Ionic Current Density Mapping

In the following, we restrict ourselves to quasi two-dimensional current distributions invariant along the z direction, for simplicity [51], Under such conditions we have jz = 0 and dByjdz = dBx/dz = 0. The only finite current density components are then 

The problem now is to determine the derivatives dBz/dx and dBz/dy. This can be done by evaluating the local precession phase shifts caused by the currents, that is 

The porous medium under investigation must be filled with an electrically conducting liquid, that is, an electrolyte solution. The electric conductivity is given by the empirical Kohlrausch law [53] 

Another problem that should be considered carefully is the fact that the evaluated phase shift data set is discrete, so that conventional numerical derivation methods 

The spatial current distribution can be simulated by solving Laplace s equation with Neumann boundary conditions at the pore walls, 

---

Ionic current density maps can be recorded with the aid of the pulse sequence shown in Figure 2.9.2. The principle of the technique [48-52] is based on Maxwell s fourth equation for stationary electromagnetic fields,... 

Fig. 2.9.2 Radiofrequency, field gradient and current distributions requires a three-dimen-ionic current pulse sequences for two-dimen- sional imaging sequence [see Figure 2.9.1(a)] sional current density mapping. TE is the Hahn and multiple experiments with the orientation spin-echo time, Tc is the total application time of the sample relative to the magnetic field of ionic currents through the sample. The 180°- incremented until a full 360°-revolution is pulse combined with the z gradient is slice reached. The polarity of the current pulses...

In corrosion studies, ISEs have been used to map the local concentration of ions over corroding metals in the liquid phase with high resolution and selectivity. For example, H+-, Mg -, and Zn +-selective microelectrodes were nsed in combined applications of the scanning ISE technique (SIET, akin to potentiometric SECM) and of the SVET over corroding alloys. The SIET image showed the local ion activities, while the SVET mapped the local ionic current density. In all cases, their ISE tips were made from single barreled micropipettes with cocktail of ionophores. 

Figure 1.1 Simple equivalent circuit (top) for modeling solar cell current-voltage characteristics and energy level diagram (bottom) mapping the various charge transfer processes in a DSSC to the current pathways of the model circuit. The dominant mechanisms are described by a current density Jl induced upon photoexcitation and electron injection into the conduction band of the metal oxide semiconductor surface MO, linear (Jsh) and nonlinear (/jj) reverse current densities in parallel with photocurrent source and a series resistance to account for electrode and ionic resistances. In Section 1.2.2 M0 = Ti02, Sn02, X = Br, I.

---