Newly-discovered presolar grain phases

TiC/iron grains -- Epitaxial growth of iron grains on TiCs

 A new type of presolar grain, namely titanium carbide/iron composite grains, was recently discovered (in 4 different SN graphites). These composite grains consist of a TiC with an iron-nickel grain (either BCC kamacite or FCC taenite) epitaxially grown onto one of the TiC faces. The diffraction patterns next to the images can be used to determine the crystal structure of both phases (TiC and iron) and to see exactly how one grows on the other.

TiCs with attached kamacite grains and selected area diffraction (SAD) patterns showing spots from each phase.

TiC with 2 attached taenite (3.65Å FCC) grains with composition Fe45Ni55. Microdiffraction patterns of the FCC taenite (top) and FCC TiC (bottom) at the same orientation show the alignment of a (200)TiC plane with a (111) taenite plane (4.4° misalignment and 4.1% lattice mismatch).

Detour:  Epitaxial growth: how do these phases grow on each other?

 Ruthenium-iron metal grains

Here’s something you won’t find laying around in the garage. Actually such ruthenium-iron metal grains do not occur naturally anywhere on the planet.

Ruthenium iron metal grains, with composition RuxFe1-x (66<x<77) and traces of Ti,Ca,Cr

Return  to Gallery of presolar grains.

My brain is very large and has complex folds ... take me straight to

your paper on supernova graphites in Geochim. Cosmochim. Acta.

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Take a detour

How are isotopic anomalies created?

What is a transmission electron microscope (TEM)?

What is the NanoSIMS?

How does secondary ion mass spectrometry (SIMS) work?

Pictures of presolar grains.

Washington University presolar grains site