1. THERMOCHROMIC NANO-COATINGS FOR SOLAR RADIATIONS HEAT REGULATION IN SMALL SATELITTES Energy Postgraduate Conference 2013 L. MATHEVULA iThemba LABS Langu@tlabs.ac.za Supervisor: Prof M. MAAZA (iThemba LABS) C0-Supervisor: Prof V.V SRINIVASU (UNISA)

2. Outline Aims and Objectives Heat Management for Small Satellite Smart IR Coating:VO2 Experiments & Results Conclusion

3. Aims & Objectives ● TUNABLE LARGE IR OPTICAL TRANSMISSION, ● TEMPERATURE PHOTO-INDUCED IR MODULATION, ● FREE ENERGY-INPUT FOR ITS OPERATION, ● LARGE DURABILITY TO DEEP SPACE RADIATIONS: ENERGETIC H+. DEVELOP & ENGINEER A SMART COATING FOR SOLAR HEAT MANAGEMENT IN SMALL SATELITTES WITH THE FOLLOWING CHARACTERISTICS:

4. IMAGES FROM THE WEB Heat management for Small Satellite ● Thermal shielding in satellites and spacecrafts “NASA, JAXA, ESA, …..” -Critical in small satellites: Sumbandilla: ≈ 81 kg, ZACUBE 1: ≈ 1.175 kg Input energy = 0 mJ

5. SMART IR COATING: VO2 SCIENTIFIC REPORTS | 3 : 1370 >68 o C <68 o C High Temperature phase Tetragonal Low Temperature phase Monoclinic

6. EXPERIMENTS-RESULTS ● PULSED LASER DEPOSITION “SUN-iThemba joint unit” ● Nd:YAG ● Repetition rate: 10 MHz, ● wavelength: 355 nm, ● Energy: 180 mJ, ● Target: Vanadium, ● substrate temperature: 500 O C ● Substrate: Mica

7. XPS V2p shows a two-peak structure (V2p 1/2 and V2p 3/2 ) due to the spin- orbit splitting V2p 3/2 peak is more sensitive to phase change, hence the peak is used to identify the phase change of vanadium oxide

8. Electrical properties T SMT = (T H + T C )/2, T H =63 o C and T C = 70 o C and hence T SMT = 66.5 o C and

9. Proton Irradiation ● Beam: H+ ● Beam Energy: 2Mev ● Beam spot: 2mm ● Current ≈ 50nA.

10. Proton Irradiation ≈ 400 nm VO 2 / MICA substrate -2 MeV H + -Doses: 36 x 10 15 72 x 10 15 110 x 10 15 140 x 10 15 Ions/cm 2 ● Low/Mid dose: Coarsening & VO 2 crystallites’ growth ● High dose: Possibly crystallites melting

11. Conclusion ● A smart coating for solar heat management (VO 2 ) successfully synthesized by PLD on Mica substrate ● Irradiation of VO 2 shows change in morphology ● further irradiation characterization to be done