Stability temperature ranges and mechanism of decomposition of La0.25Ce0.52Nd0.17Pr0.06Ni4.70Sn0.30 in Air

CERON-HURTADO, N.M.; ESQUIVEL, M.R

Ciudad de Buenos Aires

Congreso; CONGRESO SAM/CONAMET 2009; 2009

Asociación Argentina de Materiales

The thermal stability under air of a La0,25Ce0,52Nd0,17Pr0,06Ni4,7Sn0,3 intermetallic was studied in this work. The intermetallic was obtained by low energy mechanical alloying of a mixture of La0,25Ce0,52Nd0,17Pr0,06, Ni and Sn. The thermal analysis was done by Differential Scanning Calorimetry (DSC). The products of reaction were identified by X-Ray Diffraction (XRD) and the elemental composition was verified by Energy Dispersive Spectroscopy (EDS). Quantitative analysis was done using the Rietveld method.  The intermetallic is stable up to T <= 150 °C. At higher T values,  it decomposes according to the following reaction: La0,25Ce0,52Nd0,17Pr0,06(Ni4,70Sn0,3) + 7/2O2  = La0,25Ce0,52Nd0,17Pr0,06O2 + 4,7.NiO + 0,3 SnO. The decomposition occurs in three successive exothermal events. At the slower heating velocity,  (1°C .min-1), the first and second events are observed between 200°C and 400°C. These steps are associated to the decomposition of the former structure and further oxidation of La0,25Ce0,52Nd0,17Pr0,06. The thermal events of both processes are overlapped. The third thermal event occurs between 400 and 600 °C .It is associated to the formation of NiO. The oxidation of Sn is simultaneous with those of the other two constituents. The results are discussed according to the application of La0,25Ce0,52Nd0,17Pr0,06(Ni4,70Sn0,3) in thermal compression of hydrogen.