Effect Of High Temperature Exposure Research Articles

Anti-corrosion behavior of magnesium phosphate (Mg–P) coatings after exposure to elevated temperatures

In this study, Mg–P coatings, prepared on steel alloy substrates, were exposed to temperature from 25 °C to 900 °C. The effects of high temperature exposure and the salt spray test on the anti-corrosion ability of Mg–P coating were investigated in detailed. The results show that the corrosion resistance of coatings decreases continuously from 25 °C to 700 °C, then increases at 900 °C of exposure. However, the corrosion resistance of coatings after 2000h salt spray test was significantly improved. In particular, the corrosion rate of the coating is only one-ninth that of the coating before the salt spray test when the temperature is 900 °C. Furthermore, the microscopic characterization test revealed that a dense oxide layer form between the steel alloy substrate and the coating when temperature exceed 400 °C. Besides the crystal phase transition and oxide layer, the synergistic effect of the secondary reaction of the raw material is the key factor to ensure that the coating still has good corrosion resistance at a high temperature.

Desain Mini Primer STR Lokus TH01 dan D21S11 untuk Amplifikasi DNA Darah Terpapar Suhu Tinggi

DNA identification has an important role in forensics to investigate a case. However, the problem that is often encountered is that the DNA found is difficult to analyze because the amount is relatively small and degraded. An alternative used in DNA examination is to design mini primers for amplification. Mini primers can produce DNA profiles even in samples that have very low quantity and quality. Therefore, this study aims to determine the effectiveness of mini primers for amplification of TH01 and D21S11 loci in DNA exposed to high temperatures. In addition, to determine the effect of high temperature exposure on DNA quality and quantity. The samples used were 3 ml of human blood treated with 100, 150, and 200ºC for 10, 20, and 30 minutes. The method used was PCR amplification using mini primers TH01 and D21S11 loci. Quantity data were analyzed by a parametric test using the Two Way Anova method. Meanwhile, DNA quality was tested by agarose gel electrophoresis. The results showed that temperature treatment affected the quantity and quality of DNA. The TH01 locus in DNA samples treated with high temperature can be amplified using primer pairs MP1FTH01 and MP1RTH01. At the D21S11 locus, the use of primers 1 and 2 can be combined to identify DNA samples with high temperature treatment

Stress-strain models for FRP-confined thermally damaged concrete

Fiber-reinforced polymer (FRP) jackets have been increasingly used for the strengthening and confinement of concrete columns. Despite extensive research efforts yielding various concrete confinement models that can be broadly classified as design- and analysis-oriented, an accurate model is lacking for the design of FRP-strengthened thermally damaged concrete columns. This paper presents a comprehensive review of existing experimental studies on FRP-confined thermally damaged concrete columns and collects a large database of the corresponding test results. Then, a theoretical analysis is conducted to evaluate the accuracy and reliability of typical concrete confinement models (originally proposed for undamaged concrete) through extensive comparisons with the corresponding test data. The analytical findings have revealed that none of the existing models can accurately predict the compressive behavior of FRP-confined thermally damaged concrete. Two novel confinement models, design-oriented and analysis-oriented, are proposed for FRP-confined thermally damaged concrete. These novel models have appropriately considered the effects of high-temperature exposure on the confining pressure of FRP jackets and the lateral deformation characteristics of thermally damaged concrete. The proposed models are then validated by comparing the model predictions with the corresponding test results, indicating that these models can accurately predict the compressive stress-strain responses and dilation behavior of FRP-confined thermally damaged concrete.

Effect of High Temperature Exposure on Bond Properties of Steel Deformed Rebar Embedded in Self-Consolidating Concrete Containing Copper Slag as Fine Aggregate

Effect of High Temperature Exposure on Bond Properties of Steel Deformed Rebar Embedded in Self-Consolidating Concrete Containing Copper Slag as Fine Aggregate

Microstructure evolution and properties of red mud/slag-based cenosphere/geopolymer foam exposed to high temperatures

In this study, a type of red mud/slag-based cenospheres/geopolymer foam was directly fabricated using the direct foaming method at room temperature. The effects of high-temperature exposure (700–1100 °C) on the phase evolution, pore structure, and properties of the foams were investigated. The results showed that the untreated foam was amorphous structure. The porosity of the foams increased from 36.4 ± 0.6% (1 wt%) to 71.9 ± 0.1% (5 wt%) with the addition of H2O2. The compressive strength of the foams was 1.20–18.15 MPa, which was attributed to the good bond between the cenospheres and red mud/slag-based geopolymer matrix, the fractured spheres, and the crack deflection. After this high-temperature exposure, the foam crystallized mainly into the leucite and mullite phases. The density and compressive strength of the foams decreased as the exposure temperature increased. The thermal conductivity of the foams reached the lowest value of 0.169 W/(m⋅K) and 0.108 W/(m⋅K) with 5 wt% H2O2 before and after the exposure, respectively. These foams have demonstrated good potential for application in the building insulation field.

Effect of high temperature exposure on microstructure, mechanical and tribological properties of cold sprayed NiCoCrAlTaY coatings

NiCoCrAlTaY coating is widely used in high temperature oxidation resistance, gas erosion protection and gas path sealing of hot-end parts of aeroengines and gas turbines. In this study, NiCoCrAlTaY coatings were prepared on cobalt-based superalloy substrates by high pressure cold spray technology. The microstructure, mechanical property and tribological behaviors of the coatings before and after thermal exposure at 1050 °C were systemically studied. The results showed that NiCoCrAlTaY coatings with very dense structure could be obtained by high-pressure cold spraying with nitrogen as carrier gas. The coating remained completely intimate with the substrate without any cracking and spalling after thermal exposure at 1050 °C for 500 h. Due to elemental diffusion at high temperatures, the coating formed a four-layer structure, including alumina film on the surface, β-NiAl phase depletion layer near the surface, intermediate layer containing β-NiAl phase and β-NiAl phase depletion layer near the substrate. With the prolongation of thermal exposure at 1050 °C, the thicknesses of β-NiAl phase depletion layers both near the surface and the substrate increased. The thickness and content of the intermediate β-NiAl phase layer decreased gradually during thermal exposure. Besides, the average hardness values of the coating rapidly decreased by about 30 % after thermal exposure at 1050 °C for 5 h. In particular, the hardness of the β-NiAl phase depletion layer near the surface substrate was lower than that of the intermediate area containing β-NiAl phase. Due to the microstructure and hardness evolution, the wear resistance of the coating decreased significantly after thermal exposure. The friction coefficient of the coating increased from 0.2 to 0.5, and the volume wear rate of the thermally exposed coating was about 4.5 times higher than that of the as-sprayed coating. The results of this study provide guidance for design and application of high-performance MCrAlY coatings.

Effects of High Temperature Exposure on the Wingate Test Performance in Male University Students.

It has been suggested that heat exposure prior to exercise could induce changes in anaerobic exercise. Therefore, the purpose of this study was to observe the effects of high temperature heat exposure prior to an anaerobic test. Twenty-one men (age: 19.76 ± 1.22 years; height: 1.69 ± 0.12 m; weight: 67.89 ± 11.78 kg) voluntarily participated in this investigation. All of them performed two Wingate tests, vertical jump and macronutrient intake control. On the first day, the test was performed under normal environmental conditions. On the second day, it was performed in a similar way, but with previous exposure to heat at high sauna temperatures (15 min; 100 ± 2 °C). There were no differences in the vertical jump and macronutrient intake. However, the results showed an improvement in power (W) (p < 0.05), relative power (W/kg) (p < 0.01) and revolutions per minute (p < 0.05) 10 s after the start of the test. There was also an increase in thigh (p < 0.01) and skin temperature (p < 0.01) with pre-heat exposure. The results obtained suggest that this pre-exercise protocol could improve power in short and intensive actions.

Alternative low-power plasma-sprayed inconel 625 coatings for thermal solar receivers: Effects of high temperature exposure on adhesion and solar absorptivity

Over recent years, renewable energy technologies have focused on increasing performance and efficiency, and on the reduction of maintenance costs. In this work, thermal-sprayed Inconel 625 coatings have been studied as an alternative for concentrated solar power plants receivers. A low-power compact plasma spray system was used to deposit coatings onto two substrates: grade 22 ferritic steel and AISI 316 L austenitic steel. This system may be used for in-situ maintenance or repair purposes. The coatings were heat-treated at two temperatures: 520 °C and 800 °C, at different exposure times. The aim of this work was to evaluate the effect of this treatment on the adherence and solar absorptivity of the Inconel 625 coatings. The results showed that, at higher temperatures and longer exposure times, better adherence and absorptivity are achieved. Adherence values above 60 MPa were obtained due to diffusion in the coating-substrate interface. Additionally, absorptivity values above 93% were measured due to oxide formation on the coating surface during heat treatment. Furthermore, the highest temperature of the oxidized treatment reported the highest values of absorptivity. These results show that the developed Inconel 625 coatings could be considered as a possible alternative to improve the performance of concentrated solar power plants. • Inconel 625 coatings can be deposited by compact low-power plasma spray. • The adherence is increased at high temperature exposure by interface diffusion. • Inconel 625 coatings reach solar absorptivity values above 93%. • The formation of oxide phases is responsible of the incremental solar absorptivity. • Inconel 625 coatings could be an interesting alternative for solar receivers.

Effect of high temperature exposure on design parameters and collapse behavior of reinforced concrete and steel-framed buildings

In many situations, not only vertical loads but also lateral loads are taken into account in the design of frame systems. However, although fires are rare events, determining possible behavior changes with the increasing temperature is important for design process. Therefore, the current study presents a numerical examination of the fire behavior of two different buildings with the same geometric properties. For this purpose, 4-story reinforced concrete (RC) and steel-framed building models with four spans in the x and y directions were created. Two spaces, one at the corner and one in the middle of the ground floor were exposed to heat loading gradually from 25 °C to 1000 °C (100 °C each time). The internal forces and time to critical temperature for the columns in these spaces were determined. Furthermore, the effect of temperature on plastic hinge formation was examined and the effect of high temperatures on the design parameters was identified. The results obtained revealed that among RC and steel buildings exposed to the same heat loading, the RC building maintained its integrity and did not reach the collapse state. However, the steel building reached its critical temperature and collapse state in 60 min.

Microstructural and non-destructive investigation of the effect of high temperature exposure on ground ferronickel slag blended fly ash geopolymer mortars

It is important to understand the high temperature response of a newly developed construction material in order to assess the effect of fire exposures. The effects of different percentages of ground ferronickel slag with fly ash and different temperature exposures on geopolymer mortars were evaluated by the changes in mass, cracking behaviour , compressive strength , microstructure and ultrasonic pulse velocity after exposure to temperatures up to 1000 °C. Higher residual strength and lower voids and cracks were found in geopolymer mortars containing 50% ground ferronickel slag. The improvement is attributed to the production of sodium magnesium aluminosilicate hydrate ( N - M -A- S -H), which was confirmed by the EDS and XRD analysis. The residual compressive strengths of geopolymer mortar with 50% ground ferronickel slag were 76, 65, 51, 30 and 29 MPa after 2 h of exposure at 200, 400, 600, 800 and 1000 °C, respectively. The XRD results showed a significant increase in the number of crystalline peaks and a decrease of amorphous content at 1000 °C. The amorphous content of the geopolymer with 50% ground ferronickel slag decreased from 79.6% at ambient temperature to 75.5%, 73.7% and 53.1% at 200, 600 and 1000 °C, respectively. The differential variation in higher and lower frequency components of the ultrasonic signal was associated with the residual strength of these specimens. They revealed that geopolymer mortar with 50% ground ferronickel slag had the least amount of pores and cracks. Overall, geopolymer mortar containing 50% ground ferronickel slag showed better performance against high temperature exposure compared to the other mixes. • Ambient-cured GFNS-fly ash geopolymer mortars were exposed to high temperatures. • Higher residual strength was found for the use of 50% GFNS with fly ash. • GFNS improved the residual properties by producing N - M -A- S -H gel. • Crystalline peaks increased and amorphous contents decreased significantly at 1000 °C. • Ultrasonic tests showed the least amount of cracks in the mortar with 50% GFNS.

Properties of concrete with ferrochrome slag as a fine aggregate at elevated temperatures

Ferrochrome slag (FCS) possesses promising properties that promote its use as an alternative to natural aggregates in concrete production. Still, there is a concern about the effect of high-temperature exposure on the properties of concrete containing FCS aggregate. Therefore, due to durability and structural fire safety, it is necessary to evaluate the properties of FCS concrete after being exposed to elevated temperatures. The present study investigates the effect of FCS fine aggregate on the physical and mechanical properties of concrete at room and elevated temperatures (i.e., 200−1000 °C). Microstructural properties at high temperatures were also evaluated using SEM-EDS analysis. The results showed an improvement in the mechanical properties of concrete with FCS fine aggregate compared to conventional concrete. After being exposed to high temperatures, the concrete containing FCS fine aggregate showed less reduction in strength properties and mass than conventional concrete. Such improvements in mechanical and physical properties are achieved due to the chemical composition and surface texture of the FCS aggregate. Microstructural observation and ultrasonic pulse velocity confirmed that FCS concrete suffered less damage upon exposure to high temperatures. Furthermore, the effect of high temperatures on the strength properties of FCS concrete is consistent with the recommendations of the codes (Eurocode 2 and ACI 216.1).

The Effectiveness of Mini Primer STR CODIS in DNA Degradation as the Effect of High-Temperature Exposure

Background More and more today, forensic identification through deoxyribonucleic acid (DNA) examination has achieved greater recognition in supporting Indonesia's law enforcement. Such examination is to determine the origin of a child, paternity cases, genealogical relation, or identifying unknown crime victims. However, along with the development of this DNA material examination, problems arise. DNA undergoes a degradation, commonly known as degraded DNA, which is one of the serious issues frequently encountered by forensic and DNA experts. Some forensic DNA experts take one of the alternatives to overcome this issue by implementing a mini primer set that is through a method to reduce the size of STR assays on DNA core locus examination. Methods In this study, the writers conduct research using the mini primers of CSF1PO, FGA, and D21S11 of the molar teeth exposed to 500°C temperature for 20 and 30 minutes and 750°C for the same amount of time.Result The findings show the DNA contents of molar teeth significantly (p < 0.05) decreased as the effect of high-temperature exposure. PCR result visualization shows CSF1PO is the only locus detected with mini primer exposed to 750°C temperature for 30 minutes (the highest exposure during this research). Conclusions This finding suggests that this locus is potential in examining identification through DNA analysis, especially on a degraded condition as the effect of high-temperature exposure. Besides, this could accelerate the identification process especially on mass disaster events or criminal cases.

Effect of high temperature exposure on the fatigue damage development of X10CrMoVNb9-1 steel for power plant pipes

The aim of this research was to compare the effect of 80 000 h exploitation time in high temperature on mechanical properties and microstructure of X10CrMoVNb9-1 (P91) power engineering steel for pipes. The specimens obtained from two pipes: new, as-received and after exploitation were subjected to fatigue loadings to compare their mechanical responses. Additionally, the uniaxial tensile tests on both types of P91 steel were performed. The microstructure evolution before and after deformation was monitored using optical and scanning electron microscopy. The time intensive, high temperature exposure of P91 power engineering steel led to significant phase transformation and subsequent deterioration of mechanical properties and was further described as a function of the fatigue damage measure, ϕ, and the fatigue damage parameter D. Further proposed methodology of power exponent approximation of the fatigue damage measure, ϕ, and fatigue damage parameter D, allowed to successfully determine the fatigue life of P91 steel.

Effect of fire exposure on residual stresses relief in welded high strength Q690 steel sections

Welding induced residual stresses in steel sections can be reduced by high temperatures in fire conditions and thus affect the load bearing capacity and stiffness of structural steel members. This paper presents effect of high temperature exposure on residual stresses relief in welded high-strength Q690 steel sections by experimental and numerical studies. The distribution and magnitude of the residual stresses in three Q690 steel H-sections and three Q690 steel box-sections after exposure to 600 °C and 800 °C were investigated by cutting method. In the numerical studies, finite element analysis software ANSYS was employed to simulate residual stress generation and relief in the entire welding and high temperature exposure stages, including the heating and cooling phases. The predicted results of the residual stresses after an exposure to high temperature obtained by the finite element analysis agree well with the test results. Parametric studies were conducted to investigate the influence of exposed temperature, high temperature duration, and creep strain in steel on residual stresses after being exposed to high temperature. For welded Q690 steel H- sections and box-sections, equations to evaluate the corresponding residual stress reduction factor at elevated temperatures and after high temperature exposure were proposed based on the results of finite element analysis.

Deterioration of ambient-cured and heat-cured fly ash geopolymer concrete by high temperature exposure and prediction of its residual compressive strength

This paper presents an investigation on the performance of ambient-cured and heat-cured low-calcium fly ash geopolymer concrete after exposure to elevated temperatures. The concrete specimens were heated to 100, 200, 400, 600, 800 and 1000 °C at a heating rate of 5 °C/min. The effect of high temperature exposure on geopolymer concrete was studied by visual inspection, mass loss, extent of cracking, residual strength and microstructure investigation. The total length of cross-section cracks and surface cracks reached their peak values at 800 °C and then declined at 1000 °C. The results show that all the concrete specimens could be heated at 600 °C for 2 h without strength loss. Heat-cured geopolymer concrete specimens showed higher residual compressive strengths than the ambient-cured specimens for all the exposure temperatures. A crushing index of 7.7% could be regarded as the threshold value for coarse aggregate to maintain the initial compressive strength of concrete up to 600 °C. Thus, the microstructural damage as observed by SEM images, dehydration of geopolymer shown by thermogravimetric analysis and the reduced strength of coarse aggregate are considered as the contributing factors for strength losses at temperatures higher than 600 °C. Finally, two prediction equations are proposed which correlated well with the experimental results of this study and those reported in published literature.

Quantitative multi-scale characterization of single basalt fibres: Insights into strength loss mechanisms after thermal conditioning

This article presents an experimental investigation to quantify the effects of high temperature exposure (400–600 °C) on the mechanical properties of single basalt fibres. To this purpose, a combination of single edge notch tension and nanoindentation micro-pillar splitting methods was used to provide an assessment of the fracture toughness of as-received and thermally treated basalt fibres. Similar values were obtained by the two different methods, and interestingly both highlighted an increase in KIc after heat treatment, up to 22% after exposure at 600 °C for 1h (1.59±0.06MPam). The increase in KIc suggests that microstructural changes occur in the fibres, as confirmed by high-speed nanoindentation mapping. Local radial heterogeneity in the fibre structure and elastic modulus and, possibly, the loss of defect orientation originally induced during the fibre drawing process are envisaged to control the decay of basalt fibres tensile strength during high temperature exposure, mimicking a thermal recycling process for composites.

Effects of High-Temperature Exposure on the Mechanical Properties of Kenaf Composites

Automotive parts, including dashboards and trunk covers, are now fabricated through a compression-molding process in order to produce lightweight products and optimize fuel consumption. However, their mechanical strength is not compromised to avoid safety issues. Therefore, this study investigates kenaf-fiber-reinforced polypropylene composites using a simple combing approach to unidirectionally align kenaf fibers at 0°. The kenaf composite was found to withstand a maximal temperature of 120 °C. The tensile and flexural strengths of the aligned kenaf composites (50 and 90 MPa, respectively) were three times higher than those of the commercialized Product T (between 39 and 30.5 MPa, respectively) at a temperature range of 90 to 120 °C. These findings clearly showed that the mechanical properties of aligned kenaf fibers fabricated through the combing technique were able to withstand high operating temperatures (120 °C), and could be used as an alternative to other commercial natural-fiber products.

Effects of high-temperature exposure on fractal dimension of fly-ash-based geopolymer composites

In this study, the microstructures of fly-ash-based geopolymer composites exposed to high temperatures were investigated by surface fractal dimension analysis. Geopolymer pastes with various Na2O contents were exposed to high temperatures. From the results, the mechanical and microstructural properties of geopolymer composites changed after thermal exposure. For the analysis of the microstructure, the surface fractal dimension was evaluated using the pore size distribution measured through MIP. As the temperature increased, the surface fractal dimension of the macropore region increased, but that of the micropore region decreased. After thermal exposure, the surface fractal dimension of the macropore regions showed a tendency to be proportional to the Na2O content, except for Na2O content of 4%. In the micropore region, there was no relationship with the Na2O content. It was found that compressive strength was proportional to the surface fractal dimension of the macropore region except for Na2O content of 4%.

Effects of high-temperature exposure on concrete containing waste porcelain coarse aggregates and steel chips

The objective of this study is to find a new way for improving the heat resistance of concrete at extreme temperatures in structural members at low cost. In this study, a new generation of ceramics or porcelains were used in concrete for the first time. These ceramics have higher strength and heat resistance than all other types of tiles. They were used in concrete as 25% on up to 100% replacements for coarse aggregates, as well as with two types of cement (Portland cement Type I and alumina cement). Red ceramics were also used in some specimens for better comparison between heat resistance of porcelains and ordinary ceramics. Moreover, waste steel chips were used at 1%, 1.25%, and 1.5% volume ratios. The specimens were exposed to temperatures of 100 °C–850 °C, and then their compressive strength, weight change, and long-term behavior were determined. In addition, fractal dimensional changes were also determined to study concrete's crack propagation; it was observed that it decreased to zero in concrete containing Portland cement and waste porcelains after exposure to 600 °C. Conventional concrete made of alumina cement exhibited a reduction of 92% in compressive strength after exposure to 850 °C, while steel chip-concrete and porcelain-concrete showed reductions of 82% and 74%, respectively. Results also indicated that specimens with Portland cement have better heat resistance than alumina cement up to 600 °C, although such specimens were not able to withstand heat above 600 °C.

Effect of High-Temperature Exposure on Degradation of La0.6Sr0.4CoO3 Coated Metallic Interconnects for ITSOFC and SOEC

Previous studies showed the formation of new phases affecting the electrical properties of LSC thin films deposited on stainless steel substrates, which are commonly tested for ITSOFC and SOEC interconnects. A 4.3 μm thick La0.6Sr0.4CoO3 coating was deposited on AISI430 steel by spray pyrolysis, followed by heat treatment (800°C/2h) and an oxidation in air (800°C/96h). The La0.6Sr0.4CoO3 phase interacted with the metallic substrate and formed SrCrO4, causing degradation of the perovskite into La0.9Sr0.1CoO3. An EDS mapping showed Sr and Cr enrichment in the coating/substrate interface. TG analysis indicated a lower mass gain for the coated substrate. The total ASR at 800°C of the interconnect before and after oxidation was 3.23 Ω.cm2 and 3.98 Ω.cm2, respectively. The Ea underwent very small variation, remaining around 0.24 eV (T≤300°C) and 0.65 eV (T≥400°C). The reaction of Cr from the substrate and Sr from LSC seems to have impaired the performance of the interconnect.