Cu-Mn尖晶石涂层的制备与高温性能的研究

发布时间：2018-07-25 08:18

【摘要】：随着中温SOFC技术的成熟应用,使得低价不锈钢铁素体作为连接体成为可能。但是,在SOFC的工作环境中,不锈钢铁素体表面会不断发生氧化,铁素体中会不断挥发出气态Cr,从而导致面比电阻增大与单电池的阴极毒化。在基体的表面增加一层抗高温氧化且导电的涂层是解决这些问题的一种有效办法。最近,一些尖晶石涂层,尤其是(Cu,Mn)_3O_4因其具有较高的电导率、与不锈钢铁素体匹配的热膨胀系数(TCE)以及良好的抑制Cr向外挥发的能力而受到了科学家们的重点关注。本文首先用电沉积的方法以氯酸盐体系、用EDTANa_2作为络合剂在430SS不锈钢铁素体表面制备了 Cu-Mn合金镀层,利用SEM及EDS研究镀层微观形貌及成分变化。研究了电流密度、pH值、沉积时间、电解液中n(Cu):n(Mn)的比等参数对合金镀层微观结构和成分的影响。然后,通过预氧化,即先后在750℃的氩气和800℃的空气中分别进行热处理2h,从而得到铜锰尖晶石涂层。最后,研究铜锰尖晶石涂层在SOFC阴极环境下800℃空气中和800℃空气+10%H_2O空气中的高温氧化行为,并用SEM、EDS和XRD分析等手段表征氧化膜的相结构、表面和截面微观形貌及元素分布,研究了不锈钢铁素体表面沉积铜锰尖晶石涂层的氧化机制。此外,利用四点法测试铜锰尖晶石涂层高温氧化后的面比电阻(ASR)。得出的主要结论如下:通过电沉积的方法成功的在430SS表面得到了 Cu-Mn合金镀层,电流密度为200～700mA/cm~2、pH 值为 3～7、时间为 10～30min 和 n(Cu):n(Mn)的比为 1:20～1:10 时,镀层中的Mn含量随着电流密度、pH值、时间的增大而增大,随着n(Cu):n(Mn)的比值增大而减小。当 pH=5,时间 t=20min,n(Cu):n(Mn)=1:10,电流密度 i=450、500、550mA/cm~2时,可以得到均匀、致密、无边缘效应、与基体结合良好、Mn含量较高且铜锰比分别为1:2、1:1、2:1的铜锰合金镀层。预氧化处理可以使得铜锰合金完全转变为铜锰尖晶石涂层。氧化涂层分为两层结构,外层为(Cu,Mn)_3O_4和内层的富Cr氧化层组成。涂层和基体在800℃空气中氧化300h后都具有较低的氧化速率。涂层与基体结合良好,可以降低基体在800℃的氧化速率。在含10%H_2O的空气氧化过程中,430SS在一段时间的孕育期后发生失稳氧化,然而(Cu,Mn)304能很好的阻止失稳氧化的发生。在空气和潮湿的空气中氧化后涂层依然保持双层结构。(Cu,Mn)_3O_4涂层和430SS在800℃的空气氧化300h和在800℃的潮湿空气氧化100h的接触电阻都随测试温度的升高而降低。铜锰尖晶石涂层中铜锰原子比为1:1、1:2、2:1三种尖晶石涂层在800℃空气中氧化300h后的ASR分别为23.2mQ.cm~2、15.3mΩ·cm~2、35.3mΩ·cm~2,低于同样条件下的基体的ASR值41mΩ·cm~2。铜锰尖晶石涂层中铜锰比为1:1、1:2、2:1三种尖晶石涂层在在800℃潮湿空气中氧化100h后的ASR分别为33.2mQ.cm~2、25.6mQ.cm~2、69.3mQ.cm~2,也同样低于相同条件下的基体的ASR值83mQ.cm~2。
[Abstract]:With the mature application of medium temperature SOFC technology, it is possible to use low-price stainless steel ferrite as connectors. However, in the working environment of SOFC, the surface of the stainless steel ferrite will be oxidized continuously, and the gaseous Cr will be volatilized in the ferrite, which will lead to the increase of the surface specific resistance and the cathodic toxicity of the single cell. It is an effective way to solve these problems by adding a layer of high temperature oxidation resistant and conductive coating on the surface of the substrate. Recently, some spinel coatings, especially (Cu-Mn) _ 3O _ S _ 4, have attracted great attention due to their high conductivity, thermal expansion coefficient (TCE) matching with stainless steel ferrite, and good ability to inhibit Cr outward volatilization. In this paper, Cu-Mn alloy coatings were prepared on the ferrite surface of 430SS stainless steel by electrodeposition with chlorate system and EDTANa_2 as complexing agent. The microstructure and composition of the coating were studied by SEM and EDS. The effects of current density pH value, deposition time and the ratio of n (Cu) to n (Mn) in electrolyte on the microstructure and composition of alloy coating were studied. Then, the copper manganese spinel coating was obtained by preoxidation, which was heat treated in argon at 750 鈩，

本文编号：2143198