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A critical examination of a cryochemical method for the preparation of high surface area semiconducting powders

Part 1 Rate of freeze-drying

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Abstract

In the preparation of high surface area powders by the method of freeze-drying, a solution of the dissolved substance is rapidly frozen in liquid nitrogen, followed by vacuum sublimation of the ice. A computer analysis of the vacuum sublimation step showed that the heat supply to the surface ice was less than that for maximum sublimation. An infra-red lamp was used to supply extra heat and, in agreement with the computer model, the time required for sublimation of 100 g ice fell from 42 h to 3.8 h. The ice did not melt. Conductivity measurements of samples of freeze dried 10 at % Li doped NiSO4 prepared with and without the extra heat supply showed that in both cases, a very uniform distribution of Li+ in the NiSO4 lattice had been achieved. The surface areas of the freeze-dried samples were 3 times that of a sample of 10 at % Li doped NiSO4 which had been prepared by boiling to dryness a solution of LiSO4 and NiSO4.

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Authors and Affiliations

  1. Department of Chemistry, The City University, London, UK

    J. Kelly, D. B. Hibbert & A. C. C. Tseung

Authors
  1. J. Kelly
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  2. D. B. Hibbert
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  3. A. C. C. Tseung
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Kelly, J., Hibbert, D.B. & Tseung, A.C.C. A critical examination of a cryochemical method for the preparation of high surface area semiconducting powders. J Mater Sci 13, 1053–1060 (1978). https://doi.org/10.1007/BF00544701

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  • DOI: https://doi.org/10.1007/BF00544701

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