TWI393782B - Method to improve the activation treatment in ti-v-cr based bcc hydrogen storage alloys - Google Patents

Description

Method for improving activation performance of Ti-V-Cr system BCC hydrogen storage alloy

The technical field to which this case belongs is mainly the hydrogen energy solid state storage technology of New Energy Technology. In addition, the viewpoint of the process technology to which the invention belongs is also related to the smelting, mechanical synthesis and pre-activation treatment techniques of hydrogen storage alloys.

Hydrogen is one of the cleanest energy sources because its by-products are only water. However, in practical applications, because the molecular weight of hydrogen is too small, the storage volume is too large, although it can be stored in an ultra-high pressure mode, it raises safety concerns. Since the development of AB ₅ LaNi ₅ hydrogen storage alloy by Philips in the Netherlands in 1969, the hydrogen storage reaction speed, high hydrogen content, hysteresis effect and reaction heat effect of the alloy are low, the platform pressure is low, and the activation is easy. It can realize the rapid and safe storage of hydrogen, and some of them include: replacing the expensive pure metal La with rare earth mixed metal (Mm, ML), and partially replacing Ni with Al, Co, Mn, Cu and other elements to make the alloy life. After the improvement of elongation, anti-toxicity and anti-electrolyte corrosion, it was quickly applied to Ni-MH batteries. At the same time, in order to increase the capacity and improve the hydrogen storage performance of the alloy, the AB ₂ hydrogen storage alloy developed by Ovonic Company of the United States is also almost in contact with the AB ₅ type hydrogen storage alloy, and is mainly used as the anode material of the MH/Ni battery. . Although it is widely used in AB ₅ or AB ₂ hydrogen storage alloys of nickel-hydrogen batteries, it has the advantages of large capacity, safety, non-toxicity and long service life compared with nickel-cadmium batteries. However, hydrogen storage for fuel cell vehicles as transportation power. In the case of a can, a general commercial hydrogen storage alloy having a hydrogen storage capacity of about 1.5% by weight is still insufficient in storage weight density.

On the other hand, it is mainly used as a type AB hydrogen storage alloy for fuel cell hydrogen storage tanks (mainly composed of titanium and iron). Although it has a material price advantage, its maximum hydrogen storage capacity is less than 2.0 wt%, and it is easy. Poisoning due to impure hydrogen. Therefore, all countries strive to develop hydrogen storage alloys having a higher capacity in weight percentage. Since 2000, BCC hydrogen storage alloys based on Ti, V and Cr have been published in the journals such as US Pat. No. 6,582,814 and No. 6616891, and in journals such as Journal of Alloys and Compounds, due to their hydrogen storage capacity. In the conventional AB ₅ or AB _{2, there is} a leap forward (almost twice or more), which immediately attracts the attention of researchers in hydrogen storage alloy materials and related industries.

However, in these studies, it was quickly found that such a BCC hydrogen storage alloy containing titanium vanadium chromium as a main element is generally slower in activation speed than conventional AB ₅ or AB ₂ and is also difficult. A conventional activation treatment method which is quite useful for a conventional AB ₅ or AB ₂ hydrogen storage alloy, comprising: a so-called chemical acid pickling process (wet method) using hydrofluoric acid, nitric acid or a mixture of the two, the main purpose of which is Corrosion method removes the surface of the hydrogen storage alloy to form an oxide layer easily; or another physical activation process (dry method) under a high-temperature, high-pressure hydrogen atmosphere, that is, the hydrogen storage alloy expands due to hydrogen absorption volume, resulting in alloy hydrogen Brittle cracking produces a fresh, non-oxidized surface (boundary) surface that makes it easy to absorb hydrogen and increase hydrogen absorption rate. However, these treatment methods which are quite effective for the conventional hydrogen storage alloys, when applied separately to the BCC hydrogen storage alloys, have been tested by actual tests, and it is still difficult to smoothly activate and absorb hydrogen. Sometimes, even in the alloy melting process, if the degree of vacuum is slightly worse, the hydrogen storage alloy to be melted is completely incapable of activation, not to mention the subsequent use as a storage hydrogen.

Another effective practice for this problem is to use mechanical alloying (MA) and high energy ball milling (HEBM) in addition to the vacuum melting process. Since these two methods can cause a large amount of plastic deformation, cold welding and cracking in the alloying process, resulting in the formation of a nanocrystalline alloy, the rate of hydrogen absorption and desorption can be increased and the activation problem can be improved. In many studies, the mechanical alloying method has been proven to successfully prepare BCC hydrogen storage alloys, and the problem of rapid hydrogen absorption and desorption to solve the problem of activation is achieved. However, these BCC hydrogen storage alloys prepared by mechanical alloying or high-energy ball milling have a hydrogen storage capacity far less than the same composition and are vacuum smelting plus rapid cooling processes. Therefore, for the practical commercial application of BCC high-capacity hydrogen storage alloys, there is a strong demand in the industry for how to effectively solve the activation problem without damaging its hydrogen storage capacity.

Compared with the conventional dry and wet activation processes, the inventors have repeatedly tested and found that a small amount of metal palladium (Pd) is added during or before the smelting of BCC hydrogen storage alloys containing Ti, V, and Cr as main elements. In which the element is located, a high-capacity hydrogen storage alloy that does not require subsequent activation treatment is obtained. The optimum amount of palladium (Pd) element added is 0.05 to 1.0 wt% relative to the original hydrogen storage alloy. When the amount of palladium (Pd) added is less than 0.05 wt%, it is not enough to activate the BCC hydrogen storage alloy which is not easy to activate. When the addition amount exceeds 1.0 wt%, the BCC hydrogen storage alloy can directly absorb hydrogen although it does not need subsequent activation treatment. However, its hydrogen storage capacity will drop sharply.

Although the general commercial hydrogen storage alloys are currently mainly produced by vacuum melting, the activation method of the present invention is not limited to the melting process. In particular, for BCC hydrogen storage alloys with Ti, V, and Cr as main elements, because of their high melting point and high activity, they cannot be carried out by conventional vacuum melting methods, or mechanical alloy processes (for example, powder). The raw materials are ball milled to synthesize. At this time, as long as the same dose (0.05~1.0 wt%) of palladium (Pd) powder is mixed in the ball milling process and ball-milled together with the Ti, V, and Cr powders, the activation performance of the BCC hydrogen storage alloy can be improved.

The features and effects of the present invention will be more apparent from the following examples and comparative examples, so that those skilled in the <RTIgt;

[Comparative example 1]

The Ti-V-Cr BCC hydrogen storage alloy raw material is placed in a quenchable double-layer water-cooled copper mold crucible at a ratio of equal ratio of Ti, V and Cr, and vacuuming is started until 2*10- 3 torr then passes high purity hydrogen to 0.8 atm. It is then smelted by arc heating, re-melting six times each time for 50 seconds and repeatedly turning over to ensure uniformity of the alloy. The cast Ti-V-Cr BCC hydrogen storage alloy ingot was mechanically crushed to fine particles of 1-3 mm size for subsequent hydrogen absorption and desorption experiments. According to the conventional experience, since the hydrogen storage alloy contains a highly active element, the surface thereof is very easy to form an oxide layer, and the formation of the oxide layer hinders the entry of hydrogen atoms into the lattice gap of the crystal. Therefore, the conventional AB ₅ or AB ₂ hydrogen storage alloy must be pre-activated (acid washed) before use or before the so-called hydrogen storage and PCT curve test, so that hydrogen can be absorbed smoothly. Accelerate the absorption and release of hydrogen.

Due to the strong binding ability of titanium and vanadium to oxygen, BCC hydrogen storage alloys are more likely to form oxide layers than the surface of conventional AB ₅ or AB ₂ hydrogen storage alloys, making it difficult for hydrogen atoms to diffuse into the interior of the alloy, so smelting and fragmentation The fine particles of the Ti-V-Cr BCC hydrogen storage alloy are also formulated as (A)H ₂ O:H ₂ NO ₃ :HF=3:2:1, (B)H ₂ O:H ₂ NO ₃ :HF=6:1:1, (C)H ₂ O:H ₂ NO ₃ :HF=6:2:1 and (D)H ₂ O:H ₂ NO ₃ :HF=2:1:1 acid The washing liquid was subjected to a pickling treatment (activation treatment) at a corrosion time of 30 seconds, 1 minute, and 2 minutes, respectively, to remove the oxide layer on the surface to facilitate the subsequent hydrogen absorption and desorption reaction.

However, the actual hydrogen absorption and desorption test found that it should be (A) H ₂ O: H ₂ NO ₃ : HF = 3: 2: 1, (B) H ₂ O: H ₂ NO ₃ : HF = 6: 1:1, (C)H ₂ O:H ₂ NO ₃ :HF=6:2:1 and (D)H ₂ O:H ₂ NO ₃ :HF=2:1:1 pickling solution after 30 seconds 1, 1 minute or 2 minutes of pickling activation pretreatment, when hydrogen is applied at 50 bar of hydrogen, even if the maximum hydrogen storage capacity of Ti-V-Cr BCC hydrogen storage alloy is still less than 0.8 wt% for one hour, much lower than its The theoretical value is even worse than the AB ₅ or AB ₂ hydrogen storage alloy. This result shows that the traditional pickling activation method is still difficult to eliminate the impurities on the surface of the powder by the BCC hydrogen storage alloy mainly composed of Ti-V-Cr, and a complete hydrogen absorption reaction is produced.

[Comparative Example 2]

The Ti-V-Cr BCC hydrogen storage alloy raw material is placed in a quenchable double-layer water-cooled copper mold crucible at a ratio of equal ratio of Ti, V and Cr, and vacuuming is started until 2*10- 3 torr then passes high purity argon to 0.8 atm. It is then smelted by arc heating, re-melting six times each time for 50 seconds and repeatedly turning over to ensure uniformity of the alloy. The cast Ti-V-Cr BCC hydrogen storage alloy ingot was mechanically crushed to fine particles of 1-3 mm size for subsequent hydrogen absorption and desorption experiments. The smelted Ti-V-Cr BCC hydrogen storage alloy ingot, according to the known experience, because of the high active element, the surface of the Ti-V-Cr BCC hydrogen storage alloy is very easy to form an oxide layer, and the formation of the oxide layer hinders the entry of hydrogen atoms into the lattice gap of the crystal. Pre-activation treatment is required prior to use or prior to testing for hydrogen storage and so-called hydrogen absorption and desorption hydrogen PCT curves.

Since the previous pickling activation pretreatment (chemical method) has a very limited effect on the BCC hydrogen storage alloy with Ti-V-Cr as the main component, it is also known that the other is the physical pre-activation treatment: first The fine particles of the shattered Ti-V-Cr BCC hydrogen storage alloy are placed in the alloy tank and then vacuumed to below 10-3 torr for 30 minutes, then 20 bar of hydrogen is introduced at room temperature, and the temperature is raised to 400 ° C. The surface oxide layer was subjected to reduction activation by maintaining a hydrogen atmosphere pressure of 10 bar for 1 hour. The hydrogen is then released at the same 400 ° C. When less than 1 bar, the physical pump is activated by activating the vacuum pump and evacuating to below 10-3 torr. However, when the Sieevert method is used to measure the hydrogen storage of Ti-V-Cr BCC hydrogen storage alloy When the amount was found, the maximum hydrogen storage capacity was found to be less than 0.6 wt%, which was much lower than the theoretical value, indicating that the activation was not achieved. Therefore, the physical activation mode is repeated twice, three times or even five times. However, even after one hour, the maximum hydrogen storage capacity of the Ti-V-Cr BCC hydrogen storage alloy is still less than 0.8 wt%, which is much lower than Its theoretical value. The results also show that the activation mode of the traditional physics is still difficult to eliminate the impurities on the surface of the powder by the BCC hydrogen storage alloy mainly composed of Ti-V-Cr, and generate a complete hydrogen absorption reaction.

[Comparative Example 3]

The Ti-V-Cr BCC hydrogen storage alloy raw material is placed in a quenchable double-layer water-cooled copper mold crucible at a ratio of equal ratio of Ti, V and Cr, and vacuuming is started until 2*10- 3 torr then passes high purity argon to 0.8 atm. It is then smelted by arc heating for 50 seconds and flipped over and re-melted six times to ensure uniformity of the alloy. The cast Ti-V-Cr BCC hydrogen storage alloy ingot is mechanically crushed to fine particles of 1-3 mm size for subsequent physical hydrogen absorption and desorption. For a Ti-V-Cr BCC hydrogen storage alloy ingot in which an oxide layer is easily formed on the surface after melting, a so-called pre-activation treatment is first performed by a pickling activation pretreatment (chemical method) and a physical activation method to accelerate the hydrogen absorption reaction. The pickling solution is: (A) H ₂ O: H ₂ NO ₃ : HF = 3: 2: 1, (B) H ₂ O: H ₂ NO ₃ : HF = 6: 1:1, (C ) H ₂ O: H ₂ NO ₃ : HF=6:2:1 and (D)H ₂ O:H ₂ NO ₃ :HF=2:1:1 acid pickling solution, the etching time is 30 seconds respectively With 2 minutes to remove the oxide layer on the surface for subsequent physical activation.

The acid-washed powder is immediately dried and placed in an alloy bath. The vacuum is evacuated to below 10-3 torr for 30 minutes in the alloy bath, and 20 bar of hydrogen is introduced at room temperature, and the temperature is raised to 400 ° C. The surface oxide layer was subjected to reduction activation by maintaining a hydrogen atmosphere pressure of 10 bar for 1 hour. The hydrogen is then released at the same 400 ° C. When less than 1 bar, the physical pump is activated by activating the vacuum pump and evacuating to below 10-3 torr. However, when the hydrogen storage capacity of Ti-V-Cr BCC hydrogen storage alloy is measured by Sievert method, even if it lasts for one hour, its maximum hydrogen storage capacity is still less than 0.8wt%, which is far below its theoretical value, showing the physical addition of the conventional method. The chemical activation mode is extremely limited for BCC hydrogen storage alloys with Ti-V-Cr as the main component.

[Embodiment 1]

The Ti-V-Cr BCC hydrogen storage alloy raw material and a trace amount of metal palladium (Pd) element are made up of a ratio of Ti, V, Cr elements in an atomic ratio and doped with 0.03 wt% (300 ppm) of metal palladium. In the case of the (Pd) element, after being placed in a quenchable double-layer water-cooled copper mold crucible, vacuuming is started to 2*10-3 torr and then high-purity argon is introduced to 0.8 atm. It is then smelted by arc heating for 50 seconds and flipped over and re-melted six times to ensure uniformity of the alloy. The cast Ti-V-Cr BCC hydrogen storage alloy ingot was mechanically crushed to fine particles of 1-3 mm size for subsequent hydrogen absorption and desorption experiments.

The Ti-V-Cr BCC hydrogen storage alloy containing 0.03 wt% of metal palladium is directly measured by Sievert in the manner of no physical or chemical (pickling) activation. Bar under hydrogen pressure, this alloy It can absorb hydrogen quickly, and the hydrogen storage capacity can reach 3.4wt% in 10 minutes, which is close to its theoretical value. It shows that adding a small amount of metal palladium (Pd) element in Ti-V-Cr BCC hydrogen storage alloy can be obtained. A high capacity hydrogen storage alloy that does not require subsequent activation treatment at all.

[Embodiment 2]

The Ti-V-Cr BCC hydrogen storage alloy raw material and a trace amount of metal palladium (Pd) element are in the ratio of Ti, V and Cr in an atomic ratio and doped with 0.05 wt% (500 ppm) of metal palladium. In the case of the (Pd) element, after being placed in a quenchable double-layer water-cooled copper mold crucible, vacuuming is started to 2*10-3 torr and then high-purity argon is introduced to 0.8 atm. It is then smelted by arc heating for 50 seconds and flipped over and re-melted six times to ensure uniformity of the alloy. The cast Ti-V-Cr BCC hydrogen storage alloy ingot was mechanically crushed to fine particles of 1-3 mm size for subsequent hydrogen absorption and desorption experiments.

The Ti-V-Cr BCC hydrogen storage alloy containing 0.05 wt% of metal palladium is directly measured by Sievert in the manner of no physical or chemical (pickling) activation, and is found at room temperature 18 Under the hydrogen pressure of bar, the alloy can absorb hydrogen rapidly, and the hydrogen storage capacity can reach 3.4wt% in 5 minutes, which is close to its theoretical value, indicating that a small amount of metal palladium (Pd) element is added in Ti-V-Cr BCC. In the hydrogen storage alloy, a high-capacity hydrogen storage alloy which does not require subsequent activation treatment can be obtained.

[Embodiment 3]

The Ti-V-Cr BCC hydrogen storage alloy raw material and a trace amount of metal palladium (Pd) element The parts are Ti, V, and Cr in an atomic ratio and are doped with 0.5 wt% of metal palladium (Pd) element. After being placed in a quenchable double-layer water-cooled copper mold crucible, the vacuum is started to 2 *10-3 torr then passes high purity argon to 0.8 atm. It is then smelted by arc heating for 50 seconds and flipped over and re-melted six times to ensure uniformity of the alloy. The cast Ti-V-Cr BCC hydrogen storage alloy ingot was mechanically crushed to fine particles of 1-3 mm size for subsequent hydrogen absorption and desorption experiments.

The Ti-V-Cr BCC hydrogen storage alloy containing 0.5 wt% of metal palladium is directly measured by Sievert in the manner of no physical or chemical (pickling) activation, and is found at room temperature 6 Under the hydrogen pressure of bar, the alloy can absorb hydrogen rapidly, and the hydrogen storage capacity can reach 3.45wt% in 5 minutes, which is close to its theoretical value, indicating that a small amount of metal palladium (Pd) element is added in Ti-V-Cr BCC. In the hydrogen storage alloy, a high-capacity hydrogen storage alloy which does not require subsequent activation treatment can be obtained.

[Embodiment 4]

The Ti-V-Cr BCC hydrogen storage alloy raw material and a trace amount of metal palladium (Pd) element are made up of a ratio of Ti, V, Cr elements in an atomic ratio, and 1.0 wt% of metal palladium (Pd) element is doped. In this case, after placing the quenched double-layer water-cooled copper mold crucible, start vacuuming to 2*10-3 torr and then pass high-purity argon to 0.8 atm. It is then smelted by arc heating for 50 seconds and flipped over and re-melted six times to ensure uniformity of the alloy. The cast Ti-V-Cr BCC hydrogen storage alloy ingot was mechanically crushed to fine particles of 1-3 mm size for subsequent hydrogen absorption and desorption experiments.

This Ti-V-Cr BCC hydrogen storage alloy containing 1.0wt% metal palladium does not do at all. In the physical or chemical (pickling) activation mode, when the hydrogen storage capacity is measured directly by Sievert, it is found that the hydrogen can be rapidly absorbed under the hydrogen pressure of 5.8 bar at normal temperature, and the hydrogen storage amount is within 5 minutes. It can reach 3.2wt%. It is shown that the addition of a trace amount of metallic palladium (Pd) element in the Ti-V-Cr BCC hydrogen storage alloy provides a high-capacity hydrogen storage alloy which does not require subsequent activation treatment.

[Embodiment 5]

The Ti-V-Cr BCC hydrogen storage alloy raw material and a trace amount of metal palladium (Pd) element are made up of a ratio of Ti, V, Cr elements in an atomic ratio, and a 3.0 wt% metal palladium (Pd) element is doped. In this case, after placing the quenched double-layer water-cooled copper mold crucible, start vacuuming to 2*10-3 torr and then pass high-purity argon to 0.8 atm. It is then smelted by arc heating for 50 seconds and flipped over and re-melted six times to ensure uniformity of the alloy. The cast Ti-V-Cr BCC hydrogen storage alloy ingot was mechanically crushed to fine particles of 1-3 mm size for subsequent hydrogen absorption and desorption experiments.

The Ti-V-Cr BCC hydrogen storage alloy containing 3.0 wt% of metal palladium was found to be at room temperature 4.6 when the hydrogen storage amount was directly measured by Sievert mode without physical or chemical (acid wash) activation. Under the hydrogen pressure of bar, the alloy can absorb hydrogen rapidly, and the hydrogen storage capacity can reach 1.8 wt% in 5 minutes, but the hydrogen storage capacity is still 1.8 wt% after 30 minutes, indicating the addition of metal palladium (Pd) element. Although the Ti-V-Cr BCC hydrogen storage alloy can be completely eliminated from the conventional activation process, the amount of addition is not excessive, otherwise the hydrogen storage amount will be sacrificed.

It can be found from the first embodiment to the fifth embodiment that the Ti-V-Cr BCC hydrogen storage alloy is added. The metal palladium (Pd) element has a significant improvement effect on the BCC hydrogen storage alloy which is not easily activated. However, when the amount of palladium (Pd) added is less than 0.05 wt%, higher hydrogen pressure is required to activate and absorb hydrogen of the BCC hydrogen storage alloy. When the addition amount exceeds 1.0 wt%, the BCC hydrogen storage alloy does not need subsequent activation. The treatment can directly absorb hydrogen, but its hydrogen storage capacity will drop sharply. In terms of practicality, the general hydrogen charging pressure is preferably less than 20 bar, and the hydrogen storage capacity is at least greater than 3.0 Wt%, so the optimum amount of palladium element added is 0.05 to 1.0 wt% relative to the original hydrogen storage alloy. %. Throughout the description of the invention, those skilled in the art will be able to understand the features and functions of the present invention and can implement it accordingly.

In summary, the present invention is a novelty, progressive and available for industrial use, and should conform to the patent application requirements stipulated in the Patent Law of China, and the invention patent application is filed according to law. Patent, to the feeling of prayer.

Claims (3)

A method for improving the activation performance of a high capacity BCC hydrogen storage alloy having a hydrogen storage capacity of more than 3.0% by weight in a Ti-V-Cr system, characterized in that an additional 0.05 to 1.5 weight percent of palladium (Pd) is added during the alloying process. The original hydrogen storage alloy chemical composition. For example, in the method of claim 1, wherein the alloying process is a vacuum melting process. For example, in the method of claim 1, wherein the alloying process is a mechanical alloy process.