High Elevated Temperature Research Articles

Determination and verification of parameters in the dynamic constitutive for Inconel 718 superalloy

Abstract Inconel 718, which is a nickel-based superalloy material used in aero engines, may be subjected to intense dynamic loading in an accidental engine failure. However, the material models for Inconel 718 employed in existing studies can not describe the mechanical behaviors under complex stress states, high strain rates and elevated temperatures satisfactorily. In this paper, various parameters of a previously proposed dynamic constitutive model for Inconel 718 are determined and verified. First, the parameters of strength, strain rate effect, temperature effect and failure for precipitation hardened Inconel 718 are calibrated against various material tests. Then, the parameters are verified by comparing the numerical results obtained from the dynamic constitutive model with the corresponding ballistic test data. It transpires that the numerical results agree well with the test data, which demonstrates the accuracy and effectiveness of the dynamic constitutive model for Inconel 718. It can also be concluded that the consideration of Lode angle effect and precise descriptions of strain rate and temperature effects are significant for the reproduction of mechanical responses of Inconel 718 plates under intense dynamic loadings in numerical simulations.

Scalable and Efficient H2S Treated Nickel Foam Electrocatalyst for Alkaline Water Electrolysis Under Industrial Conditions

With the foreseen orders of magnitude increase of green hydrogen production from electrolysis in the coming decade [1], electrolyzer stacks must be produced in a scalable and efficiently manner based on abundant materials, while still maintaining high energy efficiency. This study explores a novel synthesis route utilizing reactive Chemical Vapor Deposition (CVD) of hydrogen sulfide (H2S) gas to enhance the catalytic activity of nickel foam for alkaline water electrolysis. The synthesis involves sulfiding the nickel foam at temperatures ranging from 100 °C to 140 °C in an H2S atmosphere for durations of 1 to 17 hours. The resulting electrodes exhibit a uniform film with distinctive nanostructural modification [2].Electrochemical performance evaluations were conducted under industrial conditions, in 30 wt% KOH electrolytes at 85 °C with current densities ranging from 200 to 500 mA/cm2 for up to two weeks. Testing under high current densities and elevated temperatures is essential to meet industrial requirements [3]. The tests were made in an immersed single cell setup with 4 cm2 electrodes on both sides [4]. Remarkably, the H2S-CVD modified electrodes demonstrate a cell potential reduction of 0.4 V@200 mA/cm2, corresponding to an 18% increase in the overall efficiency for water splitting compared to pristine nickel foam. Electrochemical analysis reveals a substantial 30-fold higher surface area following the H2S-CVD treatment. [2].Structural and compositional analyses of the modified nickel foam electrodes were conducted using various techniques including X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Energy Dispersive X-Rays (EDX) analysis, and synchrotron powder X-ray diffraction (XRD) both before and after running alkaline electrolysis. These analyses reveal the presence of Ni3S2 with a film thickness ranging from 1 to 4 μm post-H2S treatment. Characterization of the synchrotron data XRD shows 14 wt% Ni3S2 for the H2S-CVD treated samples. Furthermore, prolonged reaction times reveal the continuous reaction and emergence of NiS, elucidating the evolution of surface morphology under sulfidation conditions [2].Post-electrolysis characterizations indicate either the absence or minimal presence of sulfur on the modified electrodes, suggesting that the enhanced performance is likely attributed to alterations in the surface morphology rather than sulfur-assisted increase in the catalytic activity. This study provides insights into the surface-sensitive characterization, synthesis conditions, activity assessments, and degradation analyses, showing the potential of H2S-mediated surface modification as electrocatalytic material in alkaline water electrolysis systems. Bibliography [1] International Energy Agency. Global Hydrogen Review 2021. www.iea.org/report s/global-hydrogen-review-2021.[2] Olesen, S. E. et al. Scalable and Efficient H2S Treatment of Nickel Foam Electrocatalyst for Alkaline Water Electrolysis under Industrial Conditions. 2024. In preparation.[3] Ehlers, J. C.; Feidenhans’l, A. A.; Therkildsen, K. T.; Larrazábal, G. O. Affordable Green Hydrogen from Alkaline Water Electrolysis: Key Research Needs from an Industrial Perspective. ACS Energy Letters. American Chemical Society March 10, 2023, pp 1502–1509. doi.org/10.1021/acsenergylett.2c02897.[4] Frederiksen, M. L.; Kragh-Schwarz, M. V.; Bentien, A.; Nielsen, L. P. Improved Performance of Electrodes for Alkaline Electrolysis. Transactions of the Institute of Metal Finishing. 2023. 10.1080/00202967.2023.2196850. Figure 1

Electrochemical Adsorption-Desorption Mechanism on Composite Electrode Materials for CO2 Direct Air Capturing

Use of carbon-based fossil fuels, greenhouse gases are emitted to the atmosphere causing fatal environmental issues like global warming. To overcome this problem, Sustainable Development Goals (SDGs) is now a fundamental issue for worldwide nations. Among them, carbon neutrality stands as a central pillar since CO2 has the biggest portion of emitted green-house gases. Emitted CO2 from industrial facilities like factories and incinerators is collected by various carbon capturing technology which is developed due to the pursuit of carbon neutrality necessities. Among them, Direct Air Capture (DAC) is gaining interests due to its superior efficiency compared to other alternatives such as filters and absorbents for the challenges like high pressure and elevated temperatures at the CO2 capturing process. Furthermore, the durability of filtration materials and waste problems poses a significant concern to the environment. To overcome these limitations, electrochemical adsorption system is looking forward to becoming the next generation carbon capture technology. By applying varying electrical energies, this allows adsorption and desorption of CO2 within an adsorber layer. By this mechanism, we can significantly reduce the filtration waste of capturing process. The adsorber layer is consisted with catalysts, which has large surface area and active sites that can adsorb and desorb CO2 stably with electricity. Detailed physicochemical and electrochemical characterizations of the reactive and adsorbent materials were conducted with chemically designed evaluation system to measure the CO2 capturing efficiency.

Poly(fluorene)-Based Anion Exchange Membranes with an Interstitial Alkyl Chain in Polymer Backbone and Conducting Groups for Water Electrolysis

The demand to reduce fossil fuel dependence has received unprecedented attention due to the generation of greenhouse gases and increase in energy consumption. Hydrogen is considered an ideal energy carrier for building a global renewable energy system owing to its numerous benefits, such as high energy efficiency and nontoxicity. However, more than 95% of hydrogen is produced by reformation of natural gas, which is a nonrenewable energy source with high carbon emissions that predominantly consists of methane. To realize hydrogen as a true alternative to fossil fuels, it must be produced in an environmentally friendly and sustainable manner, which is also known as green hydrogen. One approach to generating green hydrogen is by water electrolysis to split water, which is an essentially unlimited resource.Current approaches to water electrolysis currently use proton exchange membranes, but anion exchange membranes (AEMs) operate under alkaline conditions and thus allow the use of platinum group metal (PGM)-free metals as electrocatalysts, which makes them a more cost-effective alternative. However, AEM water electrolysis (AEMWE) is limited by unsatisfactory cell durability and performance due to the poor physicochemical stability under alkaline conditions and low hydroxide conductivity of the AEM. Therefore, AEMs need to be improved in terms of their mechanical properties, dimensional stability, and alkaline stability to ensure cell durability and in terms of their hydroxide conductivity to ensure cell performance.For AEMs, an important step in improving the efficiency and durability of the cell is to enhance the ion conductivity and chemical stability of these materials, which are vulnerable to hydroxide. The stable operation of AEMWE under high alkaline conditions and elevated temperatures is necessary; hence, the spacer-type cation groups anchored from the backbone and aryl ether-free based polymers are a promising candidate for tolerating harsh alkaline conditions.Thus, we newly designed various type of aryl ether-free poly(fluorene)-based AEMs with interstitial alkyl chains in the conducting groups and a polymer backbone for water electrolysis. The rationally designed AEMs not only demonstrated excellent mechanical properties, high alkaline stability and satisfactory hydroxide conductivity, making them excellent cell performance and durability of the AEMWE. The resulting single AEMWE cell using synthesized AEM demonstrates a voltage decay rate of 2 mV kh− 1 at 1.0 A cm− 2, significantly lower than those reported for AEMWEs and Nafion-based PEMWEs. Additionally, a large-sized 1-cell AEMWE stack utilizing PFPBPF-4-QA with an active area of 63.6 cm2 acheived an energy conversion efficiency of 80.2% and a voltage decay rate of 1.5 mV kh−1 for 2,000 h,with over 90% of the initial efficiency maintained for over 49,095 h through exponential fitting calculation.

Densities and Apparent Molar Volumes of Aqueous Solutions of Nitric Acid to High Concentrations and Elevated Temperatures

Densities and Apparent Molar Volumes of Aqueous Solutions of Nitric Acid to High Concentrations and Elevated Temperatures

Explainable deep learning on multi-target time series forecasting: An air pollution use case

Urban air pollution represents a significant threat to public health and the environment, with nitrogen oxides, ozone, and particulate matter being among the most harmful pollutants. These contribute to respiratory and cardiovascular diseases, particularly in urban areas with high traffic and elevated temperatures. Machine learning, especially deep learning, shows promise in enhancing the prediction accuracy of prediction of pollutant's concentrations. However, the “black box” nature of these models often limits their interpretability, which is crucial for informed decision-making. Our study introduces a Temporal Selection Layer technique within deep learning models for time series forecasting to tackle this issue. This technique not only improves prediction accuracy by embedding feature selection directly into the neural network, but also enhances interpretability and reduces computational costs. In particular, we applied this method to hourly concentration data of pollutants, including particulate matter, ozone, and nitrogen oxides, from five urban monitoring sites in Graz, Austria. These concentrations were used as target variables to predict, while identifying the most relevant features and periods that affect prediction accuracy. Comparative analysis with other embedded feature selection methods showed that the Temporal Selection Layer significantly enhances both model effectiveness and transparency. Additionally, we applied explainable techniques to evaluate the impact of weather and time-related factors on air pollution, which also helped assess feature importance. The results show that our approach improves both prediction accuracy and model interpretability, leading finally to more effective pollution management strategies.

Optimization of titanium alloy bipolar plate performance in proton exchange membrane water electrolysis with Cr/W/diamond-like carbon coating

The operating environment for bipolar plates in proton exchange membrane water electrolysis (PEMWE) systems is highly challenging, characterized by high electrical potential, acidic pH, and elevated temperatures. Bipolar plates must possess high corrosion resistance and electrical conductivity to ensure stable and efficient system perfomance. Therefore, surface coatings are essential to decelerate oxidation on the substrate surface, preventing a significant increase in interfacial contact resistance (ICR). This investigation applied a Cr/W/diamond-like carbon (DLC) coating to titanium alloy (Ti-6Al-4 V, also known as TC4) surfaces using magnetron sputtering. The multilayer coating system was designed to enhance electrical conductivity and corrosion resistance of the bipolar plate while ensuring good coating adhesion. At potentials of 1.2 V, 1.5 V, and 1.8 V, the current densities measured during potentiostatic polarization were 0.11 μA·cm-2, 0.19 μA·cm-2, and 0.4 μA·cm-2, respectively, showing a significant reduction compared to the TC4 matrix and demonstrating long-term stability. The Cr/W/DLC-coated TC4 bipolar plates exhibited an ICR of 16.98 mΩ/cm2 under a contact pressure of 1.4 MPa. These results suggest that the coating provides exceptional corrosion resistance under PEMWE operating conditions while retaining electrical conductivity.

Indoor Air Quality in Laboratories and Its Relationship with Psychological Performance Among University Students in Malaysia

Introduction: Poor indoor air quality (IAQ) in work environments can reduce productivity and decrease overall performance. This study examines IAQ in university laboratories and its relationship with psychological performance among students in Malaysia. Methods: This cross-sectional study was conducted from October to November 2023 in six laboratories at a Malaysian university, categorised into chemical and non-chemical. A total of 117 students aged 18 to 40 participated. IAQ was measured in real-time for 8 hours during weekdays using instruments for particulate matter (PM2.5, PM10), carbon monoxide (CO), total volatile organic compounds (TVOC), airborne microorganisms, carbon dioxide (CO2), temperature in °C, relative humidity (RH), and air movement. Psychological performance was assessed using the General Health Questionnaire (GHQ-12) and Post Occupancy Evaluation (POE). Data analysis was performed using Kruskal-Wallis, One-Way ANOVA, and Chi-Square tests. Results and Discussion: Significant differences in IAQ parameters were observed for PM2.5 (p=0.007), PM10 (p=0.020), CO2 (p=0.024) and RH (p=0.043). Psychological distress affected 41.9% of students based on the predefined threshold. High CO levels (≥0.67 ppm) and elevated temperatures (≥23.28°C) were significantly associated with increased psychological distress (p=0.011). Students exposed to these conditions were 1.3 times more likely to experience distress (OR=1.3). Conclusion: Specific IAQ parameters, particularly CO and temperature, critically impact students’ psychological well-being. Improving IAQ by reducing CO levels and maintaining optimal temperatures may enhance mental health and performance. Improving IAQ by reducing CO levels and maintaining optimal temperatures may enhance mental health and performance. However, external factors such as personal stressors could not be entirely controlled.

Scalable all polymer dielectrics with self-assembled nanoscale multiboundary exhibiting superior high temperature capacitive performance

Polymers are key dielectric materials for energy storage capacitors in advanced electronics and electric power systems due to their high breakdown strengths, low loss, great reliability, lightweight, and low cost. However, their electric and dielectric performance deteriorates at elevated temperatures, making them unable to meet the rising demand for harsh-environment electronics such as electric vehicles, renewable energy, and electrified transportation. Here, we present an all-polymer nanostructured dielectric material that achieves a discharged energy density of 7.1 J/cm³ with a charge-discharge efficiency of 90% at 150°C, outperforming the existing dielectric polymers and representing more than a twofold improvement in discharged energy density compared with polyetherimide. The self-assembled nano-scale multiboundaries effectively impede the charge injection and excitation, leading to more than one order of magnitude lower leakage current density than the pristine polymer matrix PEI at high electric fields and elevated temperature. In addition, the film processing is simple, straightforward, and low cost, thus this all-polymer nanostructured dielectric material strategy is suitable for the mass production of dielectric polymer films for high-temperature capacitive energy storage.

Physical, Mechanical and Durability Properties of Eco-Friendly Engineered Geopolymer Composites

Engineered geopolymer composite (EGC) is a high-performance material with enhanced mechanical and durability capabilities. Ground granulated blast furnace slag (GGBFS) and silica fume (SF) are common binder materials in producing EGC. However, due to the scarcity and high cost of these materials in some countries, sustainable alternatives are needed. This research focused on producing eco-friendly EGC made of cheaper and more common pozzolanic waste materials that are rich in aluminum and silicon. Rice husk ash (RHA), granite waste powder (GWP), and volcanic pumice powder (VPP) were used as partial substitutions (10–50%) of GGBFS in EGC. The effects of these wastes on workability, unit weight, compressive strength, tensile strength, flexural strength, water absorption, and porosity of EGC were examined. The residual compressive strength of the proposed EGC mixtures at high elevated temperatures (200, 400, and 600 °C) was also evaluated. Additionally, scanning electron microscope (SEM) was employed to analyze the EGC microstructure characteristics. The experimental results demonstrated that replacing GGBFS with RHA and GWP at high replacement ratios decreased EGC workability by up to 23.1% and 30.8%, respectively, while 50% VPP improved EGC workability by up to 38.5%. EGC mixtures made with 30% RHA, 20% GWP, or 10% VPP showed the optimal results in which they exhibited the highest compressive, tensile, and flexural strengths, as well as the highest residual compressive strength when exposed to high elevated temperatures. The water absorption and porosity increased by up to 106.1% and 75.1%, respectively, when using RHA; increased by up to 23.2% and 18.6%, respectively, when using GWP; and decreased by up to 24.7% and 22.6%, respectively, when using VPP in EGC.

A comparative experimental study on abrasive flow machining vs flow peening GOV processes on Inconel 718

Inconel 718, a nickel-based super alloy, has a broad applications area from aerospace, medical and defence to traditional industries because of its high durability, corrosion resistance and elevated temperature performance. Unconventional surface treatment methods of abrasive flow machining (AFM) and shot peening (SP) are applied to improve the mechanical performance of Inconel 718. In this work, a new surface treatment process known as flow peening (GOV) already developed by combining the advantages of abrasive flow machining (AFM) and shot peening methods such as surface finishing and residual compressive stress generation respectively was applied experimentally for Inconel 718. The effects of process parameters for GOV and AFM processes on the surface quality of the specimens were experimentally investigated. White layer decrease, surface roughness decrease and material removal amount were discussed for both processes. The best surface quality with 0.56 μm Ra surface roughness value and material removal amount of 7.2 mg were obtained by GOV process while similar level of surface roughness value of 0.52 μm was obtained by removing 6648.03 mg material for AFM. When the AFM process was continued, the best values of 0.24 μm Ra was obtained removing excess material of 17,385.60 mg compared to the GOV process. Also, all these results were supported by SEM images.

Unlocking nature’s brilliance: using Antarctic extremophile Shewanella baltica to biosynthesize lanthanide-containing nanoparticles with optical up-conversion

Both lanthanide-containing and fluorine-containing nanomaterials present challenging targets for microbial biosynthesis because these elements are toxic to most bacteria. Here, we overcome these challenges by using an Antarctic Shewanella baltica strain that tolerates these elements and report the first biosynthesis of lanthanide-doped fluoride nanoparticles (NPs) from them. NaYF4 NPs doped with Er3+/Yb3+ are prototypical lanthanide-based upconverting nanoparticles (UCNPs) with upconverted luminescence at visible wavelengths under infrared excitation. However, their synthesis employs high precursor concentrations, organic solvents, and elevated temperatures. Microbial biosynthesis offers a greener alternative but has not been explored for these materials. Here, we harness an extremophile S. baltica strain to biosynthesize UCNPs at room temperature, based upon its high tolerance for fluoride and lanthanide ions and the observation that tolerance of lanthanides increased in the presence of fluoride. Our biosynthesis produces electron-dense nanostructures composed of Na, Y, F, Yb, and Er in the bacterial periplasm, adhered to the outer cell membrane, and dispersed extracellularly, which exhibited up-converted emission under 980 nm excitation. This suggests that extracellular or periplasmic mineralization of lanthanides as fluorides protects the bacteria from lanthanide toxicity. Subsequent heating both enhanced upconverted emission from UCNPs and allowed observation of their crystallinity in transmission electron microscopy (TEM). This work establishes the first biosynthesis of NaYF4:Yb: Er UCNPs, advancing both nanotechnology and biotechnology.Graphical

Unraveling the complex interactions between ozone pollution and agricultural productivity in China's main winter wheat region using an interpretable machine learning framework

Surface ozone has become a significant atmospheric pollutant in China, exerting a profound impact on crop production and posing a serious threat to food security. Previous studies have extensively explored the physiological mechanisms of ozone damage to plants. However, the effects of ozone interactions with other environmental factors, such as climate change, on agricultural productivity at the regional scale, particularly under natural conditions, remain insufficiently understood. In this study, we employed an interpretable machine learning framework, specifically the eXtreme Gradient Boosting (XGBoost) algorithm enhanced by SHapley Additive exPlanations (SHAP), to investigate the influence of ozone and its interactions with environmental factors on crop production in China's primary winter wheat region. Additionally, a structural equation model was developed to elucidate the mechanisms driving these interactions. Our findings demonstrate that ozone pollution exerts a significant negative effect on winter wheat productivity (r = −0.47, P < 0.001), with productivity losses escalating from −12.28 % to −22.09 % as ozone levels increase. Notably, the impact of ozone is spatially heterogeneous, with western Shandong province identified as a hotspot for ozone-induced damage. Furthermore, our results confirm the complexity of the relationship between ozone pollution and agricultural productivity, which is influenced by multiple interacting environmental factors. Specifically, we found that severe ozone pollution, when combined with high aerosol concentrations or elevated temperatures, significantly exacerbates crop productivity losses, although drought conditions can partially mitigate these adverse effects. Our study highlights the importance of incorporating the interactive effects of air pollution and climate change into future crop models. The comprehensive framework developed in this study, which integrates statistical modeling with explainable machine learning, provides a valuable methodological reference for quantitatively assessing the impact of air pollution on crop productivity at a regional scale.

Tailor-made ammonia nitrogen risk management with machine learning models for aquatic environments in the Mainland of China

Efficient management of pollutant risks in water bodies is crucial for public health and aquatic ecosystem sustainability. However, the toxicities of pollutants, such as ammonia nitrogen (NH3-N), are often affected by multiple water quality factors, including the pH and water temperature. Extensive spatial and temporal variability in these factors hinders tailor-made management of risk. This study used high-frequency monitoring data collected over 1 year to evaluate the long-term NH3-N risk in China’s aquatic ecosystems. High accuracy and interpretability were achieved by decomposing NH3-N risk into the contributions of key influencing factors using random forest models and Shapley Additive Explanations. Two distinct types of NH3-N risk hotspots were identified across 18 cities: 15 cities with high NH3-N concentrations and 3 cities with low environmental carrying capacity due to high pH levels or elevated water temperatures. For the former, rapid NH3-N abatement measures are necessary to bring NH3-N concentrations back below the environmental capacity. For the latter, it is recommended that NH3-N related industries are relocated to regions with high environmental capacities because fragile environments are not suitable for such industries. Importantly, this study investigated methods for attributing pollutant risks in the context of non-linear influencing factors, and the risk of NH3-N was predicted to increase by 6.1 % by the end of 2100 in the context of increasing temperatures under the SSP 2–4.5 scenario. The methodology is also adaptable and suitable for integration into global ecosystem risk management efforts to balance development and aquatic ecological sustainability.

Behavioural Thermoregulation of Flowers via Petal Movement.

Widely documented in animals, behavioural thermoregulation mitigates negative impacts of climate change. Plants experience especially strong thermal variability but evidence for plant behavioural thermoregulation is limited. Along a montane elevation gradient, Argentina anserina flowers warm more in alpine populations than at lower elevation. We linked floral temperature with phenotypes to identify warming mechanisms and documented petal movement and pollinator visitation using time-lapse cameras. High elevation flowers were more cupped, focused light deeper within flowers and were more responsive to air temperature than low; cupping when cold and flattening when warm. At high elevation, a 20° increase in petal angle resulted in a 0.46°C increase in warming. Warming increased pollinator visitation, especially under cooler high elevation temperatures. A plasticity study revealed constitutive elevational differences in petal cupping and stronger temperature-induced floral plasticity in high elevation populations. Thus, plant populations have evolved different behavioural responses to temperature driving differences in thermoregulatory capacity.

From drops to drums: Assessing rainwater storage’s quality and quantity for addressing water demands in dry periods – A case study from Arusha Tanzania

Sustainable Development Goal 6 highlight the importance of providing reliable, affordable, and safe source of clean drinking water and sanitation for all by 2030. In Tanzania there is a dire need of a water supply strategy due to high levels of natural fluoride contamination in ground water (upto 74 mg/L) and the challenge of meeting water demand during 5 months long dry period. This study assesses social and technical feasibility of implementing rainwater harvesting (RWH) along with treatment technologies that includes Denutritor® to remove ammonia/pesticides and ultrafiltration to eliminate carbon. This integrated technology known as “Mbinguni Maji” is aimed for the long-term water storage to supply drinking water throughout the dry season. The methodology involves i) Assessing the technical feasibility of RWH using database from QGIS and Water Productivity Open-access portal (WaPOR) from the Food and Agricultural Organization of the United Nations; ii) conducting pilot demonstration in 5 different locations in Tanzania; and iii) conducting socio-economic survey for social acceptance of the technology through detailed questionnaires administered to residential homes, medical facilities, schools, hotels, and water kiosk owner. The result indicates that, from technical perspective, there is ample rainfall (average of 1036 mm/year) to supply water throughout the dry season, primarily for drinking and cooking purpose only (upto a maximum of 10 lpcd). The pilot demonstration confirms that the Mbinguni Maji RWH technology produce water that meets WHO water quality standards. The produced water is free from nutrients like carbon and ammonia, ensuring the possibility of long-term storage without bacterial and algal growth. Furthermore, Lab scale demonstration of Denutritor® show promising result of removing nitrite, ammonia even at high elevated temperature (30 °C), which can be effectively applied in Tanzania. In terms of social acceptance, RWH technology is already widely practised in Tanzania during the rainy season. However, the initial investment costs and operation & maintenance (O&M) concerns hinder the usage of RWH technology. Therefore, to ensure the long-term sustainability of RWH technologies, there is a need of development of comprehensive business plan and community awareness campaign.

Bio-Inspired Photosynthesis Platform for Enhanced NADH Conversion and L-Glutamate Synthesis.

Inspired by the layered structure, light absorption, and charge carrier pathway of chloroplast thylakoids in natural photosynthesis, we propose a novel artificial photosynthesis platform, which is composed of layered structured vaterite as the scaffold with gold nanoparticles (AuNPs), photosensitizer eosin Y (EY), and redox enzyme L-glutamate dehydrogenase (GDH) as the functional components. The EY exhibited significantly enhanced light absorption and charge carrier generation due to the localized surface plasmon resonance (LSPR) around the AuNPs and light refraction within the layers. This artificial photosynthesis platform can regenerate reduced nicotinamide adenine dinucleotide (NADH) under visible light and promote the rapid conversion of α-ketoglutarate to L-glutamate (0.453 Mm/h). The excellent biocompatibility of layered vaterite significantly enhances the resistance of GDH to harsh conditions, including high pH (pH = 10) and elevated temperatures (37-57 °C).

Thermally stable high-loading single Cu sites on ZSM-5 for selective catalytic oxidation of NH3

Rigorous comparisons between single site- and nanoparticle (NP)-dispersed catalysts featuring the same composition, in terms of activity, selectivity, and reaction mechanism, are limited. This limitation is partly due to the tendency of single metal atoms to sinter into aggregated NPs at high loadings and elevated temperatures, driven by a decrease in metal surface free energy. Here, we have developed a unique two-step method for the synthesis of single Cu sites on ZSM-5 (termed CuS/ZSM-5) with high thermal stability. The atomic-level dispersion of single Cu sites was confirmed through scanning transmission electron microscopy, X-ray absorption fine structure (XAFS), and electron paramagnetic resonance spectroscopy. The CuS/ZSM-5 catalyst was compared to a CuO NP-based catalyst (termed CuN/ZSM-5) in the oxidation of NH3 to N2, with the former exhibiting superior activity and selectivity. Furthermore, operando XAFS and diffuse reflectance infrared Fourier transform spectroscopy studies were conducted to simultaneously assess the fate of the Cu and the surface adsorbates, providing a comprehensive understanding of the mechanism of the two catalysts. The study shows that the facile redox behavior exhibited by single Cu sites correlates with the enhanced activity observed for the CuS/ZSM-5 catalyst.

Fabrication and Tribological Performance of Self-Lubricating Porous Materials and Composites: A Review.

Porous materials have recently attracted significant attention in the aerospace and biomedical fields for addressing issues related to friction and wear. Porous materials are beneficial in applications where continuous lubrication is not feasible or for components that operate under extreme conditions, such as high speeds, elevated temperatures, and heavy loads. The pores can serve as reservoirs for liquid lubricants, which are gradually released during the operation of the components. The tribological properties of these materials depend on their porosity, the lubricants used, and any additional additives incorporated into the porous materials. This review article provides insight into common fabrication techniques for porous materials and examines their tribological performance for all three classes of materials-polymers, metals, and ceramics. Additionally, it discusses design criteria for porous self-lubricating materials by highlighting the critical properties of both the substrate and lubricants.

Combustion of ammonium perchlorate fo near adiabatic condition at high pressures and elevated Initial temperature

AbstractThis paper addresses the combustion of ammonium perchlorate (AP) near adiabatic conditions at high pressures and higher initial temperatures. The AP pellets were coated with a thin layer of silica grease to simulate the near adiabatic condition. The experiments were performed at initial temperatures of 30 and 70 °C in the pressure range of 2.5–30 MPa for coated and bare pellets. The bare pellets were found to exhibit mesa burning as reported in the literature. However, the coated pellets did not exhibit mesa burning. The burn rates of coated AP pellets increased linearly for the entire pressure range of 2.5–30 MPa with 0.64 pressure index. Further, the experiments were carried out for the first time at an initial temperature of 90 °C for 14–30 MPa pressure range, wherein, AP combustion did not display any characteristics of mesa burning (pressure index of 0.33). The surface morphology of quenched samples of both bare and coated pellets of AP were studied, by quenching (rapid depressurization technique) pellets at 6, 12, and 18 MPa pressures. The surface structure of quenched samples for near adiabatic conditions was similar for all three pressures. However, for bare pellets the changes in surface structure were observed with change in pressure, similar to the literature. Mesa burning was found to be an effect of convective heat loss from the periphery of the pellets and it was not observed when heat loss was reduced or initial temperature was higher than the critical initial temperature.