à 
(QC) Canada

Lien Zoom: https://umontreal.zoom.us/j/93026432919
Meeting ID: 930 2643 2919
Passcode: écrire en chiffre: un, trois, sept.

First presentation:

Tailoring the magnetocaloric effect in oxides
Mohammad Abbasi Eskandari
Département de physique
Univresité de Sherbrooke

Présentation en anglais

Abstract: Magnetic cooling systems based on magnetocaloric effect (MCE) have been considered as an alternative solution to the actual gas compression technology in terms of their higher energy efficiency and being environmentally friendly [1]. In the case of domestic magnetic refrigeration, one needs to have a magnetic material with a near room temperature magnetic transition and a significant magnetic entropy change over a wide temperature range covering roughly the 20° C to -20° C. For some magnetocaloric refrigeration cycles, a so-called table-top temperature dependence of the entropy change would be a great asset and several routes to achieve it have been explored. Among the many oxide families which show significant magnetocaloric effect close to room temperature, manganites of general formula R1-xAxMnO3 have received enormous attention due to their advantages such as small thermal and magnetic hysteresis, high chemical stability and tunable transition temperature. Similarly, double perovskites of general formula A2BB’O6 have also attracted interest [2]. Their main advantage over R1-xAxMnO3 is their high resistivity. As many other oxides, the magnetic properties of manganites and double perovskites can be tuned in using doping with different elements or changing the growth conditions [3] allowing to shift their transition temperature, but also manipulating the width of their transition in the hope of achieving table-top entropy change. As another approach, one can tune material properties by combining different systems in a composite structure. In this case people usually combine materials with different transition temperatures to get magnetic entropy change over a wide temperature range.

In this work, we used pulsed laser deposition (PLD) technique to growth bilayer and trilayer composites of two different oxides La2NiMnO6 (LNMO) and La2/3Sr1/3MnO3 (LSMO) on LSAT substrates. In bilayer samples we were able to affect the ratio of the cation ordering in LNMO layer by changing the arrangement of the layers. We get a cation-ordered LNMO layer with a magnetic phase transition at 230 K when it is deposited on a bare substrate. However, it shows a lower magnetic phase transition temperature at 180 K when it is grown on top a LSMO. This behavior driven by strains can be used in trilayer samples where three magnetic transition can be detected, which enables us to get a fairly flat and roughly temperature-independent table-top magnetic entropy change over a temperature range as large as 100 K. These results suggest a route through composites to tune the magnitude, shape and width of the temperature dependence of the magnetic entropy change. This technique allows us to tailor an appropriate material for magnetic refrigeration at room temperature by changing the arrangement of layers.

[1] M. Balli, S. Jandl, P. Fournier, and A. Kedous-Lebouc, 'Advanced materials for magnetic cooling: Fundamentals and practical aspects,' Applied Physics Reviews, vol. 4, no. 2, p. 021305, 2017.
[2] K.-I. Kobayashi, T. Kimura, H. Sawada, K. Terakura, and Y. Tokura, 'Room-temperature magnetoresistance in an oxide material with an ordered double-perovskite structure,' Nature, vol. 395, no. 6703, p. 677, 1998.
[3] D. Matte, M. de Lafontaine, A. Ouellet, M. Balli, and P. Fournier, 'Tailoring the Magnetocaloric Effect in La 2 NiMnO 6 Thin Films,' Physical Review Applied, vol. 9, no. 5, p. 054042, 2018.

Second presentation:

Three Decades of Innovative and Engineered Green Chemistry: from Papermaking to Neurodegenerative Disease
Roger Gaudreault
Département de physique
Université de Montréal

Présentation en anglais

Abstract: Dr. Gaudreault’s will cover more than 30 years of his contribution to Green Chemistry research and process development. The focus of his work has been in the Pulp and Paper Industry (P&P), industrial water treatment, renewable energy and more recently neurodegenerative disease.

At the conference, you will learn about innovative paper and packaging products, totally chlorine-free bleaching processes, corrosion inhibition, biofuel from biomass, kinetics of aggregation and neurodegenerative disease (e.g. Alzheimer).

Bio: Roger Gaudreault, Baccalauréat en chimie UQAC (1986),
MSc en pâtes et papiers de UQTR (1991),
Doctorat en simulation moléculaire de l’Université McGill (2003),
PostDoc sur la chimie des colloïdes à Harvard (2005-2006).
Prix et distinctions :
Depuis 2017, chercheur invité à l'Université de Montréal, il étudie l'impact de la chimie verte sur l'atténuation de la maladie d’Alzheimer et du coronavirus COVID-19.
Mr Gaudreault s'est vu décerné le Prix canadien de la chimie verte et de l'ingénierie en 2016 (CGCEN), également « PAPTAC Fellow » en 2017 en reconnaissance de sa contribution exceptionnelle à long terme et significative à l'industrie des P&P.

For more information about Dr Goudreault, you can consult his research web page.

Cette conférence est présentée par le RQMP.

RQMP séminaire du lundi: Mohammad Abbasi Eska (UdeS) et Roger Gaudreault (UdeM)