentally measured nil-strength temperature on the calculated zero strength temperature for the investigated steels was determined. Based on regression analyses, there were determined mathematical relations which described with high accuracy a linear dependence of the nil-strength and zero strength temperatures on the solidus temperature of the investigated steels.
Adsorption of nerve agent simulants onto vermiculite structure: Experiments and modelling
(Elsevier, 2020) Plachá, Daniela; Kovář, Petr; Vaněk, Jakub; Mikeska, Marcel; Škrlová, Kateřina; Dutko, Ondřej; Řeháčková, Lenka; Slabotínský, Jiří
Chemical warfare agents are still a threat to humanity despite the existence of a ban on their production and use. There are many new materials that have been experimentally verified to be effective in degrading and eliminating various chemical warfare agents; however, clay minerals still remain very effective, environmentally friendly and not expensive. Vermiculites modified with hexadecylpyridinium, hexadecyltrimethylammonium and tetramethylammonium cations were used for static sorption of vapours of two simulants of nerve agents: dimethyl methyl phosphonate and diethyl ethyl phosphonate. The materials before and after sorption were characterized using infrared spectroscopy, X-ray diffraction and carbon phase analysis. The breakthrough time and capture of simulants were measured using dynamic sorption test. Molecular modelling was used to confirm the experimental results and provide a deeper insight into the structure of the materials and sorption processes.
Degradation of ammonia from gas stream by advanced oxidation processes
(Taylor & Francis, 2019) Kočí, Kamila; Reli, Martin; Troppová, Ivana; Prostějovský, Tomáš; Žebrák, Radim
The reduction of ammonia emissions from air was experimentally investigated by advanced oxidation processes (AOPs) utilizing the combination of ultraviolet irradiation with ozone. The influence of operating conditions such as initial ammonia concentration and flow rate of gas on the reduction of ammonia concentration was investigated in homemade photochemical unit. The conversion of ammonia decreased with increasing initial concentration of ammonia and with increasing flow rate of air (decreasing retention time). The highest conversion of ammonia (97%) was achieved under lower initial concentration of ammonia (30 ppm) and lower flow rate of air (28 m(3)/h). The energy per order was evaluated for the advanced oxidation process too. The energy consumption was about 0.037 kWh/m(3)/order for the 97% ammonia conversion at 30 ppm of initial ammonia concentration and 28 m(3)/h flow rate of air. Based on the results, the advanced oxidation process combining the UV irradiation and ozone was effective for mitigation of ammonia concentration and presents a promising technology for the reduction of odor emissions from livestock buildings. Moreover, the AOPs are suitable for application for high flow rate of air, especially for ammonia abatement from livestock buildings, where very high efficiency is expected.
Fabrication of highly stable CdS/g-C3N4 composite for enhanced photocatalytic degradation of RhB and reduction of CO2
(Springer, 2019) Li, Xin; Edelmannová, Miroslava; Huo, Pengwei; Kočí, Kamila
CdS/g-C3N4 (CdS/CN) type II heterojunction photocatalyst was prepared by an improved successive ionic layer adsorption and reaction process. TEM results show that the CdS nanoparticles (CdS NPs) were successfully loaded on the surface of CN. The results of PL and PEC display that the construction of CdS/CN heterojunction benefits the transmission of the photogenerated carriers and effectively inhibits the photogenerated carrier recombination in photocatalytic process. The photodegradation experiments exhibit that the 3-CdS/CN photocatalyst possesses the highest photodegradation performance over the other samples. The yields of H-2 and CH4, in the presence of the best CdS/CN photocatalyst (1-CdS/CN) are 50 and 13 times stronger, respectively, than in the case of the pure CN in the photoreduction process of CO2. The CN coupling effectively improves the photocatalytic performance of CdS-based photocatalyst and inhibits the hole-induced photocorrosion of CdS NPs. A possible type II heterojunction photocatalytic mechanism has been provided.
Crystallization and quantification of crystalline and non-crystalline phases in kaolin-based cordierites
(MDPI, 2019) Valášková, Marta; Klika, Zdeněk; Novosad, Boris; Smetana, Bedřich
Kaolin is most often used as traditional raw material in ceramic industry. The purpose of the study was to obtain understanding of the structural and chemical variability of cordierite ceramics influenced by chemical and mineralogical properties of six raw kaolins taken from different localities when they are applied in ceramics mixtures with vermiculite and sintered up to 1300 degrees C. The X-ray diffraction and simultaneous thermogravimetric and differential thermal analysis were used to identify and characterize crystalline mineral phases and the course of reactions during the heating. The percentages of the crystalline and non-crystalline phases were newly determined by recalculation of the bulk chemical analyses of kaolins and cordierite ceramics using Chemical Quantitative Mineral Analysis (CQMA) method. Varying amounts of minerals in kaolins: kaolinite from 73.3 to 85.0, muscovite from 4.2 to 9.9, and quartz from 6.0 to 19.5 (mass %) affected amount of cordierite/indialite from 75.2 to 85.1, enstatite from 5.8 to 8.9 (when are calculated as their maximal possible percentages), and non-crystalline phases from 8.8 to 15.1 (mass %) in cordierite ceramics. Regression analysis predicted high relationship between quantity of: (a) kaolinite in kaolins and crystalline cordierite and (b) quartz in kaolins and non-crystalline phases in the ceramics. The migration of potassium from muscovite into the cordierite structure, melting point and crystallization of cordierite/indialite phases and pore size variability in relation to impurity of kaolins are documented and discussed.
The role of fluorine in F-La/TiO2 photocatalysts on photocatalytic decomposition of methanol-water solution
(MDPI, 2019) Edelmannová, Miroslava; Dubnová, Lada; Reli, Martin; Meinhardová, Vendula; Huo, Pengwei; Štangar, Urška Lavrenčič; Čapek, Libor; Kočí, Kamila
F-La/TiO2 photocatalysts were studied in photocatalytic decomposition water-methanol solution. The structural, textural, optical, and electronic properties of F-La/TiO2 photocatalysts were studied by combination of X-ray powder diffraction (XRD), nitrogen physisorption, Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), Electrochemical impedance spectroscopy (EIS), and X-ray fluorescence (XPS). The production of hydrogen in the presence of 2.8F-La/TiO2 was nearly up to 3 times higher than in the presence of pure TiO2. The photocatalytic performance of F-La/TiO2 increased with increasing photocurrent response and conductivity originating from the higher amount of fluorine presented in the lattice of TiO2.
Co-Mn-Al mixed oxides promoted by K for direct NO decomposition: Effect of preparation parameters
(MDPI, 2019) Pacultová, Kateřina; Bílková, Tereza; Klegová, Anna; Karásková, Kateřina; Fridrichová, Dagmar; Jirátová, Květa; Kiška, Tomáš; Balabánová, Jana; Koštejn, Martin; Kotarba, Andrzej; Kaspera, Wojciech; Stelmachowski, Paweł; Słowik, Grzegorz; Obalová, Lucie
Fundamental research on direct NO decomposition is still needed for the design of a sufficiently active, stable and selective catalyst. Co-based mixed oxides promoted by alkali metals are promising catalysts for direct NO decomposition, but which parameters play the key role in NO decomposition over mixed oxide catalysts? How do applied preparation conditions affect the obtained catalyst's properties? Co4MnAlOx mixed oxides promoted by potassium calcined at various conditions were tested for direct NO decomposition with the aim to determine their activity, stability and selectivity. The catalysts were prepared by co-precipitation of the corresponding nitrates and subsequently promoted by KNO3. The catalysts were characterized by atomic absorption spectrometry (AAS)/inductive coupled plasma (ICP), X-ray photoelectron spectrometry (XPS), XRD, N-2 physisorption, temperature programmed desorption of CO2 (TPD-CO2), temperature programmed reduction by hydrogen (TPR-H-2), species-resolved thermal alkali desorption (SR-TAD), work function measurement and STEM. The preparation procedure affects physico-chemical properties of the catalysts, especially those that are associated with the potassium promoter presence. The addition of K is essential for catalytic activity, as it substantially affects the catalyst reducibility and basicity-key properties of a deNO catalyst. However, SR-TAD revealed that potassium migration, redistribution and volatilization are strongly dependent on the catalyst calcination temperature-higher calcination temperature leads to potassium stabilization. It also caused the formation of new phases and thus affected the main properties-S-BET, crystallinity and residual potassium amount.

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