Pore creep

Pore-Creep in Electrical Contacts and Metallic Joints... 

High Contact Resistance on Gold-Plated Connector Contacts Caused by Pore-Creep Corrosion... 

At temperatures in excess of 750°C the addition of water vapour accelerates the rate of growth of FeO (Fig. 7.10) by producing large pores in the FeO" . At much higher temperatures (1 200°C) Sheasby et have found that addition of steam to Oj-Nj, Oj-HjO-Nj and HjO-Nj, in a simulated reheating atmosphere furnace, caused increases in scale growth due to improved adhesion at the scale/metal interface. They concluded that water vapour enhances scale creep as previously reported by Tuck et... 

As to the particular way in which solvent manages to creep through the membrane, to the exclusion of solute, nothing definite can be said. We might assume that the action of the membrane is of the character of a sieve, the smaller solvent molecules getting through its pores whilst the larger... 

Even though the above work is providing a stable, non-sintering, creep-resistant anode, electrodes made with Ni are relatively high in cost. Work is in progress to determine whether a cheaper material, particularly Cu, can be substituted for Ni to lower the cost while retaining stability. A complete substitution of Cu for Ni is not feasible because Cu would exhibit more creep than Ni. It has been found that anodes made of a Cu - 50% Ni - 5% A1 alloy will provide long-term creep resistance (36). Another approach tested at IGT showed that an "IGT" stabilized Cu anode had a lower percent creep than a 10% Cr - Ni anode. Its performance was about 40 to 50 mV lower than the standard cell at 160 mA/cm. An analysis hypothesized that the polarization difference could be reduced to 32 mV at most by pore structure optimization (37). 

The increase of thus induces a macroscopic creep under constant stress. Assuming an instantaneous diffusion of the solute within the pore space, the mechanical affinity is Am —psij/el. The strain concentration effect at the crack tip then implies that the dissolution process concentrates at this place and is negligible elsewhere. The rate of crack radius increase a is derived from (22) and gives the evolution f(t) of the damage parameter ... 

In the absence of suspended solutes or colloids, the pure solvent flux through an ultrafiltration membrane is directly proportional to the applied pressure difference and inversely proportional to the viscosity of the solvent and the membrane thickness. Transport within the pores occurs in the creeping flow regime, since kinematic viscosities of liquids are sufficient to make Re < C 1 for practical pore sizes. In the simplest case, the membrane can be considered to be a packed array of straight, equal diameter nonintersecting capillary tubes. The observed volumetric flux, nAvA (cc/sec cm2), equals the product of the mass flux of solvent based on the total membrane area, nA... 

Anode Anode sintering Anode deformation and creep Extent of electrolyte filling Change in the pore structure, gas leak through the edges, poor strength Forms a BBP layer Increase in the polarization due to increase in the area of the electrode... 

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