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Title: Crystallographic Study of Product Phases of Carbothermic Reduction and Nitridation of Hafnium Dioxide
Details of the carbothermic reduction/nitridation to synthesize hafnium nitride (HfN) and hafnium carbide (HfC) are scarce in the literature. Therefore, this current study was carried out to evaluate two pathways for synthesizing these two refractory materials: direct nitridation and carbothermic reduction/nitridation. Two mixtures of hafnium dioxide and carbon with C/ HfO2 molar ratios of 2.15 and 3.1 were nitridized directly using flowing nitrogen gas at elevated temperatures (1300−1700 °C). The 3.1 C/HfO2 molar ratio mixture was also carbothermically reduced under flowing argon gas to synthesize HfC, which was converted into HfN by introducing a nitridation step under both N2(g) and N2(g)-10% H2(g). X-ray diffraction results showed the formation of HfN at 1300 and 1400 °C and HfC1−yNy at ≥1400 °C under direct nitridation of samples using a C/HfO2 molar ratio of 2.15. These phase analysis data together with lower lattice strain and greater crystallite sizes of HfC1−yNy that formed at higher temperatures suggested that the HfC1−yNy phase is preferred over HfN at those temperatures. Carbothermic reduction of 3.1 C/HfO2 molar ratio samples under an inert atmosphere produced single-phased HfC with no significant levels of dissolved oxygen. Carbothermic reduction nitridation made two phases of different carbon levels (HfC1−yNy and HfC1−y′Ny′, where y′ < y), while direct nitridation produced a single HfC1−yNy phase under both N2 and N2-10% H2 cover gas environments.  more » « less
Award ID(s):
2047084
PAR ID:
10509885
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
ACS Publications
Date Published:
Journal Name:
Inorganic Chemistry
Volume:
62
Issue:
30
ISSN:
0020-1669
Page Range / eLocation ID:
11910 to 11919
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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