Pores coalescence

In general, radiation-induced coalescence looks similar to the process of thermal pore coalescence, which is caused by the fact that small pores eject vacancies more intensively than bigger ones. Both processes lead to the growth of big pores as a result of dissolution of smaller ones, however, physical reasons behind thermally and radiation-induced coalescence are altogether different. In contrast to thermally induced coalescence, radiation-induced coalescence is not related to the ejection of vacancies but results from pore preference Sp being inversely related to the pore radius (Sp = aiJR, where a,v is the difference between the interaction constant of a pore with a vacancy and with an interstitial generated by irradiation). As a result of this relation, small pores adsorb... 

Fig. 8.27 Schematic illustration of grain growth accompanied by pore coalescence. Reproduced with permission fixrm [3]. Copyright 2007, Springer...

Pore coalescence and Surface diffusion Annealing in H2 Sato et al. (2000), Mizushima... 

Figure 9.34 (a) Schematic illustration of grain growth accompanied by pore coalescence. (b) Grain growth and pore coalescence in a sample of UO2 after 2 min, 91.5% dense and 5 h, 91.9% dense, at 1600°C (magnification 400 X ). (From Ref. 75.)... 

Taking Fi, l/G, Na 1/X IG, where X is the interpore distance, and assuming coarsening by grain growth and pore coalescence so that r G, after some rearranging, Eq. (9.89) becomes... 

When the two pores coalescence as a result of grain growth to form a single pore with a radius T2, this pore contains 2n molecules of gas and the limiting condition when it stops shrinking is given by... 

Further sintering of the sample in air leads to grain growth with pore coalescence, with the pores reaching an average size of 4 p,m. Will the porosity be different Explain. If the porosity is different, estimate how different. 

The observation of the plane parallel to the surface of the membrane made it possible to show that the pores had a conical form and formed a honeycomb structure (see Figure 10.5). While progressing from surface towards the interior of the membrane, two dose pores coalesce to form a larger pore. This fusion traces of the coalescence of the phases composing the membrane in formation. These observations imply questions about the phenomena which led to the formation of such structures. The authors proposed a process which suggests that these... 

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