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 A·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 A·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 ºC 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 °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 °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 °C. It was shown that the samples synthesized at T = 300 °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 ° 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 ° 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 °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 T≥500 °C, in the case of nanocomposites Ni-Co / C alloy nanoparticle formation is possible at T ≥ 270 °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 °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 °C the magnetization increases from 0.055 to 17 A·m2/kg