This paper presents a method of using femtosecond laser inscribed nanograting as low-loss– and high-temperature–stable in-fiber reflectors. By introducing a pair of nanograting inside the core of a ...single-mode optical fiber, an intrinsic Fabry-Perot interferometer can be created for high-temperature sensing applications. The morphology of the nanograting inscribed in fiber cores was engineered by tuning the fabrication conditions to achieve a high fringe visibility of 0.49 and low insertion loss of 0.002 dB per sensor. Using a white light interferometry demodulation algorithm, we demonstrate the temperature sensitivity, cross-talk, and spatial multiplexability of sensor arrays. Both the sensor performance and stability were studied from room temperature to 1000°C with cyclic heating and cooling. Our results demonstrate a femtosecond direct laser writing technique capable of producing highly multiplexable in-fiber intrinsic Fabry-Perot interferometer sensor devices with high fringe contrast, high sensitivity, and low-loss for application in harsh environmental conditions.
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.
This study presents a framework for detecting mechanical damage in pipelines, focusing on generating simulated data and sampling to emulate distributed acoustic sensing (DAS) system responses. The ...workflow transforms simulated ultrasonic guided wave (UGW) responses into DAS or quasi-DAS system responses to create a physically robust dataset for pipeline event classification, including welds, clips, and corrosion defects. This investigation examines the effects of sensing systems and noise on classification performance, emphasizing the importance of selecting the appropriate sensing system for a specific application. The framework shows the robustness of different sensor number deployments to experimentally relevant noise levels, demonstrating its applicability in real-world scenarios where noise is present. Overall, this study contributes to the development of a more reliable and effective method for detecting mechanical damage to pipelines by emphasizing the generation and utilization of simulated DAS system responses for pipeline classification efforts. The results on the effects of sensing systems and noise on classification performance further enhance the robustness and reliability of the framework.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Timely detection of the incipient fault of a power transformer is of utmost importance to prevent potential malfunctioning. Monitoring the condition of the transformer insulation oil is the essential ...step as it contains most of the transformer's health diagnostic information. Thus, the temperature of the oil is considered the most crucial parameter that has to be monitored continuously in real-time. Distributed optical fiber sensors for temperature monitoring has various advantages over traditional methods. In this study, an optical fiber-based distributed temperature measurement of insulation oil of a fully energized 100 kVA commercial distribution transformer is demonstrated. Two types of techniques were deployed to monitor the temperature of the transformer inside and outside of the tank using a distributed Optical Frequency Domain Reflectometry (OFDR) and a quasi-distributed Fiber Bragg Grating (FBG) sensor array respectively. The insulation oil temperature was monitored with different load conditions in a distributed fashion and compared with the conventional method of single point thermocouple and infrared thermal imaging. The test results show very good agreement between the conventional methods and proposed distributed fiber temperature sensors.
Metal amorphous nanocomposites (MANCs) are promising soft magnetic materials (SMMs) for power electronic applications offering low power loss at high frequency and maintaining a relatively high flux ...density. While applications in certain motor designs have been recently modeled, their widespread application awaits scaled manufacturing of MANC materials and proliferation of new higher speed motor designs. A hybrid motor design based on permanent magnets and doubly salient stator and rotor is reported here to develop a compact (a factor of 10 smaller than currently possible in Si steels), high-speed (>1 kHz, electrical), high-power (>2.5 kW) motor by incorporating low loss (<10 W/kg at 1 kHz) MANCs such as recently reported Fe-Ni-based alloys. A feature of this motor design is flux focusing from the permanent magnet allowing use of lower energy permanent magnet chosen from among non-rare earth containing compositions and attractive due to constraints posed by rare earth criticality. A 2-D finite element analysis model reported here indicates that a 2.5 kW hybrid motor may be built with a permanent magnet with a 0.4 T remanence at a rotor speed of 6000 rpm. At a magnetic switching frequency of 1.4 kHz, the core loss may be limited to <3 W by selecting an appropriate MANC SMM. The projected efficiency exceeds 96% not including power loss in the controller. Under full load conditions, the flux density distributions for the SMM stay predominantly <1.3 T, the saturation magnetization of optimized FeNi-based MANC alloys. The maximum demagnetizing field in the permanent magnet is less than <inline-formula> <tex-math notation="LaTeX">2.2 \times 10^{5} </tex-math></inline-formula> A/m sustainable, for example, with a high-grade hard ferrite magnet.
The ability to monitor gas species selectively, sensitively, and reliably in extreme temperatures and harsh conditions is critically important for more efficient energy production using conventional ...fossil energy based production technologies, enabling advanced technologies for fossil based power plants of the future, and improving efficiency in domestic manufacturing industries. Optical waveguide based sensing platforms have become increasingly important but a need exists for materials that exhibit useful changes in optical properties in response to changing gas atmospheres at high temperatures. In this manuscript, the onset of a near-IR absorption associated with an increase in free carrier density in doped metal oxide nanoparticles to form so-called conducting metal oxides is discussed in the context of results obtained for undoped and Al-doped ZnO nanoparticle based films. Detailed film characterization results are presented along with measured changes in optical absorption resulting from various high temperature treatments in a range of gas atmospheres. Optical property changes are also discussed in the context of a simple model for optical absorption in conducting metal oxide nanoparticles and thin films. The combination of experimental results and theoretical modeling presented here suggests that such materials have potential for high temperature optical gas sensing applications. Simulated sensing experiments were performed at 500°C and a useful, rapid, and reproducible near-IR optical sensing response to H2 confirms that this class of materials shows great promise for optical gas sensing.
•Near-IR absorptance is affected by high temperature gas streams in Al-doped ZnO.•Optical modeling confirms near-IR absorptance is due to free carriers.•Conducting oxide films show promise for high temperature optical gas sensing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The performance of electrochemical devices depends on the three-dimensional (3D) distributions of microstructural features in their electrodes. Several mature methods exist to characterize 3D ...microstructures over the microscale (tens of microns), which are useful in understanding homogeneous electrodes. However, methods that capture mesoscale (hundreds of microns) volumes at appropriate resolution (tens of nm) are lacking, though they are needed to understand more common, less ideal electrodes. Using serial sectioning with a Xe plasma focused ion beam combined with scanning electron microscopy (Xe PFIB-SEM), two commercial solid oxide fuel cell (SOFC) electrodes are reconstructed over volumes of 126 × 73 × 12.5 and 124 × 110 × 8 μm3 with a resolution on the order of ≈ 503 nm3. The mesoscale distributions of microscale structural features are quantified and both microscale and mesoscale inhomogeneities are found. We analyze the origin of inhomogeneity over different length scales by comparing experimental and synthetic microstructures, generated with different particle size distributions, with such synthetic microstructures capturing well the high-frequency heterogeneity. Effective medium theory models indicate that significant mesoscale variations in local electrochemical activity are expected throughout such electrodes. These methods offer improved understanding of the performance of complex electrodes in energy conversion devices.
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•Large volume 3D reconstructions of SOFC electrodes are achieved using Xe PFIB-SEM.•PFIB reconstructions enable scale-bridging characterization of properties.•Significant variation exists in microscale structural values over the mesoscale.•Synthetic microstructures model origin of high-frequency microstructural variation.•Significant variation in microscale electrochemistry expected over the mesoscale.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Innovation approach to turn conventional polymer protective coating of optical fibers into functional structures for both methane sensing.•MOF nanocrystallines integrated in PDMS improve gas ...permeability for CH4 and also serve as gas molecule capture and storage agents.•Methane detection limit of 1% was achieved with outstanding repeatability using both Multimode fiber and D-shaped single mode fiber platform.
Functional polymer coating integrated with optical fiber is an intriguing approach to develop low-cost point and distributed fiber sensors for large-scale applications. This paper presents the development of gas-sensitive coatings for both single-mode and multi-mode optical fibers through the application of polymer/nanocrystalline metal-organic frameworks (MOFs) composites as methane sensors for monitoring natural gas infrastructure. Silicone polymers based on PDMS with optimized optical and mechanical properties were developed as host materials for the well-known metal organic framework ZIF-8. Integration of ZIF-8 nanocrystals within the PDMS polymer modified the physical properties of the material and led to an enhancement of the CH4 solubility and permeability of the resulting film. The refractive indices, viscosities, and mechanical properties of the ZIF-8 functionalized polymers were optimized by adjusting the ZIF-8/polymer weight ratio and subsequently used as the fiber coating. Both multi-mode and single-mode optical fibers coated with the MOF-functionalized polymers showed scaled changes in transmitted power upon exposure to various concentration of CH4 in a N2 carrier gas. The variations in transmitted power through the fiber were the result of changes in evanescent wave interactions with the sensor coating due to shifts in the polymer cladding refractive index upon CH4 sorption. A methane detection limit of 1 % in nitrogen was achieved using both multimode fiber and D-shaped single mode fibers. Overall, our paper presents a low-cost approach to perform point and distributed sensing for CH4 through an innovative method of functional polymer material integration on optical fiber sensor platforms.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Controllable and fast heating profiles provide unique capabilities to realize enhanced soft magnetic properties of amorphous and nanocrystalline materials in conventional nanocrystalline alloys, as ...well as alloy chemistries for which carefully controlled annealing processes play a critical role in realizing desired properties tailored within a large degree of flexibility. This review aims to identify the fundamental physical phenomena in rapid thermal processing of amorphous and nanocrystalline soft magnetic alloys and to provide a comprehensive summary on the progress made to improve their performance, with an emphasis on processing in electromagnetic fields. The review begins with general background on fundamental concepts of electromagnetic heating and aspects of heat transfer followed by a detailed description of rapid thermal processing techniques employed over the relevant frequency range. These include; Joule heating, induction heating, microwave heating, and laser-assisted surface heating. In addition, traditional methods enabling high heating rates are included and reviewed accordingly. Influences of processing parameters and the detailed mechanism of heating are discussed with an assessment of experimental observations reported in the literature and further validated by simulations. Phase transformations and crystallization processes are discussed in the context of nucleation and growth kinetics, with a demonstration of thermal processing routes and alloy design. A critical evaluation of structural and magnetic properties are provided, and the underlying role of heating rates and magnetic anisotropies are highlighted. An outlook for future development trends and a number of challenges in this field are presented.
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•Microstructural engineering at the nanoscale in nanocomposite soft magnetic materials.•Fundamentals of electromagnetic heating and energy transfer at the nanoscale.•Enhancing materials performance via rapid thermal processing and alloy optimization.•Spatially selective thermal processing using techniques such as radio frequency induction heating and laser annealing.•Comprehensive summary of experimental results reported in the literature to date.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Active sites and structure–activity relationships for methanol synthesis from a stoichiometric mixture of CO2 and H2 were investigated for a series of coprecipitated Cu-based catalysts with ...temperature-programmed reduction (TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N2O decomposition. Experiments in a reaction chamber attached to an XPS instrument show that metallic Cu exists on the surface of both reduced and spent catalysts and there is no evidence of monovalent Cu+ species. This finding provides reassurance regarding the active oxidation state of Cu in methanol synthesis catalysts because it is observed with 6 compositions possessing different metal oxide additives, Cu particle sizes, and varying degrees of ZnO crystallinity. Smaller Cu particles demonstrate larger turnover frequencies (TOF) for methanol formation, confirming the structure sensitivity of this reaction. No correlation between TOF and lattice strain in Cu crystallites is observed suggesting this structural parameter is not responsible for the activity. Moreover, changes in the observed rates may be ascribed to relative distribution of different Cu facets as more open and low-index surfaces are present on the catalysts containing small Cu particles and amorphous or well-dispersed ZnO. In general, the activity of these systems results from large Cu surface area, high Cu dispersion, and synergistic interactions between Cu and metal oxide support components, illustrating that these are key parameters for developing fundamental mechanistic insight into the performance of Cu-based methanol synthesis catalysts.
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