Other
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p11a1581w&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P11A-1581
Other
[6015] Planetary Sciences: Comets And Small Bodies / Dust
Scientific paper
Amorphous and crystalline dust particles are smallest components of accretionary processes within circumstellar disks. The transition characteristics of amorphous dust to crystalline particles highly influence the thermal structure of the circumstellar disk and therefore affect most other processes. Annealing experiments on different compositions on the MgO-SiO2 join yielded quite contrasting results on the crystallization kinetics of enstatite (Mg2SiO3) and forsterite (Mg2SiO4) (e.g. review of Wooden et al., 2005; Murata et al., 2009; Roskosz et al., 2009). The discrepancies may result from differences in the starting materials. To explore this factor, we have setup several experimental series, using different methods to prepare sol-gels on a variety of Mg/Si ratios. We have also tested different procedures to process the raw gel materials after precipitation. The final gels were annealed in a furnace at temperatures between 700 and 1500 °C for durations between 15min and 96h. MIR and FIR-spectroscopy, x-ray diffraction, BSE imaging and EDX analyses were used to characterize the run products. On enstatite composition the 1500 °C run products consist of well crystallized enstatite polymorphs with very little forsterite. Products of runs between 700 and 800 °C contain both poorly crystallized phases and amorphous material. Between 800 and 780 °C at all run durations crystalline products are dominated by enstatite and show less forsterite. Run products at 750 °C change with run time from amorphous, to forsterite dominated and finally to enstatite dominated mixtures, the latter containing subordinated forsterite. At 700 °C amorphous run products are observed after short run times, but change to forsterite dominated mixtures after longer run times. Up to 24 hours no enstatite could be observed in the products at 700 °C. Preliminary results with the SEM reveal compositional heterogeneities after short run durations (up to 30 minutes), which reflect the formation of crystalline forsterite. On the Mg2SiO4 composition, heat treatment for 20 hours at temperatures as low as 450 °C already leads to the crystallization of forsterite. Our experimental results are partially in accord with the findings of Thompson et al. (2003) and Roskosz et al. (2009). They are, however, at odds with the observations of Murata et al. (2009) on composition 1.00 MgO * 1.07 SiO2, who record enstatite as the first crystalline phase at temperatures in the range 750-780°C. Further investigations are in progress to try to resolve these discrepancies.
Burchard Michael
Lattard Dominique
Willenweber A.
No associations
LandOfFree
Laboratory simulations of thermal annealing in proto-planetary discs - I. Crystallization of Mg silicates from sol gels does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Laboratory simulations of thermal annealing in proto-planetary discs - I. Crystallization of Mg silicates from sol gels, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laboratory simulations of thermal annealing in proto-planetary discs - I. Crystallization of Mg silicates from sol gels will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-867435