One of the bottlenecks in the implementation of a hydrogen economy is the development of storage materials that can uptake high content of H 2 and release it within a suitable temperature and pressure range. Among the proposed hydride systems, the perovskite NaMgH 3 is receiving increasing attention, not only as the Mg ternary based hydride with the highest hydrogen gravimetric (6 wt %) and volumetric density (88 g L À1 ) but also as a stable hydride likely to be formed in the transformation reactions of mixed hydrides. However, there is a large scatter in the literature for both the structure of the NaMgH 3 compound and the thermodynamics of the hydrogenation/ dehydrogenation processes. In this paper a critical review of the literature data, supported by a new set of experimental (in situ synchrotron X-ray diffraction, infrared spectroscopy, high-pressure differential scanning calorimetry, pressure composition isotherms) and theoretical data is presented. The influence of ball milling on the microstructure is studied in the NaMgH 3 in comparison to NaH and MgH 2 . The infrared spectrum of NaMgH 3 compound, assigned by calculated and experimental results, is characterized by vibrational regions around 1100 and 600 cm À1 . In situ synchrotron X-ray diffraction measurements show the desorption reaction of NaMgH 3 into NaH and Mg at about 673 K under 0.2 MPa H 2 , and the successive reabsorption of NaH and Mg back to NaMgH 3 at 623 K under 0.5 MPa H 2 . From high-pressure differential calorimetry, it was measured a formation enthalpy of 141 kJ/mol f.u for NaMgH 3 compound. It was confirmed the possible reaction of NaH with Mg with observation of NaMgH 3 formation in 1.0 MPa H 2 . Finally, this work provides a thermodynamic description of the NaMgH 3 phase by a critical assessment of the available information using the CALPHAD approach and the equilibrium pressureÀtemperature phase diagram is presented.

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Thermochemical conversion of world top crops (rice and wheat) has been extensively investigated (TGA, DTF, SEM, XRD, BET, EA), and main insights are discussed in light of materials and process kinetics. Overall, the results show that the rice husk presents lower reactivity than the wheat straw for all thermal processes regardless of the final temperatures (300°C− 1300°C), residence times (0.6 s−300 min), and atmospheres (100−340 mL·min −1 N 2 /air). The higher reactivity of wheat straw is attributed not only to higher alkali and ash contents but also to differences in both silica morphology and graphitic structure after pyrolysis. Chars produced from slow pyrolysis present more homogeneous characteristics than those produced from fast pyrolysis. Combustion of the chars from slow pyrolysis (up to 900°C) show similar kinetic parameters with activation energies, E a , of 101.8 and 101.0 kJ·mol −1 with pre-exponential factor, A, of 4.3 × 10 7 and 9.6 × 10 7 min −1 for rice husk and wheat straw, respectively; while chars from fast pyrolysis (up to 1300°C) show a range of values. Reaction times at 90 wt % loss (min) and rate constants k o (min −1 ) gives a more clear difference in values even for chars from slow pyrolysis with 12.4 and 0.221 for rice husk and 4.3 and 0.499 for wheat straw, correspondingly. These results are discussed herein according to changes in the physical and chemical characteristics of the nascent chars and, consequently, on their reactivity.