Effect Of Rapid Heating Research Articles

Production of phenolic monomers from lignin in hydrothermal medium: Effect of rapid heating and short residence time

This study investigates the influence of heating rate and short residence time (1–15 min) on the hydrothermal liquefaction (HTL) of alkali lignin, as a function of reaction temperature (280–320 °C). A novel induction-heating reactor system (IHRS) was designed and was used for rapid heating rate (∼100 °C/min), while a resistive-heating reactor system (RHRS) was used for slow heating rate (∼5.3 °C/min). The experiment using IHRS with a short residence time (1 min) resulted in the highest yield of carbon recovery in biocrude (52.2 ± 0.63 wt%) at 320 °C under autogenous pressure. In contrast, the experiments using RHRS or longer residence time (8–15 min) with IHRS showed lower biocrude yield due to the promotion of gasification and undesired secondary reactions. The detailed characterization of biocrude revealed that rapid heating rate improves the selectivity of compound in biocrude, such as phenol, while slow heating rate produced a broader distribution of compounds, including anisole and alkyl phenols at 320 °C for 1 min residence time. Furthermore, the usefulness of phenol as capping agent during IHRS of lignin was demonstrated in suppressing char formation and increasing biocrude yield.

Effects of Rapid-heating and/or High-pressure Conditions on Coke Making, Examined Using a Synthetic Model Compound

Effects of Rapid-heating and/or High-pressure Conditions on Coke Making, Examined Using a Synthetic Model Compound

Flash heating boosts the potential for mechanochemical energy sources for subglacial ecosystems

Subglacial environments harbour a diversity of microbial ecosystems capable of influencing biogeochemical cycles. However, the darkness and isolation of subglacial environments limit the energy sources available for microbial metabolism. A recently recognised energy source for these microbes in wet-based regions is the rock-water reactions that occur after the mechanical fracturing of glacial bedrock. These mechanochemical reactions produce H2 and H2O2 at 0°C from reactions with mineral surface defects (Si• and SiO•) and release Fe from within the mineral structures, providing electron donors and acceptors for microbial metabolism. However, the production of H2O2 and H2 may be underestimated as temperatures at rock abrasion sites can increase substantially above 0°C as glaciers “slip and grind” rocks, potentially accelerating the rates of mechanochemical reactions. Despite this, the effect of rapid heating on subsequent low-temperature mechanochemical reactions has yet to be examined. Here, we investigate H2, H2O2, and Fe production during low-temperature (0 °C) incubations of water with a range of ground rocks and minerals following “flash heating” to 30, 60, or 121 °C. We show that transient increases (as little as 5–10 min of heating) to moderate temperatures (30 or 60 °C) can significantly increase the rate of H2 production, while short-term heating to 121 °C generates larger bursts of H2. In addition, pyrite is easily crushed, potentially releasing large quantities of Fe2+ into subglacial systems and promoting mechanochemical reactions due to the resulting large surface area (10× larger than other materials). We provide the first evidence for H2 production from water reactions with crushed pyrite and suggest that crushed pyrite has a greater influence on subglacial H2O2 production than silicates. We conclude that electron donors in the form of Fe2+ and H2 bursts can be produced in subglacial ecosystems, which may be coupled to substantial concentrations of H2O2 produced from crushed pyrite. This suggests that rock–water mechanochemical reactions may be a greater source of energy for subglacial environments than previously recognised.

Effects of rapid heating on the phase transformation and grain refinement of a low-carbon mciroalloyed steel

The present study aims to clarify the possibility of rapid heating in the preparation of low-carbon ultrafine (UFG) steel. The effects of heating rate on the phase transformation, microstructure and precipitation of a low-carbon microalloyed steel were elaborately investigated. The results manifest that rapid heating potentially provides a simple and innovative process for the preparation of UFG steels just by increasing the heating rate. The parent austenite grains were refined due to the more reserved (Nb, Ti, V)C precipitates and dislocations within a short heating process by rapid heating. However, an effective holding time was proposed in the rapid heating to ensure the refined austenite grains. Moreover, the synthetic influences of initial increased grain boundaries and redissolved (Nb, Ti, V)C carbides provoked the abnormal grains with weakened thermostability. Redissolution of (Nb, Ti, V)C carbides were apparent during austenite nucleation at a slow heating rate, and it was verified during the isothermal holding stage by rapid heating. In addition, the austenitic phase transition occurred at higher temperature with the increase of heating rate, by which the transformation rate was accelerated.

The effect of plasma-assisted ball milling on preparation and sintering behavior of (Zr0.1429Hf0.1429Ce0.1429Y0.2857La0.2857)O2-δ high entropy fluorite oxide

The sintering process of high entropy fluorite oxide ceramics prepared by the conventional solid-phase reaction method suffers from high single-phase synthesis temperature, low densities, and abnormal grain growth. To improve the sintering characteristics of high entropy fluorite oxide ceramics, the oxide mixture was dealt with dielectric barrier discharge plasma-assisted ball milling. The samples were analyzed using XRD, SEM, TEM, TG/DTG, visual high-temperature deformation analyzer, and nanoindentation meter. The results show that the plasma field activates the raw material powder and promotes powder finer. The rapid heating effect of the plasma during the ball milling process causes micro-area sintering and micro-area melting on the powder surface, which increases the active sites of the solid phase reaction of the material, accelerates the mass transfer process, and improves the sintering activity. Compared with conventional ball milling, plasma-assisted ball milling reduces the single-phase synthesis temperature of high entropy ceramics from 1500 °C to 1300 °C. The sintered ceramic pellets have intact grain growth, no noticeable abnormal grain growth, and improved density and mechanical properties.

Superhydrophobic natural melanin-coated cotton with excellent UV protection and personal thermal management functionality

This study presents a new approach to imparting the combined functionalities of superhydrophobicity, UV protection and personal thermal management via the photothermal effect to cotton fabrics. Surface modification of fabrics was carried out by applying coatings containing natural melanin (NM) particles extracted from yak hair and fluorine-free polydimethylsiloxane (PDMS) polymer via a dip-pad-dry-cure process. Different concentrations of NM particles were used in the coatings and the roles of each ingredient in achieving the desired functionalities were investigated. In addition, the relationship between NM content and the resultant durability of the coatings was explored based on the variations in superhydrophobicity, UV protection, photothermal performance, and color strength of the fabrics. The results demonstrated that the non-fluorinated NM/PDMS coatings were highly effective in developing a superhydrophobic cotton fabric with a water contact angle of 164°. The NM-coated fabrics provided a rapid heating effect under near-infrared light and their temperature increased to 38.4–45.3 °C, which was up to 14.7 °C higher than that of pristine cotton. Furthermore, the application of NM particles resulted in an excellent UV protection performance and generated the UV protection factor level of 198.48 on cotton fabrics. Finally, the coated fabrics were highly breathable and showed high stability against 1000 abrasion cycles, 5 accelerated washing tests, and 70 h UV irradiation. These findings provide new pathways in the development of future functional textiles using user-friendly and biocompatible ingredients.

Effect of Rapid Heating on Microstructure and Tensile Properties of a Novel Coating-Free Oxidation-Resistant Press-Hardening Steel

Effect of Rapid Heating on Microstructure and Tensile Properties of a Novel Coating-Free Oxidation-Resistant Press-Hardening Steel

Real-time monitoring of volatiles and particles emitted from thermoplastic filaments during 3D printing

The proliferation of consumer-grade three-dimensional (3D) printers using fused deposition, also known as fused filament fabrication, has given rise to concerns over the exposure of users to potentially harmful substances. Thermoplastic filaments made of different polymers are extruded through a heated printer nozzle and deposited layer by layer on a build platform to form the printed object. This process leads to the emission of both particles and gases, in particular volatile organic compounds (VOCs). While the emission of airborne particulate matter during 3D-printing has been relatively well researched [1], this is not the case with the monitoring of the associated emission of VOCs, and so we are far from understanding the emission profile of 3D-printers as a whole. The main reason for that is the difficulty with sampling the emitted volatiles with sufficient time resolution to investigate e.g. the effect of rapid heating of the nozzle, and so the available data mostly describes either the total emission of particular VOCs during printing, or the time-resolved emission of total VOCs, without the determination of particular compounds [2,3]. In order to bridge this gap, we have previously demonstrated that proton transfer reaction mass spectrometry (PTR-MS) can be used to monitor the emission of volatiles during 3D-printing in real-time, both qualitatively and quantitatively [4]. Here, we propose to combine this approach with the concurrent real-time measurement of the corresponding emission of particles to obtain a more detailed understanding of the profile of pollutants generated during 3D-printing and the factors which determine this process.

Black diamond powder: On the thermal oxidation and surface graphitization

Oxidation and graphitization are among the most interesting thermochemical characteristics of diamond to be explored. This is due to the influence of these phenomena on either degradation or promotion of the critical properties of diamonds. This article investigates the oxidation and graphitization of diamond powder using thermal analysis combined with X-ray diffraction, Raman spectroscopy, electron microscopy and bulk-electrical conductivity measurements. To this end, the thermokinetic characteristics of micrometre-sized diamond crystals with dominant (1 1 1) facet are investigated at various heating rates from 1 to 100 °C min−1, and the oxidation activation energy is determined to be 135.7 kJ mol−1. In contrast with thermal oxidation, the facile surface graphitization of diamond crystals is also studied as a possible way to promote the electrical conductivity of diamonds without affecting their bulk properties. This surface phase transition involves minimum atomic diffusion, with the crystalline relationship between the interfacial phases described as (0 0 2) graphite || (1 1 1) diamond. The surface-graphitized diamonds, which are black in appearance, exhibit a high value of electrical conductivity of 2100 S m−1. The effect of rapid heating is also confirmed using nanodiamond precursor. This article suggests an ultra-fast and economical method for surface graphitization of diamond crystals, enhancing their electrical performance.

Effects of rapid heating and uniaxial loading on the phase transformation and mechanical properties of direct partial remelted butt joint of AISI D2 tool steel

Tool steels are widely used in various industries, such as automotive, shipbuilding, manufacturing, and marine, for rolling mills, blanking metals, and punching dies, given their distinctive hardness, resistance to abrasion, and deformation. However, joining tool steels using the conventional fusion welding process is difficult because of the formation of dendritic structures and hot cracking, which affect the strength of joining. Therefore, this study proposed the direct partial remelting process (DPRMP) for the butt joining of AISI D2 tool steel. Moreover, different uniaxial loads of 0, 0.5, 2.5, and 5 N were applied during the joining process to investigate the microstructural evolution and mechanical properties of DPRMP samples. Results showed that the ferrite phase in the base material was changed to the austenite phase with globular shape in the joined samples through DPRMP. In addition, increasing the uniaxial load from 0 N to 5 N reduced the average grain size, increased the shape factor, and caused joining defects, such as voids, to disappear. Furthermore, the tensile strength of the DPRMP samples improved by increasing uniaxial loading from 0 N to 5 N due to the effect of grain boundary diffusion and the decrease in eutectic carbide at the joint interface. The highest tensile strength was achieved in DPRMP-5, with a value of 652 MPa and a welding efficiency of 103%. Moreover, the average hardness value of the fusion zone improved in the DPRMP samples and increased to 400 HV wherein the as-received material presented a value of 226 HV.

Review of pool boiling critical heat flux (CHF) and heater rod design for CHF experiments in TREAT

Preventing the occurrence of a departure from nucleate boiling (DNB) event is an important aspect of nuclear safety in pressurized water reactors (PWRs). This phenomenon is partially governed by the cladding-to-coolant heat transfer under transient irradiation conditions, such as during a reactivity-initiated accident (RIA). Currently, there are large uncertainties about cladding-to-coolant heat transfer under these rapid transient conditions. This effort aims to elucidate the mechanisms of CHF under in-pile fast transient irradiation conditions using the Transient Reactor Test (TREAT) facility. These experiments will be carried out under pool boiling conditions, within experimental capsules that will be inserted into the TREAT reactor. A heater rodlet made from stainless steel 304 with tailored natural boron content will be usedin these experiment capsules to induce CHF when submitted to a TREAT power pulse. We will investigate the impacts of the presence of an oxide layer, radiation-induced surface activation (RISA), heat transfer time constant, and rapid surface heating effects on the CHF phenomenon.We review the parameters with significant effects governing the predictions of pool boiling CHF. Only CHF influencing parameters that are highly important, among them coolant subcooling and pressure, as well as oxide layer thickness, RISA, and rapid heating effects were included in this literature assessment.Preliminary neutronics and thermal hydraulic results from the design of the experimental apparatus are also presented in this paper. To aid in the modeling approach, the energy deposition and occurrence of CHF were identified as the most crucial key Figures of Merit (FoMs).In the heater rod design, boron concentrations between 0.1 and 2.09 wt% were considered. Further, a self-shielding study was performed to determine whether an instrumented borated tube could be used in place of a solid borated rod. This study determined that the inner region of the rod can be excluded or instrumented without heat generation penalties. Lastly, a thermal-hydraulics sensitivity study determined the lowest limiting boron concentration needed to induce CHF in water with different degrees of subcooling. Additionally, the value of CHF is known to increase during a rapid transient. Therefore, a CHF multiplier sensitivity study determined what multipliers would inhibit CHF for varying degrees of subcooling of two chosen power coupling factors (PCFs). The current borated tube rodlet geometry configuration achieved a maximum CHF multiplier value of 7.8 using a 1400 MJ power pulse in TREAT. Although this was the power pulse with the greatest energy deposition considered for this study, the TREAT facility is capable of pulses up to ~2500 MJ. This provides a significant margin in energy capacity that was not included within the scope of the calculations carried out to date.The application of the heater rod design was successfully demonstrated in initial experiments in December 2019. The results of these experiments will be explored in future publications.

Austenite Grain Ultra-refinement of 42CrMo Steel Induced by Electropulsing Treatment

With the increasing demands for steel products with both higher strength and toughness to meet the requirements for weight reduction and security promotion, steels with fine grained microstructures cannot meet the application demands any more, and should be further strengthened without toughness or other property loss, such as fatigue lifetime. Ultragrain refinement is a promising way to strengthen steels without toughness loss. For steels with the final bainite, martensite or tempered martensite structures, microstructure refinement basically depends on the prior austenite grain size reduction. In this study, electropulsing treatment (EPT) was used to refine the austenite grain, because pulse current shows remarkable influence on microstructure of metallic material. Results in this study confirm that the prior austenite grains (PAGs) can be ultra-refined by pulse current. When the steel was quenched from peak temperature less than about 850°C during EPT, the average PAGs size was less than 5μm. With the increasing of peak temperature during EPT, the PAGs became coarsening. But the PAGs in samples quenched from peak temperatures less than 1000° were still finer than that quenched from recommend 850° during conventional heat treatment (CHT). EPT induced grain refinement is related to the thermal effect and athermal effect of high density pulse current. The thermal effect results in high heating rate as high as 7700°C/s. In order to analysis the influences of rapid heating effect and athermal effect of pulse current itself on the grain refinement, J Mat Pro software was used to calculated the PAGs size at the same heating rate as that during EPT, which represented the nucleation rate and grain size only under the influence of thermal effect related to rapid heating. However, the simulated result shown the PAGs cannot be ultra-refined during simplex rapid heating. This reveals that the athermal effect of high density electric current itself plays a key role in the EPT induced austenite grain ultra-refinement.

The Effect of Rapid Heating and Fast Cooling on the Transformation Behavior and Mechanical Properties of an Advanced High Strength Steel (AHSS)

The major goal of this work was to study the effect of rapid heating and fast cooling on the transformation behavior of 22MnB5 steel. The effect of the initial microstructure (ferrite + pearlite or fully spheroidized) on the transformation behavior of austenite (during intercritical and supercritical annealing) in terms of heating rates (2.5, 30 & 200 °C/s) and fast cooling, i.e., 300 °C/s rate, were studied. As expected, the kinetics of austenite nucleation and growth were strongly related to the heating rates. Similarly, the carbon content of the austenite was higher at lower intercritical annealing temperatures, particularly when slower heating rates were used. The supercritical temperatures used in this study were similar to those used during commercial hot stamping operations, i.e., 845 and 895 °C, respectively, followed by a fast cooling rate. The prior austenite grain size (PAGS) was not strongly influenced by the nature of the initial microstructure, heating rate, reheating temperatures (845 or 895 °C), at 30 s holding time. The decomposition of austenite using fast cooling rates was examined. The results showed that 100% martensite was not obtained. The observed low temperature transformation products consisted of mixtures of martensite-bainite plus undissolved Fe3C carbides and small amounts of martensite-austenite (M-A). At higher supercritical temperatures, i.e., 1000 °C and 1050 °C, the final microstructure showed an increase in the volume fraction of martensite and a decrease in the volume fraction of bainite. The Fe3C and the M-A microconstituent were not observed. The best combination of tensile properties was obtained on samples reheated in the lower temperature range (845 to 895 °C). Interestingly, when the samples where reheated at the higher temperature range (1000 to 1050 °C) and fast cooled, the results of the mechanical properties did not exhibit significantly higher strength levels independent of heating rate or initial microstructural condition. This can be attributed to the change in the microstructural balance %martensite+%bainite as the reheating temperature increases. The results of this study are presented and discussed.

Microscopic heat pulses activate cardiac thin filaments.

During the excitation-contraction coupling of the heart, sarcomeres are activated via thin filament structural changes (i.e., from the "off" state to the "on" state) in response to a release of Ca2+ from the sarcoplasmic reticulum. This process involves chemical reactions that are highly dependent on ambient temperature; for example, catalytic activity of the actomyosin ATPase rises with increasing temperature. Here, we investigate the effects of rapid heating by focused infrared (IR) laser irradiation on the sliding of thin filaments reconstituted with human α-tropomyosin and bovine ventricular troponin in an in vitro motility assay. We perform high-precision analyses measuring temperature by the fluorescence intensity of rhodamine-phalloidin-labeled F-actin coupled with a fluorescent thermosensor sheet containing the temperature-sensitive dye Europium (III) thenoyltrifluoroacetonate trihydrate. This approach enables a shift in temperature from 25°C to ∼46°C within 0.2 s. We find that in the absence of Ca2+ and presence of ATP, IR laser irradiation elicits sliding movements of reconstituted thin filaments with a sliding velocity that increases as a function of temperature. The heating-induced acceleration of thin filament sliding likewise occurs in the presence of Ca2+ and ATP; however, the temperature dependence is more than twofold less pronounced. These findings could indicate that in the mammalian heart, the on-off equilibrium of the cardiac thin filament state is partially shifted toward the on state in diastole at physiological body temperature, enabling rapid and efficient myocardial dynamics in systole.

Ultrastructure of potato starch granules as affected by microwave treatment

ABSTRACTThe effect of microwave heating on the lamellar ultrastructure of potato starch granules was studied using small-angle X-ray scattering (SAXS), and the linear correlation function was generated from SAXS data to obtain the parameters of the lamellar repeats architecture. To investigate how the molecular vibration of the microwaves influences the lamellar structure during heating, rapid convection heating was applied through an oil bath for comparison. The results showed that the samples subjected to the microwave and the rapid convection heating displayed similar data, which could demonstrate that the effect of microwave heating on submicroscopic structure of potato starch may be mainly due to its rapid heating effect.

Effect of thermal damage on mineralogical and strength properties of basic volcanic rocks exposed to high temperatures

In this study, the engineering behaviors of rocks exposed to temperatures ranging from 200 to 1000 °C were investigated and changes in the geomechanical properties, as well as related mineralogical changes, were examined. To reduce the effect of rapid heating and prevent the formation of new thermo-mechanical cracks, a heating rate of 10 °C/min was used. In addition, a heating time of 2 h was applied for each temperature degree to observe the thermal heating effect. After heating, the samples were left to cool to room temperature, both dry or immersed in water. The strength of the samples gradually decreased from 128 to 25 MPa with increasing temperature. The strength value decreases by about 70% for the samples cooled in air and by about 80% when cooled in water. The strength decrease was greater for the water-cooled samples because of new microcracks and glass material formed during sudden cooling. The effect of different temperature degrees on rock samples was evaluated separately and approximately 80% of total strength decrease occurred in the 600–700 °C range. Also, new mineral formation and melting of the existent minerals were not observed, although the structural properties were significantly changed at these temperatures. At 800 °C and above, some secondary minerals (e.g., melilite and augite) were formed. Partial melting was seen at temperatures higher than 1000 °C. In the study, a predictive model as a function of the strength for determination of thermal damage on rocks was also suggested. Some equations characterized by a correlation coefficient of 96% were suggested, based on the curves of thermal damage, to predict the uniaxial compressive strength for the designed temperature.

A facile synthesis of boron nitride nanosheets and their potential application in dye adsorption

A facile approach was developed to prepare boron nitride nanosheets (BNNSs) by directly exfoliating hexagonal boron nitride (h-BN) intercalated with concentrated H2SO4, subsequently the rapid heating effect of H2SO4 mixing with water. The obtained BNNSs were characterized. It was demonstrated that bulk h-BN powder was successfully exfoliated by this new method. Transmission electron microscopy and atomic force microscopy confirmed that the obtained BNNSs mainly consisted of few-layer sheets with a thickness range 1–2nm, corresponding to 3–6 layers. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy revealed that the oxidation did not occur in BNNSs during the concentrated H2SO4-intercalated exfoliation process. It was directly observed that the resultant BNNSs could be well dispersed in water. The adsorption performance of the BNNSs for Rhodamine B were then studied. Compared with the bulk BN, BNNSs showed superiority in adsorption ability. And the adsorption capacity of BNNSs was about 2 times that of h-BN.

Effect of Rapid Heating on a Cold-Rolled Mn–Al Transformation-Induced Plasticity Steel with Coarse Delta-Ferrite

Effect of Rapid Heating on a Cold-Rolled Mn–Al Transformation-Induced Plasticity Steel with Coarse Delta-Ferrite

Effects of Heating and Cooling Rates on Phase Transformations in 10 Wt Pct Ni Steel and Their Application to Gas Tungsten Arc Welding

10 wt pct Ni steel is a high-strength steel that possesses good ballistic resistance from the deformation induced transformation of austenite to martensite, known as the transformation-induced-plasticity effect. The effects of rapid heating and cooling rates associated with welding thermal cycles on the phase transformations and microstructures, specifically in the heat-affected zone, were determined using dilatometry, microhardness, and microstructural characterization. Heating rate experiments demonstrate that the Ac3 temperature is dependent on heating rate, varying from 1094 K (821 °C) at a heating rate of 1 °C/s to 1324 K (1051 °C) at a heating rate of 1830 °C/s. A continuous cooling transformation diagram produced for 10 wt pct Ni steel reveals that martensite will form over a wide range of cooling rates, which reflects a very high hardenability of this alloy. These results were applied to a single pass, autogenous, gas tungsten arc weld. The diffusion of nickel from regions of austenite to martensite during the welding thermal cycle manifests itself in a muddled, rod-like lath martensitic microstructure. The results of these studies show that the nickel enrichment of the austenite in 10 wt pct Ni steel plays a critical role in phase transformations during welding.

Investigations of the long-term effects of LII on soot and bath gas

A combination of high-repetition rate imaging, laser extinction measurements, two-colour soot pyrometry imaging, and high-resolution transmission electron microscopy of thermophoretically sampled soot is used to investigate the long-term and permanent effects of rapid heating of in-flame soot during laser-induced incandescence (LII). Experiments are carried out on a laminar non-premixed co-annular ethylene/air flame with various laser fluences. The high-repetition rate images clearly show that the heated and the neighbouring laser-border zones undergo a permanent transformation after the laser pulse, and advect vertically with the flow while the permanent marking is preserved. The soot volume fraction at the heated zone reduces due to the sublimation of soot and the subsequent enhanced oxidation. At the laser-border zones, however, optical thickness increases that may be due to thermophoretic forces drawing hot particles towards relatively cooler zones and the rapid compression of the bath gas induced by ...