28 research outputs found
Polyaniline/palladium nanohybrids for moisture and hydrogen detection.
Palladium nanoparticles display fascinating electronic, optical and catalytic properties, thus they can be used for various applications such as sensor fabrication. Conducting polymers such as polyaniline have also been widely used in sensor technology due to its cost effectiveness, versatility, and ease of synthesis. In this research, attention was given to unify the exceptional properties of these two materials and construct palladium nanoparticle coated polyaniline films to detect hydrogen and moisture. Electrochemical polymerization of aniline was carried out on gold sputtered epoxy resin boards. Polyaniline film was generated across a gap of 0.2Â mm created by a scratch made on the gold coating prior to electrochemical polymerization. A palladium nanoparticle dispersion was prepared using sonochemical reduction method and coated on to polyaniline film using drop-drying technique. Polyaniline only films were also fabricated for comparative analysis. Sensitivity of films towards humidity and hydrogen was evaluated using impedance spectroscopy in the presence of the respective species. According to the results, polyaniline films exhibited an impedance drop in the presence of humidity and the response was significantly improved once palladium nanoparticles were incorporated. Interestingly, polyaniline only films did not respond to hydrogen. Nevertheless, palladium nanoparticle coated polyaniline films exhibited remarkable response towards hydrogen
Light emission from corona discharge in SF
A spectroscopic investigation of corona discharges in SF6/N2 gas
mixtures has been undertaken using an optical multichannel analyser (OMA). A
point-to-plane geometry has been used with point radii varying from 3 to 10Â ÎĽm. Spectra are measured for high pressures ranging from 0.2Â MPa up to
1.4 MPa and for different concentrations of SF6 in the gas mixture. The
spectra in the 200–850 nm spectral range are mainly made of molecular bands,
which is indicative of a low temperature discharge. It has been noted that
SF6 emits in the region of 420Â nm to 510Â nm in positive and negative
polarities, although in negative polarity the emission is weaker. For
SF6/N2 mixtures, the main source of light emission is from
N2. The resultant spectra are used to evaluate the rotational Tr
and vibrational Tv temperatures of excited N2, Tr being
considered, due to the high pressure, to be equal to the kinetic temperature
Tkin in the corona discharge. Tr and Tv are determined by
comparing the experimental spectrum of the second positive system
( of N2
and the simulated one, which is obtained using a convolution method. As
expected, the results show that the measured rotational temperature Tr
increases steadily with the mean discharge current, while its increase with
gas pressure is less pronounced. The values of Tr are higher for the
positive corona discharge than the negative and also for mixtures having
higher amounts of SF6. In all conditions, we found
and Tv is less sensitive to the variation of the current
Factors that influence the surface potential decay on a thin film of polyethylene erephtalate
International audienc
Light emission from corona discharge in SF6 and SF6/N2 gas mixtures at high pressures
International audienc
Partial discharge in capacitor model at low temperature
International audienc
Influence de la nature du surfactant ionique sur la conduction Ă©lectrique de ses solutions dans le cyclohexane
According to the nature of additives, the electrical conduction of cyclohexane between plane, metallic electrodes is due for the most important part either to ions created by dissociation in the bulk of the liquid, or to ions appearing near one electrode (injection). This study about ionic additives of different kinds (ionophores, surface-active agents) shows that charged species with a large Stokes radius and then a large distance of minimum approach to the electrode do not produce an injection. This is relevant to additives similar to the surfactant Aerosol OT which forms inverted micelles for concentrations > 10-3 M in non-polar liquids.La conduction électrique du cyclohexane contenant différents additifs est, suivant la nature des composés, due à des ions créés pour la plus grande part soit dans le volume du liquide soit près d'une électrode (injection). L'étude de composés ioniques du type ionophore (TIAPi) ou tensio-actifs (Aérosol OT, DAP) montre que des espèces chargées de grand rayon de Stokes et donc de distance minimum d'approche élevée ne donnent pas lieu au phénomène d'injection. C'est le cas des additifs de la famille de l'Aérosol OT connus pour former des micelles inverses aux concentrations > 10-3 M dans les liquides non polaires
Partial Discharge in Capacitor Model at Low Temperature
The partial discharge plays an important role in the ageing and the rupture process of solid or mixed insulation systems. Ithas been recognized that the failure of this insulation can be joined to the presence of partial discharge often in inclusionssparkling. Liquid filled cavities can be considered as the most likely defects that can exist in capacitors. In this paper wedescribe the partial discharge evolution at low temperatures in all-PP film capacitors according to the time and the appliedvoltage. We distinguish two regimes of discharges for all the range of temperature and the low temperatures encourage thebreakdown of capacitors at weak voltage, we assign this phenomenon to the increase of the viscosity of filling liquid