Base material for a fuel cell

Abstract: A material for a base tube of a fuel battery, comprising a mixture of at least two components selected from the group consisting CaO , ZrO 2 ,NiO, MgO, SrO, Al2O3, TiO2, and BaO. Such material suppresses cracks of an electrolyte and also suppress leakage after rapid temperature increase and decrease, thus providing a reliable fuel battery.

Description: Field of the Invention This invention relates to a base material for a fuel battery. Background of the Invention An example of a conventionally used technique is shown in Fig. 1. A base tube (base material portion) 1 according to prior art comprises a porous tube composed of 30.0 wt.% of CaO and 70.0 wt.% of ZrO 2 . On the surface of the base tube (base material portion) 1, there are laminated a 100 µm thick fuel electrode-side electrode 2 comprising Ni-zirconia thermit, a 100 µm thick electrolyte 3 comprising yttrium-stabilized zirconia ("YSZ"), and a 100 µm thick air-side electrode 4 comprising LaMnO 3 doped with Sr in a proportion of 0.1. Further, a conductive connecting material 5 comprising LaCrO 3 is laminated for connecting the fuel electrode-side electrode 2 with the air-side electrode 4 to form a solid oxide fuel cell ("SOFC"); hereinafter referred to as "a fuel cell"; multiple fuel cells are connected to form a device hereinafter referred to as a "fuel battery". However, the base tube according to the earlier technology poses the problem of degrading markedly at a fast temperature raising and lowering rates during a heat cycle. In detail, with a temperature raising and lowering rate of not higher than 50°C/hour, the performance of the cell after the heat cycle does not differ from its performance before the heat cycle. At a temperature raising and lowering rate in excess of 50° C/hour, on the other hand, an output drop of about 10% may occur per each heat cycle. When fuel cells are used as a gathering, a temperature raising and lowering rate, if not made very slow, exceeds 50°C/hour in a part of the fuel cell gathering, thereby damaging the cell. Thus, there is a demand for a cell which is not damaged even at a high temperature raising and lowering rate of about 200°C/hour. Brief Description of the Drawing Fig. 1 is a sectional view of a base tube of a solid electrolyte fuel battery. Summary of the Invention In order to meet such demand for a fuel cell, the material for constructing the porous base tube of the fuel cell has been changed from the prior art material comprising 30.0 wt.% CaO and 70. wt.% ZrO 2 . It has been found that porous base tubes comprised of the materials described below will permit the fuel cell to operate at heat cycles entailing rapid rates of temperature increase and decrease without any significant reduction in output. Details of the Invention According to the invention the material employed for the porous base tube of a fuel battery comprises a three-component mixture of CaO, ZrO 2 and NiO. Especially it consists of 9.1 wt.% ≤ CaO ≤ 26.1 wt.%, 20.0 wt.% ≤ ZrO2 ≤ 60.9 wt.%, and 13.0 wt. % ≤ NiO ≤ 70.0 wt.%, wherein NiO particles of 5 µm or less are used. <Example> Base tube Leak after 1 cycle of rapid temperature raising and lowering Leak after 15 cycles of rapid temperature raising and lowering Fuel composition capable of power generation Composition (4) CaO: 26.1 wt.% ZrO 2 : 60.9 wt. % NiO particle size: 5 µm 3% 3% S/C = 1.5 Composition (1) CaO: 26.1 wt.% ZrO 2 : 60.9 wt.% NiO: 13.0 wt.% 3% 3% S/C=2.0 Prior Art CaO: 30.0 wt.% ZRO 2 ; 70.0 wt.% 3% 28% S/C = 2.0 Actions and effects of Example: A base tube comprising a composite material having a CaO-ZrO 2 -MgO three-component mixture (particle size of NiO: 5 µm or less). Fig. 1 shows an example in which a base tube (base material portion) 1 was formed from a porous tube comprising a composite material having a composition (4) indicated in Table 4. Composition (4) was similar to composition (1) in its content, except that the NiO employed in composition (4) consisted of particles having a maximum particle size of 5 µm. On the surface of the base tube 1, a fuel electrode-side electrode 2, an electrolyte 3, and an air-side electrode 4 where laminated, and a conductive connecting material 5 was further laminated. The compositions of these materials and the procedure used were the same as in the prior art. In this manner, a fuel battery was produced. The rapid temperature raising and lowering of the fuel battery was repeated, and then it leaks before and after this tests were compared. Fuel composition capital of power generation using natural gas as a fuel were also compared. The results are shown in the Table. A fuel battery having the aforementioned based tube composition (1) (particle size:10 um), and the fuel battery having the base tube composition CaO: 30.0 wt.%/ZrO 2 : 70.0 wt.% according to the earlier technology were used as controls. The results given in Table 4 show that the composition (4) causes no changes in the leak after rapid temperature raising and lowering and can reduce the amount of steam added (S/C = Steam/carbon) during use of natural gas. Actions and effects of Example. The composition of the invention can suppress cracks of an electrolyte during rapid raising and lowering of the temperature of a fuel battery, reduce the leak after temperature raising and lowering, and thus provide a reliable fuel battery. It can also decrease the amount of steam added when natural gas is used as a fuel. As noted above, the composition (4) can suppress the increase of the leak after rapid temperature raising and lowering. It can also decrease the amount of steam added when natural gas is used as a fuel.

Claims: A material for a porous base tube of a fuel battery, comprising a three-component mixture consisting of CaO, ZrO2 and NiO, wherein 9,1wt.% ≤ CaO ≤ 26,1 wt.%, 20.9 wt.% ≤ ZrO2 ≤ 60.9 wt.%, and 13.0 wt.%≤ NiO ≤ 70.0 wt.%, the NiO being present in the form of particles having a particle size of 5 µm or less.

Inventors: HISATOME NAGAO, HOUJYOU TORU, NISHI TOSHIRO, TSUKUDA HIROSHI, HISATOME, NAGAO, HOUJYOU, TORU, NISHI, TOSHIRO, TSUKUDA, HIROSHI, Hisatome, Nagao c/o Mitsubishi Heavy Ind., Ltd., Houjyou, Toru c/o Choryo Engineering Co., Ltd., Nishi, Toshiro c/o Mitsubishi Heavy Ind., Ltd., Tsukuda, Hiroshi c/o Mitsubishi Heavy Ind., Ltd.
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI HEAVY INDUSTRIES, LTD.
Application year: 1998
Main classification: H01M8
IPC codes: C04B35, H01M8