Harsh Operating Conditions Research Articles

Unveiling High Performance Solder Alloys for Automotive Applications

Vehicle electrification and advances in autonomous driving technologies are creating unique opportunities and challenges in the automotive electronics assembly industry. The ever-increasing demand of reliability at higher temperatures and longer service life, especially for automotive electronics, is leading to the evolution of high reliability solder alloy design in the electronics assembly industry. The combination of harsh operating conditions, increasing power densities, and miniaturization has added to the complexity of assembly designs in the automotive electronics market for which traditional surface mount solders are no longer applicable. Thermo-mechanical reliability of solder alloys under harsh operating conditions has been a primary factor for defining suitability and selection of solder alloy for next generation designs. A next generation high reliability alloy for automotive electronics is introduced herein. The microstructure of this novel alloy consists of a well-distributed eutectic phase and finely distributed precipitates of intermetallic compounds which contributes towards solid solution strengthening as well as precipitation strengthening. It is shown that a high-temperature superior creep strength improvement of more than 100% over existing high reliability alloys is achieved at temperatures of 150°C. This and other mechanical properties of the bulk alloy are then correlated to performance with thermal cycling testing under extreme conditions. The novel alloy showed significantly higher thermal cycling performance, exhibiting more than 40% increase in the characteristic life over other existing high-reliability alloys while maintaining traditional surface mount target reflow temperatures. Considering these results, this new class of alloys has the capability to meet the increasingly challenging reliability requirements of automotive electronics.

Design-oriented method for concrete pavements with volumetric stability admixtures: An integrated experimental and analytical approach

The high-performance demands on industrial floors, both in terms of larger slab dimensions and increased durability under harsh operating conditions, have led to the growing use of expansive admixtures. These generate a controlled expansive reaction within the concrete and compensate the early-age shrinkage. Despite their increasing use, calculation methods that permit to consider the expansive agents during the pavement design phase with a certain level of reliability are still unexistent. This study presents a straightforward cross-sectional model to assess both the stress-strain state and joint-opening of concrete pavements with volumetric stability admixtures by considering the slab dimensions, concrete composition, exposure conditions, and base friction characteristics. For that, a novel experimental device is designed and implemented in this work to characterize the dimensional variations associated with expansive agents since casting. A Type-G commercial volumetric stability admixture is considered as the expansive admixture. A full-scale validation of the proposed model is performed on a jointless concrete panel constructed by RCR Industrial Flooring in Spain. This validation proves the feasibility of the combined approach of laboratory calibration of the expansive addition and the cross-sectional model presented to accurately estimate both the slab deformations and joint opening developed over the 77-day test period.

A New Multi-Physics Coupled Method for the Temperature Field of Dry Clutch Assembly

The temperature field of the clutch assembly is critical for the clutch design and operation life. Current modeling methods of the temperature of the clutch assembly suffer from insufficient accuracy or a limited time scale for the complicated multi-physics coupling between the contact force, friction-generated heat, heat transfer, and thermal deformation in the clutch assembly in harsh operation conditions. In order to improve the accuracy of temperature field simulation and achieve long-term time scale, a new approach to modeling the temperature is proposed based on CFD simulation and decoupling technology. Firstly, the flow-thermal bi-directional coupling method is employed to determine the convective boundary conditions between the clutch assembly and the ambient air, improving the model’s accuracy. Secondly, the thermal-solid decoupling method is then used to reduce the computational time. The temperature of the clutch assembly during the continuous engagement and disengagement process is performed using this approach and verified by the rig test. The results demonstrate that the temperature of the outer, middle, and inner diameters of the pressure plate by the model agrees well with that by the rig test. For the first engagement and disengagement processes, the proportion of simulated temperature deviations exceeding 5 °C from the measured data is only 3.03%. For the last engagement and disengagement process, while the maximum temperature of the clutch is above 350 °C, the maximum temperature deviation between simulation and measurement is 4.99%. It proves that the approach proposed for modeling the dry clutch assembly temperature field has high accuracy while achieving long-term time-scale simulation.

Triple heat treatment effects of Inconel X-750 superalloy on its microstructure, hardness, and high-temperature fretting wear characteristics

Inconel X-750 alloy specimens were undergone the triple heat treatment process: solution annealing (1149 °C/2h), equalization treatment (843 °C/24h), and precipitation treatment (704 °C/20h). Then microstructure characterization and hardness tests were performed prior to the self-mated pin-on-disk fretting wear tests in the range of 25 °C-650 °C temperature conditions. This type of alloys is widely used in bump-type gas foil bearing applications where complex fretting phenomenon occurs between foils under harsh operating conditions. Conducted investigations revealed that the heat-treated sample developed more precipitated phases in the matrix and along the grain boundaries with higher bulk hardness. Fretting wear surface morphologies indicate that the formation of glaze layer composed of NiO, Cr2O3, and mixed Ni(Fe,Cr)2O4 oxides prevail on the wear scar during the elevated temperatures, harnessing significantly lower friction coefficient and wear loss. Severe material transfers and galling were the dominant wear mechanism in the non-heat-treated alloy interface which caused the stick-slip frictional behavior. On the contrary, the heat-treated alloy surfaces demonstrated the stable coefficient of friction and 3–10 times lower wear rates at high temperatures due to the additional Cr-rich carbides. It is believed that these hard and lubricious Cr2O3 internal oxide precipitates form healing glaze barrier in the interface by protecting against severe material transfer/build-up.

Artificial Neural Network Based Wear and Tribological Analysis of Al 7010 Alloy Reinforced with Nanoparticles of SIC for Aerospace Application

The current study investigates the wear behavior of three distinct composite compositions designated as C1, C2, and C3, with direct implications for aerospace applications. Critical factors such as the Coefficient of Friction (Cf), Specific Rate of Wear (Sw), and Frictional Force (FF) were meticulously analyzed using a systematic experimental approach and the Taguchi L27 array design. Significant relationships between input factors and responses emerged after subjecting these responses to Taguchi signal-to-noise ratio analysis. The optimal parameter combination of a 5% composition, 14.5 N Applied Load (Ap), 150 rpm Rotational Speed (Rs), and 40.5 m Distance of Sliding (Ds) highlights the interplay of factors in improving wear resistance. An Artificial Neural Network (ANN) was used as a predictive tool to boost research efficiency, achieving an impressive 99.663% accuracy in response predictions. The result shows comparison of the ANN's efficacy with actual experimental results. These findings hold great promise for aerospace applications where wear-resistant materials are critical for long-term performance under harsh operating conditions. The incorporation of ANN predictions allows for rapid material optimization while adhering to the stringent requirements of aerospace environments. This research contributes to the evolution of tailored composite materials, poised to improve aerospace applications with increased reliability, efficiency, and durability by advancing wear analysis methodologies and predictive technologies.

Prediction of the belt drive contamination status based on vibration analysis and artificial neural network

Belt drive contamination is considered one of the most common failure modes that could be developed in the belts due to harsh operation conditions, high humidity, and sunlight exposure, reducing the belt’s performance. If the belt failure has not been detected early, a sudden shutdown may happen, producing safety and economic consequences. However, most maintenance personnel use their senses of sight, hearing, smell, and touch to identify the cause of the problem while diagnosing a belt drive condition. Hence, this research involves developing an intelligent contamination status detection system based on vibration signal analysis for a pulley-belt rotating system. Time-domain signal analysis was employed to extract some suggestive features such as the root mean square, kurtosis, and skewness from the vibration data. An artificial neural network (ANN) model was built to detect the simulated different operating conditions. The vibration data was gathered with the help of two MEMS accelerometers (ADXL335) interfaced with an NI USB-6009 data acquisition device. A signal capture, analysis, and feature extraction system was developed using Matlab Simulink. The simulated operating conditions include clean, wet, and powder-contaminated belts. The results showed that the designed system could identify the pulley-belt operation conditions with 100% overall accuracy.

Natural Convection in Molten Salt Electrochemistry.

Molten salt electrochemistry has been widely used in many fields, especially for metal extraction/refinement. The understanding of mass transfer in molten salts under harsh operation conditions is of great importance to reveal reaction mechanisms and advance fine technologies. It has been generally assumed that natural convection is negligible in stagnant molten salt electrochemistry. Herein, we report an abnormal natural convection in molten LiCl-KCl, with the arising time from 2.37 s at 873 K to 10.13 s at 673 K. Using the concentration correction factor, the derived thickness of the natural convection-diffusion layer (δconv.) was found to be ranging from 128 to 163 μm, much thinner than those in aqueous solutions (∼200 μm). The simulations showed that the notable natural convection resulted from convection-diffusion layer (CDL) convection dominated over the density-driven convection even at high redox concentrations, implying the severe vibration of molten salt systems. To suppress the intense natural convection, we predicted that the use of microelectrodes (with radii less than 23.2 μm for δconv. = 150 μm) would be a promising tool, regardless of their inferior stabilities in high-temperature molten salts at this stage. These innovative findings offer insights into the impact of natural convection on mass transfer in molten salts that have not been previously revealed.

Redox enhanced slow ion kinetics in oxide ceramics

AbstractThere is a growing interest in field‐assisted fast ceramic processing and long‐term service of electrochemical devices under harsh operation conditions. These extreme redox conditions can make some conventionally thought slow ions highly mobile in electrochemical materials and devices and greatly accelerate the microstructural evolution. Experimental observations for enhanced slow ion diffusion that controls mass transport include accelerated grain growth in zirconia and ceria under atmospheric and electrochemical reduction above 1000°C and lattice cavitation of high‐voltage Li‐rich layered cathodes of lithium‐ion batteries at room temperature. These observations cannot be explained by altered defect concentrations under defect chemistry arguments. Instead, they support hugely enhanced slow ion mobility. My colleagues and I recently proposed a new mechanism resulted from strong electron–phonon interactions and dynamic electronic relaxations at the saddle point of an ion hopping event, which significantly lowers the ion migration barrier. In this perspective article, the theory and its experimental and computational supports shall be discussed. Such an electronic effect holds even in nominally ionic ceramic materials with wide bandgaps and is expected to be general in many transition metal oxides. It rationalizes a variety of intriguing experimental observations and offers an electronic perspective on the redox enhancement of slow ion kinetics in structural, functional, and energy ceramics.

Experimental study and comparative analysis of pitting fault in spur gear system

This paper uses a dynamic six-degree-of-freedom model that considers torsional and lateral motions to predict the impact of pitting on vibration parameters in a spur gearbox for various operating speeds and torque loads. The study examines the dynamic characteristics of a gearbox with localized pitting damage on a single gear tooth using theoretical and experimental approaches. The research analyzes the forced vibrations of a single-stage spur gear system with pitting damage, which includes variations in mesh stiffness, damping, and gear error excitation, to identify symptoms of default. The equation of motion for the rotary gearbox system is established using the Lagrangian method in tandem with Short-Time Fourier Transform (STFT) and frequency-RPM map fault diagnosis. During real-time vibration monitoring, vibration signals are captured via accelerometers and processed in both the time and frequency domains using the LabVIEW data acquisition signal processing package to extract diagnostic information. The experimental findings demonstrate how vibration analysis combined with time-frequency processing can recognize machine conditions even in harsh operational conditions. Moreover, the experimental results indicate a significant similarity with the theoretical analysis and validate the effectiveness of the RPM frequency technique-based pitting detection method, which can be an asset in gear fault monitoring.

Highly Durable and Efficient Seawater Electrolysis Enabled by Defective Graphene-Confined Nanoreactor.

Direct seawater electrolysis is a promising technology for massive green hydrogen production but is limited by the lack of durable and efficient electrocatalysts toward the oxygen evolution reaction (OER). Herein, we develop a core-shell nanoreactor as a high-performance OER catalyst consisting of NiFe alloys encapsulated within defective graphene layers (NiFe@DG) by a facile microwave shocking strategy. This catalyst needs overpotentials of merely 218 and 276 mV in alkalized seawater to deliver current densities of 10 and 100 mA cm-2, respectively, and operates continuously for 2000 h with negligible activity decay (1.0%), making it one of the best OER catalysts reported to date. Detailed experimental and theoretical analyses reveal that the excellent durability of NiFe@DG originates from the formation of the built-in electric field triggered by the defective graphene coating against chloride ions at the electrode/electrolyte interface, thus protecting the active NiFe alloys at the core from dissolution and aggregation under harsh operation conditions. Further, a highly stable and efficient seawater electrolyzer is assembled with the NiFe@DG anode and the Pt/C cathode to demonstrate the practicability of the catalysts.

Vortex effects on aerodynamic performance of multi-stage continuous-resistance trim under high pressure gradient

The multi-stage continuous-resistance trim (MSCRT) is widely utilized in gas turbine combined-cycles (GTCC), acting as an indispensable throttling component used for regulating fluid pressure, flow rate and temperature. However, under harsh operating conditions, the flow in MSCRT becomes unstable, leading to disrupted aerodynamic performance and increased energy consumption. Despite its significance, the underlying vortex dynamics and its correlation with aerodynamic performance remain elusive. To address this, a comprehensive investigation into the unsteady flow of MSCRT is proposed, combining experimental and numerical methods. The vortex dynamics mechanism is revealed, and then, the vortex effects on pressure pulsation and aerodynamic performance are investigated. Results show that the novel design allows the pressure gradient to be dissipated between the layers and succeeds in achieving effective control of noise and energy consumption. Based on the aerodynamic design, the mutual correspondence between the vortical structure and the flow field results is verified. Furthermore, the relationship between the instantaneous total vorticity and the pressure pulsation is established, as well as the relationship between the vortex parameters and the maximum sound pressure level. Notably, a linear correlation between the maximum sound pressure level and the maximum instantaneous total vorticity is determined. This study provides support for improving the aerodynamic performance of related throttling components.

Composite fault feature extraction of rolling bearing using adaptive circulant singular spectrum analysis

Aiming to extract the weak composite fault characteristics of a rolling bearing under harsh operation conditions, a novel composite fault diagnosis method for bearings based on adaptive circulant singular spectrum analysis (ACiSSA) is proposed. The proposed method is able to adaptively obtain the eigenvalue of a non-stationary vibration signal in any dimension, and effectively reassemble the same frequency components and improve the signal-to-noise ratio (SNR). Specifically, circulant singular spectrum analysis is utilized to decompose the raw signal, and the optimal parameters, i.e. the embedding dimension and threshold value of cumulative contribution, are selected to maximum kurtosis through the grey wolf optimization method. The signal is reconstructed with high SNR according to the effective singular spectrum components. Envelope demodulation analysis is then implemented to extract the characteristic defect frequency in the reconstructed signal. Finally, feature extraction performance is quantitatively evaluated, and experimental results show that the proposed ACiSSA method is able to extract more sensitive features under more noisy conditions compared with other common methods, with higher computational efficiency.

Intracycle Active Blade Pitch Control for Cross-Flow Tidal Turbines Using Embedded Electric Drive Systems

Cross-flow tidal turbines (CFTTs) have proven advantages over horizontal axis turbines in terms of high power density per unit area, simplicity of design, and operation independence from inflow direction. However, they suffer from an unsteady flow regime which can comprise dynamic blade stall and thus problems of material fatigue or even failure. Active pitch control mechanisms on blade level have been shown to provide a potential solution, when continuously adjusting the pitching angle of each individual blade during the whole rotational cycle of the turbine.
 As part of the research of the OPTIDE project, in this study, electric drive systems embedded in the blades of a CFTT flume model are proposed aiming to realize an active pitch control with high efficiency and fast response. The blade embedded actuation allows for reasonable flow conditions. For full scaled on-site applications this is required to reduce hydrodynamic losses and to protect the actuators and electronics from the harsh environmental and operation conditions. Based on the expected hydrodynamic loads from numerical flow simulations (CFD), several types of actuators are considered. The first type has brushless DC motors installed at both sides of each blade. Along with a gear box with proper reduction ratio, the actuators are able to provide required torque within expected cycle period. The second type of actuator drives the blade directly, which always results in faster pitching action, higher drive efficiency, more accurate positioning of blades, as well as simpler structure. Specifically, the shaft of each blade is designed as the primary of a limited angle torque motor, while the blades are used as the secondary with magnets inside. To mitigate the potential saturation effect on the iron of the primary­, the blade can also be used as the primary, where there always exists much larger space for windings. In this case, the magnets are now located at the shaft. By doing this, it is expected to output larger torque in a wider range of pitching angle as compared with the original one, while almost the same power is required. An experimental test bench for a single blade with both types of actuators is built to verify their ability of a fast and accurate pitching control. This also lays the foundation of identifying the optimal pitching angle for the control and inhibition of dynamic blade stall at various flow conditions and blade positions within the rotational cycle of the turbines. After successful optimization and testing of the model scaled mechatronical design, the actuators will be up scaled for realistic applications.

LUBRICATION OF OFFSHORE MECHANICAL COMPONENTS: TOWARDS SUSTAINABLE & RELIABLE POWER PRODUCTION

As different wave and tidal energy generators advance towards the commercial deployment phase, addressing potential issues related to the lubrication of the machine components integrating the Power Take Off system (PTO) due to the harsh operating conditions encountered in the marine environment becomes even more essential. Environmentally Acceptable Lubricants (EALs) based on water-soluble polymers are proposed as a way to reduce friction and wear of the mechanical components in wave and tidal energy generators. Although these fluids have the advantage of being biodegradable and non-toxic, they have not shown to be as effective as other synthetic fluids, or mineral oils in preventing corrosion, severe friction, and wear, thus increasing the risk of moving parts experiencing premature failure.
 This work explores the potential of different water-soluble polymers to be used in the formulation of EALs that can meet the strict environmental regulations while providing effective protection against wear, and corrosion in offshore operating conditions. To evaluate the potential of these lubricants as an alternative to replace conventional mineral oils, different polymers were analyzed from the point of view of their ability to form an effective full lubricant film that can keep separation between the contacting surfaces, mitigate wear, and prevent corrosion. The rheological properties of these polymers were also studied at different concentrations in order to optimize the performance in the application. The hydrodynamic film build-up properties of EALs formulated with water-soluble polymers with different molecular weight, concentration, and viscosity are reported. The corrosion resistance exhibited by steel components when exposed to the different formulations compared to seawater was an object of examination. The study also aimed to establish correlations between the lubricant film-build up properties, viscosity, and electrical impedance.
 The results showed that high molecular weight polymers can form a separating film at relative high pressure in the low-speed region even at low polymer concentrations. While with the increasing speed, the fluid viscosity becomes more important to sustain a full film between contacting surfaces. With the increasing concentration of polymer in the aqueous solution the open circuit potential (OCP) becomes more negative indicating the deterioration of the steel corrosion resistance.
 The results provide new insights into the design of EALs that can effectively protect the mechanical components of wave and tidal energy generators while minimizing environmental impact. The findings suggest that water-soluble polymers are a promising solution for offshore applications, as they can provide efficient full film lubrication, mitigate wear, and prevent corrosion. These polymers can help to improve the performance and lifespan of offshore power generators while minimizing the environmental impact.

Exploration of a Cellulose-Based Biocompatible Gate Dielectric for Low-Voltage Organic Transistors

In this work, a cellulose-based biocompatible high-k dielectric cyanoethyl cellulose (CEC) is comprehensively explored for demonstration of low-voltage organic transistors. The organic field-effect transistor (OFET) devices fabricated using a blend of TIPS-Pentacene and polystyrene to create the active semiconductor layer exhibited excellent p-channel transistor behavior with maximum and average process transconductance values of ~ 9.0, and ~ 6.0 nF/V.s respectively, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , and average threshold voltage of -0.4 (±0.1) V suitable for sub-5V operation. Moreover, very high electrical stability was achieved from these devices through bias-stress, and repeatability measurements. The device operation was still maintained after 6 months in normal ambient indicating a high shelf life. Finally, there was a minimal variation in performance upon annealing the devices up to 60 °C, indicating high reliability in harsh environmental operating conditions. Our results confirm that CEC can be a potential gate dielectric for organic and biodegradable electronics which is essential for sustainability.

PtZn nanoparticles supported on porous nitrogen-doped carbon nanofibers as highly stable electrocatalysts for oxygen reduction reaction

The oxygen reduction reaction (ORR) electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles (NPs) on a porous carbon support with large surface area. However, such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores, in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support. Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers. Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential (E1/2) of 0.911 ​V versus reversible hydrogen electrode (vs. RHE) and enhanced durability with only decreasing 11 ​mV after 30,000 potential cycles, compared to a more significant drop of 24 ​mV in E1/2 of Pt/C catalysts (after 10,000 potential cycling). Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support, inhibiting the migration and aggregation of NPs during the ORR.

Size-Controlled Synthesis of IrO2 nanoparticles at High Temperatures for the Oxygen Evolution Reaction

Polymer electrolyte membrane (PEM) electrolysis is considered to play a vital role in the sustainable energy transition. The efficient generation of hydrogen is largely influenced by the slow rate of the anodic oxygen evolution reaction (OER). Iridium oxide represents one of the most promising catalysts for the electrochemical oxidation of water in an acidic environment. Under harsh operating conditions at the anode, iridium oxide is found to be among the most dissolution-resistant catalysts while offering acceptable OER activity. However, iridium’s limited availability dictates high costs centralizing the research in direction of reducing noble metal content while maintaining favorable electrochemical properties.[1] Designing nanostructured catalyst with an increased surface-to-volume ratio improves the application-oriented mass-specific activity.[2] Hydrous iridium oxide is known for superior OER activity, but for a successful application, drastic dissolution of the catalyst must be addressed by stabilization. This can be achieved by heat treatment to temperatures ≥400ºC with the formation of crystalline order. However, managing to avoid agglomeration of nanoparticles at high temperatures is not trivial, thus, temperature studies on electrochemical stability and activity on similar particle sizes are missing.[3]. Here, we demonstrate how nanoparticles below 10 nm can be obtained at high preparation temperatures up to 800 °C with unprecedented control over particle size and morphology. A detailed understanding of the structural evolution during heating was obtained by in-situ scanning transmission electron microscopy (in-situ STEM) with locally resolved nanoparticles, high spatial resolution, and chemical specificity. Additionally, changes in surface properties at different temperatures were tracked ex-situ by X-ray photoelectron spectroscopy (XPS), the crystal structure was investigated by X-ray diffraction analysis (XRD), size and morphology were characterized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The OER activities of synthesized iridium oxide nanoparticles were measured in half-cell measurements at forced convection. The stability was carefully studied by operando flow cell measurements that were coupled to online inductively coupled plasma mass spectrometry.[4] The iridium oxide catalyst calcined at the lowest temperature resulted in outstanding mass-specific activity outperforming the reference iridium oxide catalyst by a factor of 40. By gradual increase in calcination temperatures up to 800 °C, we observe improvement in the durability of the synthesized catalysts, being comparable to the reference catalyst, yet still with notable improvement in catalytic activity. This is the first report to synthesize iridium oxide nanoparticles at high temperatures with preserved size and morphology not exceeding 10 nm and allows for the determination of activity and durability of similarly sized nanostructures.[5] Literature:[1] M. Bernt et al. Chemie Ingenieur Technik 2020, 92, 31-39.[2] T. Reier, et al. ACS Catalysis 2012, 2, 1765-1772.[3] Y. Lee et al. The Journal of Physical Chemistry Letters 2012, 3, 399-404.[4] S. Geiger et al. Nature Catalysis 2018, 1, 508-515.[5] M.Malinovic et al. Advanced Energy Materials 2022, Manuscript submitted for publication.

Evaluation and Upscaling of Impregnated La0.20Sr0.25Ca0.45TiO3 Fuel Electrodes for Solid Oxide Electrolysis Cells Under H2O, CO2 and Co-Electrolysis Conditions

As a result of a successful collaboration between the University of St Andrews and HEXIS AG over the past >10 years, an alternative solid oxide fuel cell (SOFC) fuel electrode material (to the state-of-the-art Ni/CGO fuel electrode) has been intensively researched and developed 1 at a button cell scale (1 cm2 active area), 2 tested under harsh operating conditions and upscaled to short stack scale (5 cells each of 100 cm2 active area), 1,3 in addition to being integrated into full combined heat and power units (60 cells each of 100 cm2 active area) with nominal 1-1.5 kW power outputs. 3,4 This highly robust fuel electrode comprises a La0.20Sr0.25Ca0.45TiO3 (LSCTA-) ‘backbone’ with cerium gadolinium oxide (CGO) and Rh impregnates, offering stability toward redox/thermoredox/thermal cycling, overload or stress testing, degradation comparable to the state-of-the-art SOFCs and exposure to sulphurised natural gas. 1 This material, therefore, addresses many of the challenges presented by the Ni/CGO fuel electrodes.Given the success of this material as a SOFC fuel electrode and the growing demand for production of ‘green’ hydrogen and synthesis gas through high-temperature electrolysis, 5 it is also desirable to assess its performance in solid oxide electrolysis cells (SOECs). In this paper, the authors present a comprehensive study of the performance of SOECs containing the aforementioned titanate-based fuel electrodes.Firstly, testing of button cell scale SOECs (1 cm2 active area) in pure CO2 and H2O/H2 mixtures, carried out at the University of St Andrews and HEXIS AG, will be outlined, including promising initial test data from VI curves and AC impedance spectroscopic analysis. Subsequently, information on durability testing of the aforementioned SOECs will be provided. This data indicates that high degradation is observed during testing in H2O/H2/N2 mixtures when employing a LSM-YSZ/LSM air electrode, most likely due to delamination caused by oxygen evolution at the triple phase boundary between LSM and YSZ particles and at the air electrode-electrolyte interface, which is significantly minimised by replacement with a LSCF-CGO air electrode. Finally, upscaling of this technology to a 5 x 5 cm footprint SOEC (16 cm2 active area) containing the aforementioned fuel electrode, a stabilised zirconia electrolyte and a LSCF-CGO air electrode will be outlined. Encouraging results from a ~600 hour test at 850 °C will be presented, including operation in 54 % H2O:46 % CO2 and pure CO2 at 1.47 V, as well as in 51 % H2O:49 % N2 at 1.29 V (without the use of a reducing gas). References 1 R. Price, M. Cassidy, J. G. Grolig, G. Longo, U. Weissen, A. Mai and J. T. S. Irvine, Advanced Energy Materials, 2021, 11, 2003951.2 R. Price, M. Cassidy, J. G. Grolig, A. Mai and J. T. S. Irvine, J. Electrochem. Soc., 2019, 166, F343–F349.3 M. C. Verbraeken, B. Iwanschitz, E. Stefan, M. Cassidy, U. Weissen, A. Mai and J. T. S. Irvine, Fuel Cells, 2015, 5, 682–688.4 R. Price, H. Bausinger, G. Longo, U. Weissen, M. Cassidy, J. G. Grolig, A. Mai and J. T. S. Irvine, In Preparation, 2022.5 J. B. Hansen, Faraday Discuss., 2015, 182, 9 – 48.

Wear resistance of composite materials based on ultra-high molecular polyethylene with combined filling

Polymer composite materials (PCM) of antifriction duty with self-lubricating properties are used for the manufacture of various parts in friction units of machines and mechanisms. PCM can partially replace parts made of metals and alloys, increasing the reliability and service life of the equipment when the use of oils or external lubricants is limited or prohibited. The goal of the study is the effect of fillers (sulfenamide, sulfur, magnesium and zinc oxides) on the tribological parameters of polymer composite materials based on ultra-high molecular weight polyethylene (UHMWPE). Samples were prepared by hot pressing at a temperature of 175°C and a pressure of 10 MPa. Composites with filler concentrations 0.5 and 1 wt.% were considered (for sulfenamide, sulfenamide with sulfur, and combinations of 0.5 and 1 wt.% sulfenamide with sulfur and zinc oxide or magnesium oxide). It is shown that the introduction of sulfenamide leads to an increase in the wear resistance by six times, and the introduction of a combination of fillers of 0.5 wt.% sulfenamide, sulfur, and magnesium oxide — by 1.5 times. The friction surfaces of composites were studied using methods of scanning electron microscopy and IR-spectrometry. The formation of an oriented ordered structure in the form of clusters of wear products was revealed on the friction surfaces of composites filled with sulfenamide. In the case of combined filling, secondary structures were found on the friction surface, which visually differ from the UHMWPE friction surface. The appearance of peaks in IR spectra corresponding to oxygen-containing groups (–C=O, –COOX) was observed on the friction surface of composites with combined filling. It is shown that IR spectra of composites with mono- and binary fillers have peaks of less intensity due to the formation of secondary structures. The introduction of sulfenamide into UHMWPE, together with zinc and magnesium oxides, promotes the crosslinking of polymer macromolecules in the friction zone due to frictional heating, shear loads, and the action of a counterbody. The developed materials can be used as parts of friction units for cars and transport equipment that can withstand harsh operating conditions in a sharply continental climate.

A decision-making design approach to optimize the hole arrangement of effusion cooling plates under non-uniform heat load conditions

The harsh operating conditions of aero-engines contain non-uniform temperatures and variable hotspots, which require adaptive cooling techniques to accommodate the heat loads on the external surfaces of metal. Among the existing technologies, effusion cooling is an important way to fulfill such quests due to its flexibility in controlling coolant locally. As an effusively cooled component generally contains hundreds of holes, hole arrangement optimization is a high-dimensional problem that is difficult to solve using existing evolutionary algorithms. Recently matured deep reinforcement learning algorithms showed success in many research fields by incorporating data modeling with sequential optimization, which demonstrated the ability to convert high dimensional optimization problems into very low dimensional iterative optimization problems. The present study proposed a decision-making design approach to optimize the hole arrangement of a series of effusion cooling plates. Hole arrangements were transformed into Markov decision chains of opening or closing each hole. The decision chains were solved by a reinforcement learning framework integrated with a deep learning-based environment simulator. Results indicated that the proposed approach could yield an elevation of cooling performance by 20% as compared with the results from genetic algorithms. Moreover, an analytical correlation was extracted from the clear decision boundaries of reinforcement learning. Upon further validation, the computational cost to apply the correlation to other non-uniform heat loads was within seconds, while the cooling effect could reach the same optimization level as reinforcement learning. The idea proposed in this study could be applied to the arrangement optimization of multiple cooling technologies, such as film/effusion cooling, impingement cooling, and pin–fin array cooling.