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Laforgue A.,Industrial Materials Institute of Canada | Robitaille L.,Industrial Materials Institute of Canada
Macromolecules | Year: 2010

This study reports on the combination of the electrospinning technique and an adapted vapor-phase polymerization procedure to fabricate PEDOT nanofibers. The fibers have average diameters around 350 nm and are soldered at every intersection of the mat, ensuring a superior dimensional stability. The nanofibers are highly ordered at the molecular level, giving the nonwoven mats a very high conductivity (∼60 S/cm), the highest value reported so far for polymer nanofibers. The mats also demonstrate interesting electrochemical properties due to their porous and nanostructured nature. These conductive nanofibers are expected to be of interest for a number of electronic devices requiring flexibility and/or significant surface area, such as sensors or energy storage systems. © Published 2010 by the American Chemical Society.

Laforgue A.,Industrial Materials Institute of Canada
Journal of Power Sources | Year: 2011

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanofibers were obtained by the combination of electrospinning and vapor-phase polymerization. The fibers had diameters around 350 nm, and were soldered at most intersections, providing a strong dimensional stability to the mats. The nanofiber mats demonstrated very high conductivity (60 ± 10 S cm-1, the highest value reported so far for polymer nanofibers) as well as improved electrochemical properties, due to the ultraporous nature of the electrospun mats. The mats were incorporated into all-textile flexible supercapacitors, using carbon cloths as the current collectors and electrospun polyacrylonitrile (PAN) nanofibrous membranes as the separator. The textile layers were stacked and embedded in a solid electrolyte containing an ionic liquid and PVDF-co-HFP as the host polymer. The resulting supercapacitors were totally flexible and demonstrated interesting and stable performances in ambient conditions. © 2010 Elsevier B.V.

Yang D.,Industrial Materials Institute of Canada
Journal of Power Sources | Year: 2011

Thin films of manganese oxides have been grown by the pulsed laser deposition (PLD) process on silicon wafer and stainless steel substrates at different substrate temperatures and oxygen gas pressures. By proper selection of processing parameters such as temperature and oxygen pressure during the PLD process, pure crystalline phases of Mn 2O 3, Mn 3O 4 as well as amorphous phase of MnO x were successfully fabricated as identified by X-ray diffraction. The pseudo-capacitance behaviours of these different phases of manganese oxides have also been evaluated by the electrochemical cyclic voltammetry measured in 0.1 M Na 2SO 4 aqueous electrolyte at different scan rates. Their specific current and capacitance determined by electrochemical measurements were compared and the results show that crystalline Mn 2O 3 phase has the highest specific current and capacitance, while the values for crystalline Mn 3O 4 films are the lowest. The specific current and capacitance values of the amorphous MnO x films are lower than Mn 2O 3 but higher than Mn 3O 4. The specific capacitance of Mn 2O 3 films of 120 nm thick reaches 210 F g -1 at 1 mV s -1 scan rate with excellent stability and cyclic durability. This work has demonstrated that PLD is a very promising technique for screening high performance active materials for supercapacitor applications due to its excellent flexibility and capability of easily controlling chemical composition, microstructures and phases of materials. © 2011 Elsevier B.V. All rights reserved.

Utracki L.A.,Industrial Materials Institute of Canada
Polymer Degradation and Stability | Year: 2010

The Pressure-Volume-Temperature (PVT) of polystyrene (PS), polyamide-6 (PA-6) and their clay-containing polymeric nanocomposites (CPNC) were determined at T = 300-600 K and P = 0.1-190 MPa, thus in the molten, glassy and semicrystalline phase. The melt and glass behavior was interpreted following the Simha-Somcynsky (S-S) cell-hole free volume theory while that of the semicrystalline phase using S-S and the Midha-Nanda-Simha-Jain (MNSJ) cell theory describing crystalline quantum interactions. The theoretical analysis yielded two sets of the interaction parameters, one from the S-S and the other from the MNSJ model. The derivative properties: the compressibility, κ, and thermal expansion coefficient, α, were computed as functions of T, P and clay content, w. These functions, crossing several transition regions, were significantly different for the amorphous PS than for the semicrystalline PA-6. The isobaric PS plots of κ and α vs. T detected secondary transitions at Tβ/Tg ≈ 0.9 ± 0.1 and at Tc/Tg = 1.2 ± 0.1. Addition of clay severely affected the vitreous phase (physical aging). In PA-6 systems the behavior was distinctly different than in PS, viz. κ = κ(T) followed a similar function across the melting zone, while α = α(T) dependencies were dramatically different for the solid and molten phase. The theoretical functions in reduced variables over(κ, ̃) = κ P* = over(κ, ̃) (over(T, ̃), over(P, ̃)) ; over(α, ̃) = α T * = over(α, ̃) (over(T, ̃), over(P, ̃)) provided good basis for explanation of the observed dependencies. Crown Copyright © 2009.

Rousseau G.,Industrial Materials Institute of Canada | Blouin A.,Industrial Materials Institute of Canada | Monchalin J.-P.,Industrial Materials Institute of Canada
Biomedical Optics Express | Year: 2012

The detection of ultrasound in photoacoustic tomography (PAT) and ultrasonography (US) usually relies on ultrasonic transducers in contact with the biological tissue. This is a major drawback for important potential applications such as surgery and small animal imaging. Here we report the use of remote optical detection, as used in industrial laser-ultrasonics, to detect ultrasound in biological tissues. This strategy enables non-contact implementation of PAT and US without exceeding laser exposure safety limits. The method uses suitably shaped laser pulses and a confocal Fabry-Perot interferometer in differential configuration to reach quantum-limited sensitivity. Endogenous and exogenous inclusions exhibiting optical and acoustic contrasts were detected ex vivo in chicken breast and calf brain specimens. Inclusions down to 0.5 mm in size were detected at depths well exceeding 1 cm. The method could significantly expand the scope of applications of PAT and US in biomedical imaging. © 2011 Optical Society of America.

Li H.,Industrial Materials Institute of Canada | Huneault M.A.,Université de Sherbrooke
Journal of Applied Polymer Science | Year: 2011

This article investigates the structure and properties of thermoplastic starch/PLA blends where the TPS phase is plasticized by sorbitol, glycerol, and glycerol/sorbitol mixtures. The blends were prepared using a twin-screw extruder where starch gelatinization, water removal, and dispersion of TPS into a PLA matrix were carried out sequentially. The plasticizers were added to starch in the first stage of the extruder to allow complete starch gelatinization. The PLA was added at mid-extruder and thoroughly mixed with the TPS. The plasticizer concentration was varied from 30 to 42% and the TPS content was varied from 27 to 60% on a weight basis. In all investigated blends, the PLA formed the continuous phase and the TPS was the dispersed phase. The viscosity, blend morphology, tensile mechanical properties as well as the thermal properties of the materials were measured. It was found that the glycerol/sorbitol ratio has an important effect on the blend properties. Finer blend morphologies, higher tensile strength and modulus but lower crystallization rate were found for the sorbitol plasticized blends. © 2010 Wiley Periodicals, Inc.

Laforgue A.,Industrial Materials Institute of Canada
Journal of Materials Chemistry | Year: 2010

Conductive PEDOT nanofiber mats were obtained by the electrospinning of oxidant fibers and subsequent vapour-phase polymerization of the EDOT monomer. The mats presented high conductivities as well as unprecedented resistive heating properties. Electrically controlled colour-changing textiles were produced by coating thermochromic inks on the PEDOT mats and triggering the colour change by applying current to the mat. © 2010 The Royal Society of Chemistry.

Laforgue A.,Industrial Materials Institute of Canada | Robitaille L.,Industrial Materials Institute of Canada
Chemistry of Materials | Year: 2010

Electrospun polyacrylonitrile (PAN) nanofibers were successfully coated with polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene) PEDOT layers. To obtain ultrathin coatings on highly porous nanofibrous webs, we adapted a two-step vapor-phase coating process usually used to produce ultrathin films. Ferric tosylate (FeTos) was chosen as the oxidant, because of its solvent-free templating effect that produces highly ordered polymer coatings with improved electronic properties. The concentration of the oxidant solution was found to be a key parameter for the preservation of the open porosity in the nanofibrous mats. Coating thicknesses varied from 5 to 12 nm depending on the polymer and oxidant concentrations. The coatings were strongly attached to the PAN nanofibers and presented some degree of crystallinity and high conductivities. PEDOT-coated nanofibers displayed good electrochemical properties without the need of an additional current collector, making them excellent candidates for the fabrication of flexible electronic devices. © 2010 American Chemical Society.

Yang D.,Industrial Materials Institute of Canada
Journal of Power Sources | Year: 2012

Thin films of manganese oxide doped with various percentages of cobalt oxide were grown by pulsed laser deposition on silicon wafers and stainless steel substrates. The films were characterized by Xray diffraction and field emission scanning electron microscopy in order to identify their phases and microstructures. The pseudo-capacitance behavior of the Co-doped manganese oxide films were then evaluated using electrochemical cyclic voltammetry in an aqueous electrolyte. Their specific current and capacitance determined by electrochemical measurements were compared with undoped manganese oxide films, and the results show that Co-doped amorphous MnOx films have significantly higher specific current and capacitance than undoped amorphous MnOx films. The 3.0% Co-doped MnOx (i.e., Mn 0.970Co0.030Ox) film had the highest specific capacitance of 99 F g?1 at a 5 mV s?1 scan rate. However, Co-doped crystalline Mn2O3 films did not show an improvement in specific current and capacitance compared with undoped Mn 2O3 crystalline films. High Co doping level (20.7% doped) in the crystalline Mn2O3 films actually decreased both the specific current and capacitance values. These findings demonstrate that elemental doping is an effective way to improve the performance of pseudo-capacitive metal oxides. © 2011 Published by Elsevier B.V. All rights reserved.

Amira S.,Industrial Materials Institute of Canada | Huot J.,University of Québec
Journal of Alloys and Compounds | Year: 2012

The effect of cold rolling, as an activation process of materials aimed to hydrogen storage application, was applied to some cast magnesium alloys. The alloys studied in this work are AZ91D and three experimental creep resistant magnesium alloys (MRI153, AXJ530, ZAEX10430) in the as-cast and die-cast states. Experiments showed that AZ91D, MRI153 and ZAEX10430 have faster absorption/desorption kinetic than as-cast pure magnesium. On the other hand, AXJ530 showed the worst hydrogen storage properties. These results were attributed to a possible beneficial effect of aluminum and zinc as alloying elements. Segregation inside primary α-Mg grains may explain the difference of hydrogen storage properties between as-cast and die-cast alloys. © 2011 Elsevier B.V. All rights reserved.

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