An acoustic study of the mixed-alkali-mixed phase β-aluminas. Part 1: Naβ″/β_Al2O3, Kβ″/β_Al2O3 and (Na0.6K0.4)β″/β_Al2O3

Patel, N. D.; Nicholson, Patrick S.

doi:10.1016/0167-2738(87)90148-2

Cited by 8 publications

(2 citation statements)

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“…In addition to Ca 2+ ions, various other ions are present in the CAC‐bonded castable, such as Fe 3+ or Mg 2+ listed in Table , which are known to incorporate into the β‐Al 2 O 3 structure. Incorporation of such ions into the spinel‐like planes of the β‐Al 2 O 3 has been shown to impede the motion of the Na + ions increasing the activation energy for ionic conductivity . The presence of grain boundaries has also been shown to reduce Na + mobility .…”

Section: Resultsmentioning

confidence: 99%

“…The presence of grain boundaries has also been shown to reduce Na + mobility . While the effect of Na + ion hopping on damping has been measured elsewhere at considerably lower temperatures, the incorporation of other ions and the presence of numerous grain boundaries, could explain the shift of the damping peak to higher temperatures . The large damping peak between 1200°C and 1000°C upon cooling could therefore be caused by hopping of Na + ions.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Sodium on Microstructures and Thermoelastic Properties of Calcium Aluminate Cement–Bonded Refractories

et al. 2015

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The effect of sodium on refractory phase formation in a model Calcium Aluminate Cement-bonded refractory was investigated from 700°C to 1500°C. Sodium reacts with a-alumina to form sodium b-alumina (b-Al 2 O 3 ) via the intermediate NaAlO 2 . Formation of b-Al 2 O 3 disrupts the reaction path of calcia with alumina, delaying crystallization of calcium hexaluminate, CaOÁ6Al 2 O 3 , from 1350°C to 1500°C. b-Al 2 O 3 is also shown to reduce Young's modulus and delay sintering. The presence of NaAlO 2 and b-Al 2 O 3 result in an increase in internal friction. Increased linear expansion of up to 47% is observed when 1 wt% Na is added. The expansion is shown to scale with the amount of dopant with only 0.3 wt% Na leading to an additional 31% linear expansion. On cooling, the presence of bAl 2 O 3 can be demonstrated by a peak in internal friction between 1200°C and 1000°C which could be caused by Na + ion hopping along the spinel-like planes.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%