ABSTRACT The present study investigates the effects of the substitution of iron in the B-site on ... more ABSTRACT The present study investigates the effects of the substitution of iron in the B-site on the magnetic and magnetocaloric properties of the new brownmillerite LaSrMn2O5 powder. Our samples were synthesized using the conventional solid state reaction at high temperature. Magnetization measurements versus temperature in an applied magnetic field of 0.05 T indicated that the samples underwent a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature T C decreased with more substitution of iron content. Arrott plots showed that all samples exhibited a second order magnetic phase transition. Magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. A large magnetocaloric effect was observed for x =0.1 and x =0.2 samples. The maximum magnetic entropy changes, |ΔSMMax|, obtained were 0.7 J kg−1 K−1 and 0.75 J kg−1 K−1 in magnetic field change of 5 T for x=0.1 and x=0.2, respectively.
Abstract This study describes the synthesis and characterization of Cu-doped ZnO nanorods (NRs) b... more Abstract This study describes the synthesis and characterization of Cu-doped ZnO nanorods (NRs) by an electrochemical method in the presence of two different Cu precursor (Cu+2 and Cu+) in order to improve photocurrent generation. Analyses of the resulting materials by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis and electrochemical photocurrent (ECP) spectroscopy confirm the formation of well-aligned ZnO Wurtzite nanostructures in the form of hexagonal rods. For both doping source with a concentration of up to 0.5%, the following changes were observed: a distortion of the ZnO morphology, an increase in transmittance to 96% for ZnO doped with Cu+2, and a reduction of the energy gap from 3.36 eV to 3.06 and 3.02 eV for ZnO doped with Cu+2 and Cu+, respectively. From photoelectrochemical tests, the photo-current density was improved up to 0.05 mA.cm-2 in the presence of Cu doping, which is twelve times superior to that of undoped ZnO nanorods, which means that the incorporation of Cu+2 or Cu+ significantly improves the separation efficiency of photogenerated electron-hole pairs. These results can be considered promising for optoelectronic and photocatalysis applications.
ABSTRACT This work presents the construction of an ethanol microfluidic biofuel cell based on a b... more ABSTRACT This work presents the construction of an ethanol microfluidic biofuel cell based on a biocathode and a bioanode, and operating in a Y-shaped microfluidic channel. At the anode, ethanol was oxidized by alcohol dehydrogenase, whereas at the cathode, the oxygen was reduced by laccase. Fuel and oxidant streams moved in parallel laminar flow without turbulent mixing into a microchannel fabricated using soft lithography methods. The enzymes were immobilized in the presence of reactive species at gold electrode surfaces. Bioelectrocatalytic processes were enhanced by combination of enzymes and carbon nanoparticles, attributed to appropriate electron transport and high amount enzyme loading. The benefit of the nanoparticles with higher surface porosity was explained by the high porous structure that offered a closer proximity to the reactive species and improved diffusion of the substrates within the enzyme films. The microfluidic BFC was optimized as function of electrode patterns, showing that higher current and power densities were achieved for shorter and wider electrodes that allow for thinner boundary layer depletion at the electrodes surface resulting in efficient catalytic consumption of fuel and oxidant. This miniaturized device generated maximum power density of 90 μW cm−2 at 0.6 V for a flow rate 16 μL min−1.
Les biopiles representent une solution attractive et ambitieuse pour developper des systemes alte... more Les biopiles representent une solution attractive et ambitieuse pour developper des systemes alternatifs de conversion d'energie. Ce travail decrit la construction d'une biopile a ethanol/O2 (oxydation de l'ethanol a l'anode et reduction de l'oxygene a la cathode) avec des electrodes tridimensionnelles possedant une surface specifique elevee. Le point de depart a ete la fabrication et l'optimisation de bioelectrodes enzymatiques par immobilisation d'enzymes et de mediateurs sur des nanofibres de polyacrylonitrile, preparees par la methode d'electrospinning, et recouvertes d'or. Ces bioelectrodes a base de nanofibres (biocathode et bioanode) ont ete assemblees pour construire et caracteriser une biopile a ethanol/O2 qui a fourni une densite de puissance de 1600 µW/cm2 par la methode de polarisation et 210 µW/cm2 par imposition de resistances au systeme. Enfin, nous avons decrit la fabrication de la premiere biopile miniaturisee a ethanol/oxygene av...
This work presents the construction of an ethanol microfluidic biofuel cell (MBFC) based on bioel... more This work presents the construction of an ethanol microfluidic biofuel cell (MBFC) based on bioelectrodes and operating in aY-shaped microfluidic channel. At the cathode, the oxygen is reduced by laccase, whereas at the anode, ethanol is oxidized by alcohol dehydroge- nase. The enzymes were immobilized in the presence of reactive species at gold electrode surfaces. Oxidant and Fuel streams move in parallel laminar flow without turbulent mixing into a microchannel. The benefit of the carbon nanoparticles with higher surface porosity was explained by the high porous structure that offered a closer proximity to the reactive species and improved diffusion of ethanol and oxygen within the enzyme films. The highercurrent and power densities were achieved for shorter and wider electrodes that allow for thinner boundary layer depletion at the electrodes surface resulting in efficient catalytic consumption of fuel and oxidant. This miniaturized device generated maximum power density of 90 μW...
This paper describes our interest on the ethanol separation and the enhancement of the obtained i... more This paper describes our interest on the ethanol separation and the enhancement of the obtained interaction parameters. The binodal curves and tie-lines data for the ternary systems (Water +Ethanol + 1-Octanol), (Water + Ethanol +4-Methyl-2-pentanone) and (Water + Ethanol + Ethyl Acetate) at 293.15K were investigated. These ternary systems follow a type-1 Liquid-Liquid equilibrium diagram. Furthermore, the extraction capabilities of these solvents in this study were tested using the separation factor (S) which was found greater than 1 in all ternary systems (S varying between 3.52 and 18.37). Besides, the values of the distribution coefficient (D) of ethanol were also not constant over the entire composition of the two-phase region (D values varied between 0.777 and 0.928), which confirms the extraction of ethanol. The ternary system (Water + Ethanol + Ethyl Acetate) was found to be the best option in terms of the distribution coefficient and separation factor. Othmer-Tobias and Han...
ABSTRACT The present study investigates the effects of the substitution of iron in the B-site on ... more ABSTRACT The present study investigates the effects of the substitution of iron in the B-site on the magnetic and magnetocaloric properties of the new brownmillerite LaSrMn2O5 powder. Our samples were synthesized using the conventional solid state reaction at high temperature. Magnetization measurements versus temperature in an applied magnetic field of 0.05 T indicated that the samples underwent a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature T C decreased with more substitution of iron content. Arrott plots showed that all samples exhibited a second order magnetic phase transition. Magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. A large magnetocaloric effect was observed for x =0.1 and x =0.2 samples. The maximum magnetic entropy changes, |ΔSMMax|, obtained were 0.7 J kg−1 K−1 and 0.75 J kg−1 K−1 in magnetic field change of 5 T for x=0.1 and x=0.2, respectively.
Abstract This study describes the synthesis and characterization of Cu-doped ZnO nanorods (NRs) b... more Abstract This study describes the synthesis and characterization of Cu-doped ZnO nanorods (NRs) by an electrochemical method in the presence of two different Cu precursor (Cu+2 and Cu+) in order to improve photocurrent generation. Analyses of the resulting materials by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis and electrochemical photocurrent (ECP) spectroscopy confirm the formation of well-aligned ZnO Wurtzite nanostructures in the form of hexagonal rods. For both doping source with a concentration of up to 0.5%, the following changes were observed: a distortion of the ZnO morphology, an increase in transmittance to 96% for ZnO doped with Cu+2, and a reduction of the energy gap from 3.36 eV to 3.06 and 3.02 eV for ZnO doped with Cu+2 and Cu+, respectively. From photoelectrochemical tests, the photo-current density was improved up to 0.05 mA.cm-2 in the presence of Cu doping, which is twelve times superior to that of undoped ZnO nanorods, which means that the incorporation of Cu+2 or Cu+ significantly improves the separation efficiency of photogenerated electron-hole pairs. These results can be considered promising for optoelectronic and photocatalysis applications.
ABSTRACT This work presents the construction of an ethanol microfluidic biofuel cell based on a b... more ABSTRACT This work presents the construction of an ethanol microfluidic biofuel cell based on a biocathode and a bioanode, and operating in a Y-shaped microfluidic channel. At the anode, ethanol was oxidized by alcohol dehydrogenase, whereas at the cathode, the oxygen was reduced by laccase. Fuel and oxidant streams moved in parallel laminar flow without turbulent mixing into a microchannel fabricated using soft lithography methods. The enzymes were immobilized in the presence of reactive species at gold electrode surfaces. Bioelectrocatalytic processes were enhanced by combination of enzymes and carbon nanoparticles, attributed to appropriate electron transport and high amount enzyme loading. The benefit of the nanoparticles with higher surface porosity was explained by the high porous structure that offered a closer proximity to the reactive species and improved diffusion of the substrates within the enzyme films. The microfluidic BFC was optimized as function of electrode patterns, showing that higher current and power densities were achieved for shorter and wider electrodes that allow for thinner boundary layer depletion at the electrodes surface resulting in efficient catalytic consumption of fuel and oxidant. This miniaturized device generated maximum power density of 90 μW cm−2 at 0.6 V for a flow rate 16 μL min−1.
Les biopiles representent une solution attractive et ambitieuse pour developper des systemes alte... more Les biopiles representent une solution attractive et ambitieuse pour developper des systemes alternatifs de conversion d'energie. Ce travail decrit la construction d'une biopile a ethanol/O2 (oxydation de l'ethanol a l'anode et reduction de l'oxygene a la cathode) avec des electrodes tridimensionnelles possedant une surface specifique elevee. Le point de depart a ete la fabrication et l'optimisation de bioelectrodes enzymatiques par immobilisation d'enzymes et de mediateurs sur des nanofibres de polyacrylonitrile, preparees par la methode d'electrospinning, et recouvertes d'or. Ces bioelectrodes a base de nanofibres (biocathode et bioanode) ont ete assemblees pour construire et caracteriser une biopile a ethanol/O2 qui a fourni une densite de puissance de 1600 µW/cm2 par la methode de polarisation et 210 µW/cm2 par imposition de resistances au systeme. Enfin, nous avons decrit la fabrication de la premiere biopile miniaturisee a ethanol/oxygene av...
This work presents the construction of an ethanol microfluidic biofuel cell (MBFC) based on bioel... more This work presents the construction of an ethanol microfluidic biofuel cell (MBFC) based on bioelectrodes and operating in aY-shaped microfluidic channel. At the cathode, the oxygen is reduced by laccase, whereas at the anode, ethanol is oxidized by alcohol dehydroge- nase. The enzymes were immobilized in the presence of reactive species at gold electrode surfaces. Oxidant and Fuel streams move in parallel laminar flow without turbulent mixing into a microchannel. The benefit of the carbon nanoparticles with higher surface porosity was explained by the high porous structure that offered a closer proximity to the reactive species and improved diffusion of ethanol and oxygen within the enzyme films. The highercurrent and power densities were achieved for shorter and wider electrodes that allow for thinner boundary layer depletion at the electrodes surface resulting in efficient catalytic consumption of fuel and oxidant. This miniaturized device generated maximum power density of 90 μW...
This paper describes our interest on the ethanol separation and the enhancement of the obtained i... more This paper describes our interest on the ethanol separation and the enhancement of the obtained interaction parameters. The binodal curves and tie-lines data for the ternary systems (Water +Ethanol + 1-Octanol), (Water + Ethanol +4-Methyl-2-pentanone) and (Water + Ethanol + Ethyl Acetate) at 293.15K were investigated. These ternary systems follow a type-1 Liquid-Liquid equilibrium diagram. Furthermore, the extraction capabilities of these solvents in this study were tested using the separation factor (S) which was found greater than 1 in all ternary systems (S varying between 3.52 and 18.37). Besides, the values of the distribution coefficient (D) of ethanol were also not constant over the entire composition of the two-phase region (D values varied between 0.777 and 0.928), which confirms the extraction of ethanol. The ternary system (Water + Ethanol + Ethyl Acetate) was found to be the best option in terms of the distribution coefficient and separation factor. Othmer-Tobias and Han...
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