Electromagnetic-shielding layers

Formulated with pigments, like graphite and carbon black [232] or metal powders [233,234], conductive films were obtained at low cost, used as electromagnetic shielding layers or for capacitive energy-storing inductive coils, when coated on an insulated magnet wire. 

Various copolymers with the basic backbone of —Ar—NH—Ar—S—, i.e., aromatic amino sulfide copolymers have been synthesized. This type of copolymer is semiconducting and can be used in many electronic and electro-optical applications. Examples of such applications are antistatic layers, electromagnetic-shielding layers, anticorrosion layers, batteries, electroluminescent devices, and in electronic circuits, such as conductor tracks of transistors. 

When metallic coatings are applied for radio-frequency or electromagnetic shielding electroless copper always is used (its superior electrical conductivity gives excellent performance) but in order to protect the copper against abrasion and corrosion it is necessary to apply a top layer of nickel. 

In addition, there is also the possibility of tailoring the properties of plain composites further by adding particles (such as metallic fillers [29,30], carbon nanotubes [31] or urea formaldehyde [32]) to the composite layers to create multifunctional and self-healing materials, von Klemperer and Maharaj [29] added copper and aluminium powder fillers to carbon fibre epoxy laminates to improve the electromagnetic shielding capacity of the composite panels. Blast tests on the laminates [30] showed that the laminates with filler particles outperformed their plain composite counterparts, although the margin was small. 

Polymer surfaces are modified by plasma techniques for interfacial enhancement [4-10], Au, Ag, Pd, Cu and Ni were coated on poly (methylmethacrylate) (PMMA) by barrel technique [11]. Coating of A1 alloys on PET was compared with Ti layer under A1 alloys [12]. Thin Aluminum oxide coatings have been deposited on various uncoated papers, polymer-coated papers and plain polymer films using atomic layer deposition technique [13]. The isotactic polypropylene (iPP) and A1 composite is widely used as television cable electromagnetic shielding materials [14], The reflection of infrared light depends on geometry of the surface of alumi-... 

Nonetheless, the WHO recommended that brominated flame retardants should not be used where suitable replacements are available . Plastics containing no flame retardants are now being used in computer monitor housings. These have an internal fireproof metal layer, which also provides electromagnetic shielding. Whether this is a satisfactory substitute for flame retardants is still very uncertain. 

Another type of electronic connector joins coaxial conductors. These have a soHd or stranded center-conductor surrounded by a dielectric. The dielectric is covered with a conductive shield made of metal braid or tape and with a layer of insulation. Coaxial cable connectors terminate the center-conductor and the shield. These are used primarily in radio frequency circuits. The shape, dimensions, and materials of an electronic connector shell or stmcture may have to be designed to shield the connection from electromagnetic and radio frequency interferences in many appHcations. 

The idea of using CPCM for shielding is rather alluring. Indeed, a casing of an article or instrument manufactured of such a material serves at the same time as a screen to protect against electromagnetic radiation. All the above-described operations involved in applying additional layers become unnecessary. 

Benzotriazole has also been used as an additive in anticorrosive coatings for silver layered on plastic film <89JAP8909733). An anticorrosive, electromagnetic wave-shielding coating containing tolyltriazole has been developed for aluminum <91EUP437979). 

Ozone absorbs ultraviolet radiation below 320 nm. It thus forms an indispensable shield in the upper atmosphere, protecting the Earth s surface from most of the potentially hazardous effects of such high-energy electromagnetic radiation. There is now increasing concern because atmospheric pollutants are depleting the ozone layer worldwide, with the most serious depletion over Antarctica as a result of seasonal variations in high-altitude air circulation. In the upper atmosphere, ozone is formed from O2 ... 

Because ozone selectively absorbs these deleterious wavelengths of solar radiation, it serves as an ultraviolet shield. As such, stratospheric ozone helps to protect humans and other organisms on Earth s surface from some of the harmful effects of exposure to this high-energy electromagnetic radiation, hi fact, without the protective action of the stratospheric ozone layer, it is likely that... 

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