The Experts below are selected from a list of 4029 Experts worldwide ranked by ideXlab platform
C. Reynaud - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of nanosized zirconium carbide by Laser Pyrolysis route.
Journal of Alloys and Compounds, 2009Co-Authors: L. Combemale, Y. Leconte, X. Portier, Nathalie Herlin-boime, C. ReynaudAbstract:Nanosized zirconium carbide was obtained by carburization of tetragonal zirconia/free carbon nanocomposites synthesized by Laser Pyrolysis technique using zirconium butoxide as precursor and ethylene as sensitizer gas. To achieve the carboreduction, the powder had to be annealed at high temperature under Ar atmosphere to reduce the oxygen and form zirconium carbide (ZrC). Different temperatures were investigated for the heat treatment to obtain the complete carburization while keeping the size as low as possible. The final ZrC grain size was as low as 35 nm. Powders were characterized using X-ray diffraction, thermogravimetric analysis and transmission electron microscopy.
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Synthesis of nanosized zirconium carbide by Laser Pyrolysis route
Journal of Alloys and Compounds, 2009Co-Authors: L. Combemale, Y. Leconte, X. Portier, Nathalie Herlin-boime, C. ReynaudAbstract:International audienceNanosized zirconium carbide was obtained by carburization of tetragonal zirconia/free carbon nanocomposites synthesized by Laser Pyrolysis technique using zirconium butoxide as precursor and ethylene as sensitizer gas. To achieve the carboreduction, the powder had to be annealed at high temperature under Ar atmosphere to reduce the oxygen and form zirconium carbide (ZrC). Different temperatures were investigated for the heat treatment to obtain the complete carburization while keeping the size as low as possible. The final ZrC grain size was as low as 35 nm. Powders were characterized using X-ray diffraction, thermogravimetric analysis and transmission electron microscopy
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Laser Pyrolysis: a versatile method to produce nanopowder
Actualite Chimique, 2008Co-Authors: Nathalie Herlin-boime, Y. Leconte, C. Reynaud, D. Porterat, Olivier SublemontierAbstract:Laser Pyrolysis is an efficient and versatile method to perform the synthesis of nanoparticules (silicon, oxides for catalysis...). The device is schematized and some examples of synthesis are given.
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Laser Pyrolysis synthesis and characterization of luminescent silicon nanocrystals
Physica E: Low-dimensional Systems and Nanostructures, 2007Co-Authors: O. Guillois, X. Portier, Nathalie Herlin-boime, F. Lacour, H. Perez, C. ReynaudAbstract:Quantum dots of silicon are very attractive materials due to their photoluminescence (PL) emission that can be very strong at room temperature in the visible range under UV illumination. Weighable batches are demanded for several applications in opto-electronic, photovoltaic, medicine, and so on. Laser Pyrolysis of silane in a flow reactor is an efficient method to synthesize silicon nanocrystals, but up to now the production rate for the smallest particles was very low. We present here results of a work aimed to overcome this limitation. Optimization of the Laser Pyrolysis process has been performed through an elaborate study of the synthesis parameters. Weighable batches of very small silicon particles were obtained in a controlled and reproducible way, with production rate in the 0.1-1 g/ h. High-resolution electron microscopy and specific surface measurements show that the particles were true silicon nanocrystals in the 4-9 nm range. We have then studied their PL properties. For this purpose, we have paid a particular attention to the surface passivation, an essential step to obtain efficient PL. Various ways were explored: natural oxidation under air and dispersion in liquids. We show that after natural oxidation, the PL properties are, as expected, in agreement with the quantum confinement model. Strong PL is also obtained by dispersion in solvents, but the interpretation is less straightforward in this case, and as discussed in the paper, needs further investigation.
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Laser Pyrolysis synthesis and characterization of luminescent silicon nanocrystals
Physica E: Low-dimensional Systems and Nanostructures, 2007Co-Authors: F. Lacour, X. Portier, O. Guillois, H. Perez, N. Herlin, C. ReynaudAbstract:International audienceQuantum dots of silicon are very attractive materials due to their photoluminescence (PL) emission that can be very strong at room temperature in the visible range under UV illumination. Weighable batches are demanded for several applications in opto-electronic, photovoltaic, medicine, and so on. Laser Pyrolysis of silane in a flow reactor is an efficient method to synthesize silicon nanocrystals, but up to now the production rate for the smallest particles was very low. We present here results of a work aimed to overcome this limitation. Optimization of the Laser Pyrolysis process has been performed through an elaborate study of the synthesis parameters. Weighable batches of very small silicon particles were obtained in a controlled and reproducible way, with production rate in the 0.1-1 g/ h. High-resolution electron microscopy and specific surface measurements show that the particles were true silicon nanocrystals in the 4-9 nm range. We have then studied their PL properties. For this purpose, we have paid a particular attention to the surface passivation, an essential step to obtain efficient PL. Various ways were explored: natural oxidation under air and dispersion in liquids. We show that after natural oxidation, the PL properties are, as expected, in agreement with the quantum confinement model. Strong PL is also obtained by dispersion in solvents, but the interpretation is less straightforward in this case, and as discussed in the paper, needs further investigation
Claudiu Teodor Fleaca - One of the best experts on this subject based on the ideXlab platform.
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Study of phase development and thermal stability in as synthesized TiO2 nanoparticles by Laser Pyrolysis: ethylene uptake and oxygen enrichment
Applied Surface Science, 2017Co-Authors: Alina Ilie, Claudiu Teodor Fleaca, Florian Dumitrache, M. Scarisoreanu, Elena Dutu, Ana-maria Banici, Eugenia Vasile, Ion N. MihailescuAbstract:Abstract Laser Pyrolysis has proven a viable and trustworthy method of TiO 2 nanoparticles fabrication, ensuring good quality and wide variety of nanoparticle morphologies and sizes. This work is aimed to phase control, experimentally studied, by parameter modulation, during one step Laser Pyrolysis synthesis or in combination with thermal annealing. High phase purity anatase and rutile TiO 2 nanoparticles, oxygen abundant, are synthesized from TiCl 4 and C 2 H 4 gas mixtures, in the presence of air as oxygen donor, under CO 2 Laser radiation. The nano-titania samples are analyzed by X-ray Diffraction, EDAX, TEM and Raman spectroscopy and reveal good phase stability and distinct morphology. This study extends the method applicability onto rutile majoritarian TiO 2 synthesis and generation of thermally stable anatase titania, a well-known catalyst.
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Development Of Magnetic Fe-C Nanocomposites Obtained Via The Laser Pyrolysis: Structural And Disaggregation Properties
2010Co-Authors: Ion Morjan, Rodica Alexandrescu, Claudiu Teodor Fleaca, Florian Dumitrache, I. Soare, R. Birjega, Catalin Luculescu, V. Prodan, Victor Kuncser, George FilotiAbstract:Fe@C) nanoparticles have been successfully synthesized using the Laser Pyrolysis method and variable nozzle geometries. At large nozzle diameters, XRD and SAED analysis clearly identified distinct α‐Fe and Fe3C phases. TEM and HRTEM indicated that these Fe‐based nanoparticles have an average grain size of 3.5–10.2 nm. Temperature dependent Mossbauer spectra further confirm their distinct nanophases. By using a multi‐step reduction procedure, Fe@C powders can be disaggregated into stable, water soluble nanoparticles.
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Development of Fe-doped SnO2- based nanocomposites prepared by single-step Laser Pyrolysis
Journal of Optoelectronics and Advanced Materials, 2010Co-Authors: Rodica Alexandrescu, Ion Sandu, Ion Morjan, Claudiu Teodor Fleaca, Florian Dumitrache, I. Soare, E. Popovici, R. Birjega, Catalin Luculescu, Elena DutuAbstract:We report a new synthesis technique for the preparation of Fe-Sn0 2 , namely the C0 2 Laser Pyrolysis of gas phase reactants. Tetramethyl tin, air and iron pentacarbonyl were used as precursors. At increased oxygen in mixtures, the Sn0 2 phase (mean crystallite sizes about 12 nm) largely prevails over the other two crystallographic phases: SnO and Sn. Different Fe/Sn ratios (from about 0.01 to 0.08 in at %) were obtained by varying the process parameters. No iron compounds were identified by diffraction techniques. With increased Fe doping, an overall decrease of the diffraction peaks and an inhibited particle growth may be observed.
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Controlled manufacturing of nanoparticles by the Laser Pyrolysis: Application to cementite iron carbide
Applied Surface Science, 2009Co-Authors: Ion Morjan, Rodica Alexandrescu, Claudiu Teodor Fleaca, Florian Dumitrache, I. Soare, E. Popovici, M. Scarisoreanu, L. Gavrila, Eugeniu Vasile, Victor CiupinaAbstract:Abstract The Laser Pyrolysis is an attractive technique for the synthesis of different nanostructures from gas-phase precursors. The characteristics of this synthesized method are here exemplified by the production of almost pure cementite Fe 3 C nanomaterials, obtained by the Pyrolysis of methyl methacrylate and iron pentacarbonyl (vapors). Those nanopowders exhibited core (Fe 3 C)–shell (MMA polymer-based) morphologies and mean particle diameters of about 8–9 nm. Preliminary magnetic measurements indicate rather high values for the saturation magnetization. By irradiating the same reactive mixture with a lower intensity radiation, the chemical content of nanopowders shifts towards mixtures of iron and maghemite/magnetite iron oxides.
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Photochemistry Aspects of the Laser Pyrolysis Addressing the Preparation of Oxide Semiconductor Photocatalysts
International Journal of Photoenergy, 2008Co-Authors: Rodica Alexandrescu, Ion Morjan, Claudiu Teodor Fleaca, Florian Dumitrache, I. Soare, E. Popovici, M. Scarisoreanu, R. Birjega, L. Gavrila, Gabriel ProdanAbstract:The Laser Pyrolysis is a powerful and a versatile tool for the gas-phase synthesis of nanoparticles. In this paper, some fundamental and applicative characteristics of this technique are outlined and recent results obtained in the preparation of gamma iron oxide () and titania () semiconductor nanostructures are illustrated. Nanosized iron oxide particles (4 to 9 nm diameter values) have been directly synthesized by the Laser-induced Pyrolysis of a mixture containing iron pentacarbonyl/air (as oxidizer)/ethylene (as sensitizer). Temperature-dependent Mossbauer spectroscopy shows that mainly maghemite is present in the sample obtained at higher Laser power. The use of selected samples for the preparation of water-dispersed magnetic nanofluids is also discussed. nanoparticles comprising a mixture of anatase and rutile phases were synthesized via the Laser Pyrolysis of - (vapors) based gas-phase mixtures. High precursor concentration of the oxidizer was found to favor the prevalent anatase phase (about 90%) in the titania nanopowders.
Rodica Alexandrescu - One of the best experts on this subject based on the ideXlab platform.
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New Advances in the Production of Iron-Based Nanostructures Manufactured by Laser Pyrolysis
Upscaling of Bio-Nano-Processes, 2014Co-Authors: Ion Morjan, Rodica AlexandrescuAbstract:Nanoparticles (NPs) are submicron moieties made of inorganic or organic materials, which have many novel properties compared with their bulk counterparts. The CO2 Laser Pyrolysis of gas- and vapor-phase reactants offers an approach for the synthesis of uniform nanoparticles. The synthesis of iron oxide-based nanomaterials by Laser Pyrolysis has been achieved by a handling procedure, in which the oxidation process initiates and develops inside the Laser-induced reaction zone. In a second step, a more complex experimental procedure is used, in which the iron precursor is allowed to dissociate alone in the flame with a surrounding oxidizing atmosphere. XRD and TEM analyses reveal a major content of maghemite/magnetite in samples SF. The power density and the nozzle diameter influence the particle size.
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magnetic properties of iron carbon nanocomposites obtained by Laser Pyrolysis in specific configurations
Journal of Alloys and Compounds, 2013Co-Authors: G. Schinteie, Ion Morjan, Rodica Alexandrescu, Florian Dumitrache, Victor Kuncser, P. Palade, George FilotiAbstract:Abstract New nanometric systems were produced by using specific parameters of the Laser Pyrolysis process. Relevant results related to the magnetic behavior of the samples were obtained via SQUID magnetometry and Mossbauer spectroscopy, the data being corroborated with those previously obtained from X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed nanocomposites contain iron carbides, iron oxides and metallic iron nanoparticles which relative content and average size depend strongly on experimental specific parameters of the Pyrolysis process. The magnetic properties and the local interaction mechanisms were explained by adequate magnetic relaxation and static models.
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Magnetic properties of iron–carbon nanocomposites obtained by Laser Pyrolysis in specific configurations
Journal of Alloys and Compounds, 2013Co-Authors: G. Schinteie, Ion Morjan, Rodica Alexandrescu, Florian Dumitrache, Victor Kuncser, P. Palade, George FilotiAbstract:Abstract New nanometric systems were produced by using specific parameters of the Laser Pyrolysis process. Relevant results related to the magnetic behavior of the samples were obtained via SQUID magnetometry and Mossbauer spectroscopy, the data being corroborated with those previously obtained from X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed nanocomposites contain iron carbides, iron oxides and metallic iron nanoparticles which relative content and average size depend strongly on experimental specific parameters of the Pyrolysis process. The magnetic properties and the local interaction mechanisms were explained by adequate magnetic relaxation and static models.
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Development Of Magnetic Fe-C Nanocomposites Obtained Via The Laser Pyrolysis: Structural And Disaggregation Properties
2010Co-Authors: Ion Morjan, Rodica Alexandrescu, Claudiu Teodor Fleaca, Florian Dumitrache, I. Soare, R. Birjega, Catalin Luculescu, V. Prodan, Victor Kuncser, George FilotiAbstract:Fe@C) nanoparticles have been successfully synthesized using the Laser Pyrolysis method and variable nozzle geometries. At large nozzle diameters, XRD and SAED analysis clearly identified distinct α‐Fe and Fe3C phases. TEM and HRTEM indicated that these Fe‐based nanoparticles have an average grain size of 3.5–10.2 nm. Temperature dependent Mossbauer spectra further confirm their distinct nanophases. By using a multi‐step reduction procedure, Fe@C powders can be disaggregated into stable, water soluble nanoparticles.
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Magnetic Properties of Fe Oxide Nanoparticles Produced by Laser Pyrolysis for Biomedical Applications
2010Co-Authors: M. A. García, Ion Morjan, Rodica Alexandrescu, Sabino Veintemillas, R Costo, V. Bouzas, P. Morales, M. García‐hernández, P GascoAbstract:We report on the magnetic characterization of Fe oxide nanoparticles by Laser Pyrolysis and the relationship between the preparation conditions and the magnetic response. It is shown that controlling the preparation conditions during the pyrolisis allows tuning the nanoparticles morphology and structure and consequently the magnetic properties of the nanoparticles. The nanoparticles are loaded into solid lipid nanoparticles without degradation nor significant modification of the magnetic properties.
Ion Morjan - One of the best experts on this subject based on the ideXlab platform.
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New Advances in the Production of Iron-Based Nanostructures Manufactured by Laser Pyrolysis
Upscaling of Bio-Nano-Processes, 2014Co-Authors: Ion Morjan, Rodica AlexandrescuAbstract:Nanoparticles (NPs) are submicron moieties made of inorganic or organic materials, which have many novel properties compared with their bulk counterparts. The CO2 Laser Pyrolysis of gas- and vapor-phase reactants offers an approach for the synthesis of uniform nanoparticles. The synthesis of iron oxide-based nanomaterials by Laser Pyrolysis has been achieved by a handling procedure, in which the oxidation process initiates and develops inside the Laser-induced reaction zone. In a second step, a more complex experimental procedure is used, in which the iron precursor is allowed to dissociate alone in the flame with a surrounding oxidizing atmosphere. XRD and TEM analyses reveal a major content of maghemite/magnetite in samples SF. The power density and the nozzle diameter influence the particle size.
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The influence of dilution gases on multilayer graphene formation in Laser Pyrolysis
Applied Surface Science, 2013Co-Authors: L. Gavrila-florescu, Ion Sandu, Ion Morjan, Elena Dutu, R. BirjegaAbstract:Abstract The work presents the structure and morphology of multilayer graphene formed as components of carbon nanoparticles synthesized by the Laser Pyrolysis technique. Low aggregated carbon nanoparticles with dimensions between 12 and 33 nm, which present a structured surface with multilayer graphene were synthesized from a C 2 H 2 /SF 6 gas mixture with different dilution gases. The longest multi-graphene sheets were obtained for a C/F = 3 atomic ratio and when N 2 O was used as dilution gas. The obtained carbon nanoparticles present electrical conductivity values comparable with those of multi-wall CNTs, but lower than those of single-wall CNTs.
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magnetic properties of iron carbon nanocomposites obtained by Laser Pyrolysis in specific configurations
Journal of Alloys and Compounds, 2013Co-Authors: G. Schinteie, Ion Morjan, Rodica Alexandrescu, Florian Dumitrache, Victor Kuncser, P. Palade, George FilotiAbstract:Abstract New nanometric systems were produced by using specific parameters of the Laser Pyrolysis process. Relevant results related to the magnetic behavior of the samples were obtained via SQUID magnetometry and Mossbauer spectroscopy, the data being corroborated with those previously obtained from X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed nanocomposites contain iron carbides, iron oxides and metallic iron nanoparticles which relative content and average size depend strongly on experimental specific parameters of the Pyrolysis process. The magnetic properties and the local interaction mechanisms were explained by adequate magnetic relaxation and static models.
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Magnetic properties of iron–carbon nanocomposites obtained by Laser Pyrolysis in specific configurations
Journal of Alloys and Compounds, 2013Co-Authors: G. Schinteie, Ion Morjan, Rodica Alexandrescu, Florian Dumitrache, Victor Kuncser, P. Palade, George FilotiAbstract:Abstract New nanometric systems were produced by using specific parameters of the Laser Pyrolysis process. Relevant results related to the magnetic behavior of the samples were obtained via SQUID magnetometry and Mossbauer spectroscopy, the data being corroborated with those previously obtained from X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed nanocomposites contain iron carbides, iron oxides and metallic iron nanoparticles which relative content and average size depend strongly on experimental specific parameters of the Pyrolysis process. The magnetic properties and the local interaction mechanisms were explained by adequate magnetic relaxation and static models.
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Development Of Magnetic Fe-C Nanocomposites Obtained Via The Laser Pyrolysis: Structural And Disaggregation Properties
2010Co-Authors: Ion Morjan, Rodica Alexandrescu, Claudiu Teodor Fleaca, Florian Dumitrache, I. Soare, R. Birjega, Catalin Luculescu, V. Prodan, Victor Kuncser, George FilotiAbstract:Fe@C) nanoparticles have been successfully synthesized using the Laser Pyrolysis method and variable nozzle geometries. At large nozzle diameters, XRD and SAED analysis clearly identified distinct α‐Fe and Fe3C phases. TEM and HRTEM indicated that these Fe‐based nanoparticles have an average grain size of 3.5–10.2 nm. Temperature dependent Mossbauer spectra further confirm their distinct nanophases. By using a multi‐step reduction procedure, Fe@C powders can be disaggregated into stable, water soluble nanoparticles.
Florian Dumitrache - One of the best experts on this subject based on the ideXlab platform.
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Study of phase development and thermal stability in as synthesized TiO2 nanoparticles by Laser Pyrolysis: ethylene uptake and oxygen enrichment
Applied Surface Science, 2017Co-Authors: Alina Ilie, Claudiu Teodor Fleaca, Florian Dumitrache, M. Scarisoreanu, Elena Dutu, Ana-maria Banici, Eugenia Vasile, Ion N. MihailescuAbstract:Abstract Laser Pyrolysis has proven a viable and trustworthy method of TiO 2 nanoparticles fabrication, ensuring good quality and wide variety of nanoparticle morphologies and sizes. This work is aimed to phase control, experimentally studied, by parameter modulation, during one step Laser Pyrolysis synthesis or in combination with thermal annealing. High phase purity anatase and rutile TiO 2 nanoparticles, oxygen abundant, are synthesized from TiCl 4 and C 2 H 4 gas mixtures, in the presence of air as oxygen donor, under CO 2 Laser radiation. The nano-titania samples are analyzed by X-ray Diffraction, EDAX, TEM and Raman spectroscopy and reveal good phase stability and distinct morphology. This study extends the method applicability onto rutile majoritarian TiO 2 synthesis and generation of thermally stable anatase titania, a well-known catalyst.
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Magnetic properties of iron–carbon nanocomposites obtained by Laser Pyrolysis in specific configurations
Journal of Alloys and Compounds, 2013Co-Authors: G. Schinteie, Ion Morjan, Rodica Alexandrescu, Florian Dumitrache, Victor Kuncser, P. Palade, George FilotiAbstract:Abstract New nanometric systems were produced by using specific parameters of the Laser Pyrolysis process. Relevant results related to the magnetic behavior of the samples were obtained via SQUID magnetometry and Mossbauer spectroscopy, the data being corroborated with those previously obtained from X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed nanocomposites contain iron carbides, iron oxides and metallic iron nanoparticles which relative content and average size depend strongly on experimental specific parameters of the Pyrolysis process. The magnetic properties and the local interaction mechanisms were explained by adequate magnetic relaxation and static models.
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magnetic properties of iron carbon nanocomposites obtained by Laser Pyrolysis in specific configurations
Journal of Alloys and Compounds, 2013Co-Authors: G. Schinteie, Ion Morjan, Rodica Alexandrescu, Florian Dumitrache, Victor Kuncser, P. Palade, George FilotiAbstract:Abstract New nanometric systems were produced by using specific parameters of the Laser Pyrolysis process. Relevant results related to the magnetic behavior of the samples were obtained via SQUID magnetometry and Mossbauer spectroscopy, the data being corroborated with those previously obtained from X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed nanocomposites contain iron carbides, iron oxides and metallic iron nanoparticles which relative content and average size depend strongly on experimental specific parameters of the Pyrolysis process. The magnetic properties and the local interaction mechanisms were explained by adequate magnetic relaxation and static models.
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Development Of Magnetic Fe-C Nanocomposites Obtained Via The Laser Pyrolysis: Structural And Disaggregation Properties
2010Co-Authors: Ion Morjan, Rodica Alexandrescu, Claudiu Teodor Fleaca, Florian Dumitrache, I. Soare, R. Birjega, Catalin Luculescu, V. Prodan, Victor Kuncser, George FilotiAbstract:Fe@C) nanoparticles have been successfully synthesized using the Laser Pyrolysis method and variable nozzle geometries. At large nozzle diameters, XRD and SAED analysis clearly identified distinct α‐Fe and Fe3C phases. TEM and HRTEM indicated that these Fe‐based nanoparticles have an average grain size of 3.5–10.2 nm. Temperature dependent Mossbauer spectra further confirm their distinct nanophases. By using a multi‐step reduction procedure, Fe@C powders can be disaggregated into stable, water soluble nanoparticles.
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Iron Oxide Materials Produced by Laser Pyrolysis
2010Co-Authors: Rodica Alexandrescu, Ion Morjan, Florian Dumitrache, María Del Puerto Morales, R Costo, M. A. García, V. Bouzas, Valentina Bello, Rossella Giorgi, Carlos J. SernaAbstract:The Laser Pyrolysis technique was employed in the production of magnetic iron oxide nanometric powders due to its capability of producing highly homogeneous nanoparticles in continuous form. This technique consists of the Laser‐driven rapid heating of an iron precursor in vapor phase in presence of oxygen. Different samples were prepared by changing the experimental conditions of synthesis. We found that high crystallinities and good magnetic properties are attained at high density of the Laser power and strong oxidation. By the contrary, softer conditions using low Laser densities and soft oxidation conditions give in general smaller and poorly ordered nanoparticles. The particles obtained were in the range of 2 to 9 nm in diameter (TEM). All of them were superparamagnetic at room temperature with saturation magnetization values in the interval of 4–38 emu/g‐sample. The samples consist in Fe2O3 maghemite with carbon as the main impurity present on the surface in the form of C = O bonds.
