Charged solids

Charge solids materials by means of a closed system (e.g., hopper and rotary airlock, screw feeder, double-dump valve system, etc.)... 

Trace contaminants are also significant at charged solid surfaces, affecting both the charging process and the surface conductivity. In ambient air atmospheres their effect is often determined by interaction with adsorbed water vapor, whose dominant concentration may be sufficiently large to form a monolayer. Topical antistatic agents for solids typically rely on interaction with adsorbed water and can lose effectiveness at low relative humidity (4-2.1). 

Figure 6.27. Charge density contours for the adsorption of Cl, Si, and Li on jellium. (a) Total charge and (b) induced charge solid lines indicate an increase in electron density, dashed...

Figure 2.4 Sketch of an electric double layer next to a negatively charged solid surface. Through balance of thermal motion and electrostatic forces a rapidly decaying electric potential IFdevelops inside the liquid phase.

Figure 38. Calculated j-U curves for dielectric with negative space charge (solid curves) and reference uncharged one (dashed curve). The insets illustrate curve linearization in log j- U and log j-Ul/2 coordinates.62...

Figure 7. Specific capacity during the first charge (solid symbol) and discharge of modified carbon-type materials.

Figure 3. Vertical cross-section showing equipotential contours inside a conductive cylindrical silo containing a symmetric conical heap of uniformly charged solids. The electrostatic potential maximum exists on the center line somewhat below the powder surface, while the maximum electric field intensity occurs near the wall just above the powder.

Charging solids with a nongrounded and conductive chute can result in a buildup of a charge on the chute. This charge can accumulate and finally produce a spark that may ignite a dispersed and flammable dust. 

With the thermospray interface (Figure 4.38(a)), the mobile phase, usually containing an ammonium ethanoate buffer, is passed through a heated probe (350-400°C) into an evacuated source chamber where it forms a supersonically expanding mist of electrically charged droplets. The liquid evaporates to leave charged solid particles which then release molecular ions such as MH+ and, VI by an ammonia chemical ionization (Cl) process. The analyte ions are skimmed off into the mass spectrometer whilst the vaporized solvent is pumped away. An electron beam is also employed to enhance the production of ions by Cl. 

Zhulina, E. B., Borisov, O. V., van Male, J. and Leermakers, F. A. M. (2001). Adsorption of tethered polyelectrolytes onto oppositely charged solid-liquid interfaces, Langmuir, 17, 1277-1293. 

Cation exchange The displacement of one cation for another on the surface of a negatively charged solid, such as a clay mineral. 

Negative adsorption occurs when a charged solid surface faces an ion in an aqueous suspension and the ion is repelled from the surface by Coulomb forces. The Coulomb repulsion produces a region in the aqueous solution that is depleted of the anion and an equivalent region far from the surface that is relatively enriched. Sposito (1984) characterized this macroscopic phenomenon through the definition of the relative surface excess of an anion in a suspension, by... 

Similarly, charged solid particles (such as latex spheres) —kinetically stable lyophobic colloids —may exist in colloidal crystalline phases (with body-centered or face-centered cubic structures) as a consequence of thermodynamically favored reduction in free energies (see Chapter 13). Even neutrally charged spherical particles ( hard spheres ) undergo a phase transition from a liquidlike isotropic structure to face-centered cubic crystalline structures due to entropic reasons. In this sense, the stability or instability is of thermodynamic origin. 

In this section we deal with liquids, which flow along charged solid surfaces. In many cases the surface binds one, two, or several layers of liquid molecules and possibly ions more or less tightly. As a result the shear plane is often not directly at the interface. Only at a distance 6 away from the surface do the molecules start to move. The potential at this distance is called the zeta potential . 

Calculate the thickness of the diffuse electric double layer for a negatively charged solid surface in contact with the following... 

The volume balance of the charged solid and of the fixed charges can be integrated analytically leading to [4]... 

Example 3.2 Consider a large number of uniformly charged solid particles initially kept in a spherical barrier of radius R with a symmetric density distribution. When the barrier is suddenly removed, the particles start to emerge from that spherical domain. The viscous drag in the gas is assumed to be negligible. Find the ratio of the force due to dipole to that due to electrostatic repulsion and show that for dilute suspensions, the dipole effect due to self-field is negligible. Also discuss the spreading of the solid particles in this simple symmetric system. 

Usually, there is fast exchange of the looked-at cations between several sites, typically the bulk solvent (water, most often) and the anionic head-group of the surfactant, or of a charged solid surface (for a 2 1 phyllosilicate) If the quadrupo-... 

Statistic mechanics were used by Kiefer and Wilson104 to calculate adsorption isotherms of ionic surfactants on charged solid-water interface. The effect of coulombic repulsions between the ionic heads of the surfactant species are considered, as well as the van der Waals attractions of their hydrocarbon tails. Using the method of Fowler and Guggenheim93 they obtained the equation for an adsorption isotherm ... 

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