Effect of the in situ synthesis of vanadium oxide nanowires on the electrical properties of hybrid nanocomposites based on synthetic carbon matrices

Abstract

Organic–inorganic nanocomposites (RF/VOX) were prepared by sol–gel method coupled with pyrolysis treatment using a resorcinol–formaldehyde carbon matrix enriched with vanadium nanoparticles. The structural properties of the final product were characterised using X-ray diffraction, revealing the transformation of the incorporated vanadium oxide from the V₂O₅ phase to V₂O₃ due to the pyrolysis temperature in a reductive atmosphere, alongside the formation of vanadium carbide (V₈C₇) in the sample treated at 1000 °C. The X-ray analysis also indicated the presence of a graphite phase across all samples. Microscopic examinations showed macroporous carbon structures enriched with vanadium oxide in the form of nanowires. These structural features significantly influenced the materials' electrical properties. At low frequencies, the AC conductance indicated a thermally activated process in the RF/VOX-625 and RF/VOX-650 samples pyrolysed y at 625 °C and 650 °C, respectively. RF/VOX-625 displayed semiconductor behaviour at high frequencies, while RF/VOX-650 transited from semiconductor behaviour to metal one at 200 K. The changes in the exponent s suggested that the CBH model effectively describes the AC conduction mechanism. Impedance analysis highlighted a relaxation phenomenon, and Nyquist plots illustrated the contribution of grain and grain boundaries in RF/VOX-625 and RF/VOX-650 at low temperatures. Furthermore, these plots indicated that in RF/VOX-650, the grain effect became predominant beyond 200 K. Incorporating vanadium oxide nanoparticles into the polymer matrix resulted in distinct physical properties and behaviours compared to the original organic matrix, allowing this material to be tested in various applications including negatronic devices and electronic components.