Surface pretreatment prior anodizing

The current transients observed upon immersion of n-type Si electrodes in HF of low concentration (2%) depend on the sample pretreatments. Immersion in 50% HF prior to anodization, for example, leads to current densities of up to 30 pA cm-2, which decreases within 1 s to the steady-state dark current value, producing a charge density of 24 pC cnrf 2. This effect has been ascribed to the density of Si-F bonds present on the electrode surface electrode prior to anodization [Be22],... 

Some rough surfaces resulting from pretreatment prior to adhesive bonding (a) porous anodic oxide on aluminum (schematic) (b) dendrites of zinc electrodeposited onto a zinc surface (c) black CuO layer produced on copper (d) PTFE irradiated by argon ions (After Koh et al. 1997) (e) adhesion of copper to silica using a mechanical key (van der Putten 1993) (i) TiW islands deposited (ii) Pd activator adsorbed and HF etching (iii) electroless Cu deposited (iv) Cu electrodeposited... 

Formation of the SEI layer plays an important role on the cycling stability of silicon-based anodes. Kulova and Skundin [109] reported a method used to preform the SEI layer on an electrode surface (prior to initial cathodic polarization) by direct contact of silicon and lithium metal in the electrolyte. The electrolyte was 1-M LiC104 in a mixture of propylene carbonate (PC) and dimethoxyethane. This method effectively reduced the irreversible capacity of the amorphous silicon electrode. Pretreatment of nanometer-sized silicon in ethanol also can form functionalized surfaces on the silicon particles that improve adhesion of silicon-based electrodes. A stable capacity of 2,500 mAh/g after 25 cycles has been reported for ethanol-treated silicon electrodes [110]. 

After pretreatment but prior to bonding, the adherend surfaces may undergo changes. The porous oxide produced on phosphoric acid anodization (PAA) of aluminum can be easily... 

Because the morphology of the outer surface of the CAA oxide is strongly dependent on the process steps used just prior to the CAA treatment, the type of pretreatment can be chosen to enhance the bonding. Samples that are FPL-etched and then anodized have a typical FPL shallow cell-and-whisker morphology. Surfaces that are PAA treated before the CAA anodization have a deeper cell structure, typical of PAA. Finally, surfaces that have a smooth tartaric acid-anodized (TAA) oxide before CAA treatment retain a smooth surface which is typical of the TAA treatment. 

---