Soviet Powder Metallurgy and Metal Ceramics

, Volume 5, Issue 9, pp 703–708 | Cite as

Densification during the hot pressing of magnesium oxide with additions

  • I. S. Kainarskii
  • M. I. Prokopenko
  • I. G. Orlova
Theory and Technology of Sintering, Heat Treatment, and Chemicothermal Treatment Processes
Received:
  • 41 Downloads

Summary

  1. 1.

    The effect of various additions depends on the type of magnesium oxide. Thus, the additions investigated fail to raise the density of hot-pressed specimens from “p” magnesium oxide for luminophores, but enable the final pressing temperature to be lowered by 100–300°C. For extra-light magnesium oxide, the additions have practically no effect on the limiting temperature securing the maximum densification of specimens, but increase the density of the latter.

     
  2. 2.

    It was established that many of the additions lower the density of hot-pressed specimens at limiting pressing temperatures above 1600–1700°C (“p” magnesium oxide for luminophores) or above 1400°C (extra-light magnesium oxide) because of an increase of sealed porosity, which is probably due to the generation of excess vacancies on pressure removal.

     
  3. 3.

    When the amount of an addition is raised from 0.5 to 4 mol.%, densification shifts into the region of lower temperatures, while the density may actually increase.

     
  4. 4.

    The densification kinetics during the hot pressing of the two grades of magnesium oxide with additions are characterized by proportionality between ΔD/D0 and t1/3. It is shown that the increase in the width of the nonporous crust of periclase crystals at the final stages of hot pressing is also proportional to t1/3. This indicates a diffusion mechanism of the elimination of sealed (intragranular) pores during hot pressing and confirms the diffusion character of densification at the last stages of the hot pressing of magnesium oxide.

     

Keywords

Oxide Porosity Magnesium Final Stage Diffusion Mechanism 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Consultants Bureau 1967

Authors and Affiliations

  • I. S. Kainarskii
    • 1
  • M. I. Prokopenko
    • 1
  • I. G. Orlova
    • 1
  1. 1.Ukrainian Scientific-Research Institute of RefractoriesUSSR

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