【摘要】：鎂基儲氫材料以其儲氫量高(7.6wt.%)、資源豐富、成本低廉的特點,被認為是最具有發(fā)展前景的儲氫材料之一,但是其高的吸放氫溫度、緩慢的吸放氫動力學性能阻礙了它的實際工業(yè)化應(yīng)用。本文以Mg粉為初始原料研究了高溫高壓氫化工藝對樣品中Mg H2含量的影響,進一步選擇Cs F、Ti C、Ni F2對Mg H2進行復相球磨改性,此外,還研究了Mg H2+Li Al H4復合體系的放氫性能。本文利用p-C-T測試儀在高溫高壓的條件下制備得到了Mg H2儲氫合金。確定了較優(yōu)的制備工藝,Mg粉的球磨參數(shù)為:球料比40:1,轉(zhuǎn)速300r/min,球磨時間6h,氬氣;氫化參數(shù):氫壓4MPa,溫度653K,兩次氫化時間分別為48h、24h。通過分析發(fā)現(xiàn)采用上述工藝制備得到的樣品中Mg H2的含量達到了98wt.%左右。進一步通過復相球磨的方式制備得到了Mg H2+M(M:Cs F、Ti C、Ni F2)的儲氫試樣。吸放氫性能及XRD測試結(jié)果表明,三種添加物對Mg H2的吸放氫動力學性能均有很好的催化促進作用,但其催化的機理不盡相同。Ti C在系統(tǒng)的吸放氫過程穩(wěn)定存在,沒有與基質(zhì)Mg H2發(fā)生反應(yīng),是以傳統(tǒng)催化劑的形式對Mg H2產(chǎn)生了表面改性的效果,從而提高了Mg H2的吸放氫性能。而Cs F、Ni F2則是因為在吸放氫過程中分別與基體發(fā)生了2Cs F+Mg H2→2Cs H+Mg F2、Ni F2?4H2O+7Mg H2→Mg2Ni H4+Mg F2+4Mg O+9H2的反應(yīng),從而促進了Mg H2的吸放氫過程。對于Cs F和Ti C,均在添加量為5wt.%時表現(xiàn)出最好的催化效果,而Ni F2添加2wt.%時性能較好。綜合比較,其中Cs F的催化作用較為突出,當其添加量在5wt.%時,573K下的放氫量達到了7.06wt.%,可逆吸氫容量為7.09wt.%,在473K時的吸氫量也達到了6.33wt.%。同樣采用球磨的方式制備的Mg H2+Li Al H4、Mg H2+Li Al H4+5wt.%Ti C復合體系,其放氫性能測試及XRD結(jié)果表明,Mg H2+Li Al H4的放氫性能明顯優(yōu)于Mg H2,Mg H2+Li Al H4在較低溫度(473K以下)時,只表現(xiàn)為Li Al H4的單方面放氫行為,當溫度達到523K時產(chǎn)生了協(xié)同放氫效應(yīng),這一協(xié)同效應(yīng)表現(xiàn)為Li Al H4分解產(chǎn)生的Al原子降低了Mg H2的穩(wěn)定性,產(chǎn)生了兩種新相Mg2Al3和Mg17Al12,從而改變了Mg H2放氫過程;在Mg H2+Li Al H4的基礎(chǔ)上添加Ti C所帶來的細化作用,增加了Mg H2與Li Al H4之間的相界面,有利于它們之間的這種協(xié)同放氫效應(yīng),進一步提高了系統(tǒng)的放氫動力學性能。
[Abstract]:Magnesium based hydrogen storage materials are considered as one of the most promising hydrogen storage materials due to their high hydrogen storage capacity (7.6 wt.%), rich resources and low cost, but their high hydrogen absorption and desorption temperatures. The slow kinetics of hydrogen absorption and desorption hinders its practical industrial application. In this paper, the effect of high temperature and high pressure hydrogenation on the content of Mg H2 in the sample was studied by using Mg powder as the initial raw material. Furthermore, the Cs FFU Ti Ni F 2 was selected to modify Mg H2 by multiphase ball milling. The hydrogen desorption properties of Mg H2 Li Al H 4 composite system were also studied. In this paper, Mg H2 hydrogen storage alloys were prepared by using p-C-T tester under high temperature and high pressure. The optimum preparation process was determined. The milling parameters of Mg powder were as follows: ratio of ball to material 40: 1, rotational speed 300 r / min, milling time 6 h, argon gas, hydrogenation parameter: hydrogen pressure 4 MPA, temperature 653 K, twice hydrogenation time 48 h and 24 h, respectively. It is found that the content of Mg H2 in the sample prepared by the above process is about 98 wt.%. Furthermore, the hydrogen storage samples of Mg H 2M (M:Cs FN Ti Ni F 2) were prepared by multiphase ball milling. The results of hydrogen absorption and desorption and XRD test showed that the three additives had a good catalytic effect on the hydrogen absorption and desorption kinetics of Mg H2, but the mechanism of their catalytic mechanism was different, and. Ti C existed stably in the process of hydrogen absorption and desorption. There was no reaction with Mg H2, which resulted in the surface modification of Mg H2 in the form of traditional catalyst, which improved the hydrogen absorption and desorption performance of Mg H2. However, the reaction of 2Cs F Mg H 2 + 2Cs H Mg F 2N Ni F2?4H2O 7Mg H 2 Mg2Ni H 4 Mg F 2 4Mg O 9H2 with the matrix occurred during the hydrogen absorption and desorption process of Cs F 2 Ni F 2, which promoted the hydrogen absorption and desorption process of Mg H 2. For Cs F and Ti C, both showed the best catalytic effect at the addition amount of 5wt.%, while the performance of Ni F2 was better when adding 2wt.%. Compared with each other, the catalytic activity of Cs F is more prominent. When the addition amount of Cs F is 5 wt.%, the hydrogen release capacity at 573K reaches 7.06wt.and the reversible hydrogen absorption capacity is 7.09wt.and the hydrogen absorption capacity at 473K reaches 6.33wt. The hydrogen release properties of Mg H 2 Li Al H 4 O mg H 2 Li Al H 4 5wt.%Ti C prepared by ball milling were tested and XRD results showed that Mg H 2 Li Al H 4 was superior to Mg H 2. At low temperature (under 473K), Mg H _ 2 Li Al H _ 4 exhibits only the unilateral hydrogen release behavior of Li Al H _ 4. When the temperature reaches 523K, there is a synergistic hydrogen release effect. The synergistic effect is that the Al atoms produced by the decomposition of Li Al H4 decrease the stability of Mg H2, and produce two new phases, Mg2Al3 and Mg17Al12, which change the process of Mg H2 dehydrogenation. The addition of Ti C on the basis of Mg H2 Li Al H4 increases the phase interface between Mg H2 and Li Al H4, which is beneficial to the synergistic dehydrogenation effect between Mg H2 and Li Al H4, and further improves the dehydrogenation kinetics of the system.
【學位授予單位】：重慶大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB34

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