Fast Heating Rate Research Articles

Numerical modeling and parametric analysis of temperature distribution in soil based on water content variation under radio frequency heating for in-situ thermal remediation

Radio frequency heating (RFH) is recognized as an efficient and economical method for volatilizing organic pollutants from contaminated soils. Although some numerical simulations have been conducted to predict temperature changes during RFH, models that account for effects of water content (WC) variation on dielectric properties and temperature evolution in soil were rarely reported. To address this, a three-dimensional numerical model integrating electromagnetic-thermal conversion, heat transfer, and mass transfer was developed with coupling dynamic changes in WC and corresponding impacts on soil properties. The effects of soil types and RFH engineering parameters on temperature evolution and energy utilization were evaluated. The model's temperature prediction was validated using experimental data, indicating that temperature decreases outward from hot electrode, with high-temperature regions forming at the top and bottom regions near electrode. Water evaporation in soil causes a temperature plateau with >76.25 % of energy utilized for heating and evaporating water during 60-d RFH. Moreover, higher soil WC could increase electromagnetic-thermal conversion capability, counteracting the negative impact of increased specific heat capacity on temperature rise. Thermophysical properties of soil are crucial in RFH: sand, with lower specific heat capacity and higher thermal conductivity, results in faster heating rates. While, clay, with higher density and specific heat capacity, results in lower heating rates but greater energy utilization efficiency. Low-power RHF and wider well spacing improve the uniformity of temperature distribution but require more time to reach target temperatures. Moreover, input power influences the magnitude and timing of optimal energy utilization efficiency, while well spacing primarily affects timing. The models developed in this study provide essential guidance for RFH-based soil remediation projects.

Thermal Decomposition and Kinetic Analysis of Amazonian Woods: A Comparative Study of Goupia glabra and Manilkara huberi

This study presents a detailed analysis of the thermal degradation and kinetic behavior of two Amazonian wood species, Goupia glabra (cupiúba) and Manilkara huberi (maçaranduba), using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR-ATR), and direct infusion mass spectrometry (DIMS). Wood samples were subjected to controlled heating rates of 20, 40, and 60 °C/min from 25 to 800 °C under an argon atmosphere. TGA revealed moisture evaporation below 120 °C, with hemicellulose degradation occurring between 220 and 315 °C, cellulose decomposition between 315 and 400 °C, and lignin breakdown over a broader range from 180 to 900 °C. The highest rate of mass loss occurred at 363.99 °C for G. glabra and 360.27 °C for M. huberi at a heating rate of 20 °C/min, with shifts to higher temperatures at faster heating rates. Activation energies were calculated using Arrhenius and Kissinger models, yielding values between 53.46–61.45 kJ/mol for G. glabra and 58.18–62.77 kJ/mol for M. huberi, confirming their stable thermal profiles. DSC analysis identified a significant endothermic peak related to moisture evaporation below 100 °C, followed by two exothermic peaks. For G. glabra, the first exothermic peak appeared at 331.45 °C and the second at 466.08 °C, while for M. huberi, these occurred at 366.41 °C and 466.08 °C, indicating the decomposition of hemicellulose, cellulose, and lignin. Enthalpy values for G. glabra were 12,633.37 mJ and 18,652.66 mJ for the first and second peaks, respectively, while M. huberi showed lower enthalpies of 9648.04 mJ and 14,417.68 mJ, suggesting a higher energy release in G. glabra. FTIR-ATR analysis highlighted the presence of key functional groups in both species, with strong absorption bands in the 3330–3500 cm−1 region corresponding to O-H stretching vibrations, indicative of hydroxyl groups in cellulose and hemicellulose. The 1500–1600 cm−1 region, representing aromatic C=C vibrations, confirmed the presence of lignin. Quantitatively, these results suggest a high content of cellulose and lignin in both species. DIMS analysis further identified polyphenolic compounds and triterpenoids in M. huberi, with major ions at m/z 289 and 409, while G. glabra showed steroidal and polyphenolic compounds with a base peak at m/z 395. These findings indicate the significant presence of bioactive compounds, contributing to the wood’s resistance to microbial degradation. This comprehensive thermal and chemical characterization suggests that both species have potential industrial applications in environments requiring high thermal stability.

Experimental Study on Phase Change Energy Storage Flooring for Low-Carbon Energy Systems in Grassland Pastoral

Phase change energy storage technology enhances the integration of renewable resources into low-carbon energy systems for grassland pastoral settlements, further addressing the balance between energy needs and environmental sustainability. This study examines a heating system using an experimental platform in an environmental chamber, where the thermal storage and release processes of phase change energy storage flooring were monitored. The results revealed that phase change energy storage flooring exhibits higher heat transfer efficiency and faster heating rates. Under 40 °C heating conditions, the heating rate of the thermal storage layer increased by 12.5% within 1 h. The flooring also demonstrated superior heat release performance, with the peak heat flux of the thermal storage layer delayed by 15 min. Higher heating temperatures shortened the heating time and extended the heat release duration of the phase change energy storage flooring. Under 45 °C heating conditions, the heat transfer efficiency of the surface temperature of the thermal storage layer increased by 38% within 1 hour and by 24.7% over 4 h. In addition, energy consumption in different tests was analyzed, and thermal conductivity was discussed according to the heat transfer model. Phase change energy storage flooring, when coupled with the abundant solar energy resources available in grassland pastoral areas, presents a viable option for the construction of low-carbon energy systems in grassland pastoral settlements.

Simulation of electrostatic particulate matter sensor regeneration based on the particulate deposition patterns

Purpose This study aims to establish a multi-physics-coupled model for an electrostatic particulate matter (PM) sensor. The focus lies on investigating the deposition patterns of particles within the sensor and the variation in the regeneration temperature field. Design/methodology/approach Computational simulations were initially conducted to analyse the distribution of particles under different temperature and airflow conditions. The study investigates how particles deposit within the sensor and explores methods to expedite the combustion of deposited particles for subsequent measurements. Findings The results indicate that a significant portion of the particles, approximately 61.8% of the total deposited particles, accumulates on the inside of the protective cover. To facilitate rapid combustion of these deposited particles, a ceramic heater was embedded within the metal shielding layer and tightly integrated with the high-voltage electrode. Silicon nitride ceramic, selected for its high strength, elevated temperature stability and excellent thermal conductivity, enables a relatively fast heating rate, ensuring a uniform temperature field distribution. Applying 27 W power to the silicon nitride heater rapidly raises the gas flow region's temperature within the sensor head to achieve a high-temperature regeneration state. Computational results demonstrate that within 200 s of heater operation, the sensor's internal temperature can exceed 600 °C, effectively ensuring thorough combustion of the deposited particles. Originality/value This study presents a novel approach to address the challenges associated with particle deposition in electrostatic PM sensors. By integrating a ceramic heater with specific material properties, the study proposes an effective method to expedite particle combustion for enhanced sensor performance.

Enhanced post-combustion CO2 capture and direct air capture by plasma surface functionalization of graphene adsorbent

Graphene has enormous potential to capture CO2 due to its unique properties and cost-effectiveness. However, graphene-based adsorbents have drawbacks of lower CO2 adsorption capacity and poor selectivity. This work demonstrates a one-step rapid and sustainable N2/H2 plasma treatment process to prepare graphene-based sorbent material with enhanced CO2 adsorption performance. Plasma treatment directly enriches amine species, increases surface area, and improves textural properties. The CO2 adsorption capacity increases from 1.6 to 3.3 mmol/g for capturing flue gas, and from 0.14 to 1.3 mmol/g for direct air capture (DAC). Importantly, the electrothermal property of the plasma-modified aerogels has been significantly improved, resulting in faster heating rates and significantly reducing energy consumption compared to conventional external heating for regeneration of sorbents. Modified aerogels display improved selectivity of 42 and 87 after plasma modification for 5 and 10 min, respectively. The plasma-treated aerogels display minimal loss between 17% and 19% in capacity after 40 adsorption/desorption cycles, rendering excellent stability. The N2/H2 plasma treatment of adsorbent materials would lower energy expenses and prevent negative effects on the global economy caused by climate change.

Structural and magnetic properties of Mn1.25Fe0.7P0.5Si0.5 alloys prepared by spark plasma sintering using raw materials milled with different lengths of time

Spark plasma sintering (SPS) is an effective method for synthesizing the Fe2P-type alloys due to its fast heating rate and short sintering time. Raw materials in the form of powder are sintered and pressed simultaneously in the preparation. Therefore, the particle size of the powder would have important influences on the structural and magnetic properties of the Fe2P-type alloys. In this work, the structure and magnetic properties of Mn1.25Fe0.7P0.5Si0.5 alloys prepared by SPS using raw materials milled with different lengths of time were investigated. We found that the particle size of the raw materials reduced mainly within milling time of 5 h and only slight difference existed when the milling time exceeded 5 h. Obvious secondary phase of (Mn,Fe)3Si was observed in the alloy prepared with milling time of 1 h. Other alloys prepared with milling time of 2 h, 5 h and 10 h showed similar magnetic properties. Giant isothermal entropy change values of 7.4 ∼ 9.6 J ⋅ kg−1 ⋅ K−1 for a magnetic field change of 1.5 T were obtained near room temperature for the alloys. The results demonstrate that a milling time longer than 2 h is required to obtain such magnetocaloric Mn-Fe-P-Si alloys with excellent magnetic properties using SPS method and the obtained alloys are promising candidates for magnetic refrigeration near room temperature.

A device for dynamic testing of the refractory ceramic resistance to biomass ash

The corrosive effects of biomass ash on refractory materials in combustion chambers pose challenges. Development of new castable refractory materials which are more resistant to corrosion requires tests that accurately reflect the conditions occurring in real devices. This article describes the Computational Fluid Dynamics (CFD) design and construction of a device for evaluating the corrosion of refractory materials in dynamic regime. The device allows to simulate combustion chamber conditions accurately, to regulate an injection of corrosive medium on the tested material surface under the specified conditions (temperature, time, and flow). In the present investigation the conventional refractory material was exposed to attack of biomass ash at the temperature of 1300 °C for 3 h to test the functionality of the device. A burner with technology oxygen–enriched combustion was used to heat the device. The corrosion tests were conducted in accordance with the standard P CEN/TS 15,418 and the standard STN EN ISO 21404. The operational state required for corrosion tests at 1300 °C was achieved within 1.12 h. The extent of refractory material degradation in the dynamic corrosion regime was evaluated using electron microscopy-energy dispersive spectroscopy (EM-EDS) and compared with the results of a static crucible test (3 h at 1300 °C). The dynamic test provided sufficient information on the interactions of corrosion medium with the refractories. Its main advantages are the maintenance of non-equilibrium conditions by controlled deposition of the corrosion medium in quantity from 1 to −100 g/h, fast heating rate to operating temperature (20 °C/min), and the possibility of conditions variability during tests (temperature, ox-red. atmosphere, fuel gas flow etc.).

Experimental and kinetic study of PET pyrolysis under fast and slow heating rates using a visualized Macro TGA

A visualized macro thermogravimetric analyzer was utilized to gather data on sample weight, temperature, and image signals of centimeter-scale PET. The PET was subjected to both fast (above 300 K/min) and slow (below 25 K/min) heating rates. The experimental findings revealed that weight loss mainly occurred at different temperature ranges under fast (above 610 °C) and slow (400–520 °C) heating rates. The isoconversional method (ICM) and the distributed activation energy model (DAEM), both assuming single-step reactions, were employed separately to predict the conversion and rate of PET pyrolysis. However, the prediction error was considerable. To address this issue, a discrete distributed activation energy model (DDAEM) was developed, incorporating both single-step and double-step parallel reactions. The DDAEM yielded a prediction error within 10 %, which is better than ICM and DDAEM. Furthermore, all three models (ICM, DAEM, and DDAEM) indicated significant discrepancies in activation energies between fast and slow heating rates.

Synthesis of Molybdenum Oxide Nanofibers with Multiple Surface Facets Via Electropsinning Followed by Rapid Thermal Treatment

A MoO3 nanofiber prepared by electrospinning and subsequent heat treatment is attracting significant attention due to its structural advantages. Vibrant studies are being conducted to control its morphology and diameter to improve its properties. In this study, we demonstrated the synthesis of α-MoO3 nanofibers with multiple surface facets by controlling the heating rate and temperature in the heat treatment step for removing polymer and crystallizing MoO3 from the electrospun polymer/precursor nanofibers. The analysis results show that the faster heating rate and higher heat treatment temperature in the thermal treatment process are more favorable for forming a shape in which particles with facet planes are connected. Finally, we observed the morphological change according to the heat treatment time to confirm the effect of the heat treatment conditions on the shape of MoO3 and interpreted the results in terms of nucleation and crystal growth.

Experimental Study on Microwave Pyrolysis of Decommissioned Wind Turbine Blades Based on Silicon Carbide Absorbents

The rapid expansion of the scale of wind power has led to a wave of efforts to decommission wind turbine blades. The pyrolysis of decommissioned wind turbine blades (DWTBs) is a promising technological solution. Microwave pyrolysis offers the benefits of fast heating rates and uniform heat transfer, making it a widely used method in various heating applications. However, there are few studies on the microwave pyrolysis of DWTBs, and pyrolysis characteristics under different boundary conditions remain unclear. In this paper, we investigate the pyrolysis characteristics of DWTBs by utilizing silicon carbide (SiC) particles as a microwave absorbent. The results demonstrated that, when the microwave heating power increased from 400 W to 600 W, the heating rate and pyrolysis final temperature of the material increased, resulting in a reduction in pyrolysis residual solid yield from 88.30% to 84.40%. At 600 W, pyrolysis gas components included C2H4, CH4, and CO, while the tar components included phenol and toluene. The highest degree of pyrolysis was achieved under the condition of an SiC particle size of 0.85 mm, with better heating performance, and the calorific value of the pyrolysis gas generated was 36.95 MJ/Nm3. The DWTBs did not undergo pyrolysis when SiC was not added. However, when the mass ratio of SiC to DWTBs was 4, the tar yield was 4.7% and the pyrolysis gas yield was 17.0%, resulting in a faster heating rate and the highest degree of pyrolysis. Based on this, an optimal process for the microwave pyrolysis of DWTBs was proposed, providing a reference for its industrial application.

Flame Spray Pyrolysis Synthesis of Ultra-Small High-Entropy Alloy-Supported Oxide Nanoparticles for CO2 Hydrogenation Catalysts.

The synthesis of high-entropy alloys (HEAs) with ultra-small particle sizes has long been a challenging task. The complex and time-consuming synthesis process hinders their practical application and widespread adoption. This study presents the novel synthesis of TiO2 nanoparticles loaded with a quinary high-entropy alloy through flame spray pyrolysis (FSP) for the first time. The extremely fast heating rate of flame combustion makes the precursor fast pyrolysis gasification, high temperature in the flame field promotes the metal vapor mixing uniformly, and the fast quenching process can reduce the particle aggregation sintering, the ultra-small particle size of HEA firmly attached to the TiO2 surface. The catalysts prepared via this gas-to-particle pathway exhibit excellent performance in CO2 hydrogenation, achieving a conversion rate of 62% at 450°C, and maintaining their activity for over 220h without significant particle agglomeration. This finding provides valuable insights for the future design of catalytically active materials with enhanced activity and long-term stability.

Continuous flow synthesis of hierarchical low silica X zeolite

Zeolites, renowned for their versatile applications in catalysis, adsorption, and ion exchange, have long been synthesized using conventional batch processes. However, the inherent limitations of these methods, such as resource-intensive conditions and inconsistent product quality, underscore the need for a sustainable and efficient approach. In this study, a continuous flow synthesis process was established for the synthesis of industrially important low silica X (LSX) zeolite using a tubular reactor. The synthesis gel was subjected to aging for 5 days at room temperature to facilitate nucleation and crystal growth combined with the fast-heating rate in a tubular reactor at 363 K & 1.1 atm., which in turn produces LSX after 40 min. The synthesized product was confirmed by the XRD, FE-SEM, EDS, XRF, TEM, and N2 adsorption-desorption; the data was compared with the LSX sample synthesized by batch process. The result implies that LSX prepared by continuous flow has a pure phase of LSX with the hierarchical structure, which provides better adsorption capacity of CO2 at 298 K up to 20 bar. Due to continuous flow synthesis, the crystallization time was reduced and faster kinetics which may be helpful for scale-up the process for LSX synthesis.

Pyrolysis of macroalgae: Insight into product yields and biochar morphology and stability

Pyrolysis of biomass residues into biochar is seen as a feasible way to mitigate climate change by biological carbon storage (carbon dioxide removal, CDR) and to substitute fossil fuel with sustainable biofuel. This study applies a combination of flash and ramp heating pyrolysis, and organic petrography to investigate the hydrocarbon (biofuel) potential and biochar stability and morphotypes of eight brown, red, and green macroalgal species of different tissue complexity. The carbon stability of biochar derived from macroalgae has not previously been assessed using organic petrography (reflectance measurements) and evaluated in the context of the geological carbon cycle. The biochar, hydrocarbon, and CO + CO2 yields vary due to different chemical composition of the macroalgal species, but the product yield variations are not related to the brown, red, or green macroalgal groups. The total biofuel yield shows an inverse trend with biochar yield. A slower heating rate produces more biochar and higher CO + CO2 and lower biofuel yields than the combined flash pyrolysis and faster heating rate. The morphotype composition of the biochar was qualitatively examined by reflected light microscopy while carbon stability was assessed by random reflectance (Ro) measurements. The diverse morphotype compositions observed in biochar formed under similar pyrolysis conditions likely stem from variations in the original algal composition. While some biochar samples show morphologies resembling the original macroalgal structure, porous morphotypes predominantly characterize the biochar samples overall. Despite a maximum pyrolysis production temperature (PT) of 650 °C, the highest mean Ro value among all biochar samples is 2.91%, corresponding to a carbonization temperature (CT) of 526 °C. This observation is tentatively related to the less lignocellulosic structure of the macroalgae compared to terrigenous biomass. Four biochar samples have their entire Ro distribution range above the inertinite benchmark (IBRo2%) of Ro = 2% indicating high carbon stability. Conversely, the remaining four biochar samples exhibit Ro distributions extending below IBRo2%, indicating the presence of a carbon fraction with lower long-term stability in soil. The statistically significant inverse relationship observed between the mean Ro values and the peak hydrocarbon generation temperature (Tmax) can be attributed to the behavior of residual macromolecules within the biochar. When these macromolecules reach peak biofuel generation at a lower temperature, they undergo carbonization over a more extended time interval during pyrolysis. Consequently, this prolonged exposure to the pyrolysis process leads to higher degrees of carbonization, as reflected by higher Ro values. In conclusion, the findings from pyrolysis and organic petrography reveal: (1) Macroalgae demonstrate potential for biofuel production, although biofuel yields contingent upon both the species of macroalgal and the heating rate employed, and (2) This study documents for the first time that flash+ramp pyrolysis of macroalgae yields biochar suitable for long-term carbon storage. However, both the carbon stability inferred from Ro frequency distributions and biochar yields show variations across different macroalgal species and heating rate.

Influence of rapid high-temperature processing on the interface of CF/PEEK, a quick and effective method for enhancing the IFSS

This study explores the effect of rapid high-temperature processing on the interface of carbon fibre (CF) reinforced poly-ether-ether-ketone (PEEK). Specimens that have been thermally treated at slower and faster heating rates and specimens that have not been post-manufacturing treated (virgin) are examined with single fibre pull-out tests. A comparison between their interfacial shear strength (IFSS) and their failure modes takes place. Scanning electron microscopy is used to assess the surface morphology of the thermally treated specimens, and partly cross-polarised microscopy is employed to investigate the development of transcrystallinity. Furthermore, to identify the extent of thermal degradation the specimens are examined with attenuated total reflection Fourier transform infrared spectroscopy. At faster heating rates, an improved interfacial adhesion up to 25% is found at temperatures where a low-level thermal damage is induced. At higher temperatures and despite the increased thermal damage, an IFSS increase of up to 10% is still identified. This is due to the beneficial formation of thermal residual stresses upon high-temperature processing, and overall, especially rapid high-temperature processing could effectively serve for enhancing the interface properties of CF/PEEK.

Effect of fast heating rate and alkaline catalyst on composition and characteristic of volatile products during catalytic upgrading of oil sand bitumen

The study was devoted to exploring the fundamental study on the upgrading of Buton oil sand bitumen (OSB) via fast alkaline catalytic pyrolysis based on the fluid pyrolysis technology. The effect of fast heating rate on the composition and molecular distribution of volatile products from the high-temperature fast pyrolysis of OSB was investigated by Py-GC/TOF-MS that could simulate the fast heating rate of industrial fluid pyrolysis process. The results showed that the volatile products of OSB under heating rates ranging from 10 to 1000 °C/s had the similar species composition. It was found that there were the highest relative content of low-carbon alkenes (C2-C4) and light aromatics (C6-C8) in volatile products under the 1000 °C/s, indicating that the fast heating rate favored the production of light alkenes and aromatics. Subsequently, a laboratory-scale fluidized bed apparatus was employed to further gain insight into fast alkaline catalytic pyrolysis behaviors of OSB. The investigation on the yield distribution, fractional- and molecular-level chemical characteristic of volatile products obtained from the fast alkaline catalytic upgrading of OSB over calcium aluminate was carried out with the aid of the comparison with that over Y zeolite-based FCC catalyst and silica sand. The results revealed that three-phase products over calcium aluminate possessed the larger selectivity of C2−C4 alkenes, larger yield of light oil and the lower coke output, which were 51.88%, 45.49% and 7.96%, respectively. On basis of the chemical structure analysis of liquid products, the alkaline catalytic upgrading of OSB over calcium aluminate could heighten the content of chain alkyl structures as well as alkyl-substituents attached to aromatic ring in liquid products. This indicated that the fast heating rate and alkaline catalyst that adopted in catalytic upgrading process of OSB could play an energetic role in optimizing the composition of volatile products. The alkaline catalytic upgrading of OSB based on fluid pyrolysis technology with the fast heating rate could heighten the yield of low-carbon olefins and light oil and lessen coke yield, meanwhile modify the chemical structure characteristics of liquid products that were conducive to the generation of valuable chemicals (light alkanes and BTX) during secondary processing of liquid products.

Ab Initio and Kinetic Modeling of β-d-Xylopyranose under Fast Pyrolysis Conditions.

Lignocellulosic biomass is an abundant renewable resource that can be upgraded to chemical and fuel products through a range of thermal conversion processes. Fast pyrolysis is a promising technology that uses high temperatures and fast heating rates to convert lignocellulose into bio-oils in high yields in the absence of oxygen. Hemicellulose is one of the three major components of lignocellulosic biomass and is a highly branched heteropolymer structure made of pentose, hexose sugars, and sugar acids. In this study, β-d-xylopyranose is proposed as a model structural motif for the essential chemical structure of hemicellulose. The gas-phase pyrolytic reactivity of β-d-xylopyranose is thoroughly investigated using computational strategies rooted in quantum chemistry. In particular, its thermal degradation potential energy surfaces are computed employing Minnesota global hybrid functional M06-2X in conjunction with the 6-311++G(d,p) Pople basis set. Electronic energies are further refined by performing DLPNO-CCSD(T)-F12 single-point calculations on top of M06-2X geometries using the cc-pVTZ-F12 basis set. Conformational analysis for minima and transition states is performed with state-of-the-art semiempirical quantum chemical methods coupled with metadynamics simulations. Key thermodynamic quantities (free energies, barrier heights, enthalpies of formation, and heat capacities) are computed. Rate coefficients for the initial steps of thermal decomposition are computed by means of reaction rate theory. For the first time, a detailed elementary reaction kinetic model for β-d-xylopyranose is developed by utilizing the thermodynamic and kinetic information acquired from the aforementioned calculations. This model specifically targets the initial stages of β-d-xylopyranose pyrolysis in the high-pressure limit, aiming to gain a deeper understanding of its reaction kinetics. This approach establishes a systematic strategy for exploring reactive pathways, evaluating competing parallel reactions, and selectively accepting or discarding pathways based on the analysis. The findings suggest that acyclic d-xylose plays a significant role as an intermediary in the production of key pyrolytic compounds during the pyrolysis of xylose. These compounds include furfural, anhydro-d-xylopyranose, glycolaldehyde, and dihydrofuran-3(2H)-one.

Effect of Gradient Heat Conduction on Secondary Recrystallization of Grain-Oriented Silicon Steel

The grain-oriented silicon steels were subjected to gradient heat conduction during high-temperature annealing by using thermal insulation cotton. The macrostructures of samples subjected to circumferential gradient heat conduction showed a “petal-like” morphology with peripheral columnar grains and central equiaxed grains, while samples subjected to transverse gradient heat conduction showed a morphology with approximately 50% columnar grains and 50% equiaxed grains. The grain orientations, magnetic domains as well as magnetic properties in different regions were detected. Results showed that the magnetic induction intensity of cylindrical grains was better than that of equiaxed grains while the iron loss was worse, which indicated that a fast heating rate during high-temperature annealing was conducive to the accuracy of Goss grains. The magnetic domains in columnar grains were wider than the equiaxed grains, which resulted in poorer iron loss. A theory of the competitive growth among secondary Goss grains was proposed. Under the condition of gradient heat conduction, once the Goss grains with the fastest heat conduction grew up abnormally, they would compete with other Goss grains which were supposed to survive in traditional processes and swallow up them until adjacent to the secondary equiaxed grains which were later developed.

Transparent Structures with a Fast De‐Stiffening Functionality

The majority of natural organisms interact with their environments with a degree of mechanical adaptability that allows them to carry out a variety of tasks and adapt to changing circumstances. Human‐made structures, however, lack this versatility and are normally designed to fulfill a certain load‐carrying requirement. This causes limitations in performance, efficiency, and safety. The aim of this article is to present rapid de‐stiffening in the response of conventional structures, without compromising the load‐bearing capacity. This has been achieved by developing an active interface using an interconnected nanostructured metallic network. A very fast heating rate with an average of ≈45 °C s−1 under 4.8 V excitation while retaining transparency of 67% is demonstrated. The embedded metallic network in a thermoplastic matrix has been deployed as an active interface, in a conventional transparent multilayered structure. Upon activation, it provides a rapid (i.e., 2 s after activation) mechanical de‐stiffening capability. The results from finite element modeling have been found to be in good agreements with those from experiments. The rapid reversible stiffness tuning demonstrated here can be implemented in variety of multilayered structures with a wide range of applications in robotics, morphing and deployable structures, active damping, and active impact safety systems.

Heat transfer characteristics of micro-droplet impacting on high-temperature wall in pyrolysis of methyl ricinoleate

The rapid heating of the material is a key factor in the pyrolysis of methyl ricinoleate, which is mainly affected by the droplet size and velocity of methyl ricinoleate droplet impacting on high-temperature wall. The process of millimeter-droplet of methyl ricinoleate impacting on high-temperature wall at different droplet sizes and velocities were studied by high-speed photography technology and multiphysics simulation. The simulation results were basically consistent with the experimental results. Based on this model, the process of micro-droplet impacting on high-temperature wall was investigated, obtaining the heat rates of droplet at different droplet sizes and velocities. The processes of 38 ~ 58 ?m droplet impacting on high-temperature wall at velocity of 10 ~ 30 m/s were investigated. As the droplet at the initial temperature of 27 ?C and droplet size of 38 ?m impacting on a high-temperature wall of 480 ?C at a speed of 20 m/s, the average heating rate of the droplet reached 107 ?/s orders of magnitude. The results showed that faster heating rates were obtained at smaller droplet size and faster droplet velocity. Hence, the rapid heating of the material can be achieved by the micro-droplet impacting on stable high-temperature wall.

Integrating reversion ageing and forming of high-strength Al alloys: Principles and theoretical basis

Simultaneously improving the formability and post-formed strength of high-strength aluminum (Al) alloys, such as Al–Zn–Mg–Cu alloys, is essential in manufacturing complex-shaped panel components. The strict requirements on heat-treatment condition and high tooling costs limit the applications of current forming methods. A novel process called integrated reversion ageing and forming (IRAF) is proposed to form naturally aged (NA or T4 tempered) Al alloys. A principle-based concept analysis and systematic thermo-mechanical-metallurgical study of the IRAF process were performed. Additionally, tensile tests were conducted to evaluate the effects of parameters including heating rate, holding time, and forming temperature on formability and baked strength. The deformability of the AA7075-T4 alloy can be significantly enhanced through rapid heating to the reversion ageing temperature (150–300 °C), followed by short-term holding, as evidenced by the reduced yield strength of 200 MPa and increased uniform ductility. An instant strength increase to a value close to that of the T6 state was obtained after a short bake hardening (BH) treatment. Further, temperature-time-property (TTP) diagrams were established based on the correlation between the measured mechanical properties and through-process microstructure evolution to explain the mechanism underlying the optimised processing window of IRAF. The results indicate that fast-heating rate (>300 °C/min) promotes the reversion of NA clusters and inhibits re-precipitation of solutes, thereby improving the warm formability. Reversion ageing above 240 °C could induce the formation of coarse η'/η phases, leading to a considerably declined BH response. To accurately predict the strength evolution and deformation behavior during IRAF, a physical-based unified constitutive model was constructed by considering the reversion of NA clusters and solute re-precipitation. The bending and drawing tests on the AA7075-T4 alloy sheets verified that IRAF in the most-reverted state enabled optimum formability. The findings inspire promoting the reversion of pre-existing metastable particles to improve warm formability and post-formed age hardening.