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Heterogeneously nucleated particles as a reference calibration aerosol according to ISO 27891
Konstantina Vasilatou GAWG Particulate Workshop BIPM, April 15th 2015
Outline
04.05.2015 METAS 2
A. Towards a reference calibration aerosol: Heterogeneous nuclea- tion of silver (Ag) vapours on gold (Au) seed particles • Motivation • Experimental setup • Particle size distributions of gold (Au) and silver (Ag) particles • Factors that influence the growth of silver particles
B. Characterisation of a Palas UF-CPC
• Calibration with respect to a Faraday-Cup Aerosol Electrometer
Desired properties of reference aerosol
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Calibration of differential mobility analyzers (DMAs): • monodisperse aerosol • spherical particles • known particle size
Calibration of CPC detection efficiencies: • additionally, singly charged calibration aerosol. Spherical particles: mobility diameter corresponds to the geometric diameter of the particle.
Experimental setup
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Au-seed-particle generation Ag-particle
growth Monitoring/ Characterisation
GFG 1000
Furnace
AFM/TEM CPC
CPC
SMPS
Exhaust
Exhaust
DMA
T1=1210°C Evaporation of Ag T2= 730°C Shaping T3= 390°C Growth
T1 T2 T3
S. Zihlmann, F. Lüönd and J.K. Spiegel, Journal of Aerosol Science 75, 81 (2014)
}
Results: Mobility size distributions of Au and Ag particles
04.05.2015 METAS 5
S. Zihlmann, F. Lüönd and J.K. Spiegel, Journal of Aerosol Science 75, 81 (2014)
pristine Au70 seeds sintered Au70 seeds
A B
C
++
4 x105
++
TEM images
Results: Mobility size distributions of Au and Ag particles
04.05.2015 METAS 6
S. Zihlmann, F. Lüönd and J.K. Spiegel, Journal of Aerosol Science 75, 81 (2014)
pristine Au70 seeds sintered Au70 seeds final Ag particles
A B
C
++ ++
4 x105
++
TEM images
Results: Mobility size distributions of Au and Ag particles
04.05.2015 METAS 7
S. Zihlmann, F. Lüönd and J.K. Spiegel, Journal of Aerosol Science 75, 81 (2014)
pristine Au70 seeds sintered Au70 seeds final Ag particles
A B
C
++ ++
4 x105
++
- Au particle size reduces to approx. half due to sintering - Mobility distributions exhibit slight tail at larger mobility diameters - Additional peak present corresponding to doubly charged particles - To generate singly charged aerosol, the transfer function of DMA must be carefully chosen
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Factors influencing the growth of Ag particles
Size of Au seed Size of Ag particles particles (non-linear dependence)
S. Zihlmann, F. Lüönd and J.K. Spiegel, Journal of Aerosol Science 75, 81 (2014)
sintered Au at 500°C final Ag particles
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Factors influencing the growth of Ag particles
Size of Au seed Size of Ag particles particles (non-linear dependence)
Concentration − Size of Ag of Au seed particles particles
Flow of N2 − Size of Ag particles Sphericity
S. Zihlmann, F. Lüönd and J.K. Spiegel, Journal of Aerosol Science 75, 81 (2014)
sintered Au at 500°C final Ag particles
Conclusions
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Novel and simple method to generate Ag nanoparticles - which are spherical
- have a narrow size distribution (advantage over homogeneous nucleation)
- with a tunable size (through T1 of the furnace and size of seed particles)
- with diameters with a diameter that can exceed 100 nm
BUT
- The transfer function of second DMA must be carefully chosen to minimise the presence of doubly charged particles
- The growth mechanism should be further investigated to test whether it is exclusively heterogeneous nucleation or if coalescence plays also a role
Caracterisation of Palas UF-CPC
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M. Miranda, K. Auderset and K. Vasilatou, work in progress
Thermodenuder 300°C
Exhaust FCAE
Exhaust
85Kr SiO2
Exhaust
Particle-free air
Dilution unit
Advantages of UF-CPC: UF-CPC 200 (single-particle counting):
• CNmax=106 P/cm3
• Accuracy: 5%
• Working fluid: BuOH, i-PrOH, H2O, decane a.o.
• Tsat and Tcond can be changed
MFM Flow splitter
DMA
TSI 3775 CPC Palas
UF-CPC
miniCAST
Detection efficiency as a function of particle number concentration
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Number concentration (P/cm3)
104.8±0.7
78.6±0.7
104.9±0.9
80.5±0.2
103.8±0.8
91.9±0.2
110
100
90
80
% E
ffici
ency
Palas UF-CPC TSI 3775 CPC
0 50000 100000 150000 200000 250000 300000
dP = 80 nm
Detection efficiency as a function of particle number concentration
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Number concentration (P/cm3)
104.8±0.7
78.6±0.7
104.9±0.9
80.5±0.2
103.8±0.8
91.9±0.2
110
100
90
80
% E
ffici
ency
Palas UF-CPC TSI 3775 CPC
0 50000 100000 150000 200000 250000 300000
dP = 80 nm
Nominal flow rate: 0.5 lpm Measured flow rate 8% higher
Detection efficiency as a function of particle number concentration
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Number concentration (P/cm3)
104.8±0.7
78.6±0.7
104.9±0.9
80.5±0.2
103.8±0.8
91.9±0.2
110
100
90
80
% E
ffici
ency
Palas UF-CPC TSI 3775 CPC
0 50000 100000 150000 200000 250000 300000
UF-CPC at low concentrations very poor signal-to-noise ratio
dP = 80 nm
Nominal flow rate: 0.5 lpm Measured flow rate 8% higher
Detection efficiency as a function of particle number concentration
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Number concentration (P/cm3)
104.8±0.7
78.6±0.7
104.9±0.9
80.5±0.2
103.8±0.8
91.9±0.2
110
100
90
80
% E
ffici
ency
Palas UF-CPC TSI 3775 CPC
0 50000 100000 150000 200000 250000 300000
UF-CPC modified by Palas to operate also at a flow of 1.0 lpm
dP = 80 nm
Nominal flow rate: 0.5 lpm Measured flow rate 8% higher
Detection efficiency as a function of particle number concentration
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Number concentration (P/cm3)
104.8±0.7
78.6±0.7
104.9±0.9
80.5±0.2
103.8±0.8
91.9±0.2
110
100
90
80
% E
ffici
ency
Palas UF-CPC TSI 3775 CPC
0 50000 100000 150000 200000 250000 300000
We are ready to start testing isopropanol and other condensation fluids
dP = 80 nm
Thank you very much for your attention
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S. Zihlmann, F. Lüönd and J.K. Spiegel, Journal of Aerosol Science 75, 81 (2014)
pristine Au70 seeds sintered Au70 seeds final Ag particles
A B
C
++ ++
0
Results: Mobility diameter as a function of furnace temperature T1
4 x105
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