The Microstructure,Texture and Mechanical Properties of Friction Stir Welded Aluminum Alloy

Russian Journal of Non-Ferrous Metals - The microstructure and texture of 7075-T6 FSW weld with optimal parameters are investigated using optical microscopy, electron back scatter diffraction and...     

Understanding the degradation of MEA in PEMFC: Definition of structural markers and comparison between laboratory and on‐site ageing

Different accelerated tests in 12 fuel cells stack were performed in laboratory, namely on/off, back‐up, and base‐load regimes. In parallel, membrane electrode assemblies (MEA) were integrated in two “on‐site” systems for GSM relay application. One of them was dedicated to base‐load power applications while the second fuel cells coupled with photovoltaic panels operated in semibase load mode. To investigate the influence of the power profiles on MEA degradation, over 80 CCB MEAs (5 layers) were studied at different scales using ex situ characterizations such as tensile tests, TGA‐MS, DMTA, and SEM. A series of complementary microstructural ageing markers were thereby identified. The isolated influence of dry‐wet cycling on MEA properties was also established after passive hydro‐thermal (HT) ageing performed continuously for 10 months in the laboratory. The changes of each marker as a function of HT ageing time permitted to define a temporal benchmark. Based on these indicators, the main changes occurred in the MEA properties appear after a 5 months dry‐humid cycling (up to about 1800 cycles). The trends observed were useful to compare and estimate the degree of degradation of each ageing tests. Thus, the accelerated tests performed in laboratory for at least 500 h in stack did not reveal systematic MEA modifications. On the contrary, the 1500 h “on‐site” system operation results in some MEA degradations which origins are discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Multi‐walled carbon nanotubes as unexpected accelerators of chemical reactions

The influence of carbon nanotubes on various chemical reactions has been examined. These reactions include epoxy crosslinking, in situ polymerization of copolymers in the presence of carbon nanotubes and thermal degradation of a thermoplastic matrix. The various characterizations were based on different types of analyses, including differential scanning calorimetry, proton nuclear magnetic resonance, size exclusion chromatography and thermogravimetric analysis. In each case, we show that the presence of multi‐walled carbon nanotubes accelerates the process. © 2012 Society of Chemical Industry     

Aqueous Heck Arylation of Acrolein Derivatives: The Role of Cyclodextrin as Additive

Heck arylation of acrolein dialkyl acetal with (hetero)-aryl halides in water catalyzed by solid palladium catalysts and in presence of cyclodextrins is reported. Depending on the nature of the base, either cinnamaldehyde or 3-aryl propionic ester is obtained. It was shown that the presence of cyclodextrins in the reaction media increased the reaction rate as well as the stability of the palladium species.