| Summary: | 碩士 === 逢甲大學 === 材料科學所 === 92 === The method of using alloys to store and carry hydrogen gas is a newly developing technique. Among several types of hydrogen storage alloys, LmNi5 alloys are the most promising due to their easy activation, high absorption/desorption rate, large hydrogen storage capacity and a small hysteresis in equilibrium pressure of hydrogen absorption/desorption.
LmNi5 hydrogen storage alloy presents a high plateau pressure at room temperature. Slight addition of Al element into LmNi5 alloys will reduce the plateau pressure and increase the anti-poisoning. However, addition of Al element will increase the slopes of hydrogen absorption/desorption pressure, reduce hydrogen storage capacity and increase the irreversible hydrogen storage, There features will hinder the alloys hydrogen storage efficiency.
In this experiment, LmNi4.8Al0.2 alloy has been selected as the hydrogen storage material. It’s characteristics of hydrogen storage are investigated. Meanwhile, the anti-poisoning against the CO and H2S impurity gas will also be studied in this paper.
It takes 10 hours for LmNi4.8Al0.2 hydrogen storage alloy to activate at 20℃, and when the temperature rises to 40℃, the activation time is only 1.5 hours. Because the plateau pressure is between 1 and 2atm at room temperature, the LmNi4.8Al0.2 hydrogen storage alloy can directly store the low-pressure hydrogen produced by using the biological technique. If the hydrogen gas comprises the CO or H2S impurity, the alloy’s hydrogen absorption rate reduces apparently. This poisoning phenomenon increases with increasing absorption/desorption cycles and impurity concentration. Increasing the absorption temperature is able to prevent CO and H2S poisoning, but higher temperature may reduce the hydrogen storage capacity, increase the hydrogen dissociation pressure and exhibit a slower hydrogen absorption rate. By absorbing high purity hydrogen and then desorbing at a high temperature, the activity of poisoned alloy would be effectively recovered.
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