Fig. 1. Schematic of nanosecond laser ablation system

Fig. 2. Water contact angle of copper foam surface. (a) Water contact angle of pristine copper foam surface; (b)‒(c) water contact angle of superhydrophobic surface; (d) oil contact angle of pristine copper foam surface; (e) oil contact angle of superhydrophobic surface

Fig. 3. Water contact angle under different scanning parameters. (a) Relationships between water contact angle with laser power P or scanning speed v; (b) relationship between water contact angle and scanning spacing d

Fig. 4. Surface images of copper foam. (a) Surface image obtained under different ablation parameters; (b) SEM morphology of pristine copper foam surface

Fig. 5. SEM images of copper foam surface obtained under different laser power values. (a) 8 W; (b) 10 W; (c) 14 W; (d) 18 W

Fig. 6. SEM images of copper foam surface obtained under different scanning spacing values. (a) 100 μm; (b) 50 μm; (c) 10 μm

Fig. 7. SEM images of copper foam surface obtained under different scanning speeds. (a) 1.6 m/s; (b) 0.8 mm/s; (c) 0.4 mm/s; (d) 0.2 mm/s

Fig. 8. EDX analysis of surfaces. (a) Pristine copper foam; (b) superhydrophobic copper foam

Fig. 9. Oil recycle. (a) Oil recycle device; (b) formed oil layer in recoverer; (c) recycle finish

Fig. 10. Schematic of oil recycle