Conclusions
The sintering of well-brine magnesium hydroxide proceeds in accordance with the laws governing solid-phase sintering, regardless of its degree of purity (within an MgO content of 96–98%) and of the type of precipitant used.
The contraction kinetics of the magnesium hydroxide under isothermal conditions is characterized by the fact that Δl/lis approximately proportional to t1/2. The contraction and compaction rates are at a maximum at 1000–1300°C and decrease significantly at higher temperatures.
The contraction rate of specimens from calcined magnesium hydroxide was found to be 2–3 times lower than that of dried magnesium hydroxide.
The specimens are compacted while contracting; in the elimination of the open pores ΔP/P is approximately proportional to t1/2 and in that of the closed pores to t1/3.
With an increase in the temperature from 1000 to 1700°C the compaction of the material is accompanied by periclase recrystallization. The periclase grains begin to grow rapidly after 1500δC at an open porosity of 10–12%.
At a temperature above 1500°C the recrystallization rate is so high that some open pores are entrapped in the growing crystals, resulting in closed porosity, the elimination of which is difficult. The sintering rate increases sharply at the same time.
Given these general regularities, which support earlier findings, it is possible that the contraction will vary slightly with the chemical composition and heat treatment conditions of the specimens of well-brine magnesium hydroxide.
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Translated from Ogneupory, No. 6, pp. 39–44, June, 1974.
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Bunina, V.P., Dolgina, G.Z. & Ivanov, E.V. The sintering kinetics of well-brine magnesia. Refractories 15, 372–376 (1974). https://doi.org/10.1007/BF01284172
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DOI: https://doi.org/10.1007/BF01284172