Fig. 1

Scanning electron microscopy and laser interferometry. a, d Machined surface. b, e 20-min acid treatment. c, f 60-min acid treatment. Original magnification, × 15,000
Scanning electron microscopy and laser interferometry. a, d Machined surface. b, e 20-min acid treatment. c, f 60-min acid treatment. Original magnification, × 15,000