Surface metallisation

Impurities that can negatively affect the physical and electrical properties of the metallisation layer can originate from several sources, particularly the deposition source and the gaseous environment. Impurities stemming from the source bombard the surface of the growing film and get trapped in the metal layer. 

Finally, the metallisation layer usually requires patterning, which can be done by reactive ion etching (RIE) or back-sputtering. The two processes are similar. In both techniques accelerated ions hit the substrate and forcibly detach atoms or molecules from the surface. RIE uses reactive gases such as chlorine, Cl or trichlorofluoromethane [75-69-4] CCl E. Inert gases such as argon or neon are used in back-sputtering. 

Aluminium is widely applied for decorative and protective requirements, while cadmium , zinc and titanium have been applied to ferrous materials chiefly for their protective value. The method finds particular application in the plating of high-tensile steels used in aviation and rocketry, car fittings and lamp reflectors, and gramophone record master discs, as well as in the preparation of specimens for electron microscopy and in rendering insulated surfaces electrically conducting, e.g. metallising of capacitors and resistors. 

Films of polyolefins, polyamides and poly(vinylidene dichloride) are made using this technique. As most of the films are used for flexible packaging, further down-stream surface treatments are usually applied to improve performance. For example, aqueous polymer emulsions, e.g., poly(vinylidene dichloride), or delaminated clay particles improve the barrier properties as will metallising with aluminium vapour. Corona discharge, causing slight surface oxidation, improves printability. 

Metallisation is a process in which a metal ion is absorbed by a conventional fibre, followed by chemical reduction of the absorbed metal ions to its metallic phase. In this case, conduction is also obtained through the entire fibre but with a limited rate, dependent on the density of metal ion absorbed in the fibre and adsorbed at the surface of the fibre. 

Galvanisation of the metallised fibre will improve its properties as electrical conductor because of the formation of a continuous metallic coating at the surface of the fibre. In this respect, the seed layer formed during metallisation is crucial for a good adhesion between the metal layer and the PAN-fibre structure. 

Another way of surface improvement is metallising. Very thin metal layers (up to a few pm), are deposited by evaporating the metal under vacuum. This method can be applied to all types of plastics. Metallised films find their application in electrotechnics and as reflectors for radiant heat. In an electric oven aluminium is evaporated, while the vapour is precipitated on the surface to be treated in most cases an extra protective transparent layer is added. 

SEM/TEM-EDX Yes mm or urn sample Metallisation for SEM/ deposit of powder on Cu or Au grid or thin section for TEM Surface analysis/ surface or bulk analysis as a function of sampling Some hundreds of nm/some hundreds of A 1 wt.%... 

Electron microprobe WDX Yes mm or im sample Metallisation Surface analysis Some hundreds of nm 0.5wt.%... 

Metallising Applying a thin coating of metal to a non-metallic surface. May be done by chemical deposition or by exposing the surface to vaporised metal in a vacuum chamber. 

Metallised PP/PP laminate (outer PP film reverse-printed with nylon-based resin ink) bag PP film (fuUy printed on outer surface) heat-sealed single packs packed in PP film heat-sealed multipack (partially printed on outer surface) Cartonboard boxes in PP film overwrap (coated on both surfaces with VdC copolymer)... 

Preparation of a polished section can also be used for semi-quantitative elemental analyses which aids phase identification. The surface of the polished section is generally metallised with carbon, as absorption of the characteristic signals by this element is low. 

As catalysts are generally insulating, it is necessary to metallise the surface to be examined and ensure that it is earthed in order to enable the flow of charge from the electron beam. A metallization layer (generally made of carbon) is deposited via thermal evaporation under vacuum (carbon has the advantage of not being particularly absorbent vis-a-vis the incident electrons and vis-ii-vis the characteristic X-rays). The electrical contact with the sample holder is created using a silver or carbon lacquer. 

Uniform n-Si/CHsOH-dmFc contact (bare n-Si surface) Heterogeneous n-Si/Ni/E prepared using 174 nm diameter spheres Uniform n-Si/Ni contact (completely metallised surface) n-Si/Ni/E theory interacrting contact model n-Si/Ni/E theory independent contact model n-Si/Ni/E photoresponse predicted from dark response... 

The carrier may be glassine, cellulose film, and polyester film. The choice of carrier relates to speed and transfer temperature. Polyester (i.e. Melinex) is the most common base. It is suitable for flat, cylindrical or radiused surfaces. The process is used for online printing. Metallic foil consists of a carrier, release coating, lacquer metallised layer and a hot melt type adhesive specially formulated for the substrate. 

Plastics can have a layer of metallic aluminium deposited on the surface by vacuum. Although aluminium is basically a bright silver, it may be lacquer tinted to give a wide range of metallic colours. Polyester, polystyrene, urea and phenol formaldehyde, and polypropylene are readily metallised. Other plastics need a pretreatment. 

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