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Reference : UMR125-PIEJOP-001
Workplace : AUBERVILLIERS
Date of publication : Monday, November 04, 2019
Scientific Responsible name : Pierre Jop
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 January 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Thermal effects on micro-structural evolution during capillary-driven sintering. During the sintering process, particles deform at elevated temperatures through various mechanisms and then reform (i.e. densify) on cooling to produce either a fully dense or a partially dense material. The porosity of the reformed structure (and ultimately the functional quality of the final product) is affected by the microstructural changes that occur on rearrangement; for example, a high surface tension in the melt liquids (which is found with molten oxides) can induce capillary forces, which are known to detract from optimal sintering conditions. However, monitoring microstructural changes has historically proved challenging and studies to date have mainly focused on phenomenological characterization. Fortunately, recent advances in synchrotron X-ray tomography enable the fast acquisition (in a few seconds) of 3D images with a high enough spatial resolution (1μm) to examine the evolution of liquids or of granular materials in-situ. The PhD student will therefore use the latest in-situ X-ray tomography techniques to systematically explore the effects of capillary interactions in the melt liquids on porosity. She/he will first study the sintering of powder mixtures when a component has a lower fusion temperature or using inert grains (e.g. fusible materials, such as glass and oxides, and refractory materials) so that only a fraction of the structure will transform into a liquid phase. Using the synchrotron at ESRF, she/he will then examine the structural evolution and phase transformation and then explore how to control porosity in heterogeneous systems using the liquid phase produced at high temperatures by systematically changing the sintering conditions and the initial packing structure. She/he will also establish the sintering conditions at which the collapse of the granular structure under the capillary forces can be avoided and characterize the final structure and porosity of different initial structured aggregates. She/he will then use model granular materials (polymers, ice) to assess the capillary effects by changing the surface tension, viscosity or wettability.
This PhD Project will take place mostly at the Glass surface and Interfaces, localized in the RD research center of Saint-Gobain Research Paris, in Aubervilliers. Some experiments will be made at the ESRF synchrotron in Grenoble and exchanges will be made between our laboratory and another laboratory (SIMAP) where another PhD student is working in a related subject.
Constraints and risks
The candidates cannot have spent more than 12 months in France (work or studies) during the last 3 years immediately before the recruitment date.
This PhD project is part of the research program MATHEGRAM https://www.surrey.ac.uk/mathegram which is a network of 15 projects on the subject of the granular materials at high temperature. The gross salary is therefore around 3000€ gross monthly.
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