Experimental investigation on the concentration and voltage effects on the characteristics of deposited magnesium–lanthanum powder

International audiencePhone: +33 248 484 065 Highlights x We synthetize Mg-La powders by means of an electrodeposition process. x We characterize Mg-La powders using EDS, SEM, XRD and FTIR techniques

Electrical and structural characterisation of plasma-polymerized TEOS thin films as humidity sensors

In this study, we used plasma polymerization of TEOS to deposit thin water molecule sensitive layers on two intredigitated aluminum electrodes evaporated on glass substrate. Electrical and structural analyses of the deposited sensitive layers have been evaluated through current-impedance responses and FTIR spectroscopy. The elaborated humidity resistive sensor exhibited a detectable response to relative humidity (RH) percentages ranging from 20 to 95%. The films showed good sensitivity to water molecule due to the presence of hydroxyl groups OH. These groups provide the adsorption sites for water and play an important role to the humidity sensor properties. The low impedance, good sensitivity as characterized by a linear change in impedance from 106 to 103 Ω over RH interval of 20–80% and low observed hysteresis of about 4%, make the elaborated layer a promising candidate for humidity sensors development.In this study, we used plasma polymerization of TEOS to deposit thin water molecule sensitive layers on two intredigitated aluminum electrodes evaporated on glass substrate. Electrical and structural analyses of the deposited sensitive layers have been evaluated through current-impedance responses and FTIR spectroscopy. The elaborated humidity resistive sensor exhibited a detectable response to relative humidity (RH) percentages ranging from 20 to 95%. The films showed good sensitivity to water molecule due to the presence of hydroxyl groups OH. These groups provide the adsorption sites for water and play an important role to the humidity sensor properties. The low impedance, good sensitivity as characterized by a linear change in impedance from 106 to 103 Ω over RH interval of 20–80% and low observed hysteresis of about 4%, make the elaborated layer a promising candidate for humidity sensors development

THERMAL PERFORMANCE OF FLAT PLATE SOLAR COLLECTOR

In this paper, a theoretical and experimental studyof flat platesolar water collector with reflectors.A mathematical model based on energy balance equations saw the thermal behavior of the collector is investigated. The experimental test was made at the unit research applies in renewable energy (URAER) located in southern Algeria.An increase of 23% for solar radiation incident on the collector surface with the addition of the planers reflectors in the day of May, this increase causes an improvement of the performance of the collector,the fluid temperature increases with an average of 5%. Thetests conducted on the flat plate solar water collector in open circuit enabled the determination of thermal performance of the collector by estimating the daily output The thermal efficiency of the collector ranges from 1% -63% during the day, a mean value of 36%obtained

Thin plasma-polymerized layers of hexamethyldisiloxane for humidity sensor development

International audienceThe response of resistive-type sensors based on thin hexamethyldisiloxane layers to relative humidity (RH) was evaluated. Humidity sensitive layers were plasma polymerized at low frequency glow discharge using a capacitively coupled parallel plate reactor. The sensor design comprises the absorbing layer deposited on clean glass substrate with comb-shape aluminum electrodes (interdigitated structure). The change in electrical impedance of the sensing film was monitored as the device was exposed to humidity. The variation of the plasma-polymerization parameters resulted in different humidity sensing properties which could be correlated to the results of Fourier transform infrared spectroscopy (FTIR). The deposited films exhibited a detectable response to RH ranging from 30 to 95% with low hysteresis, good reproducibility and stability in long-term use. Films with a greater thickness showed a significant decrease in the humidity sensing capability. FTIR analysis revealed the presence of SiH bonding groups, which are frequently linked to the film density. The increase in the plasma discharge power induced also a significant decrease in the diffusion process of water vapor inside the sensitive layer bulk

Effect of voltage on the characteristics of magnesium-lanthanum deposits synthesized by an electrodeposition process

International audienceThis work deals with the characterization of magnesium-lanthanum powders deposits produced with an electrodeposition technique using an aqueous solution based on magnesium chloride and lanthanum(III) nitrate. In recent years, the interest for magnesium-based alloys is growing due to their potential use as solid state systems for hydrogen storage. This work is a preliminary study on the synthesis of magnesium-lanthanum powders oriented to their later evaluation in systems for hydrogen storage. Magnesium and Lanthanum are deposited on a copper plate used as a cathode. Chemical composition, structure and morphology are investigated by EDS, XRD, FTIR and SEM. The effect of voltage on powders characteristics is studied considering three values (3, 3.5 and 4 V). EDS analysis shows the presence of three major elements (Mg, La and O) with a little amount of Cl. The weight percentages of Mg and O increase whereas the one of La decreases with the growth of voltage. Morphological characterization reveals that heterogeneous chemical structures are formed on the surface of the electrode and the size of aggregates decreases with the increase of voltage. From the results of X-ray analysis the deposits reveal the significant presence of two phases: Mg(OH)2 and La(OH)3. The peaks originating from the Mg(OH)2 phase has a non-monotonic behavior and those of La(OH)3 phase increase with the increase of voltage. FTIR analysis confirms the presence of the two phases identified in XRD diffractograms and exhibits that their corresponding transmittance values increase for higher voltage values