The main requirement addressed to mSOFC and SOFC systems is related to the reduction of their fabrication and operation cost。 The metal supported SOFC is one of possible solutions due to substitution of ceramic SOFC elements by cost effective metallic。 This idea is very engaging and lately a few research groups are working on such system, e。g。 (Carter et al。, 2003, 2006; Tucker et al。, 2008; Hui et al。, 2007)。 The metallic elements are also advantageous because of high- temperature conductivity of metals allowing faster startup of the SOFC and have higher durability to temperature cycling。 Moreover, due to its high-electronic conductivity, they function perfectly as current collectors and interconnectors。 An example of the stainless steel supported SOFC system called Tuffcell is shown in Figure 5。 The elements of the cell are prepared using typical ceramic technologies。 The metal support (434 stainless steel, 2 mm thick), anode (0。2 mm thick) and electrolyte (15 mm thick) are tape casted, laminated together and sintered in a single high-temperature process。 Only the cathode is casted separately and sintered in situ
during fuel cell operation。 The Tuffcell provides 350 mW/cm2
at 8008C。 Also the results obtained by the other research
Figure 4 The procedure of assembling cube shaped micro tubular SOFC bundles
Anode Tubes and ElectrolyteExtrusion of anode,Dip-coating Electrolyte, and Co-firing
Extrusion of Cathode and Sintering
Coating Paste of Cathode Materials
Bonding of Parts, and Sintering
Source: Funahashi et al。 (2007) reproduced with permission of Elsevier
Figure 5 Tuffcell – metallic supported SOFC: (a) schematic diagram; (b) picture of three cell stack
Source: Courtesy of Argonne National Laboratory
groups are very perspective。 However, the metallic supported SOFCs are facing problems related to corrosion of stainless steel and temperature expansion coefficient mismatch between ceramic layers and stainless steels。 In the interface between steel and ceramic the oxide scale can be formed, which can exhibit high resistance。 An example is shown in Figure 6, where in the interface of YSZ and 316L the about 2 mm thick iron oxide scale is formed at as low as 4008C。 In this case the YSZ was deposited on 316L using combination of colloidal suspension and polymer precursor methods。 From the point of view of electrical conductivity it is advantageous when the oxide scale is in a form of chromium oxide。 Therefore, the chromium steels are often used for SOFC applications。 Unfortunately, during fuel cell operation chromium vapors might poison the cathode what results in the decrease of fuel cell performance。
Recently, a lot of attention has brought fabrication of fuel cell using MEMS technology。 It is much easier to use MEMS technologies to prepare low-temperature polymer electrolyte membrane fuel cells and some examples of such devices can be found in literature (Yamazaki, 2004; Erdler et al。, 2006)。 The fabrication of SOFC using MEMS technology is much tougher, even though schematic view of expected structure seems to be simple (Figure 7)。
The procedure of mSOFC preparation using MEMS technology may consist of the following steps (Jankowski and Morse, 1998; Morse and Jankowski, 1999):
1formation of silicon nitrate thin layer on silicon wafer by chemical vapor deposition formation at high temperature in dichlorosilane and NH4;
Figure 6 YSZ on 316L stainless steel prepared by net shape technology
2
patterning of silicon wafer backside using typical photolithographic techniques;
3etch of silicon in KOH up to silicone nitrate;
4deposition of Ni on the top of wafer by dc sputtering technique;论文网
5deposition of Ni and YSZ on Ni film by dc and rf sputtering technique, respectively; 微型固体氧化物燃料电池英文文献和中文翻译(3):http://www.youerw.com/fanyi/lunwen_101140.html