石墨包裹奈米鐵晶粒的合成方法改進研究：石墨坩堝設計

An Improved Synthesis Method for Graphite Encapsulated Iron Nanoparticles—Graphite Crucible Design

羅仁傑(Jen-Chieh Lo)

指導教授 ： 鄧茂華

國立臺灣大學/理學院/地質科學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.10137

摘要

石墨包裹奈米金屬晶粒(GEM)是一種複合材料。其顆粒粒徑約介於10到100 nm間，內核為金屬，外層有數層石墨層包裹。藉由石墨層的保護，GEM可以不受到氧化、強酸、強鹼的破壞，並且保有內核之鐵磁性金屬的磁性質。此種材料不單具有科學研究的價值，並且在各領域都有極高的應用潛力。先前研究指出，在燃料電池領域中，Co-GEM已證實是具有高儲氫能力的奈米材料。而Fe-GEM因其具有生物相容性，已有國內外研究團隊證實Fe-GEM可用於癌症的熱治療療程中。在國防工業上，利用Fe-GEM可吸收電磁波的物理特性，可能可以被應用在隱形戰機表面的吸波鍍膜上。總而言之，Fe-GEM是一種具有多種潛能的奈米材料。
但Fe-GEM的製造具有多重難度。舉例來說，若在製程中，產物有未被包裹完全的奈米鐵顆粒，則在接觸空氣時，會由於奈米鐵顆粒的高活性而自燃，產生出的反應熱會將被包裹的Fe-GEM一起燃燒殆盡。全球目前已有數個分別在美國、日本、歐洲、中國大陸、韓國等地的研究團隊可以成功合成出Fe-GEM，可惜產量均低，僅能供精密儀器分析，而無法發揮其應用潛能。本研究之目的就是探討如何大量增加Fe-GEM的產量和產率，使此種材料更有機會一展所長。
本研究利用特為製造GEM材料而設計的鎢電弧法來合成Fe-GEM，透過改變石墨坩堝的設計，加入陶瓷片提昇熱效率，成功增加了初產物的產量。但在初產物中，並非完全都是包裹完整的奈米顆粒，而是碳雜質、未包裹完全的奈米鐵顆粒和Fe-GEM的混合物。為提昇產物包裹的完整性，本研究改變實驗中各項參數，以及將初產物在還原氣氛中退火，以此提昇包裹率。

關鍵字

石墨 ； 包裹 ； 鐵 ； 奈米晶粒

並列摘要

Graphite encapsulated metal (GEM) nanopartcle is a composite material, with a core-shell structured and a particle size between 10 to 100 nm in diameter. By the protection of outer graphite shell, the inner metal core can survive in severe environments, such as oxidation and acid erosion. This material provides not only an excellent chance to study the properties and behaviors of nanoparticles and nano-sized graphite, but also many potential opportunities in industrial applications. In fuel cells, Co-GEM has been proven to be an effective hydrogen storage material. In biomedical applications, Fe-GEM can be used as thermoseeds of hyperthermia in cancer therapy. And in military, Fe-GEM could be important due to its microwave absorbency. Summarily, Fe-GEM is a highly potential material with numerous implementations.
But there are several difficulties in the production of Fe-GEM. For example, iron nanoparticle has serious problem of spontaneous combustion when exposing the air or oxygen including environments. Few of research teams in North America, Japan, Poland, China, and Korea had successfully synthesized Fe-GEM, but no one can massively produce Fe-GEM. The purpose of this study is to increase not only production rate, but also encapsulation efficiency of Fe-GEM.
A tungsten arc-discharge method has been used to massively synthesize GEM materials. The heat transfer efficiency of the arc system had been increased by a new designed graphite crucible with ceramic layer in it. So the production rate of as-made products had been increased as well. The as-made products, however, are not pure final GEM material, but a mixture of GEM, ill-encapsulated iron nanoparticles, and carbon debris. Though the as-made product can be purified by strong acid bath and strong magnetic field separation, the synthesis efficiency, i.e. the amount of GEM, is far from enough for further research. To increase the efficiency, we have redesigned the experiment process and greatly improved the encapsulation of iron nanoparticles, and thus increased the Fe-GEM product. The as-made product was then annealed in an Ar/H2 atmosphere before the usual acid bath and magnetic separation treatments on the purpose of encapsulation increase. The newly improved synthesis method proved to be very effective and may lead to many new discoveries and applications in near future.

並列關鍵字

Graphite ； encapsulation ； iron ； nanoparticles.

參考文獻

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