Elevated Temperature Conditions Research Articles

Microstructural analysis and tribological characteristics of thermally sprayed Co-Ni-O ternary oxide coatings

Due to their high thermal and chemical stability, ternary oxide coatings have been extensively investigated as potential solutions for high-temperature solid lubrication. In this study, the tribological behavior of the thermally sprayed Co0.75Ni0.25O and Co0.5Ni0.5O oxide coatings was investigated. The dry sliding reciprocating friction tests were performed against an Al2O3 counterface at room and elevated temperatures using a ball-on-flat tribometer. The results indicated that the friction and wear of Co0.75Ni0.25O oxide coatings did not change significantly at atmospheric and elevated temperature conditions, whereas the friction and wear of the Co0.5Ni0.5O increased at elevated temperatures. The correlations between the worn surface morphologies, the subsurface microstructure induced by wear, and the wear behavior of the coatings were discussed based on the characterizations, (i.e., microhardness, scanning electron microscopy (SEM), and electron channeling contrast imaging (ECCI)).

CO2-brine interactions in anhydrite-rich rock: Implications for carbon mineralization and geo-storage

The utilization of subsurface geologic media for carbon capture and storage through mineralization has been recognized as a reliable approach. However, less attention has been given to anhydrite rock type for CO2 mineralization and storage. Anhydrite-rich rock formations, commonly found in various geological settings, have the potential to serve as natural carbon sinks through the mineralization of CO2. Therefore, this study aims to investigate the mechanisms and potential of anhydrite-CO2-brine interactions for carbon storage. The experimental approach involved exposing anhydrite-rich rock to supercritical CO2-brine environments under varying conditions of fluid composition. Mineral transformation of an outcrop anhydrite-rich rock sample in static reactor under subsurface conditions of elevated temperature (60 °C) and pressure (104 bar), in the absence and the presence of SrCl2 was conduct for a one-month period. Mineralogical and geochemical analyses, including, solution analyses, X-ray fluorescence, X-ray diffraction, micro-computed tomography, and mechanical properties were conducted to examine the changes in the composition and rock structure resulting from the interactions. The experimental reactions revealed that anhydrite undergoes mineral transformation upon exposure to supercritical CO2-saturated brine to form stable minerals including calcite, dolomite, magnesite, and strontianite, which contributes to the potential for long-term storage of CO2 in the subsurface geologic media. The efficiency and extent of carbon mineralization were found to be influenced by brine composition. These findings contribute to the understanding of the potential of these formations for carbon storage, opening avenues for further research and the development of effective carbon capture and storage strategies.

Mechanical and failure analysis of “outer single lap” adhesive joints of carbon fiber reinforced plastics under hygrothermal conditions

Carbon fiber reinforced plastics (CFRP)laminates are widely used in aircrafts. The laminates are often assembled into components by adhesive joints, which will be affected by elevated temperature and humidity during use, resulting in performance degradation. In this study, a compression test of “Outer Single Lap” adhesive joints of CFRP on the rear fuselage of a certain type of navigable aircraft was carried out to investigate the influence of hygrothermal conditions on their performance. The experimental environment includes the elevated temperature and wet condition (ETW) (71 °C, 85%RH) and Room temperature drying (RTD) (23 %, 30%RH). The test results show that RTD specimens have different stages, and the initial stage has good plasticity and no damage. However, when the load reached 50 %, the initial opening pattern damage occurred, which eventually led to the failure of the 20° opening. Compared with RTD samples, the compression properties of ETW samples decreased by 47.7 %, and the opening damage disappeared. Fracture features and stain analysis were performed. The findings suggest the fracture characteristic can change from a brittle fracture to a ductile fracture in different testing conditions, and the influence of the humid and thermal environment on the resin structural adhesive layer itself, the compression state of the carbon fiber laminates, the interface between the carbon fiber laminates and the resin structural adhesive layer should be fully considered in the design.

Low- and elevated-temperature constitutive model of cold-formed titanium-clad bimetallic steel sections

An experiment was conducted to study the mechanical properties of the flat and corner portions of cold-formed TCBS sections at low and elevated temperatures. The predetermined temperatures were set at −80 °C, −40 °C, 20 °C, 200 °C, 300 °C, 400 °C, and 500 °C. The failure modes, stress-strain curves, and key mechanical parameters of TCBS flat and corner couple specimens at different temperatures were obtained based on test results. The TCBS flat and corner specimens failed in ductile mode. The stress-strain curves of the TCBS flat and corner specimens at different temperatures did not show a yield plateau. The strength properties of TCBS flat and corner specimens at low temperatures obviously increased. The strength properties of the TCBS flat and corner specimens generally decreased with increasing elevated temperature. The cold-forming process increased and decreased the strength and ductile properties of TCBS at different temperatures, respectively. Additionally, the mechanical property reduction factors of TCBS flat and corner specimens at different temperatures were compared with those of various structural steels. Moreover, the applicability of the reduction factors for yield strength and elastic modulus provided in current codes was assessed for TCBS flat and corner specimens. Furthermore, the prediction equations of mechanical parameters and constitutive models were proposed for the TCBS flat and corner couple specimens at different temperatures, which provided a basis for designing TCBS structures in low- and elevated-temperature conditions.

Study of CO2 Adsorption Properties on the SrTiO3(001) Surface with Ambient Pressure XPS.

The adsorption properties of CO2 on the SrTiO3(001) surface were investigated using ambient pressure X-ray photoelectron spectroscopy under elevated pressure and temperature conditions. On the Nb-doped TiO2-enriched (1 × 1) SrTiO3 surface, CO2 adsorption, i.e., the formation of CO3 surface species, occurs first at the oxygen lattice site under 10-6 mbar CO2 at room temperature. The interaction of CO2 molecules with oxygen vacancies begins when the CO2 pressure increases to 0.25 mbar. The adsorbed CO3 species on the Nb-doped SrTiO3 surface increases continuously as the pressure increases but starts to leave the surface as the surface temperature increases, which occurs at approximately 373 K on the defect-free surface. On the undoped TiO2-enriched (1 × 1) SrTiO3 surface, CO2 adsorption also occurs first at the lattice oxygen sites. Both the doped and undoped SrTiO3 surfaces exhibit an enhancement of the CO3 species with the presence of oxygen vacancies, thus indicating the important role of oxygen vacancies in CO2 dissociation. When OH species are removed from the undoped SrTiO3 surface, the CO3 species begin to form under 10-6 mbar at 573 K, thus indicating the critical role of OH in preventing CO2 adsorption. The observed CO2 adsorption properties of the various SrTiO3 surfaces provide valuable information for designing SrTiO3-based CO2 catalysts.

Floral Response to Heat: A Study of Color and Biochemical Adaptations in Purple Chrysanthemums.

Chrysanthemums are among the world's most popular cut flowers, with their color being a key ornamental feature. The formation of these colors can be influenced by high temperatures. However, the regulatory mechanisms that control the fading of chrysanthemum flower color under high-temperature stress remain unclear. This study investigates the impact of high temperatures on the color and biochemical responses of purple chrysanthemums. Four purple chrysanthemum varieties were exposed to both normal and elevated temperature conditions. High-temperature stress elicited distinct responses among the purple chrysanthemum varieties. 'Zi Feng Che' and 'Chrystal Regal' maintained color stability, whereas 'Zi Hong Tuo Gui' and 'Zi lian' exhibited significant color fading, particularly during early bloom stages. This fading was associated with decreased enzymatic activities, specifically of chalcone isomerase (CHI), dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase (ANS), indicating a critical period of color development under heat stress. Additionally, the color fading of 'Zi Lian' was closely related to the increased activity of the peroxidase (POD) and polyphenol oxidase (PPO). Conversely, a reduction in β-glucosidase (βG) activity may contribute significantly to the color steadfastness of 'Zi Feng Che'. The genes Cse_sc027584.1_g010.1 (PPO) and Cse_sc031727.1_g010.1 (POD) might contribute to the degradation of anthocyanins in the petals of 'Zi Hong Tuo Gui' and 'Zi Lian' under high-temperature conditions, while simultaneously maintaining the stability of anthocyanins in 'Zi Feng Che' and 'Chrystal Regal' at the early bloom floral stage. The findings of this research provide new insights into the physiological and biochemical mechanisms by which chrysanthemum flower color responds to high-temperature stress.

A functional MXene/cellulose nanofibers separator for high-performance dendrite-free zinc anode under harsh conditions

Aqueous zinc-ion batteries (AZIBs) show great potential for mass energy storage because of their intrinsic plentifulness and security. Nevertheless, the development of zinc dendrites is still a major challenge for the practical industrialisation of AZIB, especially under the demanding conditions of elevated current density and high temperatures. To combat this situation, we developed an ultrathin separator composed of cellulose nanofibers and MXene (noted as CM-15 separator) with a thickness of only 27 μm. The strong zincophilic characteristics and outstanding electrical/thermal conductivity of MXene make them suitable for use as an ion pump to expedite the transmission of Zn2+ through the electrolyte, which significantly increases the zinc ion transfer number and results in the deposition of homogeneous Zn nuclei and dendritic-free Zn. As a result, the symmetric battery equipped with a CM-15 separator enabled excellent dendrite free plating/stripping behavior, high coulomb efficiency (97.7 %) and cumulative plated capacity of 4.8 Ah/cm2 at 80 mA/cm2 at room temperature and as well as sustained operation for at least 300 h under 60 °C. More impressively, the Zn-MnO2/CNT battery equipped with a CM-15 separator achieved 72.6 % capacity retention after 10,000 cycles at 2 A/g under room temperature and 92.1 % capacity retention after 200 cycles at 1 A/g under 60 °C. Our research confirms the potential of functional separators to promote the application of AZIBs, especially under demanding conditions.

Effect of immediate curing at elevated temperatures on the tensile and interfacial properties of carbon fiber-epoxy composites

Elevated temperature conditions known to improve curing from the onset and during the process of immediate curing are not available in the field, which can hinder the mechanical performance of these strengthening systems. In this study, mechanical testing and material characterization were conducted to identify the effects of subjecting nanomodified epoxy and fiber-reinforced nanomodified epoxy composites to room temperature (RT) (30 °C) and elevated temperature (110 °C) from the onset of curing. Static tensile testing and interfacial adhesion tests were conducted to evaluate the mechanical performance. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to determine curing characteristics to inform on the immediate curing of nanomodified resins cured under the two temperature conditions. Scanning electron microscopy was performed to identify Carbon nanotube (CNT) dispersion characteristics. Overall, due to the incorporation of CNTs in epoxy, RT curing results in upto 62% increase in strain at failure. By supplying additional energy during immediate curing with elevated temperatures, a 51% increase in strength and 42% increase in Youngs Modulus can be observed in the nanomodified epoxy. In CFRP-epoxy composites, due to the incorporation of CNTs in the epoxy, RT curing results in upto 27% increase in strain at failure. By supplying additional energy during immediate curing with elevated temperatures, upto 133% increase in strain at failure is observed and upto 17% increase in strength is observed. CNTs incorporated in CFRP-epoxy composites demonstrated upto 50% increase in interfacial adhesion whereas supplying additional energy for their immediate curing with elevated temperatures, upto 130% increase in interfacial adhesion was observed. TGA and DSC results supported the mechanical observations and show a need for immediate curing when CNTs are used in epoxy matrices.

Propiedades de un hormigón de alto desempeño fabricado con un proceso de producción convencional

Among cement-based composites, materials that show a growing interest are the High Performance Concrete (HPC) and Ultra-hi-gh Performance Concrete (UHPC), which are categorized by an effective screening of granular elements, and an elevated quantity of fiber reinforcement [1]. HPC is produced through the particle packing methodology to enhance its matrix density and reduce its porosity [2]. Because of this producing me-thod, this material has a lower water content than conventional concrete, and better me-chanical performance and durability [3]-[5]. It is thus suitable to build several structural elements [6], [7] thanks to its enhanced pro-perties. On the other hand, the manufacture of HPC is not straightforward: expensive raw materials, impact on the environment, labo-rious fabrication and curing tasks [8], [9] are among the most important obstacles to its large-scale use. It is therefore relevant and recommended to simplify its production process. This work present new HPC mixtu-res that are produced in a straightforward manner, without requiring elevated tempe-rature curing conditions, mixers with high power or temperature controlled chambers, as commonly used for current HPC sold in the market. The mixtures described here showed a split tensile strength of 5 MPa, a compressive strength of over 70 MPa, and a virtual packing density of 0.86.

Shrinkage characteristics of glass and mineral fibre insulation materials at elevated temperatures

The fire resistance of building assemblies can be determined through testing or by numerical modelling. As testing of building assemblies is expensive and time-consuming, the development of numerical modelling methods is gaining momentum. One of the challenges in modelling assemblies’ thermal performance is insulation dimensional shrinkage at elevated temperatures. To address this challenge, this paper presents a comprehensive experimental investigation into the shrinkage of glass and mineral fibre insulation materials under elevated temperature conditions. Initially, a series of tests was conducted to establish the temperature range within which significant shrinkage occurs for both types of insulation. Then, visual observations and measurements were recorded to assess the physical and dimensional changes of the insulation materials within the identified temperature range for shrinkage, indicating distinct responses of glass and mineral fibre insulation to thermal exposure. Compared to width and length variations, thickness reduction in insulation was more significant. Overall, the insulation thickness decreased as the exposed temperature increased. The glass fibre insulation completely melted at 710°C, while mineral fibre insulation disintegrated at 1000°C. In addition, empirical equations were derived to assess the thickness variations of these insulations at elevated temperatures, which can greatly enhance the accuracy of future thermal models under fire scenarios. Lastly, potential areas for future research are identified.

Dependence of the incorporated boron concentration near SiO2/4H–SiC interface on trap passivation reduction

By systematically varying the boron concentration near the oxide/4H–SiC interface within a specifically designed boron-diffusion layer oxide structure, this paper explores the influence of boron concentration on interface state density and near-interface trap density in 4H–SiC MOS capacitors. Additionally, the effect of boron near the oxide/4H–SiC interface on device stability under elevated temperature conditions was examined. The boron species were introduced into the SiO2/4H–SiC interface by spin coating followed by annealing, whose temperature controls the amount of boron present in the near interface region. It is suggested that a higher concentration of boron leads to a better trap passivation effect while preserving the stability of flat band voltage.

Development and validation of stability-indicating method of etrasimod by HPLC/DAD/MS/MS technique with greenness profiling

Etrasimod, a novel selective sphingosine-1-phosphate receptor modulator, was recently approved by the U.S. Food and Drug Administration and the European Medicinal Agency for the treatment of moderately to severely active ulcerative colitis in adults. In this research, the forced degradation study as an integral part of drug product and packaging development, which generates data on degradation mechanisms, is published. The development and validation of the stability-indicating method using a superior high-performance liquid chromatography technique coupled with a diode array detector and tandem mass spectrometer was performed to support the forced degradation study and monitor the formation of degradation products. Etrasimod demonstrated good stability under elevated temperature and basic stress conditions, while acidic hydrolysis, oxidative, and photolytic degradation produced eight degradation products. The knowledge of degradation products will be useful in the long-term stability study for establishing the acceptance criteria of etrasimod as a drug substance and dosage form during quality control and stability assessment. The eco-friendliness of the developed forced degradation procedure was evaluated using various greenness appraisal tools. The green metric tools showed that the forced degradation procedure obeys eco-friendly conditions.

Localized loading behavior of cold-formed stainless steel RHS under interior-one-flange load case at elevated temperatures

The localized loading behavior of cold-formed stainless steel (CFSS) rectangular hollow section (RHS) members at elevated temperatures is investigated in this paper. Fifteen localized loading tests conducted at various temperatures up to 800 °C were reported. The tests were carried out under the Interior-One-Flange (IOF) load case as specified in American Specification for the design of cold-formed stainless steel structural members. Tensile coupon tests were performed to obtain the material properties of the CFSS RHS at various temperatures. Detailed information on dimensions, temperature histories, failure modes, load-deformation curves, localized loading capacities of specimens at various temperatures were presented. In addition, a numerical investigation was supplemented, where a total of 192 finite element (FE) analyses were undertaken after validation of developed FE model against the elevated-temperature test results. The influence of various parameters on the localized loading capacities of CFSS RHS at different temperatures under IOF load case was revealed. The obtained results were utilized to assess the applicability of the localized loading design provision for CFSS RHS under IOF load case codified in the American Specification to elevated temperature conditions. Moreover, the results were also compared with predictions based on existing design rules in literatures for cold-formed RHS at elevated temperatures. Furthermore, reliability analyses were carried out to assess the reliability levels of the assessed design methods. It is shown that the existing design rules can generally provide conservative and reliable predictions of the localized loading capacities for the CFSS RHS under IOF load case at elevated temperatures.

Effects of the nitrification inhibitor nitrapyrin on N2O emissions under elevated CO2 and rising temperature in a wheat cropping system

Nitrogen (N) fertilizer input will likely increase to meet the food demands of a growing population under climate change conditions, characterized by increasing atmospheric CO2 concentration and temperature. Nitrification inhibitors have the potential to reduce N2O emissions from N fertilized croplands. However, it remains unclear whether future climate change scenarios could affect the effectiveness of nitrification inhibitors. In a two-year study, winter wheat (Triticum aestivum L.) was cultivated in climate-controlled growth chambers with an elevated CO2 concentration (ambient +200 μmol mol−1) and increased temperature (ambient +2 °C). Urea was applied with or without nitrapyrin (0.5 % of urea-N). In this study, we measured nitrous oxide (N2O) fluxes, soil ammonium and nitrate levels, and the abundance of five nitrogen-cycling genes related to nitrification (amoA of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA)) and denitrification (nirS, nirK and nosZ). Key findings included the following: 1) without nitrapyrin, cumulative N2O emissions were not significantly altered by increased temperature, but decreased 24.9 % by the combination of elevated CO2 and temperature treatment and 17.5 % by the elevated CO2 alone. NO3−-N accumulation occurred in soils under increased CO2 and temperature, both individual and in combination; 2) nitrapyrin effectively reduced AOB abundance, inhibiting NO3−-N accumulation and N2O emission, irrespective of CO2 concentrations and temperature. However, under the combination of elevated CO2 and temperature conditions, the efficiency of nitrapyrin in reducing N2O emission was lower (−13 % to −49 %) than that in the control (−28 % to −65 %) and elevated CO2 (−32 % to −71 %) conditions. This reduced effectiveness of the combined treatment can be attributed to the inability of nitrapyrin to inhibit the AOA, nirS and nirK genes. Thus, nitrapyrin is expected to reduce N2O emissions under future climate change scenarios, but the efficacy may be lower than previously expected when CO2 concentration and temperature increase simultaneously. The indirect effects of nitrapyrin on denitrifiers under climate change scenarios should be considered in future research.

Recent Progress in Creep-Resistant Aluminum Alloys for Diesel Engine Applications: A Review.

Diesel engines in heavy-duty vehicles are predicted to maintain a stable presence in the future due to the difficulty of electrifying heavy trucks, mine equipment, and railway cars. This trend encourages the effort to develop new aluminum alloy systems with improved performance at diesel engine conditions of elevated temperature and stress combinations to reduce vehicle weight and, consequently, CO2 emissions. Aluminum alloys need to provide adequate creep resistance at ~300 °C and room-temperature tensile properties better than the current commercial aluminum alloys used for powertrain applications. The studies for improving creep resistance for aluminum casting alloys indicate that their high-temperature stability depends on the formation of high-density uniform dispersoids with low solid solubility and low diffusivity in aluminum. This review summarizes three generations of diesel engine aluminum alloys and focuses on recent work on the third-generation dispersoid-strengthened alloys. Additionally, new trends in developing creep resistance through the development of alloy systems other than Al-Si-based alloys, the optimization of manufacturing processes, and the use of thermal barrier coatings and composites are discussed. New progress on concepts regarding the thermal stability of rapidly solidified and nano-structured alloys and on creep-resistant alloy design via machine learning-based algorithms is also presented.

Direct evidence of gas flushing oil in deep reservoirs: Insight from integrated fluid inclusion analyses

Gas flushing of oil has been proposed as an essential process for forming some condensate gas reservoirs based on laboratory experiments and modeling but such a process has rarely been documented in subsurface reservoirs. Here, we report a unique type of yellow-ringed oil inclusions (YROIs) discovered from a deep reservoir in the Kuqa Foreland Basin, Western China that recorded the gas flushing of oil process in the subsurface. The occurrence, composition, phase state and PVT conditions of YROIs during trapping were investigated using a suite of fluid inclusion analytical methods including fluid inclusion petrography, microthermometry, fluorescence spectroscopy, PVT modeling and molecular composition analysis.YROIs found in the reservoir are three-phase (solid–liquid-vapor) fluid inclusions at room temperature with solid rings of 2–3 μm thickness and estimated volume percentages varying between 5 % and 15 %. When heated the solid ring starts to melt at around 46 °C and homogenized with the liquid phase at or above their corresponding homogenization temperatures of coeval aqueous inclusions. YROIs have fluorescence spectral peaks between 530 nm and 550 nm and an elevated spectral shoulder around 650 nm when measured at room temperature; but most spectra show a distinct “blue shift” and an absence of the 650 nm shoulder when measured at their homogenization temperatures. Some YROIs with thick yellow rings show dual spectral peaks at 570 nm and 630 nm at room temperature and their spectral peaks do not change when remeasured at their homogenization temperatures. Molecular compositions derived from synchronous fluorescence spectra and GC-MS analysis suggest that the compositions of YROIs are rich in polyaromatic compounds. PVT modeling indicates that YROIs were trapped under high pressure conditions with a pressure exceeding 50 % of the corresponding hydrostatic pressure.YROIs are interpreted to have been trapped under an elevated temperature and overpressure condition (around 110 °C and 60 MPa) relating to an intensive (wet) gas flushing of an early-charged wax-rich oil. When light hydrocarbon components in the reservoir oil were partially removed by gas, the wax/resin components rich in polyaromatic hydrocarbon compounds may precipitate due to physio-chemical fractionation. YROIs were entrapped in subsurface from a heterogeneous hydrocarbon fluid containing variable amounts of wax/resin colloids, which subsequently coalesce to form solid rings adhering to the inner wall of oil inclusions at room temperature. The presence of yellow-ringed oil inclusions in a reservoir may be indicative of a rapid gas flushing of waxy oil under high pressure, and their minimum homogenization temperature may approximate their trapping temperature.

Changes in the Growth and Fruit Yield of Hot Peppers Grown under Elevated CO2 and Temperature Conditions

Changes in the Growth and Fruit Yield of Hot Peppers Grown under Elevated CO2 and Temperature Conditions

Isolation, identification, and tolerance analysis of yeast during the natural fermentation process of Sidamo coffee beans.

Yeast, which plays a pivotal role in the brewing, food, and medical industries, exhibits a close relationship with human beings. In this study, we isolated and purified 60 yeast strains from the natural fermentation broth of Sidamo coffee beans to screen for indigenous beneficial yeasts. Among them, 25 strains were obtained through morphological characterization on nutritional agar medium from Wallerstein Laboratory (WL), with molecular biology identifying Saccharomyces cerevisiae strain YBB-47 and the remaining 24 yeast strains identified as Pichia kudriavzevii. We investigated the fermentation performance, alcohol tolerance, SO2 tolerance, pH tolerance, sugar tolerance, temperature tolerance, ester production capacity, ethanol production capacity, H2S production capacity, and other brewing characteristics of YBB-33 and YBB-47. The results demonstrated that both strains could tolerate up to 3% alcohol by volume at a high sucrose mass concentration (400g/L) under elevated temperature conditions (40 ℃), while also exhibiting a remarkable ability to withstand an SO2 mass concentration of 300g/L at pH 3.2. Moreover, S. cerevisiae YBB-47 displayed a rapid gas production rate and strong ethanol productivity. whereas P. kudriavzevii YBB-33 exhibited excellent alcohol tolerance. Furthermore, this systematic classification and characterization of coffee bean yeast strains from the Sidamo region can potentially uncover additional yeasts that offer high-quality resources for industrial-scale coffee bean production.

Accelerated corrosion tests of a contact pair austenitic stainless steel – titanium alloy

The results of accelerated corrosion tests of a pair of austenitic stainless steel — titanium alloy under conditions of elevated temperatures and high concentrations of corrosive agents are presented, conditions for the developing the mechanism of local corrosion being the same. The proposed approach included provoking the appearance of microstress concentrators by three-point loading of test samples with subsequent forced development of local types of corrosion through simultaneous exposure to an increased concentration of corrosive agents and temperatures at a fixed exposure in an autoclave. The results of modeling the corrosion process in a titanium alloy being in contact with stainless steel are assessed proceeding from the data obtained from metallographic studies of the state of surface layers of the metal and the morphology of corrosion products on prepared sections of the surface of templates cut from the samples under study. We considred a pair of steel 08Kh18N10T — titanium alloy VT-5. It is shown that the contact of samples under conditions of accelerated corrosion tests does not lead to a significant development of local types of corrosion of the titanium alloy. On the contrary, analysis of the state of the surface layers of the samples of stainless steel revealed the presence of deep corrosion pits, triggering the intergranular corrosion. In this case, corrosion of austenitic steel, both in the presence and in the absence of contact with titanium, proceeded in three stages: the initiation and fusion of pitting; formation of knife corrosion ulcers; propagation of intergranular cracks into the depth of steel. The proposed methodology of corrosion testing can be used to predict the possible nature of the development of metal corrosion under operating conditions that form local zones of static stresses in structural materials, and for prompt response to extend the design life of the equipment at thermal and nuclear power facilities.

Impact of oxygen scavenger, temperature, and packaging materials on freshness quality of packaged green teas during storage

AbstractGreen tea is renowned for its exceptional freshness; nevertheless, preserving its freshness poses a formidable challenge during storage due to its susceptibility to environmental factors. However, the effect of storage factors on freshness quality of green tea remains unclear, particularly with a lack of research studies regarding aroma quality and associated volatiles. In this study, we investigated the effects of oxygen scavenger, temperature, and packaging materials on freshness quality of packaged green teas during storage. The sensory freshness and corresponding volatile metabolites of the samples were investigated; the sensory‐chemical changes among packaged green teas during storage under different treatments were further explored. The freshness preservation in packaged green teas can be effectively achieved through the implementation of low‐temperature storage, packaging with oxygen scavenger and utilizing packaging with minimal oxygen permeability. A total of 151 volatile compounds were detected in all samples, among which 104 volatiles were identified as key contributors for distinguishing sample groups under 3 different treatments. The presence of volatiles with green, spicy, minty, and vegetable notes was found to be positively correlated with high freshness quality observed in packaged green tea. Conversely, an increase in volatiles characterized by fruity, sweet, fatty, and alkane notes was associated with the freshness deterioration. The volatiles changes that lead to freshness deterioration occurred especially under conditions of elevated temperature and increased oxygen levels, predominantly involving fat degradation, lipid oxidation, the Maillard reaction, carotenoids degradation, and dehydration reactions. The findings provide a theoretical foundation for the advancement of storage technology in packaged green teas.