Model for nanoparticle charging by diffusion, direct photoionization, and thermionization mechanisms

Jingkun Jiang, Myong Hwa Lee, Pratim Biswas

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


A nanoparticle charging model considering simultaneous diffusion, direct photoionization and thermionization charging was developed. The model included a balance expression for the positive and negative ions, and one for each charge level of the particles. Three comparable parameters: attachment coefficient, β±(v,q), photoelectric yield coefficient, α+(v,q), and thermionic yield coefficient, γ+(v,q), were identified that govern different charging mechanisms. By comparing these parameters, the importance of different mechanisms was explored. Analytical (closed-form) solutions under certain unipolar and bipolar conditions were proposed. Literature reported experimental data on a soft-X-ray based unipolar charger was used to verify this model and fair agreement was achieved. A numerical algorithm was developed to solve the governing equations for a soft-X-ray enhanced electrostatic precipitator (ESP) system. The role of soft-X-ray irradiation at improving nanoparticle average charge and enhancing the ESP capture efficiency was demonstrated. Experimental tests with this system were also conducted. Measured capture efficiency showed excellent agreement with theoretical results.

Original languageEnglish (US)
Pages (from-to)209-220
Number of pages12
JournalJournal of Electrostatics
Issue number4
StatePublished - Apr 2007
Externally publishedYes


  • Diffusion charging
  • Nanoparticle
  • Photoionization
  • Soft-X-ray
  • Thermionization

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biotechnology
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Electrical and Electronic Engineering


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