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).
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
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.
We report on a systematic investigation of newly developed (Fe70Ni30)80Nb4B14Si2 metal amorphous nanocomposites (MANCs) and the factors affecting their surface roughness, including oxide formation ...and phase evolution during the nanocrystallization process. Analysis of surface roughness using atomic force microscopy (AFM) revealed an average roughness of 9.33 nm after heat treatment compared with as-cast amorphous ribbons, which exhibited a roughness of 4.21 nm. A surface oxide layer thickness has been determined using X-ray photoelectron spectroscopy (XPS). For samples annealed at 400 °C for 1 h, 450 °C for 1 h, and 550 °C for 3 h in air, the average surface oxide layer thickness was determined to be 10.9, 11.7, and 54.4 nm, respectively. It was observed that oxygen is enriched at the outermost surface and decreases rapidly as the XPS sputtering depth increases. Fe-oxide appeared as a predominant metal oxide at the top surface, followed by the presence of Nb oxide. A boron content increase was observed at the interface between the top surface oxide layer and the bulk of the sample. A protective surface oxide layer on FeNi-MANCs, such as observed in this work, can provide sufficient electrical insulation to reduce interlaminate eddy current losses and lower overall losses in magnetic components.
•Surface roughness and oxidation of FeNi-based metal amorphous nanocomposites.•Surface roughness in amorphous ribbon using atomic force microscopy (AFM).•Crystallization and activation energies in metal amorphous nanocomposite ribbons.•Phase fractions in metal amorphous nanocomposite ribbons.•Surface oxides partitioning in amorphous and nanocrystalline alloys.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact ...on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment.
Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an intriguing optical effect of silica that, depending on ...the solution pH, amplifies or attenuates the optical absorption of a variety of embedded optically active materials with very distinct properties, such as plasmonic Au nanoparticles, non-plasmonic Pt nanoparticles, and the organic dye rhodamine B (not a pH indicator), coated on an optical fiber. Interestingly, the observed optical response to varying pH appears to follow the surface charge density of the silica matrix for all the three different optically active materials. To the best of our knowledge, this optical effect has not been previously reported and it appears universal in that it is likely that any optically active material can be incorporated into the silica matrix to respond to solution pH or surface charge density variations. A direct application of this effect is for optical pH sensing which has very attractive features that can enable minimally invasive, remote, real time and continuous distributed pH monitoring. Particularly, as demonstrated here, using highly stable metal nanoparticles embedded in an inorganic silica matrix can significantly improve the capability of pH sensing in extremely harsh environments which is of increasing importance for applications in unconventional oil and gas resource recovery, carbon sequestration, water quality monitoring, etc. Our approach opens a pathway towards possible future development of robust optical pH sensors for the most demanding environmental conditions. The newly discovered optical effect of silica also offers the potential for control of the optical properties of optically active materials for a range of other potential applications such as electrochromic devices.
Thermal processing of soft magnetic amorphous and nanocrystalline alloys is explored under the influence of radio‐frequency induction‐heating techniques. Direct induction‐heating concepts based on ...longitudinal and transverse flux heating are examined and the details of electromagnetic fields interaction with metallic strips are discussed by analytical calculations as well as finite element analysis. Initial experimental results confirming spatial control of phase transformations and nanocrystallization within a single strip of Finemet Fe‐based amorphous ribbons are reported. The degree to which primary and secondary crystallization temperature are achieved depends on the spacing between the ribbon relative to the induction coil as well as the coil design and configuration. For transverse coil configurations, the local temperature and therefore microstructural evolution is different across the lateral dimension of processed ribbons, with reduced gap sizes producing enhanced peak temperatures and larger temperature distributions with greater spatial variation in microstructure. In addition, indirect susceptor‐based induction heating under tension is performed and the impact of microstructure is demonstrated. Herein, potential for exploiting spatially optimized phase transformations is illustrated through electromagnetic field–assisted processing in a scalable manufacturing process with amorphous and nanocrystalline soft magnetic alloys.
Radio‐frequency rapid thermal processing enables spatial phase transformation and selective nanocrystallization of soft magnetic amorphous alloy ribbons. The article features novel concepts of induction heating including longitudinal‐, transverse‐, and susceptor‐based techniques providing a viable and attractive pathway toward scalable manufacturing techniques for thermal processing of amorphous and nanocrystalline alloys leveraging electromagnetic field–assisted processing methods.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Au-nanoparticle incorporated metal oxide based sensing layers show significant promise for high temperature optical sensing applications at temperatures approaching 800°C or even higher depending ...upon the base oxide material. Several Au-nanoparticle incorporated oxide systems were synthesized and investigated here, namely TiO2, ZrO2, and Yttria-Stabilized Zirconia (YSZ). Gas (CO, H2, and O2) and temperature sensing responses were observed at wavelengths near the localized surface plasmon resonance (LSPR) absorption peak of the Au nanoparticles and addition of 1% O2 content to a N2 baseline gas stream resulted in significantly enhanced recovery kinetics for H2 sensing. TiO2 films with a relatively small bandgap as compared to ZrO2 and YSZ enabled band-edge monitoring yielding a strong temperature sensing response with minimal cross-correlation to changes in gas composition. Testing of the films in high H2-level gas streams demonstrated that monotonic responses to H2 up to 98% H2 by volume in 2% O2 balance N2 gas streams could be achieved by interrogation at wavelengths shorter than the transmittance minimum associated with the Au LSPR absorption peak. These results collectively demonstrate the importance of careful wavelength selection or broadband wavelength interrogation to minimize cross-correlation between composition and temperature and to optimize the gas sensing response in high temperature gas streams. Although the tested films were stable in the presence of simple gas mixtures (N2, H2, CO, O2) used for gas and temperature sensing experiments, a preliminary study of film stability in a contaminated (H2S-containing) high temperature fuel gas stream relevant for solid oxide fuel cell applications was also carried out and yielded two important conclusions deserving further investigation: (1) enhanced microstructural stability of Au nanoparticle incorporated TiO2 due to grain boundary pinning and (2) significant mass loss of Au with an associated reduction in LSPR absorption.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Single crystal fibers of good optical quality were grown by LHPG technique.•Radial dopant segregation in single crystal fiber controlled by growth speed.•Preferential radial segregation of Nd ions ...compared to Ho ions indicating dependence of segregation on size of dopant.•Sol-gel based technique to add Ho dopants to single crystal YAG fiber is demonstrated.•The calculated Δn due to segregation of Nd ions for such a fiber was determined to be 1.2 × 10−4.
In this study, we report self-segregation of dopants in a crystal matrix within a single crystal (SC) fiber. Neodymium and holmium-doped yttrium aluminum garnet (YAG) fibers were grown using the Laser Heated Pedestal Growth (LHPG) technique and cross-sectional dopant concentration was measured using electron-probe micro-analysis. It was observed that the degree of auto-segregation of the rare-earth dopant depended on the difference in ionic size of the dopant ion and the Y3+ ion in the YAG matrix. While holmium showed little tendency to self-segregate, the concentration of neodymium ions varied as much as 25% across the cross-section of the fiber. Strong correlation between the dopant concentration profile and fiber draw speed was also demonstrated. Since the local refractive index depends on the concentration of dopants, a refractive index profile can be achieved by a dopant profile across the fiber cross-section. Engineered index profiles can be realized by varying growth conditions, dopants, crystal matrix, etc. Such an approach is promising in applications such as the development of monolithic SC fibers with graded-index profiles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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