P. Fraundorf
We sometimes refer to this as our "carbon-rain" project, because we are looking at the formation of unlayered-graphene composite during the solidification of super-cooled carbon droplets in "containerless" or free-fall settings.
This provides the first experimental window on liquid carbon at low pressures, provides insight into the cooling conditions of particles ejected by radiation pressure from carbon stars, and suggests a class of diffusion barriers that we are only beginning to explore.
Laboratory work on circumstellar dust in our solar system (hence interplanetary) began with the stratospheric collections of Don Brownlee at U. Washington in Seattle, followed on by our work in Bob Walker's group at Washington U. in StL. Laboratory work on circumstellar dust from other star systems began with meteorite dissolution and noble gas mass spectroscopy of the Anders/Lewis cosmochemistry group at U. Chicago, followed on again by our nanoSIMS and electron microscopy work in Saint Louis. More recently, collaborators in laboratory and modeling work at UM-StL have included Melanie Lipp, Tristan Hundley, Chathuri Silva, Phil Chrostoski, and Ryan Molitor.
There are now many reasons for the meteoritics community to expand work on characterizing micron-size presolar core\rim carbon spheres from AGB star environs.
We report high resolution TEM & diffraction studies from diamond & silicon carbide in dissolution residues from primitive meteorites (Allende & Murray).
A first laboratory look at interplanetary dust particles, many of which are likely of cometary origin.
Transmission electron microscopy of interplanetary dust collected in the earth's stratosphere provides our first data on their solar flare track exposure.
We offer a simple model for the statistics of heating of 10 µm micrometeorites decelerated in the earth's atmosphere without melting.
Isotopically anomalous particles extracted from primitive meteorites here on earth tell stories of their interstellar adventures. Vivian is an example.
Analytical models for 2D reaction-limited nucleation and growth are used generate analytical models to compare with presolar & lab-grown data.
Density functional theory simulations of a carbon liquid support experimental evidence of pent-first nucleatio of unlayered graphene sheets on solidification.
We compare cooling rates for micron-size carbon spheres ejected by radiation pressure from late-stage AGB stars, to laboratory cooling rates examined so far.
Here we review developments so far in study of unlayered graphene composite formation in the core of presolar micron-size carbon spheres from AGB stars.
Here we report some of the 1st experimental evidence for laboratory synthesis of unlayered graphene composite by the slow-cooling of evaporated carbon vapor.
Debye pattern analysis of faceted graphene pentacones predicts satellite peaks in powder diffraction profiles that might be detectable.
Pulse heating experiments on magnesium-rich olivine and pyroxene show that iron ion tracks remain detectable in the TEM for temperatures up to ~600 deg C.
Examination of 526 particles in the 2–50 μm size range obtained from stratospheric impaction collectors has shown that most of them fit into one of three groups
Nanogram sized particles collected by U2 aircraft in the earth's stratosphere show chondritic features suggesting an extraterrestrial origin.
This study is companion to new experimental work on carbon vapor slow-cooled in (a) the laboratory and (b) the atmosphere of ancint carbon-synthesizing stars.
We show here how analytical models of reaction limited nucleation and growth can be used to connect thermal history to electron microscope observations.
Here we report on laboratory synthesis of sub-micron core\rim carbon spheres in an evaporating carbon oven, like those found in presolar collections.
This is followup for a NASA/MO spacegrant project with Tim Volkert back in 2006, about "tales told" by a red-giant starsmoke sphere formed long ago and far away
The travel of carbon atoms from an AGB star's core, ejection into the interstellar medium, collapse of our solar nebula, parent body breakup, & study on earth.
HAADF (yellow)/BF(blue) image taken with Steve Pennycook's 300keV aberration-corrected Vacuum Generators STEM at ORNL for Eric Mandell's dissertation work.
Getting a micron-size interstellar traveler in labs here on earth to tell her story might help connect young & old scientific detectives to emergent methods.
