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Title: Electric field effect on chemical and phase equilibria in nano-TiB 2–TiO 2–TiBO 3 system at <650 °C: an in situ time-resolved energy dispersive x-ray diffraction study with an ultrahigh energy synchrotron probe

Nano-TiB 2 powder of 58 nm size with TiO 2 and TiBO 3 as secondary phases was heated with 20 °C to <650 °C in argon while applying an electric field. The powder became conductive at 520 and 305 °C (T onset) for 16 and 40 V/cm, respectively, at which point current bursts of 4.5 and 10.0 A (peak value) were observed. Current bursts were accompanied by >1% TiB 2 unit cell expansion, exceeding zero field thermally induced expansion. The current bursts also induced nonisothermal reaction between TiB 2 and TiO 2, yielding TiBO 3 that is absent with no field. Increase from 16 to 40 V/cm shifts the TiB 2 → TiBO 3 reaction forward, decreases T onset but increases reaction rate. Analysis using Van’t Hoff relation, including electrochemical effects, precluded possibility of appreciable Joule heating, which was supported with adiabatic internal temperature calculations. In conclusion, the observed low temperature oxidation of TiB 2 to TiBO 3 that is electrochemically driven and is mediated by the TiO 2 solid electrolyte.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [1]
  1. Rutgers Univ., Piscataway, NJ (United States). Dept. of Materials Science and Engineering
  2. Selcuk Univ., Konya (Turkey). Metallurgical and Materials Engineering Dept.
  3. Dulumpınar Univ., Kutahya (Turkey). Dept. of Materials Science and Engineering
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
Publication Date:
Report Number(s):
BNL-114453-2017-JA
Journal ID: ISSN 0884-2914; applab; TRN: US1800588
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
Journal of Materials Research
Additional Journal Information:
Journal Volume: 32; Journal Issue: 02; Journal ID: ISSN 0884-2914
Publisher:
Materials Research Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; sintering; oxidation; phase transformation
OSTI Identifier:
1413927