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)