DRawing of nanoparticlEs-doped Amorphous Materials – Nice-DREAM

Given the difficulties of characterization of nanoparticles formed by phase separation and the lack of models to describe such phenomena in the case of multi-element compositions as envisaged in this project, computer simulations are very important tools to develop. This project initiates the implementation of the first molecular dynamics simulations accounting for the formation of nanoparticles in the SiO2-MgO system. Such simulations are also developed to simulate the drawing.

The main outstanding results at the moment are:
- Experimental and numerical evidence a variation of the composition of vitreous nanoparticles, formed by phase separation, for sizes smaller than 20 nm. Numerical simulations have been published and honored by the cover of The Journal of Chemical Physics (2015).
- Simulation tools have been developed to model the drawing process of pure silica preform. The simulations enabled to explain the origin of the anisotropy induced in a fiber (an article has been published in Journal of Non Cryst. Solids). Such simulations will be considered in the case of preforms containing nanoparticles.

The next step of the project will take advantage of specific manufacturing processes to prepare glasses containing luminescent ions (LI) doped DN with controlled sizes. In particular, we will focus on the relationship between the spectroscopic properties of the LI and their local environment and study the behavior of nanoparticles in the drawing conditions. A proof of concept will be realized at the end of the project.

Publications
X. Bidault, S. Chaussedent, W. Blanc, D.R. Neuville, « Deformation of silica glass studied by molecular dynamics: Structural origin of the anisotropy and non-Newtonian behavior », Journal of Non-Crystalline Solids, 433, 38-44, 2016
X. Bidault, S. Chaussedent, W. Blanc, « A simple transferable adaptive potential to study phase separation in large-scale xMgO-(1-x)SiO2 binary glasses«, The Journal of Chemical Physics, 143, 154501, 2015
Communications
X. Bidault, S. Chaussedent, W. Blanc, D.R. Neuville, « Structural anisotropy induced by deformation in silica glass » In : 13th International Conference on Frontiers of Polymers and Advanced Materials (ICFPAM), Marrakech – Maroc, 2015

D.R. Neuville, “Rheology and nano-structural change of glasses and melts: implications for earth and material sciences”. ICG Shangai, 2016. (conf. invitée)
X. Bidault, J. Turlier, S. Chaussedent, W. Blanc, « Un potentiel adaptatif simple pour la modélisation par Dynamique Moléculaire de la séparation de phase dans un verre de silice binaire », Journées Verre, Nice, 2015

M. Vermillac, J.F. Lupi , S. Trzesien, M. Ude, J.B. Tissot, H. Fneich, A. Mehdi, O. Totterau, P. Vennegues, C. Kucera, J. Furtick, J. Ballato, W. Blanc, « Vie et mort d'une nanoparticule de LaF3 dans la silice à haute température », Journées Verre, Nice, 2015

H. Francois-Saint-Cyr, I. Martin, P. LeCoustumer, C. Hombourger, D. Neuville, D. J. Larson, T. J. Prosa, E. Gonthier, L. Geai , C. Guillermier, W. Blanc, « Variation of sub-10nm nanoparticle chemical composition in glass revealed by Atom Probe Tomography », XIVe colloque de la Société Française des Microscopies, Sfµ2015, Nice, 2015
Chapitre de livre
W. Blanc, “Luminescence properties of rare earth ions doped in insulating nanoparticles embedded in glassy hosts”, in «From glass to crystal: nucleation, growth and phase separation, from research to applications« Ed. Neuville D.R., Cormier L., Caurant D. et Montagne L, EDP-Sciences, 2016

This project aims to develop an original optical fibre amplifier, for photonic applications based on the encapsulation of luminescent ions in dielectric nanoparticles (DNP). It relates in particular to the study of changes of DNP during the drawing step, a key step which is a technological barrier for the development of these new fibres.

The optical fibre market is currently growing in areas such as telecommunications, machining, medicine, and sensors. This expansion is underpinned by silica fibre (SiO2) glass which has many mechanical and economic advantages over alternative hosts. Nevertheless, optical amplifiers based on this glass are limited to a relatively few narrow bands in the near-infrared. The development of new applications based on optical fibres requires rethinking the nature and structure of silica-based fibre cores to achieve “augmented” amplification properties. The encapsulation of luminescent ions in DNP in principle allows control of the environment, and the engineering, of spectroscopic properties. New optical fibres are developed according to this principle. They can combine the optical and mechanical advantages of silica and provide spectroscopic properties that do not otherwise exist in this glass.

The most promising route to a new family of optical fibres is based on the in-situ synthesis of DNP during the manufacture of the preform. There are several methods to prepare a preform; however they all share the drawing step, requiring extreme conditions of temperature and mechanical constraint. An 125-µm optical fibre is obtained by drawing a preform (diameter ~1cm) at high temperature (> 2000 °C). Currently there is no model or knowledge to engineering spectroscopic properties of luminescent ions doped DNP in these conditions.

The fate of DNP during the drawing step is therefore the major question to elucidate for the development of such optical fibres. In this context, our unique approach is based on the study of model samples to overcome the difficulties encountered with fibre characterization. The work is organized in four stages over 42 months: (1) preparation of glasses containing luminescent ions doped DNP, (2) study of DNP properties at high temperature, (3) study of the elongation at high temperature and (4) demonstrate an application proof of concept. The experiments will be based on theoretical modelling and molecular dynamics simulations. The main objective is to determine the transfer function of the drawing step, i.e. to determine the characteristics of the nanoparticles in the preform to obtain the desired properties in the fibre.

With this aim in mind, we have assembled a consortium with expertise in the fields of glass-ceramics, optical fibres, nanomaterials, phase separation in silicate materials, and thermodynamics. This proposal brings together four academic research institutes, known as top-ranked groups in their respective domains. Their global scientific and technological proficiency now spreads over various fields dealing with materials, with already initiated collaborations in these domains : materials fabrication and characterization, optics, physical-chemistry, spectroscopy, and numerical simulations.

Founded on mature multidisciplinary experimental techniques, the project will cultivate the production and analysis of a large set of samples and data of primary importance in understanding DNP production in silica based optical fibre. The outcome from which will be a notable increase of the basic scientific knowledge in this photonic materials field, whereas the technological findings should have a large impact, particularly in Key Enabling Technologies such as photonics, nanotechnology, advanced materials and advanced manufacturing systems.