Elevated Temperatures Research Articles

Effects of Quasi-Static Strain Rate and Temperature on the Microstructural Features of Post-Processed Microstructures of Laser Powder Bed Fusion Ti6Al4V Alloy

This study documents an investigation of the flow stress properties and microstructural features of Ti6Al4V (ELI) alloy produced using laser powder bed fusion (LPBF). Selected heat treatment strategies were applied to the material to obtain different microstructures. The influence of quasi-static strain rates and temperature on the obtained microstructures of this material and their strain hardening properties are documented in this study. All microstructures of the alloy formed in this study were found to be sensitive to quasi-static strain rates and temperatures, where their flow stresses increased with increasing strain rate and decreased for tests conducted at elevated temperatures. The strain hardening rates of the fine microstructures were found to be high compared to those of coarse microstructures. The strain hardening rates for the various forms of LPBF Ti6Al4V (ELI) examined here were found to diminish with increasing test temperature. Though the deformed surfaces of the built samples were largely dominated by adiabatic shear bands (ASBs), the absence of ASBs was noted for all samples tested at a temperature of 500 °C and an imposed strain of 30%.

Temperature Impact on Lithium Metal Morphology in Lithium Reservoir-Free Solid-State Batteries

Lithium reservoir-free solid-state batteries can offer exceedingly high energy densities for a range of emerging applications related to aviation and electric vehicles. However, reversible operation of reservoir-free cells is plagued by a range of degradation mechanisms. The morphology of lithium metal film and subsequent evolution during operation can be highly variable and is dependent on the type of solid electrolyte, current collector, and operating conditions (current density, temperature, pressure, etc.). Here we evaluate lithium metal vertical and horizontal growth mechanisms at an argyrodite solid electrolyte–stainless steel interface at various temperatures from 25 to 80∘C. Combining confocal imaging and mesoscale modeling, we demonstrate how lithium metal island agglomeration is accelerated at elevated temperatures and facilitates greater horizontal growth of lithium metal. Maintaining high active material contact (e.g., horizontal growth) is critical for the formation of reversible lithium metal anodes in reservoir-free cells. Published by the American Physical Society 2024

Impacts of elevated temperature and vapour pressure deficit on leaf gas exchange and plant growth across six tropical rainforest tree species.

Elevated air temperature (Tair) and vapour pressure deficit (VPDair) significantly influence plant functioning, yet their relative impacts are difficult to disentangle. We examined the effects of elevated Tair (+6°C) and VPDair (+0.7 kPa) on the growth and physiology of six tropical tree species. Saplings were grown under well-watered conditions in climate-controlled glasshouses for 6 months under three treatments: (1) low Tair and low VPDair, (2) high Tair and low VPDair, and (3) high Tair and high VPDair. To assess acclimation, physiological parameters were measured at a set temperature. Warm-grown plants grown under elevated VPDair had significantly reduced stomatal conductance and increased instantaneous water use efficiency compared to plants grown under low VPDair. Photosynthetic biochemistry and thermal tolerance (Tcrit) were unaffected by VPDair, but elevated Tair caused Jmax25 to decrease and Tcrit to increase. Sapling biomass accumulation for all species responded positively to an increase in Tair, but elevated VPDair limited growth. This study shows that stomatal limitation caused by even moderate increases in VPDair can decrease productivity and growth rates in tropical species independently from Tair and has important implications for modelling the impacts of climate change on tropical forests.

Corrosion resistance and microstructural evolution of Yb-Al-Si-O glass-ceramics under molten Ca-Mg-Al-Si environment at 1350 °C

The intrinsic characteristics of Yb2O3-Al2O3-SiO2 (YbAS) glass-ceramics and their resistance to corrosion by molten calcium magnesium aluminosilicate (CMAS) at 1350 °C were systematically investigated. YbAS glass-ceramics, characterized by diverse compositions, maintaining phase stability over extended durations at elevated temperatures. After CMAS corrosion for 50 h, the main reaction phases were CaAl2Si2O8 and Ca2Yb8(SiO4)6O2, accompanied by multiple ion solid solution garnet in certain components. The glass component positioned along the eutectic line of Yb2Si2O7 and mullite, with an OB value marginally exceeding that of CMAS, exhibits superior corrosion resistance to CMAS. This finding offers valuable insights for the subsequent design of environmental barrier coatings (EBCs).

Novel Hybrid Ferromagnetic Fe–Co/Nanodiamond Nanostructures: Influence of Carbon on Their Structural and Magnetic Properties

Novel Hybrid Ferromagnetic Fe–Co/Nanodiamond Nanostructures: Influence of Carbon on Their Structural and Magnetic Properties

Selectivity Study of Anodic Seawater Electrolysis Catalysts Using the Rotating Ring-Disc Electrode Method

Seawater Electrolysis is an exciting alternative to freshwater electrolysis; however, it suffers from a multitude of issues that must be resolved before the technology can be scaled. Corrosive hypochlorite forms at the anode of seawater electrolysis and can damage catalysts and electrolyzer components. Hypochlorite is unstable and can decay, particularly when exposed to heat and metal ions, which can lead to erroneously high oxygen evolution reaction (OER) selectivity conclusions, resulting in poor catalyst and electrolyzer component selection. In this study, we use the rotating ring-disc electrode technique to characterize the selectivity of IrO2, NiO, Co3O4, RuO2, Pt and PtRu electrocatalysts in situ at near-neutral pH (8.4) with linear scan voltammetry (LSV), potentiostatic and galvanostatic experiments. Our findings reveal that elevated temperatures are conducive to higher OER selectivity. Furthermore, when we increased the chloride concentration in the electrolyte with an IrO2 catalyst, we observed that although the overall selectivity towards the OER reaction decreased, the OER current independently increased, indicating a synergistic relationship.

A novel NbTaV0.5Hf0.1 complex concentrated alloy with superior room-temperature tensile plasticity and elevated-temperature strength

Refractory complex concentrated alloys (RCCAs) encounter difficulties in balancing room-temperature ductility and high-temperature strength, which restricts their applications. Here, a novel NbTaV0.5Hf0.1 RCCA was prepared through vacuum arc melting for the first time. The as-cast alloy exhibited a stable body-centered cubic phase structure with a small amount of micro-scale dispersed Hf-rich oxides. As a result, the designed alloy exhibits a room-temperature tensile fracture strain of 14.9 %, and superior compressive yield strength values under elevated temperatures (472 MPa under 1200 ℃, 358 MPa under 1400 ℃, respectively). A synergy between room-temperature tensile ductility and exceptional high-temperature strength was achieved in RCCAs.

Sub-terahertz optomechanics

We demonstrate optomechanics in the sub-terahertz regime. An optical racetrack resonator, patterned from thin-film lithium niobate, is suspended to support mechanical structures oscillating at these extremely high frequencies, which are read out through cavity optomechanical coupling. Our hybrid platform paves the way for advancing mechanical systems in the quantum regime at elevated temperatures.

3D printed compliance tool incorporated internal-impeller structure for high performance face grinding of titanium alloy

During compliant face grinding of difficult-to-machine areas like the blade runner surface, significant heat accumulation at the tight interface between the workpiece and tool. This leads to limitations in surface integrity and tool life longevity. This study introduces a novel cooling method that incorporates an axially rotating impeller into the cavity of a small compliant grinding tool. The internal impeller structured compliant tool was prepared base on additive manufacturing. Numerical simulations and experimental studies were carried out to investigate its heat transfer mechanisms and its effect on the continuous grinding performance. The findings indicate that while favorable surface roughness and high material removal rates coincide with elevated grinding temperatures, the Shore hardness of the flexible material decreases as the grinding temperature rises. Consequently, there is a reduction in grit cutting depth and an increase in the proportion of rubbing and ploughing grit due to the grit’s height rearranges. The designed internal impeller facilitates the external cooling air with internal vortices to reach the grinding interface zone limiting heat accumulation to below 91.0°C and removing chips to reduce grit adhesion. Consequently, the grinding performance was more consistent, with a stable material removal depth ranging from 97 µm to 103 µm. 3D-printing-based compliant tools provide new insights into consistently high grinding performance for complex parts.

Evaluation of Pigment-Modified Clear Binders and Asphalts: An Approach towards Sustainable, Heat Harvesting, and Non-Black Pavements

Pavement construction practices have evolved due to increasing environmental impact and urban heat island (UHI) effects, as pavements, covering over 30% of urban areas, contribute to elevated air temperatures. This study introduces heat-reflective pavements, by replacing conventional black bitumen with a clear binder and pigment-modified clear binders. Titanium dioxide white, zinc ferrite yellow, and iron oxide red pigments are used to give asphalt corresponding shades. The asphalt and bitumen specimens were subjected to thermal analysis in heat sinks, under varying solar fluxes. The pigment dosage was maintained at 4%, according to the weight of the total mix, for all pigment types. The samples were heated and cooled for 3 h and 2 h, respectively. Mechanical testing was conducted to ascertain the impact of temperature variations on both the neat clear binder (C.B) and pigmented C.B and asphalt mixture samples. Wheel tracking and dynamic modulus tests were conducted to evaluate their performance under high temperatures. The results indicate that non-black asphalt mixtures exhibit significant temperature reductions, up to 9 °C, which are further enhanced by pigmented binders, up to 11 °C. It was found that asphalt with a clear or transparent binder demonstrated lower temperatures and faster heat dissipation in extreme conditions. Moreover, C.B asphalt mixtures displayed a rut resistance of 15%, with the pigmented C.B asphalt mixture showing a remarkable rut resistance of 73%, outperforming conventional asphalt. Non-black mixtures, especially C.B + zinc ferrite, showed improved resistance to permanent deformation in dynamic modulus tests.

Effect of Ethanol and Iso-Octane Blends on Isolated Low-Temperature Heat Release in a Spark Ignition Engine

<div>Low-temperature heat release (LTHR) is of interest for its potential to help control autoignition in advanced compression ignition (ACI) engines and mitigate knock in spark ignition (SI) engines. Previous studies have identified and investigated LTHR in both ACI and SI engines before the main high-temperature heat release (HTHR) event and, more recently, LTHR in isolation has been demonstrated in SI engines by appropriately curating the in-cylinder thermal state during compression and disabling the spark discharge. Ethanol is an increasingly common component of market fuel blends, owing to its renewable sources. In this work, the effect of adding ethanol to iso-octane (2,2,4-trimethylpentane) blends on their LTHR behavior is demonstrated. Tests were run on a motored single-cylinder engine elevated inlet air temperatures and pressures were adjusted to realize LTHR from blends of iso-octane and ethanol without entering the HTHR regime. The blends were tested with inlet temperatures of 40°C–140°C at equivalence ratios of 0.5, 0.67, and 1.0 with boosted (1.5 barA) conditions. The measured LTHR decreased with increasing ethanol content for all conditions tested; iso-octane–ethanol blends with above 20% ethanol content (by volume) showed minimal LTHR under engine conditions. These net effects resulted from the combination of thermal effects (charge cooling) and chemical effects (reactivity changes at low temperatures). The effect of temperature, pressure, fuel composition, and equivalence ratio on ignition delay times calculated from chemical kinetic modeling are presented alongside pressure–temperature trajectories of the in-cylinder gases to explain the trends. The underlying cause of the trends is explained by using a sensitivity analysis to determine the contribution of each reaction within the chemical kinetic mechanism to first-stage ignition, revealing the effect of introducing ethanol on the OH radical pool and resulting LTHR intensity.</div>

The effects of vitamin C and vitamin B12 on improving spermatogenesis in mice subjected to long-term scrotal heat stress.

Scrotal hyperthermia poses a significant threat to spermatogenesis and fertility in mammalian species. This study investigated the effects of vitamin B12 and vitamin C on spermatogenesis in adult male mice subjected to long-term scrotal hyperthermia. The rationale is based on the sensitivity of germ cells and epididymal sperm to increased scrotal temperatures. While various factors, both internal and external, can raise the testicular temperature, this study focused on the potential therapeutic roles of vitamins B12 and C. After inducing scrotal hyperthermia in mice, vitamin B12 and vitamin C were administered for 35 days. We assessed sperm parameters, serum testosterone levels, stereological parameters, the percentage of apoptotic cells, reactive oxygen species (ROS) levels, and glutathione (GSH) levels. Additionally, real-time polymerase chain reaction was used to analyze the expression of the c-kit, stimulated by retinoic acid gene 8 (Stra8), and proliferating cell nuclear antigen (Pcna) genes. Vitamin C was more effective than vitamin B12 in improving sperm parameters and enhancing stereological parameters. The study showed a significant decrease in apoptotic cells and a beneficial modulation of ROS and GSH levels following vitamin administration. Moreover, both vitamins positively affected the expression levels of the c-kit, Stra8, and Pcna genes. This research deepens our understanding of the combined impact of vitamins B12 and C in mitigating the effects of scrotal hyperthermia, providing insights into potential therapeutic strategies for heat stress-related infertility. The findings highlight the importance of considering vitamin supplementation as a practical approach to counter the detrimental effects of elevated scrotal temperatures on male reproductive health.

Sweet-spot operation of a germanium hole spin qubit with highly anisotropic noise sensitivity.

Spin qubits defined by valence band hole states are attractive for quantum information processing due to their inherent coupling to electric fields, enabling fast and scalable qubit control. Heavy holes in germanium are particularly promising, with recent demonstrations of fast and high-fidelity qubit operations. However, the mechanisms and anisotropies that underlie qubit driving and decoherence remain mostly unclear. Here we report the highly anisotropic heavy-hole g-tensor and its dependence on electric fields, revealing how qubit driving and decoherence originate from electric modulations of the g-tensor. Furthermore, we confirm the predicted Ising-type hyperfine interaction and show that qubit coherence is ultimately limited by 1/f charge noise, where f is the frequency. Finally, operating the qubit at low magnetic field, we measure a dephasing time of = 17.6 μs, maintaining single-qubit gate fidelities well above 99% even at elevated temperatures of T > 1 K. This understanding of qubit driving and decoherence mechanisms is key towards realizing scalable and highly coherent hole qubit arrays.

Next-Gen Lubrication: Water-cooled thrust bearings in conjunction with nano fluid lubricant

Thrust bearing finds application as a key element for heavy duty machines such as hydro-power plants (vertical shaft), submarines, steam engines, cement plant-ball mills (horizontal shaft) etc. Bearing temperature is a primary factor that affects the performance of hydrodynamic thrust bearings. Thermal deformation, misalignment, reduction in minimum oil film thickness and subsequent drop in load carrying capacity, are some of the manifestations related to high bearing temperatures. The present study attempts to decrease the bearing temperature by utilizing novel hybrid bearing set up. It involves the integration of water-cooled pads coupled with nanoparticle-infused lubricant films. This approach represents a convergence of two key technologies aimed at addressing the thermal effects linked with elevated temperatures generated during the operation of bearings. This study utilizes computational simulations to evaluate the effect of integrated thrust pad design on performance characteristics like pressure, temperature, and thermal deformation of a thrust bearing. The simulation results of new integrated design confirm (i) enhancement in pressure values e.g. maximum pressure increases from 5.6 MPa to 6.5 MPa (ii) reduction of pad temperature values e.g. maximum pad temperature value reduces from 85℃ to 70℃ (iii) reduction of pad thermal deformation values e.g. maximum pad thermal deformation value reduces from 36.5 µm to 22.3 µm. By leveraging the direct cooling effect of embedded cooling circuitry and the enhanced thermophysical properties of nanoparticles, this novel configuration promises to unlock new levels of efficiency and reliability in thrust bearing operation.

Enhanced Thermal Stability of Carbonyl Iron Nanocrystalline Microwave Absorbents by Pinning Grain Boundaries with SiBaFe Alloy Nanoparticles

Nanocrystalline carbonyl iron (CI) particles are promising microwave absorbents at elevated temperature, whereas their excessive grain boundary energy leads to the growth of nanograins and a deterioration in permeability. In this work, we report a strategy to enhance the thermal stability of the grains and microwave absorption of CI particles by doping a SiBaFe alloy. Grain growth was effectively inhibited by the pinning effect of SiBaFe alloy nanoparticles at the grain boundaries. After heat treatment at 600 °C, the grain size of CI particles increased from ~10 nm to 85.1 nm, while that of CI/SiBaFe particles was only 32.0 nm; with the temperature rising to 700 °C, the grain size of CI particles sharply increased to 158.1 nm, while that of CI/SiBaFe particles was only 40.8 nm. Excellent stability in saturation magnetization and microwave absorption was also achieved in CI/SiBaFe particles. After heat treatment at 600 °C, the flaky CI/SiBaFe particles exhibited reflection loss below −10 dB over 7.01~10.11 GHz and a minimum of −14.92 dB when the thickness of their paraffin-based composite was 1.5 mm. We provided a low-cost and efficient kinetic strategy to stabilize the grain size in nanoscale and microwave absorption for nanocrystalline magnetic absorbents working at elevated temperature.

Heat-induced structural and chemical changes to a computationally designed miniprotein.

The de novo design of miniprotein inhibitors has recently emerged as a new technology to create proteins that bind with high affinity to specific therapeutic targets. Their size, ease of expression, and apparent high stability makes them excellent candidates for a new class of protein drugs. However, beyond circular dichroism melts and hydrogen/deuterium exchange experiments, little is known about their dynamics, especially at the elevated temperatures they seemingly tolerate quite well. To address that and gain insight for future designs, we have focused on identifying unintended and previously overlooked heat-induced structural and chemical changes in a particularly stable model miniprotein, EHEE_rd2_0005. Nuclear magnetic resonance (NMR) studies suggest the presence of dynamics on multiple time and temperature scales. Transiently elevating the temperature results in spontaneous chemical deamidation visible in the NMR spectra, which we validate using both capillary electrophoresis and mass spectrometry (MS) experiments. High temperatures also result in greatly accelerated intrinsic rates of hydrogen exchange and signal loss in NMR heteronuclear single quantum coherence spectra from local unfolding. These losses are in excellent agreement with both room temperature hydrogen exchange experiments and hydrogen bond disruption in replica exchange molecular dynamics simulations. Our analysis reveals important principles for future miniprotein designs and the potential for high stability to result in long-lived alternate conformational states.

Nonlinear Analysis of Steel Fiber Reinforced Recycled Aggregate Concrete under Compression, Tension, and Elevated Temperatures

In this study, we report on experiments conducted to determine the compressive behaviour of steel fibre reinforced-recycled coarse aggregate concrete (SFRCAC). Many researchers are interested in exploring the utilize of recycled aggregate in concrete for its potential to reduce environmental impact. By using recycled materials in place of natural ones, Recycled Aggregate Concrete (RAC) represents a novel environmentally friendly construction material. Processing waste concrete with a high proportion of building waste yields recycled aggregates. Natural sand & gravel reserves have been drastically depleted, and natural resources used, as a result of the expansion of the construction sector. Fire damage caused by spalling is a major issue when considering the use of such concrete in construction. SFRAC could help with this. In this research, we provide the outcomes of an investigational study into the compressive properties, particularly the compressive strength, of SFRAC cylinders subjected to extreme temperatures. Compressive mechanical characteristics of concrete were studied as a function of temperature (room temperature, 200 ℃, 400 ℃, & 600 ℃) & steel fibre volume percentage (0%, 0.5%, 1%, 1.5%). Adding steel fibres to RAC that has been heated at high temperatures greatly improves its ductility & cracking behaviour, making it more appropriate for usage in building construction since it lessens the likelihood of spalling.

Danger in the Dark: Stability of Perovskite Solar Cells with Varied Stoichiometries and Morphologies Stressed at Various Conditions.

The long-term stability of perovskite solar cells (PSCs) remains a bottleneck for commercialization. While studies on the stoichiometry and morphology of PSCs with regard to performance are prevalent, understanding the influence of these factors on their long-term stability is lacking. In this work, we evaluate the impact of stoichiometry and morphology on the long-term stability of cesium formamidinium-based PSCs. We demonstrate that the lead iodide (PbI2) to formamidinium iodide (FAI) ratio influences stability under various stress factors (elevated temperature and light). A high molar ratio (PbI2/FAI > 1.1) in the perovskite precursor displays drastic degradation under ISOS-L1 (100 mW/cm2, 25 °C, maximum power point tracking) conditions. However, postdegradation analysis contradicts these results. Devices with PbI2/FAI ≤ 1.1 are stable under light, but intermittent current density-voltage characterizations indicate that device performance decreases during storage in the dark. Migration of iodide (I-) ions to the electron-transport layer (ETL) and iodine vacancies (VI-+) to the hole-transport layer (HTL) forms localized shunts in the absorber layer. Pinhole formation, surrounded by FA+-rich regions, explains the extent of damage in comparably aged films. In summary, this work emphasizes the importance of reporting stability under different stress conditions, coupled with postdegradation and dark recovery analyses of PSCs to better understand the complexities of perovskite instability under real-life conditions such as expected during outdoor operation.

Legionella is an emerging Public Health problem

The issue of Legionnaires’ disease has emerged as a major public health problem, interesting not only researchers, but also managers of public and private organisations, those responsible for public health, the general population and occasionally magistrates. The cases of legionellosis are increasing as a result of improved etiological diagnostic methods, population lifestyles and characteristics which favour the presence of the responsible organism in the environment which leads to the frequent exposure and transmission of the disease to at-risk groups whose relative numbers are growing. Legionella spp is an opportunistic waterborne pathogen that finds its ideal habitat in warm-humid environments, it is able to survive in conditions unfavourable to other germs (elevated temperatures, presence of biocides, etc.) and multiply in particular ecological niches (amoebas and other protozoa, biofilm). Because of this, it frequently colonises the hot water systems of houses, hotels, campsites, sports centres, hospitals, tertiary care centres, etc., as well as air-conditioning cooling towers, evaporative condensers and places where water stagnates at temperatures of at least 20°C. From our experience,the disease is frequently contracted by inhaling aerosols from the contaminated water systems of houses or work places, but it has also been contracted during stays in holiday accommodation, from using baths/showers in sports and recreation centres and finally during hospital stays.

The Relationship of Hot Work Climate on Physiological Response in Traditional Clover Leaf Oil Refining Workers

In the clove leaf oil refining process which uses steam, it produces a hot temperature residue which affects clove leaf oil refinery workers. Exposure to a hot working climate can have an impact on human physiological responses such as an increase in body temperature, pulse rate, blood pressure and weight loss. as a result of producing quite a lot of sweat fluid. This research aims to investigate the physiological responses of clove leaf oil refinery workers to exposure to a hot working climate. In the clove leaf oil refining process, which utilizes steam, the production of hot temperature residue affects the workers. Exposure to such conditions can lead to various physiological responses, including increased body temperature, pulse rate, blood pressure, and weight loss due to significant sweating. Employing a quantitative research design with a cross-sectional analytical approach, data were collected from all 22 workers using a total sampling technique. The primary data collected were subjected to analysis using paired simple t-tests and the Pearson correlation test to explore relationships between variables. The findings reveal significant increases in physiological responses post-work, including elevated body temperature, pulse rate, systolic and diastolic blood pressure, and a reduction in body weight. The obtained p-values for all variables were <0.05, indicating statistically significant differences between pre-work and post-work conditions. Furthermore, the Pearson correlation test analysis between heat stress data and post-work physiological responses, including body temperature, pulse rate, systolic and diastolic blood pressure, as well as body weight, revealed moderate to strong correlations (r). These results underscore the detrimental impact of hot working climates on the physiological well-being of clove leaf oil refinery workers. Such findings highlight the urgent need for implementing appropriate measures to mitigate heat-related health risks in occupational settings, safeguarding the health and safety of workers.