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Spray Pyrolysis

Spray Pyrolysis. chemical synthesis of nanostructures. Scott Allen Physics Department University of Guelph. fundamentals – some language. atomization – is the production of droplets and their dispersion into the gas. [Okuyama et al, Chem. Eng. Sci., 2003].

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Spray Pyrolysis

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  1. Spray Pyrolysis chemical synthesis of nanostructures Scott Allen Physics Department University of Guelph

  2. fundamentals – some language atomization – is the production of droplets and their dispersion into the gas. [Okuyama et al, Chem. Eng. Sci., 2003] aerosol – defined as a suspension of solid or liquid particles in a gas. [Okuyama et al, Chem. Eng. Sci., 2003] “Spray pyrolysis is the aerosol process that atomizes a solution and heats the droplets to produce solid particles.” [Che et al, J. Aero. Sci., 1998] Messing et al, J. Am. Ceram. Soc., 1993

  3. fundamentals – the process there are a number of different atomizers Messing et al, J. Am. Ceram. Soc., 1993 atomization variables: droplet size – relates to the size of the end particle size dispersion – homogeneity of end products atomization rate – scalability of process is affected (i.e. industrial processes) droplet velocity – affects residence time within the furnaces

  4. fundamentals – droplet evolution Messing et al, J. Am. Ceram. Soc., 1993 evaporation – evaporation of solvent from the surface, diffusion of solvent vapour away from droplet, change in droplet temperature, diffusion of solute toward the center of the droplet, change in droplet size precipitation/drying – involves volume precipitation or surface precipitation of the solute, followed by the evaporation of the solvent through the nanoporous crust thermal decomposition or pyrolysis – forms a nanoporous structure sintering – involves the adhesion/solidification of the crystallites

  5. fundamentals – precipitation control Messing et al, J. Am. Ceram. Soc., 1993 Che et al, J. Aer. Sci., 1998 precipitation behaviour can be controlled by the solubilities of the starting materials or by introducing a precipitation reaction into the droplet

  6. fundamentals – creating nano particles requires dilute solutions and small initial droplet sizes conventional spray pyrolysis can produce particles that have multiple nanosized crystallites, but these crystallites are virtually inseparable due to the formation of a three-dimensional network. [Xia et al, Adv. Mater., 2001]

  7. fundamentals – salt-assisted spray pyrolysis method depends on the distribution of salt on the nanocrystallite surfaces to prevent them from agglomerating [Xia et al, Adv. Mater., 2001]

  8. benefits/limitations – does not require high quality targets or substrates – does not require a UHV system [Patil, Mater. Chem. Phys., 1999] – continuously produces the material One of the unique characteristics of spray pyrolysis is that the chemical reaction occurs within the created micron to sub-micron sized liquid droplets – a microcapsule reactor. [Che et al, J. Aero. Sci., 1998] technique is quite empirical, with a number of variables that can affect the final product – solute concentration – atomization technique – temperature, temperature gradient – residence time in furnace – carrier gases

  9. OOO

  10. OOO electrospray pyrolysis Lenggoro et al, J. Aer. Sci., 2000 ZnS particles were generated in a size ranging from 20 to 30 nm.

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