超临界CO_2流体微细电铸扩散传质过程建模与数值分析

Diffusion Transport Modeling and Numerical Analysis of Micro-elecforming under Supercritical CO2 Fluid

以微结构特征为分析对象,建立金属镍离子和多物质离子扩散传质的数学模型,利用MAT-LAB软件对所建模型进行数值模拟,分析电流密度、深宽比对微结构内部物质离子浓度的影响,同时对超临界CO2流体金属镍铸层的表面形貌和显微硬度进行研究和探讨。结果表明:在一定的深宽比和电流密度条件下,随着时间的推移,镍离子扩散传质过程逐渐趋于稳态;微结构流体的特征是自上而下,氢氧根离子浓度和氢氧化镍离子浓度逐渐递增,而氢离子浓度持续降低,镍离子浓度和硫酸根离子浓度变化不明显;深宽比大的微结构应在小电流密度条件下进行电铸,温度为323K、压力为10MPa、电流密度为5A/dm2时,超临界CO2流体电铸方法制备的镍铸层晶粒细小、组织致密,铸层的显微硬度达到701.2HV,与传统电铸相比有大幅度提高。

Diffusion transport mathematics models of nickel ions and multi--species ions were established according to the micro--structure feature in supercritical CO2 fluid,which was simulated by MATLAB software. And the software was applied to analyse the effects of aspect ratio and current density on species ions concentration inside the micro--structure. The surface morphology and microhardness of nickel films were mainly discussed. The results indicate that the transport process of nickel ions approaches a steady state with the time increasing. From the top of micro--structure to the bottom ,hydroxyl ions and nickel hydroxide ions concentration are increasing, but hydrogen ions concentration decreases gradually, the variation of nickel ions and sulfuric acid root ions concentration are not obvious. Compared to the conventional electroforming method,a higher uniformity surface of the nickel film is obtained under supercritical CO2 fluid at 10MPa and 323K, the microhardness of nickel films are as 701.2HV with current density of 5A/dm2.