Electrical Discharge Treatment Research Articles

Electric discharge treatment of the surface of bentonite clay containing montmorillonite

The electrification of solid porous adsorbents of the clay type was studied. It was found by the thermally stimulated relaxation method that clays contained centers of the accumulation of surface and volume charges. Adsorbent structural changes were studied by X-ray diffraction.

Emerging Control Technologies for Volatile Organic Compounds

Environmental problems associated with volatile organic compounds (VOCs) in the atmosphere have provided the driving force for sustained fundamental and applied research in the area of environmental remediation. Conventional methods currently used to treat VOCs include incineration, condensation, adsorption, and absorption. Incineration and condensation are cost-effective only for moderate to high VOC concentrations. Adsorption and absorption do not destroy VOCs but simply transfer them to another medium. The humid gas stream can plug the condenser and can fill up the adsorption site of the adsorbent. However, none of these methods are cost-effective for the treatment of gas streams with low to moderate concentration and having large numbers of compounds, as the recovery and reuse of the compounds is not economically feasible. A host of alternative remediation technologies, which offer a number of advantages over conventional technologies, are emerging. These include treatment of VOCs with spark-generated carbon aerosol particles, negative air ions treatment, treatment using mesoporous chromium oxide and silica fiber matrix, electrical discharge treatment, electron beam bombardment, and ultraviolet (UV) photooxidation mediated by heterogeneous photocatalyst particles. This review discusses these emerging technologies against the backdrop of conventional approaches for VOC treatment.

Electric discharge treatment of zeolites for purifying the waste water of polymer-manufacturing plants

We present the results of electric discharge treatment of zeolites for purifying the waste water from the manufacture of polymers. By application of the thermostimulated relaxation method, it has been revealed that in the zeolites, superficial and volumetric charges accumulate. It is shown that the electric discharge effects considerably enhance the efficiency of the adsorptive purification of waste water.

Behavior of admixtures in a weakly conducting porous medium with fluids under pulsed pressure excited by an electric discharge

The behaviour of admixtures in a porous medium with fluids under pulsed pressure excited by an electric discharge in surfactant solutions is studied theoretically. A mechanism is revealed for the effect of high-voltage discharges and the mechanical waves excited by them on the behaviour of composite objects (rocks having pores filled with hydrocarbon fluids, i.e. oil and surfactant solution; hard organomineral deposits). A relationship is established for filtration processes in porous materials and oil quality on treatment energy. Features established for the behaviour of composite objects may be effective in creating methods of electric discharge treatment of heterogeneous objects (articles, semifinished products of composite materials) where instead of the deposits of asphalts, resins, paraffins, there may be other admixtures, and instead of the oil and aqueous electrolyte with surfactant there may be other liquids. The results obtained may be used in developing scientific bases for managing the filtration properties of porous materials of different origin (including man-made).

The role of surface modification in digital printing on polymer‐coated packaging boards

AbstractDigital printing is increasingly being used for package printing. One of the major techniques of digital printing is dry‐toner electrophotography. This paper evaluates the printability of three different extrusion coatings used for packaging boards: low‐density polyethylene (PE‐LD), ethylene methyl acrylate (E/MA) and polyethylene terephthalate (PET). Extrusion coatings in general have an impervious, chemically inert, nonporous surface with low surface energies that cause them to be non‐receptive to bonding with toners. The most common methods used in improving the adhesion properties of polymer coatings are different surface treatments. These increase the surface energy and also provide the polar molecular groups necessary for good bonds between the toner and polymer molecules. The polymer coatings have been modified with electrical corona discharge treatment. The effects of corona on polymer surfaces and the correlation between surface modification and print quality have been evaluated. Results show that sufficiently high surface energy and surface‐charge uniformity are necessary for even print quality and toner adhesion. E/MA and PET have the required surface‐energy level without the corona treatment, but PE‐LD needs surface modification in order to succeed in the electrophotographic process. E/MA also has exceptional surface‐charge properties compared with PET and PE‐LD. Polym. Eng. Sci. 44:2052–2060, 2004. © 2004 Society of Plastics Engineers.

Combined Effect of Microwave Field and Focused Laser Radiation on Dielectrics

The combined effect of a microwave electric field and focused laser radiation on dielectrics is investigated with respect to developing a method for electric-discharge treatment. This idea is based on the fact that the absorption of microwave radiation by dielectrics increases when they are previously heated using an additional heat source. Due to this phenomenon, the destruction zone on the dielectric surface can be more narrow than the preheated area.

Tool Surface Topographies for Controlling Friction and Wear in Metal-Forming Processes

A conceptual framework is introduced for the design of tool surface topographies in bulk metal forming processes. The objective of the design is to control friction to desired levels while minimizing wear of the workpiece and tool surfaces and adhesive metal transfer between the workpiece and tool. Central to the design framework are the tool/workpiece interface properties of lubricant retention and interface permeability. Lubricant retention refers to the capacity of an interface to retain lubricant rather than freely channel it to the exterior of the tool/workpiece conjunction. Permeability refers to the capacity to distribute lubricant to all areas within the conjunction. These properties lead to the concept of two-scale surface topography consisting of a fine scale background of interconnected channels on which is superimposed an array of coarser-scale cavities. Control of friction and wear is achieved by designing the tool surface topographies at these two scales to address the unique tribological conditions of specific bulk metal forming processes. The coarser scale is designed to ensure adequate supply of lubricant within the conjunction. The finer scale is designed to ensure adequate delivery of lubricant to all parts of the conjunction where nascent workpiece surface is being formed. The design concepts are illustrated with results from laboratory experiments using the rolling process as an example, and comparing the performance of various roll surface topographies under similar processing conditions. A two-scale surface topography consisting of hemispherical cavities distributed across a background surface of finer scale, interconnected channels was shown to reduce friction compared to a single-scale ground finish, but not as much as a single-scale coarse topography consisting of densely-packed cavities produced by an electrical discharge treatment. On the other hand, the smoother cross-sections of the cavities, especially when elongated in the direction of greatest relative motion, produced significantly less wear than either of the single-scale tool surface treatments. It is concluded that two-scale engineering of tool surface topographies based upon the concepts of lubricant retention and interface permeability can provide a broad basis for achieving desired levels of interface friction while minimizing workpiece surface wear and adhesive material transfer in many metal-forming processes.

19—ELECTRICAL-DISCHARGE TREATMENT OF WOOL AT ATMOSPHERIC PRESSURE

Electrical-discharge treatment of wool fabric at atmospheric pressure increases its wettability and dye absorption. An investigation is described in which the best results were obtained with a glow discharge produced by using a small air gap between the electrodes, low fabric regain, and low relative humidity. With increase in the size of the air gap, regain, and r.h., the discharge was characterized by streamers or sparks or both, and the improvements in wettability and dye absorption were not as good.

Electrical discharge treatment of polypropylene film

The previously observed, but unexplained, deleterious effect of high relative humidity on the efficiency of electrical (‘corona’) discharge treatment for rendering polypropylene film printable has been re-examined. The effect of film temperature during treatment has also been studied. A consistent explanation of both effects based on the degree of surface coverage by physically adsorbed water is put forward, supported by X-ray photoelectron spectroscopy analysis of treated film surfaces.

XPS Studies of Polymer Surface Modifications and Adhesion Mechanisms

Abstract XPS has been used to elucidate the mechanisms of surface modification of low density polyethylene by electrical (“corona”) discharge treatment and by chromic acid treatment. The use of derivatisation techniques for improving the precision of functional group analysis is described. These techniques also allow the role of specific interactions in adhesion to discharge treated surfaces to be investigated. The role of residual Cr on the adhesion of deposited metal to polymer surfaces is discussed.

Derivatization of discharge-treated LDPE: an extension of XPS analysis and a probe of specific interactions in adhesion

Abstract Specific reactions for the derivatization of oxygen-containing functional groups in polymer surfaces have been developed in order to improve the precision of analysis by X-ray photoelectron spectroscopy ( xps ). These have been used to probe the chemical composition of low density polyethylene ( ldpe ) surface-modified by electrical discharge treatment. Simultaneously the effect of derivatizing particular groups on the auto-adhesive behaviour of these surfaces has been examined. Two independent specific interaction mechanisms have been identified.

Surface modification of poly(ethylene terephthalate) by electrical discharge treatment

Poly(ethylene terephthalate) (PET) film has been discharge-treated under controlled conditions and the resulting surface modifications analysed via X.p.s. (ESCA), contact angle and surface energy measurements. Changes in surface properties have been followed as a function of ageing time. These measurements have been correlated with the adhesive properties of the treated surfaces using autoadhesion (treated-treated seals) as the probe. Discharge treatment introduces phenolic -OH and carboxylic acid -COOH groups into the surface resulting in increased wetting and much enhanced autoadhesion via hydrogen bonding of phenol groups to carbonyl groups. Much chain scission also occurs; the low molecular weight material is easily removed by washing and migrates into the film on ageing. The new functionalities in relatively immobile chains slowly reorientate and internally H-bond. The former process is largely responsible for the wettability change on aging, the latter for the loss of adhesive properties.

Surface modification of polyethylene by electrical discharge treatment and the mechanism of autoadhesion

A reexamination of previous studies concerning the electrical (‘corona’) discharge treatment of polyethylene and the resulting enhancement of autoadhesion has been carried out. X-ray photoelectron spectroscopic data provide new insight into the phenomenon by showing surface oxidation to result from treatment in ‘inert’ gases. Treatment in hydrogen is an exception and results in no autoadhesion enhancement even though energy input into the film is more efficient than in air. Autoadhesion theories based on electret formation are rejected; those based on hydrogen bonding are largely up-held and shown to be more generally applicable than at first imagined.

Spark surface hardening of parts

It has been established in mastering spark (electrical discharge) treatment of the surface of parts that the process can be effected on units both with loose and with rotating electrodes, or with follow-up electrode systems. Figure 1 shows a unit for the spark alloying of crane tongs with loose electrodes. Granules of alloys FeCr, FeTi, FeMg, and TiC, as well as different composite materials, served as the electrodes.

Electrical discharge treatment of constructional steels

1. Electrical discharge treatment in combination with heat treatment increases the mechanical and fatigue properties of 18KhNVA, 40Kh1NVA, and 45KhNMFA steels in torsion and bending. 2. Electrical discharge treatment reduces stresses as in low temperature tempering but preserves the strength and hardness of the steel.