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Kharkov Institute of Physics and Technology

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Experimental study of hydrogen sorption-desorption parameters of zirconium and its alloys in various nanostructured states

Work in 2015 was carried out to develop perspective hydrogen storage alloys for the needs of the alternative hydrogen energy, and the experimental study of the effect of the structural state of zirconium and its alloys on the processes of sorption and desorption of hydrogen.

 Samples of perspective alloys of zirconium in various structural states:

 stoichiometric ZrV2

 eutectic Zr0,6V0,4

 Samples of both types were used for high-energy ball grinding to obtain ultra-dispersed structural states of the material.

 With the help of X-ray diffraction analysis, we found that by the method of high-energy ball grinding, powders of hydrogen storage alloys can be fabricated in a controlled manner both in nanocrystalline and quasi-amorphous nanostructured states.

 Methodic of the hydrogenation the samples

 The research of the hydrogen capacity of alloys was carried out by a volumetric method.

 In a hermetic volume, the test sample was subjected to contact with hydrogen. Then the chamber with the sample was heated and the pressure P was measured as a function of temperature T for different amounts of hydrogen.

 Cast samples were hydrogenated up to a temperature of 400 ... 450 °C. The fast quenched samples were hydrogenated to a slightly lower temperature of 350 °C for avoid their crystallization.

 The first cycle of experiments, (see results in Table. 1), was performed with unmilled samples and was carried out under pressure up to 3.5 atm.

 The second series of experiments (see Table 2) on the study of milled alloys was carried out using an automated Sieverts technique. The amount of absorbed hydrogen was determined by two methods: the difference in pressure in the chamber before and after saturation, and also by the weight method. In addition, the amount of sorbed hydrogen was qualitatively monitored with the help of the MX-7203 mass spectrometer.

Table 1 - Parameters of sorption and desorption of hydrogen initial by initial (Not milled) Zr-V alloys (hydrogen pressure up to 3.5 atm)
Sample Tactiv (°) A
(3/ [. %])
Vrech
(3/
[. %])
T1 (°) T2 (°)
Zr0.6V0.4 fast quenched 190 272 [2.42%] 96,4 [0.858%] 60100 90150
ZrV2 fast quenched 300 196 [1.74%] 96,1 [0.855%] 190260 200250
Zr0.6V0.4 cast 300 288 [2.56%] 149 [1,33%] 300350 150200
ZrV2 cast 350 275 [2.45%] 27 [0.24%] 250425 300350

Tactiv - activation temperature of alloy hydrogenation ;
A amount of hydrogen absorbed by the alloy;
Vrech the amount of hydrogen absorbed by the alloy after regeneration in 2 hours, under = 350 °;
T1, T2 timezone of active hydrogen absorption at the first hydrogenation and after regeneration.

Table 2 - Hydrogenation parameters of samples of Zr-V alloys milled in a ball mill in argon (30 min.) and ethanol (30 min.) in a different structural state and atomic composition (hydrogen pressure up to 0.7 atm).
Sample Tactiv (°) A (. %) V (. %) Trech
(°)
Vrech
(. %)
Zr0.6V0.4 fast quenched 230 1,712% 1,524% 345 0,5265%
ZrV2 fast quenched 260 1,527% 1,143% 350-400 0,459%
Zr0.6V0.4 cast 225 2,238% 1,58% 320 1,137%
ZrV2 cast 240 1.946% 1,12% 320 1,12%

Tactiv the activation temperature of the alloy (start temperature of hydrogen absorption);
a the amount of hydrogen absorbed by the alloy, calculation by the weight method;
V approximate evaluation of the hydrogen capacity by the pressure reduce in the absorption chamber;
Trech temperature of hydrogen desorption during regeneration;
Vrech hydrogen absorbed by the sample(mass%) in the second cycle after regeneration.

 Conclusion

 Analysis of the data in Tables 1 and 2 shows that in all cases cast alloys absorbed more hydrogen than fast quenched ones.

 The pressure growth gives a minor increase in the amount of absorbed hydrogen.

 For the milled samples, the second hydrogenation of the alloys occurs at the same temperatures as the first. In previous experiments with alloys of the same type that did not exhausted for ball milling, the activation was as a rule carried out at temperatures exceeding the common range of hydrogen absorption by the researched alloys.

 Fast quenched milled samples had a higher hydrogen absorption temperature than cast ones.
  2008- SPE RESST
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