Actualities and Problems of Surface Finishing for Aluminum. Present Status and Prospects on the Treatment of Hard Disks.

GDOES depth profiling analysis of amorphous Ni-P-plated aluminium hard disks

“…Mg alloy substrate at 363 K in a bath of 0.1 M dm 3 acetate and citric and lactic acids. 6,7 Furthermore, ammonia was used to adjust the plating bath pH to 4.5. The layers finally were polished mechanically with alumina to achieve a mirror finish with an average roughness of 5 nm.…”

“…The product performance of hard disks depends critically on thermal stability, flatness after mechanical polishing and the presence of micro-defects in the Ni-P layers, which in turn are related to the compositional uniformity through the film thickness and the presence of processrelated impurities at the Ni-P/aluminium interface. 6,7 Depth profiling analysis of Ni-P layers has not been reported previously because of the absence of techniques that allow rapid analysis of layers of ¾12 µm thick with the required sensitivity and depth resolution.…”

GDOES depth profiling analysis and cross-sectional transmission electron microscopy of a hard disk

“…The depth profiling analysis of the remaining regions, i.e. after 15 s, was carried out with a sampling time of 0.1 s. A high sputtering rate during GDOES depth profiling analysis is also evident; to penetrate through the 10 µm thick Ni-P layer required only 130 s, giving a sputtering rate of ¾4.6 µm min 1 . From the nickel, phosphorus, aluminium and magnesium profiles, it is shown clearly that the aluminium-magnesium alloy is covered with a thick Ni-P layer.…”

“…The aluminium-magnesium alloy, which was degreased and subsequently etched in an acid solution, is immersed in an alkaline zincate solution that usually contains small amounts of ferric chloride. 1,2 During immersion, a thin oxide layer covering the surface of aluminium-magnesium alloy dissolves and a zinc coating is then formed immediately through displacement, which later provides sites for Ni-P deposition. It is generally accepted that the role of Fe 3C ions in the zincate immersion bath is to reduce the dimensions of the zinc deposits by co-deposition of iron.…”

“…Currently, worldwide, around one billion hard disks are produced annually. 1,2 In their fabrication, aluminium disks are first treated with zincate and then amorphous Ni-P layers ¾12 µm thick are deposited electrolessly. The disks are then polished mechanically to an average roughness of ¾1 nm, leaving amorphous Ni-P layers ¾10 µm thick.…”