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Novel Wide Area Hydrogen Sensing Technology

Novel Wide Area Hydrogen Sensing Technology. W. Hoagland D. K. Benson R. D. Smith. Outline. New developmental hydrogen gas indicators Technologies Response kinetics Possible applications. What are Chemochromic H2 Detectors?.

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Novel Wide Area Hydrogen Sensing Technology

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  1. Novel Wide Area Hydrogen Sensing Technology W. Hoagland D. K. Benson R. D. Smith

  2. Outline • New developmental hydrogen gas indicators • Technologies • Response kinetics • Possible applications

  3. What are Chemochromic H2 Detectors? • Chemochromic hydrogen detectors change color when exposed to gaseous hydrogen. This color change is caused by a chemical reaction between hydrogen and the active material. It may be reversible or non-reversible.

  4. Coloration 1. H2 + 2(Pd) 2(Pd.H) 2. 2(Pd.H) + 2(WO3) 2(W+5O2.OH) + 2(Pd) Bleaching 3. 2(W+5O2.OH) + 1/2O2 2WO3 + H2O Reversible partial reductionof tungsten trioxide

  5. ChemochromicChemical ReactionsOptical absorption by electrons localized at oxide vacancies • Electrons are localized in the vicinity of W5+ ions as small polarons hv + W5+(A) + W6+(B) W6+(A) + W5+(B)

  6. Technology addresses a recognized need “Although safety-by-design and passive mitigation systems are preferred, it will still be necessary to develop technologies to detect hydrogen releases or other system failures. For example,coatings that change color upon exposure to hydrogen can provide immediate visual evidence of a leak.” U.S. DOE Multi-year Plan 2003-2010

  7. Critical Research Topic “The overall goal is to develop low-cost sensor technologies that are not based on conventional practices, that can be directly integrated with hydrogen systems, and that are resistant to contamination.” …Goal #3: Develop a sensing technology for a wide-area determination of hydrogen presence prior to any combustion or local temperature rise.” U.S. DOE - February 2004

  8. Advantages of Chemochromic Hydrogen Indicators • Reversible color change • Inherently safe – no ignition source • Convenient indication from a distance • No instrumentation needed • Applicable in various forms • Paints, inks, coatings • Tape/Stretch Films • Conformable Wrap • Decals • Very low cost

  9. Typical structures of chemochromic indicator material Vacuum deposited multi-layer thin film PTFE 100 nm Palladium 3 nm Tungstenoxide 500 nm Substrate polymer sheet Chemically synthesized nano-particles Nano-powder Tungsten oxide (~50 nm) Platinized Chemically (~5%)

  10. Thin film indicator responds quickly and reversibly

  11. Thin Film Indicator Could be used for lettering on safety decals No hydrogen present Hydrogen present

  12. Flexible Plastic Indicating Tape Could be used to wrap around pipe fittings

  13. Shrink wrap indicator appliedto a low pressure cylinder with an intentional 50 micron hole

  14. Nano-particles could be used in “smart paints” or printing inks Paint formulations shown to work include: • Epoxy (100% solids) • Polyurethane • Acrylic (Solvent based) • Acrylic (Water Based)

  15. Indicators turn dark blue when exposed to hydrogen

  16. Response of Chemochromicindicator is exponential – thin film Switchto air H2

  17. Response mechanism • Double exponential decay in transmittance is characteristic of two parallel first-order chemical reactions. • Speculation: The reactions occur at different kinds of catalytic sites - • At the catalyst metal/tungsten oxide interface • At catalyst metal/tungsten oxide/gas interface

  18. Response of Chemochromic – nano-particles

  19. Response of a Chemochromic– PVA water-base “Smart Paint”

  20. Thin film indication threshold in air is less than 400 ppm H2

  21. Chemochromic indicators respond more quickly at higher temperatures

  22. A protective coating reduces the effect of humidity

  23. Indicator response slows over time

  24. Different film structures reduce the rate of response slowing

  25. NASA/KSC Project

  26. H2 Dispensing Station

  27. H2 Dispensing Station

  28. H2DispensingStation

  29. RFID H2 Sensor Network

  30. RFID Hydrogen Sensors

  31. RFID Response

  32. On-going R&D Activities • Optimize nano-particle pigment • Catalyst choice Pd, Pt, or mixed • Catalyst concentration • Possible protective coatings • Select suitable paint vehicles • Optimize paint formulations for various applications • Field test prototype indicators in realistic environments • Optimize thin film coating for polymer substrates • Optimize film component proportions • Improve protective coatings to stabilize response over longer time

  33. Range of Products

  34. Conclusions • Present indicators are promising for leak detection in many applications • New designs are being developed with slower rates of degradation • Performance parameters can be modified for specific applications and requirements

  35. Partnerships • Actively seeking industry partners • Strategic • Testing • Manufacturing

  36. Thank you! www.elem1.com

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