heterogeneously nucleated particles as a reference ......calibration of cpc detection efficiencies:...

Heterogeneously nucleated particles as a reference calibration aerosol according to ISO 27891

Konstantina Vasilatou GAWG Particulate Workshop BIPM, April 15th 2015

Outline

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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)

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Results: Mobility size distributions of Au and Ag particles

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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

A B

C

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4 x105

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TEM images

Results: Mobility size distributions of Au and Ag particles

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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

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4 x105

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TEM images

Results: Mobility size distributions of Au and Ag particles

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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

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4 x105

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- 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

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