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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]

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]

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]

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]

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]

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]

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]

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]

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]

Under the action of cement hydration heat, the construction environment, thermal insulation measures, and pipe cooling systems, a mass concrete pile cap is subject to a complex internal temperature field, which makes it difficult to control its internal surface temperature difference (TISTD), the internal adiabatic temperature rise (TIATR), and the surface temperature (TST). In this study, a mass concrete pile cap of a very large bridge (the length, width, and height were 26.40 m, 20.90 m, and 5.00 m, respectively, and the central-pier pile cap was constructed with C40 concrete) was taken as the research object. The control factors affecting the temperature field of the pile cap were determined by comparing the field temperature measurements with the values calculated with finite element software simulation analysis. By using Midas Civil (2022 v1.2) and Midas FEA (NX 2022) finite element software, these factors (the concrete mold temperature, the concrete surface convection coefficient, the ambient temperature, the pipe cooling system parameters, etc.) were numerically analyzed, and their influence laws and degrees were determined. [ABSTRACT FROM AUTHOR]

Room-temperature elastocaloric cooling is considered as a zero-global-warming-potential alternative to conventional vapor-compression refrigeration technology. However, the limited entropy and large-deformation features of elastocaloric polymers hinder the creation of the breakthrough in their caloric responses and device development. Herein, we report that the addition of a small amount of inorganic nanofillers into the polymer induces the aggregate of the effective elastic chains via shearing the interlaminar molecular chains, which provides an additional contribution to the entropy in elastocaloric polymers. Consequently, the adiabatic temperature change of −18.0 K and the isothermal entropy change of 187.4 J kg−1 K−1 achieved in the polymer nanocomposites outperform those of current elastocaloric polymers. Moreover, a large-deformation cooling system with a work recovery efficiency of 56.3% is demonstrated. This work opens a new avenue for the development of high-performance elastocaloric polymers and prototypes for solid-state cooling applications. In this work, inorganic nanofillers are added to SEBS polymers to induce shearo-caloric effects, enhancing the elastocaloric response. Authors design and demonstrate a double-unit cooling device with a work recovery efficiency of 56.3% and a system coefficient of performance of 8.3. [ABSTRACT FROM AUTHOR]

Elastocaloric cooling technology has the prospect of becoming a commercialized green alternative to current vapor-compression technology, and the systematic characterization of the elastocaloric effect and microstructure has become increasingly significant for the optimization of elastocaloric coolers and heat pumps. In this work, a comprehensive elastocaloric effect characterization for a dog-bone shaped NiTi sheet with a thickness of 0.5 mm was performed for the application in a compact continuous rotating bending elastocaloric cooler. The elastocaloric effect was found to be nearly identical under Brayton-like and sinusoidal force-controlled cyclic tensile loadings. The maximum adiabatic temperature change values of 31 and 23 K were recorded in Brayton-like cyclic loadings under maximum applied stress of 600 and 400 MPa, respectively, with an applied strain rate of 0.1 s−1. During fatigue tests, large applied stress (>600 MPa) and high applied strain rates (>0.1 s−1) tended to result in premature failure of the NiTi sheet samples. In the continuous rotating bending elastocaloric cooler, the sheets generated a temperature span of 6 K between the copper heat sink and heat source. The results of this work provide a set of thermophysical property data for the elastocaloric solid refrigerant and insights for the optimization of structural and operational parameters in elastocaloric coolers and heat pumps. [ABSTRACT FROM AUTHOR]

Developing readily available and cost-effective electrocatalysts as an alternative to the noble metals is a critical issue for renewable hydrogen energy generation. Mesoporous high-entropy oxides (HEOs) are among the most noteworthy candidates in the kinetically challenged process of oxygen evolution reaction (OER); The current study notifies the successful fabrication, and characterization of a series of meso-structured HEOs (5 elements) and MEOs (4 elements) nanopowders with remarkable electrocatalytic performance. Obtained results reveal that the synthesized HEOs and MEOs nanocompounds are meso-structured (with pore size of ⁓43–67 Å) with particle size of ⁓20–30 nm. Combusted HEOs and MEOs powders have high crystallinity degree (derived from XRD analysis) and homogenous elemental distributions. The electrocatalytic activity of the prepared HEOs and MEOs nanopowders were studied using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) analyses. It was specified that HEO nanoparticles (HEO 0.95 sample) exhibit superior electrocatalytic performance compared to MEOs particles with respect to their overpotential of 310 mV at 10 mA cm−2 and Tafel slope of 53 mV.dec−1. The drop of the charge transfer resistance (R CT) and increase of the conductivity in HEO 0.95 sample contributes to the improved electrocatalytic OER activity of the HEOs nanopowders. Taking ECSA into account, the improved electrocatalytic activity of meso-structured HEO 0.95 sample relates to the large number of active sites in this sample. The XRD, TEM, and FE-SEM results of HEO 0.95 sample after OER analysis indicated no alteration in phase composition and morphology revealing the reusability of the synthesized nanoparticles. This study also provides an insight into the behavior of Co, Ni, Cu elements as typical electrocatalysts as well as Zn and Mg elements as obscure electrocatalysts for efficient OER electrocatalysis. Furthermore, the impact of adiabatic temperature, crystallinity degree and physicochemical features of meso-structured particles on electrocatalytic performance are explored. [ABSTRACT FROM AUTHOR]

Solid‐state methods for cooling and heating promise a sustainable alternative to current compression cycles of greenhouse gases and inefficient fuel‐burning heaters. Barocaloric effects (BCE) driven by hydrostatic pressure (p) are especially encouraging in terms of large adiabatic temperature changes (|ΔT| ≈ 10 K) and isothermal entropy changes (|ΔS| ≈ 100 J K−1 kg−1). However, BCE typically require large pressure shifts due to irreversibility issues, and sizeable |ΔT| and |ΔS| seldom are realized in a same material. Here, the existence of colossal and reversible BCE in LiCB11H12 is demonstrated near its order‐disorder phase transition at ≈380 K. Specifically, for Δp ≈ 0.23 (0.10) GPa, |ΔSrev| = 280 (200) J K−1 kg−1 and |ΔTrev| = 32 (10) K are measured, which individually rival with state‐of‐the‐art BCE figures. Furthermore, pressure shifts of the order of 0.1 GPa yield huge reversible barocaloric strengths of ≈2 J K−1 kg−1 MPa−1. Molecular dynamics simulations are performed to quantify the role of lattice vibrations, molecular reorientations, and ion diffusion on the disclosed BCE. Interestingly, lattice vibrations are found to contribute the most to |ΔS| while the diffusion of lithium ions, despite adding up only slightly to the entropy change, is crucial in enabling the molecular order–disorder phase transition. [ABSTRACT FROM AUTHOR]

In the current work, the thermodynamic properties of equiatomic and non-equiatomic Ni-Ti were estimated using Factsage Software for the "self-propagating high temperature synthesis (sHs) method. To calculate behind the pure substance model, the sublattice model was used. For the various ratios of the nickel in the B2 ordered phase and second intermetallics, the values of adiabatic temperature, Cp, Gibbs free energy, enthalpy of formation, products, and liquid-solid ratio were computed (Ni3Ti, Ti2Ni). These proporties play a crucial role in understanding the nature of propagating behavior since they affect the final product's micro/macrostructure, mechanical characteristics, and stable or metastable phases. The results were compared with the literature. It was also discussed why the existing studies could not reach the theoretical adiabatic temperature and the effect of the ignition W wire on the sample was investigated with the experimental study. [ABSTRACT FROM AUTHOR]

A large adiabatic temperature change along with a wide operating temperature region is usually required for the electrocaloric materials to fulfill their refrigeration function. In general, doping foreign ions into BaTiO3 is the frequently utilized strategy in order to obtain excellent electrocaloric materials for the practical application. In the current paper, BaTiO3 lead‐free ferroelectric ceramics were doped by Ca2+ and Sn4+ simultaneously in order to generate a coexistence state at room temperature, where ferroelectric domains and nanodomains exit. As a result, a large polarization and a wide operating temperature range were finally induced. It is found that Ba0.9Ca0.1Ti0.85Sn0.15O3 has a maximum adiabatic temperature change of 0.85 K and an excellent working temperature region (65 K, ∆T > 90% Tmax) was achieved under an electric field of 50 kV/cm. The above phenomenon indicates that the modified BaTiO3 ceramics can be a good potential electrocaloric material in the state of cross‐existence of ferroelectric domains and nanodomains. [ABSTRACT FROM AUTHOR]

In the present study, first, the environmental challenges and cracking characteristics during the construction of plateau concrete on the Sichuan–Tibet route were revealed. Then, using a multi-field coupled shrinkage model with hydration temperature humidity constraints, the early and long-term cracking risks in the core of plateau pier bodies were investigated. Later, the effects of tensile strength, pouring interval age and adiabatic temperature rise on the cracking risk were analyzed. Finally, various control measures for high-altitude concrete cracking were proposed. The results indicated that the complex environment of the plateau led to different forms of cracks in the pier body, especially vertical cracks in the straight sections. The long-term risk of core cracking in the plateau pier body is significantly greater than the risk of early cracking. This risk was strongly influenced by factors such as the concrete tensile strength, pouring interval age and adiabatic temperature rise, which should be given more attention. Deformation compensation can significantly enhance the peak and residual deformation capacities of plateau concrete, with peak values greater than 900 με and residual deformation greater than 200 με at day 60, as well as its resistance to cracking. Strategies such as adopting radiant cooling techniques, improving construction techniques and implementing effective management measures can all play a vital role in improving the cracking resistance of highland concrete. [ABSTRACT FROM AUTHOR]

We report the effect of configurational entropy (CE) on the electrocaloric (EC) effect of Ba x Sr y Ca z (Bi 0.5 Li 0.5) 1- x - y - z TiO 3 (BSCBLT) (0.627≤ x ≤ 0.66, 0.0716≤ y ≤ 0.1993, 0.0145≤ z ≤ 0.1758) ceramics. All samples were designed to show different CE but the same A-site cation average radius, tolerance factor and cationic size disorder. The samples with x ≤ 0.64 show ferroelectric (FE) relaxor behavior, while x ≥ 0.65 are normal FEs. x = 0.65 shows the maximum EC effects among all samples. Both maximum adiabatic temperature change (ΔT m) and CE vary almost in the same way with increasing x. The anomalous enhancement of ΔT m in x = 0.65 with relatively lower CE compared with that in x = 0.64 can be ascribed to an additional contribution of Ba concentration induced FE to relaxor FE transition in BSCBLT. Our results reveal important evidences of enhanced EC effects by CE and suggest that designing FEs or relaxor FEs with high CE might be an effective route to achieve high EC effects. [ABSTRACT FROM AUTHOR]

Electrocaloric refrigeration technology has garnered significant attention due to its potential for next-generation solid-state cooling, which is miniaturized and efficient. However, achieving a substantial electrocaloric effect (ECE) and a wide working temperature range at low electric fields remains a challenge. In this study, a synergistic approach combining domain and defect engineering was used in transparent 0.88 Pb(Mg 1/3 Nb 2/3)O 3 -0.12PbTiO 3 - x Sm(0.88PMN-0.12 PT- x Sm) ceramics to improve ECE and temperature stability. Finally, a notable adiabatic temperature change (ΔT) of 2.07 K in the x = 0.01 ceramic, with ΔT exceeding 1.0 K across a broad temperature range from 30 to 180 °C was achieved. Piezoresponse force microscopy (PFM) and X-ray photoelectron spectroscopy revealed the presence of small domains and appropriate oxygen vacancies as contributors to the enhanced ECE and broad operation temperature range. This work introduces a promising candidate material for electrocaloric refrigeration. [ABSTRACT FROM AUTHOR]

The effect of pulsating jet on the unsteady film cooling performance was studied by experimental and numerical simulation. The FLIR thermal infrared thermal camera was used the measure the adiabatic temperature of the surface. The large eddy simulation was conducted for analyzing the adiabatic film cooling effectiveness at four different jet non-dimensionalized pulsated frequency of St = 0, 0.1, 0.2, and 0.3. The analysis of the dynamic model decomposition of both the velocity and temperature fields obtained by numerical calculation was performed to obtain the coupling relationship between the flow and heat transfer. Results show that the cooling effectiveness of steady film cooling (St = 0) decreases with the increase of blowing ratio. At low blowing ratio (M = 0.65), the cooling efficiency of the pulsating jet is significantly lower than the steady-state jet. At the blowing ratio of 1.0 and 1.5, the cooling efficiency of the low frequency pulsating jet (St = 0.1) is a little higher than the steady-state jet, indicating that the low frequency pulsation under the high blowing ratio can improve the coverage of the cooling air. At high pulsating frequency (St = 0.3), the cooling effectiveness is obviously declined. [ABSTRACT FROM AUTHOR]

Comprehensive characterizations of the superelastic and elastocaloric effects of NiTi and NiTi-based shape memory alloys (SMA) in the operation temperature region are highly desirable for using them in elastocaloric coolers with a large temperature lift. In this article, we report the superelastic and elastocaloric effects of a commercially available superelastic polycrystalline NiTi SMA tube with an outer diameter of 5 mm and a wall thickness of 1 mm between 293 and 330 K. The NiTi tube sample was subjected to a training of 250 cycles to stabilize its superelastic and elastocaloric effects. We observed that temperature dependencies existed for both superelastic and elastocaloric effects of the NiTi tube, and stress–strain curves differed much between isothermal and adiabatic loading conditions. The largest temperature rise and temperature drop measured at 293 K under an applied strain of 3.66% and a strain rate of 0.1 s−1 during loading and unloading were 21 and 11 K, respectively. The loading conditions (loading function and holding time) also impacted the superelastic effect of the NiTi tube. We identified two major reasons for the irreversibility of the adiabatic temperature change: the hysteresis heat dissipation and the temporary residual strain after unloading, and they affected the cooling performance of the elastocaloric cooler in different ways. We investigated the dependencies of the superelastic and elastocaloric effects on the maximum applied strain and the temperature distribution on the NiTi tube during loading and unloading. The results are beneficial to the modeling of elastocaloric coolers with large temperature lifts. [ABSTRACT FROM AUTHOR]

This study examined the influence of various chemical reaction mechanisms and heat loss conditions on the prediction of longitudinal combustion instability in the Continuous Variable Resonance Combustor (CVRC). To assess the impact of chemical reaction mechanisms on the prediction of longitudinal combustion instability modes, both global and skeletal mechanisms were used, while adiabatic wall conditions were employed to eliminate the effects of heat loss. To evaluate the effect of heat loss conditions on the prediction of combustion instability modes, investigations were conducted under three different conditions: adiabatic wall, isothermal wall, and considering thermal radiation using the simple P1 model and the gray gas model. Radiative heat loss was calculated using a radiative convection boundary condition, while heat loss through wall convection was ignored. The dominant frequency, temperature field, pressure field, and combustion instability development mechanism were analyzed based on the numerical results and compared with experimental data and previous numerical studies. The use of a skeletal mechanism and the consideration of heat loss were found to reduce the difference in combustion instability mode frequency compared to experimental data. The results showed that maintaining an isothermal wall temperature effectively decreased the difference in the dominant frequency compared to experiments, but had limitations in reducing pressure fluctuation amplitudes. Additionally, incorporating thermal radiation did not significantly decrease the difference in the first mode frequency compared to experimental data, although it kept the range of pressure fluctuations within a reasonable level. Therefore, this study underscores the importance of accurate temperature prediction for evaluating thermal-acoustic instability frequencies and highlights the necessity of using a chemical reaction mechanism that accurately predicts the adiabatic flame temperature and heat loss conditions. • We investigated the impact of modeling choices on the prediction of instability. • Global and skeletal reaction mechanisms overestimated instability frequencies. • Radiative heat loss was found negligible for temperatures under 2500 K. [ABSTRACT FROM AUTHOR]

The combination of Al nanoparticles (ANPs) as fuel and H2O2 as oxidizer is a potential green space propellant. In this research, reactive force field molecular dynamics (ReaxFF-MD) simulations were used to study the influence of water addition on the combustion of Al/H2O2. The MD results showed that as the percentage of H2O increased from 0 to 30%, the number of Al-O bonds on the ANPs decreased, the number of Al-H bonds increased, and the adiabatic flame temperature of the system decreased from 4612 K to 4380 K. Since the Al-O bond is more stable, as the simulation proceeds, the number of Al-O bonds will be significantly higher than that of Al-H and Al-OH bonds, and the Al oxides (Al[O]x) will be transformed from low to high coordination. Subsequently, the combustion mechanism of the Al/H2O2/H2O system was elaborated from an atomic perspective. Both H2O2 and H2O were adsorbed and chemically activated on the surface of ANPs, resulting in molecular decomposition into free radicals, which were then captured by ANPs. H2 molecules could be released from the ANPs, while O2 could not be released through this pathway. Finally, it was found that the coverage of the oxide layer reduced the rate of H2O2 consumption and H2 production significantly, simultaneously preventing the deformation of the Al clusters' morphology. [ABSTRACT FROM AUTHOR]

The commercial ZK60 magnesium alloy processed by solution heat treatment was dynamically loaded with a high strain rate by means of the split Hopkinson pressure bar (SHPB), and the dynamic instantaneous precipitation of second phases was investigated in the present work for the first time. TEM observations indicated that the β´1 with average length/diameter of 68.24–19.27 nm and β′2 phases with an average diameter of 16.15 nm precipitated within the dynamic deformation time of 180 μs at 3000 s−1. The adiabatic temperature rise generated by the dynamic deformation increases the atomic diffusion coefficient of solute atoms, which contributes to the generation of precipitated phases. Therefore, the precipitation of the second phases is thermodynamically feasible. It is also feasible to kinetically accelerate the rate of atomic diffusion to eventually lead to the instantaneous precipitation of the mass of the β′1 and β′2 phases, due to the combined effects of adiabatic temperature rise, high deviatoric stresses, high-density dislocation (vacancies) formed by the dynamic loading, and the initial supersaturated vacancies formed by the T4 treatment. Since the high-density dislocation was generated and the numerous reinforcing phases (β′1 and β′2) were precipitated in the matrix during deformation, the Vickers hardness values of alloy increased from 64.4 HV to 93.1 HV. [ABSTRACT FROM AUTHOR]

In this work, the frequency dependence of ferroelectric and electrocaloric properties in barium titanate-based ceramics was studied based on Maxwell relations. It is found that the maximum and remnant polarization will decrease while the coercive field increases a lot with rising frequency from 0.1 to 10 Hz, indicating that polarization rotation and domain switching become difficult at high frequencies. The electrocaloric properties show the different frequency dependence at different phase structures. Isothermal entropy change (Δ S) and adiabatic temperature change (Δ T) are similar around/above Curie temperature ( T C) , showing tiny frequency dependence. However, Δ S and Δ T display the obvious frequency dependence below T C , especially in the orthorhombic–tetragonal phase-transition region with a stable ferroelectric phase, and this frequency dependence becomes more obvious under a low-electric field. It is also found that increasing the frequency can weaken the electric field dependence of electrocaloric strength. This work gives a general profile of frequency dependence for electrocaloric properties in ferroelectric ceramics. [ABSTRACT FROM AUTHOR]

The concentration of residual O2 in oxy-fuel combustion flue gas needs to be reduced before CO2 transportation, utilization, or storage. An original application of the printed circuit heat exchanger (PCHE) for catalytic combustion with natural gas (catalytic deoxygenation) is described for reducing the residual O2 concentration. The PCHE design features multiple adiabatic packed beds with interstage cooling and fuel injection, allowing precise control over the reaction extent and temperature within each reaction stage through the manipulation of fuel and utility flow rates. This work describes the design of a PCHE for methane–oxygen catalytic combustion where the catalyst loading is minimized while reducing the O2 concentration from 3 vol% to 100 ppmv, considering a maximum adiabatic temperature rise of 50 °C per stage. Each PCHE design differs by the number of reaction stages and its individual bed lengths. As part of the design process, a one-dimensional transient reduced-order reactor model (1D ROM) was developed and compared to temperature and species concentration axial profiles from 3D CFD simulations. The final design consists of five reaction stages and four heat exchanger sections, providing a PCHE length of 1.09 m at a processing rate of 12.3 kg/s flue gas per m3 PCHE. [ABSTRACT FROM AUTHOR]

This paper presents original findings on the heterogeneity of the mechanical properties of concrete of an early age, dependent on the evolution of the hydration reaction. The properties investigated are the compressive strength, the Young's modulus, and the flexural tensile strength. To achieve this, we employed a testing apparatus in which the samples underwent curing in a chamber that followed the same temperature profile as an adiabatic calorimeter. This method enabled us to monitor the hydration progress across multiple samples. We used a function derived from the literature, with specific adaptations, to model the evolution of normalized properties in relation to hydration. Heterogeneity was quantified through the use of the dispersion coefficient. The key finding of this study is that the dispersion coefficient for the analyzed mechanical properties diminishes with the advancement of hydration, until reaching a specific threshold. Beyond this point, the impact of microcracking on the various properties becomes increasingly pronounced, varying according to the particular property being examined. Moreover, this paper presents initial functions designed to offer formulas that assist in modeling concrete within probabilistic numerical simulations from the early stages of its development. [ABSTRACT FROM AUTHOR]

We examine the relationships between the observed long‐term trends of the zonal wind in the mesopause regions at King Sejong Station (KSS), Antarctica, and wind trends in the Southern Hemisphere (SH) middle atmosphere using the 15‐year data set from KSS meteor radar, Aura MLS and MERRA‐2. During July, significant positive trends of zonal winds appear above z = 90 km and near the stratopause over the KSS, while negative trends exist between the two layers. In the SH winter, the observed mesopause winds correlate positively (negatively) with stratospheric (mesospheric) winds in the polar region, while they exhibit opposite correlations with the low‐latitude winds. The positive mesopause trends of zonal winds near KSS are connected, through the thermal wind relationship, to cooling (warming) trends induced by the upward (downward) trends of residual circulation over the high‐latitude mesosphere and low‐latitude stratosphere (high‐latitude stratosphere), which shows vertical coupling throughout the SH winter middle atmosphere. Plain Language Summary: Based on 15‐year (2007–2021) observations of horizontal winds obtained at mesopause altitudes of 80–100 km by a meteor radar at King Sejong Station (KSS; 62.22°S, 58.78°W), Antarctica, we find long‐term trends of eastward winds above 90 km in July. To investigate the relationship between the observed long‐term trends of the mesopause wind over the Southern Hemisphere (SH) polar region and winds in the SH middle atmosphere, we analyze Aura MLS satellite data and MERRA‐2 reanalysis data. In the SH winter, the mesopause zonal winds over polar regions are positively (negatively) correlated with zonal winds in the polar stratosphere (polar mesosphere), while the opposite correlations are found between the polar mesopause and low latitudes. We demonstrate that the trends of temperature induced by adiabatic warming or cooling associated with meridional circulation in the stratosphere and mesosphere are connected to the observed mesopause wind trends in the polar region (KSS), which accounts for the vertical coupling between the mesopause region and stratosphere across the mesosphere. Key Points: Trends of zonal winds in the Southern Hemisphere mesopause and stratosphere are investigated using meteor radar and satellite observationsSignificant correlations are found between the mesopause wind at high latitudes and the winds in the middle atmosphereThe observed wind trends in austral winter are coupled vertically between the mesopause region and stratosphere across the mesosphere [ABSTRACT FROM AUTHOR]

Seeking novel high-performance elastocaloric materials with low critical stress plays a crucial role in advancing the development of elastocaloric refrigeration technology. Here, as a first attempt, the elastocaloric effect of TiZrNbAl shape memory alloy at both room temperature and finite temperatures ranging from 245 K to 405 K, is studied systematically. Composition optimization shows that Ti-19Zr-14Nb-1Al (at.%), possessing excellent room-temperature superelasticity with a critical stress of around 100 MPa and a small stress hysteresis of around 70 MPa and outstanding fracture resistance with a compressive strain of 20% and stress of 1.7 GPa, demonstrates a substantial advantage as an elastocaloric refrigerant. At room temperature, a large adiabatic temperature change ( Δ T ad ) of −6.7 K is detected, which is comparable to the highest value reported in the Ti-based alloys. A high elastocaloric cyclic stability, with almost no degradation of Δ T ad after 4000 cycles, is observed. Furthermore, the sizeable elastocaloric effect can be steadily expanded from 255 K to 395 K with a temperature window of as large as 140 K. A maximum Δ T ad of −7.9 K appears at 355 K. The present work demonstrates a promising potential of TiZrNbAl as a low critical stress and low hysteresis elastocaloric refrigerant. [ABSTRACT FROM AUTHOR]

This paper presents the results of thermodynamic calculation of adiabatic temperature and the equilibrium composition of products of HfO2 reduction with calcium depending on carbon and calcium content at different pressures. The formation of solid HfN–HfC solutions is identified with the formation of hafnium carbonitride. It is shown that adiabatic temperatures lie in a range of 2000–2900 K, and its elevation is limited by the melting of CaO at 2900 K. The introduction of carbon often reduces the adiabatic temperature, and a pressure rise leads to its increase. A connection is revealed between the composition of products and the type of temperature curves. The main reason why adiabatic temperature rises along with pressure is a displacement of equilibrium toward the formation of condensed phases and an increase in the fraction of HfN in the products. [ABSTRACT FROM AUTHOR]

The combustion of fuels has been studied by many researchers as it is used in a wide range of engineering applications. The chemical equilibrium approach served as the foundation for the investigation of combustion reactions. This article presents a software application designed to facilitate the calculation of combustion processes by calculating the combustion of 16 fuels among the common alkanes (CnH2n+2) and alcohols (CnH2n+1OH). The Ozan Combustion Calculator (OCC) offers a user-friendly and efficient graphical user interface (GUI) that allows users to easily input data and obtain results. The program was developed using MATLAB 2021a and LaTeX software, ensuring its reliability and accuracy. To perform these calculations, the program utilizes calculations of the thermophysical properties of fuels and water obtained from tables. The program consists of five modules, each serving a specific purpose. These modules calculate various parameters, such as the Adiabatic Flame Temperature, Exergy of Combustion with Dry Air, Exergy of Combustion with Moist Air, Energy of Combustion with Dry Air, and Energy of Combustion with Moist Air. Additionally, the program can be used to investigate the impact of relative humidity on the adiabatic flame temperature and exergy destruction. The results obtained from the calculations reveal that the adiabatic flame temperature exhibits a linear decrease as the relative humidity increases. On the other hand, exergy destruction demonstrates a quadratic increase with higher relative humidity values. The program derives mathematical relationships for the adiabatic flame temperature and exergy destruction with respect to relative humidity values, with a high regression coefficient ( r 2 = 0.999 ). The versatility of OCC makes it suitable for various applications. It can be utilized in university settings for both undergraduate- and graduate-level courses, providing students with a practical tool for studying combustion processes. Additionally, it finds applications in industrial settings for the design and optimization of combustors, gas turbines, and burners. The user-friendly interface and accurate calculations make OCC a valuable resource in the field of combustion engineering. [ABSTRACT FROM AUTHOR]

By combining the distinctive advantage of the pulsed laser with a high strain rate, this study conducts dynamic compaction experiments with high-strain rate laser shock and quasi-static compaction with a low strain rate on aluminum-based composite powder (Wp/Al) and analyzes the effects of pressing pressure and Wp content on the relative density, surface microstructure, demolding pressure, radial rebound, and mechanical properties of Al-based composite (Wp/Al) compacts under the two modes of action. The shock wave propagation process, densification process, and adiabatic temperature rise in the pressed billet at high strain rates due to laser shock are analyzed in combination with 2D MPFEM. Results show that the relative density of the billets decreases as the Wp particle content increases and that the relative density of the billets obtained with high-strain rate laser shock dynamic compaction is 97.62%, which is up to 2.9% higher than that of quasi-static compaction with low strain rate, the demolding pressure decreases by up to 1.56 times, and the hardness increases by up to 13.5%. The hard particles Wp are evenly distributed on the surface of the billet, and no significant aggregation of hard particles is observed. The 2D MPFEM reveals that the speed between particles within the powder at the beginning of the pressing reaches the minimum collision speed of welding, which is beneficial to the particles to achieve improved adhesion; laser high-speed impact under the particles due to inertial effects produces severe plastic deformation, which in turn improves the formability of the powder; in the process of laser shock the temperature at the edge of the particles is greater than the temperature inside the particles, and the temperature near the upper impactor is higher. In addition, the results of the simulation study are compared with the experiments and are found to be remarkably consistent. [ABSTRACT FROM AUTHOR]

Herein we demonstrate the influence of aliovalent (Ca2+) substitution in the single-phase orthorhombic La 1-x Ca x FeO 3 (with x = 0.01, 0.03, 0.05, 0.07, 0.09) nanoparticles prepared by simple combustion method. The samples were systematically studied using XRD, SEM-EDS, and UV–Vis-DRS characterization techniques for their structural, microstructural-elemental, and optical (band structure) characteristics. Also, the catalytic attributes were evaluated through photocatalytic studies against indigo carmine in the presence of visible light. It was observed that La 1-x Ca x FeO 3 nanoparticles crystallized in orthorhombic structure at its as-synthesized form. The SEM analysis showed that the spherical nanoparticles with high porosity and agglomerations were further reduced with increasing Ca2+ concentration. The inclusion of Ca2+ also demonstrated the change in the band structure, as the band gap of the material reduced from 2.24 eV to 1.75 eV while the Ca2+ content increased from 1 mol% to 9 mol%. Furthermore, elevating the Ca2+ levels in the La 1-x Ca x FeO 3 resulted in enhanced photocatalytic decomposition of the indigo carmine dye, exhibiting a maximum efficacy of 96.5 % at neutral pH and a stabilization period of 120 min under visible light. The increase in photocatalysis is attributed to the formation of Fe4+ ions and oxygen vacancies induced by the aliovalent cation (Ca2+) replacement at the La3+ site in the LaFeO 3 host matrix. The results suggest that the prepared LaFeO 3 nanoparticles are potential nano-catalysts for photocatalytic activities against indigo carmine under visible light. [ABSTRACT FROM AUTHOR]

A large adiabatic temperature change (Δ T) in lead-free ceramics is highly desired to develop eco-friendly and high efficiency solid-state refrigeration device based on electrocaloric effect (ECE). However, a large Δ T is often obtained near high Curie temperature (T c > 100 °C), which impedes the practical applications for electrocaloric refrigeration technology. Herein, the lead-free (1-x)(K 0.48 Na 0.535) 0.03 Li 0.07 (Nb 0.99 Sb 0.01)O 3 -xBaZrO 3 (x = 0, 0.02, 0.04 and 0.06) ceramics were synthesized through a conventional solid-state sintering method. A polymorphic phase transition (PPT) region is constructed by composition engineering to achieve large ECE near the ambient temperature. A Δ T of 0.48 K under 50 kV/cm is obtained at 60 °C by using the direct measurement in KNLNS-0.02BZ ceramic with coexistence of R-O-T phase. This work suggests that building multi-phase coexistence is a feasible design scheme in order to achieve ECE near the room temperature. [ABSTRACT FROM AUTHOR]

Nitrogen is the most abundant element in the Earth's atmosphere, yet its geochemical behavior and distribution among the various reservoirs (atmosphere, crust, mantle, and core) remain poorly understood. Although estimates of N and C fluxes in the mantle vary, there is a consensus regarding the disparity between input and output, leading to an increase in N and C contents in the mantle. The low solubility of N in mantle minerals raises questions about possible N or C storage in the mantle. Evidence suggests that Fe–N–C phases, such as Fe3C, Fe7C3, ε-Fe3N, metals, and non-stoichiometric carbonitrides, may be accessory phases at mantle pressure and temperature conditions, and thus potential hosts of C and N in the deep mantle. To investigate the phase relations and melting behavior in the (Fe,Ni)–N–C system, 19 experiments were conducted with varying starting compositions at 10 GPa and 1000–1400 °C. The results indicate that carbides, nitrides, carbonitrides, nitrocarbides, Fe(Ni)-metal, Fe-oxides, and diamond are stable at deep upper mantle pressure conditions. However, the compositions of naturally occurring nitrocarbides with high C and N contents, as found in diamond inclusions, could not be reproduced in the experiments. The significant incorporation of Ni in the experimental phases, which is also not observed in natural carbonitrides and nitrocarbides, suggests their formation in Ni-poor regimes. The solidus temperatures of the N- and C-rich systems are well below the adiabatic temperatures of the surrounding mantle. Therefore, it is hypothesized that cold regions in subduction zones, such as within or at the edge of a C- and N-rich subducted plate, are the likely formation environment for solid Fe–C–N phases. [ABSTRACT FROM AUTHOR]

Solid refrigerants exhibiting a caloric effect upon applying external stimuli are receiving attention as one of the next-generation refrigeration technologies. Herein, we report a new inorganic refrigerant, rubidium cyano-bridged manganese–iron–cobalt ternary metal assembly (cyano-RbMnFeCo). Cyano-RbMnFeCo shows a reversible barocaloric effect with large reversible adiabatic temperature changes of 74 K (from 57 °C to −17 °C) at 340 MPa, and 85 K (from 88 °C to 3 °C) at 560 MPa. Such large reversible adiabatic temperature changes have yet to be reported among caloric effects in solid–solid phase transition refrigerants. The reversible refrigerant capacity is 26000 J kg−1 and the temperature window is 142 K. Additionally, cyano-RbMnFeCo shows barocaloric effects even at low pressures, e.g., reversible adiabatic temperature change is 21 K at 90 MPa. Furthermore, direct measurement of the temperature change using a thermocouple shows +44 K by applying pressure. The temperature increase and decrease upon pressure application and release are repeated over 100 cycles without any degradation of the performance. This material series also possesses a high thermal conductivity value of 20.4 W m−1 K−1. The present barocaloric material may realize a high-efficiency solid refrigerant. Cyano-RbMnFeCo shows a large barocaloric effect with reversible adiabatic temperature changes of 74 K (340 MPa) and 85 K (560 MPa). Here, the authors observe temperature change of +44 K (440 MPa), stable after repeating over 100 times. [ABSTRACT FROM AUTHOR]

The effect of dynamic strain rate on the microstructure and properties of Q&P980 high-strength steel is studied. The quenching and partitioning, and tempering (Q&P-T) heat-treatment process was used to select different dynamic strain rates (1, 600, 1200 s–1) for tensile testing. The microstructure was characterized by OM, XRD, SEM, EBSD, and other tests to investigate the relationship between microstructure and mechanical properties. The results show that the strengthening stage and the necking stage of the tested steel appear to be prolonged, at dynamic strain rates. The strength and plasticity of the tested steel were significantly improved. The microstructure and morphology of the tested steels in the deformed and undeformed areas were found to be increasingly near to each other at dynamic strain rates of 600 and 1200 s–1. Under the impact of the TRIP effect and the adiabatic temperature rise effect at high strain rate stretching, the microstructure appears to be refined and elongated. The tested steel performed best overall at a dynamic strain rate of 1200 s–1, with a tensile strength of 1080 MPa and an energy absorption strength of 38.97 GPa%. [ABSTRACT FROM AUTHOR]

Strain-induced crystallization (SIC) prevalently strengthens, toughens, and enables an elastocaloric effect in elastomers. However, the crystallinity induced by mechanical stretching in common elastomers (e.g., natural rubber) is typically below 20%, and the stretchability plateaus due to trapped entanglements. We report a class of elastomers formed by end-linking and then deswelling star polymers with low defects and no trapped entanglements, which achieve strain-induced crystallinity of up to 50%. The deswollen end-linked star elastomer (DELSE) reaches an ultrahigh stretchability of 12.4 to 33.3, scaling beyond the saturated limit of common elastomers. The DELSE also exhibits a high fracture energy of 4.2 to 4.5 kJ m-2 while maintaining low hysteresis. The heightened SIC and stretchability synergistically promote a high elastocaloric effect with an adiabatic temperature change of 9.3°C. [ABSTRACT FROM AUTHOR]