Nanocyl (Belgium)

Carbon nanotubes (CNT) are of great commercial interest. Theoretically, during processing and handling of CNT and in abrasion processes on composites containing CNT, inhalable CNT particles might be set free. For hazard assessment, we performed a 90-day inhalation toxicity study with a multiwall CNT (MWCNT) material (Nanocyl NC 7000) according to Organisation for Economic Co-operation and Development test guideline 413. Wistar rats were head-nose exposed for 6 h/day, 5 days/week, 13 weeks, total 65 exposures, to MWCNT concentrations of 0 (control), 0.1, 0.5, or 2.5 mg/m(3). Highly respirable dust aerosols were produced with a proprietary brush generator which neither damaged the tube structure nor increased reactive oxygen species on the surface. Inhalation exposure to MWCNT produced no systemic toxicity. However, increased lung weights, pronounced multifocal granulomatous inflammation, diffuse histiocytic and neutrophilic inflammation, and intra-alveolar lipoproteinosis were observed in lung and lung-associated lymph nodes at 0.5 and 2.5 mg/m(3). These effects were accompanied by slight blood neutrophilia at 2.5 mg/m(3). Incidence and severity of the effects were concentration related. At 0.1 mg/m(3), there was still minimal granulomatous inflammation in the lung and in lung-associated lymph nodes; a no observed effect concentration was therefore not established in this study. The test substance has low dust-forming potential, as demonstrated by dustiness measurements, but nonetheless strict industrial hygiene measures must be taken during handling and processing. Toxicity and dustiness data such as these can be used to compare different MWCNT materials and to select the material with the lowest risk potential for a given application.

Abstract The modeling of carbon nanotube production by the CCVD process in a continuous rotary reactor with mobile bed was performed according to a rigorous chemical reaction engineering approach. The geometric, hydrodynamic, physical and physicochemical factors governing the process were analyzed in order to establish the reactor equations. While the study of the hydrodynamic factor suggests a co‐current plug‐flow approximation, the physical factor mainly deals with the phenomena of transport and the transfer of mass, which can be neglected. Concerning the physicochemical factor, the modeling is based on knowledge of the expression of the initial reaction rate, and takes into account catalytic deactivation as a function of time, according to a sigmoid decreasing law. The reactor modeling allows obtaining the evolution of partial pressure, carbon nanotube production and catalytic deactivation along the reactor for given initial operating conditions. The comparison between experimental and calculated production highlights a very good fit of data. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Selected acyclic disubstituted η4-(1E,3E)-dienyl-Fe(CO)3 iron complexes presented a non-covalent, but reversible affinity for multi-walled carbon nanotube (MWCNT) sidewalls likely mediated by hydrophobic and/or π–π stacking interactions. Resulting iron-complexed MWCNT-based composites displayed methyl ester/acetate, aldehyde and/or OH functional groups on CNT sidewalls. They displayed strong FT-IR absorption peaks due to organometallic CO groups of the Fe(CO)3 unit (νCO = 1966–2068 cm−1). These peaks appeared in an absorption window free of any parasitic band that usually characterize organic/bio-organic species. Routine FT-IR spectroscopy enabled an effective tracking of adsorption processes of iron complexes onto MWCNT sidewalls. Iron-complexed MWCNTs may be readily dissociated using CH3CN, allowing an accurate weight quantification of adsorptions. Both interacting components remained unmodified after composite dissociation. Sidewall oxygenated defects at high concentration were also shown to be detrimental to iron complex adsorption. This quantitative decoration methodology may constitute a quite unusual application in the Quality-Control (QC)-driven standardization/improvement of the industrial production of MWCNTs (detection of MWCNT sidewall oxygenated defects during fabrication and purification).

Download options Please wait... Supplementary files X-Ray photoelectron spectroscopy (XPS): analysis of neat MWNTs, MAO-treated MWNTs, and MAO/Cp* 2ZrCl 2-treated MWNTs PDF (133K) Article information DOI https://doi.org/10.1039/B701764B Article type Paper Submitted 05 Feb 2007 Accepted 09 Mar 2007 First published 29 Mar 2007 Download Citation J. Mater. Chem., 2007,17, 2359-2366 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Supported metallocene catalysis as an efficient tool for the preparation of polyethylene/carbon nanotube nanocomposites: effect of the catalytic system on the coating morphology D. Bonduel, S. Bredeau, M. Alexandre, F. Monteverde and P. Dubois, J. Mater. Chem., 2007, 17, 2359 DOI: 10.1039/B701764B To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Daniel Bonduel Stéphane Bredeau Michäel Alexandre Fabien Monteverde Philippe Dubois

Thermal measurements on a GaAs/AlGaAs heterostructure reveal that the state of the confined two-dimensional electrons dramatically affects the nuclear-spin diffusion near Landau level filling factor \nu=1. The experiments provide quantitative evidence that the sharp peak in the temperature dependence of heat capacity near \nu=1 is due to an enhanced nuclear-spin diffusion from the GaAs quantum wells into the AlGaAs barriers. We discuss the physical origin of this enhancement in terms the possible Skyrme solid-liquid phase transition.