Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques
The carbon films formed by accelerated C60 ion deposition are investigated by transmission electr... more The carbon films formed by accelerated C60 ion deposition are investigated by transmission electron microscopy and X-ray photoelectron spectroscopy. It is demonstrated that amorphous carbon films are formed at an ion-beam energy of 7 keV and a temperature of the substrate of 100–200°C. Substrate temperature increase to 300°C results in the formation of nanocomposite films consisting of graphite nanocrystals embedded in an amorphous carbon matrix. The presence of double- and triple-charged C60 ions with an energy of 14 and 21 keV respectively in the beam results in a decrease in the temperature of formation of the nanocomposite to 200°C. As the result of analysis of the data collected from various sample depths by X-ray photoelectron spectroscopy and Auger-electron spectroscopy, it is found that the sp3/sp2 ratio in the surface layers is higher than in the sample bulk, both in the case of a monoenergetic 7 keV beam, and in the presence of multicharged high-energy ions in the beam. If high-energy ions are present in the beam, then the sp3/sp2 ratio is higher and depends, in a complex way, on the temperature of deposition. The maximum amount of sp3 bonds in the surface layers is found at a temperature of deposition of 350°C and is equal to 88%. The water drop contact angle for this film is 96°, which is similar to the contact angle of the diamond surface.
An improved procedure for the preparation of aerogel granules of polytetrafluoroethylene-graphene... more An improved procedure for the preparation of aerogel granules of polytetrafluoroethylene-graphene oxide (PTFE-GO) with a composition of 50:50 (in wt %) and a specific density of 35 ± 2 mg/cm3 is described. The technique practically excludes the granule cracking. The specific density of the pellets after reduction using hydrazine vapor and annealing at 370 °C decreased to 29 ± 2 mg/cm3. The PTFE-reduced GO (rGO) pellets obtained were tested as a recyclable sorbent for isopropyl alcohol (IPA) in sorption/combustion cycles. It has been shown that the aerogel sorption capacity for IPA increases from 35.6 to 39.3 g/g as a result of alcohol burning off. During the combustion of IPA, the temperature of an individual pellet can exceed 300 °C. When several contingent pellets are burned, the temperature of their heating increases. The fine-pored structure of the near-surface layer of the granule is destroyed during the alcohol burning, the internal structure with larger pores is exposed, and the relative proportion of PTFE on the surface of the granules decreases. It was also shown that the specific surface area of PTFE-rGO increases from 26 to 49 m2/g during cycling.
This paper describes the comparative study of the decomposition of two iron nitrosyl complexes (N... more This paper describes the comparative study of the decomposition of two iron nitrosyl complexes (NICs) with a cysteamine thiolate ligand {Fe2[S(CH2)2NH3]2(NO)4}SO4·2.5H2O (I) and a glutathione (GSH)-ligand, [Fe2(SC10H17N3O6)2(NO)4]SO4·2H2O (II), which spontaneously evolve NO in aqueous medium.
Shock-wave-induced phase transformations in nanostructural titanium dioxide TiO2 (anatase) powder... more Shock-wave-induced phase transformations in nanostructural titanium dioxide TiO2 (anatase) powders of two types have been studied by Raman spectroscopy. It is established that, at a shock-wave compression to 42 GPa, anatase particles can either transform into a columbite phase or exhibit amorphization.
A composite aerogel with superhydrophobic external surface has been synthesized from reduced grap... more A composite aerogel with superhydrophobic external surface has been synthesized from reduced graphene oxide and polytetrafluoroethylene taken in a weight ratio of 1 : 1. The porous structure of the aerogel has been studied by the standard contact porosimetry method (SCPM). The porosimetric curves measured with respect to octane and water intersect in the region of small pores, thereby leading to the fact that the specific surface area of the aerogel in water is much larger than that in octane, although octane is known to wet any material almost ideally. This phenomenon, which is referred to as “superhydrophilicity,” is explained by the fact that, in the region of mesopores, a sample swells in water due to the hydration of surface –CO and –COH groups, which have been identified with the help of IR and Raman spectroscopies. Thus, the outside surface of the aerogel granules is superhydrophobic, while their interior is superhydrophilic in the region of small pores. As follows from the SCPM data, the total porosity and specific surface area of the aerogel are substantially larger than those of Vulcan XC-72 carbon black, which is a standard carrier for Pt catalysts used in fuel cells based on proton-exchange membranes. Oxygen electroreduction at the aerogel, containing Pt deposited in an amount of 28 µg/cm2, has been studied by the method of rotating disk electrode (RDE) in an aqueous 0.5 M H2SO4 solution, and the results obtained have been compared with the data on standard commercial Pt (20%)/Vulcan XC-72 catalyst. It has been shown that the limiting diffusion RDE currents for Pt supported on the hydrophobic–hydrophilic aerogel are markedly higher than those for the standard catalyst because of the easier access of oxygen to the reaction zone as compared with hydrophilic Vulcan XC-72 carbon black carrier.
The process of hydrophobization of melamine sponges has been investigated. Solutions of radiation... more The process of hydrophobization of melamine sponges has been investigated. Solutions of radiation-synthesized tetrafluoroethylene telomers, which had different chain lengths and end groups, in acetone and a Freon 113–ammonia solvent blend were used as water repellents. The composition and structure of hydrophobized melamine sponges were studied by X-ray photoelectron and Raman spectroscopy and light and scanning electron microscopy. It has been shown that treatment with the solutions of tetrafluoroethylene telomers makes it possible to impart high hydrophobicity to a hydrophilic material to have a water contact angle on the order of 135–140°C. This significantly improves the performance and expands the practical application of melamine sponges.
A simple method for the mechanochemical synthesis of an effective metal-free electrocatalyst for ... more A simple method for the mechanochemical synthesis of an effective metal-free electrocatalyst for the oxygen reduction reaction was demonstrated. A nitrogen-doped carbon material was obtained by grinding a mixture of graphene oxide and melamine in a planetary ball mill. The resulting material was characterized by XPS, EPR, and Raman and IR spectroscopy. The nitrogen concentration on the N-bmGO surface was 5.5 at.%. The nitrogen-enriched graphene material (NbmGO has half-wave potential of −0.175/−0.09 V and was shown to possess high activity as an electrocatalyst for oxygen reduction reaction. The electrocatalytic activity of NbmGO can be associated with a high concentration of active sites for the adsorption of oxygen molecules on its surface. The high current retention (93% for 12 h) after continuous polarization demonstrates the excellent long-term stability of NbmGO.
A CO oxidation catalyst based on plasma-chemical titanium carbonitride TiC 0.2 N 0.8 and TiO 2 wi... more A CO oxidation catalyst based on plasma-chemical titanium carbonitride TiC 0.2 N 0.8 and TiO 2 with a palladium content of 10 wt % has been synthesized. The dependence of the reaction rate of CO oxidation at room temperature and low CO concentrations (<100 mg/m 3 ) on the TiC 0.2 N 0.8 content has been studied. It has been found that, at TiC 0.2 N 0.8 concentrations from 8 to 10 wt %, the catalyst exhibited a maximum rate of the CO oxidation reaction, which was 2.5 times higher than the rate of reaction on a catalyst based on pure TiO 2 that included palladium clusters. The catalysts are promising for use in catalytic and photocatalytic systems for air purification.
Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques
The carbon films formed by accelerated C60 ion deposition are investigated by transmission electr... more The carbon films formed by accelerated C60 ion deposition are investigated by transmission electron microscopy and X-ray photoelectron spectroscopy. It is demonstrated that amorphous carbon films are formed at an ion-beam energy of 7 keV and a temperature of the substrate of 100–200°C. Substrate temperature increase to 300°C results in the formation of nanocomposite films consisting of graphite nanocrystals embedded in an amorphous carbon matrix. The presence of double- and triple-charged C60 ions with an energy of 14 and 21 keV respectively in the beam results in a decrease in the temperature of formation of the nanocomposite to 200°C. As the result of analysis of the data collected from various sample depths by X-ray photoelectron spectroscopy and Auger-electron spectroscopy, it is found that the sp3/sp2 ratio in the surface layers is higher than in the sample bulk, both in the case of a monoenergetic 7 keV beam, and in the presence of multicharged high-energy ions in the beam. If high-energy ions are present in the beam, then the sp3/sp2 ratio is higher and depends, in a complex way, on the temperature of deposition. The maximum amount of sp3 bonds in the surface layers is found at a temperature of deposition of 350°C and is equal to 88%. The water drop contact angle for this film is 96°, which is similar to the contact angle of the diamond surface.
An improved procedure for the preparation of aerogel granules of polytetrafluoroethylene-graphene... more An improved procedure for the preparation of aerogel granules of polytetrafluoroethylene-graphene oxide (PTFE-GO) with a composition of 50:50 (in wt %) and a specific density of 35 ± 2 mg/cm3 is described. The technique practically excludes the granule cracking. The specific density of the pellets after reduction using hydrazine vapor and annealing at 370 °C decreased to 29 ± 2 mg/cm3. The PTFE-reduced GO (rGO) pellets obtained were tested as a recyclable sorbent for isopropyl alcohol (IPA) in sorption/combustion cycles. It has been shown that the aerogel sorption capacity for IPA increases from 35.6 to 39.3 g/g as a result of alcohol burning off. During the combustion of IPA, the temperature of an individual pellet can exceed 300 °C. When several contingent pellets are burned, the temperature of their heating increases. The fine-pored structure of the near-surface layer of the granule is destroyed during the alcohol burning, the internal structure with larger pores is exposed, and the relative proportion of PTFE on the surface of the granules decreases. It was also shown that the specific surface area of PTFE-rGO increases from 26 to 49 m2/g during cycling.
This paper describes the comparative study of the decomposition of two iron nitrosyl complexes (N... more This paper describes the comparative study of the decomposition of two iron nitrosyl complexes (NICs) with a cysteamine thiolate ligand {Fe2[S(CH2)2NH3]2(NO)4}SO4·2.5H2O (I) and a glutathione (GSH)-ligand, [Fe2(SC10H17N3O6)2(NO)4]SO4·2H2O (II), which spontaneously evolve NO in aqueous medium.
Shock-wave-induced phase transformations in nanostructural titanium dioxide TiO2 (anatase) powder... more Shock-wave-induced phase transformations in nanostructural titanium dioxide TiO2 (anatase) powders of two types have been studied by Raman spectroscopy. It is established that, at a shock-wave compression to 42 GPa, anatase particles can either transform into a columbite phase or exhibit amorphization.
A composite aerogel with superhydrophobic external surface has been synthesized from reduced grap... more A composite aerogel with superhydrophobic external surface has been synthesized from reduced graphene oxide and polytetrafluoroethylene taken in a weight ratio of 1 : 1. The porous structure of the aerogel has been studied by the standard contact porosimetry method (SCPM). The porosimetric curves measured with respect to octane and water intersect in the region of small pores, thereby leading to the fact that the specific surface area of the aerogel in water is much larger than that in octane, although octane is known to wet any material almost ideally. This phenomenon, which is referred to as “superhydrophilicity,” is explained by the fact that, in the region of mesopores, a sample swells in water due to the hydration of surface –CO and –COH groups, which have been identified with the help of IR and Raman spectroscopies. Thus, the outside surface of the aerogel granules is superhydrophobic, while their interior is superhydrophilic in the region of small pores. As follows from the SCPM data, the total porosity and specific surface area of the aerogel are substantially larger than those of Vulcan XC-72 carbon black, which is a standard carrier for Pt catalysts used in fuel cells based on proton-exchange membranes. Oxygen electroreduction at the aerogel, containing Pt deposited in an amount of 28 µg/cm2, has been studied by the method of rotating disk electrode (RDE) in an aqueous 0.5 M H2SO4 solution, and the results obtained have been compared with the data on standard commercial Pt (20%)/Vulcan XC-72 catalyst. It has been shown that the limiting diffusion RDE currents for Pt supported on the hydrophobic–hydrophilic aerogel are markedly higher than those for the standard catalyst because of the easier access of oxygen to the reaction zone as compared with hydrophilic Vulcan XC-72 carbon black carrier.
The process of hydrophobization of melamine sponges has been investigated. Solutions of radiation... more The process of hydrophobization of melamine sponges has been investigated. Solutions of radiation-synthesized tetrafluoroethylene telomers, which had different chain lengths and end groups, in acetone and a Freon 113–ammonia solvent blend were used as water repellents. The composition and structure of hydrophobized melamine sponges were studied by X-ray photoelectron and Raman spectroscopy and light and scanning electron microscopy. It has been shown that treatment with the solutions of tetrafluoroethylene telomers makes it possible to impart high hydrophobicity to a hydrophilic material to have a water contact angle on the order of 135–140°C. This significantly improves the performance and expands the practical application of melamine sponges.
A simple method for the mechanochemical synthesis of an effective metal-free electrocatalyst for ... more A simple method for the mechanochemical synthesis of an effective metal-free electrocatalyst for the oxygen reduction reaction was demonstrated. A nitrogen-doped carbon material was obtained by grinding a mixture of graphene oxide and melamine in a planetary ball mill. The resulting material was characterized by XPS, EPR, and Raman and IR spectroscopy. The nitrogen concentration on the N-bmGO surface was 5.5 at.%. The nitrogen-enriched graphene material (NbmGO has half-wave potential of −0.175/−0.09 V and was shown to possess high activity as an electrocatalyst for oxygen reduction reaction. The electrocatalytic activity of NbmGO can be associated with a high concentration of active sites for the adsorption of oxygen molecules on its surface. The high current retention (93% for 12 h) after continuous polarization demonstrates the excellent long-term stability of NbmGO.
A CO oxidation catalyst based on plasma-chemical titanium carbonitride TiC 0.2 N 0.8 and TiO 2 wi... more A CO oxidation catalyst based on plasma-chemical titanium carbonitride TiC 0.2 N 0.8 and TiO 2 with a palladium content of 10 wt % has been synthesized. The dependence of the reaction rate of CO oxidation at room temperature and low CO concentrations (<100 mg/m 3 ) on the TiC 0.2 N 0.8 content has been studied. It has been found that, at TiC 0.2 N 0.8 concentrations from 8 to 10 wt %, the catalyst exhibited a maximum rate of the CO oxidation reaction, which was 2.5 times higher than the rate of reaction on a catalyst based on pure TiO 2 that included palladium clusters. The catalysts are promising for use in catalytic and photocatalytic systems for air purification.
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