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Optimization of silver particle number
size distributions from a homogenous
nucleation furnace
Andreas Nowak, Johannes Rosahl, Detlef Bergmann
Arne Kuntze, Margit Hildebrandt, Egbert Buhr, Volker Ebert
WG 3.23: Aerosol and Particle Diagnostics
19th ETH-Conference on Combustion Generated Nanoparticles 30.06.2015
Needs for EECPC calibration
Criteria of calibration aerosol
Nucleation furnaces
Results
EECPC calibration needs
02.07.2015 2
Manufacture independent EECPC calibration
Preferably with traceable calibration chain
Primary and secondary PN standard
A suitable aerosol EECPC calibration
Comparable to engine exhaust
Metrological Uncertainties
Previous work@PTB: EMRP-project, ENV02, PartEmission,
2011-2014)
Goals: Determination and Validation of primary and
secondary method for PN
Development of suitable calibration aerosol/setup
ENV02-Project Results
02.07.2015 3
Aerosol criteria:
highly monodisperse
single charge
spherical morphology
tunable diameter size between 10 to 100 nm
sufficient particle number concentration, up to 105 cm-³
highly thermal stability, up to 350 °C
Criteria according to ISO 27891
Promising aerosol candidate: silver nanoparticles
Homogenous nucleation process
Nucleation furnace: History
02.07.2015 4
simple tube furnace to generate silver particles (Scheibel and Porstendörfer*)
Findings:
condensation dominates nucleation process in colder part of furnace
particles < 50 nm with high concentration (107), size down to 2 nm
monomodal size distributions with narrow distributions (σ~1.3-2.0)
particles above 30 nm: have tendency to be non-spherical particle
only one heating zone (max. 1300°C)
short high temperature region
short residence time
*Journal of Aerosol Science, Volume 14, Issue 2, Pages 113-126 (1983)
Nucleation furnace: Optimization at PTB
02.07.2015 5
Goals:
larger particles increase of residence time larger furnace with 3 heating zones
optimization flow scheme and T gradient implementation of heating shields:
inlet shield with nozzle (different sizes)
outlet shield with hoper
minimization of conglomerates water cooling flange at end of tube shock cooling
water cooling flange
PNSD measurements: Experimental setup
02.07.2015 6
Sinterfurnace
NitrogenExhaust
Nucleation furnace
Nitrogendilution
UCPCUDMARack
optional
Carrier flow: 0.8 – 2.0 l/min (N2)
Dilution flow: 0.8 – 2.0 l/min (N2)
UDMA (hauke short) flow: 1.5 : 15 l/min
Scan range: 3 – 93 nm, stepwise
UCPC (TSI 3776) at high flow mode
1:1
Tests for different flow ratios and configurations
PNSD results I: Flow effects
02.07.2015 7
Constant nozzle (1mm) and same silver loading at one temperature
0.0E+00
2.0E+04
4.0E+04
6.0E+04
8.0E+04
1.0E+05
1.2E+05
1.4E+05
1.6E+05
1 10 100
raw
PN
C [
cm-3
]
mobility diameter [nm]
1.0 l/min
1.6 l/min
2.0 l/min 1200°C
Increasing PNC with higher flows Indication for an optimal flow scheme
monomodal size distribution @ 1.6 l/min
No correction factors for PNSD
flow
PNSD results II: Different shield configurations
02.07.2015 8
Constant nozzle (1mm) at one temperature and one flow ratio for carrier and dilution flow (1:1)
0.0E+00
5.0E+04
1.0E+05
1.5E+05
2.0E+05
2.5E+05
3.0E+05
3.5E+05
4.0E+05
4.5E+05
1 10 100
raw
PN
C [
cm-3
]
mobility diameter [nm]
w/o heat shield
both heat shields
1 mm nozzle
1 mm nozzle sintered
1200°C
w/o heat shield less PNC
Both heat shields smaller silver particles, sharp peak in lower size range
Only inlet heat shield with nozzle higher PNC
Sintering up to 650 °C no influence for PNSD
For further studies only inlet heating shield with different nozzle sizes
PNSD results: Nozzle sizes
02.07.2015 9
For different nozzle sizes at one flow ratio (1:1) from 960 °C up to 1300 °C
High PNC (> 105 cm-3) above 15 nm
2 mm nozzle: mean mobility diameter up to 65 nm, but broad size distribution
2 mm nozzle well suited for further experiments
1
1.5
2
2.5
3
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
0 10 20 30 40 50 60 70
Sigm
a o
f P
NSD
max
. pe
ak h
eig
ht
of
PN
SD [
cm-3
]
mean mobility diameter [nm]
3 mm nozzle | 1:1
2.5 mm nozzle | 1:1
2 mm nozzle | 1:1
1 mm nozzle | 1:1
Fit parameter of PNSD
Results IV: Particle Shape
02.07.2015 10
STEM pictures for different types of tube furnaces
Ag-particles@41 nm Ag-particles@23 nm
Old furnace construction comparable to
Scheibel and Porstendörfer
New tube furnace at PTB
Without sintering mostly spherical particles
Conclusion
02.07.2015 11
Optimization of tube furnace and homogenous nucleation through heath
shields, different nozzles and flow control
larger particle sizes and suitable PNC for Ag-NP
Only spherical particle were generated
Without required sintering for Ag-NP
For ISO 27891
Entire particle size range
Sufficient PNC
Outlook
02.07.2015 12
Further increasing of size range to larger sizes above 100 nm
Heterogeneous silver nucleation with two furnaces
Minimizing charge correction factors above 60 nm
2nd UDMPS with unipolar charging
Increasing of PNC for monodisperse fraction
Communicate results (ENV02) into the legislative community (PMP/ISO)
Establish EECPC calibration service at PTB in 2016
Physikalisch-Technische Bundesanstalt
Braunschweig and Berlin
Bundesallee 100
38116 Braunschweig
Dr. Andreas Nowak
Email: [email protected] www.ptb.de
soot particles Ag particles
k [m-1]
Type approval of opacimeter Test reports for opacimeter
N [cm-3]
Test reports for particle counter
calibration service in 2016
m[µg/m3]
Test reports for
light scattering devices
automotive emission
Dp [nm]
Comparison to TSEM and AFM
Metric of WG 3.23
Thank you very much for your attention!
Questions?