Annual-Report-2019

MODELING OF REACTIVE PLASMAS FOR
NANOPARTICLE SYNTHESIS
Materials & Energy Sciences 2019
22
Prof. Igor Denysenko
LE STUDIUM Research Professor
Smart Loire Valley General Programme
From: V. N. Karazin Kharkiv National
University - UA
In residence at: Research Group in the
Energetics of Ionized Media (GREMI) - Orléans
Nationality: Ukrainian
Dates: May 2019 to July 2019
Prof. Igor Denysenko is working on lowtemperature
plasma physics and dusty plasma
physics and chemistry since more than 25 years
and is an expert of their theoretical and numerical
modeling. His recent studies concern the growth
of nanoparticles in low-pressure plasmas and
its effect on the plasmas. He is particularly
well-known for his works related to effects of
nanoparticles on electron energy distribution in
complex plasmas and for the studies of effects
of plasma on growth of vertically-aligned carbon
nanostructures. In 2003, Prof. Denysenko was
awarded by a research fellowship of the Alexander
von Humboldt Foundation (Germany). He was
project leader of a few international projects
(Humboldt Foundation projects and a NATO
Collaborative Linkage Grant) and many Ukrainian
projects. He is co-author of 63 papers, 2 chapters
of books, 2 textbooks and many proceedings. He
was co-chairman of two international workshops.
Dr Maxime Mikikian
Host scientist
Dr Maxime Mikikian is working on dusty plasma
physics and chemistry since more than 20 years
and is an expert of their experimental investigation.
The background of his recent studies concerns the
growth of nanoparticles in low-pressure plasmas
and its effect on the plasma. He is particularly wellknown
for his work related to nanoparticle formation
and dynamics and for his discovery of original dusty
plasma instabilities. Co-responsible of the topic
Functional Materials by Plasmas and Lasers in
GREMI, he was also the coordinator of the national
network on low-temperature plasmas in 2015-
2016 («Réseau Plasmas Froids»). Co-author of 45
papers and about 60 proceedings, he gave 9 invited
lectures and 14 talks at international conferences.
He coordinated 6 national or international research
projects, and also participated in the organization
of 13 national and international conferences and
workshops.
The goals of the project are the development of theories and numerical
programs to describe physical and chemical processes in reactive (mixtures
of argon with acetylene, ethanol or aniline) steady-state and pulsed
plasmas, and on walls, substrates and surfaces exposed to these plasmas.
These theories and programs are required for analyses of the experimental
data of partner-researches from GREMI and for determination of optimal
conditions for the production of nanostructures with desired properties.
The activity is carried out to get materials with new advanced properties for
different applications and is also of fundamental interest for different fields.
During his first visit to France in May-July 2019, Igor Denysenko in
collaboration with the project partners developed a theoretical model
and a numerical program for description of properties (densities of ions,
electrons, neutrals and atoms in different excited states, radical and ion
fluxes to plasma walls, effective electron temperature and nanoparticle
charge) of Ar/C 2
H 2
complex nonstationary plasma. The pulsed regime and
the plasma with growing nanoparticles were considered. The models for
Ar/C 2
H 2
complex plasma account for various processes of production and
loss of main species in the plasma in different binary collisional processes,
as well as for their loss due to diffusion to the walls and collisions with
nanoparticles. Analyzing effects of external conditions on the densities of
species taking part in the nanoparticle nucleation (negative and positive
hydrocarbon ions and hydrocarbon radicals), it was found that Ar/C 2
H 2
plasmas with low electron density, moderate input flux of acetylene and an
electron energy distribution function (EEDF) close to the Druyvesteyn EEDF
are the most suitable for the production of carbonaceous nanoparticles.
The time-dependent properties of an Ar/C 2
H 2
dusty plasma were studied
for conditions corresponding to experiments on nanoparticle growth of
partner-researches from GREMI. The calculated density evolution for C 2
H 2
,
H 2
and C 4
H 2
molecules were compared with time-resolved measurement of
the mass peaks of the neutral species and the effects of the dust density on
the plasma properties were analyzed. Time evolutions of the main positive
and negative ions were also obtained thanks to the calculations.
As a consistency check the time-dependence of the dust radius was also
obtained numerically, assuming that an increase of the dust radius was due
to deposition of hydrocarbon ions and C 2
H radicals on the surface of dust
particles. It was shown that for conditions corresponding to the experiment,
the ions are the main contributor to the particle growth. The calculated dust
growth rate was compared to the time-dependence of the dust particle size
obtained in the experimental measurements. The results of the numerical
calculations were found to be in a good qualitative agreement with the
experimental data. The work on development of a spatially-averaged model
for argon-ethanol plasma was also started this year.