ISSN:
1573-4889
Keywords:
NITRIDATION
;
NIOBIUM
;
GROWTH MECHANISMS
;
PARABOLIC-TO-LINEAR KINETICS TRANSITION
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The nitridation behavior of pure niobium wasinvestigated in nitrogen gas over the pressure range of10-2 to 1 torr and over the temperature range1600-2000°C. A surface layer of Nb2Nformed at 1 and 10-1 torr, obeying parabolickinetics for the former and linear kinetics for thelatter. This transition in time dependency firstmanifested itself at 1 torr in nonlinear plots ofln(Kc) vs. 1/T, consistent with an adsorption-controlledreaction. An evaluation of the flux of nitrogen acrossthe gas-metal interface is presented, comparing thekinetics of gas arrival based on the kinetic theory of gases with gas removal because of inwarddiffusion into the metal. Data from the literature areused to estimate these adsorptive and diffusive fluxesand justify the observed behavior. Nitridation ofniobium at 10-2 torr resulted in gasdissolution only, with no nitride layer beingformed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1018879109285
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