Ultrafine alumina powders via a sol-emulsion-gel method

Ponthieu, Eric; Payen, Edmond; Grimblot, J.

doi:10.1016/s0022-3093(05)80684-2

Cited by 27 publications

(5 citation statements)

References 5 publications

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“…Introduction. The phase transformation of θ- to α-Al 2 O 3 is considered to occur through a nucleation and growth process. − Investigations on the critical crystallite sizes of transformation have been reported previously (Table ), − although there is substantial discrepancy among them. Recent studies , on the nanosized alumina powder have found that during the transformation process there can be a critical size for θ-Al 2 O 3 at the nucleation stage, which initiates the formation of the α-Al 2 O 3 nucleus, and a primary size for the formed α-Al 2 O 3 at the growth stage, beyond which the transformation comes to a completion.…”

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confidence: 99%

Examinations on the Critical and Primary Crystallite Sizes during θ- to α-Phase Transformation of Ultrafine Alumina Powders

et al. 2001

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Examination on the existence of the critical and primary crystallite size (d c r ∼ 17 nm and d p ) 50−55 nm) phenomena during θ-to r-phase transformation of the nanosized Al 2 O 3 powder was designed and conducted using two θ-Al 2 O 3 powders of different crystallite sizes. Due to the critical size, the size dependence of the transformation temperature, the rate of transformation, and the inevitable presence of residual θ-phase in the thermal-treated and re-treated "100%-transformed" sample can be expected. Due to the two characteristic sizes and the formation of primary crystallites by the coalescence growth of the critical crystallites, the variation in mean r-size during the transformation can be predicted by means of the difference in the growth rate of the two θ-powder (different crystallite sizes) systems associated with proper thermal treatment techniques. Further, it is important to note that the presence of primary crystallites at various thermal-treated samples becomes possible.

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confidence: 99%

Examinations on the Critical and Primary Crystallite Sizes during θ- to α-Phase Transformation of Ultrafine Alumina Powders

et al. 2001

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“…The sol-emulsion-gel process (6,(16)(17)(18)(19) was used to produce particles with cellular structure that are referred to as microspheres in this work. Batch polymerizations were carried out in a double-wall round-bottom reactor equipped with a temperature controller.…”

Section: Methodsmentioning

confidence: 99%

Morphology and Surface Area of Cellular Structured Resorcinol/Formaldehyde Microspheres: Effect of Ageing Conditions

Lee

et al. 2001

Cellular Polymers

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Cellular structured resorcinol/formaldehyde (R/F) microspheres were synthesized via the sol-emulsion-gel reaction and followed by supercritical drying with CO2. The materials were characterized by thermogravimetry, FT-IR spectroscopy, nitrogen physisorption technique and scanning electron microscopy. Variation of ageing conditions leaded to different micro and macro-structure, which affected bulk density, pore size distribution, specific surface area, and morphology of cellular structured R/F microspheres. The resultant R/F microspheres have average pore sizes in the range of less than 100 nm. Increasing the ageing time leaded to decreased surface area of cellular structured R/F microspheres. As the ageing temperature increased, the bulk density increased and the surface area decreased. The pore morphology depended on the ageing temperature and it was evidenced by nitrogen physisorption experiments.

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“…Nano-KF/Al 2 O 3 was prepared as reported [24] using potassium fluoride and nano-Al 2 O 3 [25] which was synthesized by supersonic wave catalysis using aluminium isopropoxide and distilled water. Diethyl malonate 40 mmol was taken in a 50 ml round bottom flask and to it was added nano-KF/Al 2 O 3 5 g (3 mmol F -) and IL 15 ml.…”

Section: Typical Procedures Of Michael Additions Mediated By Nano-kf/amentioning

confidence: 99%

Synthesis of Eco-Friendly Ionic Liquids by Microwave Irradiation and Their Applications in Michael Addition

Zhao

Bao

2009

2009 3rd International Conference on Bioinformatics and Biomedical Engineering

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A mild, efficient and eco-friendly procedure for the synthesis of novel ionic liquids (ILs) with formula (C 4 H 9 ) 4 NX-nC 6 H 11 NO (X=Cl -, Brand Ac -, n=2-3) under microwave irradiation and solventless conditions has been investigated. The materials have been characterized by IR, 1 H NMR methods. The properties of this kind of ILs have been researched including the melting point, the viscosity, the solubility, the pH value and the conductivity. Further, these ILs have been exploited for the synthesis of Michael addition using nano-KF/Al 2 O 3 as catalyze in short duration of time with quantitative yields, for the first time. Keywords-ionic liquids; caprolactam; quaternary ammonium salts; microwave irradiation; Michael addition; nano-KF/Al 2 O 3978-1-4244-2902-8/09/$25.00 ©2009 IEEE

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Ultrafine alumina powders via a sol-emulsion-gel method

Cited by 27 publications

References 5 publications

Examinations on the Critical and Primary Crystallite Sizes during θ- to α-Phase Transformation of Ultrafine Alumina Powders

Examinations on the Critical and Primary Crystallite Sizes during θ- to α-Phase Transformation of Ultrafine Alumina Powders

Morphology and Surface Area of Cellular Structured Resorcinol/Formaldehyde Microspheres: Effect of Ageing Conditions

Synthesis of Eco-Friendly Ionic Liquids by Microwave Irradiation and Their Applications in Michael Addition

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