Molten salt synthesis of α-Al2O3 platelets using NaAlO2 as raw material

Zhu, Lihui; Tu, Ranran; Huang, Qinghong

doi:10.1016/j.ceramint.2011.08.008

Cited by 25 publications

(9 citation statements)

References 10 publications

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“…Less often encountered are molten salt syntheses to produce platelets of about 2 µm × 0.1 µm by thermal decomposition of a precursor salt such as polyaluminum chloride, ammonium aluminum carbonate hydroxide, or NaAlO 2 [131][132][133][134]. However, BET surface areas attainable for these dimensions would still be relatively low.…”

Section: Miscellaneous Methodsmentioning

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: Miscellaneous Methodsmentioning

confidence: 99%

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

2020

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“…The basis for the nano-TiO 2 -induced formation of thick α-Al 2 O 3 platelets has been previously investigated [19,20]. At elevated temperatures, Al 3+ vacancies are generated by the diffusion of Ti 4+ ions into the crystal lattice of Al 2 O 3 .When a Ti 4+ ion replaces an Al 3+ ion, the lattice deforms owing to the larger ionic radius (0.068nm) of the former compared to that (0.053nm) of the latter; as a result, the difference between the growth velocities of differing crystal faces of α-Al 2 O 3 is reduced.…”

Section: Effect Of Nano-tio 2 On the Morphology Of α-Al 2 O 3 Plateletsmentioning

confidence: 99%

“…Most studies have attempted morphological control of the platelets by adjusting the reaction conditions [20,25,[28][29][30] or alternating the starting materials [27,31]; seeds were added [20][21][22][23][24]32] and additives were used [19,20,27] during the synthesis in order to reduce the size and control the morphology, respectively, of the platelets.…”

Section: Introductionmentioning

confidence: 99%

“…Many studies have focused on the morphological control of the platelets and several methods, particularly molten salt synthesis [17][18][19][20][21][22][23][24][25][26][27], have been used to obtain various particles. Most studies have attempted morphological control of the platelets by adjusting the reaction conditions [20,25,[28][29][30] or alternating the starting materials [27,31]; seeds were added [20][21][22][23][24]32] and additives were used [19,20,27] during the synthesis in order to reduce the size and control the morphology, respectively, of the platelets.…”

Section: Introductionmentioning

confidence: 99%

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Effect of nano-TiO 2 and nano-SiO 2 addition on the morphological control of α-Al 2 O 3 platelets via solid-state reaction

Miao

Jiangong

Hao

et al. 2016

Ceramics International

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“…This synthesis is specifically based on a redox reaction between metal salts and reducing agents like glycine or urea [24] , successfully applied to the preparation of aluminum-based compounds such as alumina and other oxides [25,26] . It possesses specific advantages over the gas phase method, the sol gel method, the mechanical ball mill method, or the molten salt method [19,[27][28][29][30] . Its advantages lie in the occurrence of the reaction of the raw material in a solution so that the components can be uniformly mixed at molecular or ionic levels.…”

Section: Introductionmentioning

confidence: 99%

Solution-combustion Synthesized Nano-pellet α-Al2O3 and Catalytic Oxidation of Cyclohexane by Its Supported Cobalt Acetate

Kong

Liu

et al. 2021

J. Wuhan Univ. Technol.-Mat. Sci. Edit.

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Nano-pellet α-Al 2 O 3 was prepared using aluminum nitrate as precursor and urea as fuel by a fast method of solution combustion synthesis. The formation of the nano material was dependent on the molar ratio of fuel/oxidant, calcination temperature, and foreign metallic ions. The prerequisite conditions of the formation were a suitable fuel/oxidant molar ratio larger than two and calcination temperature higher than 673 K. Foreign ions, Ce 4+ or Co 2+ , hindered this formation via promoting the generation of stable penta-coordinated Al 3+ ions due to strong interaction with alumina, were revealed by 27 Al NMR spectra. Such Al 3+ ions were recognized as a critical intermediate state for the phase transformation of alumina and their presence deterred the transformation. The nano-pellet morphology of the product demonstrated a specific surface area of 69 m 2 /g, of which the external surface area occupied 59 m 2 /g. It was found that the supported cobalt acetate on such nanopellets existed as nanoparticles attached to the external surface, evidenced by the TEM characterization. The prepared catalyst could efficiently catalyze the selective oxidation of cyclohexane under the reaction condition of pressure under 0.8 MPa, temperature at 373 K, and time for 4 hours. The conversion of the reaction achieved up to 7.9%; while the cyclohexanone selectivity was 42.7% and the cyclohexanone and cyclohexanol selectivity was 91.6%. This catalytic performance recommends the supported cobalt acetate on the inert nano-pellet a-Al 2 O 3 as a promising catalyst for the selective oxidation of cyclohexane.

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Molten salt synthesis of α-Al2O3 platelets using NaAlO2 as raw material

Cited by 25 publications

References 10 publications

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Effect of nano-TiO 2 and nano-SiO 2 addition on the morphological control of α-Al 2 O 3 platelets via solid-state reaction

Solution-combustion Synthesized Nano-pellet α-Al2O3 and Catalytic Oxidation of Cyclohexane by Its Supported Cobalt Acetate

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