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LGP2 - Ph.D. thesis defended in 2023

Cécile SILLARD

July 7, 2023 - Materials, Mechanical, Civil Engineering, Electrochemistry
Title
Composites and active materials: lignocellulosic fibers for biobased products
Supervision
Evelyne MAURET, Professor, Grenoble INP - Pagora, UGA / LGP2

Enrique Felix QUESADA SAAVEDRA

June 12, 2023 - Materials, Mechanical, Civil Engineering, Electrochemistry
Title
High performance cellulosic materials to increase the lifespan and reliability of power transformers
Supervision
Gérard MORTHA, Professor, Grenoble INP - Pagora, UGA / LGP2 ♦♦ Nathalie MARLIN, HDR Associate Professor, Grenoble INP - Pagora, UGA / LGP2 ♦♦ Olivier LESAINT, CNRS Research Director, UGA / G2Elab

Marlène SAULAIS

May 5, 2023 - Materials, Mechanical, Civil Engineering, Electrochemistry
Title
Design and production of biobased and non-iridescent structural pigments, by self-assembly
Supervision
Alain DUFRESNE, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Cécile SILLARD, Engineer, LGP2
Abstract
Structural colours are an interesting alternative to chemical colours, potentially toxic or photosensitive, and widely used in industry nowadays. Based on light/matter interactions, structural colour can be produced from bio-based and bio-compatible materials. Photonic systems producing structural colours in Nature are widely studied, and have inspired the scientific community in their attempts to synthesise artificial structural colours. The particularity of natural structures is their design targeting mainly short wavelengths, i.e. blue to green colours. Red in Nature mainly remains a chemical colour. Indeed, red is physically harder to produce, but is a crucial hue in the colour panel for some industries, such as the cosmetic field in which red colours remain chemically-based.
This PhD project aims to produce a red structural pigment, non-iridescent to avoid the angular-dependency of scattered colour, with bio-based and bio-compatible materials (for external uses), and with appropriate synthesis conditions for potential-scale up. As the structural pigment will be produced through a self-assembly process, the first part deals with the synthesis of the nano-building blocks, and their characterisation to conclude about their optical properties. The second part presents the assembly of the building blocks with two different strategies. And finally, the third part tries to go further in the bio-based approach, with the synthesis of new potential building-blocks. This project is at the interface between chemistry and optics, where the former is used as a tool, sometimes being a source of constraints, to produce objects suitable for the latter.

Laëtitia BARDET

March 10, 2023 - Materials, Mechanical, Civil Engineering, Electrochemistry
Title
Optimization of silver nanowire networks for transparent electrodes: fundamental and experimental contributions
Supervision
Daniel BELLET, Professor, Grenoble INP-Phelma / LMGP ♦♦ Aurore DENNEULIN, HDR Associate Professor, Grenoble INP-Pagora / LGP2
Abstract
Transparent electrodes (TEs) are key components of many devices such as solar cells, transparent heaters or touch screens. Indium tin oxide (ITO) has been the most implemented TEs within these devices. However, ITO thin films do not fulfil all the requirements of the next generation of flexible optoelectronics because of its indium scarcity and brittleness. In that context, silver nanowire (AgNW) networks appear as a relevant alternative to ITO thin films. However, their efficient integration for the next generation of flexible TEs is mainly compromised by their nanowire-nanowire junction resistance and, their morphological instability specifically when submitted to stress (i.e. thermal, electrical, humidity).
The main goal of this thesis work is to contribute to a better understanding of both properties and limitations of AgNW networks. First, conventional thermal annealing and capillary-force-induced cold-welding treatments are compared regarding the optimization of network resistance. Moreover, cold-welding treatment can be performed at a temperature of 100 °C. Both post-deposition treatments exhibit similar efficiency for optimizing electrical resistance, at both the macroscale and nanoscale.
Then, the stability of these networks has been successfully enhanced by protecting them with a thin amorphous tin oxide layer deposited by Atmospheric Pressure Spatial Atomic Layer Deposition, at 200 °C. A physical model is introduced describing the in situ reversible behaviour of AgNW networks when subjected to electrical stress. This simple model enables us to predict the associated Joule heating temperature for any applied voltage and initial network resistance.
In addition, an in-depth investigation of the evolution of both in situ structural and electrical properties of AgNW networks during thermal stress have been carried out thanks to simultaneous in situ measurements of X-ray diffraction and electrical resistance. Finally, the integration of AgNW networks as infrared low-emissivity coating is explored.
We clearly believe that this thesis work significantly contributes to maturing AgNW network science and technology for industrial requirements.
Other members of the jury
Aline ROUGIER, CNRS Research Director, Université de Bordeaux ♦♦ Stéphane COLIN, CNRS Research Director, Université Paris-Saclay ♦♦ Jean-Pierre SIMONATO, Research Director, CEA-Liten, Grenoble ♦♦ Matthias PAULY, Associate Professor, Université de Strasbourg ♦♦ Ngoc Duy NGUYEN, Professor, Université de Liège, Belgique ♦♦ Alain SYLVESTRE, Professor, Université Grenoble Alpes

Date of update August 24, 2023

French
LGP2 Laboratoire Génie des Procédés Papetiers
Laboratory of Process Engineering for Biorefinery,
Bio-based Materials and Functional Printing

461 rue de la Papeterie - Domaine universitaire - CS 10065
38402 Saint Martin d’Hères Cedex - France
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