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 0.2 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

Preparation of Hydrogen Permeable Membrane Using Nanoparticles Electrophoresis Technique

Hydrogen perm-selective membranes composed of Pd nanoparticles were investigated. The nanoparticles were prepared by ultrasonic reduction from PdII ions, and then deposited on a substrate disc with electrophoresis technique. These electrophoretic membranes have shown high performance of perm-selectivity for H2 with separation factor α = 3.85, under room temperature

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 10 μm. Spectra are measured for high pressures ranging from 0.2 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 420 nm to 510 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 ($C^{3}\Pi_{u}\to B^{3}\Pi_{g})$ 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 $T_{v}>T_{r}$ and Tv is less sensitive to the variation of the current

Elaboration and characterization of mullite-anorthite-albite porous ceramics prepared from Algerian kaolin

Abstract Mullite-anorthite-albite porous ceramic materials were successfully prepared by a solid-state reaction between kaolin clay and two different additives (CaCO3 and Na2CO3). The starting raw material was characterized by X-ray fluorescence, X-ray diffraction (XRD) and dynamic light scattering techniques. The effect of CaCO3 and Na2CO3 concentration (10 to 70 wt%) on structure, morphology and thermal properties of the obtained ceramics was investigated by XRD, scanning electron microscopy and differential scanning calorimetry (DSC) techniques. The XRD patterns showed that mullite (3Al2O3.2SiO2), anorthite (CaO.Al2O3.2SiO2) and albite (Na2O.Al2O3.6SiO2) were the main crystalline phases present in the materials. The morphology investigation revealed the porous texture of obtained ceramics characterized by the presence of sponge-like structure mainly due to the additive decomposition at high temperatures. The DSC results confirm the presence of four temperature regions related to the kaolin thermal transformations and the formation of minerals. The temperature and enthalpy of mineral formation are additive concentration dependent. As a result, the optimal content of additives which allowed the coexistence of the three phases, a sponge-like morphology, and high porosity without cracks corresponded to 15 wt% CaCO3, 15 wt% Na2CO3, and 70 wt% kaolin

Injection d'ions dans le cyclohexane entre électrodes recouvertes de couches minces isolantes

The electrical conduction of electrolyte solutions in cyclohexane has been studied between metal electrodes coated with thin films of alumina or polyphenyleneoxide. The ionic injection observed at short times after the application of a voltage step presents the same characteristics as the one previously studied between metallic electrodes (same field dependence, same variation with the liquid conductivity). We conclude that the injected ions are the ions of the electrolyte and are created in the region of image-force in the liquid. After a long application of the voltage, the coating which has blocked the ions of the electrolyte, behaves as a strong injector of ions in the liquid.La conduction de solutions d'électrolytes dans le cyclohexane a été étudiée entre électrodes recouvertes de films d'alumine ou de polyphénylène-oxyde lors de l'application d'un échelon de tension continue. L'injection faible observée aux temps courts dans les solutions de TlAPi a les mêmes caractéristiques qu'entre électrodes métalliques nues (même variation avec le champ, avec la conductivité de la solution). Les ions injectés sont les ions de l'électrolyte, ils sont créés dans la zone de force-image. Aux temps longs le film qui bloque les ions du liquide, devient un injecteur très fort d'ions dans le liquide. La nature de ces ions n'a pas été déterminée

Light emission from corona discharge in SF6 and SF6/N2 gas mixtures at high pressures

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Influence de la nature du surfactant ionique sur la conduction électrique 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