12 research outputs found
Synthesis of Nanoparticles of Fe-Co-Ni Three-component Alloy Capsulated Into Carbon Matrix of Fe-Co-Ni/C Nanocomposites
Nanoparticles of Fe-Co-Ni three-component alloy capsulated into carbon matrix were synthesized. Structure, phase composition and magnetic properties of obtained materials were defined by diffractometry and magnetometry. It was established that composition of nanoparticles is determine by synthesis temperature, because nanoparticles of three-component alloy are forms by dissolution of cobalt in Fe-Ni alloy. Magnetization of Fe-Co-Ni/C nanocomposites and coercive force increases from 26 up to 58 AΒ·m2/kg during
temperature increase that relates with growth of particles size and increase of cobalt content in the alloy
Synthesis of Nanoparticles of Fe-Co-Ni Three-component Alloy Capsulated Into Carbon Matrix of Fe-Co-Ni/C Nanocomposites
Nanoparticles of Fe-Co-Ni three-component alloy capsulated into carbon matrix were synthesized. Structure, phase composition and magnetic properties of obtained materials were defined by diffractometry and magnetometry. It was established that composition of nanoparticles is determine by synthesis temperature, because nanoparticles of three-component alloy are forms by dissolution of cobalt in Fe-Ni alloy. Magnetization of Fe-Co-Ni/C nanocomposites and coercive force increases from 26 up to 58 AΒ·m2/kg during
temperature increase that relates with growth of particles size and increase of cobalt content in the alloy
The Synthesis of Metalcarbon Nanocomposite Ni / C on the Basis of Polyacrylonitrile
Metalcarbon nanocomposites based on polyacrylonitrile and nickel chloride are synthesized under the influence of infrared heat. The resulting materials represent a system of carbon matrix formed during the carbonization of PAN, and distributed in it nickel nanoparticles. The average size of the nanoparticles in the nanocomposite was 15-25 nm. It was found that the distribution of nickel nanoparticles sizes is determined by temperature synthesis nanocomposite. Thus with increasing temperature, the predominant average particle size of the metal increases, and the distribution is spread and shifted toward larger sizes.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3360
The Structure and Magnetic Properties Metal-carbon Nanocomposites NiCo / C on Based of Polyacrylonitrile
By method of IR-pyrolysis the precursor of polyacrylonitrile and compounds of cobalt and nickel metal-carbon nanocomposites were obtained, representing nanoparticles of alloy NiCo, dispersed in nanocrystal-line carbon matrix. Identification of alloy nanoparticles was carried out by the values of the lattice param e-ter, which was determined by X-ray analysis and was 0,3533 nm (values of the lattice parameter for Ni
0,3529 nm), this corresponds intermetallics Ni0,5Co0,5. By XRD analysis it was determined that an increase
in the synthesis temperature of 500 to 800 ΒΊC leads to increase in average size of coherent dissipation of
crystallite metal phase.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3632
The Formation and Study of the FeCo Nanoparticles Alloy in Structure of Metal-Carbon Nanocomposites FeCo/C
The study of the peculiarities of the formation of the nanoparticles FeCo-alloy in the composition of
metal-carbon nanocomposites FeCo/C.
Structure, phase composition and kinetic processes of synthesis of nanocomposites FeCo/C by methods
of Mossbauer spectroscopy were studied. This allowed us to establish the peculiarities of formation of nanoparticles
FeCo alloy in the composition of the nanocomposites. The nanocomposites were synthesized by
the IR-pyrolysis at temperatures of precursors of 300 - 800 Β°C on the basis of polyacrylonitrile (PAN), iron
acetylacetonate and cobalt acetate.
Also it is established that an increase in the average size of nanoparticles FeCo with increasing temperature
synthesis is occurred. In the temperature range of synthesis of 600-800 Β°C the size varies from 9-
10 to 16-18 nm, respectively.
The features the phase transitions and phase composition of the metal-carbon nanocomposites FeCo / C
were studied by Mossbauer spectroscopy. Nanocomposites were synthesized in the temperature range of T
= 300-800 Β°C. It was shown that the samples synthesized at T = 300 Β°C contains of superparamagnetic nanoparticles
of magnetite and amorphous oxide of iron only. The process of forming nanoparticles of alloy
FeCo occurs within the temperature range 500-600 Β° C due to the recovery of amorphous iron oxide and
magnetite as well as them dissolving in a phase of cobalt. The growth of size of nanoparticles of alloy by
agglomeration and dissolution of iron in the alloy nanoparticles occurs only at the temperature range of
synthesis 600-800 Β° C. This is confirmed by a decrease of the content of Fe, which associated with carbon
and it is consistent with the results of phase and structural studies, carried out in previous works
Features of Formation of the Nanoparticles of Alloys in Metal-carbon Nanocomposites FeCo / C and NiCo / C on Based Polyacrylonitrile
By the method of IR-heating the precursor on base of polyacrylonitrile, compounds of iron, cobalt and nickel
metal-carbon nanocomposites were obtained, representing an ensemble of nanoparticles of intermetallic FeCo
(NiCo), dispersed in nanocrystalline carbon matrix. XRD analysis revealed that the carbon structure of the PAN-based matrix changed from amorphous to nanocrystalline at the processing temperatures in the range 200-700 Β°C. Thus there is a reduction of metals from compounds released by degradation of the polymer with hydro-gen. FeCo alloy nanoparticles formed at synthesis temperatures Tβ₯500 Β°C, in the case of nanocomposites Ni-Co / C alloy nanoparticle formation is possible at T β₯ 270 Β°C, which is associated with a lower temperature com-pared to the recovery of nickel from iron. According to the results of TGA and DSC found that metals are capable
of initiating the chemical transformation in the PAN, resulting in reduction start temperature degradation. Ac-cording to the results of DSC revealed that the formation of nanoparticles is accompanied by release of heat due
to exothermic processes occurring in the nanocomposites.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3631
Influence of the Ratio of Metal Composed Nanocomposites Fe-Co / C on Phase Composition
Metalcarbon nanocomposites based on polyacrylonitrile and nickel chloride are synthesized under the influence of infrared heat. The resulting materials represent a system of carbon matrix formed during the carbonization of PAN, and distributed in it nickel nanoparticles. The average size of the nanoparticles in the nanocomposite was 15-25 nm. It was found that the distribution of nickel nanoparticles sizes is determined by temperature synthesis nanocomposite. Thus with increasing temperature, the predominant average particle size of the metal increases, and the distribution is spread and shifted toward larger sizes.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3360
Propagation and blocking in periodically hostile environments
We study the persistence and propagation (or blocking) phenomena for a
species in periodically hostile environments. The problem is described by a
reaction-diffusion equation with zero Dirichlet boundary condition. We first
derive the existence of a minimal nonnegative nontrivial stationary solution
and study the large-time behavior of the solution of the initial boundary value
problem. To the main goal, we then study a sequence of approximated problems in
the whole space with reaction terms which are with very negative growth rates
outside the domain under investigation. Finally, for a given unit vector, by
using the information of the minimal speeds of approximated problems, we
provide a simple geometric condition for the blocking of propagation and we
derive the asymptotic behavior of the approximated pulsating travelling fronts.
Moreover, for the case of constant diffusion matrix, we provide two conditions
for which the limit of approximated minimal speeds is positive
The Influence of Synthesis Temperature on the Structure, Composition and Magnetic Properties of Nanocomposites NiCo/C
By method of IR-pyrolysis the precursor of polyacrylonitrile and compounds of cobalt and nickel metalcarbon
nanocomposites were obtained, representing nanoparticles of alloy NiCo, dispersed in nanocrystalline
carbon matrix. NiCo / C nanocomposites are ferromagnets. Magnetization and the coercive force depends
on the size and composition of the alloy nanoparticles NiCo. The average size of metal nanoparticles
is determined by the synthesis temperature and in range of 350-800 Β°C is 10-80 nm, respectively. According
to the results of TEM it was detected that with increasing synthesis temperature the maximum synthesis
of nanoparticles size distribution shifts to larger sizes. The magnetization and coercivity depend on
the size and composition of the nanoparticles of alloy NiCo. With increasing synthesis temperature from
350 to 800 Β°C the magnetization increases from 0.055 to 17 AΒ·m2/kg