Equilibrium Charge Density Research Articles

Electrification analysis of a web or sheet moving between pinch rollers

Abstract A model is developed which provides a phenomenological understanding of the static electrification of a web or sheet by a pinch roller system through which it passes, in terms of the electrostatic characteristics of the separate regions comprising the system. The total pinch roller interaction is characterized by a matrix and vector which are derived from the characteristics of the component parts of the interaction. It is therefore possible to examine the effect on the electrostatic performance of the whole system caused by a change in one or more components. The mode of accumulation of electrostatic charge on a web subjected to many repeated passes through the pinch roller system is derived and reveals that a unique equilibrium charge density on each surface is approached regardless of the initial charge density configuration. However, the sequence of discrete charge density changes on each surface, by which the equilibrium charge configuration is approached, is a unique function of the initial charge density on each surface. The model should be useful in designing or improving pinch roller devices, i.e., in choosing roller materials and their physical configuration.

Intermolecular Potential Variation due to Intramolecular Rotation in Molecules

Abstract The changes in charge and polarization densities of ethane, methanol and formamide upon internal rotation is studied using SCF-HF calculations. For formamide the charge density changes with dihedral angle are seen in the rapidly varying molecular dipole moment, whereas these changes are only moderate in the methanol molecule. In ethane the quadrupole moment variation is about 15%. The barriers to rotation are found to be 3.47 kcal/mole for ethane, 0.84 kcal/mole for methanol and 14.94 kcal/mol for formamide. The total molecular polarizability, which is estimated using perturbation theory, is varying slowly with rotation angle, but the individual atomic components change rapidly for all three molecules investigated. The calculations indicate that solvent effects upon intramolecular configuration are reflected in variations of intermolecular interactions. These implications are discussed in connection with modelling internally flexible molecules for use in molecular dynamics and Monte Carlo simulations. Similarly, water-water interactions are affected by small vibrations which alter the equilibrium charge density and polarizability of the individual molecule.

Conformation of surface bound polyelectrolytes: I. Implications for cell electrophoresis

We present a self-consistent calculation for a layer of short-chain polyelectrolytes grafted to a planar interface. Individual self-avoiding chain configurations are generated on a tetrahedral lattice. By evaluating the complete ensemble of configurations in the presence of a self-consistent field we determine averages for the equilibrium layer height, segment and charge density profiles. These describe the response of the layer to changes in the surrounding medium, in particular to electrolyte concentration. This self-consistent model of a biological cell, which is known to have an extended layer of charge exterior to the membrane bilayer surface, is applied to the problem of cell electrophoretic mobility. We compare the electrophoretic mobility deduced from the application of this model with that for a constant profile of charge and segments and with the case of a constant segment profile with a plane of charge, usually assumed in the literature. We find that, within the region of concentrations studied here and with the chain lengths used, there is general agreement between the different descriptions.

An ab initio Hartree-Fock pseudopotential approach to the ground-state properties of Si

An ab initio Hartree-Fock (HF) pseudopotential approach to the ground-state properties of silicon is presented. The methods used is the plane-wave self-consistent band calculation in the HF approximation. Results for the equilibrium lattice constant, cohesive energy, bulk modulus, charge density and band structure are given. The correlation contribution neglected in the HF approximation is discussed.

Surface passivation of inversion layer m.i.s. solar cells

Inversion layer m.i.s. solar cells rely on the charge-inducing properties of antireflection (a.r.) coatings to achieve good device performance. It has previously been shown that these properties reduce with time due to build-up of an equilibrium charge density on the outside of the a.r. coating. Although devices can be designed to accommodate this, considerable relaxation in design constraints could be achieved if it were possible to develop techniques for preventing this effect. Results with a technique based on surfactants are described.

Thermonuclear ion-electron screening at all densities. I - Static solution

view Abstract Citations (88) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Thermonuclear ion-electron screening at all densities. I. Static solution. Mitler, H. E. Abstract A good two-fluid approximation to the equilibrium charge density surrounding a target nucleus in a plasma is obtained, and it is shown that the usual expression for the screening factor by which thermonuclear reactions are accelerated in the plasma over their vacuum values is valid only in the weak-screening regime. The standard treatments of this problem are briefly outlined, their inadequacies are indicated, and reasonable general expressions are derived for the equilibrium potential and charge density around the target nucleus. The resulting interaction energy is determined along with the action integral for the WKB approximation to penetrability. Reaction rates and screening factors are calculated, first analytically in the general case and then numerically for a two-carbon-atom reaction in a pure C-12 medium. The screening factor for resonant reactions is given, and inadequacies of the present treatment are discussed. The results are compared with those obtained by others for a carbon flash in a 0.8-solar-mass star, a late stage of carbon burning, and explosive carbon ignition in a supernova shock. Publication: The Astrophysical Journal Pub Date: March 1977 DOI: 10.1086/155071 Bibcode: 1977ApJ...212..513M Keywords: Coulomb Potential; Ionic Reactions; Plasma Density; Plasma Interactions; Thermonuclear Reactions; Two Fluid Models; Electron Energy; Plasma Control; Quantum Mechanics; Screening; Stellar Evolution; Wentzel-Kramer-Brillouin Method; Nuclear and High-Energy Physics full text sources ADS |

The electrification of polymers by metals

A mechanism is proposed for the transfer of charge from a metal to a polymer which leads to a natural explanation of the (previously unexplained) linear relationship between the charge density and the metal work-function. In the simplest case of a single non-sliding contact it is found that the charge density does not depend on the metal. But if the contact is repeated many times, or if the metal slides on the plastic, the final charge density varies linearly with the metal work-function. In a single (non-sliding) contact electrons are believed to tunnel from the metal into trapping levels a short distance from the interface; thermodynamic equilibrium is not achieved because the difference in electrostatic potential across this thin layer of charge is not sufficient to raise the energy of the trapping levels up to the Fermi energy of the metal. But repeated contacts (or sliding contacts) transfer charge to greater depths and make equilibrium possible. This hypothesis predicts an equilibrium charge density linearly dependent on the metal work-function.

A new method of measuring contact electrification characteristics of materials

In studying the electrification of materials, the equilibrium charge transfer is a useful and common basis for comparing materials and investigating the parameters involved in charge transfer. This value is often difficult to obtain, however, because of air breakdown, changes in the nature of materials during prolonged contact, etc. Some of these difficulties may be overcome by precharging one of the insulating samples to a known charge density before making a contact charge measurement. Experimental results show that the charge retained after contact is linearly related to the precharge. From this linear relation, the equilibrium charge density can be obtained.