GB/T 33291-2016Measurement method of pressure-composition-temperature for reversable hydrogen asborption & desorption of hydrides (English PDF)

3.1 One-step hydrogenation capacity

After the hydride has undergone a pressure change at a constant temperature and reached a steady state, the ratio of the hydrogen adsorbed in the hydride material to the original mass of the hydride.

3.2 One-step dehydrogenation capacity

After the hydride has undergone a pressure change at a constant temperature and reached a steady state, the ratio of the mass of hydrogen released in the hydride material to the original mass of the hydride.

3.3 Total hydrogenation capacity; Ca

The sum of multiple consecutive one-step hydrogenation capacity of the hydride.

3.4 Total dehydrogenation capacity; Cd

The sum of multiple consecutive one-step dehydrogenation capacity of the hydride.

5.1 Test method

The test uses the isovolumic method.

5.2 Test principle

At a certain temperature, introduce hydrogen gas of known pressure into a container of known volume. Connect the hydride reactor to the vessel. Hydrogenation or Figure 1 -- Test device composition diagram

6.2 Technical requirements for test system

6.2.1 Calibration of equipment and instruments

The equipment and instruments used in this test method shall be regularly calibrated by a qualified inspection agency in accordance with the relevant national standards.

6.2.2 Pressure sensor

The accuracy of the pressure sensor shall not be less than 0.5 per thousand. The significant figures of the test value under the highest working pressure shall be no less than 5 digits.

6.2.3 System leak rate

The pressure drop of the system under the maximum working pressure within 24h shall not be greater than 0.1% of the maximum working pressure.

6.2.4 Connecting pipes

Connecting pipes shall be internally polished stainless-steel pipes. They shall comply with the provisions of 4.4.4 in GB 4962-2008.

6.2.5 Temperature fluctuation

The fluctuation of the ambient temperature of the test system and the working temperature of the sample chamber shall not exceed ±0.5K.

6.2.6 Hydrogen purity

The purity of hydrogen shall meet the requirements of high-purity hydrogen in GB/T 3634.2.

6.2.7 Helium purity

The purity of helium shall meet the requirements of high-purity helium in GB/T 16943.

7.1 Sample shape and sample size

7.1.1 Sample shape

7.1.1.1 Block sample

For block samples, it is advisable to use mechanical crushing method to make granular samples of 0.5mm~1.0mm.

7.1.1.2 Fine powder sample

For fine powder samples, it is advisable to use the mechanical tableting method to make them into flake samples. The tableting pressure shall not be lower than 20MPa.

7.1.2 Sample size

7.1.2.1 Metal hydride hydrogen storage materials

For metal hydride hydrogen storage material samples, the mass shall be 1.0g~2.0g. The sample volume shall not exceed 50% of the sample chamber volume.

7.1.2.2 Other hydride hydrogen storage materials in this Standard

For other hydride hydrogen storage material samples in this Standard, the mass shall not be less than 0.5g. The sample volume shall not exceed 50% of the sample chamber volume.

7.1.2.3 Weighing accuracy of sample

It shall use a weighing tool with an accuracy of not less than 0.2mg to weigh the sample.

7.2 Filling of samples

The filling of the sample shall be carried out as follows:

a) Open valve V1 and valve V3. Fill the sample chamber with about 0.1MPa of helium;

b) Close valve V1 and valve V3. Open the sample chamber H. Load the sample into the sample chamber H. Seal the sample chamber H;

c) Open valve V3 and valve V5. Vacuum the sample chamber to better than 0.1Pa;

d) Close valve V5. Open valve V1. Fill the sample chamber with helium to the maximum test pressure of the sample. Detect if the sample chamber has leakage;

e) When there is no leakage in the sample chamber, open valve V4. Reduce the sample chamber pressure to about 0.1MPa. Close valve V4.

NOTE: For samples with high activity in the air, the filling of the samples shall be carried out in a protective atmosphere.

7.3 Calibration of sample chamber volume

7.3.1 Calibration method

7.3.1.1 Sample chamber volume calibration for granular samples

For the samples made in 7.1.1.1, the volume of the sample chamber can be calibrated at room temperature.

7.3.1.2 Sample chamber volume calibration for powdered samples

For samples made in 7.1.1.2, it shall start at room temperature. Carry out the calibration of sample chamber volume Vsam at Tsam temperature every 20K~50K. The calibrated maximum temperature shall not exceed the minimum temperature for the thermal decomposition of the sample to release hydrogen. When the deviation of the sample chamber volume measured at three consecutive temperature points is less than 1.5%, the average value is taken as the final sample chamber volume Vsam.

7.3.2 Calibration steps

Calibration shall be performed as follows:

a) Open valve V3 and valve V5. After the system is evacuated to better than 0.1Pa, close valve V5;

b) After the sample chamber temperature Tsam is stable, open the valve V1. Fill the sample chamber with helium. After the pressure is stable, record the pressure P5 (P5 shall not be greater than 1.0MPa);

c) Close valve V3. Open valve V5. Evacuate the system to better than 0.1Pa. Close valve V5;

d) Open valve V3. Record stable post-pressure P6. Calculate the sample chamber volume Vsam according to formula (4). the pressure is stable;

d) Open valve V3 to introduce hydrogen into the sample chamber. After the pressure is stable, record the pressure Peq;

e) Use formula (5) to calculate the hydrogenation capacity of the sample;

f) Repeat steps a)~e). The activation is completed until the deviation of the hydrogenation capacity obtained during the two consecutive activation processes is less than 2%;

g) When the activation is completed, repeat step a). Wait for the P-C-T test.

8.1 Temperature setting

The temperature setting shall be carried out as follows:

b) Set the sample chamber temperature to the P-C-T test temperature Tsam and maintain a constant temperature.

8.2 Hydrogenation P-C-T test

The hydrogenation P-C-T test shall be carried out according to the following steps:

a) Record the sample chamber pressure Psam. Close valve V3. Open valve V2. Fill the system with hydrogen. After the system pressure is stable, record the system pressure Psys(0);

b) Open valve V3. Connect the system and the sample chamber. When the pressure meets the equilibrium condition of 8.4, record the equilibrium pressure Peq, sample chamber temperature Tsam, and system temperature Tsys. Close valve V3.

Complete a one-step hydrogenation. The equilibrium pressure Peq is defined as the sample chamber pressure Psam for the next hydrogenation test. Calculate the one-step hydrogenation capacity delta C(m) of the sample according to formula (5). Obtain a set of pressure and hydrogenation capacity data.

c) Increase system pressure by delta Psys. After the system pressure is stable, record the system pressure Psys(n). Proceed to the one-step hydrogenation test according to step b). If the difference delta Peq between the (n+1)th and nth equilibrium pressures is less than 0.5 per thousand of the full scale of the system, then the system pressure rise delta Psys shall be increased by 1.5 times in the (n+2)th one-step hydrogenation measurement. Otherwise, continue to adjust the system pressure according to delta Psys.

d) Repeat the one-step hydrogenation steps. The number of steps shall not be less than 10.

e) When the system equilibrium pressure reaches the maximum hydrogenation pressure specified by the sample, the hydrogenation P-C-T test is completed.

8.3 Dehydrogenation P-C-T test

The dehydrogenation P-C-T test shall be carried out as follows:

a) Record the sample chamber pressure Psam. According to the sample chamber pressure Psam, the system volume Vsys and the sample chamber volume Vsam, adjust the initial pressure Psys(0) of the system;

b) Open valve V3. Connect the system and sample chamber. When the pressure meets the equilibrium condition of 8.4, record the pressure Peq, the sample chamber temperature Tsam, and the system temperature Tsys. Close valve V3. The one-step dehydrogenation of the sample is completed. The pressure Peq is defined as the new pressure Psam of the sample chamber for the next one-step dehydrogenation. Calculate the one-step dehydrogenation capacity delta C(m) of hydride according to formula (5). Obtain a set of pressure and dehydrogenation capacity data.

c) Proceed to the one-step dehydrogenation test according to step b). If the pressure difference between the (n+1)th and nth times after stabilization delta Peq=Peq(n)-Peq(n+1) is less than 0.5 per thousand of the full scale of the system, then the system pressure variable delta Psys shall be increased by 1.5 times in the (n+2)th system one-step dehydrogenation measurement. Otherwise, continue to adjust the system pressure according to delta Psys.

d) Repeat the one-step dehydrogenation steps. The number of steps shall not be less than 10. Until the final pressure Peq is not greater than 0.5 per thousand of the full scale of the system, the dehydrogenation P-C-T test is completed.

8.4 Determination of pressure balance

When the pressure change value within 30min is not greater than 0.5 per thousand of the full scale of the system, the pressure is considered to be balanced. Otherwise, continue to determine the pressure balance for the next 30min until the pressure balance is reached. […]