30 results on '"Balázs Réti"'
Search Results
2. Preparing SnO2/MWCNT Nanocomposite Catalysts via High Energy Ball Milling
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Klara Hernadi, Zoltán Németh, Zoltan Pallai, Krisztián Németh, Peter Berki, and Balázs Réti
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Materials science ,Nanocomposite ,Tin dioxide ,Scanning electron microscope ,Biomedical Engineering ,Nanoparticle ,Bioengineering ,General Chemistry ,Carbon nanotube ,Condensed Matter Physics ,law.invention ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,Chemical engineering ,law ,Transmission electron microscopy ,symbols ,General Materials Science ,Raman spectroscopy ,Ball mill - Abstract
Ball milling method was used to fabricate successfully tin dioxide (SnO₂)/multi-walled carbon nanotubes nanocomposite materials using SnCl₂ ×2H₂O as precursor together with soda and salt as admixture. The as-prepared materials were characterized by transmission electron microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, Raman microscopy, and X-ray diffraction techniques. Observations revealed that applying both soda and salt are advantageous for increasing dispersity of tin dioxide nanoparticles on the surface of carbon nanotubes. These multi-walled carbon nanotube-based composites are promising candidates as thick film gas sensors or catalysts. Results indicate that SnO₂/MWCNT composites can be achieved under solvent free dry conditions, too.
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- 2019
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3. The Synthesis and Investigation of SiO2—MgO Coated Multiwalled Carbon Nanotube/Polymer Composites
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Klara Hernadi, Karoly Belina, Balázs Réti, Levente Kovacs, and Krisztián Németh
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010506 paleontology ,Nanotube ,Materials science ,Biomedical Engineering ,Bioengineering ,02 engineering and technology ,General Chemistry ,Carbon nanotube ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Multiwalled carbon ,01 natural sciences ,law.invention ,Chemical engineering ,law ,Polymer composites ,General Materials Science ,0210 nano-technology ,0105 earth and related environmental sciences - Published
- 2017
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4. Carbon sphere templates for TiO 2 hollow structures: Preparation, characterization and photocatalytic activity
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Kornélia Baán, Gabriella Kiss, Balázs Réti, Klara Hernadi, Klára Magyari, and Tamás Gyulavári
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Materials science ,Scanning electron microscope ,Analytical chemistry ,Infrared spectroscopy ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,law.invention ,Thermogravimetry ,symbols.namesake ,Chemical engineering ,Rutile ,law ,Photocatalysis ,symbols ,Crystallization ,0210 nano-technology ,Spectroscopy ,Raman spectroscopy - Abstract
TiO 2 hollow structures (HS) were synthesized by carbon sphere template removal method. Nanometer sized carbon spheres (CS) were prepared by mild hydrothermal treatment of ordinary table sugar (sucrose). The size of these spheres can be controlled by the parameters of the hydrothermal treatment (e.g. time and pH). The obtained CSs were characterized by scanning electron microscopy (SEM), Raman spectroscopy, infrared spectroscopy (IR), X-ray diffraction (XRD) and thermogravimetry (TG). CSs were successfully coated with TiO 2 via sol–gel method. The phase composition of the TiO 2 hollow spheres were controlled by the annealing temperature during crystallization and CSs template removal. TiO 2 hollow structures (HSs) were characterized by SEM, XRD, Raman spectroscopy, TG and energy-dispersive X-ray spectroscopy (EDX). Photocatalytic performance of the TiO 2 HSs was evaluated by phenol degradation in a batch-type foam reactor under low powered UV‐A irradiation. The degradation reaction was followed by high‐performance liquid chromatography (HPLC) and total organic carbon (TOC) measurement techniques. Photocatalytic activity test results pointed out that increased rutile content up to a certain extent (resulting mixed phase anatase-rutile TiO 2 ) effects advantageously the photocatalytic performance of TiO 2 HSs and the unique morphology proved to enhance the photocatalytic activity (six times) as well as TOC removal efficiency (twelve times) compared to the sample which was prepared by the same method without the CSs.
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- 2017
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5. Synthesis and investigation of SiO2-MgO coated MWCNTs and their potential application
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Karoly Belina, Balázs Réti, Klara Hernadi, Krisztián Németh, Balazs Adam, Peter Berki, and Nikolett Varro
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Materials science ,lcsh:Medicine ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Article ,law.invention ,chemistry.chemical_compound ,Differential scanning calorimetry ,law ,Crystallization ,lcsh:Science ,Polypropylene ,chemistry.chemical_classification ,Multidisciplinary ,lcsh:R ,Synthesis and processing ,Polymer ,Polyethylene ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Tetraethyl orthosilicate ,chemistry ,Chemical engineering ,Polyamide ,Nanoparticles ,lcsh:Q ,0210 nano-technology - Abstract
In the present publication, multiwalled carbon nanotubes (MWCNT) coated with SiO2–MgO nanoparticles were successfully fabricated via sol–gel method to facilitate their incorporation into polymer matrices. Magnesium acetate tetrahydrate and tetraethyl orthosilicate were used as precursors. The coated MWCNTs were characterized by transmission electron microscopy (TEM), X–ray diffraction (XRD) and Raman spectroscopy methods. These investigation techniques verified the presence of the inorganic nanoparticles on the surface of MWCNTs. Surface coated MWCNTs were incorporated into polyamide (PA), polyethylene (PE) and polypropylene (PP) matrices via melt blending. Tensile test and differential scanning calorimetry (DSC) investigations were performed on SiO2–MgO/MWCNT polymer composites to study the reinforcement effect on the mechanical and thermal properties of the products. The obtained results indicate that depending on the type of polymer, the nanoparticles differently influenced the Young’s modulus of polymers. Generally, the results demonstrated that polymers treated with SiO2-MgO/MWCNT nanoparticles have higher modulus than neat polymers. DSC results showed that nanoparticles do not change the melting and crystallization behavior of PP significantly. According to the obtained results, coated MWCNTs are promising fillers to enhance mechanical properties of polymers.
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- 2019
6. Utilization of Carbon Nanospheres in Photocatalyst Production: From Composites to Highly Active Hollow Structures
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Zsolt Pap, Klara Hernadi, Tamás Gyulavári, Gábor Veréb, Kornélia Baán, M. Todea, Klára Magyari, Balázs Réti, and Imre Miklós Szilágyi
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Materials science ,Diffuse reflectance infrared fourier transform ,Scanning electron microscope ,Infrared spectroscopy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,lcsh:Technology ,Article ,law.invention ,Crystallinity ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,law ,phenol ,General Materials Science ,Calcination ,composite ,Composite material ,lcsh:Microscopy ,hollow structures ,visible light ,lcsh:QC120-168.85 ,carbon spheres ,lcsh:QH201-278.5 ,lcsh:T ,titanium dioxide ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,lcsh:TA1-2040 ,Titanium dioxide ,Photocatalysis ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,0210 nano-technology ,lcsh:Engineering (General). Civil engineering (General) ,lcsh:TK1-9971 ,photocatalysis - Abstract
Titanium dioxide&ndash, carbon sphere (TiO2&ndash, CS) composites were constructed via using prefabricated carbon spheres as templates. By the removal of template from the TiO2&ndash, CS, TiO2 hollow structures (HS) were synthesized. The CS templates were prepared by the hydrothermal treatment of ordinary table sugar (sucrose). TiO2&ndash, HSs were obtained by removing CSs with calcination. Our own sensitized TiO2 was used for coating the CSs. The structure of the CSs, TiO2&ndash, CS composites, and TiO2&ndash, HSs were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS). The effect of various synthesis parameters (purification method of CSs, precursor quantity, and applied furnace) on the morphology was investigated. The photocatalytic activity was investigated by phenol model pollutant degradation under visible light irradiation (&lambda, >, 400 nm). It was established that the composite samples possess lower crystallinity and photocatalytic activity compared to TiO2 hollow structures. Based on XPS measurements, the carbon content on the surface of the TiO2&ndash, HS exerts an adverse effect on the photocatalytic performance. The synthesis parameters were optimized and the TiO2&ndash, HS specimen having the best absolute and surface normalized photocatalytic efficiency was identified. The superior properties were explained in terms of its unique morphology and surface properties. The stability of this TiO2&ndash, HS was investigated via XRD and SEM measurements after three consecutive phenol degradation tests, and it was found to be highly stable as it entirely retained its crystal phase composition, morphology and photocatalytic activity.
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- 2019
7. Comparative Study of Graphite-Oxide and Graphene-Oxide Supported Proline Organocatalysts in Asymmetric Aldol Addition
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Kornél Szőri, Mihály Bartók, György Szőllősi, Klara Hernadi, and Balázs Réti
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Graphene ,Chemistry ,Enantioselective synthesis ,Oxide ,Graphite oxide ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,Aldol reaction ,law ,Organic chemistry ,Graphite ,0210 nano-technology ,Selectivity - Abstract
Graphite oxide (GrO), graphene oxide (GnO) and their sulphated derivatives (GrOs, GrOo, GnOs, GnOo) were prepared from graphite (Gr) and graphene (Gn) as starting materials, using various methods. Previous experience suggests that in the course of sulphation relatively few functional groups get incorporated, which are mainly located along the edges of the layers. In the course of oxidation the layers are also converted to a significant extent, although aromatic regions are also retained, depending on the strength of the oxidative conditions. Proline impregnation of the functionalized catalyst supports obtained in this way enables the synthesis of Pro-GrO and Pro-GnO chiral catalysts. Proline interacts with the functional groups building up on the layers in a mostly reversible fashion and is relatively easily removed therefrom, whereas over sulphated materials groups forming on the edges allowed stronger bonding of proline. An asymmetric aldol reaction between 2-nitrobenzaldehyde and acetone with a selectivity of 90 % and an enantioselectivity of 77 % can be catalysed using these materials. The catalysts lifetime, however, is still limited at the present stage of our studies. Catalysts prepared from graphenes usually proved to be more active than those prepared from graphite, which was suggested to be due to the accessibility and amount of the functional groups created on the edges of the graphene sheets.
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- 2016
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8. Preparation of TiO2/WO3 composite photocatalysts by the adjustment of the semiconductors' surface charge
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Istvan Szekely, Endre Zsolt Kedves, Peter Berki, Veronica Coșoveanu, Adriana Vulpoi, Eszter Orbán, Zsolt Pap, Lucian Baia, Klára Magyari, Csaba Bolla, Monica Baia, Kata Saszet, Szilvia Fodor, Boglárka Hampel, Klara Hernadi, É. Karácsonyi, András Dombi, Balázs Réti, Alexandra Csavdári, Virginia Danciu, and Gábor Kovács
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Materials science ,Mechanical Engineering ,Composite number ,Inorganic chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Homogeneous distribution ,0104 chemical sciences ,Nanomaterials ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Methyl orange ,Photocatalysis ,Hydrothermal synthesis ,General Materials Science ,Surface charge ,0210 nano-technology ,Photodegradation - Abstract
The present research focused on the preparation of TiO2/WO3 (76/24 wt. %) composite photocatalysts for the photodegradation of methyl orange under UV light. The composites were prepared by the adjustment of the surface charge of the individual semiconductors, achieving a homogeneous distribution of the components within the composite. This resulted in a homogeneous distribution of the components within the composite. The individual WO3 and TiO2 nanocrystals were obtained either by sol–gel or by hydrothermal synthesis. The produced nanomaterials were characterized by using TEM, SEM, XRD and DRS. Major differences in their photocatalytic performance depended on the nature of the precursors and the synthesis pathway.
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- 2016
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9. Segmental nitrogen doping and carboxyl functionalization of multi-walled carbon nanotubes
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Klara Hernadi, Balázs Réti, Krisztián Németh, Zsolt Szegletes, Gergo Peter Szekeres, Anikó Kinka, László Nagy, Melinda Magyar, Erika Varga, and A. Erdöhelyi
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Materials science ,Inorganic chemistry ,technology, industry, and agriculture ,Selective chemistry of single-walled nanotubes ,chemistry.chemical_element ,Carbon nanotube ,Condensed Matter Physics ,Nitrogen ,Electronic, Optical and Magnetic Materials ,law.invention ,symbols.namesake ,chemistry ,X-ray photoelectron spectroscopy ,Transmission electron microscopy ,law ,symbols ,Surface modification ,Raman spectroscopy ,Carbon - Abstract
Partial nitrogen doping was performed during the catalytic chemical vapor deposition (CCVD) synthesis of multi-walled carbon nanotubes. A special reactor was created to facilitate the execution of syntheses with different reaction conditions. The synthesized samples were analyzed by transmission electron microscopy (TEM) in order to provide information about the tubular and nontubular morphology of particles and their deformation gained after the reaction conditions were changed. The incorporation of nitrogen into the carbon structure was studied by X-ray photoelectron spectroscopy (XPS), whereas X-ray diffraction (XRD) and Raman spectroscopy evaluations showed the degree of graphitization. The samples then were carboxyl functionalized in varied concentrations of nitric acid solutions and photosynthetic reaction center protein (RC-26) purified from purple bacteria was linked to the carboxyl groups in order to make the degree of functionalization visible. The protein-linked samples were characterized by atomic force microscopy (AFM). Our experiments indicated that the syntheses carried out in the new reactor were successful and resulted in carbon nanotubes partially doped with nitrogen. TEM studies revealed that the expected deformations are localized only in a defined segment of carbon nanotubes therefore nitrogen doping is most possibly presented there. The nitrogen content in the samples represented in atomic ratios was between 0.9% and 2.9%. The deformations facilitate the functionalization at that certain area, thus the location of carboxyl groups can be determined.
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- 2015
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10. Super growth of vertically aligned carbon nanotubes on pulsed laser deposited catalytic thin films
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Egon Kecsenovity, Dora Fejes, Balázs Réti, Zsolt Toth, Zsuzsanna Pápa, and Klara Hernadi
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Materials science ,Nanotechnology ,General Chemistry ,Carbon nanotube ,law.invention ,Pulsed laser deposition ,Catalysis ,symbols.namesake ,Crystallinity ,Chemical engineering ,law ,symbols ,General Materials Science ,Wafer ,Thin film ,Raman spectroscopy ,Layer (electronics) - Abstract
Efficient and reproducible growth of vertically aligned carbon nanotube (CNT) forests by catalytic chemical vapor deposition (CVD) requires precise setting of the properties of the catalyst thin films and CVD conditions. In this work, super growth of vertically aligned CNTs onto Al2O3 support and Fe–Co catalyst layer system is presented. The layers were grown by pulsed laser deposition (PLD) onto silicon wafer pieces. Their thickness and optical properties were controlled by spectroscopic ellipsometry. The effect of heat treatment at 750 °C in nitrogen and in hydrogen of these PLD layers was compared. High-resolution electron microscopic images showed that treatment of catalyst layers in H2 resulted in finer and denser catalytic particles. As a result, well-aligned, dense and few-walled CNT forests with 1–1.5 mm height were deposited by water-vapor-assisted CVD on the hydrogen-treated films, while without hydrogen treatment defected CNT structures were grown. According to these observations, Raman spectroscopy showed a higher degree of crystallinity in case of CNT-s, where reduction by hydrogen influenced the oxidation state of the metallic catalytic particles in a beneficial way.
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- 2015
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11. Photocatalytic hollow TiO
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Nóra, Justh, László Péter, Bakos, Klára, Hernádi, Gabriella, Kiss, Balázs, Réti, Zoltán, Erdélyi, Bence, Parditka, and Imre Miklós, Szilágyi
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Article - Abstract
Carbon nanospheres (CNSs) were prepared by hydrothermal synthesis, and coated with TiO2 and ZnO nanofilms by atomic layer deposition. Subsequently, through burning out the carbon core templates hollow metal oxide nanospheres were obtained. The substrates, the carbon-metal oxide composites and the hollow nanospheres were characterized with TG/DTA-MS, FTIR, Raman, XRD, SEM-EDX, TEM-SAED and their photocatalytic activity was also investigated. The results indicate that CNSs are not beneficial for photocatalysis, but the crystalline hollow metal oxide nanospheres have considerable photocatalytic activity.
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- 2017
12. Synthesis, Comparative Characterization and Photocatalytic Application of SnO2/MWCNT Nanocomposite Materials
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András Dombi, Zoltán Németh, Kornélia Baán, Gábor Veréb, Zoltan Pallai, Klara Hernadi, Ottó Berkesi, A. Erdöhelyi, L. Forró, Zoltan Imre Balogh, Endre Horváth, and Balázs Réti
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Materials science ,Nanocomposite ,Nanoparticle ,Infrared spectroscopy ,Carbon nanotube ,Hydrothermal circulation ,law.invention ,Solvent ,symbols.namesake ,Chemical engineering ,law ,symbols ,Photocatalysis ,Organic chemistry ,Raman spectroscopy - Abstract
Two different preparation methods were developed to cover successfully multi-walled carbon nanotubes (MWCNT) with tin-dioxide (SnO 2 ) nanoparticles using SnCl 2 I‡2H 2 O as precursor under different solvent conditions. The applied mass ratios of the components were 1:4, 1:8, 1:16, 1:32 and 1:64, respectively. As-prepared tin-dioxide coverages were characterized by TEM, SEM, SEM-EDX, Raman microscopy, BET and X-ray diffraction techniques. Photocatalytic efficiencies of selected composites were investigated in a self-made photoreactor, equipped with UV-A fluorescence lamps. Photocatalytic degradation of phenol solution was followed by using HPLC. Observations revealed that using hydrothermal method we can easily control the layer of SnO 2 nanoparticles on the surface of MWCNTs. Using various solvents SnO 2 nanoparticles with different morphologies formed. The nanocomposites have low photocatalytic efficiencies under conditions used generally (when I»>300 nm).
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- 2014
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13. Chemical challenges during the synthesis of MWCNT-based inorganic nanocomposite materials
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Peter Berki, Klara Hernadi, Endre Horváth, Zoltan Pallai, Arnaud Magrez, Balázs Réti, Zoltán Németh, Judit Major, and László Forró
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Nanocomposite ,Materials science ,Nanoparticle ,Nanotechnology ,Carbon nanotube ,Condensed Matter Physics ,Hydrothermal circulation ,Electronic, Optical and Magnetic Materials ,law.invention ,Solvent ,Metal ,law ,visual_art ,visual_art.visual_art_medium ,High-resolution transmission electron microscopy ,Layer (electronics) - Abstract
Multiwalled carbon nanotubes (MWCNTs) were successfully covered with metal oxides - such as TiO2, ZnO, Al2O3, SnO2, and In2O3 nanoparticles - with different preparation methods under solvent conditions. The applied synthesis techniques were impregnation, a hydrothermal process and a ball-milling method. As-prepared inorganic coverage layers were characterized by TEM, HRTEM, SEM, SEM-EDX, and X-ray diffraction techniques. Results revealed that the choice of synthesis technique affects the quality and the layer structure of the deposited inorganic particles on the surface of carbon nanotubes. These materials might be suitable for nanotechnology applications. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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- 2014
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14. The effect of titania precursor on the morphology of prepared TiO2/MWCNT nanocomposite materials
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Christos Tsakiroglu, Arnaud Magrez, Dora Fejes, Endre Horváth, Ioannis Bountas, Peter Berki, László Forró, Balázs Réti, Katerina Terzi, and Klara Hernadi
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Nanocomposite ,Materials science ,Scanning electron microscope ,Nanotechnology ,Carbon nanotube ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,law ,Specific surface area ,Alkoxide ,Titanium dioxide ,Photocatalysis ,Thermal analysis - Abstract
Since materials science is of great importance, the application of composite materials based on carbon nanotubes (CNTs) is widely investigated. Current work is aimed at preparing nanocomposites of TiO2/MWCNT using an impregnation method combined with slow hydrolysis. Different titanium alkoxide compounds as Ti(OEt)(4), Ti(OiPr)(4), and Ti(OBu)(4), respectively, were used as precursor materials to cover the surface of CNTs in ethanolic medium. In our samples themass ratiowas 10:1 (TiO2:MWCNT). The produced composite materials were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Raman microscopy, transmission (TEM) and scanning electron microscopy (SEM) techniques; moreover, thermal analysis and the determination of the specific surface area (BET) were also carried out. These as-prepared TiO2/MWCNT composites were also tested as photocatalysts in degradation reaction of the model compound salicylic acid. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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- 2014
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15. Substrate dependent photocatalytic performance of TiO2/MWCNT photocatalysts
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Károly Mogyorósi, Klara Hernadi, Balázs Réti, and András Dombi
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Process Chemistry and Technology ,Oxalic acid ,chemistry.chemical_element ,Catalysis ,chemistry.chemical_compound ,symbols.namesake ,Adsorption ,chemistry ,Titanium dioxide ,Photocatalysis ,symbols ,Organic chemistry ,Phenol ,Raman spectroscopy ,Nuclear chemistry ,Titanium - Abstract
Titanium dioxide multiwall carbon nanotube (TiO2/MWCNT) composite photocatalysts were synthesized by the hydrolysis of titanium containing precursor adsorbed on the surface of MWCNT. Annealing was applied to convert amorphous titania oxide-hydroxide to crystalline material. The prepared photocatalysts were characterized with TEM, XRD and Raman spectroscopy. XRD and Raman results showed that only anatase-phase titanium dioxide is present in the samples. Generally this is the preferred phase as it is photocatalytically more active than all other TiO2 phases. TEM investigations revealed that the prepared photocatalysts have well defined structures; the MWCNTs were decorated with TiO2 nanoparticles. The photocatalysts were tested in aqueous-phase photocatalytic reactions using sol–gel prepared TiO2 as references. The choice of model compounds was based on their aromatic and polar characteristics. The concentration of the model compounds (phenol and oxalic acid) was measured by HPLC technique. These investigations showed that photocatalytic activity does depend on the model compound and the percentage of MWCNT content. The sample containing 5% MWCNT was the most efficient for oxalic acid decomposition under UV irradiation while the sample containing 1% MWCNT performed the best in phenol decomposition under our experiment conditions. For both model compounds, there are MWCNTs containing samples which are better than the similar way prepared TiO2 reference samples.
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- 2014
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16. Growth and characterization of bamboo-like carbon nanotubes synthesized on Fe-Co-Cu catalysts prepared by high-energy ball milling
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Klara Hernadi, Dora Fejes, Egon Kecsenovity, and Balázs Réti
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Materials science ,chemistry.chemical_element ,Nanotechnology ,Carbon nanotube ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Catalysis ,chemistry.chemical_compound ,symbols.namesake ,Chemical engineering ,Acetylene ,chemistry ,law ,Transmission electron microscopy ,symbols ,High-resolution transmission electron microscopy ,Raman spectroscopy ,Ball mill ,Carbon - Abstract
Bamboo-like carbon nanotubes (BCNTs) are special nanotubes with unique morphology and properties. Until now BCNTs could be fabricated mostly by nitrogen doping, but the use of nitrogen-containing organic compound is toxic and it makes the synthesis more complicated. Here, we present a simple method for the selective growth of bamboo-like CNTs. We employed high energy ball milling method for preparing Fe–Co–Cu (2.5–2.5–1 wt%) catalysts on Al2O3 support to synthesize bamboo-like CNTs by hydrogen-assisted catalytic chemical vapor deposition (CCVD) from acetylene at 720 °C. The effect of milling time on the growth of bamboo-like CNTs was investigated. Morphology and structure of the carbon deposits were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The growth mechanism of the as-prepared bamboo-like CNTs, and the role of copper containing catalyst were studied. Their properties theoretically make them ideal for gas storage and can be used as matrix fillers in composite materials, where the improved electrical conductivity with the mechanical properties of the tubes are the novel factor. HRTEM image of bamboo-like carbon nanotube (the scalebar is 50 nm).
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- 2013
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17. Preparation of SnO2 -TiO2 /MWCNT nanocomposite photocatalysts with different synthesis parameters
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Klara Hernadi, Balázs Réti, Nóra Péter, and András Dombi
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Materials science ,Nanocomposite ,Precipitation (chemistry) ,Composite number ,Nanoparticle ,Carbon nanotube ,Condensed Matter Physics ,Decomposition ,Electronic, Optical and Magnetic Materials ,Catalysis ,law.invention ,Chemical engineering ,law ,Photocatalysis - Abstract
Photocatalytic activity of TiO2 can be further improved by coupling it with other semiconductors and/or carbon nanotubes (CNTs) and create a composite material. SnO2–TiO2/multiwall carbon nanotube (MWCNT) composite catalysts with different molar ratios were prepared and the photocatalytic activities of these samples were evaluated with methylene blue decomposition. The catalysts were synthesized by acid-catalysed sol–gel method. Two series of catalysts were made, one with co-precipitation and the other one with consecutive precipitation method. The samples were characterized by TEM, XRD, BET techniques, respectively. These investigations revealed that some crystalline oxide nanoparticles were successfully bound onto the surface of MWCNTs. Mainly, the MWCNT containing catalysts showed higher photocatalytic activity, and addition of SnO2 enhances the efficiency of photocatalysts. The composites with the ratio of 25–75 (SnO2–TiO2 mol%) with 10 wt% of MWCNTs showed the best performance in photocatalytic test reactions.
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- 2013
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18. Preparation and characterization of multiwalled carbon nanotube/WO3composite materials
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Klara Hernadi, Adam Vass, Zoltán Németh, Balázs Réti, and Peter Berki
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Nanotube ,Materials science ,Scanning electron microscope ,chemistry.chemical_element ,Tungsten ,Condensed Matter Physics ,Chloride ,Tungsten trioxide ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,law ,medicine ,Photocatalysis ,symbols ,Calcination ,Composite material ,Raman spectroscopy ,medicine.drug - Abstract
Multiwalled carbon nanotube (MWCNT)/tungsten trioxide (WO3) composites were prepared by two different impregnation methods. Tungsten (VI) chloride (WCl6) was chosen as precursor compound to cover the surface of MWCNTs using either a simple or a combined impregnation technique. The applied mass ratio of MWCNT:WO3 was 1:15 for each sample. Two different temperatures (450 and 700 °C) were applied during the calcination process depending on the type of the synthesis method. The produced composite materials and the reference WO3 sample were characterized by transmission and scanning electron microscopies, Raman microscopy, and X-ray diffraction. The results show that using varying both solvents and methods has a significant effect on the formation of composite materials. As prepared MWCNT-based composites are planned to be applied in gas sensing techniques or in photocatalytic processes in the near future.
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- 2013
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19. Titán-dioxid alapú, többfalú szén nanocső tartalmú kompozitok előállítása, jellemzése és fotokatalitikus aktivitásuk vizsgálata
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Balázs Réti
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- 2016
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20. SiO2/MgO coated multiwalled carbon nanotubes in polymer composites
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Balázs Réti, Krisztián Németh, Klara Hernadi, Karoly Belina, and Mark Posa
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Polypropylene ,Diffraction ,Materials science ,Mixing (process engineering) ,Carbon nanotube ,engineering.material ,Condensed Matter Physics ,Multiwalled carbon ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,chemistry ,Coating ,Chemical engineering ,law ,Transmission electron microscopy ,engineering ,Electron microscope - Abstract
The aim of this work was to develop a talc-like inorganic coating on the surface of the multiwalled carbon nanotubes (MWCNTs) to facilitate their mixing into the polypropylene and polyethylene matrix. Precursor compounds such as MgCl2 · 6H2O, Mg(NO3)2 · 6H2O, MgO2C4H10 and tetraethyl-orthosilicate (TEOS) were used to cover the surface of the MWCNTs. As prepared, coverages and polymer composites were characterized by transmission electron microscopy and X-ray diffraction techniques.
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- 2012
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21. Photocatalytic measurements of TiO2/MWCNT catalysts having different surface coverage
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Zoltán Németh, András Erdőhelyi, Károly Mogyorósi, András Dombi, Klara Hernadi, Krisztián Németh, Balázs Réti, and Kata Markó
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Anatase ,Materials science ,Nanocomposite ,chemistry.chemical_element ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Catalysis ,chemistry.chemical_compound ,Adsorption ,chemistry ,Chemical engineering ,Rutile ,Titanium dioxide ,Photocatalysis ,Titanium - Abstract
Photocatalytic oxidation using TiO2 is one way to deal with pollutant compounds. Due to literature data, further improvement can be achieved by using MWCNT-based nanocomposites as photocatalysts. TiO2/multiwall carbon nanotube composite photocatalysts were synthetized by sol–gel method with different level coverages. As-prepared catalysts were characterized with transmission electron microscopy, scanning electron microscopy and X-ray diffraction (XRD). These investigations revealed that we could fabricate MWCNT composite either homogenously, inhomogenously or barely coated with TiO2. XRD results showed that after annealing the amorphous titanium oxide–hydroxide formed anatase phase titanium dioxide which is photocatalytically more active than rutile phase TiO2. Catalysts were tested in both gas and liquid phase photocatalytic reactions using Aeroxide (Degussa) P25 as reference. The concentrations of model compounds were measured by GC and HPLC techniques. As a result of catalytic tests, we have found correlation between morphology and photocatalytic activity. Preferred adsorption of test molecules on MWCNT surface can be a key step of the reaction.
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- 2011
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22. The effect of alkaline doped catalysts on the CVD synthesis of carbon nanotubes
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Klara Hernadi, Krisztián Németh, Dora Fejes, Zoltán Németh, Balázs Réti, and Zoltan Imre Balogh
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inorganic chemicals ,Materials science ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Chemical vapor deposition ,Carbon nanotube ,010402 general chemistry ,01 natural sciences ,Catalysis ,law.invention ,symbols.namesake ,law ,Dopant ,Carbon nanofiber ,technology, industry, and agriculture ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical engineering ,symbols ,Carbon nanotube supported catalyst ,0210 nano-technology ,Raman spectroscopy ,Carbon - Abstract
The aim of this work was to develop new doped catalysts for chemical vapour deposition (CVD) synthesis in order to increase the quantity and quality of carbon nanotubes (CNTs). Doping compounds such as CsBr, CsCl, KBr and KCl were used to reach higher carbon deposit and carbon yield. The amount of the dopant alkali compounds varied from 1 to 5%. As prepared CNTs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman microscopy. Results revealed that both carbon yield and deposit could be increased over doped catalysts.
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- 2011
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23. Preparation of homogeneous titania coatings on the surface of MWNTs
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Klara Hernadi, Jin Won Seo, Ákos Kukovecz, László Forró, Zoltán Németh, Duncan T. L. Alexander, Balázs Réti, and Christel Dieker
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Surface (mathematics) ,Diffraction ,Materials science ,Scanning electron microscope ,Electron energy loss spectroscopy ,Nanotechnology ,Carbon nanotube ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Chemical engineering ,law ,Transmission electron microscopy ,X-ray crystallography ,Electron microscope - Abstract
The aim of this work was to develop a controllable route to produce a stable and inorganic layer on the surface of multi-wall carbon nanotubes. Precursor compounds such as TiBr4, TiCl4, Ti(OiPr)(4), and Ti(OEt)(4) were used to cover the surface of carbon nanotubes (CNTs) under either solvent free or solution conditions. Various titania precursors were compared in the formation of homogeneous layers on the surface of CNTs. As-prepared titania coverages were characterized by transmission electron microscopy (TEM), high resolution TEM, scanning electron microscopy, electron energy loss spectroscopy, and Xray diffraction techniques. Results revealed that homogeneous coverage can be achieved in a controllable way. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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- 2010
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24. Modification of mechanical properties of polymers by SiO2 - MgO coated multiwalled carbon nanotubes
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Attila Bata, Krisztián Németh, Klara Hernadi, Balázs Réti, Karoly Belina, and Andrea Major Adamne
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chemistry.chemical_classification ,Materials science ,Nanoparticle ,Mechanical properties of carbon nanotubes ,Polymer ,Carbon nanotube ,Dynamic mechanical analysis ,Homogeneous distribution ,Nanomaterials ,law.invention ,chemistry ,law ,Composite material ,Tensile testing - Abstract
Multiwalled carbon nanotubes (MWCNTs) feature excellent mechanical properties and for this reason these nanomaterials are suitable candidate for a reinforcement material in the polymer composites. To take full advantage of their outstanding properties, homogeneous distribution needs to be improved in the polymer matrix. In the following study multi-walled carbon nanotubes were coated with SiO2-MgO nanoparticles - to improve the interfacial bonding between the MWCNTs and the matrix - and dispersed in two different polymers. The influence of the coated MWCNTs on mechanical properties was investigated by dynamic mechanical analysis (DMA), and tensile test. We have observed experimentally that mutual chemical connection between the inorganic layer on the MWCNTs and polymer matrix can enhance the properties of the polymers.
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- 2015
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25. Core-shell carbon nanosphere-TiO2composite and hollow TiO2nanospheres prepared by atomic layer deposition
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Nóra Justh, Zoltán Erdélyi, László Péter Bakos, Gabriella Kiss, Bence Parditka, Klara Hernadi, Balázs Réti, and Imre Miklós Szilágyi
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Carbon nanosphere ,History ,Materials science ,Composite number ,chemistry.chemical_element ,Fizikai tudományok ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Computer Science Applications ,Education ,Core shell ,Atomic layer deposition ,Burning out ,Természettudományok ,Coating ,chemistry ,engineering ,Composite material ,Fourier transform infrared spectroscopy ,0210 nano-technology ,Carbon - Abstract
Core-shell carbon-TiO2 composite and hollow TiO2 nanospheres were prepared using carbon nanospheres as hard-templates, coating them with TiO2 using atomic layer deposition, and subsequent burning out of the carbon cores. The bare carbon, the composite carbon-TiO2 and the hollow TiO2 nanospheres were characterized with TG/DTA-MS, FTIR, XRD and SEM-EDX.
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- 2016
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26. Influence of TiO2 phase composition on the photocatalytic activity of TiO2/MWCNT composites prepared by combined sol-gel/hydrothermal method
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Klara Hernadi, Balázs Réti, Arnaud Magrez, Endre Horváth, András Dombi, Tamás Boldizsár, László Forró, Dóra Szarka, and Zoltán Major
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Anatase ,chemistry.chemical_element ,02 engineering and technology ,Material science ,010402 general chemistry ,01 natural sciences ,Catalysis ,Hydrothermal circulation ,Carbon nanotube ,law.invention ,chemistry.chemical_compound ,law ,Specific surface area ,Physical and Theoretical Chemistry ,Crystallization ,Composite material ,Photocatalysis ,Process Chemistry and Technology ,Salicylic acid ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Rutile ,Titanium dioxide ,0210 nano-technology ,Titanium - Abstract
Titanium dioxide/multiwall carbon nanotube (TiO2/MWCNT) composites were prepared by sol-gel method with hydrolysis of titanium alkoxide precursor followed by crystallization via hydrothermal treatment at different acid concentrations. Transmission electron microscopy (TEM) measurements revealed that the acid concentration has serious control over the morphology which is in good agreement with the change of specific surface area. According to the X-ray diffraction analysis of the samples the anatase/rutile ratio of the TiO2 in the composite can be tuned by the manipulation of acid concentration used for the hydrothermal crystallization. Samples were tested in aqueous-phase photocatalytic degradation reaction of salicylic acid in a batch-type foam reactor using relatively low power UV-A irradiation. The change in salicylic acid concentration was monitored by UV-vis spectroscopy technique. Anatase/rutile ratio decreased with increasing acid concentration and photocatalytic performance was decreased with increasing rutile content, however low rutile content (11 wt%) enhanced the photocatalytic efficiency above all prepared samples. (C) 2016 Elsevier B.V. All rights reserved.
27. Fabrication of homogeneous titania/MWNT composite materials
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Zoltán Németh, László Forró, Balázs Réti, Barbara Korbély, Jin Won Seo, Klara Hernadi, and Arnaud Magrez
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Fabrication ,Materials science ,Nanostructure ,Layer ,Interfaces ,Oxide ,chemistry.chemical_element ,02 engineering and technology ,Growth ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Electron microscopy ,General Materials Science ,Composite material ,Composites ,Nanocomposite ,Mechanical Engineering ,Walled Carbon Nanotubes ,Dispersion ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,X-ray diffraction ,chemistry ,Mechanics of Materials ,X-ray crystallography ,Tio2 ,Strength ,0210 nano-technology ,Dispersion (chemistry) ,Layer (electronics) ,Titanium - Abstract
MWNT/titania nanocomposites were prepared by an impregnation method and subsequent heat treatment at 400 degrees C. Precursor compounds such as titanium (IV) propoxide and titanium (IV) ethoxide were used to cover the surface of CNTs under solution conditions. Electron microscopy and X-ray diffraction techniques were carried out to characterize the as-prepared titania layers. (C) 2011 Elsevier Ltd. All rights reserved.
28. Preparation of titania covered multi-walled carbon nanotube thin films
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Arnaud Magrez, Endre Horváth, Zoltán Németh, Peter Berki, László Forró, Klara Hernadi, and Balázs Réti
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Thermogravimetric analysis ,Materials science ,Scanning electron microscope ,Analytical chemistry ,chemistry.chemical_element ,Hydrochloric acid ,Carbon nanotube ,law.invention ,Catalysis ,chemistry.chemical_compound ,symbols.namesake ,law ,lcsh:TA401-492 ,General Materials Science ,Mechanical Engineering ,MWCNT ,Sealed system ,Relative humidity ,chemistry ,Chemical engineering ,Mechanics of Materials ,SEM ,Raman spectroscopy ,symbols ,lcsh:Materials of engineering and construction. Mechanics of materials ,Desiccator ,Titanium - Abstract
The aim of this work was to investigate the effects of relative humidity on the formation of titania layers on the surface of multi-walled carbon nanotubes under regulated conditions in a sealed system. Reactive precursor compounds such as titanium (IV) oxychloride hydrochloric acid and titanium (IV) bromide were used as precursor to cover the surface of multi-walled carbon nanotubes (MWCNTs) under solvent conditions. The mixtures of MWCNTs and titania compounds were not stirred or sonicated. The effect of relative humidity was influenced using the mixture of sulphuric acid and water in desiccators. As-prepared titan-dioxide (TiO2) layers were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TG), X-ray diffraction (XRD) and Raman spectroscopy. Our results revealed that TiO2 layers with different thicknesses can be obtained using this simple sealed system. These TiO2 covered multi-walled carbon nanotube films can be ideal candidates for different kinds of applications (e.g. sensors, virus filtration or catalysts). Keywords: MWCNT, Sealed system, Relative humidity, SEM, Raman spectroscopy
29. Controlling the Structure of Carbon Deposit by Nitrogen Doping Catalytic Chemical Vapor Deposition Synthesis
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Dora Fejes, Gergő Péter Szekeres, László Forró, Jung Woo T. Seo, Krisztián Németh, Balázs Réti, and Klara Hernadi
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Materials science ,Catalyst support ,growth ,Inorganic chemistry ,Biomedical Engineering ,chemistry.chemical_element ,Bioengineering ,Carbon nanotube ,Organic compound ,law.invention ,nanotubes ,chemistry.chemical_compound ,law ,nanofibers ,tem ,General Materials Science ,cvd synthesis ,n-doped carbon nanotubes ,chemistry.chemical_classification ,nano-onions ,oxygen reduction reaction ,xrd ,Electron energy loss spectroscopy ,General Chemistry ,Condensed Matter Physics ,Nitrogen ,eels ,chemistry ,Acetylene ,Transmission electron microscopy ,functionalization ,Carbon ,bamboo-structure - Abstract
Nitrogen doped multi-walled carbon nanotubes and other carbon nanoparticles were synthesized by catalytic chemical vapor deposition of tripropylamine and acetylene on CaCO3-supported cobalt catalyst (5 wt%), prepared by impregnation, and various precursors. Each synthesis was performed by using either the pure nitrogenous organic compound or its mixture with acetone. Transmission electron microscopy studies revealed a significant difference both in the yield and the diversity of the carbon deposits. Every synthesis resulted in bamboo-like nanotubes, and nearly all of them also in onion-like structures. Electron energy loss spectroscopy studies of the samples indicated the presence of nitrogen and calcium (caused by the catalyst support). High-resolution transmission electron microscopy and X-ray diffraction measurements were also performed to characterize the samples.
30. Preparation and characterization of multiwalled carbon nanotube/In2O3 composites
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Klara Hernadi, Vladimir M. Aroutiounian, Zoltán Németh, Peter Berki, Ottó Berkesi, Arnaud Magrez, László Forró, and Balázs Réti
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Thermogravimetric analysis ,Nanotube ,Materials science ,Scanning electron microscope ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,symbols.namesake ,law ,symbols ,General Materials Science ,Calcination ,Fourier transform infrared spectroscopy ,Composite material ,0210 nano-technology ,Spectroscopy ,Raman spectroscopy ,Scherrer equation - Abstract
We have prepared multiwalled carbon nanotube (MWCNT)/In2O3 composites using a simple impregnation method. The precursor compound indium(III) chloride (InCl3) was used to cover the surface of MWCNTs and distilled water was used as solvent. The applied mass ratio was 4:1 (In2O3/MWCNT), and during the calcination process different temperatures (300, 350 and 400 degrees C) were investigated. The produced materials were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, and a thermogravimetric analysis was executed also. The average thickness of the produced surface layer and the average sizes of the In2O3 particles were calculated with the Scherrer formula and the ImageJ-program. The results show that the heat treatment temperature affected the characteristic morphology and the crystal structure of the as-prepared composite. These multiwalled carbon nanotube-based composites are promising candidates as gas sensors and catalyst. (c) 2013 Elsevier Ltd. All rights reserved.
Catalog
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