Model for the Prediction of the Hydriding Thermodynamics of Pd-Rh-Co Ternary Alloys

Conference · Mon Mar 01 04:00:00 EST 1999

OSTI ID:758926

Teter, D F; Thoma, D J

A dilute solution model (with respect to the substitutional alloying elements) has been developed, which accurately predicts the hydride formation and decomposition thermodynamics and the storage capacities of dilute ternary Pd-Rh-Co alloys. The effect of varying the rhodium and cobalt compositions on the thermodynamics of hydride formation and decomposition and hydrogen capacity of several palladium-rhodium-cobalt ternary alloys has been investigated using pressure-composition (PC) isotherms. Alloying in the dilute regime (<10 at.%) causes the enthalpy for hydride formation to linearly decrease with increasing alloying content. Cobalt has a stronger effect on the reduction in enthalpy than rhodium for equivalent alloying amounts. Also, cobalt reduces the hydrogen storage capacity with increasing alloying content. The plateau thermodynamics are strongly linked to the lattice parameters of the alloys. A near-linear dependence of the enthalpy of hydride formation on the lattice parameter was observed for both the binary Pd-Rh and Pd-Co alloys, as well as for the ternary Pd-Rh-Co alloys. The Pd-5Rh-3Co (at. %) alloy was found to have similar plateau thermodynamics as a Pd-10Rh alloy, however, this ternary alloy had a diminished hydrogen storage capacity relative to Pd-10Rh.

• Research Organization: Los Alamos National Lab., NM (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 758926
• Report Number(s): LA-UR-99-1341
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
36 MATERIALS SCIENCE
COBALT ALLOYS
HYDRIDATION
HYDROGEN STORAGE
MATHEMATICAL MODELS
PALLADIUM ALLOYS
RHODIUM ALLOYS
TERNARY ALLOY SYSTEMS
THERMODYNAMICS