Influence of cryogenic drying conditions on hierarchical porous structure of aluminum oxide systems

Sinkó, Katalin; Kobzi, Balázs; Sinclaire, Jeremy; Baris, Adrienn; Temesi, Ottó

doi:10.1016/j.micromeso.2015.06.018

Cited by 13 publications

(3 citation statements)

References 40 publications

(56 reference statements)

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“…Ultimately, porosity of the synthesized gels much depends on the chosen drying conditions. Xerogel granules can be obtained by evaporative drying methods, cryogels by freeze-drying [70,71], or aerogel monoliths by drying under supercritical conditions, respectively [65,72]. Whichever drying method is chosen, it cannot effectively prevent the collapse of mesopores originating from the sol-gel process upon high temperature calcination, which is necessary to accomplish the phase transition from θto α-Al 2 O 3 .…”

Section: Introducing Porosity Via Soft Templating In Sol-gel Synthesesmentioning

confidence: 99%

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: Introducing Porosity Via Soft Templating In Sol-gel Synthesesmentioning

confidence: 99%

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

2020

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“…The viscous system is soluble in water, but at an Al concentration of about 10-15 wt% (0.7 M), the solution turns into an optically clear gel after several hours. The second step is the freeze drying of the monolith hydrogel (at 233 K in a Christ, Alpha 2-4 LD plus cryostat instrument) [29].…”

Section: Preparation Of Aluminum Oxide Cryogelsmentioning

confidence: 99%

“…The latter size is determined essentially by the rate of freezing [29]. The application of supercritical conditions leads to formation of aerogels with nanopores.…”

Section: Synthesis and Drying Of Highly Porous Aluminum Oxide Systemsmentioning

confidence: 99%

Absorbability of Highly Porous Aluminum Oxide Ceramics

Sinkó¹

2017

JMSE-A

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Highly porous aluminum oxide ceramics were synthesized by various low energy consumption techniques. This work demonstrates the efficiency of the preparation technique to tailor the structure of the materials. The drying method was varied and applied in vacuum (freeze drying), under supercritical conditions, and at atmospheric pressure. The pore system and the absorbability can be significantly affected by the conditions of the drying process. The absorbability of porous materials was compared basically for organic compounds. The gas and liquid adsorption measurements were carried out on a gas chromatography and mass spectrometry instrument. The absorbability of several porous aluminum oxide materials was compared to the adsorption data of pure carbon.

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Ice-Templating: Processing Routes, Architectures, and Microstructures

Deville

2017

Engineering Materials and Processes

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Influence of cryogenic drying conditions on hierarchical porous structure of aluminum oxide systems

Cited by 13 publications

References 40 publications

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Absorbability of Highly Porous Aluminum Oxide Ceramics

Ice-Templating: Processing Routes, Architectures, and Microstructures

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