Ivc 2013-1
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The document describes the development of a selective coating for parabolic trough solar collectors using DC reactive co-sputtering. The coating consists of a stack with layers optimized through simulations to have high solar absorptance and low thermal emittance. The layers include a SiO2 anti-reflection coating, molybdenum-doped SiO2 cermet absorbing layers of different metal volume fractions, and a silver back reflector. Voltage control was used during deposition to manage the hysteresis effect and achieve the desired stoichiometry and deposition rates of the individual layers. Characterization showed the coating achieved absorptance over 80% with emittance below 13% at operating temperatures.
![Optical characterization of the stack
Sample
Up-scaled
Temperature
λ2
∫λ
1
A(λ )
ε thn
0,804
0,047
0,804
0,076
0,804
0,111
650 °C
α sol
0,025
600 °C
∫
(θ , T ) = λ
0,804
500 °C
1
0,001
400 °C
∫λ [1 − R(λ ,θ )]A(λ )
=
0,804
300 °C
λ2
ε2
RT
λ2
α2
0,804
0,130
E (T , λ )[1 − RS (λ ,θ )]dλ
1
λ2
∫λ
1
E (T , λ )dλ](https://image.slidesharecdn.com/ivc-2013-1-131119053749-phpapp01/85/Ivc-2013-1-30-320.jpg)
Ivc 2013-1
- 1. Cermet coating deposition by DC reactive co-sputtering process controlled by voltage aintech@ain.es
- 2. Cermet coating deposition by DC reactive co-sputtering process controlled by voltage Beatriz Navarcorena, Julián Rodrigo, Gonzalo G. Fuentes, José A. García, Ramón Escobar, Carlos Prieto, José Angel Sánchez, Eva Céspedes, J. M. Albella IVC-19 2013 – September 9-13, Paris, FRANCE
- 3. Index 1 Objective 2 Introduction 3 Selective coating design 4 Deposition and characterization 5 Conclusions
- 4. Index 1 Objective 2 Introduction 3 Selective coating design 4 Deposition and characterization 5 Conclusions
- 5. Objective To develop coating a solar selective for the parabolic trough solar collectors that allows the operating temperature of the transfer fluid to reach 600ºC, and to develop an application method for them (PVD).
- 6. Index 1 Objective 2 Introduction 3 Selective coating design 4 Deposition and characterization 5 Conclusions
- 7. Introduction Parabolic trough solar collector Parabolic mirror Absorber tube
- 8. Introduction Key component: Absorber tube AR-coated glass tube (high solar transmittance) Glass-to-metal seal Selective absorber coating (high solar absorptance and low thermal emittance) Vacuum Insulation (minimized heat convection losses)
- 9. Introduction ↑ Solar absorptance 1,44 µm ↓ Thermal emissivity
- 10. Index 1 Objective 2 Introduction 3 Selective coating design 4 Deposition and characterization 5 Conclusions
- 11. Selective coating design Literature review Anti-reflection coating LMVF cermet absorbing layer HMVF cermet absorbing layer IR-reflective metal Substrate
- 12. Selective coating design Our stack SiO2 SiO2:Mo (LMVF) SiO2:Mo (HMVF) IR-reflective metal (Ag) Stainless steel
- 13. Selective coating design Software simulations To optimize the optical parameters Dependence with the metal volume fraction Dependence with the cermet thickness SiO2 64 nm LMVF-20% 70 nm HMVF-40% 113 nm Ag
- 14. Index 1 Objective 2 Introduction 3 Selective coating design 4 Deposition and characterization 5 Conclusions
- 15. Selective coating deposition DC-Reactive Magnetron Sputtering Elemental targets: Al, Ti, Si, etc. Reactive gases: O2, N2, etc. Inert gases: Ar, etc. SiO2, Al2O3, Si3N2… HYSTERESIS EFFECT
- 16. Selective coating deposition The hysteresis effect Constant power Metallic mode Voltage Reactive mode Reactive gas flow rate
- 17. Selective coating deposition The hysteresis effect Control Methods Increasing the pumping speed Increasing the target-to–substrate distance Obstructing reactive gas flow to the cathode Pulsed reactive gas flow Plasma emission monitoring Voltage control I.Safi “Recent aspects concerning DC reactive magnetron sputtering of thin films: a review” Surface and Coatings Technology 127 (2000) 203-219
- 18. Selective coating deposition The hysteresis effect Stoichiometry K.Koski et al. “Voltage controlled reactive sputerring process for aluminium oxide thin films” Thin Solid Films 326 (1998) 189-193
- 19. Selective coating deposition position The hysteresis effect Deposition rate K.Koski et al. “Voltage controlled reactive sputerring process for aluminium oxide thin films” Thin Solid Films 326 (1998) 189-193
- 20. Selective coating deposition The hysteresis effect Control method used speedflo™ Mini is a multichannel closed-loop control system for high speed adjustment of a reactive gas for magnetron sputter processes.
- 21. Selective coating deposition The hysteresis effect SiO2 Power Si constant = 2000 W loop point of maximal deposition rate
- 22. Selective coating deposition Characterization by FTIR: SiO2
- 23. Selective coating deposition The hysteresis effect SiO2:Mo In co-Sputtering, the hysteresis loop of Si target changes when the Mo target is on
- 24. Selective coating deposition Silicon power (W) 23 3000 60 4000 97 1000 2000 Deposition rate (nm/min) 1000 1000 Molybdenum power (W) 45 2000 62 3000 83 4000 111
- 25. Selective coating deposition Characterization by ellipsometry Si(1000W):Mo(4000W)
- 26. Selective coating deposition Optical simulations with real optical values
- 27. Selective coating deposition Silicon power (W) 23 3000 60 4000 97 HMVF 1000 2000 Deposition rate (nm/min) 1000 1000 Molybdenum power (W) 45 LMVF 2000 62 3000 83 4000 111
- 28. Selective coating deposition Layer Material MVF Thickness (nm) IR mirror Ag - 250 HMVF cermet Mo/ SiO2 0.28 100 LMVF cermet Mo/ SiO2 0.1 90 AR layer SiO2 - 50
- 29. Optical characterization of the stack FTIR dual MIR/NIR Spectrometer Rango: NIR: 11000-3000 cm-1 (0.9 - 3.3 µm) MIR: 4000-400 cm-1 (2.5 – 25 µm) UV-Vis-NIR Spectrophotometer Range: 200 nm – 3.3 mm
- 30. Optical characterization of the stack Sample Up-scaled Temperature λ2 ∫λ 1 A(λ ) ε thn 0,804 0,047 0,804 0,076 0,804 0,111 650 °C α sol 0,025 600 °C ∫ (θ , T ) = λ 0,804 500 °C 1 0,001 400 °C ∫λ [1 − R(λ ,θ )]A(λ ) = 0,804 300 °C λ2 ε2 RT λ2 α2 0,804 0,130 E (T , λ )[1 − RS (λ ,θ )]dλ 1 λ2 ∫λ 1 E (T , λ )dλ
- 31. Index 1 Objective 2 Introduction 3 Selective coating design 4 Deposition and characterization 5 Conclusions
- 32. Conclusions DC-reactive sputtering technique has important advantages for depositing multipurpose oxide films controlled by voltage. DC-reactive Magnetron process requires fast control methods in order to obtain high deposition rates with the desired stoichiometry, and with a low reactive gas flow rate. High value CSP technology stack architecture can be achieved by cosputtering with a previous optical simulation.
- 33. Acknowledgments The research leading to these results has received funding from the European Community's Seventh Framework Programme. Thanks for your attention!