Tego Magnan powder

Figure 2.6a shows typical kinetic cnrves of first desorption carried out in a Sieverts-type apparatns at the initial hydrogen pressure of 0.1 MPa (atmospheric pressure of 1 bar) for the as-received, nonmilled, and nonactivated Tego Magnan powder. For each temperatnre, a fresh load of sample was desorbed. At each tem-peratnre in Fig. 2.6a, the desorption process is complete with 100% of MgH des-... 

Figure 2.1 la shows an example of PCT desorption curves for the activated commercial MgH Tego Magnan powder obtained at four different equilibrium temperatures. Figure 2.11b shows the Van t Hoff plot of In p vs. 1,000/T (where p is the pressure and T is the temperature), from which the enthalpy of decomposition of MgH of 71kJ/molH2can be obtained. This value is very close to aU the values for the enthalpy of formation of MgH obtained during absorption as reported... 

Fig. 2.10 (a) Particle of a Tego Magnan powder with the grain size of 67 nm before activation and (b) after activation, (c) Particle of ABCR powder with the grain size of -300 nm before activation and (d) after activation (dark envelope around particles represents Mg(OH) /MgO)... 

Fig. 2.11 (a) PCX desorption curves at various temperatures for the activated commercial MgH Tego Magnan powder numbers indicate the average mid-plateau pressure, (b) The Van t Hoff plot for finding the enthalpy and entropy of decomposition, which is equal to -71 kJ/mol and-134 J/ mol K, respectively. Note excellent coefficient of fit = 0.991 (p - pressure)... 

Fig. Z12 DSC curve of a commercial, as-received and nonactivated Tego Magnan powder obtained under argon flow and a heating rate 4°C/min...

Fig. 2.17 Particle size (ECD) of Tego Magnan powder milled for 100 h under the low-energy impact mode with one magnet and subsequently subjected to five cycles of desorption at 300°C under 0.1 MPa pressure for -4,700 s/absorption at 300°C under 2.5 MPa for 60 min...

Fig. 2.19 Scanning electron micrographs of Tego Magnan powder (a) milled for 100 h under the high-energy impact mode (IMP68 with two magnets at six and eight o clock positions) and (b) after three cycles of desorption at 350°C under 0.1 MPaH pressure for 15 min/annealing at 350°C under pre-vacuum for 15 min/absorption at 350°C under 3.2 MPa pressure for 15 min...

Figures 2.23 and 2.24 show the desorption curves and the Arrhenius plots for the calculation of the apparent activation energy of the Tego Magnan powder milled for 20 and 100 h, respectively. In both cases desorption tests were made under 0.1 MPa...

Table 2.11 The values of the reaction order t in the JMAK equation for the desorption experiments on the Tego Magnan powder milled for 20 h presented in Fig. 2.21 ...

Fig. 2.25 DSC traces of Tego Magnan powder milled continuously for 20 (continuous line) and 100 h (broken line) under the IMP68 mode in argon (heating rate 4°C/min)...

Fig. 2.27 XRD patterns of MgH2 (Tego Magnan) powders milled continuously for 100 h under the IMP68 mode in argon and subsequently desorbed directly after milling in a Sieverts-type apparatus at various temperatures...

Table 2.13 Grain size of P-MgH, Mg, and retained P-MgH in the Tego Magnan powder after milling and desorption at various temperatures...

Figure 2.33 shows the plots of DSC desorption temperatures as a function of powder particle size (BCD) of the milled Tego Magnan powder. It can be seen in... 

Fig. 2.33 DSC hydrogen desorption temperatures vs. particle size for as-received and ball-milled Tego Magnan powder, (a) Onset temperature (T ) and (b) low-temperature (LT) and high-temperature (HT) DSC peaks. Numbers beside data points indicate grain (crystallite) size of the P-MgH phase. Standard deviation bars for the particle size (BCD) are omitted for clarity [6]...

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