Heating Duration Research Articles

Investigations on deteriorations of concrete from surfaces to interiors under temperature gradient effects

In this investigation, in order to understand deterioration processes of concrete from surfaces to interiors under temperature gradient effects, 150mm cubic concrete specimens were heated without temperature-rising stages at 800° for 20min, 40min, 60min, 90min and 120min and then cooled with running water. For the purpose of evaluating deterioration characteristics of the heated concrete, compressive strengths and cracking conditions of heated concrete specimens, microstructural morphologies of concrete constituents, as well as dehydration degrees of concrete matrix from surfaces to interiors were determined. Results showed that during heating process, deterioration of concrete matrix from surfaces to interiors could be divided into a heat-influenced area, a semi heat-influence area and a heat-uninfluenced area. In heat-influenced area, dehydration degrees of hydration products were extremely severe, and the corresponding microstructural integrity almost completely lost. With increasing heating durations, heat-influenced areas gradually expanded towards concrete interiors, making the semi heat-influenced areas gradually become heat-influenced areas, and heat-uninfluenced areas become semi heat-influenced areas. Consequently, with increasing heating durations, compressive strengths of the heated concrete gradually decreased.

Experimental and numerical investigation of transparent insulation material to enhance the heating performance of an innovative Trombe Wall in Mediterranean climates

An innovative façade system in which the roof and side walls are transparent to solar radiation, with transparent insulating material parallel slats (TIM-PS) embedded between the glass façade and the solid wall, is proposed as a strategy to effectively reduce convective losses and intensify solar radiation penetration. This study proposes the validation of a model equipped with glass side walls and roof, using data provided by an experimental device. A numerical study was then carried out to investigate the effect of the TIM-PS included in the air duct and how the position of slats affects the performance of the proposed solution. The Optimal design is a T-T-W featuring with −45° TIM-PS. For the innovative T-T-W equipped with −45° TIM-PS heating duration has been extended by two hours. This original model allowed raising the thermal efficiency at 17H from 5% provided by the normal T-T-W up to 40%.

Effects of heat, elevated vapor pressure deficits and growing season length on growth trends of European beech

In recent decades, continued growth decline has been observed in various beech forest regions of Central and Western Europe, especially in the warmer lowlands, which is not necessarily linked to increased mortality. While earlier dendrochronological studies have shown that a deteriorating climatic water balance in the course of climate warming can drive negative growth trends, less is known about the effects of climatic extremes on tree growth, notably heat and rising atmospheric vapor pressure deficits (VPD). Through climate-growth analysis, we analyzed the influence of summer heat duration (frequency of hot days with Tmax > 30°C) and elevated VPD on the basal area increment (BAI) of dominant beech trees in 30 stands across a precipitation gradient in the northern German lowlands. Summer heat (especially in June) and elevated VPD are reducing BAI in a similar manner as does a deteriorated climatic water balance. While growing season length (GSL), derived from thermal thresholds of growth activity, has substantially increased since 1980, BAI has declined in the majority of stands, demonstrating a recent decoupling of tree productivity from GSL. We conclude that heat and elevated VPD most likely are important drivers of the recent beech growth decline in this region, while growing season length has lost its indicative value of beech productivity.

Transient heat transfer characteristics of cooling fluid loop with latent heat storage unit

In the realm of electronic cooling, it is of significance to efficiently manage the transient heat load. In this context, an innovative strategy is introduced by integrating a cooling fluid loop with a latent heat storage (LHS) unit. The effects of strategic positioning of LHS units on the dynamic temperature under varying conditions, such as heat load intensities, filling rates of phase change materials (PCMs), heating durations, and coolant flow rates, are examined and analyzed. The results indicate that the introduction of LHS unit can significantly alleviate the temperature fluctuation of microchannel heat sink (MHS) under instantaneous heat load. When the LHS unit is located upstream and downstream of the cooler, the maximum temperature of the MHS surface is reduced by 10 °C and 42 °C, respectively. The heat load determines the dynamic temperature characteristics of LHS units, and PCM performs best at precise melting states. When the heat storage of LHS unit matches the heat generated by the heating surface, further increasing the PCM filling rate has no positive effect, and extending the heating time is not conducive to cooling MHS. Additionally, increasing flow rate of working fluid has a limit effect on thermal enhancement of fluid loop with LHS.

Effect of post-weld heat treatment on microstructure and mechanical properties of induction roll welded joint for A283GRC steel and 5052 aluminum alloy

Steel-aluminum transition joints are commonly produced through explosive welding and friction welding techniques, serving to link aluminum pressure vessels with steel pipes within cold boxes in air separation unit. This study investigates the impact of PWHT on the microstructure and mechanical properties of steel-aluminum transition joints created via IRW, utilizing A283GRC steel and 5052 aluminum alloy as substrates. The findings suggest that the types of intermetallic compounds (IMCs) in IRW joints remain unchanged before and after heat treatment. The thickness of interfacial IMCs increases with higher annealing temperature and longer annealing time, with a faster growth rate at higher annealing temperatures. After PWHT, the grain size near the interface of the joint on the steel side decreased, with the most significant decrease observed when annealed at 300 °C for 2 hours. While cracks in the interface zone gradually diminish or disappear with PWHT, excessive heat treatment temperature or duration may result in new transverse cracks. At an annealing temperature of 200 °C, there is limited growth range for IMCs and noticeable repair effect on cracks within the interface region. When annealed at 300 °C and 400 °C, there is a decrease in joint hardness compared to before heat treatment levels, and this decreasing rate accelerates with higher annealing temperature and longer duration. Following annealing at 300 °C for 2 hours, the shear strength of the sample reached 70.52 MPa, which is 32% higher than that before heat treatment. Overall findings suggest that the annealing temperature exerts a more pronounced impact on the mechanical properties of joints in comparison to the annealing duration across the investigated time and temperature ranges. The fracture mode exhibited by the samples before and after heat treatment in IRW is characterized by a mixed fracture mode. However, the predominant fracture mode observed without heat treatment is brittle fracture, whereas after heat treatment, ductile fracture becomes the primary mode of fracture.

Microstructure and mechanical properties at elevated temperatures of as-built and heat-treated Inconel 718 produced through laser powder bed fusion processes

Purpose This study aims to better understand the influence of various post-treatments on the microstructure and mechanical properties of additively manufactured parts for critical applications. Design/methodology/approach In this study, Laser Powder Bed Fusion (LPBF) fabricated Inconel 718 (IN718) samples were subjected to various heat treatments, namely homogenization, solution heat treatment and double aging, to investigate their influence on the microstructure, mechanical properties and fracture mechanism at an elevated temperature of 650 °C. Homogenization treatment was performed at 1080 °C for durations ranging from 1–8 h. The solution treatment temperature varied from 980 °C to 1140 °C for 1 h, followed by double aging treatment. Findings At 650 °C, the as-built sample showed the minimum strength but demonstrated the maximum elongation to failure compared to the heat-treated samples. The strength of the IN718 superalloy increased by 20.26% to 34.81%, while ductility significantly reduced by 65.26% to 72.89% after various heat treatments compared to the as-built state. This change is attributed to the enhancement in grain boundary strength resulting from the pinning effect of the intergranular δ-phase. Originality/value The study observed that the variations in the fracture mechanism of LPBF fabricated IN718 depend on the duration and temperature of heat treatment. This research provides a thorough overview of the high-temperature mechanical properties of LPBF fabricated IN718 subjected to different homogenization times and solution treatment temperatures, correlating these effects to the corresponding changes in microstructure.

Thermal degradation of 18 amino acids during pyrolytic processes

Biomass pyrolysis greatly impacts climates, ecosystem dynamics, air quality, human health, global carbon and nitrogen cycle. The emissions of nitrogen-containing compounds from biomass pyrolysis highly depend on the protein nitrogen existing in biomass. However, the quantitative kinetic information, including the rate constant and apparent activation energy of individual amino acid induced by pyrolysis are still yet to be well-constrained. Towards this, we performed a series of controlled pyrolysis experiments where 18 equimolar free amino acids standard mixtures were pyrolyzed under ambient oxygen at temperatures between 160 and 240 °C. Additionally, straw samples were pyrolyzed to understand the mechanism of combined amino acids in protein liberation to free amino acids during pyrolytic processes. Our observations indicated that an increase in heating duration and temperature promote the degradation of free amino acids. Further, the heating stability of the 18 examined amino acids varied, which could be related to the length and functional groups present in their side chains. Our result shows that the degradation processes of all examined 18 amino acids followed irreversible first-order reaction kinetics in air within the given temperature range, with their activation energy ranging from 88.5 to 137.44 kJ mol−1. The distinct distribution patterns of both combined and free amino acids in aerosol samples from straw pyrolytic processes were obtained. The kinetic information of amino acids garnered herein helps to elucidate the transformation mechanisms of nitrogenous compounds during biomass burning.

Effect of Heat Treatment on Mechanical Characteristics and Microstructure of Aluminium Alloy AA6061

Aluminium alloy 6061 (AA6061) is widely used across various industries. It has untapped potential in diverse sectors due to its exceptional strength, lightweight characteristics and corrosion resistance. It finds value in aerospace, automotive, marine, sports gear, architecture, renewable energy, electronics, healthcare devices, packaging and defence. This study investigates the impact of heat treatment on AA6061 on its microstructural and mechanical properties (tensile strength and microhardness). The main goals of this study involve assessing the mechanical properties of AA6061 after subjecting it to solution heat treatment at various temperatures and time intervals. Furthermore, the study aims to understand the relationship between microstructural alterations and mechanical properties in AA6061 following heat treatment. A combination of tensile tests, hardness tests, and scanning electron microscopy (SEM) to examine the material's microstructure. The findings reveal that the sample subjected to the heat treatment of 450°C for 60 minutes exhibited the highest tensile strength, boasting an impressive 130.9 MPa, coupled with a remarkable hardness of 19.8 HRB. Conversely, the sample treated at 550°C for 60 minutes displayed the most significant elongation percentage, reaching a remarkable 46%. These results can be explained by analysing the microstructure. Finer grain boundaries led to increased tensile strength and hardness, while a larger dendritic microstructure was linked with lower tensile strength and hardness. Remarkably, the second one led to higher elongation percentages. Therefore, precise control of the heating temperature and duration is crucial to enhance the performance of aluminium alloy, AA6061. With continuous research, alloy improvement and creative design, AA6061 have the potential to enhance performance and efficiency in these areas, driving technological advancements and better products.

The human plasma lipidome response to exertional heat tolerance testing

BackgroundThe year of 2023 displayed the highest average global temperatures since it has been recorded—the duration and severity of extreme heat are projected to increase. Rising global temperatures represent a major public health threat, especially to occupations exposed to hot environments, such as construction and agricultural workers, and first responders. Despite efforts of the scientific community, there is still a need to characterize the pathophysiological processes leading to heat related illness and develop biomarkers that can predict its onset.MethodsLiquid chromatography-tandem mass spectrometry (LC–MS/MS)-based lipidomics analysis was performed on plasma from male and female subjects who underwent exertional heat tolerance testing (HTT), consisting of a 2-h treadmill walk at 5 km/h with 2.0% incline at a controlled temperature of 40ºC. From HTT, heat tolerance was calculated using the physiological strain index (PSI).ResultsNearly half of all 995 detected lipids from 27 classes were responsive to HTT. Lipid classes related to substrate utilization were predominantly affected by HTT, with a downregulation of triacylglycerols and upregulation of free fatty acids and acyl-carnitines (CARs). Even chain CAR 4:0, 14:0 and 16:1, suggested by-products of incomplete beta oxidation, and diacylglycerols displayed the highest correlation to PSI. PSI did not correlate with plasma lactate levels, suggesting that correlations between even chain CARs and PSI are related to metabolic efficiency versus physical exertion.ConclusionsOverall, HTT displays a strong impact on the human plasma lipidome and lipid metabolic inefficiencies may underlie reduced heat tolerance.

Bright Transparent Glass‐Ceramic Scintillators With High Fraction (Ca, Sr, Ba)1‐xYxF2+x: Tb Nanocrystals Precipitation for X‐ray Low‐Dose Detection and High‐Resolution Imaging

AbstractTransparent glass‐ceramic (GC) scintillator offers cost‐effective and large‐scale preparation for high‐resolution X‐ray imaging and detectors. However, it remains difficult to precipitate a high fraction of lanthanide activated fluoride nanocrystals that determine scintillation properties in glass. Herein, an ionic‐covalent fluoroaluminate‐phosphate glass network structure is constructed by combining simulation and experimental study, which enables the precipitation of (Ca, Sr, Ba)1‐xYxF2+x: Tb nanocrystals with high crystallinity (30.11%). By adjusting Tb doping concentration, heat treatment temperature and duration, a high internal quantum efficiency of 76.07%, the steady‐state light yield of 12710 photons MeV−1 and the lowest X‐ray detection of 180 nGyair s−1 are obtained. Finally, a high‐resolution (23.4 lp mm−1) X‐ray imaging application is realized by using the (Ca, Sr, Ba)1‐xYxF2+x: Tb GC scintillator. This provides a new option for the development of low‐cost, high‐performance scintillators for X‐ray high‐resolution imaging and low‐dose detection applications.

Optimum Thermal Treatment for Removing Antibiotic Resistance Genes and Retaining Nutrients in Poultry Broiler Manure

Poultry broiler manure is a reservoir of antibiotic resistance genes (ARGs), antibiotics, organic carbon, and plant nutrients. However, its direct application leads to spread of ARGs in agricultural fields, causing public concerns. It is thus crucial to identify optimum heating conditions that remove ARGs while retaining nutrients. This study examined the effects of heating temperatures (100-500oC) and durations (30, 120 and 240min) on the removals of ARGs and antibiotics from poultry broiler manure and nutrient retention. The results showed that the poultry broiler manure contained a total of 211 ARG subtypes, which were susceptible to temperature. The contents of ARGs and antibiotics decreased with increasing temperature. The temperature had a significant effect on the loss of available phosphorus (r = -0.893, P <0.01), while other nutrients had no significant loss. The results show that the heat treatment at 110°C for 240min maximized the removals of ARGs while the loss of nutrients was minimized. Under these optimum conditions, all ARGs and antibiotics (e.g., oxytetracycline, tetracycline, doxycycline, tilmicosin, tylosin, sulfamethazine, and sulfadiazine) were removed while 91.98% of total carbon, 99.89% of total nitrogen, 92.38% of total phosphorus, 50.10% of available phosphorus, 99.96% of total potassium, and 95.02% available potassium were preserved. These findings suggest that heat treatment at 110oC for 240min could be an effective and affordable approach to safe use of poultry broiler manure.

Cognitive decline in relation to later-life high temperature exposure in a Chinese nationwide cohort

Growing evidence has linked extreme temperature with neuropsychiatric disorders under climate warming with frequent extreme heat events over the past decades, while cognitive performance in relation to heat exposure remains largely unstudied, particularly in populations at high vulnerability to climate risks (e.g., China). Based on five survey waves of a nationwide dynamic cohort (2011–2020), we analyzed 47,825 cognitive test records from 14,729 respondents aged 45+ years across 126 Chinese cities. Global cognitive performance and its two dimensions (episodic memory and mental status) was measured using standardized questionnaires. Temperature exposure prior to cognitive tests was assessed using both average temperatures and heat days exceeding predefined temperature thresholds. Linear mixed-effects models were utilized to examine the relationship between high temperature exposure and cognitive function. This study revealed consistent evidence for heat-related declines in global cognitive performance and episodic memory across multiple exposure-window analyses, while robust associations were observed solely during prolonged exposure periods (more than 90 d) for mental status. For each 1-°C rise in annual mean temperature within 1 year prior to investigation, cognitive scores declined by 0.058 (95% CI: −0.079, −0.037) points for global performance, 0.033 (95% CI: −0.048, −0.018) points for episodic memory, and 0.025 (95% CI: −0.038, −0.013) points for mental status, respectively. Similar findings were seen in analyses using heat exposure days defined by multiple temperature percentiles, linking per 10-d increase in heat duration to reduced global cognitive scores ranging from −0.142 (95% CI: −0.214, −0.070) to −0.168 (95% CI: −0.254, −0.082). Despite varied evidence by heat exposure metrics and cognitive dimensions, stratified analyses suggested possibly higher susceptibility among females, less-educated, and urban-dwelling residents to heat-related cognitive impairment. These results provided suggestive evidence for the role of exposure to heat in triggering cognitive impairment in middle-aged and older individuals. This finding may be crucial in developing public health strategies for managing climate change risks of neurobehavioral disorders in a healthy aging society.

Optimizing prediction of stainless steel mechanical properties with random forest: a comparison of feature selection methods

In machine learning, predicting the mechanical properties of stainless steel, such as Yield Strength (YS), Ultimate Tensile Strength (UTS), and Elongation (EL), requires many input variables, such as chemical composition, type of heat treatment, heating duration, and cooling method. However, the complexity and number of these variables can increase processing time and reduce model accuracy. This study aims to explore the impact of selecting the most influential input variables to improve prediction accuracy. We compared two feature selection techniques: Recursive Feature Elimination (RFE), which systematically removes less important features, and Information Gain (IG), which measures the contribution of each variable to the target prediction. Both techniques were implemented using the random forest algorithm, chosen for its robustness in handling large datasets and its ability to capture complex interactions between variables. Parameter optimization was performed using a grid search. The analysis showed that the RFE-based model outperformed both the IG-based model and the model without feature selection. In predicting YS, RFE identified 13 out of 21 influential variables, achieving a Mean Absolute Error (MAE) of 9.91, Root Mean Square Error (RMSE) of 14.20, and R-squared value of 0.89. For UTS, RFE identified 8 out of 21 variables, with an MAE of 12.89, RMSE of 16.97, and R-squared of 0.97. In predicting EL, RFE identified 14 out of 21 variables, with an MAE of 3.82, RMSE of 6.10, and an R-squared value of 0.85. The high R-squared values (0.85) across all properties indicate the model’s strong predictive capabilities, making it suitable for practical applications in predicting the mechanical properties of stainless steel.

Global buckling and residual capacities of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) columns after exposure to fire

The post-fire flexural buckling behaviour and capacities of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) columns are studied in this paper, underpinned by testing and numerical modelling. A testing programme was firstly conducted on twelve column specimens designed with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), including nine column specimens after exposure to the ISO 834 standard fire for 15 min, 30 min and 45 min and three reference column specimens at ambient temperature. The test failure modes, load–mid-height lateral deflection curves and failure loads were reported in detail. The influences of heating durations and recycled coarse aggregate replacement ratios on failure loads and mid-height lateral deflections at failure loads of circular RACFSST column specimens were discussed and their lateral deflection distributions were analysed. The testing programme was followed by a numerical modelling programme, where thermal and mechanical finite element models were developed to repeat the experimental results and afterwards used to carry out parametric studies to generate a numerical data pool over a wide range of cross-section dimensions and member lengths. Based on the test and numerical data, the relevant design rules for circular natural aggregate concrete-filled carbon steel tube columns at ambient temperature, as specified in the European code, Australian/New Zealand standard and American specification, were evaluated, using post-fire material properties, for their applicability to circular RACFSST columns after exposure to fire. It was revealed from the evaluation results that the three design codes led to overall acceptable levels of accuracy and consistency in predicting post-fire flexural buckling capacities of circular RACFSST columns, but with some unsafe predictions.

Micro/Meso-Porous Double-Shell Hollow Carbon Spheres through Spatially Confined Pyrolysis for Supercapacitors and Zinc-Ion Capacitor.

Energy storage in supercapacitors and hybrid zinc ion capacitors (ZIC) using porous carbon materials offers a promising alternative method for clean energy solutions. The unique combination of hierarchical porous structure and nitrogen doping in these materials has demonstrated significant capacity for energy storage. Nevertheless, the full potential of these materials, particularly the relationship between pore structure configuration and performance, remains underexplored. Herein, a confined pyrolysis strategy based on the polymerization characteristics of polydopamine (PDA) was developed to construction of hollow carbon spheres with microporous/mesoporous dual shell structure. The depth of micropores and cavity can be controlled by adjusting the duration of heat treatment and hydrothermal treatment, in accordance with the decomposition and polymerization characteristics of PDA. Due to the elasticity of this structure, the relationship between the micro/mesoporous depth of the prepared carbon spheres and the energy storage performance in supercapacitors and ZIC is established. Through optimizing the ion transport capacity of carbon spheres and considering the influence of its internal cavity structure on energy storage, the resulting carbon spheres exhibit high specific capacitance of 389 F g-1 in supercapacitor and specific capacitance of 260 F g-1 and excellent stability with 99.3 % retention after 30000 chare/discharge cycles in ZIC.

Micro/Meso‐Porous Double‐Shell Hollow Carbon Spheres through Spatially Confined Pyrolysis for Supercapacitors and Zinc‐Ion Capacitor

AbstractEnergy storage in supercapacitors and hybrid zinc ion capacitors (ZIC) using porous carbon materials offers a promising alternative method for clean energy solutions. The unique combination of hierarchical porous structure and nitrogen doping in these materials has demonstrated significant capacity for energy storage. Nevertheless, the full potential of these materials, particularly the relationship between pore structure configuration and performance, remains underexplored. Herein, a confined pyrolysis strategy based on the polymerization characteristics of polydopamine (PDA) was developed to construction of hollow carbon spheres with microporous/mesoporous dual shell structure. The depth of micropores and cavity can be controlled by adjusting the duration of heat treatment and hydrothermal treatment, in accordance with the decomposition and polymerization characteristics of PDA. Due to the elasticity of this structure, the relationship between the micro/mesoporous depth of the prepared carbon spheres and the energy storage performance in supercapacitors and ZIC is established. Through optimizing the ion transport capacity of carbon spheres and considering the influence of its internal cavity structure on energy storage, the resulting carbon spheres exhibit high specific capacitance of 389 F g−1 in supercapacitor and specific capacitance of 260 F g−1 and excellent stability with 99.3 % retention after 30000 chare/discharge cycles in ZIC.

Post fire flexural behavior of mild steel based cold-formed built-up beams exposed to elevated temperature

The use of back-to-back built-up channel beams in cold-formed steel (CFS) structures is steadily rising. The growing demand for CFS sections as a cost-effective design solution has driven the development of these CFS built-up sections. Despite this, there has been limited research on the performance of mild steel (MS) based CFS at high temperatures, particularly regarding its flexural behavior. This study thoroughly explores the behavior of MS-based CFS beams with different spans under high temperatures, followed by cooling with air or water. It assesses the impact of thermal loading and evaluates the effectiveness of these cooling methods. Experimental findings are validated and analyzed in conjunction with Finite Element Modeling (FEM) using ABAQUS and the Direct Strength Method (DSM). The study also conducts a parametric analysis to determine how the varying span that affects flexural capacity of beam. Among beams heated to the same temperature, those cooled with water exhibit slightly lower load capacities than those cooled with air. The maximum load observed is 91.21 kN for the reference specimen, while the minimum load is 39.82 kN for the specimen heated for 90 min and cooled with water, resulting in a 78.45% difference between these values. Additionally, as heating duration increases, ductility of beam also increases. Various failure modes are observed based on different heating and cooling conditions across different beam spans. This study offers valuable insights into the performance of MS-based CFS beams under thermal stress and different cooling conditions, providing important data for structural design and safety in construction.

Optimization of Production Parameters for Impact Strength of 3D-Printed Carbon/Glass Fiber-Reinforced Nylon Composite in Critical ZX Printing Orientation.

Additive manufacturing (AM) methods are increasingly being adopted as an alternative for mass production. In particular, Fused Deposition Modeling (FDM) technology is leading the way in this field. However, the adhesion of the layers in products produced using FDM technology is an important issue. These products are particularly vulnerable to forces acting parallel to the layers and especially to impact strength. Most products used in the industry have complex geometries and thin walls. Therefore, solid infill is often required in production, and this production must take place in the ZX orientation. This study aims to optimize the impact strength against loads acting parallel to the layers (ZX orientation) of PA6, one of the most widely used materials in the industry. This orientation is critical in terms of mechanical properties, and the mechanical characteristics are significantly lower compared to other orientations. In this study, filaments containing pure PA6 with 15% short carbon fiber and 30% glass fiber were utilized. Additionally, the printing temperature, layer thickness and heat treatment duration were used as independent variables. An L9 orthogonal array was employed for experimental design and then each experiment was repeated three times to conduct impact strength tests. Characterization, Taguchi optimization, and factor analyses were performed, followed by fracture surface characterization by SEM. As a result, the highest impact strength was achieved with pure PA6 at 8.9 kJ/m2, followed by PA6 GF30 at 8.1 kJ/m2, and the lowest impact strength was obtained with PA6 CF15 at 6.258 kJ/m2. Compared to the literature and manufacturer datasheets, it was concluded that the impact strength values had significantly increased and the chosen experimental factors and their levels, particularly nozzle temperature, were effective.

Crystallization and luminescence properties of stable CsPbBr3 Nanocrystals in Li2B4O7 glass

All-inorganic CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals (NCs), have achieved unprecedented advances in opto-electronic applications. However, issues such as poor stability and the volatility of halides in the preparation process continue to hinder their practical applications. Here, lithium tetraborate (Li2B4O7) was chosen as the glass matrix to prepare CsPbBr3 NCs glasses through traditional melting-quenching and heat treatment processes, effectively reducing the glass synthesis temperature to 940 °C. The heat treatment temperature and duration are examined. The Li2B4O7 glass matrix exhibits a uniform structure and high transmittance and CsPbBr3 NCs precipitated uniformly after heat treatment. Among these glasses, the sample heat-treated at 510 °C for 5 h exhibited an optimal photoluminescence quantum yield of 76.1 % and the narrowest full width at half maximum values of 24 nm. Its photoluminescence intensity maintained 96.6 % of its original value after multiple thermal cycles and thermal shocks, demonstrating the sample's robust thermal stability. Finally, by integrating the CsPbBr3 NCs glass sample with a blue chip in simple device packaging, a green light-emitting diode was successfully fabricated, featuring excellent luminescence stability and a color purity of up to 96.4 %, promising for applications in solid-state lighting and display technologies.

Frozen and unfrozen moisture content estimation in coral calcareous sand during artificial freezing

In tropical areas where coral calcareous sands are prevalent, artificial freezing techniques are frequently employed during construction. However, the fundamental thermodynamic behaviors and moisture dynamics of calcareous sands under freezing conditions are poorly understood. Therefore, we conducted laboratory tests and developed a numerical model to capture the total moisture, liquid water, and ice contents of calcareous sand during artificial freezing. The thermal fiber Bragg grating (T − FBG) and frequency − domain reflectometry methods were used in the study. Freezing characteristic curves were quantitatively analyzed with taking into account the initial moisture content and ambient temperature. The results indicate that T − FBG effectively estimates the total moisture content in unfrozen and frozen calcareous sand, as well as ice content in frozen soil, with less than 0.029 m3/m3 error. Ice melting induced by T − FBG heating is affected by the initial moisture content, heating duration, power, and ambient temperature. However, the maximum change is below 0.008 m3/m3, which is negligible. The van Genuchten model accurately describes the liquid moisture–temperature relationship of unsaturated calcareous sand, with an R2 exceeding 0.98. The residual–initial moisture content relationship follows a quadratic function. During freezing, the temperature reduction aligns with the Kozlowski model, and the liquid moisture–temperature relationship follows a cubic polynomial function.