Metallization metal diffusion during

Metal Diffusion During Metallization of High-Temperature Polymers... 

The volume is divided into three parts Part I. Metallization Techniques and Properties of Metal Deposits, Part II, Investigation of Interfacial Interactions," and Part III, "Plastic Surface Modification and Adhesion Aspects of Metallized Plastics. The topics covered include various metallization techniques for a variety of plastic substrates various properties of metal deposits metal diffusion during metallization of high-temperature polymers investigation of metal/polymer inlerfacial interactions using a variety of techniques, viz., ESCA, SIMS, HREELS, UV photoemission theoretical studies of metal/polymer interfaces computer simulation of dielectric relaxation at metal/insulalor interfaces surface modification of plastics by a host of techniques including wet chemical, plasma, ion bombardment and its influence on adhesion adhesion aspects of metallized plastics including the use of blister test to study dynamic fracture mechanism of thin metallized plastics. 

Mercury electrodes require far less maintenance than solid metal electrodes. Especially for the dropping mercury electrode, a noticeable amount of impurities present in the solution at low concentrations (<10-5mol dm-3) cannot appreciably reach the surface of the electrode through diffusion during the drop-time (see Section 5.7.2). 

K. Ratzke, P.W. Huppe, and F. Faupel. Transition from single-jump type to highly cooperative diffusion during structural relaxation of a metallic-glass. Phys. Rev. Lett., 68( 15) 2347-2349, 1992. 

Figure 3. Schematic representation of silicide formation in the solid state, during reaction between a thin (ca. 1000 A) metal film and a thick Si substrate. Either the metal (M), or the Si or both can diffuse during silicide formation.

This paper aims to give a brief review of our present understanding of metal diffusion during polymer metallization and of the implications for the formation and structure of metal-polymer interfaces. For recent more extended reviews the reader is also referred to references 2-4. 

The effects of pulsed waveforms are extremely complex and poorly understood, but the following effects are generally accepted. During the off period of a pulse, no net electron transfer can take place and the cathode surface is refreshed with metal cations as a result of convective diffusion. During the on period, the surface metal ion concentration will initially approach the bulk solution value but will decay with time, i.e. the technique involves non-steady state diffusion. A limiting case is a surface metal ion concentration of zero, i.e. complete mass transport control. The reverse (anodic) current may lead to selective dissolution of high points on the deposit due to their enhanced current density, producing a more compact or smooth surface. 

During exposure in CO2, mild steels produce protective duplex scales (Fig. 3.15(a)), the interface between the two layers being the original metal surface. The zone where the inner oxide layer grows is observed in Fig. 3.15(b) through the presence of chromium, which does not diffuse during the oxidation process. 

Eabrication techniques must take into account the metallurgical properties of the metals to be joined and the possibiUty of undesirable diffusion at the interface during hot forming, heat treating, and welding. Compatible alloys, ie, those that do not form intermetaUic compounds upon alloying, eg, nickel and nickel alloys (qv), copper and copper alloys (qv), and stainless steel alloys clad to steel, may be treated by the traditional techniques developed for clads produced by other processes. On the other hand, incompatible combinations, eg, titanium, zirconium, or aluminum to steel, require special techniques designed to limit the production at the interface of undesirable intermetaUics which would jeopardize bond ductihty. 

Both zirconium hydride and zirconium metal powders compact to fairly high densities at conventional pressures. During sintering the zirconium hydride decomposes and at the temperature of decomposition, zirconium particles start to bond. Sintered zirconium is ductile and can be worked without difficulty. Pure zirconium is seldom used in reactor engineering, but the powder is used in conjunction with uranium powder to form uranium—zirconium aUoys by soHd-state diffusion. These aUoys are important in reactor design because they change less under irradiation and are more resistant to corrosion. 

Processes in which solids play a rate-determining role have as their principal kinetic factors the existence of chemical potential gradients, and diffusive mass and heat transfer in materials with rigid structures. The atomic structures of the phases involved in any process and their thermodynamic stabilities have important effects on drese properties, since they result from tire distribution of electrons and ions during tire process. In metallic phases it is the diffusive and thermal capacities of the ion cores which are prevalent, the electrons determining the thermal conduction, whereas it is the ionic charge and the valencies of tire species involved in iron-metallic systems which are important in the diffusive and the electronic behaviour of these solids, especially in the case of variable valency ions, while the ions determine the rate of heat conduction. 

A number of metals, such as copper, cobalt and h on, form a number of oxide layers during oxidation in air. Providing that interfacial thermodynamic equilibrium exists at the boundaries between the various oxide layers, the relative thicknesses of the oxides will depend on die relative diffusion coefficients of the mobile species as well as the oxygen potential gradients across each oxide layer. The flux of ions and electrons is given by Einstein s mobility equation for each diffusing species in each layer... 

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