SAW Sensors for Chemical Vapors and Gases Devkota, Jagannath; Ohodnicki, Paul R; Greve, David W
Sensors (Basel, Switzerland),
04/2017, Volume:
17, Issue:
4
Journal Article
Peer reviewed
Open access
Surface acoustic wave (SAW) technology provides a sensitive platform for sensing chemicals in gaseous and fluidic states with the inherent advantages of passive and wireless operation. In this ...review, we provide a general overview on the fundamental aspects and some major advances of Rayleigh wave-based SAW sensors in sensing chemicals in a gaseous phase. In particular, we review the progress in general understanding of the SAW chemical sensing mechanism, optimization of the sensor characteristics, and the development of the sensors operational at different conditions. Based on previous publications, we suggest some appropriate sensing approaches for particular applications and identify new opportunities and needs for additional research in this area moving into the future.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Fiber optic sensor technology offers several advantages for harsh-environment applications. However, the development of optical gas sensing layers that are stable under harsh environmental conditions ...is an ongoing research challenge. In this work, electronically conducting metal oxide lanthanum-doped strontium titanate (LSTO) films embedded with gold nanoparticles are examined as a sensing layer for application in reducing gas flows at high temperature (600-800 °C). A strong localized surface plasmon resonance (LSPR) based response to hydrogen is demonstrated in the visible region of the spectrum, while a Drude free electron-based response is observed in the near-IR. Characteristics of these responses are studied both on planar glass substrates and on silica fibers. Charge transfer between the oxide film and the gold nanoparticles is explored as a possible mechanism governing the Au LSPR response and is considered in terms of the corresponding properties of the conducting metal oxide-based matrix phase. Principal component analysis is applied to the combined plasmonic and free-carrier based response over a range of temperatures and hydrogen concentrations. It is demonstrated that the combined visible and near-IR response of these films provides improved versatility for multiwavelength interrogation, as well as improved discrimination of important process parameters (concentration and temperature) through application of multivariate analysis techniques.
Coupled plasmonic and Drude response of gold-nanoparticle incorporated LSTO demonstrates visible and NIR fiber-based sensing of hydrogen at high-temperature (600-800 °C).
Applications of fiber optic sensors to battery monitoring have been increasing due to the growing need of enhanced battery management systems with accurate state estimations. The goal of this review ...is to discuss the advancements enabling the practical implementation of battery internal parameter measurements including local temperature, strain, pressure, and refractive index for general operation, as well as the external measurements such as temperature gradients and vent gas sensing for thermal runaway imminent detection. A reasonable matching is discussed between fiber optic sensors of different range capabilities with battery systems of three levels of scales, namely electric vehicle and heavy-duty electric truck battery packs, and grid-scale battery systems. The advantages of fiber optic sensors over electrical sensors are discussed, while electrochemical stability issues of fiber-implanted batteries are critically assessed. This review also includes the estimated sensing system costs for typical fiber optic sensors and identifies the high interrogation cost as one of the limitations in their practical deployment into batteries. Finally, future perspectives are considered in the implementation of fiber optics into high-value battery applications such as grid-scale energy storage fault detection and prediction systems.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Corrosion has been a great concern in the oil and natural gas industry costing billions of dollars annually in the U.S. The ability to monitor corrosion online before structural integrity is ...compromised can have a significant impact on preventing catastrophic events resulting from corrosion. This article critically reviews conventional corrosion sensors and emerging sensor technologies in terms of sensing principles, sensor designs, advantages, and limitations. Conventional corrosion sensors encompass corrosion coupons, electrical resistance probes, electrochemical sensors, ultrasonic testing sensors, magnetic flux leakage sensors, electromagnetic sensors, and in-line inspection tools. Emerging sensor technologies highlight optical fiber sensors (point, quasi-distributed, distributed) and passive wireless sensors such as passive radio-frequency identification sensors and surface acoustic wave sensors. Emerging sensors show great potential in continuous real-time in-situ monitoring of oil and natural gas infrastructure. Distributed chemical sensing is emphasized based on recent studies as a promising method to detect early corrosion onset and monitor corrosive environments for corrosion mitigation management. Additionally, challenges are discussed including durability and stability in extreme and harsh conditions such as high temperature high pressure in subsurface wellbores.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The effect of HCO3−(aq) on CO2 corrosion of carbon steel was investigated in deaerated 3.5 wt% NaCl solutions at 30 °C from pH 3.96 to 7.15. In the CO2-saturated solutions, the pH was adjusted with ...different HCO3−(aq) concentrations, cHCO3−(aq). The corrosion rate decreased by a factor of 2 as the pH and cHCO3−(aq) increased. The cathodic current density during polarization increased at higher pH with higher cHCO3−(aq), indicating that HCO3−(aq) acted as an additional hydrogen source for the hydrogen evolution reaction. As the pH increased, the active dissolution regions displayed similar anodic Tafel slopes and suggested a modified Bockris mechanism for the Fe oxidation reaction. The exchange current densities for the half reactions were calculated to study kinetics of the anodic and cathodic half reactions independently. The anodic exchange current density (j0,a) increased by one order of magnitude in the presence of CO2, indicating the involvement of CO2(aq) in the Fe oxidation reaction. As the pH and cHCO3−(aq) increased, the cathodic exchange current density (j0,c) decreased by a factor of 50 because the increase in j0,cHCO3−(aq) was not high enough to compensate the decline from the other hydrogen sources, especially j0,cH+(aq); and j0,a decreased by a factor of 2.4 because HCO3−(aq) may have competed with CO2(aq) for the surface coverage and the increase in j0,aHCO3−(aq) could not compensate the decrease in j0,aCO2(aq). It suggests that the reaction rate constant of HCO3−(aq) was smaller than CO2(aq) for the anodic half reaction and was smaller than H+(aq) for the cathodic half reaction. The XPS results verified that the corrosion products transitioned from iron carbonate to hydroxide as the pH increased while iron carbonate remained the major product. As the pH increased with HCO3−(aq), a second time constant was observed at lower frequencies of the electrochemical impedance spectroscopy (EIS) results.
•HCO3− acted as an additional hydrogen source for the cathodic reaction.•Active dissolution mechanism was discussed based on anodic Tafel slopes.•Half reactions were studied independently on the effect of HCO3−.•CO2(aq) was verified to participate in the Fe oxidation reaction.•Corrosion products transitioned from iron carbonate to hydroxide as pH increased.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Rare earth elements (REEs) are widely used in high-performance technologies including wind turbine magnets, electric vehicle batteries, lighting displays, circuitry, and national defense systems. A ...combination of projected increasing demand for REEs, monopolistic economic conditions, and environmental hazards associated with the mining and separation of REEs has led to significant interest in recovering REEs from alternative sources such as coal waste streams. However, rapidly locating high-value waste streams in the field remains a significant challenge primarily because of slow analytical methods, and existing techniques with low limits of detection such as inductively-coupled plasma mass spectrometry suffer from high equipment and operating costs and a lack of portability. Alternatively, luminescence-based sensors for REEs present a potential path for sensitive, portable, low-cost detection. The development and design of materials suitable for the luminescence-based detection of REEs are crucial to realizing this potential. Here, we review a broad range of materials used (or that have the potential to be used) for REE luminescence-based detection, including organic compounds, biomolecules, polymers, metal complexes, nanoparticles, and metal-organic frameworks. A general overview of REE optoelectronic properties and luminescent sensing protocols is first presented, followed by analyses of material-specific sensing mechanisms, emphasizing sensing figures of merit including sensitivity, selectivity, reusability and portability. The review concludes with a discussion of remaining barriers to luminescent REE sensing, how each sensor class may be best deployed, and directions for future material and spectrometer design. Taken together, this review provides a broad overview of sensing materials and methods that should be foundational for the continued development of high-performance sensors.
A range of materials are evaluated for their ability to detect and quantify rare earth elements
via
luminescence techniques.
We examine the application of guided waves on a single conductor (Goubau waves) for sensing. In particular, the use of such waves to remotely interrogate surface acoustic wave (SAW) sensors mounted ...on large-radius conductors (pipes) is considered. Experimental results using a small-radius (0.0032 m) conductor at 435 MHz are reported. The applicability of published theory to conductors of large radius is examined. Finite element simulations are then used to study the propagation and launching of Goubau waves on steel conductors up to 0.254 m in radius. Simulations show that waves can be launched and received, although energy loss into radiating waves is a problem with current launcher designs.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Plasmonic excitation of Au nanoparticles attached to the surface of ZnO catalysts using low power 532 nm laser illumination leads to significant heating of the catalyst and the conversion of CO2 and ...H2 reactants to CH4 and CO products. Temperature-calibrated Raman spectra of ZnO phonons show that intensity-dependent plasmonic excitation can controllably heat Au-ZnO from 30 to ~600 °C and simultaneously tune the CH4 : CO product ratio. The laser induced heating and resulting CH4 : CO product distribution agrees well with predictions from thermodynamic models and temperature-programmed reaction experiments indicating that the reaction is a thermally driven process resulting from the plasmonic heating of the Au-ZnO. The apparent quantum yield for CO2 conversion under continuous wave (cw) 532 nm laser illumination is 0.030%. The Au-ZnO catalysts are robust and remain active after repeated laser exposure and cycling. The light intensity required to initiate CO2 reduction is low (~2.5 × 10(5) W m(-2)) and achievable with solar concentrators. Our results illustrate the viability of plasmonic heating approaches for CO2 utilization and other practical thermal catalytic applications.
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