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WAter
in TEM
ANR project n°ANR-20-CE42-0008 (36 months, 2020-2023) |
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Contact: Thierry EPICIER, thierry.epicier@ircelyon.univ-lyon1.fr (updated 2024/04/05) |
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Predicting both climate
and temperature evolution
requires, among other parameters, to quantify properly the contribution
of
clouds through a better understanding of their formation. Clouds form
by
condensation of water vapor on particles (aerosols) of varying
morphology and
chemical composition and with sizes down to a sub-micron level. WATEM will
study the early stages of this process in situ in a Transmission
Electron
Microscope (TEM). Providing the required spatial resolution, the TEM
also
brings morphological (2D/3D), structural and chemical information. The
challenge to control thermodynamic conditions for condensation of
liquid
droplets from a humid gaseous environment will be taken up in a
dedicated
Environmental TEM (ETEM) working at a variable partial pressure (<
20 mbar
as in ESEM: Environmental Scanning EM). Titan ETEM 80-300 kV (FEI/TFS) installed
at IRCELYON, Univ. Lyon 1 (CLYM
instrument) |
ESEM Quattro (FEI/TFS)
installed at MATEIS, INSA-Lyon (
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We will develop a tip for
a sample holder based on a
Peltier cooled micro-device allowing observing solid, liquid and vapor
phases
at the same time, and evolution at their interfaces, as well as pure
liquid
without sealing membranes. Based on this
technological development, WATEM will
highlight the scientific expertise of three teams whose expertise are
both complementary
and with sufficient overlap so that effective communication and
exchanges can
take place together with effective intra- and inter-team work thus
providing a
solid basis for the success of the project: IRCELYON (atmospheric
chemistry, liquid/gas ETEM, liquid/gas ESEM), MATEIS
(liquid/gas ETEM, liquid/gas ESEM,
electronic tomography, specific sample holders) , MAJULAB (micro/nano
devices, specific sample holders,
ESEM/ETEM). WATEM will
revolve around 5 scientific/technological
WP (in addition to the WP concerning the project management). WP1
concerns the
realization of the Peltier cooled micro-device adaptable both to an
ESEM and to
an existing sample holder in an ETEM. This original solution will be
completed
by other existing alternatives a priori
less effective from the point of view of fine control of the
temperature, and
therefore of the conditions of condensation of water on the aerosols.
These
alternatives allow nevertheless to manageable the risk of delay in the
development of our prototype. In WP3, WP4 and WP5 particular attention
will be
given to the effects of irradiation so as to minimize their effect on
the observed
phenomena and to develop relevant experiment protocols. WP3 will
validate and
calibrate the Peltier micro-device in the ESEM by studying the water
condensation on large collections of model artificial aerosols
(statistical
studies) thus taking advantage of the space existing in the ESEM
chamber and in
order to facilitate the experiments to be carried out in the ETEM;
tomography
approaches in ESEM, under condensation conditions, will also be tested.
A
similar approach in ETEM will be performed in WP4, taking advantage of
the
results acquired in WP3: validation of the Peltier micro-device in ETEM
on the
same model aerosols and measurements of the deliquescence (DRH) and
efflorescence (ERH) relative humidity. We will also study the role of
the mixed
nature of aerosols (for instance: inorganic/organic) on hygroscopicity
using
analytical methods (EDX/EELS), complementary to imaging, as well as
electronic
tomography. Finally, in WP5 we will tackle the study of natural
aerosols
(atmospheric sampling) in ETEM; here the main challenge will be to be
able to
follow in real-time the evolution of the solid/liquid and liquid/vapor
interfaces
essential for an understanding of the growth phenomena of water
nanodroplets
and their implication in cloud formation.
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