Tailoring atomic structure and mechanical behavior of complex concentrated alloy thin films by oxygen incorporation

Organisation/Company

LSPM , CNRS 3407

Research Field

Engineering » Materials engineering
Physics » Solid state physics
Engineering » Mechanical engineering

Researcher Profile

First Stage Researcher (R1)

Country

France

Application Deadline

3 Oct 2024 – 00:00 (Europe/Paris)

Type of Contract

Temporary

Job Status

Full-time

Hours Per Week

38

Offer Starting Date

1 Oct 2024

Is the job funded through the EU Research Framework Programme?

Not funded by an EU programme

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

PhD thesis position

Tailoring atomic structure and mechanical behavior of complex concentrated alloy thin films by oxygen incorporation

Supervisors : Dr. Matteo Ghidelli (@LSPM), Dr. J. Nelayah and Prof. Christian Ricolleau (Uni. Paris Cité)

Desired Starting date : 01/10/2024

Keywords: thin films; complex compositional alloys; magnetron sputtering; pulsed laser deposition; Oxygen addition; HRTEM;  in-situ SEM mechanical properties.

A fully funded 3 years PhD project is available between the Laboratoire des Sciences des Procédés et des Matériaux (LSPM/USPN) and the Laboratoire Matériaux et Phénomènes Quantiques (MPQ/UPCité).

Short description of the thesis project

Complex concentrated alloys, also referred as High Entropy Alloys (HEAs), are a new class of equiatomic multicomponent metallic materials exhibiting remarkable mechanical properties[1] . Recently, it has been shown that introducing oxygen (O) in bulk refractory HEAs significantly enhances mutually exclusive mechanical properties, such as strength and ductility, reaching, respectively, 1.2 GPa (48.5 % increase) and >30% (95% increase) when adding 2.0 % at. O to TiZrHfNb HEA[2] .

Furthermore, the current trend toward device miniaturization within key sectors such as microelectronics (MEMS, NEMS), energy, devices fabrication as well as in the development of high-performance films lead to the development of Thin Film HEAs (TF-HEAs), reporting even boosted combination of mechanical properties. For example, micro-pillar compression tests carried out on BCC NbMoTaW TF-HEAs have shown outstanding yield strength of 10 GPa and 30% elastic-plastic deformation which are among the highest values reported in the literature for metallic materials[3] .

However, the synthesis and characterization of TF-HEAs are still in their infancy and open questions dealing with a systematic investigation of O addition, leading to controlled/boosted mechanical behavior, are still to be uncovered. Such difficulty arises by the complex interplay of structure, composition and atomic heterogeneities (generated by O addition) and the need of scale-bridging characterization methods, ranging from the atomic to the micrometer scale capable to grasp the evolution of structure and mechanical properties. In addition, key elements involving the film growth regime of TF-HEAs with O addition, investigating the transition from nanoparticles (NPs, 0D) to continuous films (2D) are still to be uncovered.

In this context, this PhD project will focus on the deposition of CoCuNi and Fex CoCuNi TF-HEAs focusing on O addition (form 0 up to 15% at.), while avoiding the use of rare earth elements often present in refractory counterparts. This represents a novel class of TF-HEAs with the potential to widely explore the effect of composition. This approach benefits of the ease of synthesis of complex compositions, which can be easily tailored by changing the deposition parameters, while systematically investigate the effect of O addition.

The alloys will be deposited by magnetron sputtering (LSPM) and pulsed laser deposition (PLD, MPQ), with tunable O content. Specifically, we aim to exploit the potential of PLD to investigate the initial film growth regimes, namely the formation of multicomponent (0D) NPs with different size, potential out-of-equilibrium atomic arrangements and to compare it with conventional sputter deposition, which will be used to produce thicker (2D) films of the same composition.

The structural characterization will involve standard SEM/EDX, XRD as well as advanced HRTEM imaging and spectroscopy techniques (MPQ) to investigate the effect of the oxygen-induced local heterogeneities as well as to identify key atomic structural features responsible of the mechanical behavior. In parallel, the mechanical characterization will focus on nanoindentation, optoacoustic techniques as well as on cutting-edge in situ SEM mechanical testing (i.e. micropillar compression test, LSPM), enabling direct observation of the deformation mechanisms at the microscale, while providing key properties such elastic-plastic deformation and yield strength.

Overall, the results of the PhD will pave the way to understanding fundamental questions involving the early stage growth of TF-HEAs with O addition and how this affect local structure and the micro-mechanical behavior. This will open new scenarios for the design of structural coatings with boosted mechanical properties with large interest for a variety of applications in the field of high performance coatings and microelectronics.

Your tasks:

• Synthesis of TF-HEAs and nanoparticles by magnetron sputtering (LSPM) and PLD (MPQ) with controlled O addition.
• Standard and advanced structural HRTEM characterization (MPQ/LSPM).
• Investigation of mechanical properties with in situ SEM techniques (nanoindentation, micropillar compression…) (LSPM).
• Unveiling the interplay among atomic structure↔O addition↔mechanical properties, leading to a new class of materials with potential applications (LSPM/MPQ).

The offer:

• Multidisciplinary project covering physics, materials science, mechanics, and nanotechnologies.
• Development of cutting-edge experimental tools for the synthesis of TF-HEAs with O incorporation and advanced scale-bridging characterizations.
• Multicultural and dynamic laboratory environment within two labs in Paris. High mobility and competitive salary.
• National and International collaboration network with different institutions in France and Europe.

Your Profile:

• Master’s degree in physics or materials science or similar disciplines.
• For students without a master, a master (M2) internship can also offered with graduation expected before October 2024 followed by the enrollment in the PhD program.

Further information & application:

For further information and application please send your CV and your exam scores (Bachelor and Master) to Dr. Matteo Ghidelli ([email protected] ), Prof. Christian Ricolleau ([email protected] ) and Dr. Jaysen Nelayah ([email protected] ).

References:

[1] D.B. Miracle, O.N. Senkov, A critical review of high entropy alloys and related concepts, Acta Mater. 122 (2017) 448-511.

[2] Z. Lei, et al., Enhanced strength and ductility in a high-entropy alloy via ordered oxygen complexes, Nature 563(7732) (2018) 546-550.

[3] Y. Zou, H. Ma, R. Spolenak, Ultrastrong ductile and stable high-entropy alloys at small scales, Nature communications 6(1) (2015) 1-8.

Requirements

Research Field

Engineering » Materials engineering

Education Level

Master Degree or equivalent

Research Field

Physics

Education Level

Master Degree or equivalent

Research Field

Engineering

Education Level

Master Degree or equivalent

Skills/Qualifications

• Master’s degree in physics or materials science or similar disciplines.
• For students without a master, a master (M2) internship can also offered with graduation expected before October 2024 followed by the enrollment in the PhD program.

Languages

ENGLISH

Level

Good

Research Field

Engineering » Materials engineering

Years of Research Experience

None

Additional Information

Website for additional job details

https://www.linkedin.com/in/matteo-ghidelli-5932b64b/

Work Location(s)

Number of offers available

1

Company/Institute

Centre national de la recherche scientifique (CNRS)

Country

France

City

Paris

Geofield

Where to apply

E-mail

[email protected]

Contact

State/Province

Ille de France

City

Villetaneuse

Website

http://www.lspm.cnrs.fr/?lang=fr

Street

99 Avenue JB Clement,

Postal Code

93430

STATUS: EXPIRED