Use of X-ray microtomography to study the homogeneity of carbon nanotube aqueous suspensions and carbon nanotube/polymer composites

in Carbon (2012), 50(4), 1703-1706

X-ray microtomography was used to study the stability and homogeneity of concentrated carbon nanotube (CNT) aqueous suspensions and CNT/resorcinol–formaldehyde gel composites. Various CNT distribution ... [more ▼]

X-ray microtomography was used to study the stability and homogeneity of concentrated carbon nanotube (CNT) aqueous suspensions and CNT/resorcinol–formaldehyde gel composites. Various CNT distribution states were achieved by modifying the CNT concentration, sonication time and resting time. X-ray microtomography is able to discriminate between zones with different CNT concentration levels and can be used as a non-destructive and fast tool to characterize the homogeneity of suspensions and composite systems at the micron scale. [less ▲]

Use of X-ray microtomography to study the homogeneity of carbon nanotube aqueous suspensions and carbon nanotube/polymer composites

in Carbon (2012), 50

Effect of CO2 activation of carbon xerogels on the adsorption of methylene blue

in Adsorption (2012), 18(3-4), 199-211

The effect of physical activation with CO2 of carbon xerogels, synthesized by pyrolysis of a resorcinolformaldehyde aqueous gel, on the adsorption capacities of Methylene Blue (MB) was studied. The ... [more ▼]

The effect of physical activation with CO2 of carbon xerogels, synthesized by pyrolysis of a resorcinolformaldehyde aqueous gel, on the adsorption capacities of Methylene Blue (MB) was studied. The activation with CO2 lead to carbon materials with micropore volumes ranging from 0.28 to 0.98 cm³/g -1 C. MB-adsorption isotherm studies showed that the increase of micropore volume and corresponding surface area led to: (i) a significant improvement in the capacity of MB-adsorption at monolayer coverage, from 212 to 714 mgg -1 C, and (ii) an increase of the binding energy related to Langmuir isotherm constant up to 45 times greater than those of commercial microporous activated carbons used as reference (NORIT R2030, CALGON BPL and CALGON NC35). It is proposed that the increase of the binding energy results from chemical cleaning of the O-groups onto carbon surface as a consequence of CO2-activation, increasing the π-π interaction between MB and graphene layers of the carbon xerogels. Finally, a series of batch kinetics were performed to investigate the effect of CO2-activation conditions on the mechanism of MB-adsorption. Experimental data were fitted using pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. From pseudo-second-order kinetic model, one observes an increase in the initial rate of MB-adsorption from 0.019 to 0.0565 min -1, by increasing the specific surface area from 630 to 2180 m²/g -1 C via CO2-activation. Depending on the activation degree of the carbons, two different mechanisms control the MB-adsorption rate: (i) at low activation degree, the intraparticle diffusion is the rate-limiting phenomenon, whereas (ii) at high activation degree, the reactions occurring at the solid/liquid interface are the rate-limiting steps. © 2012 Springer Science+Business Media, LLC. [less ▲]

Optimized deposition of TiO2 thin films produced by a non-aqueous sol-gel method and quantification of their photocatalytic activity

in Chemical Engineering Journal (2012), 195-196

TiO2 thin films have been produced by a dip-coating process using a non-aqueous sol-gel method. This study investigated the influence of the operating variables such as nature of the substrate, sol ... [more ▼]

TiO2 thin films have been produced by a dip-coating process using a non-aqueous sol-gel method. This study investigated the influence of the operating variables such as nature of the substrate, sol concentration, withdrawing speed of the dip-coater and number of layers on the physico-chemical properties of the films using XRD, GIXRD, UV-Vis spectroscopy, profilometry, spectroscopic ellipsometry and SEM. Photocatalytic activity of the films was evaluated by following the degradation of methylene blue under artificial UV light at 25°C. The performances of the catalysts were compared through the reaction rate constants determined using an apparent first-order kinetic model adjusted on the experimental data. This study showed that the photocatalytic activity and the reaction rate constant depend on the film thickness through the synthesis and dipping variable, with an optimum thickness of 80 nm being observed. An optimized transparent film exhibiting a high adhesion, a well crystallized TiO2-anatase phase, a good photocatalytic activity and a reaction rate constant k equal to 0.126 h-1 was obtained using a simple process. The specific photocatalytic activity of this film was higher to the one measured for TiO2 powders in previous works. [less ▲]

Large-scale synthesis of multi-walled carbon nanotubes in a continuous inclined mobile-bed rotating reactor by the catalytic chemical vapour deposition process using methane as carbon source

in Chemical Engineering Journal (2012)

Multi-walled carbon nanotubes (CNTs) were produced in a continuous inclined mobile-bed rotating reactor by the catalytic chemical vapour deposition of methane on a bimetallic Ni-Mo/MgO catalyst whose ... [more ▼]

Multi-walled carbon nanotubes (CNTs) were produced in a continuous inclined mobile-bed rotating reactor by the catalytic chemical vapour deposition of methane on a bimetallic Ni-Mo/MgO catalyst whose activity remains constant in the course of time. Measurements performed on the continuous reactor were validated to ensure that the installation worked correctly and that measurements were precise enough. The performance of the reactor was simulated using a model based on the chemical reactor engineering approach. Hypotheses of the model were verified, and a kinetic study was performed to obtain a kinetic rate expression and to determine the catalytic activity as a function of time. The purity level of produced CNTs depends on the desired properties of the product, so the operating conditions are linked to the purity level that is required. A minimal purity level corresponds to high carbon production, and a maximal purity level corresponds to high specific productivity. It was shown that operating conditions had to be fixed to reach a given specific productivity or a given carbon production, and the optimized operating conditions leading to those two opposite purity level objectives were established. [less ▲]

Synthesis by the sol-gel process of visible light sensitive-TiO2 for the degradation of pollutants and microorganisms

in Récents Progrès en Génie des Procédés, Lavoisier Technique et Documentation, Volume 101, 6 p. (CD-ROM) (2011, November 29)

To stabilize the TiO2-dye interaction, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced into the TiO2 matrix by cogelation rather than by grafting. DR ... [more ▼]

To stabilize the TiO2-dye interaction, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced into the TiO2 matrix by cogelation rather than by grafting. DR and FT-IR spectroscopies were performed to establish the interaction between porphyrins and TiO2. Cristallinity and specific surface area were performed by XRD and nitrogen adsorption-desorption measurements. The photoactivity of doped-TiO2 xerogels was evaluated for p-nitrophenol and Escherichia coli degradation. Under visible light, the samples allowed the degradation of 40% of p-nitrophenol in 6 h and the elimination of 108 CFU/mL of E. coli in 48 h. [less ▲]

Modelling of a continuous rotary reactor for carbon nanotube synthesis by catalytic chemical vapour deposition

Conference (2011, November)

nanostructured carbon materials by surfactant-templating of resorcinol-formaldehyde gels: towards a control of porosity for energy storage applications

Poster (2011, September 26)

Optimized deposition of photocatalytic TiO2 thin films produced by a non-aqueous sol-gel method

Poster (2011, September)

Pt/carbon xerogel catalysts for PEM fuel cells

in Proceedings of the Fundamentals & Developments of Fuel Cells (FDFC) 2011 Conference (2011, January 19)