Local, nano- and micro-structures of mixed metal oxide aerogels for catalyst applications

Hair, L.M.; Owens, L.; Tillotson, Thomas M.; Fröba, Michael; Wong, Joe; Thomas, George J.; Medlin, Douglas L.

doi:10.1016/0022-3093(95)00034-8

Cited by 19 publications

(6 citation statements)

References 5 publications

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“…Applications for high-resolution imaging, frequently referred to as HRTEM, range from determining whether there is local crystallinity in an otherwise amorphous sample, to characterizing the structural relationships between phases in composite aerogel materials, to distinguishing between crystalline materials with similar diffraction patterns. For example, Schneider et al [10] used HRTEM to determine that the particles of a vanadiatitania aerogel were single crystals of the anatase crystal structure; Long and coworkers used HRTEM to identify the structures a variety of nanocrystalline manganese oxide aerogels [11][12][13]; Hair et al tracked the alteration of vanadium-silica composite aerogels to nanocrystalline vanadium oxide-silica composites [14]; and Maldonado-Hodár et al examined the differences in graphitization of carbon aerogels catalyzed with various metal nanoparticles [15].…”

Section: High-resolution Imagingmentioning

confidence: 99%

A practical guide to transmission electron microscopy of aerogels

Stroud¹,

Long²,

Pietron³

et al. 2004

Journal of Non-Crystalline Solids

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Section: High-resolution Imagingmentioning

confidence: 99%

A practical guide to transmission electron microscopy of aerogels

Stroud¹,

Long²,

Pietron³

et al. 2004

Journal of Non-Crystalline Solids

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“…Aerogels have porosities up to 99.8% and a large surface area of 500-1200 m 2 g À1 made by supercritical drying method [3]. Such a large specific surface area offered by the aerogel matrix can be used to host finely dispersed metallic particles [4], which enables increased number of active sites per gram of the material. The cost involved in supercritical drying is a disadvantage and to circumvent this drawback, other alternate ambient pressure drying processes have been developed [5].…”

Section: Introductionmentioning

confidence: 99%

Silver Nanoparticles in Mesoporous Aerogel Exhibiting Selective Catalytic Oxidation of Benzene in CO2 Free Air

2007

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The present article reports the synthesis of silver nanoparticles in silica aerogel matrix by sub-critical drying technique. The catalytic performance of these nanocomposites was evaluated for the selective oxidation of benzene. Silica aerogel with 1, 5, 10 and 25 wt.% of silver was prepared and characterized for their physicochemical characteristics. The catalytic performance of these samples was evaluated as a function of silver particle size crystallized within the aerogel matrix. The sample with the silver concentration of 1 wt.% showed high selectivity among the tested samples. With increasing silver particle size, the % conversion increased with a decreased selectivity, which is attributed to the particle size effect on the catalytic oxidation of benzene.

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“…Designing new and improved silica aerogel particles has many potential applications, such as catalyst matrixes, chromatography resins, and precursors for ceramic powders for biomaterials. − An aerogel is a gel that has a lower density than the fully condensed form of the material forming it. Aerogels are typically produced by replacing the liquid of a gel by air or another gas without allowing complete collapse of the structure .…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Formation of Silica Aerogel Particles By a Novel Sol−Gel Route in Supercritical Carbon Dioxide

2004

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A new method to obtain silica aerogel particles using acetic acid as the condensation agent for silicon alkoxides in supercritical carbon dioxide (scCO 2 ) is proposed. The objective of this study was to determine the mechanism of silica aerogel formation in scCO 2 using in situ analysis techniques. The synthesis and formation of silica aerogel particles was carried out by a modified sol-gel route, based on the hydroxylation and condensation of silicon alkoxides in scCO 2 ; both submicron and micron-size aerogel spheres were obtained. By means of in situ Fourier Transform infrared spectroscopy (FTIR), the activity of acetic, formic, benzoic, and chloroacetic acids were studied for the condensation of tetraethyl orthosilicate (TEOS). Formic and acetic acid gave slower rates than benzoic and chloroacetic acids. Increasing the concentration of acid and addition of extra water led to an acceleration of the reaction. The reactions were also studied as a function of temperature and pressure. Higher rates of reaction were obtained at higher temperatures and lower pressures. Results from particle formation studies indicated that by slowing the rate of reaction, precipitation and agglomeration of particles could be minimized. A submicron particle size range was obtained by depressurization of the sol-gel solution inside the reaction vessel, while the rapid expansion of supercritical solutions (RESS) process was found to yield particles in the size range of approximately 100 nm.

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Local, nano- and micro-structures of mixed metal oxide aerogels for catalyst applications

Cited by 19 publications

References 5 publications

A practical guide to transmission electron microscopy of aerogels

A practical guide to transmission electron microscopy of aerogels

Silver Nanoparticles in Mesoporous Aerogel Exhibiting Selective Catalytic Oxidation of Benzene in CO2 Free Air

Synthesis and Formation of Silica Aerogel Particles By a Novel Sol−Gel Route in Supercritical Carbon Dioxide

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