Effect Of High Temperature Research Articles

Study on Foaming Agent Foam Composite Index (FCI) Correlation with High Temperature and High Pressure for Unconventional Oil and Gas Reservoirs

In the process of unconventional oil and gas reservoir exploitation, it is difficult to reduce drilling fluid lost in natural fractures, enhance the CO2 displacement effect and reduce foam drainage gas recovery costs. In most cases, foaming agents can solve these problems in a low-cost way in a short period of time. Foaming agent screening and evaluation is the key to this technology. However, there are few experimental tests used in the evaluation of foaming agent properties that match the actual unconventional oil or gas well conditions of high temperature and high pressure. Using the actual temperature and pressure conditions of a wellbore, the foaming capacity and half-life of two common foaming agents were systematically evaluated by using the high-temperature and high-pressure visual foam properties evaluation device (UPMX-500), in which the foaming agent’s volume concentration was 3‰ in a simulated formation water with a pH of 6 and salinity of 9 × 104 mg/L. The high-temperature (40 °C, 60 °C, 80 °C, 100 °C) and high-pressure (0.1 MPa, 6.0 MPa, 8.0 MPa, 10.0 MPa) effect on the foaming capacity and half-life was analyzed. Binary linear regression of pressure and temperature was carried out, taking the foam composite index as the target and using a formula with high correlation. The results showed that the foam composite index (FCI) of the two foaming agents was positively correlated with pressure and temperature. The correlation of UT-7 was FCI = 64.1196T + 735.713p − 2066.2, the correlation of HY-3K was FCI = 62.5523T + 7220.391p − 2415.6, and the coefficients of determination were 0.9799 and 0.9895, respectively, with an error of less than 10%. This correlation equation can provide a reference for accurately predicting the foaming capacity of foaming agents under high-temperature and high-pressure conditions and can also be used to optimize foaming agents or to qualitatively evaluate results for the efficient exploitation of unconventional oil and gas reservoirs.

Influences of high temperature and humidity on vegetable-tanned leather

Leather artifacts, mainly composed of collagen and tanning agents, possess significant historical importance. However, external factors could lead to the aging of such artifacts during preservation. Therefore, it is crucial to examine the impact of various factors on leather aging. In order to know the effects of high temperature and humidity conditions on the changes of leather artifacts, the traditional vegetable tanning agents (chestnut, tara, quebracho, and mimosa) were used to tan the pickled sheepskins to prepare leather artifact model samples. The leather artifact model samples were aged for 0, 2, 4, 8, 16, and 32 days at 80°C and 40–80 % relative humidity (RH). The changes in appearance, structure and thermal stability of the vegetable-tanned leather samples under the synergistic impact of temperature and RH were analyzed using total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), chromatography, and scanning electron microscopy (SEM). The thermal degradation of the samples before and after being tanned with vegetable tanning agents was analyzed using thermal gravimetric analyzer (TGA) analysis. Furthermore, the shrinkage temperature (Ts), tensile strength and elongation at break of the samples were investigated during different aging periods. The study aims to provide valuable insights into the stability of leather artifacts during long-term storage, as well as guidance for their restoration and conservation.

ASSESSMENT OF THE CORROSION-MECHANICAL PROPERTIES OF THE LEFT MATERIALS AND FORECASTING THE SAFETY OF GAS TURBINE PARTS

Purpose. Determination of the possibility of using the temperature-time parametric dependences of Miller-Larson, Manson-Haferd, and Sherby-Dorn for long-term prediction of the strength characteristics of parts subjected to oxidation and high-temperature sulfide-oxidation effects. Research methods. Long-term strength studies were performed on samples of ВЖЛ-12У and ЗМІ-3У alloys in synthetic ash (66.2 % Na2SO4, 20.4 % Fe2O3, 8.3 % NiO, 3.3 % CaO, 1.8 % V2O5) and an oxidizing environment at temperatures of 800 °C and 850 °C. The Miller-Larson, Manson-Haferd, and Sherby-Dorn temperature-time parametric dependences were used to predict the tensile strength of materials in an oxidizing and corrosive environment. The microstructure of the samples was studied using an optical microscope MIM-8M. Results. The results obtained indicate a high level of corrosion resistance of ЗМІ-3У samples at 800 °C and 850 °C and the possibility of determining the tensile strength of the material for a period of 1000, 5000, and 10000 hours by the calculation method. Tests of ВЖЛ-12У alloy samples in synthetic ash showed a discrepancy between the experimental time to fracture and the calculated value, regardless of the parametric method, which indicates a direct dependence of long-term strength on the degree of corrosion damage to the surface of the samples. Scientific novelty. The possibility of using the Miller-Larson, Manson-Haferd, and Sherby-Dorn temperature-time parametric dependences for long-term prediction of the strength characteristics of parts in an oxidizing environment has been confirmed. In a sulfide-oxide environment, the use of parametric methods to determine strength characteristics for up to 10,000 hours is possible only for corrosion-resistant alloys. Intensive corrosion damage to ВЖЛ-12У alloy leads to accelerated deformation, which limits the use of temperature and time dependencies for effective prediction of the time of failure of parts made of this material. Practical value. Determining a reliable method for predicting the strength characteristics of heat-resistant alloys in an oxidizing and corrosive environment allows reducing the time and financial costs of conducting lengthy field studies.

Maize migration mitigates the negative impact of climate change on China’s maize yield

Crop migration as an adaptation to modulate climate change’s impact on crop yields presents both benefits and risks. We explored how maize migration in China modulates yield responses to climate change and quantified the potential economic benefits of maize migration as an adaptation strategy. We employed a panel data model to identify and measure the factors driving the relocation of maize area, linear regression to quantify the effects of maize migration on climate exposure and irrigated area, and an econometric model to estimate the effects of maize migration on yield. The results show that rise in temperature has a significant negative effect on maize area and that precipitation has a significant positive effect. The migration of maize area is driven by socio-economic factors including agricultural gross domestic product, power of farming machines, and fertilizer input. Moreover, expanded irrigation reduces the adverse effects of high temperatures on maize yield, thereby influencing adaptive crop migrations. The beneficial effects of maize migration are primarily achieved by reducing the adverse effects of extreme heat and strengthening the positive effects of irrigation. However, the extent of this adaptation is jointly affected by agricultural policies, irrigation infrastructure, and economic factors. Current market-oriented agricultural policies may be effective in guiding spatial shifts in maize distribution to align with climate-driven changes, potentially decreasing the vulnerability of China’s maize yield to the impact of climate change. China’s food security policies need to consider climate-driven spatial shifts in crop cultivation and enhance food subsidy policies to highlight the benefits of investment in climate change adaptation, such as adjusting cropping acreage and irrigation to farmers in North China.

Numerical and experimental investigation of the gyroid heat exchanger

This paper presents a study of a novel type of heat exchanger (HE) whose core is built based on a Triply Periodic Minimal Surface structure. The core of this exchanger is built as a periodic structure based on a gyroid-type lattice and is manufactured by laser powder-bed fusion technology. This solution is distinguished not only by an exceptionally favorable ratio of the heat exchange surface area to the volume occupied but also by a unique geometry that additionally turbulates the flow and intensifies the heat exchange process. This article contains the results of numerical analyses of the entire exchanger under different operating conditions and the results of analyses of small fragments of the core filled with cells of different sizes. Numerical analyzes of the lattice-type exchanger are performed on the basis of the experimentally validated numerical model. The objective of the study is to determine the performance of the gyroid HE under different operational conditions and select the best elementary cell size per exchanger core for the assumed operating conditions. The printed HE was compared with a plate HE that was 30% larger, although the lattice one managed to achieve 10.5% higher values in on average Number of Transfer Units (NTU) and on average 5% higher temperature effectiveness (TE) in the studied range of flow parameters.

Photopolymerization-based 4D-printing of shape-memory materials containing high-performance polymers

High-performance aromatic heterochain polymers are engineering thermoplastics with exceptional mechanical and thermal properties that have attracted great interest in various areas ranging from aerospace to biomedicine. However, there have been a number of difficulties to 3D-print materials based on such polymers with new promising performance characteristics. Herein, a number of new photosensitive compositions (PSCs) based on high-performance polyetherimide (PEI) or polysulfone (PSU), reactive functional monomer (N,N-dimethylacrylamide) and oligomer (bisphenol A ethoxylate diacrylate) has been developed. It has been shown that the use of the developed PSCs allows the formation of 3D-structures with high printing resolution by LCD 3D-printing. Subsequent thermal post-curing of 3D-printed green-state samples at 250°С for 1 h led to the fabrication of materials with the highest tensile strength (up to 41.9 ± 3.1 MPa), glass transition temperature (141 °C) and thermal stability (above 350 °C). In addition, 3D-printed structures demonstrate high-temperature shape memory effect with shape fixity ratio > 99% and shape recovery ratio up to 97.1%.

Benefits and barriers to the adoption of climate‐smart agriculture practices in West Africa: A systematic review

AbstractClimate‐smart agriculture (CSA) serves as a credible mechanism to simultaneously address food security, climate change, and agricultural productivity. Despite the widespread adoption of CSA approaches across West Africa, many countries have still not been able to resolve the problems of food insecurity and rural poverty. This systematic review evaluates published evidence on the types of CSA practices, the determinants and benefits of adoption, and the barriers confronting the adoption of CSA practices across West Africa, following the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses statement checklist. Articles published in English from January 2010 to March 2023 investigating the benefits of and barriers to the adoption of CSA practices in West Africa were retrieved from ScienceDirect, Web of Science, and Scopus databases. The methodological quality of studies was assessed using Joanna Briggs Institute critical appraisal tools for use in systematic reviews. The themes emerging from the articles were extracted, and a summary was provided to illustrate each theme. After applying the eligibility criteria, 12 articles were included in the final review. The studies reviewed revealed that farmers used more knowledge‐, water‐, carbon‐, and nitrogen‐smart practices, compared to weather‐ and energy‐smart practices. Across the reviewed papers, factors such as the education level of farmers, age, gender, household size, membership of a social group, agricultural extension services, and access to credit/financial resources influenced CSA adoption. The reviewed studies identified that farmers who used CSA practices reported benefits such as improved soil fertility, higher yield, improved household income, climate resilience (such as overcoming the effects of drought and extreme temperatures), and food security. Some farmers adopted CSA practices to reduce the effect of droughts and high temperatures on their crops, and thus increase their resilience to climate variability and change. However, farmers’ adoption is confronted with challenges related to the technicality of some CSA practices, high cost of labor for CSA implementation, lack of credit and government support, limited access to weather and climate information, limited information about CSA options, high illiteracy level of smallholder farmers, and incompatibility of some practices with farmers’ crop of interest. Our findings show that most CSA practices in the studies we reviewed are not well targeted to meet farmers’ crop of interest, and that governments should provide more practical training to enhance farmers’ understanding of CSA practices, especially those related to weather‐ and energy‐smart initiatives. There should also be more robust financial and institutional support to improve the adoption and usage of CSA practices at all levels. Additionally, socio‐cultural factors such as values, customs, and beliefs should be properly integrated into CSA plans as they influence the adoption of CSA practices.

Investigation of the structural and phase state of detonation multilayer coatings based on NiCr/NiCr–Al2O3/Al2O3 during high-temperature oxidation

This paper presents a study of the structural and phase state of detonation multilayer coatings under hightemperature oxidation. The experiment aimed to find out the effect of high temperatures on the structuralphase state of coatings and their effectiveness in preventing oxidative processes. As a result of the research, it was found that after high-temperature tests, protective phases such as NiCr2O4, Al2O3, and Cr2O3 are formed in the structure of multilayer coatings. These phases were identified to play a key role in preventing intensive oxidation of the metal surface. It was determined that NiCr2O4 provides stability to the metal layer, and Al2O3 and Cr2O3 are effective barriers protecting the surface from aggressive environmental influences. It is important to note that no signs of fracture or detachment were found in the multilayer coatings during the entire experiment. After the first cycle, the uncoated sample experienced peeling of its oxide film, resulting in a significant loss of mass. It was determined that the uncoated steel experiences significantly higher mass loss, indicating a faster formation of oxides on its surface. The experimental data confirm the effectiveness of coatings in protecting against oxidative processes at high temperatures, thereby maintaining the stability and durability of the material under extreme thermal influences.

Investigating the impact of weather on stroke in summer.

The objective of this study is to explore how changes in weather contribute to an increase in hospital admissions for stroke in summer. We collected 96,509 cases of stroke hospitalization data in Tianjin from 2016 to 2022 summer, along with corresponding meteorological data. The generalized additive model and distributed lag nonlinear model were used to analyze the lag and cumulative effects of temperature on stroke hospitalization. The research results show both the cold effect and the heat effect in summer would increase the risk of hospitalization. The effect of daily maximum temperature on stroke hospitalization was immediate when the temperature was higher, and delayed when the temperature was lower. However, the risk of stroke hospitalization increased more significantly with increasing temperature than with decreasing temperature. In the presence of one or more of the following three weather changes: sharp temperature increase, sharp temperature decrease, continuous high temperature, the daily number of stroke inpatients were higher than the average in the same period. 83% of the Inpatient-heavy events within the study period were caused by a combination of dramatic temperature changes and continuous high temperatures. In 48% of Inpatient-heavy events, continuous high temperature weather above 30℃ for at least 4 consecutive days were observed. And 55% of high temperature weather was accompanied by high humidity. When the daily relative humidity was greater than 70% and the daily maximum temperature was between 26 and 28℃ or more than 34℃, or the daily maximum temperature changes over 10℃ within 48h, the number of daily inpatients was more than 1.2 times of the average daily inpatients. More attention should be paid to the combined effects of continuous high temperature and sudden temperature changes in summer stroke prevention.

Research on strength and microscopic characteristics of lime-activated fly ash-slag solidified sludge under high temperature effect.

To explore the reaction mechanism of sludge, slag, lime, and fly ash in high temperature environments, the unconfined compressive strength (UCS) test was hereby implemented to study the effect on curing age, curing temperature, slag content and fly ash content about the strength of sludge. Scanning electron microscopy (SEM) was used to observe the microscopic composition of the substance, and X-ray diffraction (XRD) was used to analyze the mineral composition at the micro level to further disclose its reinforcement mechanism. The experimental results demonstrate the difference in the strength measured by different dosage of curing agent, and results indicate that the strength of high temperature curing sample was obviously higher than that of low temperature curing sample. When the curing temperature rises, the pozzolanic reaction and hydration reaction between materials are accelerated, and a certain amount of gel products are produced, playing a precipitation and bonding role between particles. The 28 days and 90 days strengths of the sludge samples with 20% fly ash and 80% slag dosing at 40°C were 1139 KPa and 1194 KPa, which were 1.4 and 1.1 times of that of pure cement solidified sludge. At 60°C, the strength of 14 days, 28 days and 90 days were 802 KPa, 1298 KPa and 1363 KPa, which were 1.1, 1.5 and 1.3 times of that of pure cement solidified sludge. Under the influence of an alkaline environment, the silicon-aluminum grid structure was interconnected into a denser network structure, and the compressive strength of lime-activated fly ash-slag was thus continuously enhanced. Affected by the high temperature, lime-activated fly ash-slag solidified sludge could significantly improve the middle and late strength of the sample. The research showed that the new solidification material can replace partly the concrete curing agent, thereby alleviating the carbon emission and environmental pollution problems arising from cement solidified sludge.

Influence of Oxidation Temperature on the Regeneration of a Commercial Pt-Sn/Al2O3 Propane Dehydrogenation Catalyst

In the propane dehydrogenation process, the structure and catalytic performance stability of the catalyst are determined by its regeneration process, which includes oxidation of coke and oxychlorination to redisperse the supported metal particles. A commercial Pt-Sn catalyst was used in this work to investigate the impact of oxidation temperature on oxychlorination performance. The catalysts after oxidation and oxychlorination were characterized by H2-TPR, CO-DRIFTS, HAADF-STEM, XPS, and CO chemisorption. It was found that mild sintering of Pt occurred during oxidation in the temperature range of 550–650 °C, and the catalyst could be fully restored in the subsequent oxychlorination treatment. Upon oxidation of the catalyst at 700 °C, a severe aggregation of Pt and SnOx could be observed, and the catalyst could not be fully regenerated under the given oxychlorination conditions. However, PDH catalyst deactivation caused by sintering is not irreversible. By tailoring the oxychlorination conditions, the detrimental effect of high oxidation temperature on regeneration could be ruled out. During the oxidation and oxychlorination treatment, the metal tends to migrate to anchor on sites with stronger metal–support interaction, which was helpful for enhancing the catalytic activity.

Structural performance of steel reinforced concrete L-shaped columns in high temperature

This paper presented structural performance of steel reinforced concrete (SRC) L-shaped columns under high temperature and axial load coupling effects. Considering the influence of the axial load ratio (0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8), eccentricity (25, 50, 75 and 100 mm), concrete strength (40, 50, 60 and 70 MPa), calculation length (500, 1000, 1500 and 2000 mm), the SRC L-shaped columns were tested and analyzed in high temperature conditions. The results demonstrated that: (1) Concrete surface of all specimens was grayish white with many cracks. With the increasing axial load ratio, the number of cracks decreased and crack width increased. (2) The fire resistance decreased by 1.3–15.1 %, 6.1–14.9 %, and 3.8–7.1 % respectively, with increasing axial load ratio, eccentricity, calculation length; the fire resistance increased by 0.7–5.3 % with increasing concrete strength. (3) Axial displacement trend first increased gradually because of the thermal expansion of concrete, and decreased gradually after reaching the maximum axial expansion deformation. With increasing axial load ratio, the maximum axial expansion deformation decreased by 42.4–60.2 %, the time of displacement to reach the maximum expansion deformation decreased by 29.7–57.0 %, and the time of displacement to reach 0 mm decreased by 272.7–366.2 %. Finally, the calculation method for displacement and maximum bearing capacity in high temperature was proposed according to principle of virtual work, which served as a guide for fire evaluation of SRC L-shaped columns.

Adaptation and Mitigation of High Temperature Stress in Tomato

Tomato (Solanum lycopersicum L.) holds considerable economic significance as a vegetable crop globally, ranking second in both cultivated area and production worldwide. Optimal growth conditions for tomatoes typically fall within the temperature range of 25°C - 30°C during the day and around 20°C at night. However, deviations from these thresholds can lead to irreversible damage to plant growth and development. To counteract the adverse effects of high temperatures, tomato plants employ various adaptive mechanisms involving physiological, morphological, anatomical, and biochemical changes. Efforts to enhance thermotolerance in tomatoes encompass a range of strategies, including agronomic practices, the application of growth regulators and fertilizers to induce acclimation responses, breeding programs aimed at developing heat-resistant cultivars, and genetic modification. Various other methods are also employed to mitigate the impacts of high-temperature stress on plants, such as pretreating seeds with low concentrations of inorganic salts, applying osmoprotectants and signaling molecules through foliar sprays, and subjecting plants to preconditioning measures. These approaches facilitate stress avoidance and foster the development of inherent mechanisms for high-temperature tolerance in plants.

Study on the Health Effect of Temperature on Cardiovascular and Cerebrovascular Diseases in Haikou City

Research on the impact of temperature in tropical regions on the risk of cardiovascular and cerebrovascular diseases was limited. The aim of the study was to investigate this topic using Haikou, a tropical city, as the research area. Outpatient data on cardiovascular and cerebrovascular diseases (CVD and CeVD) from Hainan Provincial People’s Hospital during 2016–2018 (total of 77,820) and meteorological and air-quality data were used to establish a distributed-lag nonlinear model (DLNM) based on the nested generalized addition model (GAM) of meteorological elements. The results revealed the impact on the risk of CVD and CeVD was mainly due to the cold effect, which significantly lagged behind. The thermal effect had a strong impact on the onset of CVD and CeVD on the day of high temperature. Males were easily affected by low temperatures, while females were the opposite. The lag period of the working-age group affected by low temperatures was longer and greater than that of the elderly group. The high-temperature effect only had an impact on the working-age group. The lag effect of low temperatures on the risk of hypertension was the greatest. These results can provide technical support for carrying out meteorological forecasting, warning, and services for individuals with CVD and CeVD, suggesting attaching importance to health protection for special populations.

Research on the residual compressive properties of concrete with preload after sustained high temperatures

The containment vessel of nuclear power plants, concrete structures near the furnaces and roller lines, and chimneys, are exposed to high temperatures (120 °C to 350 °C) for long term. Research on the compressive properties of concrete after short-term high temperatures (usually within 3 h) has been widely conducted, while that of concrete after sustained high temperatures is scarce. In this research, the effects of temperature (120 °C to 350 °C), heating duration (3 h to 32 h) and initial stress level (0.2 to 0.6, ratio of initial applied stress to compressive strength at room temperature) on the failure mode, compressive strength, peak strain and stress-strain relationship of concrete after sustained high temperatures were studied. The results show that with increasing temperature and heating duration, concrete compressive strength gradually decreases, while concrete peak strain gradually increases. At heating duration of 24 h, the properties of concrete have basically stabilised. Preloading helps the concrete to resist the adverse effects of high temperatures by inhibiting the dehydration of cement matrix and the cracking of interfacial transition zone. For concrete with preload, transient thermal strain and short-term creep at high temperatures could not be recovered after cooling, which causes a significant increase in the peak strain of concrete. A compressive stress-strain model for concrete with preload after sustained high temperatures was developed, which consists of pre-creep ascending segment, creep segment, post-creep ascending segment and descending segment. Comparison of the prediction results with the test results proves that the model has high accuracy.

High temperature exposure causes sexual dimorphism in immune responses against largemouth bass ranavirus (LMBV) in Micropterus salmoides

Largemouth bass (Micropterus salmoides) is an important freshwater fish species in aquaculture. Largemouth bass ranavirus (LMBV) infection at high temperature results in a considerably higher mortality rate in females than that in males. This study compared the spleen transcriptomes and analyzed the impact of sexual dimorphism on immunity and metabolism of largemouth bass infected with LMBV at high temperatures to gain a comprehensive understanding of the sex-based differences in immunity and metabolism of this species. (1) Compared with the ambient temperature group (W20), the high temperature group (W30) exhibited multiple significant differences in metabolic and immune terms, with several immunity-related pathways, including phosphatidylinositol 3-kinase-protein kinase B (PI3K-Akt) signaling pathway. Most identified pathways were associated with the estrogen signaling pathway, which also differed significantly. (2) Differences in glycolipid metabolism, immunity, and the endocrine and complex adaptive systems were distinctly different between male groups (W20M vs. W30M), whereas the female groups (W20F vs. W30F) were not significantly different. The male groups had a significantly higher number of enriched immunity-related KEGG pathways and differentially expressed genes (DEGs) and pathways related to the estrogen signaling pathway. (3) When comparing male and female samples infected with LMBV at the same temperature, no significant difference was observed between the ambient temperature groups (W20F vs. W20M). The high-temperature groups (W30F vs. W30M) had 18 immunity-related pathways among the top 25 enriched KEGG pathways, and gene expression correlation analysis of the DEGs showed positive correlations. This study demonstrates that the combined effects of high temperature and LMBV affect multiple metabolic and immune pathways in largemouth bass, thereby modulating immune responses by regulating the estrogen signaling pathway and influencing the expression of estrogen and its receptors. Under high-temperature conditions, male fish may have stronger estrogen signaling pathway-associated immune responses, which regulate immune pathways, including antigen processing and presentation, complement system, and phagocytosis. Consequently, males may have higher disease resistance than that of females. Our result contribute to mono-sex breeding and antiviral drug therapies available in largemouth bass, thereby markedly improving breeding efficiency.

Post-fire residual mechanical and microstructural properties of waste basalt and glass powder-based geopolymer mortars

The wastes that arise during the production process of the products required by the industry create environmental problems. In recent years, the activation of such wastes with alkaline activators has provided environmentally friendly and sustainable solutions. Different mixture designs have been realized for the production of geopolymer composites with basalt and glass powder waste. This study deals with the changes in the mechanical properties and microstructure of geopolymer mortars containing basalt powder (BP) and glass powder (GP) with the post-fire air curing effect. Geopolymer mixtures were prepared by using basalt powder and glass powder at 0 %, 25 %, 50 %, 75 %, and 100 % proportions. After casting and vibrating, the mortars were cured at 90 °C for 24 h. Flexural and compressive strength tests have been conducted on the specimens at the age of 1, 28, and 90 days. Additionally, the tests were applied to the heated specimens (400 °C, 600 °C, and 800 °C) after 1, 28, and 90 days from the heating process, separately. The effect of high temperature on mechanical, physical, and microstructural properties is examined comparatively. In addition, SEM/EDX analyses were performed on selected samples. As a result, the post-fire behavior of geopolymers is changeable with the precursor type. The compressive strength of the mortars containing %75 basalt and %25 glass powder had the best post-fire performance of all the mortars. The compressive strength of these mortars significantly increased from 1 day to 90 days after being subjection to high temperatures up to 800 °C.

Aggregation-Growth and Densification Behavior of Titanium Particles in Molten Mg-MgCl2 System.

In this work, the preparation of titanium sponge by magnesium thermal method is regarded as the liquid-phase sintering process of titanium, and powder-metallurgy sintering technology is utilized to simulate the aggregation-growth and densification behavior of titanium particles in a high-temperature liquid medium (the molten Mg-MgCl2 system). It was found that compared with MgCl2, Mg has better high-temperature wettability and reduction effect, which promotes titanium particles to form a sponge titanium skeleton at lower temperature. The aggregation degree of titanium particles and the densification degree of a sponge titanium skeleton can be improved by increasing the temperature and the relative content of Mg in the melting medium. The kinetics study shows that with the increase in temperature, the porosity of the titanium particle aggregates and the sponge titanium skeleton decreases, and their density growth rate increases. With the extension of time, the aggregation degree of titanium particles and the densification degree of sponge titanium gradually increase. This work provides a theoretical reference for controlling the density of titanium sponge in industry.

Mechanical failure analysis of drill string aggravated by stuck pipe after high-temperature melting-cutting operations

High-temperature melt cutting is an important technology for fast cutting and unjamming of downhole jammed tubular rods, but due to the well depth and mud environment, it cannot completely cut through the large wall thickness tubular rods such as weighted drill pipe, and it needs to be damaged by external load applied by drilling rig. The shape of the drill pipe kerf after the melt cutting operation is not the same, so the size of the applied external load needs to be further investigated. To address this problem, firstly, this paper establishes the Johnson-Cook ontology and failure model of S135 steel grade drilling tools based on the high temperature tensile test; secondly, according to the characteristics of the weighted drill pipe melt-cutting notch, a finite element model for mechanical damage failure analysis of weighted drill pipe with melt-cutting notch is established, and the reliability of the model is verified; lastly, the influence of high temperature and different notch characteristics (melt-cutting depth, circumferential cutting angle, Finally, the effects of high temperature and different notch characteristics (depth of cut, circumferential cutting angle, number of perforations) on the mechanical failure capacity of weighted drill pipe with fusion notch are analysed. The results show that the errors of the maximum stresses and strains of the samples obtained from the tensile fracture simulations at 20 °C and 400 °C and the maximum stresses and fracture strains obtained from the experiments are within 9 %, which verifies the accuracy of the model. Tensile loading was more effective than compressive loading in destroying the drill pipe; the change in loading speed had a small effect of 4.1 % on the tensile force required to destroy the drill pipe. The damage load of the drill pipe and the pressure acting on the cross-section of the fusion cut decreases with the increase of the fusion cutting depth; the damage load required decreases with the increase of the circumferential cutting angle and the number of openings, but the pressure acting on the cross-section of the fusion cut does not decrease. The softening effect of high temperature on the drill pipe is very obvious, and the tensile capacity of the drill pipe is attenuated by 80.6 % at a temperature of 800 °C. The research work can improve the operation process of cutting and unjamming thick-walled drilling tools in deep wells and guide the field operation to achieve the purpose of rapid unjamming.

Microstructural and thermal characterization of polyethylene fiber-reinforced geopolymer composites

The use of geopolymer (GPL) as a non-combustible mineral matrix for fiber-reinforced composites and environmentally acceptable building materials is growing. When fibers are added to GPL, its brittle behavior changes to ductile or quasi-ductile, producing fiber-reinforced GPL composites that function well. The novelty in the present research involves analyzing the effects of high temperature and polyethylene (PE) fiber content on mechanical and microstructural properties to determine how PE fiber reinforcement influences the thermal performance of GPL composites. In this study, the main objective is to assess various GPL mixes to investigate how the inclusion of PE fiber and exposure temperature affect the material's performance after being subjected to elevated temperatures. These included compression tests, flexural tests, scanning electron microscopy, bubble parameter testing, thermogravimetric and differential thermal analysis, and mass loss measurement. The PE fiber concentrations varied between 0 % and 1.5 % by volume of the mix, and the exposure temperatures were established at 25, 200, 400, 600, and 800 °C. A two-way ANOVA analysis was performed to examine the significance of variation in the results due to the addition of PE fibers and elevated temperatures. According to the results, the GPL mortar observed a significant mass loss as the temperature rose from 25 °C to 250 °C. But from 250 °C to 710 °C, there was very little mass loss, and from 710 °C to 800 °C, there was no more loss. The GPL mortar thickened as the temperature increased, but more pores and cracks appeared. At 25 °C, adding PE fibers to GPL improved compressive strength by 16.2 %–35.55 % for 0.25 %–1.50 % dosages. Over 1.0 % led to a significant reduction because of uneven distribution, compromising homogeneity, and increasing porosity. The melted fiber defects had a minor effect on the strength of the mortar, even if the PE fiber broke down at higher temperatures. With an ideal fiber content of 1.50 % below 200 °C, PE fibers greatly enhanced the flexural properties of GPL mortar, resulting in a 6.30 %–58.00 % increase in flexural strength. Conclusively, incorporating PE fibers improves the flexural strength of GPL up to 200 °C, but beyond this temperature, there is a significant decline of the flexural strength, showing the fibers' effectiveness up to a specific temperature.