Chimie

Nombre total de résultats : 172
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Formulation et caractérisation des matériaux biodégradables à base de l’acide polylactique-Plastifiants

MAIZA Mounira (2016)
Thèse de doctorat

In this study, the characterization of plasticized PLA with TEC and ATBC by melt blending method wasreported. The value of the melt flow index (MFI) observed for all samples are higher than those of neat PLA.The evaluation of the influence of the type and plasticizer content on the viscoelastic properties of PLA withDMA indicates a decrease in the storage modulus for plasticized PLA, indicating the flexibility and mobility ofthe amorphous phase of PLA caused by TEC and ATBC. UV-Visible spectroscopy shows that the twoplasticizers: TEC and ATBC have no effect on the color change of the films. The opacity values of the PLAfilms plasticized with TEC and ATBC were slightly lower than the value of the treated PLA film. X-raydiffraction shows the appearance of a strong diffraction at 16.7° assigned to the crystalline phase α, whichconfirms that the PLA has no crystalline polymorph transition. FTIR spectra indicate that there are somemolecular interactions by intermolecular hydrogen bonds between PLA and citrate ester. The thermal propertiesof plasticized PLA shows that TEC and ATBC are effective in lowering the glass transition temperature (Tg), themelting temperature (Tm) and the cold crystallization temperature (Tcc) of the PLA. In addition, its crystallinityincreases with increasing content of plasticizer. The TGA results indicated that the TEC and ATBC promote adecrease in thermal stability of the PLA. The weight loss plasticizer with heating time and at 100 °C is lesserthan at 135 °C. Leaching of TEC and ATBC results in cracks and changed color of material. The tensile testshowed that the formulations of the plasticized PLA with citrate ester (TEC and ATBC) give better mechanicalproperties by providing treated PLA. The observation by SEM confirmed there is miscibility between the PLAand plasticizer. Finally it can be said that the higher molecular weight of citrate exhibited a greater plasticizingeffect. Voir les détails

Mots clés : Polylactic acid (PLA), plasticizing, Triethyl Citrate (TEC), Acetyl Tributyl Citrate (ATBC)

Characterization of toughened Poly (lactic acid) PLA/ Polycaprolactone (PCL) with bio-plasticizers (TEC and PEG3)

M. Maiza, A. HAMAM  (2019)
Article de conférence

Triethyl citrate (TEC) and poly (ethylene glycol) (PEG3) were used as plasticizer for Polylactic acid (PLA)/ polycaprolactone (80PLA/20PCL) blends. The treated and plasticized 80PLA/20PCL blends at various concentrations of plasticizers were analyzed were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), Differential scanning calorimetry was used to evaluate the crystallinity and thermal property of all the samples. It was found that the glass transition temperature (Tg) and the melting temperature (Tm) decreased as the amount of plasticizers increased. Additionally, the presence of TEC or PEG3 tended to increase the crystallinity of PLA. DMA of plasticized PLA indicates that a decrease in Tg is obtained with increasing plasticizer content, Plasticizing effect was also shown by decrease in the dynamic storage modulus and viscosity of plasticized mixtures compared to the treated 80PLA/20PCL blends. The TGA results indicated that PEG3 and TEC promoted a decrease in thermal stability of the 80PLA/20PCL. Voir les détails

Mots clés : Poly lactic acid (PLA), Polycaprolactone (PCL), Plasticizers vegetable, Biodegradable

Enhancement of photoelectrochemical and optical characteristics using a TiO2 nanoparticles interlayer in MEH-PPV heterojunction devices

F Habelhames, M Girtan, A Manole, L LAMIRI, W Zerguine, B Nessark  (2012)
Publication

In this work, MEH-PPV+TiO 2 composite material was prepared by incorporation of titanium oxide nonoparticles (TiO 2) into poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) polymer matrix and deposited by spin coating on glass and indium thin oxide (ITO) substrates. The absorbance of various MEH-PPV composites incorporating different concentrations of TiO 2 nanoparticles shows that addition of TiO 2 improves absorption of the composites. TiO 2 and the conjugated polymer have absorption in the UV and visible regions, respectively. As a result, the composite has slightly broader absorption. In addition, absorption of the composite shows that the polymer induces a certain structuring, as evidenced by the presence of fine structures. The effect of inserting a TiO 2 nanoparticles interlayer in the MEH-PPV polymer heterojunction device on the photoelectrochemical and optical characteristics of the device has been studied. The modified device (MEH-PPV+TiO 2) shows improved photocurrent density characteristics, and increased with TiO 2 concentration. The study showed that the presence of inorganic semiconductor nonoparticles (TiO 2) in polymer film improves the optical and the photovoltaic properties of MEH-PPV, and was designed to explore new approaches to improve light-collection efficiency in polymer photovoltaic. Voir les détails

Mots clés : Hybrid composite materials, MEH-PPV, morphology, photocurrent

Growth and characterization of electrodeposited Cu2O thin films

S. Laidoudi, A.Y. Bioud, A. Azizi, G. Schmerber, J. Bartringer, S. Barre, A. Dinia  (2013)
Publication

This work demonstrates the electrodeposition of cuprous oxide (Cu2O) thin films onto a fluorine-doped tin oxide (FTO)-coated conducting glass substrates from Cu(II) sulfate solution with C6H8O7 chelating agent. During cyclic voltammetry experiences, the potential interval where the electrodeposition of Cu2O is carried out was established. The thin films were obtained potentiostatically and were characterized through different techniques. From the Mott–Schottky measurements, the flat-band potential and the acceptor density for the Cu2O thin films are determined. All the films showed a p-type semiconductor character with a carrier density varying between 2.41 × 1018 cm−3 and 5.38 × 1018 cm−3. This little difference is attributed to the increase of the stoichiometric defects in the films with the deposition potential. Atomic force microscopy analysis showed that the Cu2O thin films obtained at high potential are more homogenous in appearance and present lower crystallites size. X-ray Voir les détails

Mots clés : Cu2O, electrodeposition, Mott–Schottky, optical properties, Thin films, XRD

Electrochemical and spectroscopic characterization of poly (bithiophene + 2-methylfuran) copolymer.

Leila LAMIRI, Belkacem Nessark, Farid Habelhames, Lakhdar Sibous  (2017)
Publication

In this work, Poly(bithiophene + 2-methylfuran) copolymer is successfully achieved by an electrochemical polymerization of two monomers, bithiophene and 2-methylfuran in acetonitrile containing lithium perchlorate. The resultant copolymer was characterized via cyclic voltammetry, impedance spectroscopy, UV-visible, scanning electron microscope, conductivity and photocurrent measurements. The cyclic voltammetry study showed two redox couples characteristic of Poly (bithiophene + 2-methylfuran) copolymer. The impedance spectroscopy study revealed that the resistance of the copolymer ?lm increases with the addition of 2-methylfuran. The photocurrent measurement showed good photoelectrochemical properties, making this copolymer an ideal candidate for photovoltaic cell applications. Voir les détails

Mots clés : Electrochemical polymerization, copolymer, polybithiophene, poly2-methylfuran, morphology, photo-electrochemical properties.

Electrochemical behavior, characterization and corrosion protection properties of poly(bithiophene + 2-methylfuran) copolymer coatings on A304 stainless steel

Leila LAMIRI, Belkacem  (2018)
Publication

Polybithiophene (PBTh), poly(2-methylfuran) (PMeFu) and poly(bithiophene + 2-methylfuran) noted poly(BTh + MeFu) copolymer films were synthesized by electrochemical deposition on 304-stainless steel, from an acetonitrile (ACN) solution containing 10−2 m bithiophene, 10−2 m 2-methylfuran and 10−1 m lithium perchlorate (LiClO4), by cyclic voltammetry (CV) between 0 V and 2 V vs. SCE, with a scan rate of 50 mV · s−1. The copolymers coated were studied in a corrosive sulfuric acid medium (H2SO4 1 N) using the potensiodynamique polarization method and the electrochemical impedance spectroscopy (EIS). Copolymers coated characterization was performed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The polarization curves show that the copolymer film formed on A304, shifts the corrosion potential towards more positive potentials. The presence of the poly(BTh + MeFu) improves the corrosion resistance of the metal in a corrosive medium, H2SO4. This protection against corrosion is caused by the barrier effect of the layer of copolymer, which covers the surface of the A304 stainless steel against the aggressive ions of the corrosive medium. Voir les détails

Mots clés : 2-methylfuran, bithiophene, copolymers, protection against corrosion, stainless steel.

Optical and Photo-electrochemical characterization of manganese dioxide/polypyrrole nanocomposite

Assia Tounsi, Chrif Dehchar, Samiha LAIDOUDI, Ouafia BELGHERBI, Belkacem Nessark, Farid Habelhames  (2019)
Article de conférence

PPy-coated manganese dioxide (PPy-MnO2) synthesized by depositing PPy on the surface of γ-MnO2 particles in acetonitrile solution containing 10-1M lithium perchlorate (LiClO4) containing a monomer (pyrrole) and semiconductor (MnO2) nanoparticles. The composite materials (MnO2-PPy/ITO) were characterized by different methods including cyclic voltammetry, impedance spectroscopy, chronoamperometry, scanning electron microscopy (SEM). The cyclic voltammogram showed one redox couple characteristic of the oxidation and reduction composite material of composite material. The impedance spectroscopy study showed that the resistance of the film increases with the MnO2 incorporated in the polymer. The morphological analysis of the film surfaces showed that the MnO2 nanoparticle increased the roughness. These results give information on the use possibility of these materials for energy storage and as photovoltaic cells applications. Voir les détails

Mots clés : Manganese dioxide, Polypyrrole, electrodeposition, optical proprieties.

OPTICAL, STRUCTURAL AND MORPHOLOGICAL CHARACTERIZATION OF ELECTRODEPOSITED CUPROUS OXIDE THIN FILMS: EFFECT OF DEPOSITION TIME

Samiha LAIDOUDI, Mohamed Redha Khelladi, Charif DEHCHAR, Samah BOUDOUR, Leila LAMIRI, Ouafia BELGHERBI, Rabah Boufnik  (2019)
Article de conférence

The purpose of this work is the development and characterization of a novel electrode material based on copper oxide (Cu2O) for use as electrode in catalytic application. The samples are prepared on an indium doped tin oxide (ITO) glass substrate using a simple electrochemical deposition process from a solution of copper (II) sulfate and citric acid. The Cu2O films are deposited under chronoamperometric control at a potential of −0.50V versus SCE at different deposition times ranging from 2 to 15 minutes. The solution was maintained at a temperature of 60°C and a pH of 11. The effect of the deposition time is mainly examined in terms of the change in structural, morphological and optical properties of the Cu2O films using various characterization techniques. Atomic force microscopy (AFM) images showed that the prepared thin films are homogeneous with a granular shape. Also, the surface of the deposits becomes roughened with increasing deposition time. Scanning electron microscopy (SEM) images showed that the morphology of the prepared thin films is composed of a mixture of cubic and pyramidal shapes regularly distributed over the surface of the substrate. X-ray diffraction (XRD) measurements demonstrated that Cu2O thin films prepared by electrochemical deposition have a pure cubic structure with higher preferred growth orientation (111) and good crystallinity. Characterization by UV-Visible spectroscopy showed that the samples have high absorption in the visible region. The calculated values of the direct band gap are between 1.9 and 2.15 eV. These results represent a good starting point for the development of low cost anode used in catalytic application. Voir les détails

Mots clés : Cu2O thin film, electrodeposition, deposition time, optical properties

Theoreticalmodelling for calculation of the energydensities of adsorption sites using inverse gaschromatography

A.BOUHANK, L.BENCHEIKH  (2019)
Publication

The inverse gas chromatography is used to determine the energy densities of theadsorption sites of the stationary solid phase. The use of this technique is old anddates back to the 1940s. The many possibilities offered by this method are describedin several works. This work is an attempt to explore some adsorption local isothermmodels in order to determine the energy density of the adsorption sites. It involves theuse of integral equations of the first kind which are known to be numerically instable.These integral equations were solved by two different methods of solution. One isbased on the use of Taylor series expansions and the other uses the Stieltjes transform.Some interesting theoretical and numerical results are presented. Voir les détails

Mots clés : adsorption, Integral equations, Adsorption isotherms, energy

Etude de quelques modèles pour le calcul des densités énergétiques des sites d'adsorption en utilisant la chromatographie gazeuse inverse

BOUHANK Antar (En préparation)
Thèse de doctorat

Résume :L'application de la Chromatographie Gazeuse Inverse (CGI) pour la détermination des grandeurs physico-chimiques qui caractérisent l'interaction entre une molécule sonde et unsupport chromatographique est déjà ancienne puisque les premiers travaux remontent aux années quarante. Les nombreuses possibilités offertes par cette méthode sont décrites dans plusieurs ouvrages. On se propose dans ce travail d'explorer quelques modèles d'adsorption locales,à savoir l’isotherme d’adsorption de Langmuir générale et de Sips pour calculer la densité énergétique des sites d'adsorption.Pour ce faire on s'appuie surdes méthodes analytiques et numériques. Une des méthodes analytiques utilise la notion de transformée de Stieltjes, alors que la méthode numérique est basée sur la discrétisation de l’équation intégrale en un système d’équations algébriques.  Voir les détails

Mots clés : adsorption, isotherme d'adsorption, Energie, équation d'intégrale