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Electrocaloric effects of adiabatic temperature change via the application of external electric fields are explored for energy-efficient solid-state refrigeration. These effects are typically estimated from the thermodynamic analyses of polarization and field in electrocaloric materials, which implies that higher field application gives larger temperature changes. However, this may not be always true. Here, using both indirect and direct methods, we report an anomalous effect where larger thermal changes occur by applications of lower fields in a multi-domain BaTiO3 (001) single crystal. A large temperature change of 1.9 K under a low field change of 8 kV/cm at 404 K is observed in a multi-domain BaTiO3 (001) single crystal in comparison to that of 1.4 K at a high field change of 30 kV/cm. We attribute this counterintuitive effect to the interplay of the c- and a-domains in the BaTiO3 (001) single crystal under the influence of temperature and field changes. This work provides a fundamental understanding of the complex role of domains in governing the electrocaloric response of ferroelectric materials which is often overlooked but critical for their practical applications. [ABSTRACT FROM AUTHOR]

Using commercially available components, a compact laboratory-type prototype has been developed and assembled to demonstrate single and multicaloric effects arising from single and cyclic applications of magnetic fields and uniaxial mechanical loads. Using the example of the LaFe11.4Mn0.3Si1.3H1.6 alloy with a first-order phase transition near room temperature, the possibility of observing magnetocaloric, elastocaloric, and multicaloric effects is demonstrated. It is shown that by selecting protocols for applying combined external influences: magnetic field and mechanical load, it is possible to observe a synergistic effect for adiabatic temperature change, which amounts to 1.17 K (0.31 T and 19 MPa) at a temperature of 291.5 K for the multicaloric effect, which exceeds the corresponding value of |ΔT| = 0.75 K (0.31 T) at a temperature of 291.65 K for the magnetocaloric effect. The proposed approaches and obtained results can be used for the development of new prototypes of multicaloric cooling systems and the optimization of current ones. [ABSTRACT FROM AUTHOR]

Magnetocaloric materials, which exploit reversible temperature changes induced by magnetic field variations, are promising for advancing energy-efficient cooling technologies. The potential integration of two-dimensional materials into magnetocaloric systems represents an emerging opportunity to enhance the magnetocaloric cooling efficiency. In this study, we use atomistic spin dynamics simulations based on first-principles parameters to systematically evaluate how magnetocaloric properties transition from three-dimensional (3D) to two-dimensional (2D) ferromagnetic materials. We find that 2D features such as reduced Curie temperature, sharper magnetic transition, and higher magnetic susceptibility are beneficial for magnetocaloric applications, while the relatively higher lattice heat capacity in 2D can compromise achievable adiabatic temperature changes. We further propose GdSi 2 as a promising 2D magnetocaloric material. Our calculation predicts that GdSi 2 exhibits an isothermal entropy change Δ S M of 22.5 J kg − 1 K − 1 and an adiabatic temperature change Δ T a d of 6.2 K, near the hydrogen liquefaction temperature (T C ≈ 25 K). Our analysis offers valuable theoretical insights into the magnetocaloric effect in 2D ferromagnets and demonstrates that 2D ferromagnets hold promise for cooling and thermal management applications in compact and miniaturized nanodevices. [ABSTRACT FROM AUTHOR]

A magnetocaloric effect (MCE) due to adiabatic change of temperature was directly measured in an Fe47.1Mn26.1Ga26.8 alloy undergoing martensitic transformation. Its values in the high-temperature region were positive, while in the temperature range below temperatures of martensitic transformation, the adiabatic change of temperature in the magnetic field was negative. The x-ray diffraction analysis revealed the presence of a Heusler L21 (B2) phase and a γ-phase in the Fe47.1Mn26.1Ga26.8 alloy above temperature of martensitic transformation. The features of field-dependent magnetization and temperature variation in MCE indicate the occurrence of ferromagnetic-to-antiferromagnetic transition in the γ-phase, which is responsible for the observed inverse magnetocaloric effect. [ABSTRACT FROM AUTHOR]

PbTiO 3 is a prototypical ferroelectric perovskite that is known to undergo a temperature driven ferroelectric tetragonal to paraelectric cubic phase transition, but the understanding of some key phenomena and associated mechanisms underlying this transition remains unclear. Here, using molecular dynamics simulations based on first-principles effective Hamiltonian, we show the behaviors of the phase transition temperature T c and adiabatic temperature change Δ T of PbTiO 3 under an external electric field and tensile stress along the [001] direction. Our results show that the electric field E induces rising T c via a linear relation T c ∝ 0.3083 E , rendering the phase transition to go from first-order with thermal hysteresis to second-order without thermal hysteresis above ∼ 200 kV/cm; meanwhile, a maximum electrocaloric response Δ T m a x ∼ 34 K is obtained under E = 500 kV/cm. Moreover, external stress (σ z) causes rising T c via a linear relation T c ∝ 160 σ z and improves the electrocaloric response Δ T m a x when combined with the electric field. The present results offer insights into the physical processes and mechanisms that dictate finite-temperature properties of ferroelectric perovskite oxides, laying a foundation for further exploration of this intriguing class of materials. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of hexagonally structured Mn 5 − x Fe x Ge 3 (x = 0.15 , 0.3, and 0.5) alloys have been investigated using DC magnetization and heat capacity measurements. The maxima of entropy change, − Δ S m max ∼ 5.04 (5.57) J/kg K, along with an adiabatic temperature change of Δ T a d max ∼ 5.05 (7.25) K was observed for x = 0.15 (0.5) at an applied magnetic field H = 5 T. With the scaling analysis of − Δ S m , the rescaled curves collapse onto a single universal curve anticipated by the mean-field theory, revealing a second-order type of magnetic transition. Furthermore, − Δ S m max follows a power law of H n with n = 0.597 (3) , 0.591(3), and 0.586(3) for Mn 5 − x Fe x Ge 3 (x = 0.15 , 0.3, and 0.5) alloys, respectively. The refrigerant capacity (RC) is increased from 400 J/kg (for x = 0.15) to 420 J/kg (for x = 0.5) with Fe doping in Mn 5 Ge 3. Moreover, the coefficient of refrigerant performance (CRP) enhances with Fe doping from 0.06 (for x = 0.15) to 0.1 (for x = 0.5). Thus, high RC and reasonable CRP values for earth-abundant Mn-based Mn–Fe–Ge alloys promise the potential to replace the high-cost rare-earth (Gd) and heavy metal-based metallic magnetocaloric systems for use in environment-friendly magnetic refrigeration technology. [ABSTRACT FROM AUTHOR]

This paper deals with the proposal of a model that can predict the heat of hydration of concrete containing fly ash and the adiabatic temperature rise test results that are the basis of the model. For the adiabatic temperature rise tests, a total of 12 concrete mixtures were prepared with varying percentages of fly ash replacement and varying ratios of water–cementitious materials (w/cm). The test results indicate that the replacement of fly ash significantly reduces the adiabatic temperature rise and delays the early hydration of fly ash-blended cements. Additionally, w/cm was found to influence not only the maximum adiabatic temperature rise but also the slope of the temperature rise. Therefore, a regression analysis was conducted to propose three parameters (hydration time, hydration slope, ultimate degree of hydration) for the heat of hydration model of concrete containing fly ash. The developed heat of hydration model was validated using test data. Models that did not consider w/cm, similar to those proposed by other researchers, failed to accurately predict the test results. However, the final model developed, which incorporates w/cm, accurately predicted the test results, as confirmed through this study. [ABSTRACT FROM AUTHOR]

This study investigates the suppression effects of heptafluoropropane (CF 3 CHFCF 3)–CO 2 mixtures on the premixed hydrogen-air explosion. The experiments are conducted in a stainless-steel duct system with the concentrations of CF 3 CHFCF 3 and CO 2 ranging from 1% to 4% and 10%–15% respectively. The hydrogen-air equivalent ratio, Φ is varied from 0.8, 1.0, and 1.2. The "finger" shape flame front of the baseline cases changes to the "reversed slope" shape and is significantly dimmed at the center and end sections of the duct as each suppressant concentration increases. When 4% CF 3 CHFCF 3 -15% CO 2 is used, the P max of the fuel-lean (Φ = 0.8) and stoichiometric (Φ = 1.0) cases are reduced by 46.8% and 57.5% compared to baseline cases. The maximum pressure arrival time, t max increases by 16.2 and 25.8 times. The fuel-rich mixture (Φ = 1.2) cannot be ignited under this mixture concentration. Furthermore, the chemical kinetic simulation shows that the addition of the CF 3 CHFCF 3 –CO 2 mixture noticeably reduces the adiabatic flame temperature and CF 3 CHFCF 3 promotes the consumption of O and OH radicals through dehydrogenation reactions (R1466, R1475). At Φ = 1.2 , CF 3 CHFCF 3 inhibits reactions by consumption of H radicals (R1476). CO 2 mainly acts as a physical inhibitor with kinetic coupling with CF 3 CHFCF 3 , which effectively reduces the explosion enhancement of low-concentration CF 3 CHFCF 3. The results provide theoretical support for explosion mitigation strategies in hydrogen applications. • The addition of CO2 enhances the CF3CHFCF3 suppression effects with reduced use of both suppressants. • The "reverse slope" flame is observed at the 4 % CF3CHFCF3 and the flame speed decreases with CO2. • The mixtures effectively reduce the flame temperature and the peak molar fraction of key radicals. • The undesired reaction enhancement caused by CF3CHFCF3 is mitigated by coupling effects of CO2. [ABSTRACT FROM AUTHOR]

Moderate or intense low-oxygen dilution (MILD) combustion has the potential to enhance flame stability and control NOx emissions when using ammonia (NH 3) as fuel. However, the effects of a wide range of ammonia ratios on the combustion characteristics and NOx emissions of jet in a hot co-flow (JHC) ammonia-doped MILD combustion have not been thoroughly investigated. In this study, the combustion and NOx production characteristics of CH 4 /NH 3 hot co-flow combustion jets with a wide range of NH 3 contents (i.e. , ammonia ratios) are investigated systematically. The results indicate that all the simulated cases fall within the MILD combustion regime. The autoignition temperature increases, while the maximum temperature rise decreases monotonically with the increase of ammonia ratio. This suggests that the MILD combustion regime is more easily achieved with the addition of ammonia. The maximum temperature rise shows only slight changes when the ammonia ratio is less than 60%. This phenomenon occurs because the adiabatic flame temperature decreases with the blending of ammonia; however, the heat loss due to radiation is also reduced. Under most conditions, the emission index of NO (EINO) initially increases with the ammonia ratio when it is below 50%, but gradually decreases when it exceeds 50%. Additionally, the EINO decreases with an increase in hot co-flow temperature for a given ammonia ratio, indicating that the overall NO emission levels are suppressed by raising the hot co-flow temperature, despite the peaks of the NO rise. Changes in key chemical reaction pathways are also analyzed. It is found that hydroxyl (OH) radicals play a significant role during the dehydrogenation of NH 3 into NH 2 radicals. In ammonia-rich combustion, a higher ammonia ratio suppresses the conversion of NH i to HNO, while promoting the conversions of NH i to N 2 H 2 , NN, and N 2 O. This shift is advantageous for the conversion of NH 3 into N 2. [Display omitted] • Jets in hot co-flow combustion are simulated with a wide range of ammonia ratios. • Combustion regime and temperature variation are analyzed. • Emission index of NO (EINO) under different conditions are calculated. • Reaction pathways of NH 3 into NO with low and high ammonia ratios are compared. • Effects on NH i radical conversion to N-containing species are also discussed. [ABSTRACT FROM AUTHOR]

Electrocaloric (EC) refrigeration offers superior energy-conversion efficiency, miniaturization, and environmental benefits compared to compression refrigeration. However, its practical application is limited by the challenge of aligning the adiabatic temperature change (Δ T) with the operational temperature range. In this study, we have tailored the EC characteristics of BaTiO 3 (BT)-based Ba(Ti 0.9 Sn 0.1)O 3 (BTS) ferroelectric ceramics using Bi(Mg 0.5 Ti 0.5)O 3 (BMT). We provide a comprehensive analysis of the microstructure, electrical properties, and EC behavior of the (1– x)BTS- x BMT system. Our results indicate that the incorporation of BMT establishes a broad platform in the dielectric spectrum while maintaining high polarization. This improvement potentially increases the electrocaloric effect (ECE) and expands the operating temperature range. Direct heat flux measurements reveal that the x = 0.02 composition achieves a maximum Δ T (Δ T max) of 0.41 K with a temperature span (T span) of 68 °C under an intermediate electric field of 50 kV/cm. Moreover, the x = 0.01 sample exhibits a room-temperature Δ T of 0.33 K and relatively good temperature stability within 30–130 °C. These findings indicate that chemical modification methods have the potential to optimize the cooling capacity of refrigerants. [ABSTRACT FROM AUTHOR]

Continuous miniaturization of electronic components puts higher demands on the heat dissipation of the micro-systems, which requires environmental friendliness, good heat exchange capability, and high-performance micro-refrigeration materials. Here, we developed a Ni–Mn–Fe–In microwire fabricated by the Taylor–Ulitovsky method, showing ⟨001⟩A orientation close to the axial direction of microwire. Due to the large volume change ΔV/V (−1.24%), the large entropy change ΔStr of 43.6 J kg−1 K−1 was achieved in the microwire. Owing to the low driving force of the microwire with a single crystalline of ⟨001⟩A orientation close to the axial direction of microwire, large adiabatic temperature change of −5.7 K was achieved at room temperature after removing a low stress of 120 MPa. Thus, high specific adiabatic temperature change of 47.5 K/GPa was obtained in the microwire, which is the highest value among all the reported low-dimension elastocaloric materials, including thin films/foils, microwires/wires, and ribbons. The outstanding comprehensive properties give this microwire a great application potential in miniaturization and compactness of refrigeration devices. [ABSTRACT FROM AUTHOR]

This paper reports an extensive investigation on the structural, dielectric, ferroelectric and pyroelectric properties of 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 (x = 0.0, 0.5, 0.6, 0.7) ceramics synthesized via conventional solid-state reaction (SSR) technique. X-ray diffraction data confirms the presence of pure perovskite phase. The variation of lattice parameters with strontium concentration in 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 ceramics were evaluated using the Rietveld refinement of the XRD data. The variation of dielectric permittivity with temperature (ε' ∼ T) shows the diffused phase transition and all the parameters related to the relaxor ferroelectrics (relaxation coefficient, activation energy and freezing temperature) were evaluated. The energy storage properties of the as-prepared ceramics were evaluated using the room temperature PE loop. Amongst the as-prepared ceramics, the composition with x = 0.5 possesses the highest energy storage density of 0.46 J/cm3 with an efficiency of 90 %. The temperature dependent P-E loops were used to study the electrocaloric effect (ECE). The ECE calculations were performed using in-direct method based on Maxwell's thermodynamic relations. A maximum adiabatic temperature change of 0.32 K is achieved at 268 K under a small applied electric field of 25 kV/cm for the ceramic with Sr content x = 0.5. Additionally, electrocaloric responsivity ξ max = 0.13 K mm/kV was also found for the studied ceramics. The above results show that the ceramic 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 with the composition x = 0.5 is a viable lead-free option for application in solid state refrigeration. [ABSTRACT FROM AUTHOR]

Azodicarbonamide (ADC) based airbag gas generants with various potential oxidizers, including (1) C2H4O2N4/KNO3 (2) C2H4O2N4/NaNO3 (3) C2H4O2N4/Sr(NO3)2 (4) C2H4O2N4/Ba(NO3)2 (5) C2H4O2N4/KIO4 and (6) C2H4O2N4/NaIO4 were thoroughly tested to identify the best mixture for a real-time ballistic application. The evaluation of the gas generant mixtures is carried out based on the performance properties such as quantity of oxidizer decomposed (in g) to give 1 g of O2, residual mass % of the mixture, density of the oxidizer, oxygen balance percentage for the oxidizer, adiabatic flame temperature, onset temperature, activation energy, pre-exponential factor, critical ignition temperature, change in enthalpy, change in entropy, impact sensitivity and friction sensitivity of the gas generant mixtures. Using the TOPSIS methodology, a systematic approach was developed for the first time to determine the best suitable airbag gas generant for real-time ballistic application by taking into account all of these properties. TOPSIS findings revealed that the preferred order of the airbag gas generant mixture is C2H4O2N4/KIO4 > C2H4O2N4/NaIO4 > C2H4O2N4/KNO3 > C2H4O2N4/NaNO3 > C2H4O2N4/Sr(NO3)2 > C2H4O2N4/Ba(NO3)2. A similar methodology can also be used to discover the best fuel/oxidizer mixture for any other composition. [ABSTRACT FROM AUTHOR]

Large hydrocarbon fuels are used for ground and air transportation and will be for the foreseeable future. A key parameter when burning these fuels is the turbulent consumption speed, which is the velocity at which fuel and air are consumed through a turbulent flame front. Such information can be useful as a model input parameter and for validation of modeled results. In this study, turbulent consumption speeds were measured for three jet-like fuels using a premixed turbulent Bunsen burner. The burner was used to independently control turbulence intensity, unburned temperature, and equivalence ratio. Each fuel had similar heat releases (within 2%), laminar flame speeds (within 5–15%), and adiabatic flame temperatures. Despite this similarity, for constant ReD and turbulence intensity, A2 fuel (i.e. jet-A) has the highest turbulent flame speeds and remains stable (i.e. without tip quenching) at lower ϕ than the other fuels. In contrast the C1 fuel, which consists of heavily-branched alkanes, contains no aromatics and has a relatively high average molecular weight, has the slowest turbulent flame speeds and is the most prone to tip quenching. The C1 fuel has the highest stretch sensitivity, in general, as indicated by calculated Markstein numbers. This work shows that turbulent flame speeds and tip stability of multi-component large hydrocarbon fuels can be sensitive to the chemical class of its components. [ABSTRACT FROM AUTHOR]

High energy composite films made from high explosives has important applications in pyrotechnics. In this study, electrostatic spraying was used to prepare energy-containing films based on 1,2,3,4-butanetetrol tetranitrate (ETN). The results show that all energy containing films are made of nanofibres. They have excellent hydrophobicity and combustion properties. In particular, monolayer films in which ETN is the main energy containing substance. Once ignited, the trace monolayer film generates a maximum pressure of 0.85 MPa and an adiabatic flame temperature of 2,855 °C. For single and double layer films, the heat of combustion can reach 9899 J/g and 11975 J/g respectively. The level of combustion heat can also be controlled by adjustment of the ETN content. The results of the thermo-properties performance evaluation show that by optimizing the nanostructure, the ETN-based energy-containing fiber membranes can meet the requirements of advanced pyrotechnic products. In particular, there is great potential in the metastable intermixed composites (MICs) field. [ABSTRACT FROM AUTHOR]

We report the effects of B-site cationic size disorder ( σ 2 ) and configurational entropy (CE) on the crystal structure and electrocaloric (EC) effect of BaTi1−x−ySnxZryO3 (BTSZ) (0.01 ≤ x ≤ 0.06) ceramics. The samples were designed to show decreased σ 2 and increased CE but the same B-site cation average radius and tolerance factor with increasing x. The tetragonal lattice distortion c/a and piezoelectricity showed a minimum and maximum, respectively, near x = 0.04. The ferroelectric Curie temperature decreased overall from ∼358 to ∼332 K with x increasing from 0.01 to 0.06. The EC effects measured by the direct method showed a maximum with an adiabatic temperature change of ∼0.80 K at 60 kV/cm near x = 0.04. The large EC effect in x = 0.04 is attributed to the small tetragonal distortion and low energy barrier for E-induced phase transformation due to the combined disorder effects of cationic size and configuration. Our results suggest a close correlation between the lattice distortion and EC effects and an effective route to improve the EC effects. [ABSTRACT FROM AUTHOR]

Environment-friendly Ba0.95Ca0.05Ti0.91Sn0.09-xZrxO3 ceramics, with x = 0.00 and 0.01 (BCTSZx) were prepared through a standard solid-state sintering process. The diffusion coefficient estimated from the Santos-Eiras fit of ε r -T plot implies that the ferroelectric-paraelectric transition is a diffuse type. Well-saturated and fatigue resistant P-E hysteresis loops were obtained at room temperature (RT). The energy-storage density (Wrec) and the associated efficiency (η) were obtained from P-E loops data. When applying a relatively losw electric field of 30 kV/cm, a large value of adiabatic temperature change (∆T = 0.73 K), high values of electrocaloric responsivity (ξ = 0.247*10−6 K·m·V−1) and coefficient of performance (COP = 12.26) were obtained in BCTSZ ceramic. In addition, the pyroelectric figures of merit (FOMs) were calculated. The density of pyroelectric energy harvesting increased from 206 to 237 kJ/m3 when the Olsen cycle was operated at temperatures between 25 and 100 °C and an electric field between 0 and 30 kV/cm. The results indicate that the increase in the grain size significantly enhances the dielectric, electrocaloric and pyroelectric properties. This research not only presents a novel technique for generating high-performance ceramic for refrigeration devices, but also expands the field of applications for BaTiO3-based lead-free ferroelectrics for energy storage applications. [ABSTRACT FROM AUTHOR]

In order to obtain large room-temperature electrocaloric effect (ECE) and wide operation temperature range simultaneously in lead-free ceramics, we proposed designing a relaxor ferroelectric with a Tm (the temperature at which the maximum dielectric permittivity is achieved) near-room temperature and glass addition. Based on this strategy, we designed and fabricated lead-free 0.76NaNbO3–0.24BaTiO3 (NN-24BT) ceramics with 1wt.% BaO–B2O3–SiO2 glass addition, which showed distinct relaxor ferroelectric characteristics with strongly diffused phase transition and a Tm near-room temperature. Based on a direct measurement method, a large ΔT (adiabatic temperature change) of 1.3 K was obtained at room temperature under a high field of 11.0 kV mm−1. Additionally, large ECE can be maintained (>0.6 K@6.1 kV mm−1) over a broad temperature range from 23 °C to 69 °C. Moreover, the ECE displayed excellent cyclic stability with a variation in ΔT below ±7% within 100 test cycles. The comprehensive ECE performance is significantly better than other lead-free ceramics. Our work provides a general and effective approach to designing lead-free, high-performance ECE ceramics, and the approach possesses the potential to be utilized to improve the ECE performance of other lead-free ferroelectric ceramic systems. [ABSTRACT FROM AUTHOR]

To achieve the rapid heat dissipation of components in the industrial field, the heat dissipation coating is prepared on the surface, which is conducive to improving the service life of the parts and greatly reducing the industrial costs. In this paper, metallized diamond/Cu composite coatings were fabricated on 1060Al substrate by supersonic laser deposition. The composite coatings were prepared at a nitrogen pressure of 3.0 MPa, a scanning speed of 10 mm/s, and a 1060 nm semiconductor coupled fiber laser with different laser power. The research results show that the laser power affects the interface bonding by affecting the temperature of adiabatic shear instability during particle impact. The metallized diamond forms a good bonding at the interface through the plastic deformation of the Cu matrix. Appropriate parameters ensure that the jet does not affect the subsequent particle deposition and build a good heat transfer bridge to elevate the heat transfer efficiency. The coating prepared at a laser power of 1000 W has the highest thermal diffusion coefficient of 89.3 mm2/s and thermal conductivity of 313.72 W/(m·K), which is 8.92% higher compared to the coating prepared without laser. Experiments with thermal imaging have also demonstrated that the coating at optimal parameter transferred heat faster. Our research provides a technical guidance for rapid preparation of high-quality heat dissipation coatings in industry. [ABSTRACT FROM AUTHOR]

Rare earth‐based perovskites have become an attractive research interest in the field of cryogenic magnetic refrigerants due to their unique advantages in practical applications. The remarkable magnetocaloric effect (MCE) renders EuTiO3 a potential magnetic refrigerant in the liquid helium temperature range. More impressively, the tunability between antiferromagnetism (AFM) and ferromagnetism (FM) provides the feasibility of tailoring the magnetism and enhancing the magnetocaloric performance. In this study, the magnetism of EuTi0.75Al0.125Zr0.125O3 is investigated in depth through first‐principles calculations and experimental methods. Both theoretical calculations and experimental results reveal that it exhibits significant ferromagnetism due to the AFM‐FM magnetic transition promoted by the co‐substitution of Al and Zr. Lattice expansion and altered electronic interactions are responsible for the FM behavior, which leads to a significant enhancement of the MCE. With the field change of 0−1 T, the peak values of magnetic entropy change (−ΔSM), refrigerating capacity (RC), and adiabatic temperature change (ΔTad) reach 18.9 J kg−1 K−1, 77.7 J kg−1, and 7.4 K, respectively. More surprisingly, the values of maximum magnetic entropy change (−ΔSMmax$ - {{\Delta}}S_{\mathrm{M}}^{{\mathrm{max}}}$) and maximum adiabatic temperature change ΔTadmax${{\Delta}}T_{{\mathrm{ad}}}^{{\mathrm{max}}}$ for EuTi0.75Al0.125Zr0.125O3 reach 11.4 J kg−1 K−1 and 3.7 K under the field change of 0−0.5 T, respectively. The remarkable magnetocaloric performance proves it to be a brilliant magnetic refrigerant operating near liquid helium temperature. [ABSTRACT FROM AUTHOR]

A novel amorphous Fe88Pr6Ce4B2 ribbon with better magnetocaloric properties near 285 K is reported in the present work. The Fe88Pr6Ce4B2 ribbon exhibits a typical second-order ferromagnetic–paramagnetic transition near its Curie temperature (Tc, ~284 K), with a maximum magnetic entropy change (−ΔSmpeak) of ~4.15 J/(kg × K) under 5 T and a maximum adiabatic temperature rise (ΔTad) of ~2.57 K under 5 T, both of which are almost the largest amongst the iron-based metallic glasses with Tc = 285 ± 10 K. The high −ΔSmpeak enables several amorphous hybrids with table-like −ΔSm–T curves to be synthesized by appropriately proportioning the Fe88Pr6Ce4B2 ribbon and other amorphous ribbons with different Tc. The larger average −ΔSm and effective refrigeration capacity, as well as the appropriate temperature range, make the two amorphous hybrids potential candidates for use as refrigerants in household magnetic air conditioners. [ABSTRACT FROM AUTHOR]

Isothermal electrocaloric (EC) heat is a key—but rarely reported—parameter for cooling applications. Here, we employ calorimetry with large-area Peltiers (10 × 10 mm2) to study a multilayer capacitor (MLC) of well-ordered PbSc0.5Ta0.5O3 (PST) with a first-order ferroelectric phase transition. Our direct measurements of isothermal EC heat are consistent with complementary EC measurements of similar MLCs that display large EC effects, i.e., indirect EC measurements and direct measurements of adiabatic EC temperature change [Nair et al., Nature 575, 468 (2019)]. Using a field of 7.9 V μm−1, the EC heat associated with the electrically active PST peaks at 11 MJ m−3 near 300 K. At higher temperatures, as one approaches the critical point, the transition is seen to become less first order. Separately, we find that the inactive PST compromises quasi-direct EC measurements. In the future, isothermal EC heat should be directly measured as a matter of routine. [ABSTRACT FROM AUTHOR]

Ammonia is a promising hydrogen carrier and carbon-free fuel. In this work, new laminar burning velocity data of ammonia under intensified preheating (773K–848K) and N 2 diluted condition is provided. Temperature coefficient that reflects the exponentially positive effect of preheating is reevaluated and compared with literature data at lower preheating temperatures, which is in the range of 2.08–2.30 with an improved accuracy. In contrast, dilution is of a linearly negative effect. The laminar burning velocity decreases by more than 20% as the O 2 content drops from 21% to 19%. Besides, 11 recently published kinetic models are evaluated based on the experimental data. The Otomo18 model makes the best prediction with a small relative difference (≤±5%). Accordingly, the effects of radiation heat loss and dilution are analyzed in detail. The former is found insignificant, and the latter is mainly attributed to the adiabatic flame temperature drop. [Display omitted] • New S l data of NH 3 flame over 773K is provided. • Temperature coefficient is still close to 2.0. • Thermal effect dominates the negative dilution effect. • Radiation heat loss is no more significant under preheated condition. • Otomo mechanism performs better in S l prediction. [ABSTRACT FROM AUTHOR]

In this study, the effect of curing temperature on mechanical strength and thermal properties of hydraulic limestone powder (LS) concrete is investigated. The hydration products and microstructure of hydraulic LS concrete are characterized through X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results indicate that the mechanical strength decreases with an increase in the LS dosage. The largest mechanical strength at 3 and 7 d is recorded at the curing temperature of 50 °C, that at 28 and 90 d is obtained at 20 °C, whereas the lowest mechanical strength from 3 to 90 d is obtained at 5 °C. The thermal conductivity and thermal diffusivity of LS concrete are positively correlated with the compressive strength. The adiabatic temperature rise decreases with an increase in the LS dosage, and the largest temperature rise is obtained at the initial temperature of 5 °C, followed by those obtained at 20 and 50 °C. The longest fibrous C-S-H and thickest plate Ca(OH)2 with the largest size at 90 d is obtained at a curing temperature of 50 °C, followed by those obtained at 20 and 5 °C. The MIP results indicate that the largest total amount of gel pores and medium capillary pores at 90 d are obtained at a curing temperature of 20 °C, followed by 50 and 5 °C. [ABSTRACT FROM AUTHOR]

The cyclic stability of the elastocaloric effect and the operating parameters (adiabatic cooling value ΔTad, coefficient of performance, operating temperature range) in Ni50.8Ti49.2 and Ni51.5Ti48.5 single crystals oriented along the ⟨001⟩-direction and containing dispersed Ti3Ni4 particles of different sizes were investigated, and the mechanisms of cyclic degradation of the elastocaloric effect were determined. Aged Ni50.8Ti49.2 single crystals containing nanosized Ti3Ni4 particles were shown to possess the optimal combination of operational properties for solid-state cooling. These crystals are characterized by high adiabatic temperature change ΔTad of 16.8–21.4 K over a wide temperature range above 160 K, the highest elastocaloric effect cyclic stability, and high coefficient of performance values up to 27.8. Ni50.8Ti49.2 single crystals with semi-coherent particles (400 nm in size) demonstrate maximum values of ΔTad = 25.3 K; but, they are not feasible for practical applications because of cyclic degradation caused by the formation of residual martensite and dislocations near large particles as well as low coefficient of performance up to 12.7. The use of Ni-rich Ni51.5Ti48.5 crystals can improve the operating characteristics of crystals with semi-coherent Ti3Ni4 particles and achieve high cyclic stability of the elastocaloric effect by strengthening the crystals through an increase in the volume fraction of particles and a decrease in the distance between them. [ABSTRACT FROM AUTHOR]

The lithium-ion battery (LIB) is a significantly and broadly used power storage system known for its high energy density and extended lifespan. However, it is vital to continue examining and addressing potential safety concerns that require further exploration and discussion. This study employed a pseudo-adiabatic calorimeter, vent sizing package 2, to assess the thermal runaway behaviour exhibited by 18650 LIBs under diverse charging conditions. Through calorimetric experimental trials, the charge levels of the batteries at 0%, 30%, 50%, 80%, and 100% were assessed. This allowed us to identify and evaluate the thermal characteristics that pose potential hazards or risks, such as apparent exothermic onset temperature (T0), self-heating rate (dT/dt), pressure rise rate (dP/dt), maximum temperature (Tmax), maximum pressure (Pmax), and pressure–temperature-time profiles. When a fully charged LIB experienced thermal runaway, it reached a Tmax of 902.9 ℃ and a Pmax of 1985.2 psig. These experimental findings can be utilised to estimate uncontrolled thermal behaviours and thermokinetic parameters across different charge states of the 18650 LIB. These results demonstrate practical applications as well as implications in designing batteries with proactive safety measures and can provide essential parameters for ensuring the process safety of commercial batteries, thereby preventing thermal damage. Based on the adiabatic temperature rise (∆Tad) and Pmax, the venting gas molar amount was also calculated through the ideal gas equation, and the generation of flammable gases was considered a significant factor in the uncontrolled combustion of LIBs. [ABSTRACT FROM AUTHOR]

Superelastic shape memory alloys with an integration of large elastocaloric response and good cyclability are crucially demanded for the advancement of solid-state elastocaloric cooling technology. In this study, we demonstrate a giant elastocaloric effect with improved cyclic stability in a <001>A textured polycrystalline (Ni50Mn31Ti19)99B1 alloy developed through directional solidification. It is shown that large adiabatic temperature variation (|ΔTad|) values more than 15 K are obtained across the temperature range from 283 K to 373 K. In particular, a giant ΔTad up to −27.2 K is achieved by unloading from a relatively low compressive stress of 412 MPa at 303 K. Moreover, persistent |ΔTad| values exceeding 8.5 K are sustained for over 12,000 cycles, exhibiting a very low attenuation behavior with a rate of 7.5 × 10−5 K per cycle. The enhanced elastocaloric properties observed in the present alloy are ascribed to the microstructure texturing as well as the introduction of a secondary phase due to boron alloying. [ABSTRACT FROM AUTHOR]

The electrocaloric effect (ECE) refers to the isothermal entropy or adiabatic temperature change of polar crystals when an electric field is applied or removed. This effect is a promising approach for the development of compact solid state coolers. Among the promising materials are environmentally friendly lead-free relaxors of the (Na 0.5 Bi 0.5)TiO 3 –BaTiO 3 (NBT-BT) family showing a large ECE in a wide temperature range. Intriguingly, some groups have reported negative ECE in these materials and attributed this to the antiferroelectric features of NBT. Both relaxor and antiferroelectric properties of NBT can be enhanced by doping, e.g., by adding bismuth magnesium titanate (BMT). In this study, the effect of the incorporation of BMT on the structural, electrical, and electrocaloric properties of lead-free ceramics (1- x)[0.95(Na 0.5 Bi 0.5)TiO 3 -0.05BaTiO 3 ]-(x)Bi(Mg 0.5 Ti 0.5)O 3 , where x = 0, 0.1, and 0.2, was investigated. The temperature dependences of the dielectric permittivity exhibit behavior characteristic of relaxors. With increasing BMT content, the maximum polarization value decreases from 23 to 8.5 μC/cm2, and the depolarization temperature shifts from 322 to 254 K, which points out an enhancement in relaxor properties. We have shown that double hysteresis loops observed in the studied materials are not caused by the antiferroelectric nature of the compositions, but by the pinning effect by point defects. Furthermore, the negative ECE estimated from the indirect measurements using Maxwell's relation was not confirmed by the direct measurements using a quasi-adiabatic calorimeter. The interplay between defect dipoles and the role of BMT in stabilization of ergodic relaxor behavior at lower temperatures and electrocaloric effects are discussed. The study also shows that the NBT-5BT-10BMT composition is promising for energy storage applications. [ABSTRACT FROM AUTHOR]

Porous Ni-Mn-Ga shape memory alloys (SMAs) were prepared by powder metallurgy using NaCl as a pore-forming agent with an average pore size of 20–30 μm. The microstructure, phase transformation, superelasticity, and elastocaloric properties of the porous alloys were investigated. The prepared porous alloy had a uniform pore distribution and interconnected microchannels were formed. Cu doping can effectively improve the toughness of a porous alloy, thus improving the superelasticity. It was found that porous Ni-Mn-Ga-Cu SMAs have a flat stress plateau, which exhibits a maximum elongation of 5% with partially recoverable strain and a critical stress for martensite transformation as low as about 160 MPa. In addition, an adiabatic temperature change of 0.6 K was obtained for the prepared porous alloy at a strain of 1.2% at about 150 MPa. This work confirms that the introduction of porous structures into polycrystalline Ni-Mn-Ga SMAs is an effective way to reduce costs and improve performance, and provides opportunities for engineering applications. [ABSTRACT FROM AUTHOR]

Magnetic refrigeration, which utilizes the magnetocaloric effect, can provide a viable alternative to the ubiquitous vapor compression or Joule-Thompson expansion methods of refrigeration. For applications such as hydrogen gas liquefaction, the development of magnetocaloric materials that perform well in moderate magnetic fields without using rare-earth elements is highly desirable. Here we present a thorough investigation of the structural and magnetocaloric properties of a novel layered organic-inorganic hybrid coordination polymer Co4(OH)6(SO4)2[enH2] (enH2 = ethylenediammonium). Heat capacity, magnetometry and direct adiabatic temperature change measurements using pulsed magnetic fields reveal a field-dependent ferromagnetic second-order phase transition at 10 K < T C < 15 K. Near the hydrogen liquefaction temperature and in a magnetic field change of 1 T, a large maximum value of the magnetic entropy change, Δ S M P k = − 6.31 J kg−1 K−1, and an adiabatic temperature change, Δ T ad = 1.98 K, are observed. These values are exceptional for rare-earth-free materials and competitive with many rare-earth-containing alloys that have been proposed for magnetic cooling around the hydrogen liquefaction range. The magnetocaloric effect could allow for more efficient refrigeration compared to traditional vapour compression, however, it requires materials with large magnetocaloric coefficients, and these typically require rare-earths. Herein, Levinsky et al. demonstrate a large magnetocaloric effect in a rare-earth free layered coordination polymer. [ABSTRACT FROM AUTHOR]

[Objective] Most gas combustion devices used in university laboratories are custom-built. Given the widespread use of mixed gases, both the devices and experiments pose significant risks. Inadequate consideration of safety during the design, manufacture, and operation of these devices increases the likelihood of explosion accidents, which can result in severe injuries and property damage. Therefore, engineering control measures should be implemented to reduce the risk of such accidents. [Methods] This paper proposes using the Le Chatelier formula to estimate the explosion limits of combustible mixed gases. It emphasizes creating a flammability diagram for combustible gas--inert gas--oxygen mixtures and presents the combustion and explosion characteristics of mixed gases with varying volume fractions under standard temperature and pressure conditions. This approach offers a quantitative method for mitigating explosion risks by incorporating inert gases into combustion experiments. Additionally, the paper classifies combustion devices into two categories: normal pressure burners and deflagration/detonation devices. [Results] A comparison of the two types of devices reveals that deflagration/detonation devices pose a higher safety risk. When preparing and handling combustible mixed gases in these devices, special attention should be given to the impact parts of the device during gas flow, as these components are more prone to abnormal temperature increases. This paper estimates the temperature after adiabatic compression of commonly used combustible gases, such as methane and oxygen, and suggests that adiabatic compression in the negative pressure state of impact parts may lead to accidental combustion and explosion. Moreover, the explosion hazards associated with gas combustion devices are discussed from several perspectives, including the explosion temperatures and pressures of commonly used combustible gases in the laboratory and the effects of explosion overpressure on human health. [Conclusions] From the standpoint of inherent safety, the following recommendations are proposed: 1 Relatively safe combustible gases should be chosen for experimental schemes whenever possible. Inert gases should be selected based on their inerting capacity. Normal-pressure burners should be chosen, or the volume of the combustion chamber and gas mixing tank in deflagration/ detonation devices should be minimized as much as feasible. 2 Experimental devices should be equipped with appropriate valves, impact parts should be minimized, and a status monitoring and control system should be used to promptly address abnormal situations. Additionally, filters, flame arresters, pressure relief valves, and other necessary safety features should be installed. 3 The laboratory environment must meet the requirements for combustion experiments. Devices with explosion potential should be isolated. The room should be equipped with combustible gas detection and alarm systems, adequate ventilation, explosion-proof electrical equipment, and complete emergency supplies. 4 The configuration and proper use of personal protective equipment should be standardized. By implementing a comprehensive set of explosion prevention and control measures, accidents can be prevented, their progression can be managed, their consequences can be mitigated, and the overall safety of combustion experiments can be improved. [ABSTRACT FROM AUTHOR]

We have studied the impact of demagnetizing fields on the magnetocaloric effect of commercial-grade gadolinium plates. Adiabatic temperature changes (Δ T) were measured for magnetic fields applied along the parallel and perpendicular directions of the plates. The differences in the obtained Δ T values were accounted for by differences in the internal field due to demagnetizing effects. A combination of calorimetric measurements under a magnetic field and thermometric measurements has enabled us to obtain Brayton cycles for the two different magnetic field orientations. It has been found that the refrigerant capacity for a Brayton cycle working at 1.6 T around room temperature reduces from R C = 9.4 to R C = 5.5 J kg − 1 when the demagnetizing factor changes from N D = 0.035 to N D = 0.928 for the parallel and perpendicular configurations, respectively. It has been shown that it is possible to obtain significant demagnetizing field-induced magnetocaloric effects by rotating the sample in a region of a constant applied magnetic field. The refrigerant capacity of a Brayton cycle around room temperature for a 1.6 T constant applied magnetic field is R C = 0.6 J kg − 1 . The feasibility of these demagnetizing field-induced effects has been confirmed by direct thermometric measurements, which reveal adiabatic temperature changes of 1 K when the sample is rotated between the perpendicular and parallel configurations. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of TbCrO3 and TmCrO3 are reported and compared with those of the previously reported rare-earth chromites RCrO3 (R = Gd, Dy, Ho, and Er) and other perovskite-type oxides. The samples of TbCrO3 and TmCrO3 in this work were synthesized using a citrate gel combustion technique, and their magnetic properties were investigated and compared with those reported previously on RCrO3 (R = Gd, Dy, Ho, and Er). The Cr3+–Cr3+ ordering temperatures were found to strongly depend on the ionic radii of the rare-earth. By fitting the dc magnetization data with modified Curie–Weiss law including the Dzyaloshinsky–Moriya antisymmetric exchange interaction (D) and the symmetric exchange constant Je, spin canting angles (α) were obtained. In general, α was found to increase with the decreasing ionic radii of R3+ in RCrO3. The magnetocaloric properties investigated included the magnetic entropy change (−ΔS) for a given change in magnetic field (ΔH), the corresponding adiabatic temperature change (ΔTad), and their relative variations (ΔTad/ΔH) and (−ΔS/ΔH). It is observed that for RCrO3, (−ΔS) measured in the vicinity of the ordering temperature of R3+–R3+, varies almost as G2/3 where G is the de Gennes factor. Among RCrO3, GdCrO3 shows the largest value of (−ΔS/ΔH), because of its largest G factor and its magnitudes of (ΔTad/ΔH) and (−ΔS/ΔH) compare well with the reported values for the perovskites GdFeO3 and EuTiO3. These comparisons presented here provide useful information on the potential use of these materials in magneto-refrigeration technology. [ABSTRACT FROM AUTHOR]

Reactive single-step hot-pressing at 1473 K and 35 MPa for 4 h produces dense, bulk, near single-phase, low-cost, and low-criticality Fe2Al1.15B2 and Fe2Al1.1B2Ge0.05Ga0.05 MAB samples, showing second-order magnetic phase transition with favorable magnetocaloric properties around room temperature. The magnetic as well as the magnetocaloric properties can be tailored upon Ge and Ga doping, leading to an increase in the Curie temperature T C and the spontaneous magnetization m S. The maximum isothermal entropy change Δ s T , m a x of hot-pressed Fe2Al1.15B2 in magnetic field changes of 2 and 5 T amounts to 2.5 and 5 J(kgK)−1 at 287.5 K and increases by Ge and Ga addition to 3.1 and 6.2 J(kgK)−1 at 306.5 K, respectively. The directly measured maximum adiabatic temperature change Δ T a d , m a x is improved by composition modification from 0.9 to 1.1 K in magnetic field changes of 1.93 T. Overall, we demonstrate that hot-pressing provides a much faster, more scalable, and processing costs reducing alternative compared to conventional synthesis routes to produce heat exchangers for magnetic cooling devices. Therefore, our criticality assessment shows that hot-pressed Fe-based MAB phases provide a promising compromise of material and processing costs, criticality, and magnetocaloric performance, demonstrating the potential for low-cost and low-criticality magnetocaloric applications around room temperature. [ABSTRACT FROM AUTHOR]

This paper presents a novel green combined heat and power generation system for industrial applications. It composes of a hydrogen-fueled combined cycle power plant and a battery energy storage. Firstly, the hydrogen-air rich mixture enters the combustion chamber of the gas turbine cycle for generating electricity, while recovering the heating energy from the exhausted flue gases for driving a steam turbine cycle. The heating energy extracted from the condenser heat exchanger is also used to supply the heating demand of the end-user. Moreover, a comprehensive thermodynamic model and analysis of H 2 combustion process is provided to estimate the adiabatic flame temperature based on enthalpies of reactants and products. The optimum operating point of the cogeneration system is found by solving a mixed-integer nonlinear problem using MATLAB and GAMS over a 24-h study horizon aiming to minimize its daily operation cost considering all technical constraints of system components and load-generation balance criterion. It is found that the energy efficiency of the hydrogen-fueled combined cycle changes from 46 to 58 % while generating 11.331–12.982 MW electricity and 4.436–4.984 MW heat. Two cases are studied without and with participation of battery in energy procurement strategy. It is demonstrated that the objective function of the optimization problem improves from 18 $ cost in case 1 to 29 $ revenue in case 2. • Thermodynamic model and analysis of a H 2 -fueled CHP plant is presented. • Adiabatic flame temperature is obtained based on enthalpies of reactants and products. • A high-temperature heat exchanger is used to produce steam from waste heat of gas turbine flue gases. • Optimal charge and discharge of battery is scheduled for higher cost savings. [ABSTRACT FROM AUTHOR]

The research has examined the effects of CO 2 dilution on ignition characteristics in H 2 /air mixtures. An ignition kernel was initiated by a laser-induced plasma in H 2 /air/CO 2 mixtures with a bulk velocity of 6.5 m/s. An infrared camera was used to measure radiation intensity emitted from H 2 O and ignition probabilities. A high-speed schlieren image system was utilized to measure ignition kernel areas and ignition time. High-speed chemiluminescence was performed to examine OH* intensities. Numerical simulations were conducted using GRI 3.0 mechanisms to calculate reaction rates and laminar flame speeds. The ignition probability is highest for the undiluted mixtures and decreases with increasing the CO 2 dilution fraction at constant adiabatic temperatures. A prolonged ignition time is observed at elevated CO 2 dilution concentrations. Increasing the CO 2 mole fraction decreases the ignition kernel growth, the integrated OH* intensity, and the integrated radiation intensity for each adiabatic temperature. CO 2 reacts with H radicals and decreases the production of OH*, OH, and H 2 O. The CO 2 dilution in the H 2 /air flames significantly contributes to the reduced reaction rate and flame speed, resulting in the low ignition probability. The high ignition probability is found at the large integrated OH* intensity in all cases. The ignition probability is high at the large integrated radiation intensity under the constant adiabatic flame temperatures. The OH* intensity is a critical parameter to estimate the ignition probability in the diluted lean hydrogen flames. • The effects of CO 2 dilution on the ignition process have been studied in lean premixed H 2 /Air flames. • The ignition probability decreases with increasing the CO 2 dilution fraction. • An increase in the CO 2 dilution fraction in the mixtures reduces OH* intensity and radiation intensity emitted from H 2 O. • The presence of CO 2 in the mixtures decreases reaction rates and flame speed. [ABSTRACT FROM AUTHOR]

Thermoelastic stress analysis (TSA) can be used to determine the stress field of structures or materials under cyclic loadings through temperature under adiabatic conditions. So high-frequency cyclic loadings are considered as a fundamental condition. However, loading frequencies in many practical applications do not meet the adiabatic conditions. In order to improve the accuracy of TSA under low-frequency fatigue loadings, the non-adiabatic response in TSA was derived by combining the classical thermoelastic equation and heat conduction equation. This response was used to create a modified model that accounted for heat transfer and temperature distribution under low-frequency loading conditions. Otherwise, fatigue test and finite element method were used to evaluate the correctness of the modified model using epoxy resin material. The results showed that the temperature change obtained from the modified model were in good agreement with the experiment results. The modified model can effectively evaluate the structural stress under low-frequency fatigue loadings. [ABSTRACT FROM AUTHOR]

Electrocaloric refrigeration shows the merits of environmental safeguarding, large efficiency, easy combination, and miniaturization as a novel solid-state refrigeration technique. In this paper, Sn4+ is doped into the B site of BLNT ceramics. By adjusting the doping content, the T-C phase transition peak was successfully shifted to room temperature and promoted the formation of relaxor ferroelectrics, resulting in a wider operating temperature range (T span) and improved adiabatic temperature change (ΔT). A comprehensive study was conducted on the crystal structure, surface morphology, dielectric properties, ferroelectricity, and electrical properties of BLNTS ceramics with varying levels of Sn4+ doping. Wherein, when the doping amount is 5Sn, a maximum adiabatic temperature change value (ΔT max) of 1.14 K was obtained, and the temperature span (T span) reached 45 °C (T span is defined as ΔT ≥ 80 % ΔT max). This work proposes a high-performance environmentally friendly electrocaloric effect (ECE) material suitable for solid-state cooling applications. [ABSTRACT FROM AUTHOR]

We present the results of direct measurements of the adiabatic temperature change (ΔTad) for the Fe50Rh50 alloy in a cyclic magnetic field (CMF) of 1.2 T. It is shown that increasing the frequency of the CMF from 1 to 30 Hz is accompanied by a shift of the position of temperature dependence ΔTad(T) maximum, Tmax, toward low temperatures. With an increase in the CMF frequency from 1 to 5 Hz, the ΔTmax value decreases by ∼12%. A further increase in frequency leads to stabilization of the effect. In the vicinity of the antiferromagnetic-ferromagnetic phase transition point TC = 370 K, ΔTad exhibits unconventional frequency behavior: while at T well above TC, the value of ΔTad monotonously decreases as frequency increases, at T = 370.4 K; an interval of frequency-independent ΔTad up to 10 Hz is observed, and at 368 K < T < TC, the maximum of ΔTad(f) dependence is found in the interval 1 < f < 10 Hz. Such behavior in the future can be applied in magnetic cooling technology due to large values of ΔTad and the frequency stability of the effect in alternating fields. The specific cooling power reaches giant values of ∼22 W/g at 20 Hz, which is comparable to the values under the same conditions for Gd −21.6 W/g. The unconventional behavior of ΔTad in the CMF is discussed in the context of the role of secondary phase localization, which leads to an enhanced internal local magnetic field and dynamic effects of ΔTad. [ABSTRACT FROM AUTHOR]

In order to reveal the deflagration mechanism of DME/H2-blended gasses, the micro-mechanism was studied based on the constructed UC San Diego 2016 pyrolysis oxidation mechanism model. The results show that adiabatic flame temperature and laminar flame speed increase with the increase in the equivalence ratio (Φ); they first increase and then decrease with the increase in the hydrogen (H2)-blended ratio (λ), and with the increase in λ, the Φ corresponding to the peak laminar flame speed of the blended gas increases. The addition of H2 increases the consumption of O2, and H2 reacts with CO to form H2O and CO2, promoting complete combustion. When Φ = 1.0–1.2, the equilibrium mole fraction of H and OH-activated radicals reach the maximum, and with the addition of H2, the concentration of activating radicals gradually increases, while the number of promoted elementary reactions increases by two, and the number of inhibited elementary reactions does not increase. Meanwhile, the addition of H2 increases the reaction rate of most reactions on the main chemical reaction path CH3OCH3→CH3OCH2→CH2O→HCO→CO→CO2 of DME and increases the risk of the deflagration of DME/H2-blended gas. [ABSTRACT FROM AUTHOR]

In order to improve the magnetocaloric properties of MnNiSi-based alloys, a new type of high-entropy magnetocaloric alloy was constructed. In this work, Mn0.6Ni1−xSi0.62Fe0.4CoxGe0.38 (x = 0.4, 0.45, and 0.5) are found to exhibit magnetostructural first-order phase transitions from high-temperature Ni2In-type phases to low-temperature TiNiSi-type phases so that the alloys can achieve giant magnetocaloric effects. We investigate why chexagonal/ahexagonal (chexa/ahexa) gradually increases upon Co substitution, while phase transition temperature (Ttr) and isothermal magnetic entropy change (ΔSM) tend to gradually decrease. In particular, the x = 0.4 alloy with remarkable magnetocaloric properties is obtained by tuning Co/Ni, which shows a giant entropy change of 48.5 J∙kg−1K−1 at 309 K for 5 T and an adiabatic temperature change (ΔTad) of 8.6 K at 306.5 K. Moreover, the x = 0.55 HEA shows great hardness and compressive strength with values of 552 HV2 and 267 MPa, respectively, indicating that the mechanical properties undergo an effective enhancement. The large ΔSM and ΔTad may enable the MnNiSi-based HEAs to become a potential commercialized magnetocaloric material. [ABSTRACT FROM AUTHOR]

Materials with electrocaloric effect (ECE) and/or thermal switching ratio λ are desirable for developing various heat management devices, but developing high-performance candidates, especially those that simultaneously possess large near room-temperature ECE and λ is actually absent. The Zr-rich PbZr1−xTixO3 (PZT) displays a composition-induced antiferroelectric-ferroelectric (AFE-FE) phase boundary, where an unusual negative ECE is expected. Meanwhile, the electric field-sensitive dipole orientation during the AFE-FE phase transition can be employed to modulate λ. In this work, the Zr-rich PZT with coexisting AFE and FE phases was developed and the AFE-FE phase transition temperature is tuned toward room temperature by changing the Ti content to achieve large negative ECE and λ. A large adiabatic temperature change ΔT of −3.3 K accompanied by a giant λ of 1.84 near 60 °C is captured in optimal PbZr0.95Ti0.05O3 ceramics, demonstrating a prominent application prospect in solid-state refrigeration. [ABSTRACT FROM AUTHOR]

This study presents a new single-step synthesis of Fe 2 AlB 2 at 1150°C for 4 hours using hot isostatic pressing (HIPing). X-ray diffraction confirmed the material as single-phase, while metallographic etching revealed predominant equiaxial Fe 2 AlB 2 grains (∼25 μm) and minor unreacted boron particles and Al-rich zones at grain boundaries. Magnetocaloric investigations demonstrated an impressive isothermal entropy change of 2.9 J/kg.K at 2 T and 6.8 J/kg.K at 5 T, with corresponding adiabatic temperature changes of 1.1 K and 2.8 K at 2 and 5 T, respectively. The HIPed Fe 2 AlB 2 performance matches that of studies without post-treatments or doping. Fe 2 AlB 2 , composed of light and earth-abundant elements, can be synthesized in a single step using HIPing, making it an attractive option for magnetic refrigeration with improved energy efficiency and simplified manufacturing. • Successful synthesis of Fe2AlB2 through a single-step reactive hot isostatic pressing (HIPing) process. • Utilization of a 0.005 M NaOH + 0.01 M NaOCl solution for metallographic etching to reveal grain boundaries. • Equiaxial Fe2AlB2 grains (∼ 25 μm) in with Al enrichment at grain boundaries and a modest presence of unreacted B particles. • Magnetocaloric Effect (MCE) measurements show a -ΔSM of 2.9 and 6.8 J/kg·K at 2 and 5 T, respectively. • Determination of the relative cooling power (RCP) values of 39 J/kg and 142 J/kg at 2 and 5 T, respectively. [ABSTRACT FROM AUTHOR]

The paper presents research results of the synthesis, phase composition, and structure of products obtained by highly exothermic reactions between Ti and C10H8O4 mixture components, depending on the plastic waste concentration and Ti powder dispersiveness, density of initial samples, and synthesis medium. The dependence of the phase composition and structure of the synthesis products on the concentration of the polymer (plastic) component in the initial Ti -PET (C10H8O4) system was found. When the plastic waste content is 20 wt% to 25 wt %, synthesis products contain TiC0.5O0.5-TiC0.6-0.75 particle agglomerates. Further growth in the polyethylene terephthalate content from 30 wt% to 45 wt% leads to the formation of synthesis products consisting of titanium carbide (TiC0.6-1.0). The gaseous byproduct composition of the exothermic reaction is investigated for the Ti--C10H8O4 mixture composition. It is found that the gaseous by-product mostly contains hydrogen and carbon monoxide as well as impurities of different hydrocarbons (methane, acetylene, ethane, ethene) and carbon dioxide. The maximum adiabatic temperature of the gas combustion temperature is 2080 °C, which demonstrates the possibility of using gas as a fuel for energy generation devices. Based on the data obtained, it is possible to create a basis for a new plastic waste technology to fabricate carbide-containing materials. [ABSTRACT FROM AUTHOR]

Phase change materials can be converted between solid, liquid, and gaseous states, absorbing or releasing a large amount of heat. PCM is incorporated into concrete to adjust the temperature difference between inside and outside of concrete, which can reduce cracking. In this paper, the finite element analysis method is used to establish the model of an ordinary concrete structure, doped with phase change materials, on the basis of mechanical properties and a temperature regulation test performed by calculating the adiabatic temperature rise of concrete with different contents of composite phase change material, comparing the experimental and simulation results of the ordinary concrete structures with phase change materials, and analyzing the change in temperature field of the concrete structure with the content of self-prepared composite phase change materials. It is found that the addition of self-prepared composite phase change materials reduces the temperature peak of the concrete structure in the stage of hydration heat and delays the time taken to reach the temperature peak. Then, the temperature field of the phase change mass concrete structure is established, and the influence law of composite phase change material admixture on the temperature field of mass concrete is summarized through the time–temperature curves of different admixture amounts and positions so as to predict the possibility of cracks in mass concrete. [ABSTRACT FROM AUTHOR]

Interrupted and incremental tensile tests have been carried out on 316 austenitic stainless steel at different strain rates, revealing the correlation between the strain, strain rate, and temperature rise of martensitic transformation. The FERITSCOPE FMP ferrite tester and Telops FAST M2K infrared imager measured the martensite content and surface temperature rise at different strain rates, respectively. The effect of adiabatic temperature rise and strain rate on martensitic transformation was isolated by incremental tests. Compared with the incremental tensile test at a low strain rate (0.001 s−1), it has been found that the increase in strain rate has a negative effect on martensitic transformation, and the effect of strain rate on martensitic transformation seems to be more significant than that of adiabatic temperature rise. The formation and evolution mechanism of strain-induced martensitic transformation of 316 austenitic stainless steel were studied by electron backscattered diffraction. During the process of tensile plastic deformation, the nucleation and growth of new martensite mainly occurred near the twin boundary. [ABSTRACT FROM AUTHOR]

Transient conjugate heat transfer measurements under varying temperature and velocity inlet boundary conditions at incompressible flow conditions were performed for flat plate and ribbed channel geometries. Therefrom, local adiabatic wall temperatures and heat transfer coefficients were determined. The data were analyzed using typical heat transfer correlations, e.g., Nu = C Re m Pr n , determining the local distributions of C and m. It is shown that they are closely linked. A relationship ln C = A − m B is observed, with A and B as modeling parameters. They could be related to parameters in log-law or power-law representations for turbulent boundary layer flows. The parameter m is shown to have a close link to local pressure gradients and, therewith, near wall streamlines as well as friction factor distributions. A normalization of the C parameter allows one to derive a Reynolds analogy factor and, therefrom, local wall shear stresses. [ABSTRACT FROM AUTHOR]

The determination of the characteristics and main combustion properties of fuels is necessary for post-implementation in different applications. Among the most important combustion properties of a fuel are the combustion products, flame temperature and laminar burning velocity. Therefore, this paper describes the step-by-step development and coding of a MATLAB application that can determine 12 combustion products, flame temperature and laminar burning velocity in order to understand the logic of calculus procedure, so any user would be able to make improvements of new functionalities (add more fuels, add more combustion products, etc.). The numerical procedure and methods (Gaussian elimination, Taylor Series and Newton–Raphson) parallel with their implementation as code lines for the development of the application are carried out using flow charts. In addition, simulations in Ansys Chemkin were performed and included in the application as part of the results comparison. It was found that: (1) The MATLAB Application codification and development were successfully explained in detail, (2) the functions and execution sequence are described by using flow charts and code extract, (3) the application is available to everyone for modifications, (4) the application can only be used for hydrocarbons fuels, (5) the application execution time registered was less than 8 s. [ABSTRACT FROM AUTHOR]

Hydrogen-enriched methane (HEM) combustion is an effective method for reducing the consumption of carbonaceous fuels. However, high adiabatic flame temperature of H 2 can cause large NO emissions. To reduce the NO and CO 2 emissions from HEM combustion, the Box-Behnken design (BBD) method combining response surface experimental design, analysis of variance, and multi-nonlinear regression models was adopted. The effects of the H 2 doping ratio (X H2), preheated air temperature (T air), excess air coefficient of burners arranged at the bottom (E x,b), and their interactions on the NO, N 2 O, and CO 2 emissions of a gas-fired boiler were investigated. According to the BBD method, the NO, N 2 O, and CO 2 emissions prediction models with R2 exceeding 0.98 were proposed, respectively. The results showed that the increase of T air had a positive effect on reducing NO emissions, as the NO exhausted from HEM combustion is mainly thermal NO. Compared with T air and E x,b , X H2 was the most significant factor affecting N 2 O and CO 2 emissions, indicating that an increase in X H2 can significantly reduce greenhouse gas emissions. Additionally, the formation and consumption of N 2 O emissions presented a competitive mechanism at X H2 increased from 0 to 0.8, and CO 2 emissions reduced with the increase of X H2 , T air , and E x,b. Furthermore, a comprehensive emission prediction model with NO, N 2 O, and CO 2 emissions was proposed. With the target of minimizing total NO, N 2 O and CO 2 emissions, three groups of combinations for X H2 , T air , and E x,b were obtained from the equal weight, entropy weight method, and criteria importance through the inter-criteria correlation method as 1:1:1, 24:9:17, and 21:11:18. The results showed that for minimize emissions, there is not much difference in the results calculated based on the optimal boundary conditions under different weights. For various reduction targets for nitrogen, carbon, and greenhouse gases, three groups of optimal combinations of X H2 , T air , and E x,b were obtained and their accuracies were verified based on numerical calculations with relative errors below 6%. The proposed comprehensive pollutant emission prediction models are conducive to calculating the pollutant emissions of HEM combustion and guiding the investigation of prediction models considering other operating conditions. • Box-Behnken design method was first adopted to study NO, N 2 O, and CO 2 emissions. • NO, N 2 O and CO 2 emission prediction models for quick calculation were proposed. • A comprehensive emission prediction model for H 2 /CH 4 combustion was proposed. • The optimal boundary combination for less pollutant emissions was obtained. [ABSTRACT FROM AUTHOR]

Continuous dynamic recrystallization (CDRX) is widely acknowledged to occur during hot forming and plays a significant role in microstructure development in alloys with moderate to high stacking fault energy. In this work, the flow stress and CDRX behaviors of the TC18 alloy subjected to hot deformation across a wide range of processing conditions are studied. It is observed that deformation leads to the formation of new low-angle grain boundaries (LAGBs). Subgrains rotate by absorbing dislocations, resulting in an increase in LAGB misorientation and the transition of some LAGBs into high-angle grain boundaries (HAGBs). The HAGBs migrate within the material, assimilating the (sub)grain boundaries. Subsequently, an internal state variable (ISV)-based CDRX model is developed, incorporating parameters such as the dislocation density, adiabatic temperature rise, subgrain rotation, LAGB area, HAGB area, and LAGB misorientation angle distribution. The values of the correlation coefficient (R), relative average absolute error (RAAE), and root-mean-square error (RMSE) between the anticipated true stress and measured stress are 0.989, 6.69%, and 4.78 MPa, respectively. The predicted outcomes demonstrate good agreement with experimental findings. The evolving trends of the subgrain boundary area under various conditions are quantitatively analyzed by assessing the changes in dynamic recovery (DRV)-eliminated dislocations and misorientation angles. Moreover, the ISV-based model accurately predicts the decreases in grain and crystallite sizes with higher strain rates and lower temperatures. The projected outcomes also indicate a transition from a stable and coarse-grained microstructure to a continuously recrystallized substructure. [ABSTRACT FROM AUTHOR]