Increasing Heat Treatment Temperature Research Articles

Oxidative Stability of Avocado and Peanut Oils Under Different Heating Temperatures

The objective of this research was to investigate the effect of heating temperature on the quality parameters of avocado and peanut oils subjected to heating. Vegetable oils were heated at varying temperatures (110, 140, 170, 200 and 230�C for 30 min) to follow quality alterations. Levels of peroxide value, iodine value, thiobarbituric acid reactive substances, total polar compounds, refractive index, free acidity, and fatty acids composition were determined to measure the extent of lipid oxidation. Peroxide value was significantly (p [ 0.001) influenced by heating temperature in the case of peanut oil. Iodine value decreased significantly (p [ 0.01) in both oils with the increase in heating temperature due to the decrease of the unsaturation degree. Avocado oil showed the smallest increase in thiobarbituric acid reactive substances and total polar compounds during heat treatment. The fatty acids profile of peanut oil was rich in polyunsaturated fatty acids with a level of 42%, followed by monounsaturated fatty acids with about 36%. The heat treatment of oils has produced changes in unsaturated fatty acids, these have undergone isomerization from cis to trans form. The increases of heating temperature up to 230�C significantly deteriorated the quality of peanut oil, but to a lesser extent the one of avocado oil.

Unveiling the mechanisms of in-situ combustion of post-steam driven heavy oil by electric heating method induced auto-ignition

Ignition design of air injection wells is the crucial factor to a successful in-situ combustion. In this paper, experimental studies were carried out on post steam flooding wells at JIN-91 of Liaohe oilfield for improving ignition success rate. The experiments were conducted by a high temperature-pressure ignition device specifically designed for in-situ combustion, and the effects of various parameters were investigated by factorial experiments. The results showed that the ignition temperature was reduced and the ignition time was shortened due to three factors: heating temperature, reservoir pressure, and clay minerals. When heating temperature exceeded 360 °C, experimental pressure was higher than 4.0 MPa, and 10% of montmorillonite clay was added, the crude oil samples could be ignited rapidly. According to the factorial results, the most effective method to shorten ignition time is by increasing heating temperature, the safest method to reduce crude oil spontaneous combustion temperature and to shorten ignition time is by applying clay minerals, and reservoir pressure is the key factor for safety operation during ignition operation. These results will provide experimental theoretical guidance for high efficiency ignition, process optimization, and safe implementation of crude oil reservoir, they also will deliver tech support for the high efficiency operation of in-situ combustion.

Experimental studies on the physical and mechanical properties of heated rock by air, water and high-viscosity fluid cooling

A series of tests were conducted to study the thermal shock damage effect on the physical and mechanical properties of granite and limestone in different cooling media. The dry rock specimens were heated slowly to different target temperatures ranging from 25 °C–800 °C and then quickly cooled to room temperature in air, water, and high-viscosity liquid. After the heat treatment, physical and mechanical properties, such as P-wave velocity, mass, uniaxial compressive strength, elastic modulus and microstructure, were measured. The test results showed that the P-wave velocity, uniaxial compressive strength, and elastic modulus of the heated limestone and granite were all lower after thermal shock in the three cooling media. With increasing heating temperature, the changes in physical and mechanical properties became more pronounced. Air cooling has least influence on rock behavior among the three cooling media. Compared with water cooling, high-viscosity liquid cooling caused less degradation on the physical and mechanical parameters of rocks at any target temperature, which indicates that the thermal shock effect of high-viscosity liquid cooling on rocks was slightly lower than that of water cooling. The brittleness of the rock was affected by the treatment temperature and cooling media. When the treatment temperature was low, the brittleness of the rock was obvious. The brittleness of rock was maintained well by air cooling and was weakened by high-viscosity liquid cooling. Water cooling made the rock more ductility than the other two media.

Effect of treatment temperature on the initial performance of layers of water-based paints in heat-treated pine and beech wood

Hardness, surface roughness, and adhesion strength were determined for water-based opaque paints applied to heat-treated wood material surfaces. For this purpose, Scotch pine (Pinus sylvestris L.) and beech (Fagus orientalis Lipsky) woods were used as experimental material. Specimens were subjected to heat treatment at 3 different temperatures (150, 180, and 210 °C) and 2 different periods (2 and 4 h) under laboratory conditions. Two-component water-based paints with commercial codes D17 and D45 were applied to the surfaces. The hardness, surface roughness, and adhesion strength values of painted samples were determined according to the applicable standards. The results showed that there were higher values of hardness and surface roughness of water-based paints in short-term heat treatment compared with long-term heat treatment. A general decrease in pine with D17 and D45 paints applied to the surfaces and in beech with D45 in adhesion strength was detected depending on the increasing heat treatment temperature and duration. An increase was observed in beech samples with D17 paint applied.

Experimental and first-principles study on the effect of oxygen vacancy on infrared emissivity of CeO2

Ceria is considered a potential candidate for high-temperature infrared stealth materials due to its high melting point, oxidation resistance and low infrared emissivity. As reported, the infrared emissivity of ceria can be reduced after high temperature treatment. However, the available researchers have only analyzed the reasons for this change from the aspect of microstructure morphology. In this study, ceria with different oxygen vacancy concentrations were obtained by heat treatment of ceria powder at different temperatures and their infrared emissivities in 2.5–14 μm were characterized. The experimental results show that with the increase of heat treatment temperature, the oxygen concentration increases and the emissivity decreases. The electronic structure and reflectivity of ceria at different oxygen vacancy concentrations were obtained by first-principles calculations. The calculated results show that the reflectivity of ceria and the DOS peak area near the Fermi level increase with increasing oxygen vacancy concentration. Through this study, we demonstrate that the emissivity of ceria decreases with increasing oxygen vacancy concentrations, which is due to the increase in free carrier concentration.

Microwave processing and characterization of alumina reinforced HA cladding for biomedical applications

The present work comprises of enhancing the bioactivity of the SS-316L substrate by Hydroxyapatite (HA) + 10 wt% Al2O3 (HA10AL) powder using microwave supported surface modifications techniques. The microwave supported surface modified layer has a thickness of around 0.8 mm with the exposure time of 15 min. The surface modified specimens were heat treated at different temperatures (400 °C, 600 °C and 800 °C) for 2 h. Various characterizations tools were employed to characterizing the microwave supported surface modified specimens (as-deposited along with heat-treated). The microstructural study revealed the presence of HA and reaction induced HA phases in the inter-dendritic regions of the Fe-based austenite dendrite matrix. It has been observed that porosity generally decreases after the heat treatments due to faster diffusion of atoms, which fills the pores and voids, whereas the hardness showed the increasing trends with heat-treatment temperature. XRD spectra shows the presence of HA and Al2O3 phases along with iron (Fe), calcium iron phosphate (Ca19Fe2(PO4)14), iron phosphide (Fe2P), along with main iron nickel (Fe-Ni) based matrix at high temperature in all the microwave supported surface modified specimens. The apatite layer was successfully formed on the microwave supported surface modified specimens at all conditions after immersed in simulated body fluid (SBF) test. It was found that apatite formation was reduced with an increase in heat-treatment temperature due to reduction in porosity and amorphous phase (tri-calcium phosphate).

Influence of heat treatment on stainless steel 316L alloy fabricated using directed energy deposition

This article discusses the influence of heat treatment on the micro structural and mechanical properties of stainless steel 316L (SS316L) structures constructed using directed energy deposition (DED). Stress relief and solution treatment at 650 °C for 2 h (HT1) and 1100 °C for 2 h (HT2) are used to reduce the ferrite phase in the SS316L structure constructed by DED. Microstructure and x-ray diffraction analysis showed that the austenite phase exists under any circumstances, and the strength of the ferrite phase decreases as the heat treatment temperature increases. Compared with as-built samples (ABS), the plastic retention capacity of heat-treated samples is increased, and the microhardness is decreased. The maximum elongation was observed in the HT2 sample, and the maximum ultimate tensile strength was obtained for as built sample.

Analysis of Solar Irradiance Variation on Heat Flux and Temperature Distribution for a Dish Concentrator Receiver

Abstract Concentrated solar power presents immense scope for the deployment of small-scale units focusing on diverse applications, including process heat and rural on/off-grid applications. This paper presents the analysis of solar irradiance variation on heat flux and temperature distribution at the dish concentrator receiver. A solar dish concentrator with a 2.8-m aperture diameter and a 0.4-m depth was used for this analysis. The solar ray intersection between a dish concentrator and its receiver, along with the heat flux distribution prediction, was carried out using SolTrace. The effect of flux intensity variation on temperature distribution at the receiver was investigated using comsol multiphysics. The optical analysis considered 10,000 rays, and 91.65% of them were observed to reach the surface of the receiver. For 1000 W/m2 of beam solar radiation, a peak heat flux and maximum temperature at the concentrator’s focal plane are found to be 32.4 MW/m2 and 923 K, respectively. The validation had been done using previously reported results in the literature to verify the correctness of the present simulation results. The effect of beam solar radiation variation on heat flux intensity and the temperature distribution revealed that both heat flux and temperature increase with increasing solar radiation, which points out the influence of design and operating conditions. Apart from PillBox and Gaussian distributions, the effect of slope and specularity errors was characterized, suggesting a greater sensitivity to the former than the latter.

A novel method for preparing Al/Mg/Al laminated composite material, processing maps and interface diffusion analysis

A novel method of “fully covered + friction stir welding + accumulative roll bonding” was developed to prepare an Al/Mg/Al laminated composite material (LCM). This work presents a rolling simulation of an Al/Mg/Al LCM using the DEFORM software and processing maps to show the hot rolling mechanism. The single pass reduction should be set at approximately 3–4 mm by finite element simulation. The edge damage value of the core Mg alloy plate in the Al/Mg/Al LCM decreased with the increasing hot rolling temperatures. The optimum process parameters were obtained by processing maps for deformation temperatures from 250 °C to 300 °C and 350–400 °C in the strain rate range of 0.01 s−1 to 0.1 s−1. The hot rolling temperature for the 11.5 mm-thick Al/Mg/Al LCM should be controlled at 400 °C, and the single pass processing rate should be selected in the range of 20–40%. With each increase in heat treatment temperature and time, the compound gradually increased, and the thickness of the transition layer gradually increased at the Mg/Al interface. The growth kinetic model formulas of the interface layer for the 1060/AZ31/1060 LCM under different rolling strain fields were obtained, which could have been predicted by the interface layer thickness at different rolling reduction rates and heat treatments.

Effect of Water Immersion on Raw and Expanded Ugandan Vermiculite

Effect of water immersion at different times (from 1/2 h to 24 h) on raw and expanded vermiculite from Uganda was investigated. The expansion was carried out by electrical heating at different temperatures and by irradiation with microwaves. After, the expansibility (k) and the water absorption content (WA) were obtained and the samples were characterized. The elemental and mineral composition was determined by X-ray fluorescence and X-ray diffraction, respectively; the thermal behavior by thermal gravimetric analyses; and the textural parameters by BET. The expansibility of Ugandan vermiculite is relatively lower than the other commercial vermiculites due basically to its lower K2O content (0.36%) and higher water content (about 20%). The water absorption capacity of samples significantly increased with the increase in heating temperature. The maximum WA content, about 130 mg/g, was obtained at 900 °C for 24 h. The loss of water during the expansion process in the Ugandan vermiculite caused loss of structural order and crystallinity. Moreover, in the samples expanded and subsequently immersed in water, the structural order and crystallinity increased with increasing WA values. Specific surface area and porosity hardly vary with temperature and are practically independent of vermiculite purity. Expanded commercial vermiculites could be a suitable hygroscopic material, given its efficient water absorption. Microwave expanded commercial vermiculites, in this case, would not be recommended.

Microstructure and Mechanical Property of Al6Si2Cu Alloy Subjected to Double-Solution Heat Treatment

This study aims to develop the mechanical properties of the Al6Si2Cu aluminum alloy through the double-solution treatment. In addition to the Al matrix, large amounts of coarse eutectic Si, Al2Cu intermetallic, and Fe-rich phases were generated through thermo-calc simulation in agreement with the equilibrium phases. The eutectic Si phase is fragmented and spheroidized by the solution treatment as the heat treatment temperature and time increase. The Al2Cu intermetallic phase is dissolved into the Al matrix, resulting in an increase in both strength and elongation. The second-step solution temperature at 525 °C should be an optimum condition for enhancing the mechanical properties of the Al6Si2Cu aluminum alloy.

Molecular docking simulation combining with multi-spectroscopy techniques clarify how small molecule ligands bind to biomacromolecule: Myosin and aldehydes as a case study

The protein is an ideal food matrix binding volatile compounds. However, the synergistic effects between the protein rheological behavior and protein-ligand interactions on the small molecule ligand retention are not fully reported. This study clarified how aldehydes bind to myosin during the constant thermal treatment. The results presented that the myosin unfolded at 25–64 °C and were cross-linked to generate polymers at 75–79 °C. The α-helix fractions of myosin turned into β-turn and random coil fractions, regulating the rheological behavior and exposing more binding sites with aldehydes. The binding affinity of myosin with aldehydes was confirmed. Notably, the fluorescence quenching behaviors of myosin were increased (p < 0.05) with the increase of pentanal concentration and heating temperature. Synergistic effects between the rheological behavior of myosin and the myosin-aldehyde molecular interaction might predominantly contribute to the aldehyde retention. The hydrophobic interaction, amino acid residues, free sulfhydryl groups, and hydrogen bond might be the key (non)covalent linkages for myosin to bind aldehydes. Thr125, Pro128, Trp131, and Val187 might be key sites between myosin and pentanal, among which the chemical forces were the conventional hydrogen bond, alkyl, pi-alkyl, and alkyl hydrophobic among them, respectively.

Experimental investigation on the effects of heating-cooling cycles on the physical and mechanical properties of shale

The deep shale gas reservoirs are characterized by great burial depth, high formation pressure, high temperature. During the hydraulic fracturing process, the fracturing fluids will inevitably exchange heat with the surrounding rock, causing the shale in the near-well zone to undergo temperature alternation, the physical and mechanical properties of shale reservoirs are significantly affected, which brings technical difficulties to fracturing optimization design. In this paper, the Longmaxi Formation shale is used to pay attention to the rock physical and mechanical characteristics of the shale undergo temperature alternation, the microstructure and damage and fracture characteristics of the shale undergo temperature alternation are analyzed. The results show that: (1)As the heat treatment temperature increases and the number of heating-cooling cycles increases, the permeability of the shale increases, the P-wave velocity decreases, the tensile strength (TS) decreases, and the brittleness index rises. (2) Heat treatment temperature and the number of heating-cooling cycles have little effect on the triaxial compressive strength (TCS) of shale. However, it has a significant effect on the failure mode of shale. The increase of temperature and the number of heating-cooling cycles will enhance the degree of fracture of the shale failure surface. (3) Based on industrial CT scanning and scanning electron microscopy (SEM) observations, the thermal cracks caused by heating-cooling cycles are mostly inter-granular cracks and inter-layer cracks, which unfold on the surface of the sample and extend to the interior. Heating-cooling cycles also lead to an increase in the diameter of organic pores. The study results can provide a certain theoretical basis for the optimization design of staged fracturing parameters for horizontal wells in the process of deep shale gas development.

Behavior and modeling of post-heated circular concrete specimens repaired with fiber-reinforced polymer composites

Exposure of buildings to fire is one of the unexpected events during the life of the structure. The heat from the fire can reduce the strength of structural members, and these damaged members need to be strengthened. Repair and strengthening of concrete members by fiber-reinforced polymer (FRP) composites has been one of the most popular methods in recent years and can be used in fire-damaged concrete members. In this paper, in order to provide further data and information about the behavior of post-heated circular concrete columns confined with FRP composites, 30 cylindrical concrete specimens were prepared and subjected under four exposure temperatures of 300, 500, 700, and 900. Then, specimens were repaired by carbon fiber reinforced polymer composites and tested under axial compression. Results indicate that heating causes the color change, cracks, and weight loss of concrete. Also, with the increase of heating temperature, the shape of stress–strain curve of FRP-retrofitted specimens will change. Therefore, the main parts of the stress–strain curve such as ultimate stress and strain and the elastic modulus will change. Thus, a new stress–strain model is proposed for post-heated circular concrete columns confined by FRP composites. Results indicate that the proposed model is in a good agreement with the experimental data.

Microstructure and Mechanical Properties of Cast and Hot-Rolled Medium-Carbon Steels under Isothermal Heat-Treatment Conditions

In this study, the changes in the microstructure and mechanical properties during isothermal heat treatment of cast steel before and after hot deformation were investigated using medium-carbon steel with low alloy content. The microstructural characteristics of the cast and hot-rolled medium-carbon steel under isothermal heat-treatment conditions were examined using optical microscopy and scanning electron microscopy in conjunction with electron backscatter diffraction. The variation in the mechanical properties was evaluated using Rockwell hardness and tensile tests. After maintaining an austenitizing condition at 1200 °C for 30 min, an isothermal heat treatment was performed in the range 350–500 °C, followed by rapid cooling with water. Both the cast steel and hot-rolled steel did not completely transform into bainitic ferrite during isothermal heat treatment. The partially untransformed microstructure was a mixture of martensite and acicular ferrite. At 500 °C, the prior austenite phase changed to Widmanstätten ferrite and pearlite. At 450 °C, bainitic ferrite and cementite were coarsened by the coalescence of ferrite and subsequent diffusive growth. The mechanical properties increased as the isothermal heat-treatment temperature decreased, and the hardness of the cast steel was generally higher than that of the hot-rolled steel. Hardness and strength showed similar trends, and overall mechanical properties tend to decrease as the isothermal heat-treatment temperature increases, but there are slight differences depending on complex factors such as various phase fractions and grain size.

Effect of heat treatment temperature on microstructure and tensile properties of austenitic stainless 316L using wire and arc additive manufacturing

The effect of heat treatment temperature on the microstructure and tensile properties of 316L stainless steel fabricated by wire and arc additive manufacturing was studied in this paper. Heat treatment was used to uniformize the microstructure, eliminate the anisotropic tensile properties in as-built 316L part, and improve the poor elongation caused by the multilayered structure of alternating re-melting area (RA) and overlapping area (OA). The results showed that the heat treatments below 1000 °C had no significant effect on the multilayered structure and columnar austenite grains, but only changed the morphology and content of ferrite and σ phase within the grains. With the increase of the heat treatment temperature, ferrite transformed into σ phase and the fraction of second phase gradually decreased, leading to the slight increase of elongation but decrease of material strength and its anisotropic degree. After solution annealing above 1000 °C, the ferrite and σ phase was nearly dissolved in the austenite matrix. The austenite recrystallized and the multilayered structure was destroyed, which played a major role in the tensile properties. With the increase of heat treatment temperature, the fraction of recrystallization increased, resulting in decrease of material strength. The elongation was greatly improved and reached that of the annealed state, and its anisotropic was almost eliminated.

Thermal excitation studies on the silica coating magnetite composite microspheres with Mössbauer spectra and first principle calculations

Fe3O4 nanomaterials have attracted lastest interests due to their excellent properties and potential applications. In this paper, the thermal excitation is investigated by Mössbauer spectra and first principle calculations. Fe3O4 nanoparticles with uniform size, regular shape and good dispersibility are prepared by the solvothermal methods, and Fe3O4@SiO2 composite magnetic particles with layers of mesostructured SiO2 structure are assembled by improved Stöber method. The particle size is 500 nm and the shell thickness of SiO2 layer is 80 nm. Fe3O4@SiO2 composite magnetic particles are then annealed at different temperature of 200 °C, 400 °C and 600 °C. The experimental measurements exhibit that the grain size grows up, and the magnetization is enhanced significantly, with increasing heat treatment temperature. However, Mössbauer spectra show that the relative absorption intensity in B-site fast decreases as increasing heat treatment temperature, from 64% at room temperature to 27% at 600 °C, indicating that large amount of Fe vacancies may form in B-site, and correspondingly, the net magnetic moment due to the difference of amount of Fe in B and A sites would be reduced, which strongly disagrees with the results of magnetization measured by vibrating sample magnetometer. In order to find the mechanism behind magnetization, the first-principle calculations are performed and reveal that the oxygen ions in the SiO2 shell may go into Fe3O4 core, which causes number of Fe2+ ions to decreases and transfer to Fe3+ ions, leading to the increase of magnetic moment. So we classify the difference between the amount of Fe3+ and Fe2+ ions in B-site as γ-Fe2O3. Based on this, Mössbauer spectra analysis presents quantitatively the concentration of various phase and their hyperfine interactions. This work provides a method to analyze the magnetic moment of Fe3O4.

Optimization of the operation mode of regenerative heat exchangers

The paper considers the operation of regenerative heat exchangers with a fixed checkerwork. Such a checkerwork allows for high-temperature heating of gases and is made of refractory materials with a relatively high heat capacity, but low thermal conductivity. The article presents calculations of regenerative heat transfer for devices with block checkerwork. It is shown that a decrease in the equivalent diameter of the channel d e leads to an increase in the average air heating temperature over the period. An increase in the relative water section of the checkerwork f also leads to an increase in the air heating temperature, but only to a certain limit. On the one hand, with an increase in the relative water section, the specific heat exchanger surface increases. On the other hand, at a certain value f, the accumulating mass of the checkerwork significantly decreases, and as a result, the air heating temperature decreases. For the same reason, for checkerwork with a high value of the relative water section, it is necessary to reduce the duration of the heating/cooling periods of the checkerwork. The paper also examines several types of compact checkerwork, which are very promising, including in heat storage systems. It is noted that the use of such attachments in conventional regenerate heat exchangers is impossible. First, it is necessary to increase the water section of the heat exchanger and significantly reduce its height, otherwise, the pressure loss will increase sharply. Secondly, it is necessary to significantly reduce the duration of the heating/cooling periods, otherwise, due to more intense heat exchange, the air temperature at the outlet of the regenerative heat exchanger changes much more than in the block checkerwork.

Experimental and Numerical Investigation on Thermal Damage of Granite Subjected to Heating and Cooling

Rock mass is frequently subjected to rapid cooling in geothermal reservoir during water injection and reinjection. In this paper, to understand the effects of cooling treatments on heated granite, heat conduction tests, magnetic resonance imaging tests and numerical investigations were carried out to evaluate variations of thermal damage. The test results reveal that the heat flux and the heat transfer coefficient increases to a maximum within a few seconds and then gradually decreases. The maximum heat transfer coefficient of the samples treated with the initial temperature of 500, 400, 300, 200 and 100 °C is 2.3, 2.15, 1.9, 1.22 and 1.86 W·m−2K−1, respectively. The edge area with drastic temperature changes is accompanied by the densely distributed microcracks; in contrast, the internal cracks of the specimen with gentle temperature are relatively sparse. The thermal damage contributed by the heating cracks occurs at a continuous decrease, and the thermal damage contributed by cooling occurs at a continuous increase, with the increasing heating temperature. The damage caused by heating is the result of the uneven thermal expansion of the local particles, the propagation of cooling cracks is strongly affected by heating cracks, and stress concentration induced by thermal shock promotes the coalescence of the pre-existing heating cracks.

Simple thermal and freezing treatments to improve absorption capacity and alter digestibility of canna starch granules

Swollen canna starches (SCS) were prepared by controlled heating of unmodified and heat-moisture treated (HMT) starch suspensions at sub-gelatinization temperatures; subsequently, freezing was conducted to stabilize the structure of the SCS. Sizes of both unmodified and HMT swollen granules increased with increasing heating temperatures (up to 2.5 times), and freezing resulted in a significant reduction of granular size. The absorption capacities of the swollen starches increased up to 6 times for water and 3 times for tributyrin and palm oil compared to unmodified starch. The differences in absorption capacities of the unmodified and HMT swollen starches were small. Freezing the swollen starches tended to decrease oil and water absorptions, except for unmodified starch swollen at 70 °C, where freezing increased water absorption. Freezing significantly decreased the susceptibility of the swollen unmodified starches to amylase digestion and slowed down the digestion of the swollen HMT starches.