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LGP2 - Ph.D. thesis defended in 2021


15 December 2021 - Materials, Mechanical, Civil Engineering, Electrochemistry
NanoSteamEx: production of microfibrillated cellulose by steam explosion
Evelyne MAURET, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Nicolas BROSSE, Professor, Université de Lorraine / LERMAB
Micro and nanofibrillated cellulose (MNFC) exhibits remarkable properties with high added value applications in various fields. In recent years, there has been a growing interest in lignin-containing micro and nanofibrillated cellulose (L-MNFC) produced from different lignocellulosic materials. However, current L-MNFC production processes are energy-intensive, which limits their use.
Steam explosion (SteamEx) is an efficient lignocellulose pretreatment process, accessible on an industrial scale. The objective of this study is to propose an energy-efficient and environmentally friendly process, involving pre-treatment by SteamEx, in order to manufacture L-MNFC from beech wood and Eucalyptus globulus bark, then used for the production of nanopapers and the reinforcement of wood adhesives.
The originality of this study is twofold:
•    L-MNFC with different lignin contents are produced from beech wood and eucalyptus bark (two understudied biomasses for MNFC production, in particular eucalyptus bark).
•    The cooking step of the raw material (pulping) was carried out in a SteamEx apparatus combining the effects of alkaline delignification and explosive defibration. Pulping was followed by a refining and a grinding step. The chemical composition, morphology and mechanical properties of the produced L-MNFC gels and nanopapers have been studied.
The results demonstrated the possibility of producing L-MNFC by SteamEx. They have a quality comparable to that of L-MNFC produced by conventional processes (involving chemical and/or enzymatic treatments) while benefiting from a shorter reaction time. SteamEx promotes the detachment of lignin from the fibers by forming spherical nanoparticles dispersed in the L-MNFC gels.
•    The L-MNFC produced from eucalyptus bark are formed of nanofibrils with diameters between 5 and 100 nm and coarser elements. With quality indices of ≈ 60, they are used as reinforcements in Urea-Formaldehyde adhesives to improve the mechanical properties of particleboard.
•    The L-MNFC produced from beech wood presents quality index between 60 and 80. They are used to produce nanopapers with Young's moduli of 8 - 9 GPa.
Other members of the jury
Sami BOUFI, Professor, Université de Sfax, Tunisie ♦♦ Aurore RICHEL, Professor, Université de Liège, Belgique ♦♦ Bernard CATHALA, Research Director, INRAE Nantes

Bastien MICHEL

December 3, 2021 - Materials, Mechanical, Civil Engineering, Electrochemistry
Functionalized nanocelluloses for biomedical applications
Alain DUFRESNE, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Julien BRAS, Associate Professor HDR, Grenoble INP-Pagora / LGP2 ♦♦ Kristin SYVERUD, Professor, NTNU, Norvège ♦♦ Ellinor B. HEGGSET, Researcher, RISE PFI, Norvège
Combining oxidized cellulose nanofibrils (toCNF) and various β-cyclodextrin (β-CD) derivatives makes it possible to design high-performance materials for biomedical applications. Although promising, this combination faces certain challenges, in particular the characterization of this toCNF / β-CD association.
This thesis therefore consists in characterizing the phenomena of adsorption between toCNF and β-CD in order to improve the release of active ingredients which are poorly soluble in water and, consequently, to promote the antimicrobial properties of these materials. First, the production of toCNF / β-CD materials was reported, with an investigation on the impact of various process parameters on water sorption and mechanical properties. The adsorption of β-CD was characterized via different experimental tools: it was shown that β-CD derivatives adsorb up to 10 times more onto toCNF than β-CD. The formation of an inclusion complex between a model active ingredient and the various β-CD has been characterized in depth. Finally, the functionalization of toCNF with β-CD showed improvement of the antimicrobial properties of films with increased efficiency for carboxymethylated-β-CD.
By improving knowledge of the interactions between nanocellulosic materials and different cyclodextrins, the results of this project constitute a significant step towards applications in various fields: biomedical, pollution control, etc.
Other members of the jury
Bernard CATHALA, Research Director, INRAE Nantes ♦♦ Naceur BELGACEM, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Carmen FREIRE, Professor, Université d’Aveiro, Portugal ♦♦ Sophie FOURMENTIN, Professor, Université Littoral Côte d’Opale


27 October 2021 - Materials, Mechanical, Civil Engineering, Electrochemistry
Chemical modification and multi-function applications of nanocellulose
Alain DUFRESNE, Professor, Grenoble INP-Pagora / LGP2
The aim of this project was to investigate some functional application of nanocellulose. To improve the interfacial compatibility between nanocellulose and a hydrophobic matrix, active thiol groups were introduced at the reducing end of cellulose nanofibrils. Covalent cross-links were formed between thiol groups and double bonds of natural rubber via photochemically initiated thiol-ene reactions. To obtain highly conductive composites with low percolation threshold and adequate mechanical properties, cellulose nanocrystal/graphene oxide/natural rubber nanocomposites hosting a 3D hierarchical multiscale conductive network were developed. An aerogel was prepared by integrating oxidized cellulose nanofibrils, cationic cellulose nanocrystals, sodium alginate and carbon nanotubes. Good EMI shielding, low density, high conductivity and good mechanical strength were achieved.
Other members of the jury
Ana VILLAREZ, Research Director, INRA Pays de la Loire, Nantes ♦♦ Etienne FLEURY, Professor, INSA Lyon ♦♦ Nadia EL KISSI, Research Director, Laboratoire Rhéologie et Procédés, Grenoble

Etienne MONTET

17 September 2021 - Fluid Mechanics, Energy, Processes
Ph.D. title
Investigation of the consequences of the use of ozone in the bleaching of cellulosic fibres
Christine CHIRAT, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Dominique LACHENAL, Emeritus Professor, Grenoble INP-Pagora / LGP2
Production of paper grade pulp is still relying on the use of chlorine dioxide in ECF bleaching sequences in spite of the AOX pollutants this process releases in the environment and in paper products. The shift towards the use of TCF bleaching sequences will be necessary and is already made possible by the total substitution of chlorine dioxide for ozone, a greener and more powerful oxidant.
This thesis establishes that an ozone-based TCF bleached pulp can reach brightness and strength properties equivalent to that of a conventional ECF pulp. Furthermore, a UV Resonance Raman spectroscopy study demonstrates the superiority of ozone (associated with hydrogen peroxide) in stabilizing the brightness, compared to the joint use of chlorine dioxide and peroxide. An analysis by direct dissolution of the cellulose in a DMAc / LiCl mixture (8%) and size exclusion chromatography indicates that the mechanical quality of the TCF pulp is preserved because the degradation of cellulose by the different ozone stages is uniform in fibres.
Replacing chlorine-based bleaching chemicals with reagents such as oxygen, hydrogen peroxide and ozone provides significant soda savings in the sequence as oxidized white liquor can be used as alkaline agent in the bleaching alkaline stages without disturbing the recovery cycle of the mill. Although recycling of the bleaching effluent induces an overconsumption of ozone, results presented here show that this may be the most cost-effective scenario. This paves the way for the development of highly competitive TCF bleaching sequences for the production of bleached kraft pulp.
Other members of the jury
Gérard MORTHA, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Tapani VUORINEN, Professor, Université d'Aalto, Finland ♦♦ Anne-Laurence DUPONT, CNRS Research Director, Centre de Recherche sur la Conservation, Paris ♦♦ Adriaan R.P. VAN HEININGEN, Professor, Université du Maine, USA


25 June 2021 - Materials, Mechanical, Civil Engineering, Electrochemistry
Study of the molecular diversity of soluble hemicellulose oligosaccharides from wood autohydrolysates
Christine CHIRAT, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Claire BOISSET, Researche Engineer, Cermav / CNRS
Facing climate change and the near end of the oil age led us to rethink our consumption patterns and energy models, to insure a sustainable future for human beings. In this way, the biorefinery plays an important role and is a key concept to bring a part of the solution, exploiting the potential of biomass, which is renewable and widely available, for energy production and chemicals, materials, human health, and agri-food products manufacturing. Hence, this project aims at valorizing wood hemicelluloses in the frame of a lignocellulosic biorefinery integrated in a kraft pulp mill.
Hemicelluloses are complex heteropolysaccharides accounting for up to one third of wood and are among the most abundant biopolymers on Earth. Both softwood and hardwood chips industrial mixtures were used for hemicelluloses oligomers extraction prior to the kraft process through a low-tech and green process (without using any chemicals) named autohydrolysis. This pretreatment step allows for the solubilization of oligosaccharides, monosaccharides, lignin fragments and other small molecular weight organic compounds. The chemical composition of these wood hydrolysates depends on wood species and autohydrolysis severity. The main objective of the thesis is to design a sort of universal scheme of analytical methods that can be applied to any kind of hydrolysate in order to identify, quantify and isolate its hemicelluloses families.
The study of the molecular diversity of soluble oligosaccharides containing liquors produced at two temperature levels  (170 and 150°C) is based on several purifications’ steps before analysis. First of all, membrane filtration is used with different molecular weight cut-offs to classify and separate oligomers and impurities according to their size. In a second part, soluble lignin and sugar degradation products generated during autohydrolysis are removed by adsorption on activated charcoal. Less polydisperse and 99% pure oligosaccharides mixtures are thus obtained thanks to the optimization and combination of these two techniques of purification. Nevertheless big losses of hemicelluloses are triggered by these treatments between 70 and 80% compared to the raw hydrolysate.
In the end, the last chapter of experiments deals with the final purification and characterization steps of these purified samples which are performed by size exclusion liquid chromatography and mass spectrometry analyses. This chromatographic technique operating at low pressure is an interesting tool for the separation of neutral oligomers from hexuronic acid substituted oligomers in both hardwood and softwood extracts. Also, elimination of recalcitrant lignin carbohydrates complexes was achieved for some fractions as well as the isolation of specific bioactive molecules of low degree of polymerization (potential nutraceutical applications).
Autres membres du jury
Stéphane BAUP, Professor, Université Grenoble Alpes  ♦♦ Pierre-Yves PONTALIER, Associate Professor HDR, Toulouse INP ♦♦ Ana Paula DUARTE, Professor, Universidade da Beira Interior, Portugal ♦♦ Diane JOUANNEAU, Research Engineer, CNRS Bretagne et Pays de la Loire


26 March 2021 - Materials, Mechanical, Civil Engineering, Electrochemistry
Fabrication and optimization of abiotic bioelectrodes for implantable glucose biofuel cells
Naceur BELGACEM, Professor, Grenoble INP-Pagora / LGP2
This work aimed at optimizing the bioelectrode’s manufacturing for implantable glucose biofuel cells using different coating technics.
An abiotic catalyst composed of graphene doped with iron and nitrogen was used to make biocathodes. Two deposition methods were used to fabricate two-dimensional biocathodes: ultrasonic spraying and doctor blade coating.
The biocathodes produced by ultrasonic spraying exhibited low current densities (0.52 µA / cm²) due to the small amounts of active material deposited. The biocathodes produced by doctor blade coating – this method makes it possible to deposit larger quantities of material – have delivered current densities of 70 µA / cm². These biocathodes have shown stability in vitro for two years. They were also implanted in vivo in a rat: a quasi-absence of inflammatory reaction and an ability to electro-catalyze oxygen were observed after five months of implantation.
The study then turned to the development of three-dimensional bioelectrodes. Abiotic biocathodes were produced by 3D printing, with a controlled macroporosity facilitating the diffusion of the substrate within the electrode. Two methods were applied: the use of the catalyst directly in the initial ink formulation and the creation of catalytic sites in situ in the 3D shape. To carry out this approach, the ink formulation and printing parameters have been optimized.
Maximum current densities of the order of 400 µA / cm2 were obtained by the first method. The second method improved electrochemical performance (factor 1.5). This can be explained by the increase in the conductivity as well as the porosity of the bioelectrodes due to the pyrolysis step. The biocathodes from the first method were assembled in hybrid biofuel cells and implanted in the intra-abdominal region of rats. This biofuel cells remained functional even after an implantation period of three months. Over this same period, a quasi-absence of inflammatory reaction was observed, highlighting the biocompatibility of the 3D-printed biocathodes.
Finally, a study comparing two enzymatic anodes made from cellulose microfibrils (MFC) and chitosan demonstrated that the substitution of chitosan by MFC improves the anode electrochemical performance and kinetic constants.
Autres membres du jury
Philippe CINQUIN, Professor, Faculté de médecine de Grenoble  ♦♦ Sophie TINGRY, CNRS Research Director, Institut Européen des Membranes, Montpellier ♦♦ Stéphane MARINESCO, Researcher, Université Claude Bernard Lyon 1 ♦♦ Christophe MARQUETTE, CNRS Research Director, Université Claude Bernard Lyon 1


19 January 2021 - Materials, Mechanical, Civil Engineering, Electrochemistry
Industrial application of pretreatments for obtaining high quality cellulose nanofibrils
Julien BRAS, Associate Professor HDR, Grenoble INP-Pagora / LGP2 ♦♦ Naceur BELGACEM, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Denis CURTIL, Research Engineer, Grenoble INP-Pagora / LGP2
The development of biobased materials with a wide range of properties has become a key issue in today’s society, to move towards a durable bioeconomy. In this context, cellulose nanofibrils (CNF) are very promising, due to their interesting mechanical, optical, rheological and barrier properties.  
However, several technological challenges still restrain their cost-efficient production at the industrial scale, such as the toxicity issues of the cellulose pretreatments or the high energy consumption of the mechanical fibrillation processes. This project in collaboration with Arjowiggins (scientific contact: Gaël Depres) via a CIFRE-ANRT funding aims at developing innovative pretreatments and optimize several mechanical fibrillation processes, with an objective of producing high quality CNF at the industrial scale.
First, three pretreatments were studied, involving a coupled alkaline and enzymatic treatment, the adsorption of a polyelectrolyte, and in situ enzymatic hydrolysis at high solid content during fibrillation by twin-screw extrusion. Then, a disk refining process was optimized for CNF production, for the implementation of these pretreatments at the pilot scale. Several industrial trials with a specific tracing paper refining line also underlined the relevance of this process for large scale CNF production, leading to a significant decrease of energy consumption compared to conventional processes. Finally, disk refining was combined with twin-screw extrusion, ultra-fine grinding and homogenization, respectively. This strategy enabled to overcome the limitation of CNF quality encountered with the use of refining alone.
The results of this project contribute to the knowledge on pretreatments and processes for cellulose nanofibrils production, and are a step towards their efficient production at industrial scale.
Other members of the jury
Evelyne MAURET, Professor, Grenoble INP-Pagora / LGP2  ♦♦ Tatiana BUDTOVA, Research Director, MINES ParisTech ♦♦ Orlando ROJAS, Professor, Université de la Colombie-Britannique, Canada ♦♦ Sami BOUFI, Professor, Université de Sfax, Tunisia ♦♦ Gaël DEPRES, Research Director, Arjowiggins France


29 January 2021 - Materials, Mechanical, Civil Engineering, Electrochemistry
Development of a robotic cell for printing electronic circuits on the surface of 3D objects and industrial applications.
Davide BENEVENTI, CNRS Research Director, Grenoble INP-Pagora / LGP2 ♦♦ Didier CHAUSSY, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Philippe MARIN, Associate Professor, Grenoble INP / G-SCOP
Objective: to produce a 6-axis robotic cell to print electronic circuits on objects of any shape, suitable for prototyping and the production in small series of 3D objects integrating surface electronics.
The proposed manufacturing method includes several phases: digitization, mesh construction, circuit projection, speed analysis and printing. This flexible process is very useful for prototyping and small series applications where it is necessary to frequently change the substrate and the dimensions of the 3D object.
An offline programming approach allows to print conductive trajectories on 3D objects and to automatically generate the trajectory and program of the printing robot. A methodology to predict the morphology of the circuit by adapting the projection parameters according to the trajectory and the speed of the 6-axis robot has been designed.
An interface dedicated to the management of the entire process, from circuits design to the automatic generation of the printing program, has been created thus allowing operators not expert in robotics to use the cell.
Finally, prototypes were presented.
Other members of the jury
Evelyne MAURET, Professor, Grenoble INP-Pagora / LGP2  ♦♦ Yassine HADDAB, Professor, Université de Montpellier  ♦♦ Jean-Pierre RASKIN, Professor, École Polytechnique de Louvain

Date of update February 14, 2022

Université Grenoble Alpes