Contamination of Ultrapure Systems by Back-Diffusion of Gaseous Impurities

Nishith K. Verma, Asad M. Haidel, Farhang Shadman

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Diffusion of impurities against the direction of gas flow can be a significant source of contamination in the ultrapure gas systems. The mechanism and the kinetics of impurity transport due to back-diffusion is studied both experimentally and theoretically. A model is developed to simulate the process and calculate the extent of impurity transport due to back-diffusion. Experiments for measuring oxygen back-diffusion in a nitrogen carrier stream are conducted. The data and the model predictions are in good agreement. Back-diffusion involves both bulk and surface diffusion and is higher for lower pressures, lower flow rates, larger tube diameters, and for smaller nonadsorbing molecules.

Original languageEnglish (US)
Pages (from-to)1459-1463
Number of pages5
JournalJournal of the Electrochemical Society
Issue number5
StatePublished - May 1993

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry


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