氣相成長碳纖維(vapor grown carbon fiber, VGCF)在一百年前便開始發展了，然而直到90年代奈米碳管(carbon nanotube, CNT)的出現，則再度引起各界對於VGCF的興趣。因為VGCF的製程方式與CNT非常相似，只需適當地改變一些製程參數即可分別合成出VGCF與CNT。近代由於奈米科技的來臨，因此有了氣相成長奈米碳纖維(vapor grown carbon nanofiber, VGCNF or VGNF)這新稱號。由於VGNF的直徑介在CNT與VGCF之間，所以VGNF同時擁有CNT與VGCF兩者的特性。
　　本研究以流體床法合成奈米碳纖維，實驗主要將重點放在催化劑(或稱觸媒)上，分別以硫化亞鐵與二茂鐵兩種材料作為催化劑。兩種催化劑分別以不同方式來合成奈米碳纖維，硫化亞鐵是以氧化鋁坩堝裝載，直接懸掛在爐體內合成碳纖維；至於二茂鐵則是先以有機溶劑溶解後，再以氫氣或甲烷/氫氣作為承載氣體，以吹氣泡的方式將催化劑由爐外導入爐內合成碳纖維。
　　根據實驗的結果可以知道，以硫化亞鐵合成之碳纖維，其外觀形貌五花八門，而且纖維直徑多為微米級尺度，但是若在坩堝內裝載適量的硫化亞鐵，約在3g以上，而且反應溫度在1179℃~1192℃的範圍內，反應時間在2小時以上，則可以在反應完成後的硫化亞鐵塊表面，得到表面光滑平整的碳纖維；至於以二茂鐵合成之碳纖維，直徑多為奈米級尺度，而且外觀形貌均不像硫化亞鐵所合成之碳纖維那樣地奇特。同時，實驗產物中除了奈米碳纖維之外還有另一產物生成，即碳顆粒。以二茂鐵合成碳纖維的製程中，分別使用甲苯與異丙醇兩種碳氫有機溶液作為合成碳纖維所需之碳源。以甲苯作為碳源所合成之奈米碳纖維，其平均直徑約為218nm，而抗高溫氧化溫度約為595℃；另外以異丙醇作為碳源所合成之奈米碳纖維，其平均直徑約為233nm，而抗高溫氧化溫度約為585℃。由此可知，以甲苯所合成之奈米碳纖維除了直徑較小之外，還擁有較強的抗高溫氧化能力。

　　Vapor grown carbon fibers (VGCF) were found about one hundred year ago. However, recent interest in carbon nanotubes (CNT) has generated renewed interests in VGCF due to the similarities in the growth processes. By simply reducing the growth time, the diameter of carbon fiber can be reduced to form vapor grown carbon nanofibers (VGCNF or VGNF). The diameter of VGNF is between that of VGCF and CNT. This gives VGNFcomparable characterics to VGCF or CNT.
　　In this study, we have used a fluidied bed method to grow VGNF. Ferrous sulfide and ferrocene were used as catalyst precursor. Ferrous sulfide was placed in an Al2O3 crucible which was hanged in the reactor (chamber). On the other hand, ferrocene was dissolved in hydrocarbon solution and introduced into the reactor by bubblering H2 or CH4/H2.
　　VGCF synthesized by using ferrous sulfide as catalyst precursor would have particular morphology and diameter in micrometer scale. However, VGCF with smooth surface would only be obtained from surface of bulk ferrous sulfide under the experimental condition as follows: the addition of ferrous sulfide is more than 3 g and the overall reaction is between 1179℃~1192℃ maintained over 2 hours. On the contrary, VGNF synthesized by using ferrocene as catalyst precursor would have common morphology and diameter in nanometer scale. Besides, carbon particles were also obtained in the same condition. Respectively, toluene and isopropanol serve as both the carbon source for VGNF formation and the solvent for ferrocene. The average diameter of VGNF synthesized by using toluene as carbon source is about 218 nm, and the anti-oxidation temperature is about 595℃. On the other hand, the average diameter of VGNF synthesized by using isopropanol as carbon source is about 233 nm, and the anti-oxidation temperature is about 585℃. Thus, VGNF synthesized by using toluene as carbon source has smaller diameter and higher anti-oxidation temperature.

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