Formation of porous α-alumina from ammonium aluminum carbonate hydroxide whiskers

Ahmad, Jamal; Tariq, Muhammad Ismail; Ahmad, Rizwan; ul-Hassan, Syed Mujtaba; Mehmood, Mazhar; Khan, Abdul Faheem; Waseem, Shabana; Mehboob, Shoaib; Tanvir, Muhammad Tauseef

doi:10.1016/j.ceramint.2018.11.154

Cited by 12 publications

(7 citation statements)

References 20 publications

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“…Lee at al. obtained α-Al 2 O 3 with an A BET of 25 m 2 /g at 900 • C with hydrothermally synthesized aluminum oxalate hydroxide precursors [39], while Ahmad et al recently reported on α-Al 2 O 3 from hydrothermally prepared ammonium aluminum carbonate hydroxide whiskers with distinct pore diameters of 260 nm, yet without precisely determining the corresponding pore volume [40,41].…”

Section: Hydrothermal Synthesesmentioning

confidence: 99%

“…Topuz et al reported pore diameters of 110 nm in macroporous α -alumina supports prepared by using vacuum assisted filtration of α-Al 2 O 3 suspensions [174]. Finally, three articles were published in 2019: Ahmad et al reported on α-Al 2 O 3 from hydrothermally prepared ammonium aluminum carbonate hydroxide whiskers with distinct pore diameters of 260 nm, yet without precisely determining the corresponding pore volume [41]. Quite an interesting morphology in sol-gel α-Al 2 O 3 was reported very recently by Roque-Ruiz et al They obtained fibers with diameters of 230-900 nm by electrospinning an aluminum nitrate precursor solution [175].…”

Section: Pure α-Alumina With Pores In the Sub-micrometer Rangementioning

confidence: 99%

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Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

2020

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This article combines a systematic literature review on the fabrication of macroporous α-Al2O3 with increased specific surface area with recent results from our group. Publications claiming the fabrication of α-Al2O3 with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA α-Al2O3 is given, including hydrothermal methods, pore protection approaches, dopants, anodically oxidized alumina membranes, and sol-gel syntheses. Furthermore, limitations of these routes are disclosed, as thermodynamic calculations suggest that γ-Al2O3 may be the more stable alumina modification for ABET > 175 m2/g. In fact, the highest specific surface area unobjectionably reported to date for α-Al2O3 amounts to 16–24 m2/g and was attained via a sol-gel process. In a second part, we report on some of our own results, including a novel sol-gel synthesis, designated as mutual cross-hydrolysis. Besides, the Mn-assisted α-transition appears to be a promising approach for some alumina materials, whereas pore protection by carbon filling kinetically inhibits the formation of α-Al2O3 seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders.

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Section: Hydrothermal Synthesesmentioning

confidence: 99%

Section: Pure α-Alumina With Pores In the Sub-micrometer Rangementioning

confidence: 99%

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

2020

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“…In addition, Y. Tamura et al found that by using α-Al whiskers and found that it had excellent biocompatibility and drug loading and release characteristic [17], whereas, until now, no research has been done to investigate θ-Al 2 O 3 whisker. Since it is also one high temperature phase member of alumina whiskers, it is believed that except the members of γ-Al 2 O 3 and α-Al 2 O 3 whiskers [18][19][20][21][22][23][24][25] the θ-Al 2 O 3 whisker may also play one important reinforcing role in the composites.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of θ-Al2O3 Whiskers with Twins

Liao

Zhang

et al. 2021

Metals

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In this work, θ-Al2O3 whiskers with twins were successfully fabricated by a hydrothermal method followed by annealing at 1000 °C in argon atmosphere using Al2(SO4)3·18H2O, CO(NH2)2 and PEG2000 as initial materials. It is confirmed that precursor of AlO(OH) whiskers is suitable to be used for preparing alumina whiskers when the molar ratio of Al3+: CO(NH2)2 is selected to be 1:6. The mean length of obtained whiskers is 1.5 μm and the average width is 0.1 μm. Interestingly, it is found that the as-prepared θ-Al2O3 whiskers consist of twins with (100) plane as the twin surface, which is ascribed to the phase transformation from tetragonal phase (δ-Al2O3) to monoclinic phase (θ-Al2O3) during the annealing. Additionally, the specific surface area of θ-Al2O3 whiskers is measured to be 38.2 m2/g.

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“…Several low temperature phases of aluminum oxide convert to α -alumina ( α -Al 2 O 3 ) through heating over 1150°C [1,2]. Its natural form is known as the corundum mineral.…”

Section: Introductionmentioning

confidence: 99%

Isothermal compressibility and isobaric thermal shrinkage of a porousα-alumina compact: thermodynamic calculations

2020

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Two methods were proposed to calculate the thermodynamic parameters of porous ceramic compacts depending on their molar volume change with applied pressure and heating temperature, respectively. Molar volume of the porous α-alumina (α-Al 2 O 3 ) compact was evaluated according to literature depending on both the applied pressure at room temperature and the heating temperature at atmospheric pressure. The isothermal compressibility coefficient, Gibbs energy, and work done on the compact by compression were calculated. The thermal shrinkage coefficient and activation energy as well as the change in enthalpy, entropy and Gibbs energy were calculated for partial sintering. The spontaneous nature of the treatments were discussed with respect to the obtained results.

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Formation of porous α-alumina from ammonium aluminum carbonate hydroxide whiskers

Cited by 12 publications

References 20 publications

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Synthesis of θ-Al2O3 Whiskers with Twins

Isothermal compressibility and isobaric thermal shrinkage of a porousα-alumina compact: thermodynamic calculations

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