Preparation Cr₂O₃ and CrN diffusion barriers for stainless steel supported palladium membrane

In this research, chromium oxide (Cr₂O₃ ) and chromium nitride (CrN) thin films were fabricated as the intermetallic diffusion barriers between the palladium (Pd) membrane and stainless steel (SS) support. Three different methods for preparation of Cr₂O₃ were investigated, i.e., thermal oxidation, oxidized Cr-electroplating, and oxidized Cr-sputtering. The thickness of chromium thin films was controlled by chromium deposition time and measured by gravimetric method and SEM. They were found to be 2 to 6 µm as determined by SEM. The optimum condition for the oxidation of chromium to Cr₂O₃ was at 600°C for 6 hours. The CrN thin film was formed by Cr-sputtering in nitrogen atmosphere. The composition and phase structures of Cr-based thin films were studied by EDS and XRD. The Pd membranes were then developed on top of Cr-based thin films by electroless plating. The efficacies in preventing intermetallic diffusion were assessed employing SEM-EDS to analyze the elemental content of the palladium layer after hydrogen exposure for 24 hours at 400, 500 or 600°C. After the hydrogen exposure, all Cr-based thin films acted as the good intermetallic diffusion barriers, with no detectable presence of elementals from the SS disk on Pd layer. Among the four types of thin films, Cr₂O₃ created by sputtering and oxidation showed the highest permeation flux which was measured at 350-500°C in pressure differences of 1-3 atm.

本研究制备了氧化铬（Cr₂O₃）与氮化铬（CrN）薄膜，将其用作钯（Pd）膜与不锈钢（SS）载体之间的金属间扩散阻挡层。针对Cr₂O₃的制备，本研究探究了三种不同工艺：热氧化法、氧化铬电镀法以及溅射铬氧化法。通过调控铬沉积时长控制铬薄膜的厚度，并采用重量法与扫描电子显微镜（SEM）进行厚度表征，经SEM测得薄膜厚度为2~6 μm。铬氧化生成Cr₂O₃的最优工艺条件为600℃下保温6小时。CrN薄膜则通过在氮气气氛下溅射铬制得。采用能量色散X射线光谱（EDS）与X射线衍射（XRD）对铬基薄膜的组分与物相结构进行了表征。随后通过化学镀法在铬基薄膜表面制备钯膜。在400、500或600℃下经24小时氢气暴露后，采用SEM-EDS分析钯层的元素组成，以此评估各薄膜的金属间扩散阻挡效能。结果显示，所有铬基薄膜均表现出优异的金属间扩散阻挡性能，钯层中未检测到来自不锈钢圆盘的元素。在四种薄膜体系中，经溅射与氧化制备的Cr₂O₃薄膜展现出最高的渗透通量，该性能在350~500℃、压差1~3 atm的条件下测得。