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Flocculation clustering and weakness of ceramics

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Abstract

IT is well-known that the mechanical properties of ceramics are sensitive to flaws which cause weakness1,2. The most damaging flaws are large gas bubbles or particulates which contaminate the ceramic moulding during the compaction process, and which are not healed by sintering3–5. But even when great care is taken to remove such extraneous flaws, for example by filtering or by fabricating under clean room conditions, the strength of the ceramic does not rise to the level expected from the fine structure of the material (M. Real, personal communication), suggesting that some more fundamental intrinsic problem limits the strength. Here we describe a new phenomenon, flocculation clustering, which can account for the low strengths observed. An equation is derived to predict the size of the clusters and is verified by experiments on flocculation of titania sols. We find that flocculation clustering can also be observed in other colloidal systems, such as silica and polystyrene dispersions.

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Authors and Affiliations

  1. ICI, PO Box 11, Runcorn, Cheshire, WA7 4QE, UK

    K. Kendall, N. McN. Alford, W. J. Clegg & J. D. Birchall

Authors
  1. K. Kendall
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  2. N. McN. Alford
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  3. W. J. Clegg
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  4. J. D. Birchall
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Kendall, K., Alford, N., Clegg, W. et al. Flocculation clustering and weakness of ceramics. Nature 339, 130–132 (1989). https://doi.org/10.1038/339130a0

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