Ion penetration

When an energetic ion penetrates a soHd, it undergoes a series of coUisions with the atoms and electrons in the target. In these coUisions the incident particle loses energy at a rate of a few to 100 eV pet nanometer, depending on the energy and mass of the ion as well as on the substrate material. 

Fig. 6. An incident ion penetrates with a total path length R, which gives a projected range, R, along the direction parallel to that of the incident ion (1).

A schematic of the production of acid and base by electrodialytic water dissociation is shown in Fig. 22-61. The bipolar membrane is inserted in the ED stack as shown. Salt is fed into the center compartment, and base and acid are produced in the adjacent compartments. The bipolar membrane is placed so that the cations are paired with OH" ions and the anions are paired with H. Neither salt ion penetrates the bipolar membrane. As is true with conventional elec trodialysis, many cehs may be stacked between the anode and the cathode. 

On the other hand, pit initiation which is the necessary precursor to propagation, is less well understood but is probably far more dependent on metallurgical structure. A detailed discussion of pit initiation is beyond the scope of this section. The two most widely accepted models are, however, as follows. Heine, etal. suggest that pit initiation on aluminium alloys occurs when chloride ions penetrate the passive oxide film by diffusion via lattice defects. McBee and Kruger indicate that this mechanism may also be applicable to pit initiation on iron. On the other hand, Evans has suggested that a pit initiates at a point on the surface where the rate of metal dissolution is momentarily high, with the result that more aggressive anions... 

Relatively high values of the experimental capacity Q have led Samec et al. [16] to propose that ions can penetrate into the irmer layer over some distance. The effect of the ion penetration was taken into account by solving the linearized Poisson-Boltzmann (PB) equation in all three regions of the MVN model with the result [17],... 

Particular cases are potassium selective potentiometric sensors based on cobalt [41] and nickel [38, 42] hexacyanoferrates. As mentioned, these hexacyanoferrates possess quite satisfactory redox activity with sodium as counter-cation [18]. According to the two possible mechanisms of such redox activity (either sodium ions penetrate the lattice or charge compensation occurs due to entrapment of anions) there is no thermodynamic background for selectivity of these sensors. In these cases electroactive films seem to operate as smart materials similar to conductive polymers in electronic noses. 

In the ionic implantation, a beam of trivalent ions (e.g. B+ ions), is used to produce a p+ layer. Pentavalent ions (e.g. P ions), instead, create an n+ layer. The main advantage of this technique rely in the fact that the ions penetrate the crystal only for a short distance from the surface ( 200nm). The penetration depth depends on the beam energy (25 100keV). Typical doping level is 1018 1019ions/cm3. With such a high dopant concentration, the layer becomes practically a metal. 

Energy Increasing the energy of the primary ions initially increases the sputter yield. At high energy, however, ions penetrate deeper into the solid and dissipate their energy further away from the surface. The result is that fewer collision cas-... 

The intensity of a peak in RBS is determined by the cross section o for scattering. At MeV energies, the helium ion penetrates deeply into the atom and approaches the nucleus of the target atom to within 10 4 nm, i.e. well within the radius of the K-electron shell. This means that the scattering event depends only on the Coulomb repulsion between the two nuclei, whereas screening by the electrons (which is important in LETS) plays no role. Thus the scattering cross section is a... 

Supposing that the water layer is a small reservoir of 100 water molecules, and that the external pH is 0, then the hydronium ions penetrate that reservoir until equilibrium is reached and a nominal PH = 0 is also obtained in the layer s volume. From the point of view of the protein, this means that the protein gets protonated by only two protons ( pH = 0 means 2 moles H30+ for each 100 moles water)... 

One synthesis approach that does not rely on CNT formation from the gas phase is molten salt synthesis. The reactor consists of a vertically oriented quartz tube that contains two graphite electrodes (i.e. anode is also the crucible) and is filled with ionic salts (e.g. LiCl or LiBr). An external furnace keeps the temperature at around 600 °C, which leads to the melting of the salt. Upon applying an electric field the ions penetrate and exfoliate the graphite cathode, producing graphene-type sheets that wrap up into CNTs on the cathode surface. Subsequently, the reactor is allowed to cool down, washed with water, and nanocarbon materials are extracted with toluene [83]. This process typically yields 20-30 % MWCNTs of low purity. 

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