Fine α-alumina with low alkali: new approach for preparation

Исупов, В. П.; Chupakhina, L. E.; Kryukova, G. N.; Tsybulya, S. V.

doi:10.1016/s0167-2738(01)00846-3

Cited by 15 publications

(11 citation statements)

References 6 publications

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“…Among the various crystal structures, alumina that reveals electric insulation is of type. The -alumina has been conventionally produced by annealing aluminum hydroxide derived from aluminum salts or minerals at temperatures higher than 1000 ∘ C [7][8][9][10]. The -alumina can be also produced by fabricating amorphous alumina with methods using liquid phase such as precipitation and sol-gel process and then annealing it at high temperature [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Low Temperature Synthesis of α-Alumina with a Seeding Technique

et al. 2013

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This paper reports a method for producing -Al 2 O 3 at low temperature, which uses a seeding technique. White precipitate of aluminum hydroxide, which was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution, was peptized by using acetic acid at room temperature and then transformed to a transparent alumina sol. To the alumina sol -Al 2 O 3 particles were added as a seed, and then the sol containing -Al 2 O 3 particles was transformed to an -Al 2 O 3 -seeded alumina gel by drying the sol at room temperature. The nonseeded alumina gel was amorphous or fine crystallites even after being annealed at 600 ∘ C and was crystallized to -Al 2 O 3 at 700 ∘ C. The -Al 2 O 3 seeding promoted crystallization of alumina gel toAl 2 O 3 . The promotion of crystallization was made remarkable with a decrease in -Al 2 O 3 particle size and an increase in -Al 2 O 3 particle content in weight for the final seeded alumina gel. With an -Al 2 O 3 particle size of 150 nm and an -Al 2 O 3 particle content of 5%, the seeded alumina gel was partially crystallized to -Al 2 O 3 by annealing at a temperature as low as 700 ∘ C and mostly at 900 ∘ C.

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Section: Introductionmentioning

confidence: 99%

Low Temperature Synthesis of α-Alumina with a Seeding Technique

et al. 2013

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“…The volume and shape are well preserved. [3][4][5][6][7][8][9] The phenomena have been used to fabricate ceramic substrates of lower volume shrinkage as well as porous ceramics 10,11 because the outward morphology preservation of the gibbsite particles may provide lower volume shrinkage to the ceramic body if the particles cannot move freely. The previously reported mechanism for the development of a pseudomorph (pseudomorphism) involves alteration, substitution, incrustation, or paramorphism between the related minerals.…”

Section: Introductionmentioning

confidence: 99%

“…1,13 After complete phase transformation to corundum, the crystal retains its original habits. [3][4][5][6] It is interesting to find that the mineral undergoes a volume reduction of 39% due to an increase in density during the transformation. From gibbsite to w-Al 2 O 3 , to k-Al 2 O 3 , and finally to a-Al 2 O 3 (corundum), the density increases from 2.42 to B3.0, to 3.72, and finally to 3.98 g/cm 3 , respectively.…”

Section: Introductionmentioning

confidence: 99%

Low Shrinkage Nanoscaled Transition‐Alumina Crystal Aggregates of Gibbsite

Yen

Cheng

Huang

et al. 2009

Journal of the American Ceramic Society

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The low volume shrinkage phenomena occurring during thermal treatments of gibbsite (Al(OH) 3 ) crystal were examined using TEM techniques. Normally, gibbsite shows a pseudomorphic transformation. The outward gibbsite crystal form can be preserved despite the fact that phase transformation proceeds from gibbsite to v-, to j-, then to a-phase alumina. Examinations revealed that a sequential nanocrystal habit evolution developed, from v-flak to j-pillar or pole, then to a-pea pods, as phase transformation proceeded. Calculations relating the increases in sequential density with the corresponding new packing patterns exhibited as transition phases occur demonstrate that pseudomorphic transformation can be performed perfectly. It is this mechanism that eventually leads to the low volume shrinkage of gibbsite aggregates.

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“…Isupov et al (2001) recently proposed a laboratory technique for making fine and low soda materials by first treating technical-grade aluminium trihydroxide (of 85-90 μm in mean particle size) containing 0.14% Na 2 O from an alumina plant with Li salts (Li chloride, nitrate and sulphate) at 90°C. This allows the intercalation of Li ions into the aluminium hydroxide structure.…”

Section: Introductionmentioning

confidence: 99%