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1

Percolation Phenomena in Cu_{x}(SiO_{y})_{100-x} Nanocomposite Films Produced by Ion Beam-Sputtering

100%

Koltunowicz T., Zukowski P., Czarnacka K., Svito I., Fedotov A.

Acta Physica Polonica A

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2015

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vol. 128

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issue 5

908-911

EN

In this paper the results of examinations of nanocomposites Cu_{x}(SiO_{y})_{100-x} produced by ion beam sputtering using argon ions were presented. The examinations were performed by the use of ac devices for measuring frequency in the range 50 Hz-1 MHz and temperatures from 81 K to 273 K. The measurements were performed for the samples directly after production. Based on temperature dependences of conductivity σ , which were determined at the frequency 100 Hz, the Arrhenius graphs were prepared. From these graphs conductivity activation energies ΔE were calculated. Dependences of conductivity and activation energy of electrons on the metallic phase content x at the frequency 100 Hz were determined. Analysis of the obtained dependences shows that conductivity is a parabolic function of the metallic phase content x in nanocomposites. Changes of activation energies of nanocomposites, in which metallic phase contents are in the ranges x < 12 at.% and x > 68 at.%, demonstrate negative values - metallic type of conductivity. In the range 12 at.% < x < 68 at.% activation energies have positive values - the dielectric type of conductivity. It was established that for the metallic phase content of about 68 at.% the real percolation threshold occurs, and the conduction changes from dielectric to metallic type.

2

Mechanisms of Carrier Transport in Cu_x(SiO₂)_{1-x} Nanocomposites Manufactured by Ion-Beam Sputtering with Ar Ions

86%

Fedotov A., Mazanik A., Svito I., Saad A., Fedotova V., Czarnacka K., Koltunowicz T.

Acta Physica Polonica A

|

2015

|

vol. 128

|

issue 5

883-886

EN

The present paper investigates the temperature/frequency dependences of admittance Z in the granular Cu_x(SiO₂)_{1-x} nanocomposite films around the percolation threshold x_{C} in the temperature range of 4-300 K and frequencies of 20-10⁶ Hz. The behavior of low-frequency ReZ(T) dependences displayed the predominance of electrons hopping between the closest Cu-based nanoparticles for the samples below the percolation threshold x_{C} ≈ 0.59 and nearly metallic behaviour beyond the x_{C}. The high-frequency curves ReZ(f) at temperatures T > 10 K for the samples with x < x_{C} exhibited behavior close to ReZ(f) ≈ f^{-s} with s ≈ 1.0 which is very similar to the known Mott law for electron hopping mechanism. For the samples beyond the percolation threshold (x > x_{C}), the frequency dependences of ReZ(f) displayed inductive-like (not capacitive) behaviour with positive values of the phase shift angles.

3

Ion Beam Formation of Electrocatalysts for Direct Methanol and Ethanol Fuel Cells on the Basis of Carbon Catalyst Supports

86%

Poplavsky V., Dorozhko A., Luhin V., Matys V., Zukowski P., Czarnacka K.

Acta Physica Polonica A

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2017

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vol. 132

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issue 2

278-282

EN

Ion-beam modification of materials whose service properties are mainly controlled by the surface composition is of especial interest, in particular, for electrocatalysts, namely electrodes of fuel cells - perspective chemical current sources. A catalyst is needed for effective operation of fuel cell. In this paper active layers of the electrocatalysts were prepared by ion beam assisted deposition of catalytic (platinum) and activating (cerium) metals onto carbon (AVCarb® Carbon Fiber Paper P50 and Toray Carbon Fiber Paper TGP-H-060 T) catalyst supports. Formation of layers by ion beam assisted deposition by means of the deposition of metal and mixing of precipitating layer with the substrate by accelerated ions of the same metal, was carried out. Metal deposition and mixing between the precipitable layer and surface of the substrate by accelerated (U=10 kV) ions of the same metal were conducted from a neutral vapor fraction and plasma of vacuum arc discharge of a pulsed electric arc ion source. Study of the morphology and composition of layers was carried out by the scanning electron microscopy, energy dispersive X-ray microanalysis, X-ray fluorescence analysis, and the Rutherford backscattering spectrometry methods. According to the investigations with the use of cyclic voltammetry, the electrocatalysts with the prepared layers exhibited catalytic activity in the reactions of electrochemical oxidation of methanol and ethanol, which form the basis for the principle of operation of low temperature direct methanol and direct ethanol fuel cells.

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3 Acta Physica Polonica A

1 2017

2 2015

3 Czarnacka K.

2 Fedotov A.

2 Koltunowicz T.

2 Svito I.

2 Zukowski P.

1 Dorozhko A.

1 Fedotova V.

1 Luhin V.

1 Matys V.

1 Mazanik A.

1 Poplavsky V.

1 Saad A.

Percolation Phenomena in Cu_{x}(SiO_{y})_{100-x} Nanocomposite Films Produced by Ion Beam-Sputtering

Mechanisms of Carrier Transport in Cu_x(SiO₂)_{1-x} Nanocomposites Manufactured by Ion-Beam Sputtering with Ar Ions

Ion Beam Formation of Electrocatalysts for Direct Methanol and Ethanol Fuel Cells on the Basis of Carbon Catalyst Supports