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Title: Phase Formation of a C6 Niobium Hemicarbide from Sub-stoichiometric NbC
The niobium hemicarbide (Nb2C) has at least three known polymorphs: a (Pnma or Pbcn), b (P31mÞ, and c (P63/mmc) as a function of temperature. Identification of these phases has been notoriously difficult particularly for the lower-temperature variations (a and b) because of their long-range vacancy ordering. In the current study, an overall Nb2C composition has been processed by hot isostatically pressing NbC and Nb powders together which did not fully homogenize. Using neutron diffraction and selected area electron diffraction, the C6 (P3m1) structure was identified in the Nb2C. The formation pathway for this phase is postulated from the high density of stacking faults observed in the NbC.  more » « less
Award ID(s):
2026760 2026766
PAR ID:
10524211
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Springer
Date Published:
Journal Name:
JOM
Volume:
75
Issue:
11
ISSN:
1047-4838
Page Range / eLocation ID:
4626 to 4635
Subject(s) / Keyword(s):
UHTC, Nb2C, vacancy ordering
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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