铝阳极氧化残存水合氧化膜热稳定性研究

Study on thermostability of the residual hydroxide films on aluminum foils

采用水煮和直流阳极氧化法在铝箔表面获得残存的水合膜,研究热处理对水合膜结构和性能的影响。热重-差示扫描量热仪(TG-DSC)和傅里叶变换红外光谱分析(FTIR)测试表明,铝箔存在两个质量损失过程,200℃以下为铝箔表面吸附游离水的蒸发,200℃以上为水合膜中结构水的分解。X射线衍射(XRD)和扫描电子显微镜(SEM)测试结果表明:氧化膜分为内层的结晶Al2O3和外层的羽毛状Al2O3·xH2O两层,经过不同温度热处理后,水合膜的厚度和形貌无明显变化。电化学性能测试表明,热处理后样品的耐压值略有增大,比容值减小,主要是由于少量水合膜脱水转化为结晶Al2O3所致。

The aluminum specimens covered with hydroxide films were prepared using direct-current anodization method after boiled in ultrapure water. The effect of heat-treatment on the structure and the properties of hydroxide films were investigated. Thermogravimetry-differential scanning calorimetry （TG-DSC） and Fourier transform infrared spectroscopy （FTIR） analysis confirm that there are two steps during the heat-treatment process. The first step under 200 ℃correspond to evaporation of free water absorbed on aluminum foils. Crystal water in hydroxide film is lost in second step above 200 ℃. X-ray diffraction （XRD） and scanning electron microscope （SEM） reveal the film formed on aluminum consists of a crystal inner layer and a feather-like outer layer. After heat-treatment, the crystallinity of inner layer is improved, however the thickness and morphology of both layers change little. Electrochemical performance show the withstanding voltage of the anodized aluminum specimens increases a slight and the specific capacitance decrease a little. This can be explained by dehydration of hydroxide film converted into crystal alumina.