In this study, the three structures of the symmetric paper supercapacitors based on the carbon nanotubes (CNTs), graphite nanoparticles (GNPs) and graphene electrodes have been fabricated. In the supercapacitors was used of polyvinyl alcohol (PVA)/phosphoric acid (H3PO4) as a gel electrolyte and the BaTiO3 film as a separator film. The carbon nanomaterials, gel electrolyte surface, and electrode films were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The specific capacitance of the symmetric paper supercapacitors using charge-discharge technique and C-V curves at the voltage scan rates 20 mV/s and 150 mV/s have been investigated. The symmetric paper supercapacitor based on the CNTs electrode showed higher specific capacitance 411 F g−1, compared to GNPs and graphene supercapacitors. Also by electrochemical impedance spectroscopy, the Nyquist curves of the symmetric paper supercapacitors have been plotted. For the symmetric paper supercapacitors based on the GNPs, graphene and CNTs electrodes the equivalent series resistance (ESR) resistance was 210 Ω, 96 Ω and 101 Ω respectively. The flexible symmetric paper supercapacitor based on BaTiO3/PVA/CNTs structure denotes a new type of the flexible supercapacitor that can be applied to the soft electronic.

No abstract

No abstract

In this study, two hydrogen sensors with Pd/SiO2/Si and Ni/SiO2/Si structures have been fabricated. Palladium nanoparticles are synthesized and then deposited on the oxide surface using spin coating. Capacitance–voltage curves for the Pd/SiO2/Si sensor at room temperature and for the Ni/SiO2/Si sensor at 140[Formula: see text]C in pure nitrogen and 1% H2–N2 mixture are described. The time required for reaching 90% of the steady-state signal magnitude ([Formula: see text]) for Pd/SiO2/Si capacitor was 1.4[Formula: see text]s and for Ni/SiO2/Si capacitor was 90 s. The time interval for recovery from 90% to 10% of steady-state signal magnitude ([Formula: see text] for Pd/SiO2/Si capacitor was 14[Formula: see text]s and for Ni/SiO2/Si capacitor was 40[Formula: see text]min. For the Pd/SiO2/Si capacitor, the response is 88% and for Ni/SiO2/Si capacitor the response is 29%. Comparison of Pd nanoparticles capacitive- and resistance-based sensors shows that the metal-oxide-semiconductor capacitive is faster and more sensitive than the resistance-based hydrogen gas sensors.

Background: Hydrogen sensors are micro/nano-structure that are used to locate hydrogen leaks. They are considered to have fast response/recovery time and long lifetime as compared to conventional gas sensors. In this paper, fabrication of sensitive capacitive-type hydrogen gas sensor based on Ni thin film has been investigated. The C-V curves of the sensor in different hydrogen concentrations have been reported.Method: Dry oxidation was done in thermal chemical vapor deposition furnace (TCVD). For oxidation time of 5 min, the oxide thickness was 15 nm and for oxidation time 10 min, it was 20 nm. The Ni thin film as a catalytic metal was deposited on the oxide film using electron gun deposition. Two MOS sensors were compared with different oxide film thickness and different hydrogen concentrations.Results: The highest response of the two MOS sensors with 15 nm and 20 nm oxide film thickness in 4% hydrogen concentration was 87.5% and 65.4% respectively. The fast response times for MOS sensors with 15 nm and 20 nm oxide film thickness in 4% hydrogen concentration was 8 s and 21 s, respectively.Conclusion: By increasing the hydrogen concentration from 1% to 4%, the response time for MOS sensor (20nm oxide thickness), was decreased from 28s to 21s. The recovery time was inversely increased from 237s to 360s. The experimental results showed that the MOS sensor based on Ni thin film had a quick response and a high sensitivity.

No abstract

In this work, a hydrogen capacitor nanosensor with palladium nanoparticles (PdNPs) electrode based on metal-oxide-semiconductor structure has been fabricated. The capacitor sensor has been fabricated on the n-type silicon substrate with an oxide film thickness of 50 nm. PdNPs are synthesised and then deposited on the oxide surface using spin coating. PdNPs are characterised using by transmission electron microscope and UV spectrum. Also, the morphology of the oxide surface is characterised using by atomic force microscope. The response time and recovery time of nanosensor have been explained at the room temperature. The time interval to 90% of the signal value for 1% H 2-N 2 mixture was 1.4 s and recovery time was 14 s. The curve of pressure as a function of hydrogen concentration (H/Pd) in the PdNPs and the mechanism of the nanosensor are reported. The capacitor nanosensor based on nanoparticles shows sensitive and fast response.

: In this paper, the supercapacitor based on the carbon nanotubes (CNTs) electrodes has been fabricated. The polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA) were used as a gel electrolyte. The electrodes and electrolytes thin films were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The specific capacitance (Cs) of the CNTs-based supercapacitor has been measured using the cyclic voltammetry and galvanostatic methods. For the scan rate, 20 mV s-1 the Cs of the CNTs-based supercapacitor was 173 F g-1. Using the electrochemical impedance spectroscopy the Nyquist curve has been plotted. The reactance capacitance and the equivalent series resistance of the CNTs-based supercapacitor with PVDF/PVA gel electrolytes were 90 Ω and 25 Ω respectively. Also, few patents to the CNTs-based supercapacitor have been reviewed and cited. The CNTs-based supercapacitor proposed a new structure solid-state and flexible supercapacitor with high performance.