Synthetic nanoparticles produced using flame spray pyrolysis

Transcription

1 Synthetic nanoparticles produced using flame spray pyrolysis FlameDays 2012 T. Karhunen, A. Hukkanen, T. Kaivosoja, J. Leskinen, A. Lähde, O. Sippula, J. Tissari, J. Jokiniemi Fine Particle and Aerosol Technology Laboratory, University of Eastern Finland, Kuopio, Finland

2 Overview of the set-up Dispersion of the precursor Pyrolysis of the droplets Particle growth and quenching Sampling and analysis Figure: FSP schematic

3 Dispersion of the precursor Figure: Droplet size distribution at 1 bar Precursor solution Central capillary Flow rate: syringe pump Dispersion gas Annular aperture Flow rate: mass flow controller Pressure drop: adjustable aperture size

4 Pyrolysis of the droplets Figure: Temperature of HMDSO/ethanol flame Ignited by H 2 /O 2 flamelets Droplets evaporate Organic compounds combust Temperatures in excess of 2500 K Sub-millisecond residence time Formation of oxide products

5 Particle growth and quenching Figure: TEM images showing agglomeration Oxides crystallize and coagulate Sintering forms primaries and aggreagates Strong radiative cooling sintering terminated Primary size: nm Aggregate size: 100 nm Loose agglomeration up to 1 µm

6 Operation Figure: Flame spray pyrolysis in progress Precursor concentration Droplet size Combustion temperature Oxygen ratio Mixing Sintering temperature Dilution ratio

7 Outline 1 2

8 Background Figure: Li 4 Ti 5 O 12 crystal structure with Li + diffusion paths Li 4 Ti 5 O 12 (LTO) is a promising negative electrode material for next generation Li-ion batteries Inexpensive and readily available Improved environmental and operational safety Increased cycle-life However, it is an insulator poor rate performance

9 Primary particle size Kavan et al. (2003) found that reducing the primary particle size improves rate performance Rate performance imroves with increasing specific surface area ( dp 1 ) Optimal specific surface area 100 m 2 /g (primary size 17 nm) Figure: Effect of primary size on rate performance

10 Aerosol measurements Figure: Total particulate concentration measured with CPC Figure: Agglomerate size distribution measured with FMPS

11 X-ray fluorescence Table: Elemental fractions Element Fraction (%) Ti 52 F 0.3 Si 0.15 Na 0.07 Cl 0.04 Al 0.02 Ca 0.02 Zn 0.02 Li 4 Ti 5 O Figure: FSP prepared Li 4 Ti 5 O 12 powder

12 X-ray diffration Figure: XRD diffractiogram of Li 4 Ti 5 O 12 prepared with FSP at different sintering temperature

13 High-resolution TEM Figure: HRTEM image of Li4 Ti5 O12 agglomerate (left) and primary particles (right)

14 Outline 1 2

15 Background Particulate emissions of biomass combustion containg a multitude of compounds Need to isolate different compounds to understand the source of the adverse health effects Synthesise pure combustion particles using FSP Precursors: K, K+S, K+S+Zn, Zn

16 TEM Figure: TEM image of synthetic combustion particles Excess of sulphur was required Resulted in the formation of sulphuric acid Very low concentration in cell culture

17 XRD Figure: X-ray diffractiograms of synthetic combustion particles Main compounds found K precursor: potassion carbonate K+S precursor: potassium sulphate Zn precursor: zinc oxide K+S+Zn precursor: potassium sulphate and zinc oxide

18 Chemistry Figure: Chemical composition of synthetic combustion particles XRD analysis supported by chemical analysis Some inpurities present Mainly sulphuric acid Toxicology on-going

19 Thank you. Akcnowledgements This work was supported in part by the Finnish Funding Agency for Technology and Innovation (TEKES) and by the Fortum Foundation.