N. Froumin - Academia.edu (original) (raw)
Papers by N. Froumin
Batteries & Supercaps, 2020
Advanced Electronic Materials, 2019
The lower performance of pseudocapacitive supercapacitors in high‐frequency applications such as ... more The lower performance of pseudocapacitive supercapacitors in high‐frequency applications such as alternating current (AC) line filtering has been ascribed to presumed slow kinetics of redox processes compared to ion diffusion in electric double layer capacitors. A nickel‐deposited ruthenium/ruthenium‐oxide symmetric supercapacitor exhibiting remarkable electrochemical properties, particularly very high frequency response (>1 kHz) is developed. The electrodes are prepared via a simple process consisting of electrochemical reduction of ruthenium chloride on commercially available nickel foil as the current collector. A symmetric supercapacitor comprising nickel/ruthenium/ruthenium‐oxide electrodes and a polystyrene‐based thin spacer exhibits particularly fast scan rates, high power density of 1500 mW cm−2 (88 kW cm−3) with a maximum energy density of 0.58 µWh cm−2 (34 mWh cm−3), and excellent capacitance retention. Notably, supercapacitors prepared by the same synthetic method albe...
RSC Advances, 2016
Colloidal Au film forms at a water/pentane interface through spontaneous crystallization/reductio... more Colloidal Au film forms at a water/pentane interface through spontaneous crystallization/reduction of water-soluble gold complex.
Journal of Materials Science, 2015
Journal of Materials Science, 2015
ChemPhysChem, 2014
Bottom‐up synthesis offers novel routes to obtain nanostructures for nanotechnology applications.... more Bottom‐up synthesis offers novel routes to obtain nanostructures for nanotechnology applications. Most self‐assembly processes are carried out in three dimensions (i.e. solutions); however, the large majority of nanostructure‐based devices function in two dimensions (i.e. on surfaces). Accordingly, an essential and often cumbersome step in bottom‐up applications involves harvesting and transferring the synthesized nanostructures from the solution onto target surfaces. We demonstrate a simple strategy for the synthesis and chemical transformation of tellurium nanorods, which is carried out directly at the solid–solution interface. The technique involves binding the nanorod precursors onto amine‐functionalized surfaces, followed by in situ crystallization/oxidation. We show that the surface‐anchored tellurium nanorods can be further transformed in situ into Ag2Te, Cu2Te, and SERS‐active Au–Te nanorods. This new approach offers a way to construct functional nanostructures directly on s...
Le Journal de Physique IV, 1998
ABSTRACT The magnetic and conductive properties of polycrystalline La0.5Pb0.5MnO3 containing ~13a... more ABSTRACT The magnetic and conductive properties of polycrystalline La0.5Pb0.5MnO3 containing ~13at.% of a second phase PB3Mn6O13. were investigated. The studies reported include measurements of magnetization, electrical resistivity and magnetoresistance, in a temperature range 10 ÷ 400 K and at applied magnetic fields up to 5 Tesla. It was found that the sample exhibits a ferromagnetic ordering with relatively low coercive field at room temperature. Measurements of field-cooled and reversed-field-cooled magnetization support models of coexisting magnetic phases in ferromagnetic La-based manganites. The resistivity measured eshibits a maximum at ~ 230 K and a broad shallow minimum at ~ 20+25 K. These features are also attnbuted to the temperature dependence of the magnctic inhomogeneities. Measurcments of magnetoresistance show a characteristic giant effect at low temperatures.
Chemical Communications, 2013
Journal of Nanoscience and Nanotechnology, 2015
We report on investigation of detonation nanodiamond annealed at 800C°in chlorine atmosphere by m... more We report on investigation of detonation nanodiamond annealed at 800C°in chlorine atmosphere by means of 1H, 13C and 35Cl nuclear magnetic resonance and X-ray photoelectron spectroscopy. The results of these methods are found to be consistent with each other and evidence formation of chlorine-carbon groups and sp2 carbon shell on the nanodiamond surface. The data obtained provide detailed information about the structure and bonding in this diamond nanoparticle. Interaction of nuclear spins with unpaired electron spins of dangling bonds results in fast 13C nuclear spin-lattice relaxation.
Chinese Physics Letters, 2000
ABSTRACT Interfacial reactions between aluminium and polycrystalline cermet TiC0.6 were investiga... more ABSTRACT Interfacial reactions between aluminium and polycrystalline cermet TiC0.6 were investigated using x-ray photoelectron spectroscopy, Auger electron spectroscopy and x-ray diffraction. It was found that titanium exists in two chemical states. The carbide and oxide of titanium can be detected simultaneously. And the atomic ratio of Ti:C:O is 5:3:2. This suggests that TiC0.6 is a Ti-oxycarbide or oxygenated TiC composite: Ti5C3O2 (TiO2+4TiC0.75). When Al is deposited in vacuum on the Ti-Oxycarbide surface, the active Al atoms react chemically only with TiO2 at room temperature, but not with TiC0.75 in Ti-Oxycarbide. The reaction products are Al2O3 and the intermetallic compound Al3Ti. Annealing the Al/TiC0.6 interface at 750°C, Al reacts also with TiC0.75 to form a brittle Al4C3 phase. PACS: 68. 35. -p, 79. 60. -i, 73. 20. -r
IOP Conference Series: Materials Science and Engineering
Spontaneous infiltration of molten metals in to ceramic skeletons, in the course MMCs' produc... more Spontaneous infiltration of molten metals in to ceramic skeletons, in the course MMCs' production, is related to improved wetting of the ceramic by metals. TiC is considered a "metal-like" carbide and is supposed to be wetted well by metals through metallic bonding mechanism. Nevertheless, TiC/Cu exhibit an unusual behavior since spontaneous infiltration of molten Cu takes place, while TiC is partially wetted by Cu (θ=90°).In this work we studied the relation between wetting and spontaneous infiltration in the TaC/Au, Al and Cu systems. TaC is also considered a "metal-like" carbide and indeed no chemical interaction was observed at the interfaces of the studied systems.Sessile drop experiments showed almost perfect wetting in the three system but spontaneous infiltration occurred only in the first two (e.g. TaC/Au or Al). Thermodynamic calculation shows the difference between the systems which also has its' influence on the mechanical properties of the MMCs'. Further calculation clarifies the difference between TaC/Cu and TiC/Cu infiltration behavior, but is unable to explain the wetting results differences.Correlation between wetting and spontaneous infiltration in some cases is not straight forward and more studies and calculations on the atomistic level should be done in order to clarify this matter.
Studies in Surface Science and Catalysis, 2000
CoNx on alumina catalyst yielded high performance in the oxidative dehydrogenation of n-butane. 4... more CoNx on alumina catalyst yielded high performance in the oxidative dehydrogenation of n-butane. 47.6 mol% yield of olefins at 82% butane conversion was reached at 600°C. Most of olefins were ethylene and propylene formed via route of oxidative cracking of n-butane. Catalyst was prepared by deposition of sodium salt of octa (4,5-carboxy) cobalt phthalocyanine (NaCoPc) followed by calcination in He
Ewsuk/Characterization, 2006
Materials Science and Engineering: A, 2008
Ab initio simulations of the adsorption of Al atoms on CaF2 (001) and (111) surfaces have been pe... more Ab initio simulations of the adsorption of Al atoms on CaF2 (001) and (111) surfaces have been performed for supercells with 7 different atomic configurations, using density functional theory. For (111) surfaces, a repulsive interaction was observed for most configurations, while a weak attraction was obtained when the Al atom was placed above F atoms. For the Ca-terminated (001) surface, the adsorption energy was about 5 times larger, whereas for the F-terminated (001) surface it was about 20 times greater. The comparative analysis indicates that the (001) surfaces are reactive and have a strong Al adatom bonding (chemisorption), especially for the F-terminated substrate. On the contrary, the (111) plane may be considered as non-reactive (physisorption), having a weak bonding of the Al adatom above the F site.
Journal of Materials Science Research, 2012
Materials Science and Engineering: A, 2008
ABSTRACT This paper is concerned with the wetting of CaF2 by liquid Cu and In and with the effect... more ABSTRACT This paper is concerned with the wetting of CaF2 by liquid Cu and In and with the effect of Ti additions to the melt. According to thermodynamic analysis and to the experimental observations, the significantly decreased contact angle following the addition of Ti to the molten metals is not due to the formation of interfacial fluoride phases, in contrast to previously reported results. Ab initio density functional calculations indicate that preferential Ti adsorption takes place at the near CaF2 surface. It is suggested that the presence of a Ti-enriched liquid, adjacent to the substrate, gives rise, by means of heterogeneous nucleation, to the formation of a thin intermetallic compound layer that stands behind the experimentally observed enhanced wetting. The suggested wetting mechanism is supported by the notable correlation that has been observed between the temperature dependence of the contact angle and the temperature domains, associated with the presence of intermetallic compounds in both Me–Ti (Me = Cu, In) binary systems.
The Journal of Physical Chemistry C, 2010
... with a known amount of paramagnetic defects, N s = (6.3 ± 0.5) × 10 19 spins/g.(22). ... Furt... more ... with a known amount of paramagnetic defects, N s = (6.3 ± 0.5) × 10 19 spins/g.(22). ... Furthermore, the intense peak around δ = 36 ppm is asymmetric and could, in principle, be deconvoluted into ... The narrow line having a chemical shift of δ = 36.1 ± 0.3 ppm and a line width of Δν ...
Batteries & Supercaps, 2020
Advanced Electronic Materials, 2019
The lower performance of pseudocapacitive supercapacitors in high‐frequency applications such as ... more The lower performance of pseudocapacitive supercapacitors in high‐frequency applications such as alternating current (AC) line filtering has been ascribed to presumed slow kinetics of redox processes compared to ion diffusion in electric double layer capacitors. A nickel‐deposited ruthenium/ruthenium‐oxide symmetric supercapacitor exhibiting remarkable electrochemical properties, particularly very high frequency response (>1 kHz) is developed. The electrodes are prepared via a simple process consisting of electrochemical reduction of ruthenium chloride on commercially available nickel foil as the current collector. A symmetric supercapacitor comprising nickel/ruthenium/ruthenium‐oxide electrodes and a polystyrene‐based thin spacer exhibits particularly fast scan rates, high power density of 1500 mW cm−2 (88 kW cm−3) with a maximum energy density of 0.58 µWh cm−2 (34 mWh cm−3), and excellent capacitance retention. Notably, supercapacitors prepared by the same synthetic method albe...
RSC Advances, 2016
Colloidal Au film forms at a water/pentane interface through spontaneous crystallization/reductio... more Colloidal Au film forms at a water/pentane interface through spontaneous crystallization/reduction of water-soluble gold complex.
Journal of Materials Science, 2015
Journal of Materials Science, 2015
ChemPhysChem, 2014
Bottom‐up synthesis offers novel routes to obtain nanostructures for nanotechnology applications.... more Bottom‐up synthesis offers novel routes to obtain nanostructures for nanotechnology applications. Most self‐assembly processes are carried out in three dimensions (i.e. solutions); however, the large majority of nanostructure‐based devices function in two dimensions (i.e. on surfaces). Accordingly, an essential and often cumbersome step in bottom‐up applications involves harvesting and transferring the synthesized nanostructures from the solution onto target surfaces. We demonstrate a simple strategy for the synthesis and chemical transformation of tellurium nanorods, which is carried out directly at the solid–solution interface. The technique involves binding the nanorod precursors onto amine‐functionalized surfaces, followed by in situ crystallization/oxidation. We show that the surface‐anchored tellurium nanorods can be further transformed in situ into Ag2Te, Cu2Te, and SERS‐active Au–Te nanorods. This new approach offers a way to construct functional nanostructures directly on s...
Le Journal de Physique IV, 1998
ABSTRACT The magnetic and conductive properties of polycrystalline La0.5Pb0.5MnO3 containing ~13a... more ABSTRACT The magnetic and conductive properties of polycrystalline La0.5Pb0.5MnO3 containing ~13at.% of a second phase PB3Mn6O13. were investigated. The studies reported include measurements of magnetization, electrical resistivity and magnetoresistance, in a temperature range 10 ÷ 400 K and at applied magnetic fields up to 5 Tesla. It was found that the sample exhibits a ferromagnetic ordering with relatively low coercive field at room temperature. Measurements of field-cooled and reversed-field-cooled magnetization support models of coexisting magnetic phases in ferromagnetic La-based manganites. The resistivity measured eshibits a maximum at ~ 230 K and a broad shallow minimum at ~ 20+25 K. These features are also attnbuted to the temperature dependence of the magnctic inhomogeneities. Measurcments of magnetoresistance show a characteristic giant effect at low temperatures.
Chemical Communications, 2013
Journal of Nanoscience and Nanotechnology, 2015
We report on investigation of detonation nanodiamond annealed at 800C°in chlorine atmosphere by m... more We report on investigation of detonation nanodiamond annealed at 800C°in chlorine atmosphere by means of 1H, 13C and 35Cl nuclear magnetic resonance and X-ray photoelectron spectroscopy. The results of these methods are found to be consistent with each other and evidence formation of chlorine-carbon groups and sp2 carbon shell on the nanodiamond surface. The data obtained provide detailed information about the structure and bonding in this diamond nanoparticle. Interaction of nuclear spins with unpaired electron spins of dangling bonds results in fast 13C nuclear spin-lattice relaxation.
Chinese Physics Letters, 2000
ABSTRACT Interfacial reactions between aluminium and polycrystalline cermet TiC0.6 were investiga... more ABSTRACT Interfacial reactions between aluminium and polycrystalline cermet TiC0.6 were investigated using x-ray photoelectron spectroscopy, Auger electron spectroscopy and x-ray diffraction. It was found that titanium exists in two chemical states. The carbide and oxide of titanium can be detected simultaneously. And the atomic ratio of Ti:C:O is 5:3:2. This suggests that TiC0.6 is a Ti-oxycarbide or oxygenated TiC composite: Ti5C3O2 (TiO2+4TiC0.75). When Al is deposited in vacuum on the Ti-Oxycarbide surface, the active Al atoms react chemically only with TiO2 at room temperature, but not with TiC0.75 in Ti-Oxycarbide. The reaction products are Al2O3 and the intermetallic compound Al3Ti. Annealing the Al/TiC0.6 interface at 750°C, Al reacts also with TiC0.75 to form a brittle Al4C3 phase. PACS: 68. 35. -p, 79. 60. -i, 73. 20. -r
IOP Conference Series: Materials Science and Engineering
Spontaneous infiltration of molten metals in to ceramic skeletons, in the course MMCs' produc... more Spontaneous infiltration of molten metals in to ceramic skeletons, in the course MMCs' production, is related to improved wetting of the ceramic by metals. TiC is considered a "metal-like" carbide and is supposed to be wetted well by metals through metallic bonding mechanism. Nevertheless, TiC/Cu exhibit an unusual behavior since spontaneous infiltration of molten Cu takes place, while TiC is partially wetted by Cu (θ=90°).In this work we studied the relation between wetting and spontaneous infiltration in the TaC/Au, Al and Cu systems. TaC is also considered a "metal-like" carbide and indeed no chemical interaction was observed at the interfaces of the studied systems.Sessile drop experiments showed almost perfect wetting in the three system but spontaneous infiltration occurred only in the first two (e.g. TaC/Au or Al). Thermodynamic calculation shows the difference between the systems which also has its' influence on the mechanical properties of the MMCs'. Further calculation clarifies the difference between TaC/Cu and TiC/Cu infiltration behavior, but is unable to explain the wetting results differences.Correlation between wetting and spontaneous infiltration in some cases is not straight forward and more studies and calculations on the atomistic level should be done in order to clarify this matter.
Studies in Surface Science and Catalysis, 2000
CoNx on alumina catalyst yielded high performance in the oxidative dehydrogenation of n-butane. 4... more CoNx on alumina catalyst yielded high performance in the oxidative dehydrogenation of n-butane. 47.6 mol% yield of olefins at 82% butane conversion was reached at 600°C. Most of olefins were ethylene and propylene formed via route of oxidative cracking of n-butane. Catalyst was prepared by deposition of sodium salt of octa (4,5-carboxy) cobalt phthalocyanine (NaCoPc) followed by calcination in He
Ewsuk/Characterization, 2006
Materials Science and Engineering: A, 2008
Ab initio simulations of the adsorption of Al atoms on CaF2 (001) and (111) surfaces have been pe... more Ab initio simulations of the adsorption of Al atoms on CaF2 (001) and (111) surfaces have been performed for supercells with 7 different atomic configurations, using density functional theory. For (111) surfaces, a repulsive interaction was observed for most configurations, while a weak attraction was obtained when the Al atom was placed above F atoms. For the Ca-terminated (001) surface, the adsorption energy was about 5 times larger, whereas for the F-terminated (001) surface it was about 20 times greater. The comparative analysis indicates that the (001) surfaces are reactive and have a strong Al adatom bonding (chemisorption), especially for the F-terminated substrate. On the contrary, the (111) plane may be considered as non-reactive (physisorption), having a weak bonding of the Al adatom above the F site.
Journal of Materials Science Research, 2012
Materials Science and Engineering: A, 2008
ABSTRACT This paper is concerned with the wetting of CaF2 by liquid Cu and In and with the effect... more ABSTRACT This paper is concerned with the wetting of CaF2 by liquid Cu and In and with the effect of Ti additions to the melt. According to thermodynamic analysis and to the experimental observations, the significantly decreased contact angle following the addition of Ti to the molten metals is not due to the formation of interfacial fluoride phases, in contrast to previously reported results. Ab initio density functional calculations indicate that preferential Ti adsorption takes place at the near CaF2 surface. It is suggested that the presence of a Ti-enriched liquid, adjacent to the substrate, gives rise, by means of heterogeneous nucleation, to the formation of a thin intermetallic compound layer that stands behind the experimentally observed enhanced wetting. The suggested wetting mechanism is supported by the notable correlation that has been observed between the temperature dependence of the contact angle and the temperature domains, associated with the presence of intermetallic compounds in both Me–Ti (Me = Cu, In) binary systems.
The Journal of Physical Chemistry C, 2010
... with a known amount of paramagnetic defects, N s = (6.3 ± 0.5) × 10 19 spins/g.(22). ... Furt... more ... with a known amount of paramagnetic defects, N s = (6.3 ± 0.5) × 10 19 spins/g.(22). ... Furthermore, the intense peak around δ = 36 ppm is asymmetric and could, in principle, be deconvoluted into ... The narrow line having a chemical shift of δ = 36.1 ± 0.3 ppm and a line width of Δν ...