Corona-assisted flame synthesis of ultrafine titania particles

Abstract

Synthesis of ultrafine titania particles is investigated in a diffusion flame aerosol reactor in the presence of a gaseous electric discharge (corona) created by two needle electrodes. The corona wind flattens the flame and reduces the particle residence time at high temperatures, resulting in smaller primary particle sizes and lower level of crystallinity. Increasing the applied potential from 5 to 8 kV reduces the particle size from 50 to 25 nm and the rutile content from 20 to 8 wt %. Coronas provide a clean and simple technique that facilitates gas phase synthesis of nanosized materials with controlled size and crystallinity.

Independent Control of Metal Cluster and Ceramic Particle Characteristics During One-step Synthesis of Pt/TiO2

“…External electrical fields to the flame induce ionic winds that increase flame cooling and reduce product primary particles. 10,11 Quenching the entire flame through a critical flow nozzle can also rapidly reduce the flame temperature resulting in nonagglomerated particles and even titania suboxides. 12 Another possibility for controlled quench cooling is the direct radial injection of cold air from a quench ring into a vapor-fed flame at a given height.…”

Overview of Electric Field Applications in Energy and Process Engineering

“…In the studies presented in Refs. [53,54], it was found that the e-field generated by needles determined most significantly the product powder characteristics. This is obviously induced by significant modifications of the flame shape and generated turbulence.…”

“…Pratsinis and coworkers investigated different flame geometries with electric fields applied perpendicular to the flow direction (see, e.g., [53,54]). Corona discharge was generated using needle shaped or plate electrodes for charging the particles.…”

Control of nanoparticle size and agglomeration through electric-field-enhanced flame synthesis

“…Much of the recent work in electrically-assisted flame synthesis of particles has been done by Pratsinis et al (Vemury and Pratsinis 1995a;Vemury et al 1997;Morrison et al 1997;Kammler and Pratsinis 2000). Vemury and Pratsinis (1995a) produced ultrafine titania particles generated from a CH 4 /air/Ar jet diffusion flame using a corona discharge to charge the particles (for repulsion and dispersion) and to reduce residence time through ionic wind effects by flow mixing.…”

“…Vemury and Pratsinis (1995a) produced ultrafine titania particles generated from a CH 4 /air/Ar jet diffusion flame using a corona discharge to charge the particles (for repulsion and dispersion) and to reduce residence time through ionic wind effects by flow mixing. Increased electric potential reduced the particle size and the rutile content.…”