(220a) Flame Spray Synthesis of Bi2O3 Nanoparticles From Low Enthalpy Precursors

A new flame assisted
spray pyrolysis (FASP) reactor design is presented, which allows manipulating
the enthalpy content of the flame independently of the precursor solution
chemistry. In this reactor design, a gas-assisted atomizer generates the
precursor solution/oxygen spray. The spray is mixed and combusted with
externally-fed acetylene or premixed methane/oxygen fuel gases at a defined
height above the atomizing nozzle. The gaseous fuel feed can be varied to
control the enthalpy content of the flame, where particle formation takes
place. This way, the enthalpy density of the flame is decoupled from the
precursor solution composition.

Precursor solution
compositions with low internal energy contents were shown to be prone for
production of inhomogeneous product particles of a bimodal size distribution in
the related flame spray pyrolysis (FSP) process. For example precursor
compositions of various metal nitrates in ethanol were shown to produce
inhomogeneous products consisting of nanosized particles from gas-to-particle
conversion along with a fraction of large particles from droplet-to-particle
conversion. A typical route to avoid this product inhomogeneity in FSP is to
increase the flame enthalpy by the precursor chemistry, resulting in more
complex and costly precursors. The FASP design facilitates the use of the low
enthalpy precursor solutions for the production of homogeneous product powders
by increasing the enthalpy density of the flame with low cost gaseous fuels.

 The effect of the
flame enthalpy density on product properties in FASP configuration is explored
on the example of Bi₂O₃ nanoparticles produced from
bismuth-nitrate in ethanol precursor solution.  Product
powders were characterized by nitrogen adsorption, X-ray diffraction, X-ray
Disc centrifuge and transmission electron microscopy. Homogeneous product
powders from Bi-nitrate precursor in ethanol were produced by the new FASP
design.