| 摘要 |
<p>An Al substrate is provided with a dark surface having a high absorption/omission ratio for luminous energy by (a) immersing in an oxidising bath to form a is not >2.5 mu thick oxide coating, (b) rinsing and (c) immersing in a aq. acidic soln. of 1-200 g/l potassium permanganate and 1-100 g/l nitrate of co or Cu at pH 0.5-5 and 90-100 degrees C. The process is used esp. to produce light-absorbing surfaces for solar energy collectors. Absorption coeffts. of >=0.8 and absorption/emission ratios of >3 are obtd.</p> |
