M/F PhD position: Development of multifield electromagnetic levitation for characterisation and processing of metallic materials

Job Description

Thesis Subject

Description of the project.
The thesis is proposed in the frame of the ANR project MultiMAGe which is aimed to develop a versatile experimental setup, based on the coupling of electromagnetic levitation with a DC magnetic field, for the characterization and processing of metals and alloys at high temperatures.
Characterisation of metals in liquid state and study of liquid-solid transformation are essential for initiating or optimising the industrial production, as the latter requires knowledge of high-temperature thermophysical properties of materials as well as an understanding of physico-chemical processes at the free surface, etc.
However, handling liquid metals in a chemically pure state is complicated, because of their high chemical reactivity and high melting temperature, therefore, non-contact techniques are privileged for such studies. Electromagnetic levitation offers certain advantages over other levitation technics (aerodynamics, ultrasonic,…) at is allows relatively large samples to be processed and provides heating of the sample during the levitation via Joule effect.
On a negative side, another intrinsic feature of the EML is the generation of fluid flow within the liquid sample. Under terrestrial conditions, this flow is generally strong and prevails over diffuse heat and mass transfer therefore making measurement of some thermophysical impossible or at least complicate them. Similarly, phase transition is affected by convective heat and mass transport. However, it has been demonstrated that applying a second, DC magnetic field can stabilise the levitating sample and substantially reduce the flow velocity within the liquid. This opens the possibility of performing controlled parametric studies and, ultimately, of extrapolating thermophysical properties towards conditions where convective transport is negligible.
Fundamental questions nevertheless remain regarding the coupling of electromagnetic levitation with the use of a DC magnetic field. In particular, the effects of the intensity, orientation and spatial uniformity of the DC magnetic field on the internal flow and surface oscillations are not yet fully understood. The coupling between fluid flow and heat transfer is also of particular interest for the development of reliable thermophysical-property measurements or well-controlled elaboration process.

Previous developments and open questions.

A setup combining electromagnetic levitation with a horizontally directed DC magnetic field has been developed in the laboratory. Experiments performed with model materials (Cu, Ni, CuNi) demonstrated a strong stabilising effect of the DC magnetic field above 4.5 T on the oscillatory behaviour of levitated droplets. The intensity of the fluid flow visible over the surface of the droplet due to the transport of some oxide particles was also found decreased, however, the question remained about the intensity of the fluid flow inside the droplet. In addition, an unexpected and pronounced destabilisation of the levitated droplet was observed if the intensity of the DC magnetic field lied within 1.5–3 T. The physical origin of this phenomenon remains unclear. Finally, the response of the droplet to mechanical and thermal perturbations under weaker magnetic fields (below 1.5 T) has not yet been systematically investigated.

Objectives of the PhD project.

The objective of the PhD project is to pursue the experimental investigation of electromagnetic levitation coupled with DC magnetic fields, considering both horizontal and vertical direction of the latter.
The work will focus on:
• Amelioration of instrumentation and automatization of the existent setup aimed at better controlling of the temperature of the levitating sample and a speed of data acquisition
• Studying the effect of DC magnetic field of 1T on the oscillation of the droplet using images of the droplet registered with a high-speed camera
• Visualisation of the destabilised droplet with high-speed camera with identification of characteristic frequencies of oscillations aimed to understand the underlying physical mechanism
• Measurement of the thermal expansion of the samples stabilised due to the DC magnetic field
• Determining the condition under which convective heat transport can be sufficiently reduced to enable reliable measurements of selected thermophysical properties
• Developing and validating experimental procedures for the measurement of these properties under controlled thermal and electromagnetic conditions

The experimental studies performed by the PhD candidate will be supported by numerical modelling performed within the hosting team and by a partner team of ANR MultiMAGe.

Expected skills.

_Required_:
1 - Excellent understanding of the fundamental processes of mass and heat transfer: conduction, convection, radiation and solute transport (diffusion)
2 - A strong interest in experimental work
3 - Good level of English
_Considered an asset_:
1. Experience in conducting experimental work (experimental internship)
2. Basic understanding of magnetohydrodynamics
3. Knowledge of Python programming
4. Experience in signal and/or image processing
_Personal qualities_:
Independence, organisational skills, attention to detail, the ability to work as part of a team, and good communication and writing skills

Your Work Environment

SIMaP - Science and Engineering of Materials and Processes (https://simap.grenoble-inp.fr) - is a multidisciplinary laboratory with more than 200 participants from chemistry, physics, materials and fluid mechanics. It is one of the leading laboratories in physical metallurgy and thermodynamics, architectural materials, and materials for microelectronics, electronics and energy applications. SIMaP is a joint research unit administrated by CNRS, University of Grenoble Alpes and Grenoble INP.
The PhD student will work in a very dynamic team having the expertise with processing materials in solid and liquid states using external (magnetic, electric, …) fields.

The PhD thesis will be performed under the IMEP-2 doctoral school at the University of Grenoble Alpes, with a speciality of MEP – Fluid Mechanics, Energy, Process Engineering.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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