Gas and surface applications of atmospheric pressure plasmas

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1 Gas and surface applications of atmospheric pressure plasmas Eugen Stamate Technical University of Denmark Roskilde 4000, Denmark

2 OUTLINE Introduction of DTU Energy Conversion and Storage Activities in Reactive Plasma Processing laboratory - Thin film batteries - NOx reduction - Bacterial inactivation

3 Technical University of Denmark DTU Excellence since 1829 MISSION Create value for society using the natural and technical sciences Leiden Crown Indicator 2010: no. 1 in Scandinavia no. 7 in Europe Total students ~8.500 including Ph.D and Int. M.Sc. 650 Research publications 3.600

4 DTU organization

5 Department of Energy Conversion and Storage Sustainable technologies for energy conversion and storage 250 people (70 scientific staff) Research span from fundamental investigations to component manufacture Focus on industrial collaboration and industrially relevant processes Created 2012, bringing together outstanding research groups from Risø DTU National Laboratory for Sustainable Energy DTU Chemistry Located on two campuses: Risø and Lyngby

6 Research activities in the Department of Energy Conversion and Storage Solid oxide fuel cells High-temperature polymer electrolyte fuel cells Electrolysis Polymer solar cells Batteries Synthetic fuels Membranes for oxygen or hydrogen separation Magnetic refrigeration Thermoelectric components Flue gas purification using electrochemical cells Superconducting components FCH Test Center for fuel cell and hydrogen technologies

7 Case study: Solid Oxide Fuel Cells Research Better materials New cell designs Improved manufacturing processes Improved durability Long term tests

8 Polymer solar cells Promising alternative to traditional Si-based photovoltaics Organic photovoltaics printed on flexible plastic substrates High-speed roll-to-roll processing very low production costs low capital investment high throughput Research focus on increased efficiency and lifetime

9 Magnetic refrigeration Uses the magnetocaloric effect N S Ceramic materials with tunable transition temperature Advantages high efficiency low-noise operation environmentally friendly (no volatile gases) Both for refrigeration and heat pumps N S Prototype designed and constructed at DTU 200 W cooling 18 C span further optimization under way

10 Thermoelectrics Use of the Seebeck effect to generate electricity Conversion of waste heat from, e.g., solid oxide fuel cells Oxide materials for operation at C Aim is to demonstrate a device with a conversion efficiency approaching 15-20%

11 Reactive plasma processing Part of ElectroFunctional Materials (EFM) section Established in September 2006 Main activities - Thin films for electrochemical cells (SOFC, batteries, catalytic materials) - Plasma technologies for environment (NOx/SOx reduction) - Etching - Plasma immersion ion implantation - Plasma sources (ECR, ICP, Sputtering, DBD) and diagnostics (probes, mass spectrometry, optical emission spectroscopy, absorption spectroscopy)

12 Surface functionalization and thin films -insulating materials (charging effects) - temperature sensitive materials (polymers, plastics, bio-samples) - controllability of incident angle (process tuning) - large surface (high throughput) Extraction of a focused ion beam using slit. [E. Stamate, US patent (2011)] Matrix-ECR plasma source in RPP at DTU

13 Li thin film batteries Energy storage essential for an information based society Small volume and high power density Targeted applications: - MEMS - Smart cards - Micro-cameras - Microelectronics Thin-film battery Koo et al., Nanoletters (2012)

14 Lithium Ion Batteries Conventional Lithium ion battery All-solid thin film Lithium ion battery Less compatible with micro and nanoelectronic devices, safety issues Requirements: - High ionic conductivity - Stability with anode and cathode - Large potential window Both electrodes are capable of reverse lithium insertion. Because of difference in chemical potential the transport delivers (discharge) or consumes (charge) energy. Needs to be compatible with soldering stand more than 220 C

15 Introduction - Lipon Material: Li 3 PO 4 (Developed in 90s at Oak Ridge laboratories by Bates and coworkers) Deposited film: Lithium phosporus oxinitride (LiPON): Li 3.3 PO 3.9 N 0.17 (glassy) Moderate conductivity, compensated with a film thickness of about 1 µm Deposition methods in N 2 -atmosphere Main: RF magnetron sputtering (2-4 nm/min sintered, 30 nm/min powder) Alternative: Ion beam assisted deposition, Pulsed laser deposition, E-beam evaporation, Plasma assisted direct vapor deposition, Plasma enhanced metalorganic CVD Challenges Moderate Li + ion conductivity Reacts with air How to increase the conductivity?

16 RF & ECR setups for diagnostics 3x4 matrix of ECR distributed plasma cells Boreal Plasma

17 FIB-SEM 5 mtorr, 100 W, 7 h 1.43 µm 20 mtorr, 100 W, 7 h 0.97 µm 50 mtorr, 100 W, 7 h 0.59 µm Ag, Au 300 nm Lipon 1 µm Au 100 nm Si wafer Pressure (mtorr) Conductivity (µs/cm) a

18 Mass appearance spectrometry Nitrogen dissociation is significantly higher at low pressure Lithium availability is high at low pressure

19 NOx reduction Ozone O 3 NOx N 2 O 5 NO+O 3 NO 2 +O 2 2NO 2 +O 3 N 2 O 5 +O 2 N 2 O 5 +H 2 O 2HNO 3 NOx HNO 3 (aid rain) High temperature burner Power plants, gas turbines incinerators, boilers, diesel, etc. Strong negative effects on the quality of air, soil and human health Use the same principle to reduce the NOx under controllable conditions

20 Typical NOx reduction setup 1. Flue gas flow 2. NOx concentration 3. Inlet flue gas temperature 4. Electric power to ozone generator 5. Oxygen production 6. Oxygen consumption 7. Ozone production 8. Reactor temperature 9. ph in scrubber media 10. Temperature of scrubber media 11. Ozone concentration after scrubber 12. Temperature after scrubber 13. NOx after scrubber flue gas blower catalyst stack water 1-3 O 2 /O 3 flow REACTOR 6-7 Power ozone O 2 flow 4 generator 5 scrubber neutralizer 9 10 drain

21 NO X /SO x PlasTEP reactor built at DTU 6 m long reactor up to 250 SLM flue gas up to 100 g/h O 3 (air, O 2 ) NO, NO 2, O 3 sensors 7 sampling ports Controlled gas flows Gas and reactor heating Wet scrubber O 3 destroyer NOx up to ppm PC control

22 NOx/SOx PlasTEP reactor built at DTU

23 NOx/SOx PlasTEP reactor at DTU

24 NOx/SOx PlasTEP reactor built at DTU

25 Mixing schemes NO 2 and O 3 R as a function of O 3 IN at P 1 for all four mixing schemes for an air flow of 40 slm, ozonized air of 10 slm, slm of NO and initial values of NO=316 ppm and NO 2 =104 ppm (O 3 IN =0 ppm).

26 Time dependence Constant O 3 IN, on-off NO, NO x at P 1 and P 5 for 50 slm dry air, 0,21 slm NO, NO x _on= 411 ppm, NO_on= 304 ppm. O 3 IN =1900 ppm, Power ozone generator = 256 W.

27 Bacterial Inactivation using DBD plasma Time Temperature - What is the life time of a food product? - Can we extend it? Time - Initial bacterial concentration - Growth rates in specific packages

28 Effect of MAP with CO 2 on seafood products TMA at sensory Drip loss at Shelf-life Modified atmosphere packaging (MAP) Packaging rejection sensory (days at 0 C) with CO (mg-n/100g) 2 is successfully used for fresh rejection (%) and slightly coked see food products Vacuum ~30 for more 4.7 than 15 years 30% CO ~ % CO ~30 7.9

29 Experimental setup HV electrode Water cooled electrodes Gap spacer (3-10 mm) Electrodes surface: 50x50 mm 2 Total surface of the package: 80x80 mm 2 Maximum thickness: 10 mm. Copper thin film deposed on dielectric substrates (avoid heating of dielectrics by parasite discharge)

30 Details - closed container Quartz window

31 Plasma effect on sensory properties of salmon Sensory properties: color, texture Samples: sliced cold-smoked salmon packed in plastic bags Treatment variables: applied voltage (V pp ), frequency, gas gap, treatment time. Applied voltage (kv) Frequency (khz) Gas gap (mm) Treatment time (min.) Sensory properties (appearance, texture ) Acceptable Acceptable Acceptable Acceptable Acceptable Acceptable NOT acceptable NOT acceptable NOT acceptable Acceptable Acceptable

32 Preliminary tests on ceramic plates for atmospheric discharges

33 Preliminary tests