Temperature Activation Energy Research Articles

Semiconductor-to-metal transition in BaFe12−x(Ru, Re)xO19 (x = 0.1) hexaferrite at high temperatures

Semiconductor-to-metal-like behavior was observed in the BaFe11.9(Ru,Re)0.1O19 ceramic hexaferrite at temperatures above 450 K. X-ray diffraction analysis confirmed its hexagonal structure with minor α-Fe2O3 impurities, while Rietveld refinement revealed significant changes in the lattice parameters, particularly an expansion along the c axis. Atomic positions at the 2b, 4f2, and 12k sites were altered due to the partial substitution of Fe3+ by Ru4+ and Re4+ cations, which have smaller ionic radii than Fe3+. These substitutions modified the bond lengths within the crystal structure, as evidenced by increased Fe–O distances, and led to a partial reduction of Fe3+ to Fe2+, increasing electron density. The AC conductivity, σac(T), showed a transition from semiconducting to metallic-like behavior above ∼450 K. The resistivity, ρac(T), exhibited a plateau near 500 K, indicating a change in the conduction mechanism. The transport mechanism below 450 K was dominated by the non-overlapping small polaron tunneling model, characterized by thermally activated hopping with minimal Coulomb interactions, while above 450 K, the correlated barrier hopping model became dominant. The activation energy for high temperatures, Ea=0.31±0.06 eV, was consistent with the sum of the hopping energy WH=0.20±0.01 eV and half the disorder energy, Ed/2, which increased significantly with temperature. The partial substitution of Ru4+ and Re4+ significantly weakened the magnetic interactions, resulting in reduced saturation magnetization and modifications in coercivity.

Determining datum temperature and apparent activation energy: an approach for mineral admixtures incorporated cementitious systems

The maturity method is used to predict the strength of concrete by monitoring its temperature history. Accuracy of maturity method relies on the dependable determination of the datum temperature and the apparent activation energy. The current study introduces a new approach, complementing those in ASTM C1074-11, for determining the datum temperature and apparent activation energy. The experimental study involved using two different mineral additives to portland cement at 6%, 20%, and 35% replacement amounts. The mortars were then cured at temperatures of 5, 20, and 40 °C, and their strengths were determined. Subsequently, the datum temperatures and apparent activation energies for these mixtures were calculated using both the proposed approach and the alternatives from ASTM C1074-11. Strength estimations were conducted in conjunction with commonly used maturity functions. The results indicate that the proposed approach determines the datum temperature and apparent activation energy reliably for mineral admixture-incorporated mortars. Furthermore, the predicted strengths, derived from the datum temperature and apparent activation energy calculated through the proposed approach, show a closer alignment with the experimental results when applying the Nurse-Saul and Hansen-Pedersen equations, as opposed to the Rastrup and Weaver-Sadgrove models.

Synthesis and Luminescence Characterization of Novel Red-Emitting Phosphors Based on Eu3+-Activated K2Sr(MoO4)2 Molybdates for w-LEDs.

In this work, trivalent europium (Eu3+) ion activated K2Sr(MoO4)2 red phosphors have been synthesized through high-temperature solid-state reaction method at 750 ℃. Detailed analysis was conducted on the phase purity, morphology, and luminescence properties of the synthesized phosphors. X-ray diffraction (XRD) confirmed the successful formation of K2Sr(MoO4)2:Eu3+ phosphors with pure phase with space group С2/c. The photoluminescence (PL) spectroscopy was used to record the excitation and emission spectrum of Eu3+ activated K2Sr(MoO4)2 phosphor. Under the excitation of 280nm, the resultant samples exhibited the characteristic emissions of Eu3+ ions corresponding to the 5D0→7FJ transitions. The optimal doping concentration of Eu3+ ions was determined to be 35mol%. Concentration quenching mechanism was identified as the interaction of near-neighbor ions. The chromaticity coordinates of K2Sr(MoO4)2:35mol%Eu3+ were (0.659, 0.340) with a corresponding high color purity of 99.8%. The prepared K2Sr(MoO4)2:35mol%Eu3+ phosphor had good thermal stability with temperature quenching temperature (T0.5 > 420K) and high activation energy (Ea = 0.267eV). The exhaustive findings from this study form the basis for advocating the application of these phosphors in light-emitting devices.

Exploring the Stability of Azto Tfts: The Critical Role of Oxygen Partial Pressure in Performance Optimization

Amorphous oxide semiconductors, such as indium-gallium-zinc oxide (IGZO), have attracted significant attention due to their high electron mobility and low processing temperatures compared to amorphous silicon (a-Si). These characteristics make IGZO suitable for large-area applications, and its transparency holds promise for next-generation electronic devices. However, the commercialization and large-scale production of IGZO are limited by the toxicity of indium and the high cost of gallium. In this context, AZTO can emerges as a cost-effective and less toxic alternative. This study explores the fabrication and characterization of bottom-gate thin-film transistors (TFTs) using aluminum-zinc-tin oxide (AZTO) as an alternative channel material. AZTO films were deposited at room temperature via radio frequency (RF) magnetron sputtering with varying ratios of oxygen and argon. Comprehensive measurements, including temperature stress (TS), negative bias temperature stress (NBTS), activation energy, and density of states (DOS), were conducted to evaluate the electrical properties and stability of the TFTs. The results indicate that increasing the oxygen partial pressure during deposition reduces oxygen vacancies, significantly enhancing the stability of the devices. These findings highlight AZTO as a cost-effective and less toxic alternative to IGZO, particularly in display applications. Additionally, the study provides insights into the fundamental mechanisms governing the electrical behavior of AZTO-based TFTs, further confirming their suitability for advanced display technologies.

Multiobjective Route Optimization for Multimodal Cold Chain Networks Considering Carbon Emissions and Food Waste

The cold chain logistics industry faces significant challenges in terms of transportation costs and carbon emissions. It is imperative to plan multimodal transportation routes efficiently to address these issues, minimize food waste, and reduce carbon emissions. This paper focuses on four key optimization objectives for multimodal cold chain transport: minimizing total transportation time, costs, carbon emissions, and food waste. To tackle these objectives, we propose a high-dimensional multiobjective route optimization model for multimodal cold chain networks. Our approach involves the development of a multiobjective evolutionary algorithm, utilizing Monte Carlo simulation and a one-by-one selection strategy. We evaluate the proposed algorithm’s performance by analyzing various convergence and distribution indicators. The average values for the minimum total transportation time, transportation cost, carbon emission cost, and cargo loss rate derived from the proposed algorithm ultimately converge to 6721.7, 5184.4, 301.5, and 0.21, respectively, demonstrating the effectiveness of the algorithmic solution. Additionally, we benchmark our algorithm against the existing literature to showcase its efficiency in solving high-dimensional multi-objective route optimization problems. Furthermore, we investigate the impact of different parameters, such as carbon tax rates, temperature, and cargo activation energy, on carbon emissions, and food waste. Moreover, we conduct a real-world case study to apply our approach to solving a practical business problem related to multimodal cold chain transportation. The insights gained from this research offer valuable decision-making support for multimodal carriers in developing low-carbon and environmentally friendly transportation strategies to efficiently transport perishable goods.

Enhanced functionalities of isovalently substituted 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) relaxor piezoceramics synthesized via air quenching

The isovalently substituted lead-free binary solid solution, 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) (BF-BT) (x ≤ 0.07), has been synthesized by solid state ceramic method via air quenching sintering. FTIR and XRD along with Rietveld structure refinement confirmed a pure perovskite phase with a pseudocubic structure (space group Pm3‾m) for developed compositions. SEM revealed a dense microstructure with fine grain size (<1.5 μm) and minimal porosity. XPS analysis reveals predominantly Bi+3 and Fe+3 states, along with oxygen vacancies (VO··). Ferroelectric studies demonstrated a maximum remanent polarization (Pr) of 12.3 μC/cm2 and coercive field EC of 30.95 kV/cm for La3+ concentration of x = 0.03. Overall decrement in Pr can be attributed to dipolar defect-induced random fields reducing the activation barrier for domain nucleation. Leakage current measurement reveals improved resistivity (∼108 Ω cm) up to an applied field of 30 kV/cm. Dielectric measurements unveiled two frequency-dependent anomalies in temperature dependence above room temperature, indicative of diffuse phase transitions. The Vogel-Fulcher model depicted an increasing freezing temperature (from 465 K for x = 0.01–551 K for x = 0.07) and decreasing activation energy (from ∼0.61 eV to 0.07 eV) with increasing La3+ concentration. The estimated diffuseness parameter around ∼2 suggested relaxor behavior. Doping with La resulted in increased dielectric permittivity at 10 kHz (from 4100 to 24066), showcasing the efficacy of site engineering in augmenting the functional properties of BF-BT for high-temperature dielectric and transducer applications.

Analysis of subcellular energy metabolism in five Lacertidae lizards across varied environmental conditions

Aerobic respiration is the main energy source for most eukaryotes, and efficient mitochondrial energy transfer greatly influences organismal fitness. To survive environmental changes, cells have evolved to adjust their biochemistry. Thus, measuring energy metabolism at the subcellular level can enhance our understanding of individual performance, population dynamics, and species distribution ranges. We investigated three important metabolic traits at the subcellular level in five lacertid lizard species sampled from different elevations, from sea level up to 2000 m. We examined hemoglobin concentration, two markers of oxidative stress (catalase activity and carbonyl concentration) and maximum rate of metabolic respiration at the subcellular level (potential metabolic activity at the electron transport system). The traits were analysed in laboratory acclimated adult male lizards to investigate the adaptive metabolic responses to the variable environmental conditions at the local sampling sites. Potential metabolic activity at the cellular level was measured at four temperatures – 28 °C, 30 °C, 32 °C and 34 °C – covering the range of preferred body temperatures of the species studied. Hemoglobin content, carbonyl concentration and potential metabolic activity did not differ significantly among species. Interspecific differences were found in the catalase activity, Potential metabolic activity increased with temperature in parallel in all five species. The highest response of the metabolic rate with temperature (Q10) and Arrhenius activation energy (Ea) was recorded in the high-mountain species Iberolacerta monticola.

Synergetic control of multi‐level interface structure of basalt fibers by plasma and chemical functionalization to enhance the mechanical, thermal and interfacial performances of PBZ composites

AbstractThe composites of polybenzoxazine (PBZ) containing functionalized plasma treatment basalt fibers (fP‐BFs) were fabricated through in‐situ polymerization‐mixing technique. fP‐BFs is an effective reinforcement material that can improve the mechanical, thermal, and interfacial properties of composites. Surface activation of fP‐BFs can be enhanced through plasma modification, which improves the interaction between fP‐BFs and 3‐aminopropyltriethoxysilane. A systematic study on fP‐BFs/PBZ composite showed that a processing power of 300 W, a processing time of 5 min, and a fiber content of 9% can achieve good comprehensive mechanical properties. Thermogravimetric analysis results showed that fP‐BFs‐7/PBZ has the highest thermal stability, and its carbon residue rate, decomposition temperature and thermal decomposition activation energy are 36.80%, 452.2 °C and 133.56 kJ/mol, respectively. The dynamic mechanical analysis experiment showed that the addition of fP‐BFs improved the Tg of the composites. Among them, fP‐BFs‐5/PBZ showed the highest Tg, reaching 233.2 °C.Highlights Plasma treatment produced multi‐level structure of basalt fibers (fP‐BFs). Polybenzoxazine (PBZ)/fP‐BFs composites showed excellent performance. Interfacial bonding mechanism between fP‐BFs and PBZ was elucidated. Interfacial interactions between BFs and PBZ contributed to property enhancement. This work provided a green fabrication strategy of PBZ composites.

Differing temperature dependencies of functional homologs zebrafish Abcb4 and human ABCB1.

The ATP binding cassette (ABC) transporters human ABCB1 and zebrafish (Danio rerio) Abcb4 are functionally homologous multixenobiotic/multidrug (MXR/MDR) efflux transporters that confer the efflux of a broad range of diverse chemical compounds from the cell. As ATPases, the transporters utilize the energy released by ATP cleavage for protein conformation changes and concomitant active transport of substrate compounds. The temperatures, at which human ABCB1 and zebrafish Abcb4 need to function, can substantially differ: Whereas the ambient temperature of human ABCB1, which is that of the human body, is constant, zebrafish Abcb4 has to be active in a wider temperature range as the body temperature of zebrafish can considerably vary, depending on the ambient water temperature (18°C-40°C). Here, we examined the effect of temperature on the ATPase activities of recombinant human ABCB1 and zebrafish Abcb4 generated with the baculovirus expression system. Incubation temperatures for enzyme reactions were set to 37°C and 27°C, corresponding to the human body temperature and the cultivation temperature of zebrafish in our lab, respectively. For stimulation and inhibition of zebrafish Abcb4 and human ABCB1 ATPase activities verapamil and cyclosporin A were added at different concentrations and 50% effect concentrations (EC50) were determined. The different temperatures had a stronger effect on the human ABCB1 than on the zebrafish Abcb4 ATPase: Differences between EC50 values for verapamil at 37°C and 27°C, respectively, were 1.8-fold for human ABCB1 but only 1.2-fold for zebrafish Abcb4. Activation energies (Ea) of basal and verapamil-stimulated ATPases, calculated based on the Arrhenius equation, were 2-fold (basal) and 1.5-fold (verapamil-stimulated) higher for human ABCB1 than for zebrafish Abcb4. The differences between zebrafish Abcb4 and human ABCB1 ATPases in temperature sensitivity and activation energy could be important for the comparison of the functional properties of the two transporter proteins in the context of pharmaco-/toxicokinetics. Related to this, our finding that at equal reaction conditions the zebrafish Abcb4 ATPase activity tended to be generally higher than that of human ABCB1 may also be important, as this may point to a higher substrate compound transport rate of Abcb4.

Fe/LiNO3/TiN co–modified MgO for enhanced thermochemical energy storage performance in MgO/Mg(OH)2 cycles

MgO/Mg(OH)2 thermochemical energy storage can convert solar energy and industrial waste heat into forms that are easier to store and transport by cyclic hydration/dehydration reactions. To achieve excellent energy storage performance, cyclic stability and optical absorption capability of MgO/Mg(OH)2, Fe/LiNO3/TiN co–modified MgO were synthesized for energy storage cycles by wet-mixing method. The energy storage performance, cyclic stability and dehydration kinetics of Fe/LiNO3/TiN co–modified MgO were studied in dual fixed–bed system and simultaneous thermal analyzer. The experimental results show that the Fe and LiNO3 in the composite not only increase the hydration conversion of MgO by 6.3 times at 30 min, but also reduce the dehydration temperature and dehydration activation energy of Mg(OH)2 by 99.4 °C and 64 %, respectively. TiN overcomes aggregation of MgO and sustains the excellent porous structure, which results in only a 9 % decrease in energy storage performance of Fe/LiNO3/TiN co–modified MgO after 15 energy storage cycles. Subsequently, TiN significantly strengthens the optical absorption performance of Mg(OH)2 and photothermal temperature under xenon-lamp simulated sunlight radiation. Furthermore, density functional theory calculation reveals that Fe and Li enhance the adsorption of H2O on MgO model and reduce energy barrier for hydration reactions by 62.76 %, while TiN effectively inhibits MgO clusters migration within the material and enhances the optical absorption coefficient. Hence, Fe/LiNO3/TiN co–modified MgO shows significant research value in MgO/Mg(OH)2 energy storage process.

Effect of CaO/MgO on rheological properties and structure of CaO–MgO–SiO2–Al2O3-50 % TiO2 slag with SiO2/Al2O3=1.0

The rheological properties, including viscosity, melting temperature, surface tension, density, and viscous activation energy (Eη) were systematically investigated in the CaO–MgO–SiO2–Al2O3-50 % TiO2 slag system with SiO2/Al2O3 = 1.0. The effect of CaO/MgO on the structure and phase composition of the slag was studied using Raman spectroscopy and X-ray diffraction (XRD). The results of viscosity properties indicate that as the CaO/MgO ratio in the slag increase, viscosity and the viscous activation tend to decrease. Melting temperature and surface tension decreases with increasing CaO/MgO, while density increases. As the CaO/MgO ratio in the slag increases, polymerization decreases, leading to the dissociated basic oxides into metal cations and oxygen anions. This addition of basic oxides provides more O2−, increasing the O/Si ratio, disintegrating complex silica-oxygen composite ions into simple silica-oxygen composite anion, and reducing viscosity. Anosovite (MgTi2O5), CaAl2Si2O8, Mg (Al, Ti)2O4, spinel (MgAl2O4), augite (Ca (Mg, Fe, Al) (Al, Si)2O6) and Ca12Al14O33 were identified as the primary phases in slag. The appropriate CaO/MgO should not exceed 0.76. These findings will serve as a valuable technical foundation to support the development of the direct reduction smelting process for the comprehensive utilization of vanadium titanomagnetite.

Heat transfer in a reversible esterification process of hydromagnetic Casson fluid with Arrhenius activation energy

Engineering technology is rapidly changing, and activation and binary chemical reactions have many uses in the fields of chemical engineering, processing food, and mobility and Geothermal reservoir, etc. Energy activation stimulates reactants with the least energy whenever a chemical transition occurs. The thermophysical features of viscoelastic fluids are based on internal energy change, which has been discussed for years. With this significance the current proposal focuses on the heat transfer process in reversible esterification reactions. The reversible chemical reaction and the activation energy with hydromagnetic movement of Casson fluid are considered. A complex multivariate partial differential equation set can be reduced to ordinary differential equations using appropriate variables. A numerical method is utilized to determine the solutions. In order to examine the outcomes of the concentration boundary layer utilizing the R-K-based shooting technique, the study primarily considers the reversible esterification process, which involves an ethanol-based reversible chemical reaction. Also, the bvp4c solver was employed to validate the results and appraise the precision of the R-K methodology. The temperature field, the momentum field, and the volumetric concentration of the esterification process are analysed in relation to a variety of numerical values. Graphical analysis considers the pertinent physical ramifications for temperature, velocity, and concentration contours. Explications that furnish a comprehension of the values accompany the tabular depictions of the heat transfer rate, local Sherwood number and skin friction. Reversible and irreversible flows differ considerably in the assessment of Sherwood number, local Nusselt number and rate of shear stress, when the inertial parameter, temperature difference parameter and activation energy are measured.

Bioconvective peristaltic transport of hydromagnetic Sutterby nanofluid through a chemically activated porous channel with gyrotactic microorganisms

The main target of this article is to analyze the role of activation energy and thermal radiation effects on the bioconvective peristaltic transport of Sutterby nanofluid in a two-dimensional flexible porous channel with heat and mass transfer. Also, the consequences of Hall current, heat source, and complaint wall properties along with an inclined magnetic field are taken into consideration. The proposed system of governing equations is simplified by using lubrication approximation and solved numerically using MATLAB's bvp5c solver. Further, numerical observations are analyzed to figure out the consequence of different physical parameters on the flow characteristics. According to the observations, it is identified that the Sutterby nanofluid velocity declines with the climb in the damping force parameter, while it enhances with the upsurge in the Darcy number. The Sutterby fluid temperature profile strengthens when the influence of the heat generation and Brinkman number increase, while it depicts the reverse effect with the elevation in the fluid parameter and radiation parameter. The temperature ratio and activation energy parameters were found to have a significant impact on the fluid concentration. The volume of the trapped fluid bolus is an enhancing function of the channel's non-uniformity parameter. Moreover, current work reveals its applicability to recognize the hemodynamic flow analysis and other biofluid movements in the human body and industrial sectors.

Experimental study on moisture diffusivity, activation energy, and mathematical modeling of drying kohlrabi under different solar drying methods

AbstractThe assessment and enhancement of any drying system for optimal drying processes relies on critical parameters, namely moisture diffusivity and activation energy. In this study, medicinally beneficial kohlrabi of 40‐mm diameter and 6‐mm thickness samples were dried under three different drying methods, namely open sun drying (OSD), natural air‐circulation mode (NACM) single slope direct solar dryer (SSDSD), and forced air‐circulation mode (FACM) SSDSD. The experimental results showed that the drying chamber operating temperature and air velocity played significant roles in the moisture diffusion process and activation energy required to dry the kohlrabi sample. The FACM exhibited the highest average moisture diffusivity values at 7.29 × 10−10 m2/s, surpassing both NACM (5.65 × 10−10 m2/s) and OSD (3.28 × 10−10 m2/s). The activation energy needed for the drying process was the lowest in FACM at 27.44 kJ/mol, followed by NACM at 31.37 kJ/mol and OSD at 35.29 kJ/mol. This is due to the uniform temperature distribution and high airflow rate in the case of FACM. Additionally, 10 thin‐layer models were tested for all three experimental conditions. The statistical analysis showed that for OSD and NACM, the Midilli et al. model, and for FACM, the Page model was best suited for representing drying kinetics with lowest χ2 and root mean square error and highest R2 values. Furthermore, the energy and exergy assessment guaranteed an evaluation of the solar drying system's efficiency.Practical applicationsThis research provides valuable insights into optimizing solar drying methods for kohlrabi preservation. Understanding how temperature and air velocity influence moisture diffusivity and activation energy allows practitioners to enhance drying efficiency. Forced air‐circulation mode (FACM) single slope direct solar dryer (SSDSD) emerges superior, with higher moisture diffusivity and lower activation energy. The study also identifies appropriate drying kinetics models for each method, aiding the accurate prediction of drying behavior. Emphasizing efficiency, the research highlights FACM's superior thermal efficiency and natural air‐circulation mode's higher exergetic efficiency. These insights empower practitioners to make informed decisions, potentially improving agricultural product preservation, reducing energy consumption, and promoting sustainability. Moreover, the research's findings hold significant implications for industrial food processing and preservation applications, suggesting the direct implementation of optimized solar drying techniques in large‐scale settings for kohlrabi and similar agricultural products.

Electric current stressing enhanced damping properties in Sn5Sb solder

PurposeThe purpose of this paper is to investigate the effects of electric current stressing on damping properties of Sn5Sb solder.Design/methodology/approachUniformly shaped Sn5Sb solders were prepared as samples. The length, width and thickness of the samples were 60.0, 5.0 and 0.5 mm, respectively. The damping properties of the samples were tested by dynamic mechanical analyzer with a cooling system to control the test temperature in the range of −100 to 100°C. Simultaneously, electric current was imposed to the tested samples using a direct current supply. After tests, the samples were characterized using scanning electron microscope, electron backscatter diffraction and transmission electron microscope, which was aimed to figure out the damping mechanism in terms of electric current stressing induced microstructure evolution.FindingsIt is confirmed experimentally that the increase in damping properties is due to Joule heating and athermal effects of current stressing, in which Joule heating should make a higher contribution. G–L theory can be used to explain the damping properties of strain amplitude under current stressing by quantitative description of geometrically necessary dislocation density. While the critical strain amplitude and high temperature activation energy decrease with increasing electric current.Originality/valueThese results provide a new method for vibration reliability evaluation of high-temperature lead-free solders in serving electronics. Notably, this method should be also inspiring for the mechanical performance evaluation and reliability assessment of conductive materials and structures serving under electric current stressing.

Influence of Sb doping on thermal properties and electrical conductivity mechanism of SbxSe50–xSn20Te30 chalcogenide glassy systems

Tunability of thermal, and electrical characteristics of SbxSe50-xSn20Te30 (x = 2, 4, 6, and 8 at. %) bulk glass systems with varying doping concentrations are the major objective of this study. The melt quenching technique has been employed to synthesize the samples. Various thermal parameters have been inspected by using DSC measurements. The effect of Sb addition on the glass transition temperature (Tg), crystallization temperature (Tc), peak crystallization temperature (Tp), and melting temperature (Tm) have been observed from DSC thermograms. The dependence of Tg, Tc, Tp, and Tm on the heating rate has been measured. The thermal analysis is performed under non-isothermal conditions at heating rates of 5, 10, 15, and 20 K/min. The activation energies for the glass transition temperature are estimated by using the Kissinger method and are found to decrease from (211.21-168.85) KJ.mol−1. Thermal stability and glass forming ability for all glassy compositions have been examined in terms of Hruby's parameter. In addition, electrical conductivity mechanisms over vast temperature and frequency ranges are analyzed. The DC conductivity mechanism has been analyzed by deploying Mott and Greaves's variable range hopping model, while the AC conductivity mechanism has been analyzed by deploying the modified correlated barrier hopping model. AC conductivity scaling property has been examined by using the Pan and Ghosh model. The influence of Sb addition has been observed as the DC and AC conductivity increases with the increase of doping concentration.

Effect of MOF-derived nanoparticle-cumulated flower-like CoFe@C coated composites on hydrogenation/dehydrogenation performance of MgH2

Magnesium hydride (MgH2) has garnered substantial consideration mainly due to its high gravimetric density and reliable resource, whereas its poor thermodynamics and kinetics for absorbing/releasing hydrogen restricts the largescale application. Certain catalysts have demonstrated remarkable activity in enhancing the hydrogen storage capabilities of MgH2. In this work, the nanoparticle-cumulated flower-like CoFe@C coated catalysts (denoted as CoFe@C) are controllably synthesized as expected by the MOF (Metal-Organic Farmwork) in-suit decomposition method at 800 °C, which exhibits an average pore size of 18.63 nm. Meanwhile, the particle size for the as-prepared CoFe alloy coated in carbon layer are approximately 10–20 nm, and the as-prepared samples are introduced to promote the de/rehydrogenation properties of MgH2 at relatively lower temperatures. Due to the synergistic interaction of CoFe alloy nanoparticles serving as active sites and agglomeration resistance of carbon layers, the MgH2 composites doped with CoFe@C-800 could initialize its decomposition process at 175.9 °C, and may desorb 6.0 wt% H2 at 300 °C in 400 s. Additionally, the peak temperature and apparent activation energy during dehydrogenation decline significantly (with 35 % and 38 %, respectively). Furthermore, theoretical analysis results indicate a higher catalytic activity for the carbon-coated CoFe alloy owing to the synergetic effect between CoFe nanocomposite & carbon layer, which can facilitate the bond extension and strength decrease of Mg-H bonding. In brief, using MOF may derive transition metal and carbon layer, which could be a promising approach to stimulating the hydrogen storage properties of MgH2.

Modulating the Electronic States of Pt Nanoparticles on Reducible Metal-Organic Frameworks for Boosting the Oxidation of Volatile Organic Compounds.

The adsorption and activation of pollutant molecules and oxygen play a critical role in the oxidation reaction of volatile organic compounds (VOCs). In this study, superior adsorption and activation ability was achieved by modulating the interaction between Pt nanoparticles (NPs) and UiO-66 (U6) through the spatial position effect. Pt@U6 exhibits excellent activity in toluene, acetone, propane, and aldehyde oxidation reactions. Spectroscopic studies, 16O2/18O2 kinetic isotopic experiments, and density functional theory (DFT) results jointly reveal that the encapsulated Pt NPs of Pt@U6 possess higher electron density and d-band center, which is conducive for the adsorption and dissociation of oxygen. The toluene oxidation reaction and DFT results indicate that Pt@U6 is more favorable to activate the C-H of toluene and the C═C of maleic anhydride, while Pt/U6 with lower electron density and d-band center exhibits a higher oxygen dissociation temperature and higher reactant activation energy barriers. This study provides a deep insight into the architecture-performance relation of Pt-based catalysts for the catalytic oxidation of VOCs.

Carbide precipitation during tempering of hybrid steel 60

The effects of carbide precipitation on mechanical performance of Hybrid Steel 60, known as a novel bearing steel, have not been investigated. In this study, the austenite transformation temperatures of Hybrid Steel 60 during heating were revealed by the thermal expansion curve. The temperature and effective activation energy of the second phase precipitation were determined by the differential scanning calorimetry (DSC) curve. Different solid solution structures after austenitization were detected using various cooling rates. The solubility temperature was determined based on hardness and residual austenite content. The carbides precipitated at the peak temperature were qualitatively identified using XRD. It was discovered that the temperature points Ac1 and Ac3 of the steel were 786 °C and 864 °C, respectively. In addition, the effect of solid solution temperature on quenching hardness is minimal, while the cooling rate has a greater impact on hardness, reaching a peak at 5 °C s−1. The primary carbide phase in Hybrid Steel 60 is the M7C3 and VC. When the temperature ranges from 500 °C to 550 °C, M23C6 begins to precipitate. As a result, after tempering at 525 °C, the hardness peak value reached 566 HV.

Experimental investigation on the suppression of aluminum dust explosion by sodium carbonate powder

To prevent the potential explosion accidents in industries involving aluminum powder, the effectiveness of Na2CO3 in inhibiting aluminum dust explosions was investigated using thermal methods and explosion tests. Furthermore, the surface morphologies and chemical compositions of the resultant explosion products were characterized to illustrate the inhibition mechanism of Na2CO3 powder. The results revealed a marginal increase in ignition temperatures and a decrease in combustion peak temperature as the proportion of Na2CO3 increased. Notably, within the range of 0–450%, a notable reduction was observed in both the maximum explosion pressure (from 0.68 to 0.06 MPa) and the maximum pressure rising rate (from 91.93 to 2.87 MPa/s). In particular, as the percentage of Na2CO3 increased, a gradual decrease in flame brightness and average flame velocity was observed. Moreover, a negative relationship was observed between ignition temperature and apparent activation energy with maximum explosion pressure and maximum pressure rising rate. An analysis of the explosion residues indicated the presence of Na2CO3, NaOH, Al2O3, Al(OH)3, Na(AlO)2, Na2O and unburned aluminum. The inhibition mechanisms of Na2CO3 involved heat absorption, isolation, and the consumption of free radicals. These results offer valuable insights that can aid in mitigating the risks associated with aluminum dust explosion.