Diffusion battery theory

Cheng, Y.S. and H.C. Yeh, Theory of Screen Type Diffusion Battery,... 

For a poiydisperse aerosol, the number of particles deposited up to any point in the system can be calculated from the theory for monodisperse aerosols and then integrating over the initial. size distribution, which is the quantity sought- The experimental measure ments made with the condensation nuclei counter gives the number concentration of the poiydisperse aerosol as a function of the distance from the inlet to the diffusion battery. The recovery of the size distribution function from the measured decay In particle concentration can be accomplished in an approximate way. Various numerical schemes based on plausible approximations have been developed to accomplish the inversion (Cheng, 1993). The lower detection limit for the diffusion battery is 2 to 5 nm. Systems are not difficult to build for specific applications or can be purchased commercially. 

The theory of diffusion through the screens in diffusion batteries, as described by a semi-empirical equation derived by Cheng and Yeh (1980) correlating the screen fractional efficiency with experimental parameters, does not strongly differ from that formulated by Thomas and Hinchliffe (1972) as the penetration of particles through the screen (or the screen collection efficiency) is also an exponential function of the above parameters. 

Porous-electrode theory has been used to describe a variety of electrochemical devices including fuel cells, batteries, separation devices, and electrochemical capacitors. In many of these systems, the electrode contains a single solid phase and a single fluid phase. Newman and Tiedemann reviewed the behavior of these flooded porous electrodes [23]. Many fuel-cell electrodes, however, contain more than one fluid phase, which introduces additional complications. Typical fuel cell catalyst layers, for example, contain both an electrolytic phase and a gas phase in addition to the solid electronically conducting phase. An earher review of gas-diffusion electrodes for fuel cells is provided by Bockris and Srinivasan [24]. 

Recently, however, the type of diffusion unit with a porous wall has been abandoned by Hertz and his collaborators (5i), and instead batteries of diffusion pumps are joined together directly, separation occurring by effusion together with mercury vapour through jets. The theory of the separation of... 

Electronically conducting polymers have recently been considered as electrode materials for various electrochemical devices, primarily batteries and electronic displays. However, in the case of the polymers yet studied, e.g. polyacetylene and polypyrrole, little regard has been paid to the ionic conductivity which, according to ambipolar diffusion theory, is required for mass transport of the electroactive species from the surface to the bulk of the electrode. In fact, experiments on polyacetylene in conjunction with solid polymer electrolytes have indicated that the charge-discharge rate will be limited by the ionic conductivity. 

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