Oxide thermal desorption from the LaB[sub 6](100) surface following reaction wih O[sub 2]
- Univ. of Illinois, Chicago, IL (United States)
The author's have used temperature-programmed desorption (TPD) to study the oxidation of the LaB[sub 6](100) surface by O[sub 2]. The authors find that the surface oxide is removed through the desorption of BO and LaO between 1300 and 1500 K and the desorption of B[sub 2]O[sub 2] between 1100 and 1500 K. The desorption of each of the three oxides shows a distinctly different dependence on O[sub 2] exposure. For all but the lowest coverages, LaO desorption follows zero-order desorption kinetics with an activation energy of 775 kJ/mol. At the highest oxide coverages, B[sub 2]O[sub 2] follows first-order kinetics with a constant desorption peak temperature of 1170 K. The first-order rate constant corresponding to this B[sub 2]O[sub 2] peak is (1.3 [times] 10[sup 9] s[sup [minus]1]) exp[[minus](233 kJ/mol)/RT]. Similarly, a first-order desorption peak for BO at 1485-1500 K has a first-order rate constant of (6.3 [times] 10[sup 9] s[sup [minus]1]) exp[[minus](303 kJ/mol)/RT]. The results are discussed in terms of various surface reactions involving B[sub 2]O[sub 3] and La[sub 2]O[sub 3]. 56 refs., 9 figs.
- OSTI ID:
- 5046874
- Journal Information:
- Chemistry of Materials; (United States), Journal Name: Chemistry of Materials; (United States) Vol. 5:12; ISSN CMATEX; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
Similar Records
Temperature-dependent rate constants for the reactions of gas-phase lanthanides with O{sub 2}
Structure and reactivity of LaB[sub 6](100)
Related Subjects
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ACTIVATION ENERGY
BORIDES
BORON COMPOUNDS
BORON OXIDES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DESORPTION
ENERGY
KINETICS
LANTHANUM BORIDES
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MILLER INDICES
OXIDATION
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
REACTION KINETICS
SORPTION
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 1000-4000 K