| DC 欄位 |
值 |
語言 |
| DC.contributor | 機械工程學系 | zh_TW |
| DC.creator | 蔡宇洲 | zh_TW |
| DC.creator | Yu-Chou Tsai | en_US |
| dc.date.accessioned | 2010-7-22T07:39:07Z | |
| dc.date.available | 2010-7-22T07:39:07Z | |
| dc.date.issued | 2010 | |
| dc.identifier.uri | http://ir.lib.ncu.edu.tw:88/thesis/view_etd.asp?URN=953403015 | |
| dc.contributor.department | 機械工程學系 | zh_TW |
| DC.description | 國立中央大學 | zh_TW |
| DC.description | National Central University | en_US |
| dc.description.abstract | Li基複合儲氫材料(Li-based complex hydrides)一直被視為相當具有實用化潛力之新型固態儲氫材料。然而，以往在製備Li基複合儲氫材料時所使用之方法不僅產量小、雜質含量高且製程複雜、耗時較久，使得Li基複合儲氫材料之研究受到阻礙。因此，本論文研究以熔煉之方式製備Li基複合儲氫材料，但因Li活性相當大且易揮發之特性，使傳統熔煉法難以準確熔配出所需化學計量比之Li基複合儲氫材料。故此，本論文研發一階段式氣氛熔煉法(Step-Controlled Casting Process, SCCP)搭配自行設計之階段式氣氛熔煉爐(Step- Controlled Atmosphere furnace, SCA furnace)製備各式Li基複合儲氫材料並研究其儲氫性質。
本研究以階段式氣氛熔煉法搭配本實驗室自行研發之恆溫揮發熔煉法(Isothermal Evaporation Casting Process, IECP)用以製備LiAl、Al4Li9、Li3N、Li-Mg-N及Li3AlN2等Li基複合儲氫材料，並以光學顯微鏡、電子顯微鏡、X-ray繞射儀及ICP-AES等儀器進行微結構觀察與成份分析，結合活化程序及TPH/TPD進行儲氫性質之研究。
實驗結果顯示，本研究所開發之階段式氣氛熔煉法用以熔配Li基複合儲氫材料，可快速、大量合成高純度之LiAl合金，而LiAl合金經過10小時球磨後，在400℃、65大氣壓下氫化24小時可完全氫化形成LiH及Al，其放氫量可達2.40wt.%；且在經過TPD放氫後可逆回復至LiAl合金。在LiAl合金中添加4wt.%TiFe可有效的促進放氫反應之進行，放氫比例由84%提升至87%，放氫量亦由2.40提升至2.50wt.%。為提升儲氫量而熔配出高Li含量之Al4Li9合金，經過初始吸放氫循環後會形成LiAl合金及殘留有Li，而非可逆回復至Al4Li9合金，此外，殘留之Li會形成Li2O及LiOH而造成儲氫量之下降，故Al4Li9合金並不適合取代LiAl合金作為複合儲氫材料。
本研究以恆溫揮發熔煉法熔配出之Li3N複合儲氫材料，除因取料時所產生之些許雜質外，為一相當均質之α-Li3N複合儲氫材料。將其製程搭配階段式氣氛熔煉之概念，即可在不取出α-Li3N之情形下添加Mg及Al塊使其形成Li-Mg-N及Li3AlN2。研究結果顯示，以此製程熔配出之Li3AlN2成分相當準確且均質，但其在400℃、65大氣壓下氫化24小時卻僅有0.4wt.%之放氫量，與文獻中所述之非氫化相合成之Li3AlN2複合儲氫材料幾乎不具有儲放氫性質之結果相符。而以此製程製備出以LiMgN為主之Li-Mg-N複合儲氫材料，成分雖尚不均質，但卻具有3.56wt.%之放氫量，且能從50℃起即開始放氫，具有相當優良之儲氫性質。
| zh_TW |
| dc.description.abstract | Li-based complex hydrides have received considerable attention as some of the most potential hydrogen storage materials due to their light weight and high hydrogen content. For the production of Li-based complex hydrides, several methods have been developed. However, all of the methods have very complicated processes or using kinds of catalysts, so that they are restricted to obtain pure and homogeneous Li-based complex hydrides for mass production. In order to overcome the disadvantages of the Li-based complex hydrides production methods, this study develops a novel procedure, Step-Controlled Casting Process (SCCP), for mass production of Li-based complex hydrides rapidly.
This study combines the concepts of step-controlled casting process with isothermal evaporation casting process (IECP) to produce Li-based complex hydrides, like LiAl, Al4Li9, Li3N, Li3AlN2 and Li-Mg-N complex hydrides. To evaluate the chemical compositions and microstructures of the Li-based complex hydrides fabricated by SCCP combined with IECP, optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and inductivity coupled plasma–atomic emission spectroscopy (ICP-AES) are used. Otherwise, temperature programmed decomposition (TPD) is used to investigate the dehydrogenation properties of the activated Li-based complex hydrides.
The results of this study reveal that a high purity LiAl alloy without any impurity is produced by SCCP. According to the results of TPD and XRD, they can be observed that both of as-cast and ball milled LiAl alloys have reversibility which can return to the initial state. The highest dehydrogenation capacity of 2.40 wt.% can be obtained from the ball milled LiAl alloy hydrogenated under 65 atm at 400℃ for 24 hrs. The dehydrogenation capacity of LiAl alloy doped with 4wt.% TiFe is markedly higher than that of the samples doped with LaNi5 or Mg2Ni and its dehydrogenation fraction is raised from 84% of the ball-milled LiAl alloy to 87%. Al4Li9 alloy is produced in order to raise the hydrogen storage capacity because of its higher Li content. However, it transforms to LiAl and Li instead of Al4Li9 after dehydrogenation. In other words, Al4Li9 alloy is not suitable to replace LiAl alloy as a potential complex hydride.
The Li3N fabricated by IECP in this study is a homogeneous α-Li3N which only contents minor impurity generated during getting materials. The combination of SCCP with IECP can produce Li3AlN2 and Li-Mg-N complex hydrides without taking the formative α-Li3N out of the SCA furnace in order to prevent from the formation of oxides. This procedure can fabricate a high purity Li3AlN2, but it only releases 0.4wt.% hydrogen after hydrogenation under 65 atm at 400℃ for 24 hrs. This result conforms to the published paper which considers that Li3AlN2 can’t store hydrogen if it is synthesized by non-hydride materials. The Li-Mg-N complex hydride manufactured by this composite procedure is non-homogeneous, but it can dehydrogenated from 50℃ and the dehydrogenation capacity of it reaches to 3.56wt.%.
| en_US |
| DC.subject | 階段式氣氛熔煉法 | zh_TW |
| DC.subject | Li基複合儲氫材料 | zh_TW |
| DC.subject | Li3N | zh_TW |
| DC.subject | Li3AlN2 | zh_TW |
| DC.subject | LiMgN | zh_TW |
| DC.subject | LiMgN | en_US |
| DC.subject | Li3AlN2 | en_US |
| DC.subject | Li3N | en_US |
| DC.subject | step-controlled casting process (SCCP) | en_US |
| DC.subject | Li-based complex hydrides | en_US |
| DC.title | 鋰-鋁基及鋰-氮基複合儲氫材料之製程開發及研究 | zh_TW |
| dc.language.iso | zh-TW | zh-TW |
| DC.title | Research and fabricating process development of Li-Al based and Li-N based complex hydrides | en_US |
| DC.type | 博碩士論文 | zh_TW |
| DC.type | thesis | en_US |
| DC.publisher | National Central University | en_US |