Integral treatment for materials synthesized, improved and applied to hydrogen thermal compression

M.G. RODRIGUEZ; M.R. ESQUIVEL

Moscú-Rusia

Congreso; International Symposium "Metal Hydrogen Systems. Fundamentals and applications" MH2010; 2010

Chemistry Department Lomonosov Moscow State University

In this work, it is achieved an integral treatment consisting in synthesis by mechanical alloying of a mixture of intermetallics, annealing at 600 °C and application to a two stage hydrogen thermal compressor.   A mixture of AB5´s of composition LaNi4.60Al0.40 and La0.25Ce0.52Nd0.17Pr0.06Ni5 was mechanically milled 100 h to reach final stage [1,2,3]. The obtained sample of composition  La0.62Ce0.12Nd0.08Pr0.03Ni4.70Al0.30 as measured by EDS was annealed at 600 °C for 24 h to improve the microstructural properties i.e to minimize the strain and increase the crystallize size. As an example of the improvement achieved, the strain reduced from 2% to 1% and crystallite size increases from 120 ± 5 Å to 900  ± 5 Å as compared as milled samples to annealed samples. The annealed AB5 was refined using the Rietveld method. The structure crystallizes in P6/mmm space group, with cell parameters a = 4.982 ± 0.005 Å and c = 4.001± 0.005 Å. Lanthanides distribute randomly in Wyckoff positions 1a and Ni in positions 2c and Al in positions 2c and 3g. The occupancy of the OF coincides with that of the chemical composition obtained by EDS. The La0.62Ce0.12Nd0.08Pr0.03Ni4.70Al0.30 is used a one-stage hydrogen thermal compression. In this stage, the hydrogen is absorbed at 1500 ± 10 kPa at 25 °C reaching a maximum capacity of 1.2% mass percent. The system is isolated and the the temperature is elevated up to 90 °C. The hydride is desorbed reaching an hydrogen pressure of  2200 ± 10 kPa. As a result, a one stage hydrogen compression is obtained. Under these conditions, the compression ratio reached is 1.46. These results are currently used in the development of a two-stage hydrogen thermal compressor developed under the same integral program. References 1.  M.R.Esquivel, G. Meyer, J. Alloys Compd., 446-447, 2007, 212-217. 2. M.R. Esquivel, G. Meyer, Mat. Sc. For. 570, 72-77. 3. B.A. Talagañis, M.R. Esquivel, G. Meyer, Int. J.Hydrogen Energy 2009, 34, 2009, 2062-2068.