The thermodynamic characterization of the H-induced amorphization of CeFe{sub 2} and the determination of the energy site distribution using reaction calorimetry
Journal Article
·
· Acta Materialia
- Univ. of Vermont, Burlington, VT (United States)
The enthalpy of reaction for the hydrogen-induced amorphization of CeFe{sub 2} has been determined as a function of n = H/CeFe{sub 2}. At 323 K the enthalpy for this amorphization reaction is constant equal to {minus}37 kJ/mol {1/2}H{sub 2} from n = 0 to 1.8; it then declines in magnitude to about {minus}24 kJ/mol {1/2}H{sub 2} at n = 3.0. The hydrogen pressure is too small to measure at 323 K except for n {ge} 2.5. Hydrogen can be partially removed from the amorphized hydride at, e.g., 573 K, permitting the determination of the reaction enthalpy for the reintroduction of the hydrogen into the hypostoichiometric amorphous hydride. Enthalpies could be determined using this technique from about n = 2 to 3. From the relationship between these calorimetrically measured {Delta}H{sub H} values and n for the reintroduction of hydrogen into the hypostoichiometric hydride, i.e., n < 3.0, a part of the energy distribution function for the occupation of the interstices with hydrogen can be determined. The distribution function can be closely described by a Gaussian function with {sigma} = 14 kJ/mol {1/2}H{sub 2} with an average value of {Delta}H{sub H}{sup av} = {minus}54 kJ/mol {1/2}H{sub 2}. If the distribution is indeed a Gaussian, the {Delta}H for the following reaction can be obtained, i.e., CeFe{sub 2}(c) {yields} CeFe{sub 2}(a) {Delta}H(c{yields}a) = 51 kJ/mol CeFe{sub 2}.
- OSTI ID:
- 415410
- Journal Information:
- Acta Materialia, Journal Name: Acta Materialia Journal Issue: 10 Vol. 44; ISSN 1359-6454; ISSN ACMAFD
- Country of Publication:
- United States
- Language:
- English
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