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

ETUDE DE L'INJECTION D'IONS DANS LES LIQUIDES DIELECTRIQUES PAR MODIFICATION DES PROPRIETES VOLUMIQUES ET INTERFACIALES

This work deals with the study of the parameters involved in the ion injection mechanism by an electrode in a non-polar liquid. This mechanism takes into account the action of the image force at the interface and the resulting ion distribution. The applica¬tion of an electric field lowers the potential barrier and causes an injection of ions without significantly changing the charge reservoir at the interface. The parameters studied were the temperature, the nature of the additives and the nature of the electrodes.The variations of the injection current as a function of temperature are consistent with the proposed mechanism and confirm the presence of a high ion density at the interface, subjected only to electrostatic forces.We have found that only nonpolar liquids containing ionic surfactants known for their micellar properties do not give rise to this phenomenon of injection. We attributed this to the kinetics, in this slow case, of the mechanism of ion creation at the interface.We also studied the influence on the injection of insulating layers deposited on the metal electrodes. The studied layers (Al 2 O 3 in polyphenylene oxide) were obtained by electrochemical techniques. At short times, the observed injection is not modified by the deposition, which confirms that the creation of ions takes place in the liquid. At long times, on the other hand, the deposit may be an injector stronger than the metal.Ce travail porte sur l'étude des paramètres intervenant dans le mécanisme d'injection d'ions par une électrode dans un liquide non-polaire. Ce mécanisme tient compte de l'action de la force-image à l'interface et de la distribution ionique qui en résulte. L'applica¬tion d'un champ électrique abaisse la barrière de potentiel et provoque une injection d'ions sans modifier de façon notable le réservoir de charges à l'interface. Les paramètres étudiés ont été la température, la nature des additifs et la nature des électrodes.Les variations du courant d'injection en fonction de la tempéra¬ture sont conformes au mécanisme proposé et confirment la présence d'une densité ionique élevée à l'interface, soumise uniquement à des forces électrostatiques.Nous avons constaté que seuls les liquides non polaires contenant des surfactants ioniques connus pour leurs propriétés micellaires ne donnent pas lieu à ce phénomène d'injection. Nous l'avons attribué à la cinétique, dans ce cas lente, du mécanisme de création d'ions à 1'inxerface.Nous avons aussi étudié l'influence sur l'injection de couches isolantes déposées sur les électrodes métalliaues. Les couches étudiées (Al„0_ en Foiyphénylène oxyde) ont été obtenues par des techniques électrochimiques. Aux temps courts, l'injection observée n'est pas modifiée par le dépôt, ce qui confirme que la création d'ions a lieu dans le liquide. Aux temps longs, par contre, le dépôt peut être un injecteur plus fort que le métal

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

Hyperfine interactions and structural features of Fe–44Co–6Mo (wt.%) nanostructured powders

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