Mass spectrometric study of the stabilities of gaseous carbides of vanadium, niobium, and molybdenum

Journal Article · Sun Mar 15 04:00:00 EST 1981 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.441463· OSTI ID:6798989

Gupta, S K; Gingerich, K A

The gaseous molecules VC, NbC, NbC/sub 2/, MoC, and MoC/sub 2/ have been identified in a mass spectrometric study of the Knudsen effusate from the niobium--graphite and vanadium--niobium--molybdenum--graphite systems at high temperatures. Third-law enthalpies of the various reactions involving these species were determined from the experimental equilibrium measurements and estimated thermodynamic functions. The reaction enthalpies in conjunction with published thermodynamic data yielded the thermochemical values (kJ mol/sup -1/, kcal mol/sup -1/): D/sup 0//sub 0/(VC)=419 +- 24, 101.1 +- 5.7; ..delta..H/sup 0//sub at,0/(VC/sub 2/)=1178 +- 17, 281.1 +- 4.1; D/sup 0//sub 0/(NbC)=564 +- 13, 134.8 +- 3.1; ..delta..H/sup 0//sub at,0/(NbC/sub 2/)= 1257 +- 13, 300.4 +- 3.1; D/sup 0//sub 0/(MoC)=478 +- 16, 114.2 +- 3.8; and ..delta..H/sup 0//sub at,0/(MoC/sub 2/)=1101 +- 20, 263.1 +- 4.8. In addition, the bond energies D/sup 0//sub 0/(V--C/sub 2/)=572 +- 19 kJ mol/sup -1/, or 136.6 +- 4.6 kcal mol/sup -1/; D/sup 0//sub 0/(Nb--C/sub 2/)=650 +- 16 kJ mol/sup -1/, or 155.4 +- 3.8 kcal mol/sup -1/; and D/sup 0//sub 0/(Mo--C/sub 2/)=494 +- 22 kJ mol/sup -1/, or 118.1 +- 5.4 kcal mol/sup -1/ were also calculated. The results are discussed in relation to the stabilities of previously known gaseous mono- and dicarbides of transition metal.

• Research Organization: Department of Chemistry, Texas AandM University, College Station, Texas 77843
• OSTI ID: 6798989
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 74:6; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
CARBIDES
CARBON COMPOUNDS
DISSOCIATION HEAT
ENTHALPY
FORMATION HEAT
HIGH TEMPERATURE
MASS SPECTROSCOPY
MOLYBDENUM CARBIDES
MOLYBDENUM COMPOUNDS
NIOBIUM CARBIDES
NIOBIUM COMPOUNDS
PHYSICAL PROPERTIES
REACTION HEAT
SPECTROSCOPY
STABILITY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
VANADIUM CARBIDES
VANADIUM COMPOUNDS