CNRS Materials and Transformations Unit of UMET

Lille, France

CNRS Materials and Transformations Unit of UMET

Lille, France
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Descamps M.,CNRS Materials and Transformations Unit of UMET | Willart J.F.,CNRS Materials and Transformations Unit of UMET
Advanced Drug Delivery Reviews | Year: 2016

This paper presents an overview of recent advances in understanding the role of the amorphous state in the physical and chemical transformations of pharmaceutical materials induced by mechanical milling. The following points are addressed: (1) Is milling really able to amorphise crystals?, (2) Conditions for obtaining an amorphisation, (3) Milling of hydrates, (4) Producing amorphous state without changing the chemical nature, (5) Milling induced crystal to crystal transformations: mediation by an amorphous state, (6) Nature of the amorphous state obtained by milling, (7) Milling of amorphous compounds: accelerated aging or rejuvenation, (8) Specific recrystallisation behaviour, and (9) Toward a rationalisation and conceptual framework. © 2016 Elsevier B.V.

Gasmi H.,French Institute of Health and Medical Research | Danede F.,CNRS Materials and Transformations Unit of UMET | Siepmann J.,French Institute of Health and Medical Research | Siepmann F.,French Institute of Health and Medical Research
Journal of Controlled Release | Year: 2015

Abstract The aim of this study was to better understand the mass transport mechanisms controlling drug release from PLGA microparticles. New insight was gained based on the experimental monitoring of single microparticle swelling. An oil-in-water (O/W) solvent extraction/evaporation method was used to prepare ketoprofen-loaded microparticles, varying the initial drug loading from 0.6 to 45.2%. Importantly, the microparticle size was kept about constant. At low ketoprofen loadings, the release patterns were clearly tri-phasic: an initial burst release was followed by a period with an about constant release rate and a final (again rapid) drug release phase. With increasing initial drug content the onset of the third release period was shifted to earlier time points. At even higher drug loadings, the release patterns became more or less bi- or mono-phasic. Interestingly, all types of microparticles showed substantial swelling after a lag-time, which coincided with the onset of the third (and again rapid) drug release phase at low loadings and proceeded it by 1 or 2 d at higher drug loadings. The substantial microparticle swelling set on as soon as a critical PLGA molecular weight was reached (around 20 kDa). Thus, the onset of the third drug release phase from the PLGA microparticles might be explained as follows: once the macromolecules are sufficiently short, substantial amounts of water penetrate into the system, significantly increasing the mobility of the drug within the microparticles and resulting in increased drug release rates. © 2015 Elsevier B.V.

Lu G.-H.,Beihang University | Zhou H.-B.,Beihang University | Becquart C.S.,CNRS Materials and Transformations Unit of UMET
Nuclear Fusion | Year: 2014

Tungsten (W) is considered to be one of the most promising plasma-facing materials (PFMs) for next-step fusion energy systems. However, as a PFM, W will be subjected to extremely high fluxes of low-energy hydrogen (H) isotopes, leading to retention of H isotopes and blistering in W, which will degrade the thermal and mechanical properties of W. Modelling and simulation are indispensable to understand the behaviour of H isotopes including dissolution, diffusion, accumulation and bubble formation, which can contribute directly to the design, preparation and application of W as a PFM under a fusion environment. This paper reviews the recent findings regarding the behaviour of H in W obtained via modelling and simulation at different scales. © 2014 IAEA, Vienna.

Ji G.,CNRS Materials and Transformations Unit of UMET | Morniroli J.-P.,Ecole Nationale Supérieure de Chimie de Lille
Journal of Applied Crystallography | Year: 2013

The space group of a new metastable orthorhombic Al2Cu phase, located in the Al-rich interfacial region of an Al-Cu friction stir weld, was unambiguously identified as Ic2m by a recently developed systematic method combining precession electron diffraction and convergent-beam electron diffraction. This metastable phase has the same tetragonal lattice as its stable θ-Al2Cu counterpart (tetragonal, I4/mcm, No. 140). The tetragonal-to-orthorhombic symmetry lowering is due to slight modifications of the atomic positions in the unit cell. This metastable phase can be transformed into the stable θ-Al2Cu phase by in situ irradiation within the transmission electron microscope. Copyright © International Union of Crystallography 2013.

Affouard F.,CNRS Materials and Transformations Unit of UMET | Correia N.T.,New University of Lisbon
Journal of Physical Chemistry B | Year: 2010

By means of molecular dynamics simulations, dynamical properties of racemic ibuprofen glass-forming liquid are investigated at different temperatures from 360 to 500 K. The origin of the peculiar low amplitude Debye-type relaxation observed experimentally by dielectric relaxation spectroscopy is addressed (Bras, A. R.; Noronha, J. P.; Antunes, A. M. M.; Cardoso, M. M.; Schönhals, A.; Affouard, F.; Dionisio, M.; Correia, N. T. J. Phys. Chem. B 2008, 112, 11087). Single and total dipolar autocorrelation functions are calculated. It is found that the behavior of the total dipole correlation is dominated at short and long times by the single function. It mainly originates from the antiparallel dipoles correlations in agreement with a value of the Kirkwood correlation factor slightly smaller than unity. The simulation suggests that the long time Debye-type decay of the dipole-dipole correlation is dominated by the internal cis-trans conversion of the O - C - O - H group coupled to the change of the intermolecular linear/cyclic HB structures. The overall rotation of the molecules is about 1-2 decades faster than the cis to trans transformation, so all the O - C - O - H group environments are equal on average. The effective rotational potential energy barriers of the O - C - O - H groups due to the surroundings are thus averaged and dipolar relaxation follows a simple Debye law. It is found that cyclic dimers inhibit the cis to trans conversion unlike the linear dimers and trimers which favor this conversion and stabilize the trans isomer. It is well in line with the very low amplitude of the dielectric strength associated with the Debye relaxation observed experimentally and its increase when the liquid is maintained isothermally above the melting temperature since this amplitude mainly relates to the low fraction of ibuprofen molecules in the trans conformation. A comparison is made with the Debye-type relaxation found in microstructured monohydroxy alcohols. © 2010 American Chemical Society.

Stoclet G.,CNRS Materials and Transformations Unit of UMET | Seguela R.,CNRS Materials and Transformations Unit of UMET | Lefebvre J.-M.,CNRS Materials and Transformations Unit of UMET
Polymer | Year: 2011

Blends of entirely biosourced polymers, namely polylactide (PLA) and polyamide11 (PA11), have been melt-compounded by twin-screw extrusion without the use of any compatibilizing agent. The crystallization and melting behavior, the morphology and mechanical properties of the melt-compounded binary blends have been investigated over the whole composition range. Albeit immiscibility prevails in all blends, the micronic and sub-micronic dispersion of the minor phase reveals a self-compatibilization behavior of the PLA/PA11 system as directly evidenced via scanning electron microscopy. For PLA compositions below 50%, PLA appears to be dispersed as globules in the PA11 matrix. With increasing PLA content beyond 50%, the blends exhibit co-continuous intertwined phases, then thread-like PA11 phase dispersed in a PLA matrix. For PLA composition greater than 80%, PA11 displays globular dispersion. In the case of PLA-rich blends, the crystallization of PA11 from the melt displayed a contribution of "homogeneous nucleation" corroborating the high degree of dispersion of the minor phase. However, the earlier crystallization of PA11 upon cooling did not promote that of PLA suggesting low interfacial free energy at the boundaries of the phase-separated domains, i.e. roughly neutral interactions between the unlike species. The non-symmetric structural behavior of the blends over the whole composition range was found to influence the mechanical properties. If the elastic modulus of the blends roughly obeys an additive mixture law at room temperature (RT), this is not the case above the Tg of both PLA and PA11. More particularly in the PLA-rich range, the thread-like dispersion of the stiff PA11 component plays the role of in situ fibrillar reinforcement of the soft PLA matrix. The strain at break and the yield stress also do not obey a simple mixture law, both at RT and above Tg. Perspectives of morphological and mechanical improvements of PLA/PA11 blends are discussed. © 2011 Elsevier Ltd. All rights reserved.

Leroux H.,CNRS Materials and Transformations Unit of UMET
Meteoritics and Planetary Science | Year: 2012

The deceleration tracks in the Stardust aerogel display a wide range of morphologies, which reveal a large diversity of incoming particles from comet 81P/Wild 2. If the large and dense mineral grains survived the extreme conditions of hypervelocity capture, this was not the case for the fine-grained material that is found strongly damaged within the aerogel. Due to their low mechanical strength, these assemblages were disaggregated, dispersed, and flash melted in the aerogel in walls of bulbous deceleration tracks. Their petrologic and mineralogical properties are found significantly modified by the flash heating of the capture. Originating from a quenched melt mixture of comet material and aerogel, the representative microstructure consists of silica-rich glassy clumps containing Fe-Ni-S inclusions, vesicles and "dust-rich" patches, the latter being remnants of individual silicate components of the impacting aggregate. The average composition of these melted particle fragments is close to the chondritic CI composition. They might originate from ultrafine-grained primitive components comparable to those found in chondritic porous IDPs. Capture effects in aerogel and associated sample biases are discussed in terms of size, chemical and mineralogical properties of the grains. These properties are essential for the grain survival in the extremely hot environment of hypervelocity impact capture in aerogel, and thus for inferring the correct properties of Wild 2 material. © 2012 The Meteoritical Society.

Thuinet L.,CNRS Materials and Transformations Unit of UMET | Besson R.,CNRS Materials and Transformations Unit of UMET
Applied Physics Letters | Year: 2012

The preferential habit planes of coherent precipitates, strongly influencing alloy properties, can be investigated by direct-space elasticity methods, providing new insight into delicate issues such as elastic inhomogeneities or anharmonicity. Focusing on the poorly known hexagonal system, this work enlightens important trends overlooked hitherto, such as the critical role of C 44, leading to the identification of distinct families of hexagonal alloys for precipitation. Moreover, it demonstrates the complex influence of inhomogeneities for real, finite-thickness morphologies. Finally, it provides the missing material required for atomic-scale studies of precipitation in low-symmetry systems with long-range interactions. © 2012 American Institute of Physics.

Thuinet L.,CNRS Materials and Transformations Unit of UMET | Besson R.,CNRS Materials and Transformations Unit of UMET
Intermetallics | Year: 2012

We present a detailed atomic-scale investigation of coherent hydrides in Zr alloys. While previous experimental and theoretical studies emphasized the γ′ (ZrH) and ζ (Zr2H) phases as potential precursors in the hydride precipitation sequence, they led to contradictory conclusions justifying further analysis of the nucleation of these two types of precipitates. To this aim, we take proper account of the three energy contributions (bulk chemical, interfacial and elastic) involved in Classical Nucleation Theory by incorporating original features such as (i) ζ bulk off-stoichiometry, (ii) anisotropic matrix/hydride interfacial energies and (iii) shape factors of platelike nuclei. These effects turn out to be essential to provide a realistic description of the conditions of temperature and H content leading to preferential γ′ or ζ formation. Our work provides a unifying picture of the previous, apparently diverging, works on coherent zirconium hydrides. © 2011 Elsevier Ltd. All rights reserved.

Thuinet L.,CNRS Materials and Transformations Unit of UMET | De Backer A.,CNRS Materials and Transformations Unit of UMET | Legris A.,CNRS Materials and Transformations Unit of UMET
Acta Materialia | Year: 2012

A phase-field model was developed within the framework of heterogeneous elasticity theory to study the precipitation of particles with trigonal symmetry in a hexagonal matrix. The model is first calibrated and successfully compared with previous analytical calculations performed to explain the effect of symmetry-breaking transformations on precipitate morphology. Secondly, the model was adapted to study the precipitation of the coherent ζ hydride phase in zirconium. The results are consistent with the well-established experimental observation of the existence of acicular precipitates aligned along the dense directions in the basal plane. Moreover, original kinetic pathways are implied by the presence of a threefold axis of symmetry, leading to the emergence of original morphological bifurcations not previously reported and probably related to the inconsistency between the threefold symmetry and the inversion properties of the B function introduced by Khachaturyan. In spite of its simplicity (only one order parameter is taken into account), the present phase-field model gives rise to very complex morphological sequences. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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