Increasing Heating Time Research Articles

Influence of microwave heating on the swelling properties of expansive soil in Hefei

The swelling deformation of expansive soil after immersion often lead to engineering disasters. In this paper, the experiments on the swelling properties of expansive soil in Hefei after microwave heating have been carried out. The results show that, the soil samples change from fine particles to coarse particles after microwave heating. With the increase of microwave heating time, the specific gravity of soil samples first increases and then decreases, while the liquid and plastic limit continue to decrease. In addition, microwave heating significantly affects the swelling behaviors of soil samples. With the increase of microwave heating time, both the free swelling ratio and vertical free swelling strain decrease. In the process of microwave heating, there are a series of physical and chemical changes in expansive soil, such as the water escaping from the interlayer structure of clay minerals, the transformation and decomposition of material components, which significantly changes the physical and mechanical properties of expansive soil.

Components of thermal protection mechanism of carbon/phenolic composites exposed to severe aerodynamic heat

AbstractIn order to improve the thermal protection efficiency of carbon/phenolic (C/Ph) composites used as the heatshield of hypersonic vehicles, it is essential to find out the components of its thermal protection mechanism. In this study, a pyrolysis layer model considering pressure is established to simulate the percentages of heat dissipated by different thermal protection mechanisms. Numerical results reveal that the thermal protection mechanism of C/Ph composites mainly comprises of surface radiation, the heat absorbed by the heat capacity and thermal blockage effect (TBE) of pyrolysis gas, but the TBE weakens as heating time increases. Furthermore, the evolution laws of different thermal protection mechanisms of C/Ph composites with resin content are given. Based on the components of thermal protection mechanisms, both reducing the thermal conductivity of the resin matrix composites and increasing the material emissivity are effective approaches to enhancing the thermal protection efficiency of C/Ph composites exposed to severe aerodynamic heat.

Preheating of Lithium-Ion Battery Electrodes as Basis for Heated Calendering—A Numerical Approach

Lithium-ion batteries are state of the art and, still, their performance is constantly improving. To increase the energy density and electric conductivity, electrodes are usually calendered. Hereby, a higher degree of compaction, while reducing structural damage, can be reached by heating the calendering rolls. For industrially relevant line speeds, it is however questionable whether the contact time between electrode and roll is sufficient to reach the full positive effect of the increased temperature. This study shows a numerical approach based on the discrete element method to simulate the heating behavior of electrodes before and during calendering using a typical NMC-622-cathode as a model structure. To improve the results of existing, more simplified discrete element method simulations, which neglect the heat transfer through the carbon black–binder matrix, an extension with heat transfer through the carbon black–binder matrix has been implemented. Considering process parameters, such as calender roll temperature and line speed, as well as electrode parameters, such as thickness and porosity, this model can provide an individual calculation of the heating behavior to evaluate the need for a preheating device. Specifically, this study provides an in depth analysis of the influence of the mass loading on the heating time. It becomes clear that preheating can be of great relevance especially for high mass loadings, as well as high line speeds, as the required heating time increases by 116% when the basis weight is increased by 50%.

Effect of thermal ageing on physical properties of MX80 bentonite under high-temperature conditions

In a deep geological repository (DGR) system, the buffer layer is indispensable to ensuring the safe disposal of high-level radioactive nuclear waste (HLW). Because the heat generated by the decay of the spent nuclear fuel in a canister is released to the surrounding buffer layers, the bentonite buffer material experiences long-term high-temperature conditions. Therefore, the variations in physical properties of bentonite buffer material under high-temperature conditions are one of the important parameters in the DGRs for HLW. A series of tests on the specific gravity, specific surface area (SSA), Atterberg's limits, and free swelling ratio of MX80 bentonite after heating for different times at a high temperature of 200 °C were conducted, to investigate the influence of thermal ageing time on its physical properties. Then, the microscopic investigations, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), were conducted to explain the aforementioned variations from the microscopic point of view. Based on the crystal layer structure characteristics of montmorillonite, the quantitative relationships between the physical properties of bentonite and its mineral composition or bound water content were established to further explain the mechanism by which thermal ageing affects the physical properties of MX80 bentonite. The results indicate that with increasing heating time, the specific gravity, SSA, liquid limit, plastic limit, plastic index and free swelling ratio decrease sharply by 2.5%, 4.5%, 3.1%, 5.5%, 2.8% and 30.2%, respectively, within 15–30 days of heating. After 30 days of heating, their variations are negligible. Under high-temperature conditions, the transformation of mineral composition, desorption of bound water, and changes in the micro-morphology are the fundamental reasons for the variations in the physical properties of bentonite, and they influence and interact with each other.

Effect of different sweeteners on the quality, fatty acid and volatile flavor compounds of braised pork.

This study aimed to assess how several sweeteners (white sugar, Siraitia grosvenorii fruit, mogrosides, and stevia glycoside) affected the flavor, fatty acid composition, and quality of braised pork. The findings indicated that braised meat prepared with sweeteners differed from typical braised pork. When simmered for 60 min, the typical braised pork with white granulated sugar exhibited a significant cooking loss (CL) and little water content. Significantly more than in the group containing Siraitia grosvenorii, mogroside, and stevia glycoside, the Thiobarbituric acid (TBARS) value increased by 14.39% (P < 0.05). The sample in the group that included mogroside had a low CL rate. After 40 min of stewing, the lean pork has the highest L* value, but the 60-min stew sample is nicely colored and stretchy. Mogroside can prevent protein, and lipid oxidation, is thermally stable and reduces CL during stewing. Additionally, Siraitia grosvenorii and stevia glycosides help prevent oxidation from intensifying during stewing. When Siraitia grosvenorii is added, lipid oxidation is significantly inhibited, and stevia glycosides are more beneficial for enhancing meat color. With an increase in heating time, the fatty acids in braised pork reduced; the unsaturated fatty acid (UFA) of the Siraitia grosvenorii fruit (SF) and mg group also fell somewhat, and the UFA: SFA ratio was higher than that of the white sugar (WS) group. The SFA content of the braised meat in the stevia glycoside group was higher than that of the WS group. In all, 75 volatile flavor elements in braised pork were discovered by Gas chromatography-ion mobility spectrometry (GC-IMS). The sweetener increased alcohols, esters, and acids in the braised pork. As stewing time increased, ketones decreased, but aldehydes and esters increased. The pork formed antioxidant peptides with great nutritional value after cooking. Braised pork with mogroside and stevia glycoside additions primarily have some protein color protection and antioxidant effects. This study may offer fresh perspectives on applying natural sweeteners and enhancing braised pork’s flavor.

The formation of soy protein fibrils-chitin nanowhisker complex coacervates: Relationship to mixed foam stability

The effects of protein fibrillation modifications on foam properties and the foaming and stabilization ability of soy protein fibrils (SPF) and chitin nanowhisker (CNW) complex systems were investigated and evaluated. The results showed that the structure of SPF stretched significantly with the increase of heating time, probably due to the unfolding and rearrangement of protein structure. The foaming ability and stability of SPF were significantly higher than those of natural protein. The SPF and CNW coacervates effectively increased the foam strength, probably due to the interaction between the "worm-like" SPF structure and the short crystal structure of CNW. In addition, the samples containing salt had higher foaming ability, stability and viscosity compared to those without salt, resulting in a significant improvement in foaming properties. This study provided a new idea for studying the functional properties of modified protein-modified polysaccharides complex coacervates.

Flexural Performance and Thermomechanical Coupling Analysis of Full-Iron Tailings Reinforced Concrete Beams

Problems such as carbonization, corrosion, and durability deterioration would occur to full-iron tailings reinforced concrete (FIT-RC) subjected to long-term use at high temperatures, to find solutions for these problems, it’s of important value to research the flexural performance of FIT-RC beam and its thermomechanical coupling mechanism. This paper proposed a calculation method for designing the flexural capacity and deflection of the normal section of FIT-RC beam, and summarized the high temperature relationship among thermal parameters, thermal stress, and thermal strain of FIT-RC material. In our experiment, four-point bending test was performed on the RC beams and the results showed that the bearing capacity of FIT-RC beam is equivalent to that of conventional reinforced concrete (CRC) beam, the failure modes of the two kinds of RC beams are basically the same. At high temperatures, the similarity of mechanical performance of concrete components with different reduction ratios is related to the similarity of temperature field. With the increase of heating time, the difference in the fire resistance grade of concrete components with different reduction ratios decreases to the minimum value. This study has clarified the high temperature relationship between thermal stress and thermal strain, and verified the feasibility of applying FIT to RC structures.

Dielectric anisotropy effects on the microwave-induced thermodynamic response of coal: Numerical simulations and experiments

Microwave heating technology is a promising solution in underground engineering, such as mining, coalbed methane extraction, and oil/gas production, that primarily depends on the conversion of microwave energy due to dielectric properties. However, inadequate understanding of the effects of dielectric properties on microwave irradiation limits further development of microwave techniques. In this study, based on the dielectric anisotropy of coal, an electromagnetic-thermomechanical coupled model was used to numerically investigate the thermodynamic response under microwave irradiation at 2.45 GHz and 1 kW for 180 s. We performed experimental verification via indoor test. Results show that the sensitivity of microwaves to the dielectric direction in the TE10 mode is x > z > y. In different dielectric anisotropy models, the temperature and maximum principal stress increase synchronously and linearly with increasing heating time, and the curve growth rate is positively correlated with the equivalent dielectric permittivity. There are also marked temperature and stress concentrations in the sample. The compressive stress is concentrated in the center of the sample, while the tensile stress is around the outer edge. For bedding coal, tensile fractures occur under microwave irradiation along the bedding, and shear fractures run through the bedding. With the increase of the input microwave energy, the failure mode of coal gradually expands from single fracture to fracture network.

Thermal Stability of L12‐Modified Al2.5Cu0.5Ti Particles in Al Matrix

Herein, the thermal stability of two morphologically differently shaped L12‐modified Al2.5Cu0.5Ti intermetallic compound particles in the same Al matrix is studied by heating the Al–Al2.5Cu0.5Ti refiner fabricated by spark plasma sintering. Studying the thermal stability of two morphologically differently shaped L12‐modified Al2.5Cu0.5Ti intermetallic compound particles in the same Al matrix allows us to control the external experimental factors for both particles at the same time. This gives better results for comparative studies. The result shows that the heat treatment conditions and the different morphology of the L12‐modified Al2.5Cu0.5Ti particles can affect the thermal stability of Al2.5Cu0.5Ti particles in the Al matrix. In addition, the effect of heat treatment on the hardness behavior is evaluated with the Vickers microhardness test. The result shows the variation in hardness with increased heating time.

Analysis of the RCF crack detection phenomenon based on induction thermography.

Eddy current pulsed thermography (ECPT) is used to detect rolling contact fatigue (RCF) cracks on the rail. It is observed that some of the cracks disappear in the thermal image with the increase of heating time. Based on the finite element method, with double cracks as the basic unit, three different crack models are established, and the mutual disturbance relationship between the double cracks is discussed based on the eddy current distribution and thermal diffusion process. The simulation and experimental results show that different crack models are affected by thermal diffusion in different heating stages to different degrees, and the time of the crack thermal image disappearance is obtained. According to the above conclusions, the RCF cracks are extracted and classified based on the influence of thermal diffusion. The possibility of rail condition assessment and maintenance based on the disappearance time is explained.

Effect of acidification and thermal treatment on quality characteristics of high‐moisture laver ( Porphyra spp.)

Effects of two thermal treatments (sterilization at 118°C and pasteurization at 90°C) and acidification on the color, texture, chemical composition, and microstructure of high-moisture laver were investigated. Results showed that the reddish-purple of laver faded to varying degrees after heating due to rapid degradation of phycoerythrin. With increasing heating time, the a* value gradually decreased accompanied by the increase in b* value, and the color changed to yellow-green. Besides, the hardness and toughness gradually decreased, while the adhesiveness increased. Microstructure and soluble sugar results indicated that the cell tissue of the laver was destroyed after intensive heating. Compared to sterilization, laver subjected to pasteurization at 90°C exhibited better texture and color. Intensive thermal processing accelerated quality deterioration as evidenced by pigment degradation, cell rupture, and increase in soluble substances. The combination of acidification (pH < 4.6) with mild heat treatment contributed to better quality retention of ready-to-eat lavers with higher moisture. Practical applications Since most of the existing laver products in the market are dry, the development of high-quality wet laver products has attracted attention. However, due to the extremely thin leaves and soft texture, the color and texture of laver are prone to deterioration during the heat sterilization process. Understanding the quality changes of laver under typical sterilization conditions is conducive for exploring solutions. The present study clarifies the effects of heat treatment and acidification on the characteristics of high-moisture laver, which serves as a foundation for the future development of instant wet laver products that can meet both safety and palatability, and provides theoretical guidance for the seaweed processing industry.

Effect of microwave heating time on the gel properties of chicken myofibrillar proteins and their formation mechanism

SummaryThe present work was conducted to illustrate the mechanism of gel formation of myofibrillar proteins (MPs) under different microwave heating times. The results showed that the denaturation enthalpy (ΔH) of the MPs significantly decreased when the heating time increased from 3 to 9 s and then completely disappeared as the heating time progressed, indicating that the MPs gradually denatured and subsequently aggregated with increasing heating time, which was further verified by the changes in the secondary structure, electrophoretic bands, and gel properties (e.g., water holding capacity and textural profiles) of the MPs. Microstructural images indicated that the MP gel formed under 12 s had the most compact network, indicating that extended microwave heating time could induce quality deterioration of MP gels. Moreover, the hydrophobic forces, electrostatic forces, and disulphide bonds of the MPs gradually intensified with increasing microwave heating time, suggesting that both non‐covalent and covalent bonds could promote molecular denaturation and subsequent aggregation of MPs. In addition, correlation analysis revealed that the changes in the molecular conformation of MPs induced by different microwave heating times could effectively regulate the formation of MP gels and their related properties.

Thermal-Induced Alterations In Lunar Soil Grains Revealed Via In Situ TEM Heating

Impact-induced thermal modifications occur frequently in the solar system, and the microstructures of extraterrestrial samples can reveal the thermal-induced alterations that have occurred to their parent bodies. The characterization and reproduction of these sub-micron features are challenging and require new analytical techniques. The combination of a dual-beam system and transmission electron microscopy (TEM) techniques, with in situ TEM heating, is a promising method. This method can be used to systematically understand the chemical and microstructural changes in extraterrestrial samples resulting from thermal-induced alterations. To better reproduce the microstructures observed in the Chang′E-5 soil grains, a comprehensive series of TEM experiments was conducted by varying the in situ heating conditions and starting materials, including Martian meteorites and Earth samples. The experimental results showed that the nanophase iron (np-Fe0) particles, which appeared in both Fe-rich pigeonite and Fe-poor olivine, as well as the np-Fe0 content and morphology, varied with increasing heating time (0 – 90 min) at 800 °C. These results indicated that the formation mechanism of np-Fe0 particles varied in different matrices. Therefore, our established approach can reveal the thermal-induced alterations in celestial bodies and can be applied effectively for studying the formation of microscopic features in extraterrestrial bodies.

Unraveling inhibitory effects of Alpinia officinarum Hance and curcumin on methylimidazole and acrylamide in cookies and possible pathways revealed by electron paramagnetic resonance

The synchronous mitigative effects of Alpinia officinarum Hance (AOH) and curcumin on the generation of methylimidazole and acrylamide in cookies were investigated. Possible mechanisms related to quenching free radicals, reducing lipid oxidation and eliminating carbonyl intermediates were explored by electron paramagnetic resonance (EPR) and HPLC. The total methylimidazole and acrylamide contents raised with an increase in heating temperature and time, and reached a maximum at 200 °C for 11 min. AOH and curcumin reduced methylimidazole and acrylamide simultaneously; the maximum inhibition rates for methylimidazole and acrylamide were 51.55% (0.015% curcumin) and 73.66% (1.5% AOH). Alkyl free radicals and HO· were proved to be the critical free radicals for methylimidazole and acrylamide, AOH and curcumin quenched these radicals in a dose-dependent manner. The lipid oxidation, active carbonyl intermediates glyoxal, methylglyoxal, and acrylaldehyde were also reduced by AOH and curcumin simultaneously, which may be resulted from the quenching of free radicals.

Effect of glycation on protein structure, amino acid composition and digestibility of silver carp mince

SummaryThis study was to investigate the effects of glycation on the quality of silver carp mince (SCM) proteins. The browning index (BI), sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS‐PAGE), Fourier transform infrared spectroscopy (FTIR), total amino acid composition, chemical score, protein digestibility and reductive power of digested products were determined. The correlation between the degree of glycation, protein structure and protein nutritional quality was analysed. The results showed that the BI value of SCM‐G increased with the increase in heating time. Myosin heavy chain (MHC), myosin light chain (MLC), tropomyosin and actin were the main protein reactants for glycation. Glycation led to the expansion of the secondary structure of SCM proteins. Glycation reduced lysine and cysteine content but did not change the first limiting amino acid (Val) in SCM. The essential amino acid content of glycated SCM remained consistent with the amino acid nutritional requirements for children and above recommended by FAO/WHO. In addition, glycation did not change protein digestibility but significantly increased the reducing power of digested products with increasing degree of glycation. These results provided a theoretical basis for the application of glycation in food processing industry and the development of aquatic products with high nutritional value.

Simultaneous kinetics formation of heterocyclic amines and polycyclic aromatic hydrocarbons in phenylalanine model system

A combination of chemical model system with kinetics study was used to investigate the simultaneous formation of heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Heating a mixture of phenylalanine, creatinine, and glucose at a commonly practiced household cooking time and temperature successfully differentiated the rate formation (k) of HCAs and PAHs. The good fit suggested that the simultaneous formation was an endothermic bimolecular reaction, and followed the first-order model. The rate formation (k) of HCAs and PAHs significantly increased with increasing heating time and temperature. Only 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) showed degradation rate (k) at higher heating temperatures of 210 °C and 240 °C respectively. Increasing phenylalanine concentration increased the possibility of higher HCAs and PAHs formation. The activation energy (Ea) showed that heating phenylalanine mixture resulted in higher rate of formation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and benzo[b]fluoranthen (BbF).

Investigation on Hot Corrosion Behaviour of Inconel 625 and Incoloy 800H Superalloys with YSZ‐Thermal Barrier Coating Under High‐Temperature Environment for Bioreactor Applications

Thermal energy storage is one of the promising technologies in the modern era for balancing the peak power demand without emitting much emission. Molten‐salt technology plays a dominant role among the varieties of thermal energy storage systems. The difficulty in storing the molten‐salt technology requires a storage material with high temperature, corrosion, and oxidation resistance properties. The nickel‐based superalloys such as Inconel 625 and Incoloy 800H possess the desired properties to be used as a storage material for the molten salts. In this present work, the Incoloy 800H and Inconel 625 superalloy specimens were taken up for investigation. The specimens were coated with yttria‐stabilized zirconia as a thermal barrier coating using a plasma spray process. The sodium chloride and potassium chloride molten salts with a weight fraction of 7 : 3 have been taken with both uncoated and YSZ‐coated specimens, and specimens were heated up to 1000°C approximately. The specimens were heated for different hours such as 8, 12, and 16 hours, respectively. The increase in heating time also results in the increase in the tensile property of the specimens. The mechanical testing, such as tensile test and hardness test, was performed to comprehend the mechanical properties. Scanning electron microscope images and X‐ray diffraction analysis were made to study the microstructural properties and the corrosion resistance property. From the test results, YSZ‐coated specimens possess high corrosion resistance and high mechanical strength compared to the uncoated specimens.

Characterizing thermal damage of diorite treated by an open-ended microwave antenna

The thermal damage induced by microwave treatment in rocks has not been well explored, especially when using the dielectric-loaded converging waveguide antennas (DLCWAs). In this paper, the effects of microwave power level, heating time and working distance on the temperature increase, ultrasonic wave velocity reduction, and more importantly, the fracturing characteristics and the damage zone, are comprehensively investigated using a 6 kW microwave source and a customized DLCWA. A novel method is also proposed to adjust the P-wave velocity (Vp) reduction across the thickness of the specimens and to determine the equivalent damage zone. The results show that the temperature and high temperature area, crack number, length and density, and the Vp reduction rate as well as the damage zone all increase as either the power level or the heating time increases and decrease as the working distance increases. The damage zone can be divided into the crushed zone, fracture zone and discrete fragment zone based on the crack characteristics and the crack generation mechanisms. The method proposed is demonstrated to be reliable in predicting the damage zone induced by microwave heating.

Interfacial reaction of aluminum borate whisker reinforced Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy matrix composite

Magnesium matrix composites usually possess high strength and stiffness as well as low coefficient of thermal expansion, which makes them promising in lightweight and energy-saving strategies. Although the interfacial bonding state has a crucial influence on the properties of magnesium matrix composites, the interfacial reaction mechanism of Mg-RE alloy matrix composites is still unclear. Herein, the interfacial reaction and microstructure of Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy matrix composite reinforced with aluminum borate whisker (Al18B4O33w) were reported by heating the matrix to a semisolid region and inducing the interfacial reaction to continue. After heat treatment at 600 °C for 6 h, the thickness of the interface layer increased from 50‐120 nm to about 335 nm, and the main interfacial reaction product was (Mg0.4Al0.6)Al1.8O4. With the increase of heating time to 12 h, a new double interface layer with (Mg0.4Al0.6)Al1.8O4 in the inner layer and MgO in the outer layer was formed. The difference of interfacial reaction products during isothermal heat treatment was related to the concentration gradient of Mg atoms along the radial direction of the whiskers and the hindrance of the migration of Mg atoms by reaction products formed in the early stage. These findings provide a further understanding of the interfacial reaction of Al18B4O33w reinforced Mg-RE alloy matrix composites.

Texture and microstructure of heat and acid induced gels from buffalo and cow milk: Effect of thermal treatment and fat content of milk

Fat content and heat treatment of milk affect the texture of direct acidified milk gels. Gels were produced from cow or buffalo milk standardised to 3, 4.5 and 6% fat, and heated at 90 °C for 0, 6 or 12 min prior to citric acid acidification at 85 °C. Effects on composition, microstructure and textural properties were investigated. The total solids yield was on average 18% higher for buffalo than cow milk gels. A higher fat content in the gels and softer gels regardless of milk origin. Buffalo milk gels were significantly harder and had a denser protein network compared with cow milk gels with the same milk fat content and produced under the same conditions. Increase in heating time caused softening of gels with 6% fat independent of milk origin. This work shows the potential of modifying cow milk composition to modulate the texture of gels.