Deep metastable eutectic condensation in Al-Fe-SiO-H2-O2 vapors: Implications for natural Fe-aluminosilicates

Rietmeijer, Frans J. M.; Nuth, Joseph A.; Rochette, P.; Marfaing, J.; Pun, A.; Karner, J. M.

doi:10.2138/am.2006.2102

Cited by 18 publications

(15 citation statements)

References 49 publications

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“…Although we do not expect all magnesiosilica samples 1-4 to have exactly the same fluffiness, we will use their estimated fluffiness as a qualitative reference at this time. In the condensing Fe-SiO-H 2 -O 2 vapors, also rich in SiO and Si 2 O 3 vapor molecules, iron oxidation results in variable Fe 2+ /Fe 3+ ratios of the mixed ferrosilica grains (Rietmeijer et al 2006). We conjecture that the variable Fe 2+ /Fe 3+ ratios contributed to the lining-up of the nanograins in isolated narrow strands in favor of forming denser structures.…”

Section: Aggregate Fluffinessmentioning

confidence: 86%

“…Compositionally the Al-O grains were stoichiometric Al 2 O 3 but statistically significant deviations of oxygen deficiency occur that tend to be correlated with a developing vesicular structure. Al-oxide grains condensed in Fe-Al-SiO-H 2 -O 2 vapors showed similar loose structures (Rietmeijer et al 2006). Gel-produced amorphous Al 2 O 3 showed a loose structure but, in this case, the structure was probably filled with liquid water (Begemann et al 1997).…”

Section: Alumina Aggregatesmentioning

confidence: 94%

“…The iron oxide forms (sub)spherical, single-crystal magnetite and maghémite; both Fe 2 O 3 polymorphs (Rietmeijer et al 2006). The invariably crystalline MgO and Fe 2 O 3 condensates occur as individual grains or as compact clusters of several MgO or Fe 2 O 3 grains interspersed throughout an aggregate sample.…”

Section: Amorphous Silicate Aggregatesmentioning

confidence: 99%

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Experimental light scattering by fluffy aggregates of magnesiosilica, ferrosilica, and alumina cosmic dust analogs

Volten

Muñoz

Hovenier

et al. 2007

A&A

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Context. Fluffy aggregates are generally assumed to be important constituents of circumstellar and interplanetary environments as well as to be present among the solid debris ejected from active comets. Aims. We experimentally study light scattering properties of several fluffy aggregate samples. These cosmic dust analog aggregates are composed of coagulated magnesiosilica grains, ferrosilica grains, and alumina grains. The samples contain aggregates with different porosities. The individual grains have diameters of the order of a few tens of nanometers; the aggregates have diameters up to several micrometers. Methods. The samples were produced in a Condensation Flow Apparatus. Their light scattering properties were measured with the Amsterdam Light Scattering Facility at a wavelength of 632.8 nm.Results. We measured two scattering matrix elements as functions of the scattering angle, namely F 11 (θ) (phase function) and −F 12 (θ)/F 11 (θ) (degree of linear polarization for incident unpolarized light) for seven different samples of aggregates in random orientations in an aerosol jet. The samples consisted of fluffy aggregates with cosmic dust analog compositions. We provide detailed information about their production and nature. In addition, for four of these samples we measured F 22 (θ)/F 11 (θ). We covered an angle range of 5• to 174• , in small steps of 1 • in the range from 5• to 10• and 170• to 174• and in steps of 5• for the rest of the angle range. Conclusions. The results for the analog samples show an extremely high −F 12 (θ)/F 11 (θ), with maxima between about 60% to almost 100%. This Rayleigh-like behavior has been demonstrated before for fluffy aggregates and suggests that the small-sized grains in the aggregates are the main cause. Measured results for phase functions are more scarce. The phase functions we measured show shapes that are similar to those of compact micron-sized particles, suggesting that it is the overall size of the aggregates that determines their shape. The modest negative branch of −F 12 (θ)/F 11 (θ) found for all seven samples seems to be mainly governed by aggregate structure. Thus, the unique combination of accurately measured phase functions and polarization functions over a fine mesh of scattering angles for cosmic dust analog aggregates enables the exploitation of the data as powerful diagnostic tools to constrain the different physical properties of dust in e.g. circumstellar clouds and in comet ejecta.

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Section: Aggregate Fluffinessmentioning

confidence: 86%

Section: Alumina Aggregatesmentioning

confidence: 94%

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Experimental light scattering by fluffy aggregates of magnesiosilica, ferrosilica, and alumina cosmic dust analogs

Volten

Muñoz

Hovenier

et al. 2007

A&A

Self Cite

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“…It follows that natural condensation will produce simple stoichiometric oxide nanograins and amorphous non-stoichiometric mixed silicate nanograins. Larger, chemically complex amorphous grains will be the result of agglomeration and fusion of DME condensate grains (Rietmeijer et al, 2006). Experimental verification of natural mineral-forming processes can be a very powerful tool to elucidate the processes in natural environments that are inaccessible to direct sampling or wherein the processes occur over long time scales .…”

Section: Introductionmentioning

confidence: 99%

“…(1) Smectite dehydroxylate: (Nuth et al, 1999(Nuth et al, , 2000b(Nuth et al, , 2000cRietmeijer et al, 1999aRietmeijer et al, , 1999bRietmeijer et al, , 2002aRietmeijer et al, , 2006. The names for the solids (1) and (2) refer to M/Si ratios that are those of smectite and serpentine layer silicate minerals, respectively, but with the structural layer silicate (OH) − groups replaced by O 2− .…”

Section: Introductionmentioning

confidence: 99%