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PEOPLE@HES-SO – Annuaire et Répertoire des compétences
PEOPLE@HES-SO – Annuaire et Répertoire des compétences

PEOPLE@HES-SO
Annuaire et Répertoire des compétences

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Brodard Pierre

Brodard Pierre

Professeur HES associé

Compétences principales

Physical chemistry

Raman spectroscopy

Thermal analysis

Materials characterization

Polymers caharacterization

Thermal safety

Surface imaging

  • Contact

  • Enseignement

  • Recherche

  • Publications

  • Conférences

Contrat principal

Professeur HES associé

Téléphone: +41 26 429 67 19

Bureau: HEIA_B20.03

Haute école d'ingénierie et d'architecture de Fribourg
Boulevard de Pérolles 80, 1700 Fribourg, CH
HEIA-FR
BSc HES-SO en Chimie - Haute école d'ingénierie et d'architecture de Fribourg
  • Mécanique quantique
  • Spectroscopie optique
  • Travaux pratiques de chimie physique

Terminés

Bio-based smart packaging for enhanced preservation of food quality
AGP

Rôle: Collaborateur/trice

Financement: FR - EIA - Institut iRAP; Horizon 2020

Description du projet : The BIOSMART project proposal has the ambition to develop active and smart bio-based and compostable packages addressing the needs of several food market segments. The knowledge gained from developing the novel packages forms the basis for tailoring performance and functionality to other flexible and rigid food packages in diverse market segments. An holistic ecosystem approach is pursued by offering solutions that bring enhanced performance and acceptable economics to the packaging value chain to facilitate their implementation and large-scale commercialization. Critical issues that differentiate the present packages from the future all-bio-based and compostable ones are enhanced active and smart functionalities that make possible: light weighting, reduced food residues, shelf life monitoring and longer shelf life, easier consumer waste handling, and all this at a competitive cost to the incumbent. The BIOSMART project proposal develops an approach for selectively integrating superhydrophobic surfaces, microencapsulated phase change materials (thermoregulation), barrier coatings, very low cost sensor devices, and new bio-based and active ingredients (anti-microbial, anti-fungal, and antioxidants), into all-bio-based compostable packages. Three generic packaging systems are selected with specific performance needs as defined by current multi-material fossil-fuel based packages (i.e. pouches, terrines and an hybrid carton/thin film tray). The associate life cycle assessments for the different possible scenarios include the economic feasibility as a defining key performance indicator. Ultimately, the gathered developmental knowledge is consolidated in a material selection and package performance simulation Application. It enables through optimization of key performance indicators and representing emulators a quick selection of relevant plastics, packaging composition, and cost.

Equipe de recherche au sein de la HES-SO: Brodard Pierre , Hennebert Jean , Blanchard Lucien , Albergati Luce , Esseiva Julien , Zurbuchen Nicolas , Ayer Baptiste , Koopmans Rudolf , Mavrozoumi Vasiliki , Rychener Lorenz , Marti Roger

Partenaires académiques: FR - EIA - Institut ChemTech; FR - EIA - Institut iCoSys

Durée du projet: 01.04.2017 - 31.10.2021

Montant global du projet: 948'840 CHF

Statut: Terminé

2024

Up-scaling a sol-gel process for the production of a multi-component xerogel powder
Article scientifique ArODES

Barbara Pföss, Jonathan Caldi, Sutida Jansod, Christophe Allemann, Pierre Brodard, Roger Marti

CHIMIA,  2024, 78, 3, 142-147

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Résumé:

A sol-gel process for the synthesis of a multi-component oxide material from the system SiO2-ZrO2-Al2O3underwent optimization and up-scaling. Initially, on a laboratory scale, components including precursors, catalysts, and additives were methodically evaluated to ensure a safe and efficient transition to larger volumes. Subsequently, the equipment for the whole setup of the sol-gel process was strategically selected. Leveraging insights from these optimizations, the process was successfully scaled-up to pilot-scale operation, conducting hydrolysis, condensation reactions, gelation, aging, and drying within a single, integrated conical dryer system for an 80 L batch. A visual test and FTIR spectroscopy were applied for process control and monitoring.

2022

Thermal safety and structure-related reactivity investigation of five-membered cyclic sulfamidates
Article scientifique ArODES

Thomas Ferrari, Caitlin Blum, Lara Amini-Rentsch, Pierre Brodard, Michal Dabros, Pascale Hoehn, Aniko Udvarhelyi, Roger Marti, Michaël Parmentier

Organic Process Research Development,  2022, vol. 26, pp. 2614-2623

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Résumé:

Five-membered cyclic sulfamidates are very valuable electrophiles in organic synthesis and readily used on a multikilogram scale. However, their thermal degradation is underreported and might lead to unforeseen and undesirable safety events. In addition, ring or nitrogen substitution can have a tremendous influence on cyclic sulfamidate reactivity toward bases and therefore impact the overall safety assessment of a process. An understanding of such behavior is therefore of high importance in the industry while designing a synthetic route, as a change of, e.g., a protecting group can increase the thermal safety of a step on scale. We report herein the thermal degradation investigation as well as the structure-related reactivity exploration of cyclic sulfamidates, including their use in combination with strong bases. The design of a predictive model to rapidly assess the thermal hazard based on collected data and selected molecular descriptors is also presented.

Development, validation, and application of a custom-made mini-reaction calorimeter for thermal safety screening
Article scientifique ArODES

Caitlin Blum, Lara Amini-Rentsch, Thomas Ferrari, Pierre Brodard, Roger Marti, Pascale Hoehn, Michal Dabros, Michaël Parmentier

Organic Process Research Development,  2022, vol. 26, no. 9, pp. 2624-2628

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Résumé:

Before scaling up to production, it is of high importance to evaluate the potential of a reaction to lead to an undesired thermal degradation event. The use of a large amount of compounds is usually required for a reliable calorimetry study. In this work, we report the development of a milliliter-scale reaction calorimeter for reaction screening applications. The setup was designed using laboratory equipment and characterized and validated with routine experiments. The results were sufficiently accurate enabling us to observe trends in the measured reaction enthalpies of a family of compounds reacting with strong bases as a function of the compounds' structures.. The use of the microscale tailor-made calorimeter is considered very valuable for potentially highly energetic reactions since reaction calorimetry studies can be performed accurately and safely with small amounts of valuable materials.

2020

A nano-rattle SnO2@carbon composite anode material for high-energy Li-ion batteries by melt diffusion impregnation
Article scientifique ArODES

Sivarajakumar Maharajan, Nam Hee Kwon, Pierre Brodard, Katharina M. Fromm

Nanomaterials,  2020, vol. 10, no. 4

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Résumé:

The huge volume expansion in Sn-based alloy anode materials (up to 360%) leads to a dramatic mechanical stress and breaking of particles, resulting in the loss of conductivity and thereby capacity fading. To overcome this issue, SnO2@C nano-rattle composites based on <10 nm SnO2 nanoparticles in and on porous amorphous carbon spheres were synthesized using a silica template and tin melting diffusion method. Such SnO2@C nano-rattle composite electrodes provided two electrochemical processes: a partially reversible process of the SnO2 reduction to metallic Sn at 0.8 V vs. Li+/Li and a reversible process of alloying/dealloying of LixSny at 0.5 V vs. Li+/Li. Good performance could be achieved by controlling the particle sizes of SnO2 and carbon, the pore size of carbon, and the distribution of SnO2 nanoparticles on the carbon shells. Finally, the areal capacity of SnO2@C prepared by the melt diffusion process was increased due to the higher loading of SnO2 nanoparticles into the hollow carbon spheres, as compared with Sn impregnation by a reducing agent.

2019

Melt-spun nanocomposite fibers reinforced with aligned tunicate nanocrystals
Article scientifique ArODES

Alexandre Redondo, Sourav Chatterjee, Pierre Brodard, LaShanda T. J. Korley, Christoph Weder, Ilja Gunkel, Ullrich Steiner

Polymers,  2019, vol. 11, no. 12, article no. 1912

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Résumé:

The fabrication of nanocomposite films and fibers based on cellulose nanocrystals (P-tCNCs) and a thermoplastic polyurethane (PU) elastomer is reported. High-aspect-ratio P-tCNCs were isolated from tunicates using phosphoric acid hydrolysis, which is a process that affords nanocrystals displaying high thermal stability. Nanocomposites were produced by solvent casting (films) or melt-mixing in a twin-screw extruder and subsequent melt-spinning (fibers). The processing protocols were found to affect the orientation of both PU hard segments and the P-tCNCs within the PU matrix and therefore the mechanical properties. While the films were isotropic, both the polymer matrix and the P-tCNCs proved to be aligned along the fiber direction in the fibers, as shown using SAXS/WAXS, angle-dependent Raman spectroscopy, and birefringence analysis. Tensile tests reveal that fibers and films, at similar P-tCNC contents, display Young’s moduli and strain-at-break that are within the same order of magnitude, but the stress-at-break was found to be ten-times higher for fibers, conferring them a superior toughness over films.

Raman spectroscopy assisted residual stress measurement of plasma sprayed and laser remelted zirconia splats and coatings
Article scientifique ArODES

Biswajit Das, Pierre Brodard, Partha Pratim Bandyopadhyay

Surface and Coatings Technology,  2019, vol. 378. article no 124920

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Résumé:

This investigation deals with Raman and X-ray assisted stress measurement of plasma sprayed and laser remelted zirconia splats and coating. A Raman peak of tetragonal zirconia phase at 635.38 cm−1 was used as a reference peak. The tensile residual stress in the as-sprayed and laser remelted single splat lied in the range of 1–2 GPa and 0.2–0.9 GPa, respectively. Surface residual stress of the as-sprayed coating is tensile and its magnitude increases upon laser remelting. Raman spectroscopy results are in agreement with those obtained using X-ray diffraction. It appears that Raman spectroscopy is suitable for quick and accurate measurement of residual stress for small sized Raman active objects and stress depth profiling of the bulk coating. Splat morphology was correlated with particle velocity and temperature. Microstructural aspects and mechanical properties of as-sprayed and laser remelted coating were also investigated.

Materials science at Swiss Universities of Applied Sciences
Article scientifique ArODES

Pierre Brodard, Michal Dabros, Roger Marti, Ennio Vanoli, Manfred Zinn, Urban Frey, Christian Adlhart, Lucy Kind, Franziska Koch, Floriana Burgio, Johan Stenqvist, Sina Saxer, Uwe Pieles, Patrick Shahgaldian, Sebastian Wendeborn

CHIMIA International Journal for Chemistry,  2019, vol. 73, no. 7/8, pp. 645-655

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Résumé:

In the Swiss Universities of Applied Sciences, several research institutes are involved in Materials Science, with different approaches and applications fields. A few examples of recent projects from different groups of the University of Applied Sciences and Arts Western Switzerland (HESSO), the Zurich University of Applied Sciences (ZHAW) and the University of Applied Sciences and Arts Northwestern Switzerland (FHNW) are given.

2017

Characteristics and properties of nano-LiCoO2 synthesized by pre-organized single source precursors: Li-ion diffusivity, electrochemistry and biological assessment
Article scientifique ArODES

Jean-Pierre Brog, Aurélien Crochet, Joël Seydoux, Martin J. D. Clift, Benoît Baichette, Sivarajakumar Maharajan, Hana Barosova, Pierre Brodard, Mariana Spodaryk, Andreas Züttel, Barbara Rothen-Rutishauser, Nam Hee Kwon, Katharina M. Fromm

Journal of Nanobiotechnology,  2017, vol. 15, article no. 58

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Résumé:

Background : LiCoO2 is one of the most used cathode materials in Li-ion batteries. Its conventional synthesis requires high temperature (>800 °C) and long heating time (>24 h) to obtain the micronscale rhombohedral layered high-temperature phase of LiCoO2 (HT-LCO). Nanoscale HT-LCO is of interest to improve the battery performance as the lithium (Li+) ion pathway is expected to be shorter in nanoparticles as compared to micron sized ones. Since batteries typically get recycled, the exposure to nanoparticles during this process needs to be evaluated. Results : Several new single source precursors containing lithium (Li+) and cobalt (Co2+) ions, based on alkoxides and aryloxides have been structurally characterized and were thermally transformed into nanoscale HT-LCO at 450 °C within few hours. The size of the nanoparticles depends on the precursor, determining the electrochemical performance. The Li-ion diffusion coefficients of our LiCoO2 nanoparticles improved at least by a factor of 10 compared to commercial one, while showing good reversibility upon charging and discharging. The hazard of occupational exposure to nanoparticles during battery recycling was investigated with an in vitro multicellular lung model. Conclusions : Our heterobimetallic single source precursors allow to dramatically reduce the production temperature and time for HT-LCO. The obtained nanoparticles of LiCoO2 have faster kinetics for Li+ insertion/extraction compared to microparticles. Overall, nano-sized LiCoO2 particles indicate a lower cytotoxic and (pro-)inflammogenic potential in vitro compared to their micron-sized counterparts. However, nanoparticles aggregate in air and behave partially like microparticles.

2016

Life and death of plastics
Article professionnel ArODES

Yvan Mongbanziama, Sandrine Aeby, Matthieu Kaehr, Vincent Pilloud, Jean-Luc Robyr, Bernard Masserey, Stefan Hengsberger, Samuel Roth, Pierre Brodard

CHIMIA International Journal for Chemistry,  2016, vol. 70, no. 9, pp. 649-650

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Characteristics of plasma sprayed coatings produced from carbon nanotube doped ceramic powder feedstock
Article scientifique ArODES

Sudhakar C. Jambagi, Simanchal Kar, Pierre Brodard, P. P. Bandyopadhyay

Materials Design,  2016, vol. 112, pp. 392-401

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Résumé:

Incorporation of carbon nanotubes (CNT) in thermally sprayed ceramic coatings is expected to improve its properties. Three ceramic powders were doped with CNT using three methods, namely, dry mixing, mixing in alcohol and heterocoagulation, a colloidal processing technique. Plasma sprayed coatings prepared from these powders were characterized for their microstructure, phases, retention and distribution of CNT, hardness, porosity, fracture toughness, elastic modulus and ultrafine microstructural features. Raman spectroscopy revealed that the CNT could be protected during plasma spraying with limited damage, and CNT was distributed homogeneously in the coatings produced from the heterocoagulated powders. The coating obtained from the heterocoagulated powder was found to possess the highest hardness and least porosity among the coatings investigated. CNT had been found to bridge the splats and thus, enhance coating cohesion. Compared to pure alumina coatings, heterocoagulated coatings demonstrated around 23% and 20% increase in the indentation fracture toughness and elastic moduli, respectively, with the addition of 1 wt% CNT. Transmission electron micrographs showed the formation of an interlayer in the matrix-CNT interface.

New kinetic approach for evaluation of hazard indicators based on merging DSC and ARC or large scale tests
Article professionnel ArODES

Bertrand Roduit, Marco Hartmann, Patric Folly, Alexandre Sarbach, Pierre Brodard, Richard Baltensperger

Chemical Engineering Transactions (CEt),  2016, vol. 48, pp. 37-42

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Résumé:

The present study describes two methods of evaluation of hazard indicators such as Self Accelerating Decomposition Temperature (SADT) or Time to Maximum Rate under adiabatic conditions (TMRad) from the results of the experiments performed in mg scale by Differential Scanning Calorimetry (DSC). We discuss here: (i) the kinetic workflow in which the kinetic parameters of the investigated reaction evaluated from the DSC are used with the heat balance of the system and (ii) a novel merging approach in which DSC data are simultaneously considered with the results of other, temperature recorded experiments as e.g. Accelerating Rate Calorimetry (ARC), large scale experiments as e.g. cookoff, Dewar or SADT determination according to STANAG 4383 and UN regulations (Tests H.4 and H.1), respectively. The commonly kinetic-based approach is discussed and its results confirmed by those obtained in common project with Federal Institute for Materials Research and Testing, Berlin, Germany (BAM) in which the SADT for AIBN was investigated. The novel merging approach is illustrated by the results of the linked DSC-UN test H.1 data and DSC-ARC results applied for SADT determination and for evaluation of TMRad for any starting temperature for AIBN.

2015

Thermal decomposition of AIBN, Part B :
Article scientifique ArODES
simulation of SADT value based on DSC results and large scale tests according to conventional and new kinetic merging approach

Bertrand Roduit, Marco Hartmann, Patrick Folly, Alexandre Sarbach, Pierre Brodard, Richard Baltensperger

Thermochimica Acta,  2015, vol. 621, pp. 6-24

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Résumé:

The paper presents the results of the common project performed with the Federal Institute for Materials Research and Testing, Berlin, Germany (BAM) concerning the comparison of the experimental results with simulations based on the application of the kinetic-based method and heat balance of the system for the determination of the self accelerating decomposition temperature (SADT). The substantial potential of the kinetic-based method is illustrated by the results of the simulation of SADT of azobisisobutyronitrile (AIBN). The influence of sample mass and overall heat transfer coefficient on the SADT values were simulated and discussed. Simulated SADT values were verified experimentally with a series of large-scale experiments (UN test H.1 [1]) performed with packaging of 5, 20 and 50 kg of AIBN in an oven at constant temperatures. Additionally, the results of small-scale test H.4 for SADT determination based on the heat loss similarity as described in details in the UN Manual [1] were compared with the simulated data based on kinetic approach. The paper presents also the basic principles of a new kinetic analysis workflow in which the heat flow traces (e.g., DSC) are simultaneously considered with results of large-scale tests as e.g., H.1 or H.4. Application of the newly proposed kinetic workflow may increase accuracy of simulations of SADT based on results collected in the mg-scale and considerably decrease the amount of expensive and time consuming experiments in kg-scale tests.

Distribution of silica-coated silver/gold nanostars in soft- and hardwood applying SERS-based imaging
Article scientifique ArODES

Christoph Geers, Laura Rodriguez-Lorenzo, Maria Ines Placencia Peña, Pierre Brodard, Thomas Volkmer, Barbara Rothen-Rutishauser, Alke Petri-Fink

Langmuir,  2015, vol. 32, no. 1, pp. 274-283

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Résumé:

Nanoparticles (NPs) in aqueous suspension have just begun to be exploited for the preservative treatment of wood. However, at present, there is very little information available on the distribution of NPs in wood after impregnation, due to associated analytical challenges. In this study, we present the detection of model NPs in softwood and hardwood by surface-enhanced Raman spectroscopy (SERS). SERS is a highly sensitive analytical method requiring no fluorescent labeling. The NP distribution after impregnation is evaluated with one representative species of the two wood types. To show the feasibility of the method, we prepared SERS-active Au/Ag nanostars coated with silica to act as a model NP system. We show herein that NPs can be imaged in very low quantities in both wood types without any matrix interactions. The presence of the NPs in the wood was confirmed by scanning electron microscopy (SEM) imaging and energy dispersive X-ray analysis (EDX). The fast detection of NPs in a complex matrix, without complicated sample preparation, marks a huge step forward in the development and application of nanotechnology for wood preservation and the quest to optimize the properties of one of the world’s most important raw materials.

2014

Une poignée d'épée de type "Rheingönheim" à Marsens
Article professionnel ArODES

Julie Schenk, Pierre Brodard, Samuel Roth

Cahiers d'archéologie fribourgeoise = Freiburger Hefte für Archäologie,  2014, Bd. 16, pp. 42-57

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Résumé:

Un lot de fragments et mues esquilles d'os découvert à Marsens/En Barras dans un contexte fin Ier/début IIe siècle après J.-C. permet de restituer un pommeau de type "Rheingönheim" provenant d'une poignée de spatha, l'épée longue caractéristique de la cavalerie romaine.

Surface chemistry at swiss universities of applied sciences
Article professionnel ArODES

Pierre Brodard, Marc E. Pfeifer, Christian D. Adlhart, Uwe Pieles, Patrick Shahgaldian

CHIMIA,  2014, vol. 68, no. 7-8, pp. 560-562

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Résumé:

In the Swiss Universities of Applied Sciences, a number of research groups are involved in surface science, with different methodological approaches and a broad range of sophisticated characterization techniques. A snapshot of the current research going on in different groups from the University of Applied Sciences and Arts Western Switzerland (HES-SO), the Zurich University of Applied Sciences (ZHAW) and the University of Applied Sciences and Arts Northwestern Switzerland (FHNW) is given.

Determination of thermal hazard from DSC measurements. Investigation of self-accelerating decomposition temperature (SADT) of AIBN
Article scientifique ArODES

Bertrand Roduit, Marco Hartmann, Patrick Folly, Alexandre Sarbach, Pierre Brodard, Richard Baltensperger

Journal of Thermal Analysis and Calorimetry,  2014, vol. 117, pp. 1017-1026

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Résumé:

The method of determination of the thermal hazard properties of reactive chemicals from DSC experiments is illustrated by the results of SADT simulations performed with azobisisobutyronitrile (AIBN). The kinetics of decomposition of AIBN in the solid state was investigated in a narrow temperature window of 72–94 °C, just below the sample melting. The kinetic parameters of the decomposition were evaluated by differential isoconversional method. The very good fit of the experimental results by the simulation curves, based on the determined kinetic parameters, indicated the correctness of the kinetic description of the process. Application of the kinetic parameters, together with the heat balance performed by numerical analysis, allowed scale-up of thermal behaviour from mg- to kg-scale and simulation of SADT. The study presents the evaluation of the influence of the overall heat transfer coefficient U on the SADT value. The results obtained clearly illustrate also the dependence of SADT on the sample mass. The tenfold increase of the mass from 5 to 50 kg results in the decrease of the SADT from 50 to 43 °C. Determination of the reaction kinetics, describing the rate of heat generation, and the heat balance in the system, based on Frank-Kamenetskii approach, was calculated using AKTS Thermokinetics and Thermal Safety software.

Impact of composite structure and morphology on electronic and ionic conductivity of carbon contained LiCoO2 cathode
Article scientifique ArODES

Nam Hee Kwon, Hui Yin, Pierre Brodard, Claudia Sugnaux, Katharina M. Fromm

Electrochimica Acta,  2014, vol. 134, pp. 215-221

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Résumé:

Cathodes in lithium ion batteries consist of an ionic conductor, an electronic conductor and a binder in order to make a composite that is both electronically and ionically conductive. The carbon coating on the cathode material plays a critical role for the electrochemical properties of lithium ion batteries due to the increased electronic conductivity. We explain the relationship between the electrochemical properties and the characteristics of composites prepared using the ball-milling process in this report. We investigated two types of carbonaceous materials (graphite and carbon black) in LiCoO2 electrodes. These selected carbon materials have different characteristics and structure upon ball-milling with LiCoO2. The composite prepared by ball-milling for 5 min leads to better mixing of carbon and LiCoO2, an intimate contact of carbon on LiCoO2, a higher lithium ion diffusion (DLi) than non ball-milled and longer ball-milled composites. On the other hand, a longer time of ball-milling (30 and 60 min) decreases the electronic and ionic conductivity due to an increase of disordered structure of carbon and a thick and dense carbon coating layer on LiCoO2 particles, preventing the diffusion of lithium ions, respectively.

2013

Non-destructive localization and identification of active pharmaceutical compounds by Raman chemical imaging
Article professionnel ArODES

Pierre Brodard, Samuel Roth, Olivier Vorlet

CHIMIA,  2013, vol. 67, no. 12, pp. 923-924

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Résumé:

Raman spectroscopy is a powerful and non-destructive technique for chemical and structural identification. Based on inelastic scattering of laser light by molecular vibrations, the analysis can be localized on a microscopic area when combined with a microscope. Thus, by moving the sample under the microscope objective and recording a Raman spectrum at each point, a map of the intensity of specific Raman bands can be generated, effectively creating a chemical image of the sample at the microscale. Here, we present an application of this technique for identifying and localizing active pharmaceutical ingredients in a polymer matrix.

Kinetics of the chrysotile and brucite dehydroxylation reaction :
Article scientifique ArODES
a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

Roy Trittschack, Bernard Grobéty, Pierre Brodard

Physics and Chemistry of Minerals,  2014, vol. 41, pp. 197-214

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Résumé:

The dehydroxylation reactions of chrysotile Mg3Si2O5(OH)4 and brucite Mg(OH)2 were studied under inert nitrogen atmosphere using isothermal and non-isothermal approaches. The brucite decomposition was additionally studied under CO2 in order to check the influence of a competing dehydroxylation/carbonation/decarbonisation reaction on the reaction kinetics. Isothermal experiments were conducted using in situ high-temperature X-ray powder diffraction, whereas non-isothermal experiments were performed by thermogravimetric analyses. All data were treated by model-free, isoconversional approaches (‘time to a given fraction’ and Friedman method) to avoid the influence of kinetic misinterpretation caused by model-fitting techniques. All examined reactions are characterised by a dynamic, non-constant reaction-progress-resolved (‘α’-resolved) course of the apparent activation energy E a and indicate, therefore, multi-step reaction scenarios in case of the three studied reactions. The dehydroxylation kinetics of chrysotile can be subdivided into three different stages characterised by a steadily increasing E a (α ≤ 15 %, 240–300 kJ/mol), before coming down and forming a plateau (15 % ≤ α ≤ 60 %, 300–260 kJ/mol). The reaction ends with an increasing E a (α ≥ 60 %, 260–290 kJ/mol). The dehydroxylation of brucite under nitrogen shows a less dynamic, but generally decreasing trend in E a versus α (160–110 kJ/mol). In contrast to that, the decomposition of brucite under CO2 delivers a dynamic course with a much higher apparent E a characterised by an initial stage of around 290 kJ/mol. Afterwards, the apparent E a comes down to around 250 kJ/mol at α ~ 65 % before rising up to around 400 kJ/mol. The delivered kinetic data have been investigated by the z(α) master plot and generalised time master plot methods in order to discriminate the reaction mechanism. Resulting data verify the multi-step reaction scenarios (reactions governed by more than one rate-determining step) already visible in E a versus α plots.

Green synthesis of mono- and disubstituted pyridine via aromatic nucleophilic substitution
Article professionnel ArODES

Ennio Vanoli, Roger Marti, Jean-Pascal Bourgeois, Pierre Brodard, Romain Despland, Justine Horner, Fabrice Gallou

CHIMIA,  67, 9, 656-657

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Non-destructive Localization and Identification of Active Pharmaceutical Compounds by Raman Chemical Imaging
Article scientifique

Brodard Pierre, Roth Samuel, Vorlet Olivier

CHIMIA, 2013 , vol.  67, no  12, pp.  923-924

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2014

Visualization of gold/silver nanostars in wood by surface enhanced Raman spectroscopy
Conférence ArODES

Christoph Geers, Laura Rodriguez-Lorenzo, Maria Inés Placencia Peña, Pierre Brodard, Thomas Volkmer, Barbara Rothen-Rutishauser, Alke Petri-Fink

Proceedings of the 45th IRG Annual Meeting, 11-15 May 2014, St George, Utah, USA

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Résumé:

Nanotechnology is a fast growing up-to-date technology and ventures expeditiously in the wood preservative market. However, there is still a huge lack of understanding about the interaction and incorporation of nanoparticles (NSs) in wood. Surface-enhanced Raman scattering (SERS) offers unique advantages as an analytical tool with a high selectivity and sensitivity without matrix interference. Here, we design and fabricate SERS-tagged silver/gold nanostars (NSs), coated with a silica shell encapsulating nile blue A (NBA), as potential platforms for SERS imaging. These NSs can be pressure-impregnated in different wood types (pine and beech) due their optimal size (< 100 nm), allowing for their rapid and accurate identification and localization in the wood samples. For comparison and visualization of the NSs, the samples were coated with a carbon layer for analysis in a scanning electron microscope (SEM). We demonstrate that SERS provides advantages over SEM. The NSs can be visualised by SERS without coating of the samples. In addition, no vacuum is needed to image the NSs, and the excitation laser line (633 nm) used applies a lower energy for detection of NSs than the electron beam of the SEM. These facts lead to a much decreased formation of artefacts during NSs detection in wood. This quick and easy method can be used for fast analysis of new nanoparticle-based wood preservative systems, which leads to a better understanding of impregnation processes, providing an essential step in finding fundamentally new wood preservatives.

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