5. 結果與討論
5.10. 論文發表與專利申請
本計畫部分成果已整理並撰寫為學術論文並投稿與發表於國際學術期刊，參與學生也完 成三份碩士論文以及發表於國內研討會。目前仍有一位同學將再完成投稿國際論文與完成碩 士論文。另一方面，本計畫的部分成果具有潛力提供工業應用，因此目前申請兩篇國內專利，
以及一篇美國專利。上述論文與專利資訊如下:
5.10.1. 專利申請
1. Shyankay Jou, and Dong-Yu Yeh, “Method of Fabricating One-dimensional Metallic Nanostructure”, US Patent Application No. 11939341. [附件一]
2. 周賢鎧，葉東育，「一維金屬奈米級結構的製造方法」，中華民國專利，國立臺灣科技
大學專利申請字號 0960041TW。[附件一]
3. 周賢鎧，廖勝權，「多孔性網狀金屬的製造方法」，中華民國專利，國立臺灣科技大學專 利申請字號 0960072TW。[附件二]
5.10.2. SCI 期刊論文
1. Shyankay Jou(周賢鎧), Dong-Yu Yeh(葉東育), and Ampere Tseng(曾安培), “Nickel Nanorods Produced by Annealing Composite Oxide Films”,
Journal of Nanoscience and Nanotechnology 8 (2008) 1-3. [附件三]
1. Tzu-Hui Wu(吳姿慧) and Shyankay Jou(周賢鎧),“Thin porous Ni-YSZ films as anode for solid oxidefuelcell”, Journal of Physics and Chemistry of Solids (submitted) [附件四]
3. 以奈米孔隙之 Ni-8YSZ 陽極用於 Ni-YSZ/YSZ/LSMO 燃料電池元件，以單氣室系統以 及以甲烷為燃料進行電池量測，結果驗證本計畫開發之薄膜電極於適當厚度下，電池
參考文獻
[1] S. H. Haile, “Fuel cell materials and component,”Acta Mater. 51 (2003) 5981.
[2] W. Z. Zhu and S. C. Deevi, “A review on the anode materials for solid oxide fuel cells,”Mater.
Sci. Eng. A 362 (2003) 228.
[3] F. H. Wang, R. S. Guo, Q. T. Wei, Y. Zhou, H. L. Li and S. L. Li, “Preparation of Ni/YSZ anode by coating procipitation method,”Mater. Lett. 58 (2004) 3079.
[4] X. Huang, Z. Liu, Z. Lu, L. Pei, R. Zhu, Y. Liu, J. Miao, Z. Zhang and W. Su, “A Ni/YSZ composite containing Ce0.9Ca0.1O2-δparticles as an anode for SOFCs,”J. Phys. Chem. Solids 64 (2003) 2379.
[5] D. Rotureau, J.-P. Vircelle, C. Pijolat, N. Caillol and M. Pijolat, J. Eur. Ceram. Soc. 25 (2005) 2633.
[6] T. Hibino, A. Hashimoto, T. Inoue, J.-I. Tokuno, S.-I. Yoshida and M. Sano, Science 288 (2031.
[7] D. Kek, P. Panjan, E. Wanzenberg and J. Jamnik, “Electrical and microstructural investigation of cermet anode/YSZ thin film system,”J. Eur. Ceram. Soc. 21 (2001) 1861.
[8] J. L. Hertz and H. L. Tuller, J. Electroceram. 13 (2004) 663.
[9] A. Bieberle, L. P. Meier and L. G. Gauckler, J. Electrochem. Soc. 1486 (2001) A646.
[10] P. Costamagna, P. Costa and V. Antonucci, Electrochim. Acta 43 (1998) 375.
[11] S.Jou and K.C.Hsu,“MesoporousPtElectrodePreparation Using SputterDeposition and Reduction Treatment,”J. Appl. Electrochem., (in revision)
[12] 王貞芮，「添加銅之二氧化矽複合薄膜之研究」，國立台灣科技大學碩士論文 (2005)。
可供推廣之研發成果資料表
■ 可申請專利 □ 可技術移轉 日期：96 年 12 月 31 日
國科會補助計畫
計畫名稱：先進固態氧化物燃料電池材料界面反應與匹配性研究—
子計畫一：以濺鍍法形成陶金電極之微結構與型態研究
計畫主持人： 周賢鎧
計畫編號：NSC 93－2218－E－011－097 NSC 94－2218－E－011－004
NSC 95－2218－E－011－004 學門領域：材料
技術/創作名稱 一維金屬奈米級結構的製造方法 發明人/創作人 周賢鎧，葉東育
中文：
本方法用於形成奈米等級寬度的金屬線，先製作或取得均勻混合的 兩種氧化物，將該混合氧化物於含氫氣氣氛中加熱，使其中一種氧 化物還原成金屬狀態，並具有奈米等級寬度。
技術說明
英文：Provided is a method to generate metals nanowires. A mixture of oxides is employed as precursor that is heated in a hydrogen-containing atmosphere. One of the oxides in the mixture is reduced to its metal form with a lateral dimension of nanometers.
可利用之產業 及 可開發之產品
燃料電池電極、自旋電子產品、巨磁阻產品、電磁波遮蔽產品、奈 米電子產品、觸媒、感測器
技術特點
奈米結構、整合製程推廣及運用的價值
燃料電池、氣體感測器、觸媒※ 1.每項研發成果請填寫一式二份，一份隨成果報告送繳本會，一份送 貴單位研
發成果推廣單位（如技術移轉中心）。
※ 2.本項研發成果若尚未申請專利，請勿揭露可申請專利之主要內容。
※ 3.本表若不敷使用，請自行影印使用。
附件一
可供推廣之研發成果資料表
Provided is a fabrication method, which uses oxide wires of few nanometers to hundreds of nanometers in lateral size or porous oxide powders with pores of tens of nanometers as raw materials, to generate interconnected metal networks with continuous pores, after the oxide wires or powders were annealed in an atmosphere containing
hydrogen.
Nickel Nanorods Produced by Annealing Composite Oxide Films Shyankay Jou1, Dong-Yu Yeh1, and Ampere A. Tseng1,2 *†
1Graduate Institute of Materials Science and Technology, National Taiwan University of Science and Technology, Taipei, Taiwan 10672 ROC
2Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona 85287-6106 USA.
Received 20 June 2007; accepted 17 December 2007 __
*Author to whom correspondence should be addressed: E-mail: [email protected]; Fax: (480) 965-1384.
†On sabbatical leave from Arizona State University, Tempe, Arizona, 85287
ABSTRACT
Nickel nanorods have been produced by annealing a dense composite film. The nanorods of 45-140 nm in lateral dimensions and 230-1400 nm in longitudinal dimensions were obtained by annealing NiO-YSZ composite films in H2at 800 °C for one hour. The axis of the nanorods at the
<220> direction was observed. The dense NiO-YSZ composite film was originally created by co-sputtering Ni and Zr-Y-Ce targets in Ar and O2environment at 350C. Reduction of NiOxto Ni nuclei takes place on the surface of the film. The low crystallinity of the original composite film is believed to facilitate the NiO to grow into Ni nanorods on the discrete Ni seeds by diffusion.
Keywords: Nickel; nanorods; nanowire; oxide film; reduction 附件三
1. INTRODUCTION
One-dimensional nanostructures, including nanotubes, nanowires, nanorods and nanocones of diverse materials, have been receiving extensive interest due to their unique properties.1,2 A great many of techniques have been developed to produce a wide range of nano-scaled structures, from carbon nanotubes to oxides and to metallic and semiconductor nanostructures.1-4 Several processes have been developed on producing metallic nanowires and nanorods.1,2 However, these processes involve multiple steps and require many facilities. This paper provides a simple but versatile approach to generate metallic nanorods.
The processes used for producing metallic nanowires or nanorods include using nanoporous materials or carbon nanotubes as templates for growing metallic nanowires,1,2 using a polyol or a micellar medium for forming one-dimensional precursors and then reducing the precursors for making metallic nanowires, using chemical and hydrothermal reduction of precursors in solutions, and using H2 reduction of dry precursors.2 Also, metallic nanowires, especially Zn nanowires, were generated by condensing vapor to solid (VS),5,6 while direct deposition of Ag nanorods was achieved by employing an oblique angle deposition of Ag with self-shadowed effect.7 Furthermore, metal nanowires have been generated by surface treatment of bulk metal. Lee et al.8 treated a W film in a mixture of H2 and Ar at 850 °C to generate W nanowires by means of a self-catalyzed reaction, while trace of O2 would help forming W nanowires, but oxide nanowires would be generated in the presence of O2 gas.9,10 W nanowires were also generated by depositing tungsten oxide above oxide’s decomposition temperature.11
In this paper, as an alternative, we present a simple method in the generation of nickel nanorods without a template or an intermediate step as compared to those techniques discussed above in the forming of metallic nanorods. The Ni nanorods were directly obtained by annealing the NiO-YSZ composite films in H2 at 800 °C. This method is expected to be used to prepare other metallic nanorods, facilitating a variety of applications.
2. EXPERIMENT
The original NiO-YSZ composite film was created by a mixture of NiO and CeO2-doped YSZ, which were deposited on thermal-oxide-coated Si(100) substrates by using reactive co-sputtering of a Ni and a Zr-Y-Ce targets in a gas mixture of argon (10 sccm) and oxygen (10 sccm). Working and base pressures for the sputtering process were 2.4 Pa and 6.7×10-4Pa, respectively. The composite oxide film was then annealed in 20 vol.% H2-80 vol.% Ar in a quartz tube furnace at 800 °C for 1 h.
H2reduction was employed to convert NiO-YSZ to Ni-YSZ. However, Ni nanorods were produced on surface of the films.
3. RESULTS AND DISCUSSIONS
Morphology and structure of the as-deposited (Fig. 1a) and annealed films (Fig. 1b) were first inspected using scanning electron microscopy (SEM). As-deposited composite oxide film has dense columnar structure, as shown in Fig. 1(a), while Fig. 1(b) shows nanorods are grown on the top of a porous film after annealing. These nanorods are 45 to 140 nm in width and 230 nm to 1.4
m in length. Grains of 60 to 200 nm in size are also present on surface of the porous film.
X-ray diffraction (XRD) was also used to study the composition and crystal structure of the nanostructures after and before annealing. XRD spectra were taken at a glancing angle of 5°. As shown in the upper XRD spectra in Fig. 2, the nanorod-containing film is composed of Ni and YSZ phases, while the lower one is the XRD spectra of the as-deposited films. The as-deposited oxide film has low crystallinity, and two broad peaks should represent NiO (111) and (200) reflections in a stressed state. According to the XRD spectra, NiO in the composite oxide film is reduced to form Ni crystals, while the YSZ remains as oxide, after the H2-annealing. Ni nanorods on the surface of
the film are obtained from the oxide film with a relatively low crystallinity
Figure 3(a) presents a TEM image of straight nanorods obtained from above specimen. Figure 3(b) is an enlarged image of a nanorod. Inset in Fig. 3(b) shows an electron diffraction pattern of this nanorod. The diffraction pattern represents [
1 1 2
] zone of Ni cubic crystal with a lattice constant of 0.35 nm. Direction of the [220] (the arrow direction shown in the insert) is parallel to the axis of this nanorod. As a result, nanorods of Ni crystal are produced by annealing aNiO-containing oxide mixture in a H2atmosphere. Reducing NiO to Ni should take place on surface where NiO and H2meet. Ni nuclei are formed on the surface of the film, facilitating subsequent growth of the Ni crystal. Both NiO and Ni clusters are not soluble in YSZ, thus phase separation will occur and NiOxor Ni species will migrate. The as-deposited composite oxide film is uniform and without pore. Reduction would take place when Ni or NiOxdiffuses from inner to free surface of the oxide film.
These largely single-crystal Ni nanorods produced by the present one-step annealing process should have relative low resistivities, less than 10- cm and remarkably high failure density, larger than 108Acm-2.12These Ni nanorods should be an ideal electrode providing necessary electric contact to many different nanodevices for the critic first step towards integration of these
nanodevices. These nanorods should also possess anisotropic magnetoresistance, field emission, quantized conduction and optical limiting properties as those metal nanowires prepared from other processes.2,13-15 Quantification of these material properties is currently under investigation. The effects of the composition of the NiO-YSZ composite films on the geometry, sizes and density of nanorods will also be examined.
4. CONCLUSION
Using an annealing process in a H2atmosphere, Ni nanorods were produced from a NiO-containing oxide mixture. The Ni nanorod is single crystal with growth direction along [220]. It is
believed that reducing NiO to Ni takes place on the surface of oxide mixture and facilitates growth of Ni nanorods. This method should be able to be applied for creating other metallic nanorods and facilitating a variety of applications.
ACKNOWLEDGEMENTS:
This work was supported by the ROC National Science Council through Grant No.
95-2218-E-011-004. National Taiwan University of Science and Technology is acknowledged for providing the University Chair Professorship to the third author during preparing this article. The authors also thank Mr. S. C. Liao for his technical support on transmission electron microscopy.
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Fig. 1. Cross-sectional SEM images of NiO-YSZ films (a) before and (b) after annealed in a mixture of H2and Ar at 800 °C for 1 h.
Fig. 2. XRD spectra of mixtures of NiO and YSZ (lower spectra).: the upper spectra are XRD spectra of mixtures of Ni and YSZ obtained after H2annealing.
Fig. 3. TEM images of Ni nanorods.: (a) low magnification; (b) high magnification. Inset in (b) is the diffraction pattern of the Ni nanorod showing [
1 1 2
] zone.Thin porous Ni-YSZ films as anode for solid oxide fuel cell Shyankay Jou* and Tzu-Hui Wu
Graduate Institute of Materials Science and Technology, National Taiwan University of Science and Technology, Taipei 10672, Taiwan, R. O. C.
Abstract
Porous Ni-YSZ films were fabricated by reactive co-sputtering of a Ni and a Zr-Y target followed by sequentially annealing in air at 900 °C and in a vacuum at 800 °C. The Ni-YSZ films
comprised small grains and pores that were tens of nanometers in sizes. The porous Ni-YSZ films were used as the anode on one side of an YSZ electrolyte disc and a La0.7Sr0.3MnO3thick film was used as the cathode on the other side of the disc to form solid oxide fuel cells (SOFCs). The voltage-current curves of the SOFCs with single- and a triple-layered porous anodes were measured in a single chamber configuration, in a mixture of CH4and air (CH4: O2volume ratio = 2:1). The maximum power density of the SOFC using the single-layered porous Ni-YSZ thin films as the anode was 0.38 mW cm-2, which was lower than that of 0.76 mW cm-2, obtained using a
screen-printed Ni-YSZ thick anode. The maximum power density of the SOFC with a thin anode was increased, but fluctuated between 0.6 and 1.14 mW cm-2when a triple-layered porous Ni-YSZ anode was used.
Keywords: Annealing; electrochemical properties; microporous materials; sputtering
*Corresponding author. Tel: +886-2-27376665; fax: +886-2-27301265 E-mail address: [email protected] (S. Jou)
附件四
1. Introduction
Planar solid oxide fuel cells (SOFCs) have been developed for potential use in portable power devices [1-5]. SOFCs have a sandwiched cathode/electrolyte/anode structure. The power
efficiency of fuel cells depends on the resistive and polarization losses that generally are incurred in the fuel cells. Reducing the thickness of the electrolyte increases the power efficiency and reduces the operating temperature of the SOFCs because of the reduction of the resistive loss across the electrolyte [1]. Using a porous cermet electrode with a large three-phase-boundary (TPB) can reduce the loss of activation polarization and improve cell performance [6]. The porous structure of the cermet electrodes facilitates electrochemical reactions at the TPB where the gases, electrolyte and the electrode meet [7]. Conventional SOFCs use dense yttria-stabilized zirconia (YSZ) as the electrolyte, porous nickel (Ni)-YSZ cermet as the anode, and porous strontium-doped lanthanum manganite (LSM) as the cathode [1]. Two stack structures are used in the planar SOFCs [8].
One is that of the electrolyte-supported SOFC and comprises an electrolyte disc of thickness of 50 to 150 μm, with the two sides coated separately with anode and cathode films. The other is that of the electrode-supported SOFC comprising a thick anode or cathode disc with a thickness of a few hundred micrometers, and an electrolyte film with a thickness of 5 to 20 μm.
In electrolyte-supported SOFCs, the thick porous Ni-YSZ anodes are fabricated by the screen printing, tape casting or spray coating of mixtures of NiO and YSZ powders, followed by sintering in air and further reduction in diluted hydrogen [2,4,8,9]. Large YSZ powders are used in the NiO-YSZ ink or slurry to produce a rigid porous microstructure of the Ni-YSZ anode with large grains following sintering. The size of the pores thus produced in the Ni-YSZ anode is in the micrometer range, allowing gases to diffuse through. Yet the Ni-YSZ anode with large YSZ grains reduces the TPB length and causes a loss of electrochemical activity because of the agglomeration of Ni particles at high temperatures [10-12]. The issue of the Ni agglomeration can be minimized by introducing fine YSZ particles in the Ni-YSZ anode [13]. A stable, high-performance porous Ni-YSZ anode has been produced using a mixture of coarse (tens of micrometers) and fine (below one micrometer) particles, to form an entangled YSZ frame and Ni network with large TPB [14].
Various approaches have been employed to increase the TPB and to improve the performance of SOFCs by modifying the porous microstructure with nano-sized substances [15-21]. For instance, cermet anodes can be produced by impregnating a porous Ni frame with ceramic precursors or nano-sized suspensions, or by impregnating a porous YSZ frame with precursors of metal salts, followed by post-annealing [15-17]. A high-efficiency cermet anode with a nano-sized
microstructure can also be obtained by sintering NiO-YSZ core-shell powders [18] or nano-sized composite powders [19-21].
In anode-supported SOFCs, a thick porous Ni-YSZ cermet is employed to provide the mechanical strength for the cell. Slow gas flow through thick Ni-YSZ may cause concentration polarization if the electrode comprises small grains and pores. Multi-layered Ni-YSZ anodes with gradients of composition and microstructure have been used in SOFCs to provide a supporting substrate layer with large grains and pores, and a functional layer with small grains and pores [22-25]. The thin anode functional layer (AFL) comes into contact with the electrolyte and provides abundant TPB. The thick anode substrate layer (ASL) provides high porosity for gas diffusion, thus reducing the concentration polarization. Meanwhile, the ASL contains many large Ni particles to ensure good electrical contact [24]. Anode-supported SOFCs use a thinner
electrolyte than electrolyte-supported SOFCs, which electrolyte has lower resistive loss. Basu et al. [23] studied anode-supported SOFCs with a thin Ni-YSZ AFL of about 5 μm thick and a thick ASL of about 1.5 mm thick. The SOFCs could be operated at an intermediate temperature of
electrolyte than electrolyte-supported SOFCs, which electrolyte has lower resistive loss. Basu et al. [23] studied anode-supported SOFCs with a thin Ni-YSZ AFL of about 5 μm thick and a thick ASL of about 1.5 mm thick. The SOFCs could be operated at an intermediate temperature of