Thermal conductivity and thermal boundary resistance of nanostructures

International audienceWe present a fabrication process of low-cost superlattices and simulations related with the heat dissipation on them. The influence of the interfacial roughness on the thermal conductivity of semiconductor/semiconductor superlattices was studied by equilibrium and non-equilibrium molecular dynamics and on the Kapitza resistance of superlattice's interfaces by equilibrium molecular dynamics. The non-equilibrium method was the tool used for the prediction of the Kapitza resistance for a binary semiconductor/metal system. Physical explanations are provided for rationalizing the simulation results

ETUDE ELECTROCHIMIQUE DE L’INHIBITION DU PROCEDE D’ENTARTRAGE DANS UNE EAU DE MER

Calcareous scaling on domestic and industrial equipments generates severe problems and causes drastic economic loss. The use of several chemicals is a common technique to impede the scale deposition. The subject of this study is the inhibition of the scaling process. Thus, we have followed the coverage of a titanium electrode, in absence and in presence of two anti-scale products, using the chronoamperometry. The mineral scales were characterized by electrochemical impedance spectroscopy (EIS) and analyzed by electronic sweeping microscopy (ESM). It was found that 25 ppm of hydroxyl-2 méthyl-4 benzylphosponic acide (AHMBP) or of Diprochim anti-scale is sufficient to prevent electrodeposition. The efficiency of the two chemicals is comparable.L’entartrage des installations domestiques ou industrielles cause de sévères problèmes techniques et économiques. La technique la plus courante utilisée pour ralentir cette déposition consiste à utiliser divers inhibiteurs chimiques. L’objectif de cette étude rentre dans ce cadre. En effet, nous avons suivi par chronoampérométrie, l’évolution du recouvrement d’une électrode en titane, en absence et en présence de deux inhibiteurs d’entartrage. Les dépôts formés sont caractérisés par la spectroscopie d’impédance électrochimique (SIE) et analysés par microscopie électronique à balayage (MEB). 25 ppm de l’acide hydroxy-2 méthyl-4 benzylphosponique (AHMBP) ou de l’antitartre Diprochim suffisent pour ralentir considérablement le recouvrement de l’électrode. L’efficacité des deux inhibiteurs utilisés est comparable

A new highly sensitive micro-sensor for the ultra-traces analysis of paracetamol directly in water

International audienceIn the present work, a simple, inexpensive and highly sensitive electrochemical micro-sensor was developed for trace detection of paracetamol (PAR) directly in water, using electrochemical preconcentration technique (EP) on a cavity microelectrode modified with carbon black nanoparticles (nCB/ CME). The results demonstrate that with an EP of PAR on nCB/ CME at 0 V for 900 s in BRS 0.04 M at pH = 7, the new proposed micro-sensor show two large linear response in ranges of 5 × 10-10 to 9 × 10-8 mol.L-1 and from 1 × 10-7 to 1 × 10-6 mol.L-1. The detection and quantification limits are estimated to be 1.4 × 10-10 and 4.3 × 10-10 mol.L-1, respectively. The performances of the new proposed nCB/ CME for the determination of PAR were compared to its performances without EP and the results reveal the importance of the application of EP in improving the electroanalytical characteristics. The applicability of the designed micro-sensor was successfully applied for the direct analysis of local tap water and treated wastewater samples spiked with trace PAR compounds with a satisfactory recovery (less than 4 %) and a relation standard deviation less than 5 %. It indicates that the electrochemical micro-sensors are an effective device for monitoring PAR concentrations directly in water without any pretreatment. © 2022 Elsevier B.V

Fullerene-MWCNT nanostructured-based electrochemical sensor for the detection of Vanillin as food additive

International audienceIn this paper, a simple, economical, selective and sensitive electrochemical sensor is proposed for the quantification of vanillin (VAN) in real food samples. It consists of a carbon paste electrode (CPE) nanostructured with Fullerene (FNTs) and functionalized multi-walled carbon nanotubes (f-MWCNTs). The developed electroanalytical method was performed with cyclic voltammetry after optimization of operating conditions, such as supporting electrolytes, pH values and accumulation time. After optimization, the nanostructured sensor showed wide linear responses in the range from 5 × 10−8 to 9 × 10-6 mol.L-1 for VAN trace levels and from 10-5 to 10-4 mol.L-1 for higher concentrations, with a low detection limit of 3.4 × 10−8 mol.L-1. For concentrations lower than 10-5 mol.L-1, VAN was stripped after a previous quick adsorption step (300 s). The f-MWCNTs-FNTs/CPE sensor showed a good stability, repeatability and reproducibility (less than 7 %). This nanostructured sensor was successfully applied to determine VAN concentration as additive in commercial vanilla sugar samples with a satisfactory recovery and a good accuracy (andlt; 6.5 %) in comparison with UPLC/UV control method

Study of the antideposit effect of 2-Hydroxy-4-methylbenzylphosphonic acid

The scale inhibitor, 2-hydroxy-4-methylbenzylphosphonic acid (HMBP) appears efficient for desalination plants of sea water. A concentration of 26.5 ppm (131 μmol/L) prevents the calcareous magnesium deposits. The anti-scale effect of this inhibitor is achieved by chronoamperometry at imposed potential and complex impedance. SEM allows observation of the calcareous magnesium deposits with and without inhibitor 2-hydroxy-4-methylbenzylphosphonic acid (HMBP

Differential Optical Spectrometer based on Critical Angle Dispersion

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Structural, magnetic and magnetocaloric properties of nanostructured Pr 0.5 Sr 0.5 MnO 3 manganite synthesized by mechanical alloying

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Structural disorder effect on the structural and magnetic properties of Pr0.4Re0.1Sr0.5−yBayMnO3 manganites (Re = Pr, Sm, Eu, Gd, Dy and Ho)

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