Highly Dense Mn-Co Spinel Coating for Protection of Metallic Interconnect of Solid Oxide Fuel Cells

Abstract

The major degradation issues of solid oxide fuel cells (SOFC) are associated with the oxide scale growth and Cr evaporation of the metallic interconnect. To address these challenges, a highly dense spinel oxide coating was fabricated on a ferritic stainless steel interconnect using a cost-competitive ceramic processing route. The nano-scale Mn 1.5 Co 1.5 O 4 spinel powder was synthesized using a glycine-nitrate method, and the particle agglomerates were effectively disintegrated by a high-energy attrition milling process. The spinel protective coating, which was applied by screen printing, was sintered to a nearly full density, without causing damage to the metallic substrate, by a high-temperature annealing process in a reducing environment, followed by re-oxidation at a moderate temperature. The dense spinel coating remarkably reduced the growth rate of chromia scale and restrained the evaporation of chromium species, as verified by area specific resistance (ASR) measurements and analysis on chromium distribution over the cross-section. Strong adhesion between the coating and substrate was confirmed after 500-hour operation. The sintering mechanism involved in reduction-oxidation heat-treatment was studied based on dilatometry measurements and microstructural features. The implication of the ASR change and the chromium migration for stability of practical SOFC stacks was discussed in detail.

CeO2-doped (Co,Mn)3O4 coatings for protecting solid oxide fuel cell interconnect alloys

“…According to these results, the CeO 2 -free (Co,Mn) 3 Depending on the type of substrate alloy, the treatment of substrate surface prior to coating, the coating process, the spinel stoichiometry, and the oxidation condition, an increase [12,27], decrease [3,4,12,[28][29][30], or no change [31] in the oxidation rate of the metallic interconnect has been reported with the spinel coating. With regard to the oxidation behavior of (Co,Mn) 3 O 4 -coated Crofer 22 APU, it is generally agreed that the coating reduces the oxidation rate of this alloy as the coating provides some barrier against the oxygen transport to the alloy surface, even though the degree of reduction is debatable.…”

“…Several techniques have been investigated for applying the (Co,Mn) 3 O 4 coating on the ferritic alloys, including: (1) screen printing of a spinel powder or an oxide powder mixture, followed by a treatment in a reducing environment and then a re-oxidization treatment [3,4]; (2) spray pyrolysis [5]; (3) thermal spray [6,7]; (4) physical vapor deposition (e.g. sputtering) [8]; (5) sequential electroplating of Co/Mn multilayers, electrodeposition of a Co-Mn alloy layer, or electrocodeposition of a Co-Mn 3 O 4 composite layer, followed by thermal conversion [9][10][11].…”

“…Furthermore, thermal conversion of the deposited layer to the spinel coating may also be accomplished in situ during the stack startup sintering step. Overall, this processing route offers a potentially low-cost approach for application of the (Co,Mn) 3 Even though the (Co,Mn) 3 O 4 coatings are capable of blocking Cr evaporation/migration from the ferritic interconnect alloy to the cathode, it still allows oxygen transport to the coating/alloy interface, which can cause continuous Cr 2 O 3 scale growth and subsequent electrical resistance increase during long-term thermal exposure of the interconnect [2][3][4]12,13]. Recently, it has been reported that CeO 2 , La 2 O 3 , or Y 2 O 3 doping in the spinel coating can reduce the oxide scale growth rate and improve the scale adhesion [14][15][16][17], via the so-called "reactive element effect" [18,19].…”

Oxidation and Electrical Behavior of Mn-Co-Coated Crofer 22 APU Steel Produced by a Pack Cementation Method for SOFC Interconnect Applications

“…Most recent research has focused on the application of protective and conductive spinel coatings, such as (Mn,Co) 3 O 4 [5,[12][13][14][15][16][17], (Cu,Mn) 3 O 4 [16,17], (Cr,Mn,Co) 3-O 4 [18] and Co 3 O 4 [19]. Cobalt and manganese spinel coatings are promising candidates for SOFC interconnect applications because of their high conductivity and oxidation resistance.…”

La–Mn–Cu–O protective coatings on 08Kh17T interconnector steel for solid oxide fuel cells obtained by electrochemical crystallization from non-aqueous electrolyte solutions

“…Покрытия наносят различными методами, такими как плазменное или термическое напыление, пакетная цементация, трафаретная печать, радиочастотное магнетронное распыление, гальваническое осаждение, химическое осаждение металлорганических соединений из газовой фазы [11][12][13][14][15][16][17][18][19][20]. В табл.…”