Harsh Operating Conditions Research Articles

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.

Optimizing the Spatial Density of Single Co Sites via Molecular Spacing for Facilitating Sustainable Water Oxidation.

Advances in single-atom (-site) catalysts (SACs) provide a new solution of atomic economy and accuracy for designing efficient electrocatalysts. In addition to a precise local coordination environment, controllable spatial active structure and tolerance under harsh operating conditions remain great challenges in the development of SACs. Here, we show a series of molecule-spaced SACs (msSACs) using different acid anhydrides to regulate the spatial density of discrete metal phthalocyanines with single Co sites, which significantly improve the effective active-site numbers and mass transfer, enabling one of the msSACs connected by pyromellitic dianhydride to exhibit an outstanding mass activity of (1.63 ± 0.01) × 105 A·g-1 and TOFbulk of 27.66 ± 1.59 s-1 at 1.58 V (vs RHE) and long-term durability at an ultrahigh current density of 2.0 A·cm-2 under industrial conditions for oxygen evolution reaction. This study demonstrates that the accessible spatial density of single atom sites can be another important parameter to enhance the overall performance of catalysts.

Heat transfer enhancement of a microchannel cooler with V-shaped partitions

The ongoing evolution of electronic systems that operate under extreme conditions has led to persistent concern about potential failures caused by escalating temperature levels which provokes the decline the operating quality. In response to this challenge, cooling solutions based on microchannels have emerged as promising prospects for improving thermal management in such scenarios. This paper explores the importance of these innovative cooling techniques and their potential for mitigating the risks of overheating in electronic systems. Furthermore, the introduction of microfluidic techniques and microchannels, specifically constricted microchannels, offers promising approaches to improve cooling efficiency. These cooling systems enable efficient heat dissipation and thermal regulation, mitigating the risk of overheating and enhancing system performance. Constricted microchannels facilitate compact and efficient heat transfer by leveraging increased surface area-to-volume ratios and improved convective cooling. Nowadays, microchannel-based heat sinks, heat exchangers, and cooling systems have been developed, showcasing improved heat dissipation, reduced temperature gradients, and enhanced energy efficiency. This research focuses on a parametrical study that examines the fluid nature, Reynolds number analysis, and system design. Numerical results demonstrate successful thermal management of high-temperature electronic systems using constricted microchannel cooling. These results mitigate temperature-related failures and support the development of robust systems for harsh operating conditions.

A Review on MXene as Promising Support Materials for Oxygen Evolution Reaction Catalysts

AbstractThe harsh operating conditions of the oxygen evolution reaction (OER) in water electrolysis severely degrade the activity and stability of the electrocatalysts due to elemental leaching or particle agglomeration. Therefore, it is crucial to incorporate support materials that effectively immobilize catalyst particles for developing efficient OER catalysts. This review aims to highlight the role of MXene as a support material to improve the performance of OER catalysts. First, the extended OER mechanism is briefly described in terms of the effect of MXene support on OER catalysts. Then, various synthesis methods of MXene and catalyst‐MXene compounds are introduced, and important properties of MXene that are beneficial to improve OER performances are discussed. The electrocatalytic results of the enhanced OER catalysts due to the effective MXene support are also summarized. Finally, future challenges and prospects are proposed for utilizing MXene as an excellent support material for various electrocatalysis.

Stable oxygen permeable membrane with Ce0.9Gd0.1O2-δ protective layer for syngas production

The stability of catalytic membrane reactors (CMRs) is crucial for the practical applications in chemical reaction processes. However, currently reported CMRs with perovskite-based oxygen permeable membranes usually show poor stability owing to the over-reduction of Co and Fe ions in perovskite lattice under harsh reducing gas atmospheres and the interaction between membrane and catalyst. Here we developed an oxygen permeable membrane Ce0.9Gd0.1O2-δ-SrCe0.5Fe0.5O3-δ (CGO-SCF) with Ce0.9Gd0.1O2-δ (CGO) protective layer to construct a catalytic membrane reactor packed with Ni/Al2O3 catalyst for partial oxidation of methane. The CGO dense protective layer can effectively avoid the over-reduction of Fe ions in perovskite under harsh reducing gas atmospheres and the interaction between perovskite and Ni/Al2O3. Benefiting from high stability and mixed ionic-electronic conductivity of CGO in a low oxygen partial pressure environment, the developed membrane reactor with a dense CGO thin film was successfully operated with a stable CH4 conversion of 87% and a H2/CO ratio of 2 over 200 h in harsh operating conditions. This strategy proposed here provides insights into the design of highly stable catalytic membrane reactor in harsh conditions.

MXene/Ag@ZnO/WPU/Melamine gradient composite foams prepared by a unidirectional evaporation approach for absorption-dominated electromagnetic interference shielding

Gradient electromagnetic interference (EMI) shielding materials with absorption-dominated characteristics are promising but always have problems like complicated steps or harsh operation conditions. Herein, we propose a gradient EMI composite foam of MXene/Ag@ZnO/WPU/Melamine fabricated through a simple unidirectional evaporation in combination with a vacuum-drying method. Benefiting from it, the conductivity of the material decreases from the top and bottom to the middle. The top with good impedance matching, which allows electromagnetic waves to enter the material, and the bottom with an efficient conductive network, which ensures an excellent EMI SE of the composite foam, could be balanced owing to the difference in the dispersibility of MXene and Ag@ZnO. Under the effect of “absorb-reflect-reabsorb”, the as-prepared M2A3F composite material exhibits a high EMI SE of 39.90 dB and a low reflectivity coefficient of 0.1423 with an ultra-low volume ratio (2.72 % MXene and 4.25 % Ag). In addition, it features good mechanical properties, especially cyclic compression recovery. In sum, this study provides a novel solution for preparing high-performance EMI materials with absorption-dominated characteristics on a large scale.

Impact of ionizing radiation on iodine capture by functionalized mesoporous silica

The efficient capture of radioactive iodine is an important challenge for the nuclear industry, in order to prevent risks for the environment and for the health. The use of solid sorbent materials, able to capture significant amounts of iodine and to resist to harsh operating conditions, such as radiation, is then of paramount interest. Here, we have grafted a high surface area mesoporous silica, SBA-15, with the N-[3-(trimethoxysilyl)propyl]ethylenediamine “diamino” ligand. The resulting material is able to capture significant amounts of iodine (around 0.23 g per gram of material) due to a strong interaction between iodine and the lone pairs of the nitrogen atoms. We have also investigated the behavior of this grafted material towards ionizing radiation in order to assess its stability when placed in a radioactive environment. Upon irradiation, radiolysis of the ligand led to H2 production due to preferential cleavage of the N–H bonds, rather than cleavage of C–H bonds, hence forming imine functional groups as evidenced by infrared spectroscopy. After irradiation at the dose of 1 MGy, the thus-modified materials were still able to capture iodine, but in a lower proportion (around 0.11 g per gram of material). This was attributed to the loss of amine groups upon irradiation. Our work shows that these materials are potential candidates for the radioactive iodine capture, as they can be efficient up to doses of the order of 1 MGy.

Simulation study of crack parameters’ effects on the vibration characteristics of a bladed disk system

As a key component of the turbo machine rotor in harsh operating conditions, high cycle fatigue failure and even cracks are common in bladed disks. In this paper, modal analysis was carried out for a single cracked bladed disk system, the effects of crack depth, crack height and rotating speed on its vibration characteristics were studied by the method of both numerical simulation and orthogonal test, and the effects of crack distribution on the vibration characteristics of multi-crack bladed disk systems were also studied. Finally, some conclusions have been drawn, they provide a fundamental understanding of blade health monitoring and fault prediction, and are important to improve the reliability and safety of turbine operation.