這份研究主要是對本實驗室首度提出以化學方法製造鎳絲進行改進及探討。該方法係使用鎳的鹽類溶液為原料，在鹼性環境下，使用聯氨為還原劑，以及其他必要添加劑（例如PAA及NaBH4），並且在磁場中反應。根據觀察，溶液中的鎳離子首先還原成具有磁性的鎳微粒，這些鎳微粒沿著磁力線排列並互相連結生成絲狀產物。鎳絲的粗細主要受反應速率的影響，反應愈慢產物愈細，而反應速率會隨著pH值的增加而減緩。PAA的存在確保產物不會互相凝聚，但濃度過高亦會影響鎳微粒在軸向的凝聚而生成短棒狀產物。目前藉由不同配方，可生成直徑0.5、1、2μm的鎳絲。NaBH4的添加有助於克服產生新成核點的高活化能，降低反應溫度及時間。透過電性研究，明顯看出鎳絲的導電度會隨著直徑減小而大幅降低，且理論極限值大約只有塊材的30％，這可能是由於硼參雜於鎳絲中，以及鎳金屬氧化的影響。

此外，本研究亦對生成鎳絲的反應機制加以分別探討，透過觀察結果顯示在還原反應中存在兩種鎳的化合物或錯離子，例如Ni(OH)2與Ni(N2H4)32+，並分別進行還原生成金屬鎳。藉由瞭解其個別的反應活化能，可進一步控制反應速率並生成良好絲狀產物。

Abstract
In this work, we tried to improve as well as to understand the chemical method for synthesizing nickel fibers that was first found in our laboratory. The chemical method utilized nickel chloride solution as precursor, hydrazine in an alkaline solution as a reducing agent, and other necessary additives (such as PAA and NaBH4) to obtain the claimed nickel fibers under the influence of magnetic field. According to our observation, the nickel ion was first reduced to form magnetic nickel particles, and then aggregated along the magnetic line of force to form fibrous products. The diameter of the nickel fibers depended mostly on the reaction rate: with a slower reaction rate the diameter became smaller. The reaction rate was slower with increasing pH values. The use of PAA can prevent aggregation of the nickel particles, however, too much PAA would also affect the aggregation along the magnetic line and thus formed rod-like products. By changing the concentration of reactants, we could synthesize nickel fibers of diameters of 0.5, 1, and 2μm. The addition of NaBH4 lowered the activation energy of nucleation and therefore enabled us to obtain nickel fiber at a lower temperature. Electrical conductivity studies showed that these fibers could have at best about 30% of that for bulk nickel material. It was suspected to be caused by the inclusion of boron into the nickel fibers and also the oxidation of the nickel fibers.

In addition, we also discussed the reaction mechanism leading to the formation of nickel fibers. Our results showed that there are two types of nickel compound or complex preceding the chemical reduction, i.e. Ni(OH)2 and Ni(N2H4)32+ and they were reduced independently into nickel. Knowing their individual activation energy, we could have a better control over the reaction rate and thus the characteristics of nickel fibers.

Belloni, J., M. Mostafavi, H. Remita, J. L. Marigniar, and M. O. Delcourt, “Radiation-induced synthesis of mono- and multi-metallic clusters and nanocolloids”, N. J. Chem., 22(11), 1239(1998)

Cardulla, F., “Hydrazine”, J. Chem. Edu., Vol. 60, No. 6(1983)

Cepak, V. M., and C. R. Martin, “Preparation and stability of template-synthesized metal nanorod sols in Organic solvents”, J. Phys. Chem. B, 102, 9985(1998)

Chi, G.J., S.W. Yao, J. Fan, W.G. Zhang, and H.Z. Wang, “Antibacterial activity of anodized aluminum with deposited silver”, Surface and Coatings Tech., 157, 162(2002)

Dhas, N. A., C. P. Raj, and A Gedanken, “Synthesis, Characterization, and Properties of Metallic Copper Nanoparticles”, Chem. Mater., 10, 1446(1998)

Hirai, H., N. Yakura, Y. Seta, and S. Hodoshima, “Characterization of palladium nanoparticles protected with polymers as hydrogeneration catalyst”, Reactive & Functional polymers, 37, 121(1998).

Huang, J. C., “EMI Shielding Plastics: A Review”, Adv. in Polymer Tech., Vol. 14, No. 2, 137(1995)

Knez, M., A. M. Bittner, F. Boes, C. Wege, H. Jeske, E. Maiβ, and K. Kern, “Biotemplate Synthesis of 3-nm Nickel and Cobalt Nanowires”, NANO LETTERS, Vol. 3, No. 8, 1079(2003)
LEE, H. H., H. T. Kuo, and K. S. Chou, “Formation of Crystalline nickel Fibers by Chemical Reduction in the Presence of a Magnetic Field”, J. Chin. Inst. Chem. Engrs., Vol. 34, No 3, 327(2003)

Pradhan, B. K., T. Kyotani, and A. Tomita, “Nickel nanowires of 4 nm diameter if the cavity of carbon nanotubes”, Chem Commum, 1317(1999)

Roosen, A. R., and W. C. Carter, “Simulation of microstructural evolution: anisotropic growth and coarsening”, Physica A, 261, 232（1998）

Shui, X. P., and D. D. L. Chung, “Submicron nickel filaments made by electroplating carbon filaments as a new filler material for electromagnetic interference shielding”, J. Electronic Material, 24(2), 107(1995)

Sloan, J., D. M. Wright, H.G. Woo, S. Bailey, G. Brown, A. P. E. York, K. S. Coleman, J. L. Hutchison, and M. L. H. Green, “Capillary and silver nanowire formation observed in single walled carbon nanotubes”, Chem. Commum 699(1999)

Suzuki, H., N. Fukuzawa, T. Tanigaki, T. Sato,O. Kido, Y. Kimura, and C. Kaito, “Fabrication of an amorphous carbon tube from copper oxide whisker”, J CRYST GROWTH 244 (2), 168（2002）

Vaiu, G., F. Fie’vet-Vincent, and F. Fie’vet, “Nucleation and growth of bimetallic CoNi and FeNi monodisperse particles prepared in polyols”, Solid State Ionics, 84, 259 （1996）

Windholz, M.,S. Budavari, R.F. Blumeti, andE. S. Otterbein, Merk Index, p.932, Merk & CO., Inc., Rahway, NJ, U.S.A.(1983)

Yin, Y., Y. Lu, Y. Sun, and Y. Xia, “Silver nanowires can be directly coated with amorphous silica to generate well-controlled coaxial nanocables of silver/silica”, NANA LETTERS, 2(4) 427(2002)

Yu, K., D. J. Kim, H. S. Chung, and H. Liang, “Dispersed rodlike nickel powder synthesized by modified polyol process”, Mater. Latt., 57, 3992(2003)

Zhang, D., L. Qi, J. Ma, H. Chen, “Formation of silver nanowires in aqueous solution of double-hydrophilic block copolymer”, Chem. Mater. 13, 2753(2001)

Zhang, Q., Y. Li, D. Xu, and Z. Gu, “Preparation of silver nanowire arrays in anodic aluminum oxide template”, J. Material Science Letters, 20, 925(2001)

Zhu, J.Z., Q.F. Qio, H. Wang,J.R. Zhang, J.M. Zhu, and Z.Q. Chen, “Synthesis of silver nanowires by a sonoelectrochemical method”, Inorg. Chem. Commu., 5, 242(2002)

張順吉，“化學還原法製備高轉化率之奈米鎳微粒極其特性探討”，國立清華大學碩士論文（2003）。

郭宏達，“鎳絲的合成及其在電磁波遮蔽材料上的應用”， 國立清華大學碩士論文（2002）。