Electric field discharge

Fillers and additives may also interact with the solvent, with the polymer, or with both. The electrospinnability of tbe solution may change as a result of these interactions, but it may also remain imcbanged, regardless of tbe additive. It has, for example, been shown that conductive solutions can form different kinds of three-dimensional loose structures on the substrate, instead of a tbin coating layer attached to the substrate surface. Tbe form of these structures can vary from fibrils perpendicular to the substrate surface to a layer with a fluffy cotton-like structure. Fibrils can even extend to cover tbe entire electrospinning zone. If this kind of conductive fibrous structure connects tbe nozzle and collector plate, the electric field discharges and the process stops. The optimisation of the process parameters for ternary systems can be even more challenging than for binary systems composed only of polymer and solvent. 

The inductively coupled plasma [19] is excited by an electric field which is generated by an RF current in an inductor. The changing magnetic field of this inductor induces an electric field in which tire plasma electrons are accelerated. The helicon discharge [20] is a special type of inductively coupled RF discharge. 

Electric-Field Gradients across the Glow Discharge... 

In Figure 6.4, the two electrodes are marked as cathode and anode, arising from the application of an external voltage between them. Before any discharge occurs, the electric-field gradient between the electrodes is uniform and is simply the applied voltage divided by the their separation distance, as shown in Figure 6.7. 

Particularly in mass spectrometry, where discharges are used to enhance or produce ions from sample materials, mostly coronas, plasmas, and arcs are used. The gas pressure is normally atmospheric, and the electrodes are arranged to give nonuniform electric fields. Usually, coronas and plasmas are struck between electrodes that are not of similar shapes, complicating any description of the discharge because the resulting electric-field gradients are not uniform between the electrodes. 

The various stages of this process depend critically on the type of gas, its pressure, and the configuration of the electrodes. (Their distance apart and their shapes control the size and shape of the applied electric field.) By controlling the various parameters, the discharge can be made to operate as a corona, a plasma, or an arc at atmospheric pressure. All three discharges can be used as ion sources in mass spectrometry. 

The multiple energetic collisions cause molecules to break apart, eventually to form only atoms, both charged and neutral. Insertion of sample molecules into a plasma discharge, which has an applied high-frequency electric field, causes the molecules to be rapidly broken down into electronically excited ions for all of the original component atoms. 

When corona occurs, current starts to flow in the secondary circuit and some dust particles are precipitated. As potential is increased, current flow and electric field strength increase until, with increasing potential, a spark jumps the gap between the discharge wire and the collecting surface. If this "sparkover" is permitted to occur excessively, destmction of the precipitator s internal parts can result. Precipitator efficiency increases with increase in potential and current flow the maximum efficiency is achieved at a potential just short of heavy sparking. 

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