AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThP

Paper PS-ThP1
3D Numerical Modeling and Experimental Characterization of Internal Antenna Type Inductively Coupled Plasma System for Nitriding of Bipolar Plates for PEMFC(Polymer Electrolyte Membrane Fuel Cell)

Thursday, November 12, 2009, 6:00 pm, Room Hall 3

Session: Plasma Science Poster Session
Presenter: J. Joo, Kunsan National University, Republic of Korea
Authors: J. Joo, Kunsan National University, Republic of Korea
W. Yang, Kunsan National University, Republic of Korea
J. Lee, Seoul National University, Republic of Korea
Correspondent: Click to Email
Bipolar plates for PEMFC(polymer electrolyte membrane fuel cell) are crucial in determining service life of hydrogen fuel cells. The required anti-corrosion characteristics is very hard to meet with commercial materials, e.g. 316 stainless steels while keeping other requirements, e.g. electrical conductivity, mechanical formability and cost. Thin film coatings could be substitute solution but fairly marginal due to its relatively high cost. Second option is surface nitriding using high density plasma sources with appropriate substrate bias. Plasma nitriding at high temperature upto 800°C is a stable technology for automobile parts and tools. Stainless steels do not allow to go over 500°C due to its microstructural phase transformation. Low temperature, high rate nitriding technology is very crucial technique in this field. Bipolar plate is in a thin sheet form of 300 x 300 mm as thin as 0.5 mm. We used internal antenna type inductively coupled plasma as a source of nitriding species. The mixing ratio of nitrogen and hydrogen was varied to give optimal plasma generation condition. Plasma diagnostic techniques, e.g. Langmuir probe measurement, optical emission spectroscopy, and biasing voltage/current waveform measurements were used to characterize the process. For optimal design of industry scale systems, we used a 3D computational fluid dynamic code (CFD-ACE+). Number of antenna turns, relative positions of antenna and loaded sheets, gas pressure and composition were varied and diagnosed experimentally. In addition, substrate biasing schemes were studied. Final anti-corrosion characteristics showed that pulsed dc bias of 50 kHz with 600 W of ICP was giving best corrosion current density among others; 316 stainless steel, Cr, CrN with dc bias.