Dual ion beam-assisted deposition

Saha et al. [109] have proposed an improved ion deposition methodology based on a dual ion-beam assisted deposition (dual IBAD) method. Dual IBAD combines physical vapor deposition (PVD) with ion-beam bombardment. The unique feature of dual IBAD is that the ion bombardment can impart substantial energy to the coating and coating/substrate interface, which could be employed to control film properties such as uniformity, density, and morphology. Using the dual lABD method, an ultralow, pure Ft-based catalyst layer (0.04-0.12 mg Ft/cm ) can be prepared on the surface of a GDL substrate, with film thicknesses in the range of 250-750 A. The main drawback is that the fuel cell performance of such a CL is much lower than that of conventional ink-based catalyst layers. Further improvement... 

Saha, M. S., Gullb, A. R, Allen, R.J., and Mukerjee, S. High-performance polymer electrolyte fuel cells with ultralow Pt loading electrodes prepared by dual ion-beam assisted deposition. Electrochimica Acta 2006 51 4680-4692. 

Gulla et al. reported several thin-layer electrodes with superior performance and stability. Using a dual-ion beam-assisted deposition technique, they coated a Pt outer layer ( 50 nm thick, 0.08 mg Pt/cm ) directly onto GDLs with either a Co or Cr inner layer ( 50 nm thick). These bilayered electrodes showed a mass-specific Pt activity more than 50% higher at 900 mV than that for a single Pt layer on GDLs. No ionomers were present in the electrodes. 

Gulla et al. have demonstrated superior performance and stabUily of carbonless thin layer electrodes made by a dual ion beam assisted deposition (IBAD) technique that combines physical vapor deposition (PVD) with ion beam bombardment [47]. They found that bilayered coatings on GDL with either a Co or a Cr iimer layer ( 50 nm thin) and a Pt outer layer ( 50 nm thin, and 0.08 mg Pt cm ) showed a more than 50% higher Pt mass activity at 900 mV than a Pt single layer. 

Dual ion beam-assisted deposition is a method based on physical vapor deposition (PVD). A plasma of ions to be deposited is generated by bombardment of a target with low-energy ions. The ions are then extracted from the plasma and accelerated to be included into the PVD layer growing on the substrate. 

Research activity in this field has been quite important and is continuing. Thus, the effect of alloys deposited on a support by chemical vapor deposition (Seo et al., 2006b) and by dual ion-beam-assisted deposition (IBAD Gulla et al., 2006) has been studied. Another advantage of such platinum-alloy catalysts that was noted by many workers is their reduced sensitivity to methanol crossing over to the oxygen electrode in DMFCs and the associated improvement in the stability of the electrode s potential (Yuan et al., 2006 Baglio et al., 2007). 

Sadhir, R.K Schoch, K.F. (1996). Plasma-Polymerized Carbon Disulfide Thin-Film Rechargeable Batteries. Chem. Mater., Vol. 8, pp. 1281-1286 Saha, M.S. Gulla, A.F. Allen, R.J. Mukerjee, S. (2006). High Performance Polymer Electrolyte Fuel Cells with Ultra-Low Pt Loading Electrodes Prepared by Dual Ion-Beam Assisted Deposition. Electrochim. Acta, Vol. 51, pp. 4680-4692 Schieda, M. Roualdes, S. Durand, J. Martinent, A. Marsacq, D. (2006). Plasma-Polymerized Thin Films as New Membranes for Miniature Solid Alkaline Fuel Cells. Desalination, Vol. 199, pp. 286-288... 

There are two forms of ion-beam-assisted deposition (IBAD). The first is a dual-ion-beam system in which one source is used to sputter a target to provide a source of atoms for deposition (the same process we described in Section 28.10). Simultaneously a second ion beam is aimed at the substrate and bombards the depositing film. In the second configuration, shown in Figure 28.7, an ion source is combined with an evaporation source. 

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