Sintering contact material

Conta.ctMa.teria.ls, Electrical contact materials are produced by either slicing rod made from metal powder, infiltrating a porous refractory skeleton, or compaction and sintering of powders (see Electrical CONNECTORS) (51—53). 

Compared with a Teflon -bonded commercial electrode, the composite electrode showed lower polarization losses at high current densities, even though the composite material did not contain Pt. The ohmic and mass transfer resistances were lower in the composite electrode than in the commercial electrode. The sintered contacts and interlocked networks formed in the composite structure permitted better electrical and physical contact between the carbon fibres and metal fibres, leading to a composite electrode with a high void volume and large macroscopic porosity, which increased the accessibility of carbon to the reactants [22],... 

Figure C2.11.6. The classic two-particle sintering model illustrating material transport and neck growtli at tire particle contacts resulting in coarsening (left) and densification (right) during sintering. Surface diffusion (a), evaporation-condensation (b), and volume diffusion (c) contribute to coarsening, while volume diffusion (d), grain boundary diffusion (e), solution-precipitation (f), and dislocation motion (g) contribute to densification.

Sintering consists of heating a mixture of fine materials to an elevated temperature without complete fusion. Surface diffusion and some incipient fusion cause the soHd particles in contact with one another to adhere and form larger aggregates. In the processing of hematite, Fe202, or magnetite,... 

Copper and silver combined with refractory metals, such as tungsten, tungsten carbide, and molybdenum, are the principal materials for electrical contacts. A mixture of the powders is pressed and sintered, or a previously pressed and sintered refractory matrix is infiltrated with molten copper or silver in a separate heating operation. The composition is controlled by the porosity of the refractory matrix. Copper—tungsten contacts are used primarily in power-circuit breakers and transformer-tap charges. They are confined to an oil bath because of the rapid oxidation of copper in air. Copper—tungsten carbide compositions are used where greater mechanical wear resistance is necessary. 

Sintering. A ceramic densiftes duriag sintering as the porosity or void space between particles is reduced. Additionally, the cohesiveness of the body iacreases as iaterparticle contact or grain boundary area iacreases. Both processes depend on and are controlled by material transport. 

For increased power requirements, electrode constructions have been developed which bring the electronic conductors in closer contact with the active material particles first, around 1930, the sinter electrode [110], recently in sealed cells largely replaced by the nichel-foam electrode, and then, around 1980, the fiber structure electrode [111]. In order to take full advantage of their increased perform-... 

In order to interpret correctly the results of electrophysical measurements conducted on vacuum - sintered ZnO semiconductor films one should answer the question concerning the origin of contacts between specific crystallites controlling the electric conductivity of the material. This was accomplished in paper [37] using the method of prerelaxation VAC to run a comparative analysis of mechanisms of charge transfer in thin sintered (in vacuum) films and pressed polycrystalline ZnO samples. 

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