33°° InternationalInternational ConferenceConference ononFrontiersFrontiers of Plasma of Plasma PhysicsPhysics and and TechnologyTechnology
Trends Trends in plasma in plasma applicationsapplications
R. BarniR. BarniCentro PlasmaPrometeoCentro PlasmaPrometeo
BangkokBangkok5 5 MarchMarch 20072007
TrendsTrends towardstowards atmosphericatmospheric pressurepressure::
Plasma processing Plasma processing
•• MostMost industrialindustrial processesprocesses are are performedperformed in open air or at in open air or at atmosphericatmospheric pressurepressure..•• ManyMany materialsmaterials do do notnot likelike toto bebe exposedexposed toto vacuumvacuum. . •• ProcessesProcesses are are integratedintegrated in a in a chainchain withwith anan almostalmost continuos continuos feedingfeeding of the of the materialsmaterials toto bebe treatedtreated..
So So atmosphericatmospheric plasma are more plasma are more compatible compatible withwith existingexisting industrialindustrial processesprocesses
Moreover:• processes are faster (higher density of neutral radicals, if not ions) • easily scalable to large areas • processing region is well confined
On On earthearth: : lightninglightning, , thunderbolt thunderbolt ((stormsstorms, , volcanovolcano eruptionseruptions) )
AtmosphericAtmospheric pressurepressure plasmas plasmas in naturein nature
MankindMankind activityactivity::ElectricalElectrical dischargesdischarges
B.Franklin (1747)B.Franklin (1747)
ApplicationsApplications: plasma : plasma torchtorchwastewaste, , coatingscoatings, cutting, cutting
AtmosphericAtmospheric pressurepressure plasmas plasmas in in laboratorylaboratory
ArcArc dischargedischarge::thermalthermal plasmaplasma
(T(Tgasgas~T~Tee~5~5--10000 K)10000 K)
Corona Corona dischargedischarge::coldcold diffuse plasmadiffuse plasma
micromicro--dischargesdischarges::intermittentintermittent plasmaplasma
((streamersstreamers))
Corona treatment: Corona treatment: AdhesionAdhesion, , paintingpainting
Laboratory Laboratory and and experimentalexperimental setupsetup
ControlledControlled gasgas--phasephaseDBD DBD reactorreactor
EvacuatedEvacuated chamber chamber
SurfaceSurface DiagnosticsDiagnostics::AFM, FIB/SEM , FTAFM, FIB/SEM , FT--IRIR
Plasma Plasma sources sources and and diagnosticsdiagnostics
PlasmaPrometeoPlasmaPrometeo Center (2004)Center (2004)
Diagnostics Diagnostics
ElectricalElectricalcharacteristicscharacteristics::
VoltageVoltage acrossacross the gap:the gap:HV HV probesprobes, , largelarge bandwidthbandwidth
(PS(PS--6015A, 75 6015A, 75 MHzMHz))
microdischargemicrodischarge currentcurrentLargeLarge bandwidthbandwidth, , high high sensitivitysensitivity
((homehome--mademade RogoskiRogoski coilscoils))
0 10 20 30 40 50 60-8-6-4-202468
-400
-200
0
200
400-8-6-4-202468
24 26 28 30 32
0
100
200
300
Vo
ltage
[KV]
Time [µs]
Cur
rent
[mA]
Time [µs]
Volta
ge [K
V]
Cur
rent
[mA]
DiagnosticsDiagnostics
200 300 400 500 600 700 8000
100
200
300
400
500
Inte
nsità
(a.u
.)
Lunghezza d'onda (nm)
Atmospheric pressure DBD Low pressure Glow discharge
OpticalOptical tecniquestecniques: :
EmissionEmission spectraspectraradicalradical identificationidentification
AdvancedAdvanced toolstoolsLIF, LIF, StarkStark, fast , fast camerascameras
100 120 140 160 180 2000.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
2800
2900
3000
3100
3200
3300
Intensity ratio O (777.4) / N2 (357)In
tens
ity ra
tio
Power (W)
Vibrational temperature (K)
Oxygen
ModelingModeling
dt
dn=k
n n K - n n K kiji,
jkijiji,
kji ⋅⋅ ∑∑ →+→+ ik)w(ii
i 2i
k2k nB)S1(
D n
D - →⋅−⋅
Λ+⋅
Λ∑
Chemical reactor model• cylindrical channel (Rs, L) • radial diffusion • longitudinal uniform (n, T) • slow flowrate -> mixing along
the channel (well-mixed reactor)
Density balance equations• 22 species (10 neutral, 12 ions)• 194 reactions rates• 15 wall recombination processes
Chemical kineticsof the gas-phase
in a microdischarge
ModelingModeling
1E-10 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1104105106107108109
10101011101210131014101510161017101810191020
Chemical Composition of an Air streamer
Den
sity
(cm
^-3)
Time (s)
N N2 O O2 O3 NO N2O NO2
ChemicalChemical kineticskinetics of of a a sparkspark dischargedischarge in in
ArAr/CH4 /CH4
ChemicalChemical kineticskinetics of of a a dbddbd in airin air
((streamerstreamer regime)regime)
Streamer development
Repetition rate ν = 2 νAC
0 5 10 15 200.0
0.2
0.4
0.6
0.8
1.0
H2 p
artia
l pre
ssur
e (1
0-6 m
bar)
/ Hα li
ne in
tens
ity (a
.u.)
Mean spark current (mA)
P (H2) I (H
α)
0.0
0.1
0.2
0.3
H2 conversion efficiency (percentage)
ApplicationsApplications::
SilkSilk:: technologytechnology goalgoal removeremove sericinsericin
ProcessProcess:: selectiveselective removalremoval pure pure fibroinfibroin fibres fibres
Plasma:Plasma: etchingetching OO22 removeremove/crack /crack sericinsericin
Untreated Plasma treated Chemical degumming
ApplicationsApplications::
LeathersLeathers:: technologytechnology goalgoal obtainobtain printabilityprintability
ProcessProcess:: modifymodify wettabilitywettability dyedye fixedfixed on on surfacesurface
Plasma:Plasma: dbddbd in air/in air/helium helium --OH,OH,--COOH COOH graftinggrafting
Untreated Plasma treated Photographic film
ApplicationsApplications::
500 600 700 800 900 10000.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
untreated
treated
Ref
lect
ivity
(%)
wavelength (nm)
energy dose 105.4 J cm-2
untreated sample
PET PET filmsfilms:: technologytechnology goalgoal opticaloptical propertiesproperties
ProcessProcess:: modifymodify roughnessroughness reflectivityreflectivity changeschanges
Plasma:Plasma: dbddbd in air in air surfacesurface etchingetching
Untreated Plasma treated
ApplicationsApplications::
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20
1
2
3
4
5
6
pure methane
total flow Γ=20 l/min
Per
cent
age
(%)
O/C ratio
CO CO2 H2 |∆O2|
EnergyEnergy:: technologytechnology goalgoal hydrogenhydrogen productionproduction
ProcessProcess:: fuelfuel reformerreformer HH22 richrich mixturesmixtures
Plasma:Plasma: sparkspark in CHin CH44/air /air HH22 productionproduction
0 100 200 300 400 5000
1
2
3
4
5
6
O/C ratio 1.2
Per
cent
age
(%)
discharge current (mA)
CO CO2 H2 |∆O2| |∆CH4|
ApplicationsApplications::
PaperPaper:: technologytechnology goalgoal improveimprove packagingpackaging
ProcessProcess:: modifymodify wettabilitywettability hydrorepellncyhydrorepellncy
Plasma:Plasma: NN22/HMDSO /HMDSO dbd dbd siloxanesiloxane filmfilm
Untreated Plasma treated e 1 e 2 e 3 e 4 e 5
0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
2 0 0
2 5 0
3 0 0
g/m
2
U n t re a te d s u r fa c e L o w p re s s u re p la s m a a tm o s p h e r ic p re s s u re p la s m a
W a te r A b s o rp t io n [C o b b 6 0 ]
ApplicationsApplications::
FIB FIB section section and and imagingimaging
FTFT--IR IR spectra spectra of HMDSO film on PETof HMDSO film on PET
(Si(Si--OO--Si, SiSi, Si--CH3, CH3, CHxCHx)) Estimated thickness: 120 nm
4000 3500 3000 2500 2000 1500 1000 500 00
20
40
60
80
100
Tran
smitt
ance
(%)
Wavenumber k (cm-1)
ConclusionsConclusions
Plasma processing: Plasma processing:
ContributionContribution fromfrom basic plasma basic plasma physicsphysics researchresearch::
• is a dry and eco-friendly technology (deserve spreading)• atmospheric pressure discharges widen application field of plasmas• processes should be brought at atmospheric pressure
(polymerization, pattern, nanopowder)
• development of advanced diagnostics(electrical, optical)
• modeling of the discharge processes(breakdown, sustainement, regimes, chemistry)