A practical guide to transmission electron microscopy of aerogels

Stroud, Rhonda M.; Long, Jeffrey W.; Pietron, Jeremy J.; Rolison, Debra R.

doi:10.1016/j.jnoncrysol.2004.05.013

Cited by 23 publications

(14 citation statements)

References 24 publications

(23 reference statements)

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“…41 the samples are still highly porous, in accordance with physisorption data. TEM dark images allow us to determine the distribution of the nanoparticles which appear as bright spots inside the matrix, which appears dark and without contrast.…”

Section: Catalysts Characterizationsupporting

confidence: 81%

Catalytic Chemical Vapour Deposition on MFe2O4–SiO2 (M = Co, Mn, Ni) Nanocomposite Aerogel Catalysts for the Production of Multi Walled Carbon Nanotubes

Loche

Casula

Corrias

et al. 2016

j nanosci nanotechnol

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Highly porous MFe 2 O 4 -SiO 2 (M = Co, Mn, Ni) nanocomposite aerogels were tested for the first time as catalysts for multi walled carbon nanotubes production by Catalytic Chemical Vapour Deposition. Structural and textural characterization points out that the catalysts are made out of nanocomposites where nanocrystalline ferrite phases with controlled composition and size in the range 9-13 nm are finely dispersed into the highly porous silica support. Remarkably, CoFe 2 O 4 -SiO 2 and MnFe 2 O 4 -SiO 2 catalysts have shown poor catalytic activity, whereas NiFe 2 O 4 -SiO 2 catalyst has given rise to good quality nanotubes with high yields at deposition temperatures in the range 500-650 C. The different catalytic behaviour of the mixed ferrite-silica aerogels as a function of the bivalent metal (M = Co, Mn, Ni) can been ascribed to how easily the nanophase can be reduced. In particular, it was demonstrated that the most active NiFe 2 O 4 nanoparticles undergo an in-situ reduction process during the Catalytic Chemical Vapour Deposition reaction, forming a NiFe alloy phase that is responsible for promoting the multi walled carbon nanotubes growth.

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Section: Catalysts Characterizationsupporting

confidence: 81%

Catalytic Chemical Vapour Deposition on MFe2O4–SiO2 (M = Co, Mn, Ni) Nanocomposite Aerogel Catalysts for the Production of Multi Walled Carbon Nanotubes

Loche

Casula

Corrias

et al. 2016

j nanosci nanotechnol

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“…1993). However, identification and characterization of silica aerogel is relatively straightforward with TEM (Stroud et al. 2004).…”

Section: Resultsmentioning

confidence: 99%

Correlated microanalysis of cometary organic grains returned by Stardust

Gregorio

Stroud

Cody

et al. 2011

Meteorit & Planetary Scien

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Abstract-Carbonaceous matter in Stardust samples returned from comet 81P ⁄ Wild 2 is observed to contain a wide variety of organic functional chemistry. However, some of this chemical variety may be due to contamination or alteration during particle capture in aerogel. We investigated six carbonaceous Stardust samples that had been previously analyzed and six new samples from Stardust Track 80 using correlated transmission electron microscopy (TEM), X-ray absorption near-edge structure spectroscopy (XANES), and secondary ion mass spectroscopy (SIMS). TEM revealed that samples from Track 35 containing abundant aliphatic XANES signatures were predominantly composed of cometary organic matter infilling densified silica aerogel. Aliphatic organic matter from Track 16 was also observed to be soluble in the epoxy embedding medium. The nitrogen-rich samples in this study (from Track 22 and Track 80) both contained metal oxide nanoparticles, and are likely contaminants. Only two types of cometary organic matter appear to be relatively unaltered during particle capture. These are (1) polyaromatic carbonyl-containing organic matter, similar to that observed in insoluble organic matter (IOM) from primitive meteorites, interplanetary dust particles (IDPs), and in other carbonaceous Stardust samples, and (2) highly aromatic refractory organic matter, which primarily constitutes nanoglobule-like features. Anomalous isotopic compositions in some of these samples also confirm their cometary heritage. There also appears to be a significant labile aliphatic component of Wild 2 organic matter, but this material could not be clearly distinguished from carbonaceous contaminants known to be present in the Stardust aerogel collector.

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“…3 and 4). Aerogel is easily recognizable by the high number of nanopores, giving it a sponge-like microstructure (e.g., Stroud et al 2004;Shi et al 2006). Aerogel is present along the periphery of most of the samples where it was densified during the hypervelocity impact capture process.…”

Section: General Description Of the Samplesmentioning

confidence: 99%

A TEM study of thermally modified comet 81P/Wild 2 dust particles by interactions with the aerogel matrix during the Stardust capture process

Leroux¹,

Rietmeijer²,

Velbel³

et al. 2008

Meteorit & Planetary Scien

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204

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Abstract-We report the results of high-resolution, analytical and scanning transmission electron microscopy (STEM), including intensive element mapping, of severely thermally modified dust from comet 81P/Wild 2 caught in the silica aerogel capture cells of the Stardust mission. Thermal interactions during capture caused widespread melting of cometary silicates, Fe-Ni-S phases, and the aerogel. The characteristic assemblage of thermally modified material consists of a vesicular, silicarich glass matrix with abundant Fe-Ni-S droplets, the latter of which exhibit a distinct core-mantle structure with a metallic Fe,Ni core and a iron-sulfide rim. Within the glassy matrix, the elemental distribution is highly heterogeneous. Localized amorphous "dust-rich" patches contain Mg, Al, and Ca in higher abundances and suggest incomplete mixing of silicate progenitors with molten aerogel. In some cases, the element distribution within these patches seems to depict the outlines of ghost mineral assemblages, allowing the reconstruction of the original mineralogy. A few crystalline silicates survived with alteration limited to the grain rims. The Fe-and CI-normalized bulk composition derived from several sections show CI-chondrite relative abundances for Mg, Al, S, Ca, Cr, Mn, Fe, and Ni. The data indicate a 5 to 15% admixture of fine-grained chondritic comet dust with the silica glass matrix. These strongly thermally modified samples could have originated from a finegrained primitive material, loosely bound Wild 2 dust aggregates, which were heated and melted more efficiently than the relatively coarse-grained material of the crystalline particles found elsewhere in many of the same Stardust aerogel tracks (Zolensky et al. 2006).

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A practical guide to transmission electron microscopy of aerogels

Cited by 23 publications

References 24 publications

Catalytic Chemical Vapour Deposition on MFe<SUB>2</SUB>O<SUB>4</SUB>–SiO<SUB>2</SUB> (M = Co, Mn, Ni) Nanocomposite Aerogel Catalysts for the Production of Multi Walled Carbon Nanotubes

Catalytic Chemical Vapour Deposition on MFe<SUB>2</SUB>O<SUB>4</SUB>–SiO<SUB>2</SUB> (M = Co, Mn, Ni) Nanocomposite Aerogel Catalysts for the Production of Multi Walled Carbon Nanotubes

Correlated microanalysis of cometary organic grains returned by Stardust

A TEM study of thermally modified comet 81P/Wild 2 dust particles by interactions with the aerogel matrix during the Stardust capture process

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