Elsevier

Applied Surface Science

Volume 337, 15 May 2015, Pages 158-165
Applied Surface Science

Effect of pyrolysis temperature on the properties of carbon/nickel nanocomposites prepared by sol–gel method

https://doi.org/10.1016/j.apsusc.2015.02.084Get rights and content
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Highlights

  • Synthesis of nickel oxide nanoparticles in carbon structures.

  • Presence of multiwall carbon nanotubes (MWNT) around Ni nanoparticles for the sample treated at high pyrolysis temperature.

  • DC conductivity exhibited the presence of conduction percolation phenomenon and the dominance of conduction model 3D-GVRH in the studied materials.

  • From AC conductance PF/Ni nanocomposites have two behaviors: semiconductor and metal, depending on the pyrolysis temperature.

  • Appearance of a negative differential resistance (NDR) at room temperature in the sample treated at 600 °C.

Abstract

Carbon–nickel nanocomposites (C/Ni) were prepared by sol–gel method after the incorporation of nickel oxide (NiO) nanoparticles in organic matrix based on pyrogallol-formaldehyde (PF). The nanocomposites heated under inert atmosphere have been characterized by various techniques such as X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), and electrical analysis. The XRD spectra exhibited the presence of NiO or metallic Ni phase in amorphous carbon matrix at low pyrolysis temperature, while at 1000 °C the graphite structure line was observed. The TEM images indicate the presence of multiwall carbon nanotubes (MWNT) around Ni nanoparticles for the sample treated at high pyrolysis temperature. The AC conductance shows that our nanocomposites have two behaviors: semiconductor and metal, depending on the pyrolysis temperature. The voltage–current V(I) characteristics of the compound show two different regions: an Ohmic region at low current and a negative differential resistance (NDR) region at higher current. This switching phenomenal behavior has been explained by an electrothermal model.

Keywords

Carbon–nickel nanocomposites
Sol–gel
Carbon nanotubes
Switching
Negative differential resistance

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