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: andreas.nowak@ptb.de 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?