Al-ga-sn alloy for low-temperature hydrogen production and preparation process thereof

Abstract

The application discloses an Al-Ga-Sn alloy for low-temperature hydrogen production and a preparation process thereof. By controlling the pouring temperature of a mold, the grain growth process of the Al-Ga-Sn alloy during cooling and the embrittlement degree of internal liquid metal to the Al matrix can be further controlled. Research shows that the poured Al-Ga-Sn alloy has good hydrogen production performance, and hydrogen can be immediately produced when the alloy contacts with water. After the Al-Ga-Sn alloy poured by using a 600 DEG C mold is crushed and sieved through a 100-mesh sieve, 0.1 g of Al-Ga-Sn alloy powder at room temperature reacts with ice blocks at-16 DEG C, and 14.7 mL of hydrogen can be produced within 1 h. That is, the alloy powder has a certain reaction starting capacity at low temperature, and can be used for on-line hydrolysis hydrogen production under low-temperature conditions.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production by hydrolysis of aluminum alloys, and specifically relates to an Al-Ga-Sn alloy with low-temperature hydrogen production performance and its preparation process. Background Technology

[0002] Against the backdrop of the energy crisis, the development and use of new energy sources to gradually replace traditional fossil fuels has become an inevitable trend in social development. Among many new energy fields, hydrogen energy has significant advantages: it is pollution-free, has a high calorific value, and has promising application prospects. However, given the current state of hydrogen energy technology development, especially under harsh conditions such as fieldwork, emergency response, military operations, and low temperatures, solving the problems of hydrogen production, storage, and transportation is a necessary prerequisite for the widespread use of hydrogen energy. Compared with high-pressure hydrogen storage and liquid hydrogen storage, online hydrogen supply technology integrates hydrogen storage and use, eliminating the need for large-scale hydrogen supply infrastructure and long-distance transportation, thus solving the aforementioned problems to some extent. On the other hand, expanding the application scope of hydrogen energy and hydrogen fuel cells is crucial. As temperatures decrease, extremely cold regions and cold climates (such as high altitudes or winters) place higher demands on hydrogen production and the commercial use of hydrogen fuel cells. Currently, hydrogen fuel cells have achieved cold start-up at -30°C, but there are no mature low-temperature (<0°C) online hydrogen supply materials and methods. Therefore, developing low-temperature online hydrogen supply materials is of great significance.

[0003] The pioneering work of Dudoladov et al. revealed that Al can hydrolyze to produce hydrogen in salt solutions at low temperatures (<0 °C). However, this process involves a long induction time and low conversion efficiency. When the reaction temperature is as low as -40 °C, the hydrogen conversion efficiency of 90 wt% Al powder activated with Ga, In, and Zn in a 34 wt% KOH solution is only 17%. Buryakovskaya et al. investigated the hydrolysis performance of Mg powder in different salt solutions at -20 °C. They found that the hydrogen conversion efficiency of Mg powder was 78.2% in a 25.3 wt% AlCl3 solution at -20 °C, and only 15.6% in a 21 wt% MgCl2 solution. The latter required a reaction induction time of up to 55 minutes. Ouyang Liuzhang et al. prepared an Al-31.9 wt% Li alloy using a melt method. In a 40 vol% ethanol aqueous solution at -30 ℃, the hydrogen production rate reached 1076 mL / g within 0.5 minutes, with a hydrogen conversion efficiency of 71.8%. Wang Huihu et al. prepared Al alloy / NaCl / LiH / g-C3N4 composite materials using a ball milling method. The study found that the addition of LiH completely eliminated the induction time and improved the low-temperature reactivity of the Al alloy / NaCl / LiH / g-C3N4 composite material. In a 23 wt% NaCl aqueous solution at -20 ℃, the Al alloy / NaCl / 1.5%LiH / g-C3N4 composite material exhibited the highest hydrogen production, at 1095 mL·gAl. -1 The maximum hydrogen production rate is 120 mL·gAl -1 ·s -1 Zhang Jinying et al. prepared LiAlH4 sheets with a density of 92.7% and developed a solution composed of 27.1 wt% KOH (to water) and 30.0% ethylene glycol (to KOH) for low-temperature reactions. Their study found that the hydrolysis induction time of LiAlH4 was approximately 35 s at -40 °C, while the hydrolysis reaction had almost no induction time between -30 and 0 °C. The hydrogen production rate in the constant reaction zone increased from 10.83 mL / s·g at -40 °C to 18.67 mL / s·g at 0 °C. Based on the experimental data, the activation energy of the hydrolysis reaction of LiAlH4 with the used aqueous solution was derived from the Arrhenius equation as 6.83 ± 0.34 kJ / mol. The solid hydrolysis product, after washing with deionized water, was confirmed by XRD and SEM to be identical to the direct hydrolysis product, indicating that the hydrolysis reaction does not consume KOH and ethylene glycol.

[0004] In the field of hydrogen production from cast aluminum alloys, Wang Wei et al. used water-cooled copper molds to cast Al-Ga-In-Sn alloys of different masses to obtain alloy rods or ingots, achieving control over the alloy grain size. Their research found that alloys with smaller grain sizes exhibited significantly improved hydrogen production performance. When the grain size decreased from 258 μm to 23 μm, the activation energy Ea decreased by approximately 30%. This demonstrates that the hydrogen production performance of alloys can be controlled by adjusting the grain size, and this work suggests that reducing the grain size is beneficial for improving the hydrogen production performance of alloys.

[0005] In the field of traditional aluminum alloy casting (utilizing its mechanical properties for structural materials), mold temperature is a crucial process parameter. Ryong-Chol Kim et al. investigated the role and influence of mold temperature in high-pressure die casting of AlSi9Cu1Mg alloy. Their study found that controlling the mold temperature helps reduce porosity defects caused by thermal shock from the molten metal. Higher mold temperatures result in better fluidity of the molten metal, facilitating cavity filling and reducing porosity formation. However, higher mold temperatures may lead to a reduced cooling rate, thus affecting the microstructure and properties of the casting. The cooling rate has a significant impact on the microstructure of the casting. Faster cooling rates generally result in finer grain structures and provide better mechanical properties. Through optimization studies, the optimal mold temperature was determined to be 150 °C. Therefore, in the field of traditional aluminum alloy casting, controlling the mold temperature is primarily aimed at obtaining superior mechanical properties in the casting.

[0006] A review of previous research in the field of low-temperature hydrogen production reveals that almost all researchers have employed methods such as high-energy ball milling, strong acid / alkaline conditions, and the addition of active metals or metal hydrides to enhance the reactivity of low-temperature hydrogen production materials. While these methods improve material reactivity, they also introduce problems such as complex preparation methods, high production costs, high risk factors, and difficulties in safe material storage. The work of Wang Wei et al. provided insights into the relationship between grain size and the hydrogen production performance of aluminum alloys, but it did not directly link this to achieving low-temperature hydrogen production performance through wide-range adjustment of mold temperature. Furthermore, while work in the traditional aluminum alloy casting field indicates that mold temperature is a crucial parameter for optimizing the mechanical properties of aluminum alloy castings, the hydrogen production performance of aluminum alloys is preferred over their mechanical properties in the hydrogen production field. This invention addresses these issues by simply controlling the common process parameter of mold temperature. Through high-temperature melting, casting, crushing, and sieving of Ga, Sn, and Al, Al-Ga-Sn alloy powder with low-temperature reactivity is prepared, effectively solving the aforementioned problems in the field of low-temperature hydrogen production and achieving control over the low-temperature hydrogen production performance of aluminum alloys. Studies have found that mold temperature can simultaneously affect grain size and the intensity of liquid metal embrittlement (LME), meaning that the effect of mold temperature on the hydrogen production performance of alloys is not always linear. At low temperatures, the hydrogen production performance of bulk alloys initially increases and then decreases with increasing mold temperature; the hydrogen production performance of alloy powders increases monotonically with increasing mold temperature. After low-temperature start-up, applying certain thermal compensation to the reaction system can significantly improve the hydrogen production performance of the alloys. Summary of the Invention

[0007] This paper aims to invent an Al-Ga-Sn alloy powder with low-temperature hydrogen production performance and proposes a method for preparing this alloy powder.

[0008] The preparation method of the hydrogen production alloy used is as follows:

[0009] 1) Weigh each raw material according to the formula into a container, and place the container in an atmosphere resistance furnace under a nitrogen protective atmosphere. The heating rate is 10-15 °C / min (for example, using a certain temperature range of 550-650 °C as a boundary, 15 °C / min before and 10 °C / min after), and the termination temperature is set to 750-1000 °C, such as 800, 850, or 900 °C. Preferably, the impurity content of each raw material used is not greater than 1 wt%, for example, 0.01 wt%; the container is a high-alumina crucible or a graphite crucible.

[0010] 2) Hold the molten alloy liquid in the furnace at a temperature of about 0.5-5 h, such as 1 h, 2 h, 3 h or 4 h; after holding at a temperature of 0.5-5 h, add the alloy liquid to a mechanical paddle and stir for 5-20 min, such as 7 min, 10 min, 12 min or 15 min.

[0011] 3) Pour the stirred alloy liquid into different molds ranging from room temperature to 600 ℃ and let it solidify.

[0012] 4) After crushing the alloy with a crusher, sieve it (greater than or equal to 100 mesh), such as 100 mesh, 200 mesh, 300 mesh, etc. The obtained sieved alloy powder has low-temperature hydrogen production performance. The alloy powder can be stored for a long time using vacuum packaging.

[0013] To improve the melting effect of the final alloy material and stabilize the hydrolysis hydrogen production reaction, according to the aluminum alloy material of the present invention, preferably, the alloy melting time in step (1) is 0.5-2 h, such as 1 or 1.5 h; preferably, in step (2), the stirring time is 7-15 min; the stirring rate is controlled within 100 r / min, more preferably 40-80 r / min, such as 50, 60 or 70 r / min.

[0014] The beneficial effects of this invention are as follows:

[0015] (1) This invention provides a highly active hydrogen-producing aluminum alloy. The performance of the hydrogen-producing aluminum alloy can be controlled by changing the casting temperature. The specific principle is as follows: as the casting temperature increases, the grain size of the alloy gradually increases, which is not conducive to the hydrolysis reaction of the aluminum alloy; however, the embrittlement effect of liquid metal will increase, making the alloy easier to break, which is conducive to the hydrolysis reaction of the aluminum alloy. Under the combined effect of the two factors, the aluminum alloy block obtained by casting with a mold at 200 °C has the best hydrogen production performance at low temperature.

[0016] (2) The prepared alloy (obtained by casting at 600 ℃) was crushed using a crusher and then sieved (greater than or equal to 100 mesh). The obtained alloy powder can react with ice at -16 ℃ to produce hydrogen, that is, the alloy powder has certain low-temperature hydrogen production performance. The specific principle is: the alloy obtained by casting at 600 ℃ has a higher content of low-melting-point activating components and a more uniform distribution. When the particle size of the reactants is close (about 100 μm), the alloy obtained by casting at 600 ℃ has better hydrogen production performance at low temperature than the alloy obtained by casting at 200 ℃.

[0017] (3) The preparation method of the aluminum alloy hydrogen production material provided by the present invention is simple. Without changing the alloy composition or increasing the preparation cost, the performance can be controlled and optimized by simply changing the temperature of the casting mold, which is conducive to large-scale production. Alloy powder with certain low-temperature reaction performance can be obtained by simple crushing and sieving. Attached Figure Description

[0018] Figure 1 The X-ray diffraction patterns of the Al-Ga-Sn alloys in Examples 1-3 are shown below.

[0019] Figure 2 (ac) and (df) are scanning electron microscope images of Al-Ga-Sn alloys in Examples 1-3 and Comparative Examples 1-3, respectively;

[0020] Figure 3 The graph shows the low-temperature hydrogen production of Al-Ga-Sn alloys in Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0021] The present invention will be described in detail below with reference to embodiments, but the present invention is not limited thereto.

[0022] Examples 1-3, Comparative Examples 1-3

[0023] According to Table 1, Al, Ga, and Sn metal blocks were melted in a stirred furnace filled with nitrogen protective gas at a heating rate of 10-15 °C / min to 800 °C for 1 h. After stirring at 70 r / min for 10 minutes, the mixture was poured into steel molds at different temperatures and allowed to solidify, yielding an Al-Ga-Sn alloy. After cooling, the alloy was either vacuum-packed for later use or crushed using a crusher and passed through a 100-mesh sieve to collect the alloy powder, which was then vacuum-packed for later use.

[0024] (1) The total components and mold temperature are shown in Table 1.

[0025] Table 1. Composition of Al-Ga-Sn ternary alloy

[0026] Example 1 85 10 5 25 powder powder Example 2 85 10 5 200 powder powder powder powder Example 3 85 10 5 600 powder Comparative Example 1 85 10 5 25 block Comparative Example 2 85 10 5 200 block Comparative Example 3 85 10 5 600 block

[0027] (2)Phase of matter

[0028] The X-ray diffraction patterns of the prepared alloys (Examples 1-3) are as follows: Figure 1 As shown, the scanning electron microscope (SEM) images of the Al-Ga-Sn alloys of Examples 1-3 and Comparative Examples 1-3 are as follows: Figure 2 As shown in (ac) and (df);

[0029] according to Figure 1 The XRD patterns of Al-Ga-Sn ternary alloys in Examples 1-7 all contain Al(Ga) solid solution, elemental Sn, and SnO2 phase. Figure 2 As can be seen from (ac), the alloy powder passing through a 100-mesh sieve has a size of approximately 100 μm and exhibits numerous surface cracks. From... Figure 2 As can be seen in (df), numerous cracks exist in the bulk alloy matrix. The size and morphology of the grain boundary phases change with increasing mold temperature. As the mold temperature increases, the size of the grain boundary phases in each alloy increases significantly from a few micrometers to nearly 100 micrometers. The morphology of the grain boundary phases gradually changes from granular to striped, and finally to lamellar.

[0030] (3) Hydrogen production

[0031] The hydrogen production of the alloy powders prepared in Examples 1-3 and the alloy blocks prepared in Comparative Examples 1-3 after reacting with ice at -16 °C for 1 h is as follows: Figure 3 As shown (where the initial temperature of the frozen alloy is -44 ℃), the alloy powder in Example 3, with an initial temperature of room temperature, can generate 14.7 mL of hydrogen gas within 1 h. This indicates that the alloy powder possesses a certain reaction initiation capability at low temperatures and has the potential for online hydrolysis hydrogen supply under low-temperature conditions.

Claims

1. An Al-Ga-Sn alloy for low-temperature hydrogen production, characterized in that: Al-Ga-Sn alloys with different hydrogen production properties were obtained by adjusting the temperature of the casting mold from room temperature to 600°C. The alloys were crushed and sieved using a crusher, and the resulting alloy powder had the ability to react with ice at -16°C. The Al-Ga-Sn alloy comprised 85 wt%-97 wt% aluminum, 2 wt%-14 wt% gallium, and 1-5 wt% tin. The Al-Ga-Sn alloy was prepared through the following steps: (1) Weigh each raw material into a container according to the proportion, and place the container in an atmosphere resistance furnace under nitrogen protection. The heating rate is 10-15℃ / min, and the termination temperature is set to 750-1000℃. (2) Keep the molten alloy liquid in the furnace at a temperature of 0.5-5 h, and then stir the alloy liquid with a mechanical paddle for 5-20 min after holding at the temperature; (3) The stirred alloy liquid is poured into casting molds at different temperatures and solidified. (4) Use a crusher to crush the alloy and then sieve it.

2. The Al-Ga-Sn alloy according to claim 1, characterized in that: The alloy melting time in step (1) is 0.5-2h.

3. The Al-Ga-Sn alloy according to claim 1, characterized in that: In step (2), the stirring time is 5-15 min; the stirring rate is controlled within 100 r / min.

4. The Al-Ga-Sn alloy according to claim 1, characterized in that: In step (3), the temperature of the casting mold is continuously changed from room temperature to 600 ℃.

5. The Al-Ga-Sn alloy according to claim 1, characterized in that: In step (4), the alloy is crushed using a crusher and then passed through a sieve with a mesh size greater than or equal to 100.

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