Activation Energy For Diffusion Research Articles

Utility and influence mechanism of densification modulation on grain boundary diffusion in NdFeB magnets

Grain boundary diffusion technology is pivotal in the preparation of high-performance NdFeB magnets. This study investigates the factors that affect the efficiency of grain boundary diffusion, starting from the properties of the diffusion matrix. Through the adjustment of the sintering process, we effectively prepared magnets with varied densities that serve as the matrix for grain boundary diffusion with TbHx diffusion. The mobility characteristics of the Nd-rich phase during the densification stage are leveraged to ensure a more extensive distribution of heavy rare earth elements within the magnets. According to the experimental results, the increase in coercivity of low-density magnets after diffusion is significantly greater than that of relatively high-density magnets. The coercivity values measured are 805.32 kA/m for low-density magnets and 470.3 kA/m for high-density magnets. Additionally, grain boundary diffusion notably enhances the density of initial low-density magnets, addressing the issue of low density during the sintering stage. Before the diffusion treatment, the Nd-rich phases primarily concentrate at the triangular grain boundaries, resulting in an increased number of cavity defects in the magnets. These cavity defects contain atoms in a higher energy state, making them more prone to transition. Consequently, the diffusion activation energy at the void defects is lower than the intracrystalline diffusion activation energy, accelerating atom diffusion. The presence of larger cavities also provides more space for atom migration, thereby promoting the diffusion process. After the diffusion treatment, the proportion of bulk Nd-rich phases significantly decreases, and they infiltrate between the grains to fill the cavity defects, forming continuous fine grain boundaries. Based on these observations, the study aims to explore how to utilize this information to develop an efficient technique for grain boundary diffusion.

Accurate Calculation of Solid-State Li+ Diffusion Coefficient and Kinetic Activation Energies for an Artificial Graphite Anode

The slow electrochemical reaction kinetics of artificial graphite is one of the limiting factors for safety of lithium-ion batteries, especially the lack of systematic research on activation energies of various kinetic processes. In this work, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic intermittent titration technique (GITT) were used to investigate key kinetic parameters of artificial graphite such as solid-state Li+ diffusion coefficient (D Li+) and activation energy. The results reveal the evaluation of the chemical diffusion coefficient of same material is independent of the technique and shows a similar value, with D Li+ ranging from 10−11 to 10−13 cm2·s−1. The activation energies measured by EIS and GITT for solid-state Li+ diffusion in graphite at 50% depth of discharge are 74.5 kJ·mol−1 and 66.8 kJ·mol−1, which are in the same order of magnitude as the activation energies of charge transfer resistance (59.5 kJ·mol−1), electrode/electrolyte interface membrane impedance (56.1 kJ·mol−1), and ohmic impedance (6.6 kJ·mol−1). It demonstrates that the solid-state Li+ diffusion, interface charge transfer process, and Li+ transmission through SEI membrane are significantly affected by temperature. This work provides a reliable parameter basis for establishing more accurate thermal-electrochemical coupling models and designing safer battery thermal management systems for lithium-ion batteries.

Determining the effective diffusivity coefficient and activation energy in thin-layer drying of Haj Kazemi peach slices and modeling drying kinetics using ANFIS

Abstract This study investigated the moisture changes in Haj Kazemi peach slices during drying in a thin-layer dryer at five temperature levels (40, 50, 60, 70, and 80°C), three levels of inlet air velocity (1, 1.5, and 2 m/s), and three slice thicknesses (2, 4, and 6 mm). The relative moisture content during drying was calculated, and an adaptive neuro fuzzy inference system (ANFIS) was used to predict the drying process of peach slices. The results indicated that slice thickness had a greater impact on drying time than air velocity. Moreover, an almost direct relationship was observed between changes in slice thickness and drying time. The effective moisture diffusivity coefficient in peach slices increased with an increase in slice thickness, temperature, and air velocity and ranged from 9.57 × 10^-10 to 4.33 × 10^-9 m^2/s under different experimental conditions. The calculated activation energy for drying peach slices under experimental conditions ranged from 16.74 to 20.48 kJ/mol. The designed model for simulating the drying conditions was based on an adaptive neuro fuzzy inference system (ANFIS) with input and output membership functions of triangular and linear shapes and a hybrid learning algorithm. The model could simulate the drying process with a correlation coefficient of 0.979.

Diffusion coefficients of zirconium (IV) acetylacetonate: Measurements and correlation in both pressurized liquid and supercritical fluid

Limited data exist on the diffusion coefficient of a solute in both pressurized and supercritical fluids, despite its crucial role as an essential transport property. In this study, we present the first-ever determined diffusion coefficients of zirconium acetylacetonate (Zr(acac)4) in two distinct fluids: pressurized ethanol and supercritical carbon dioxide. Using the Taylor dispersion method, we measured the diffusion coefficients in pressurized ethanol at temperatures between 298.15 and 333.15 K, reaching pressures up to 30.00 MPa. In supercritical carbon dioxide, we employed the chromatographic impulse response (CIR) method, conducting the experiments at temperatures from 308.15 to 343.15 K and pressures up to 35.00 MPa. Remarkably, predissolving Zr(acac)4 in supercritical carbon dioxide and injecting it into the diffusion column enabled the accurate determination of diffusion coefficients in supercritical carbon dioxide, which were approximately an order of magnitude higher than those in pressurized ethanol. Our investigation revealed diffusion activation energies, ranging from 26.7 to 10.2 kJ mol−1 at pressures between 10.00 and 30.00 MPa in supercritical carbon dioxide and from 20.4 to 19.6 kJ mol−1 at pressures between 20.00 and 30.00 MPa in pressurized ethanol. All diffusion data, in both liquid and supercritical states, can be effectively correlated using the equation Sc = ∑n=03(Cnηn) with 2 parameters and 4 adjustable coefficients. This correlation demonstrates high accuracy, with an average absolute relative deviation (AARD) of 3.7 % over a wide fluid viscosity range of 21.0 to 1305.0 μPa s. Additionally, it is observed that all diffusion data can also be well-fitted with the equation D12/T = αηβ with 2 parameters and 2 adjustable coefficients, achieving an AARD of 3.5 %.

Drying Kinetics and Mass Transfer Characteristics of Walnut under Hot Air Drying

This study was conducted to investigate the drying kinetics and internal and external mass transfer characteristics of walnuts for an understanding of the drying mechanism. The drying characteristics, mass transfer characteristics, and color of walnut during hot air drying (HAD) were investigated under different initial moisture content (IMC) (0.35, 0.39, and 0.43 g water/g wet mass) and drying temperatures (50, 60, 70, and 80 °C). The results indicated that the IMC and drying temperature both have significant effects on the drying process of walnut, showing the higher the IMC, the longer the preheating time, the smaller the effective moisture diffusivity (Deff) and mass transfer coefficient (hm), and the longer the drying time, but reverse results for drying temperature. The values of Deff and hm for walnut ranged from 4.94 × 10−10 to 1.44 × 10−9 m2/s and 1.24 × 10−7 to 3.90 × 10−7 m/s, respectively. The values of activation energy for moisture diffusion and mass transfer ranged from 21.56 to 23.35 kJ/mol and 28.92 to 33.43 kJ/mol, respectively. Multivariate linear prediction models were also established for estimating the Deff and hm as a function of the HAD process parameters. The drying temperature has a greater effect on the walnut kernel lightness than the IMC. The Verma et al model could be used to describe the HAD process of the walnut. The findings contribute to the understanding of moisture transfer mechanisms in walnuts and have practical value for the evaluation and improvement of drying systems.

First-principles study of diffusion of intrinsic point defects in tungsten borides

The evolution of point defects is crucial in determining the radiation resistance of materials in a fusion environment. A comprehensive investigation of diffusion mechanisms for intrinsic point defects in six stoichiometric tungsten borides (WxBy), including W2B, WB, WB2, W2B5, WB3 and WB4, has been performed using first-principles density functional theory (DFT) calculations based on the W boride with a minimum formation enthalpy for each involved stoichiometry. The calculations indicate that boron point defects are more mobile than W point defects in each W boride. The activation energy of the W vacancy (VW) diffusion in W borides increases with B content. In general, with increasing B content, the activation energy for one-dimensional (1D) diffusion of B vacancy (VB) slightly decreases, while the activation energy for 3D diffusion of VB does not show a clear trend with B content. VW in B-rich WxBy (y/x > 1) enhances the mobility of adjacent B lattice atoms. In W2B, WB and WB2 compounds, complex configurations of W interstitials (IW), which involve B displacement, are more energetically stable than single W atoms at interstitial sites; while no or less stable complexes of W interstitials are observed in W2B5, WB3 or WB4. The activation energy for 1D/2D diffusion of IW in B-rich compounds increases with B content, and the 3D diffusion of IW in WB3 has the largest activation energy. The activation energy for 1D/2D diffusion of B interstitials (IB) generally increases with B content; however, the activation energy for 3D diffusion of IB is dependent on specific W boride composites. This study is helpful in building a database related to the diffusion behavior of defects in stoichiometric W borides. It is important to note pre-existing, as well as irradiation-induced, defects in non-stoichiometric WxBy will impact the diffusion kinetics of all intrinsic species, which needs further investigation.

Effects of pectin and temperature on the diffusion of ions and water in saltwater membranes

In this study, we investigate the structural and dynamical characteristics of the biopolymer pectin, exploring its impact on ion transport, diffusion activation energy, and relaxation timescales within a saltwater environment (100 mM NaCl (aq.)) using classical molecular dynamics (MD) simulations. Our analysis of radial distribution functions (g(r)) reveals a notable preference of Na+ ions to interact more extensively with pectin compared to Cl– ions. Moreover, we observe slight variations in the strength of inter-ion interactions, with a modest decrease in ion-pectin interaction strength with increased pectin loading. Additionally, our findings indicate that sodium exhibits the lowest diffusion coefficient due to the presence of significant energy barriers among Na+, Cl–, and water molecules, following the sequence: D(water) > D(Cl–) > D(Na+) at any pectin loading and temperature conditions within pectin-saltwater membranes. Furthermore, our study demonstrates that viscosity, ion-pair relaxation timescales and ion-cage relaxation timescales exhibit monotonic increases with pectin loading while displaying the opposite trend with temperature. Overall, our simulations strongly endorse the use of biopolymer pectin as a highly promising and innovative option for a wide range of industrial applications, including flexible hydrogel electrolytes and saline water treatment.

Comparison of Two Methods for Measuring the Temperature Dependence of H2 Permeation Parameters in Nitrile Butadiene Rubber Polymer Composites Blended with Fillers: The Volumetric Analysis Method and the Differential Pressure Method.

Hydrogen uptake/diffusivity in nitrile butadiene rubber (NBR) blended with carbon black (CB) and silica fillers was measured with a volumetric analysis method in the 258-323 K temperature range. The temperature-dependent H2 diffusivity was obtained by assuming constant solubility with temperature variations. The logarithmic diffusivity decreased linearly with increasing reciprocal temperature. The diffusion activation energies were calculated with the Arrhenius equation. The activation energies for NBR blended with high-abrasion furnace CB and silica fillers increased linearly with increasing filler content. For NBR blended with medium thermal CB filler, the activation energy decreased with increasing filler content. The activation energy filler dependency is similar to the glass transition temperature filler dependency, as determined with dynamic mechanical analysis. Additionally, the activation energy was compared with that obtained by the differential pressure method through permeability temperature dependence. The same activation energy between diffusion and permeation in the range of 33-39 kJ/mol was obtained, supporting the temperature-independent H2 solubility and H2 physisorption in polymer composites.

Vanadium substituted Fe, Cr co-doped high performance C/Na3V2(PO4)2F3 cathode for sodium-ion batteries

In recent years, Na3V2(PO4)2F3 (NVPF) has been considered as one of the most promising candidates for cathodes in sodium ion batteries (SIBs). However, presence of vanadium makes the material costly. Besides, its electrochemical properties are hampered due to its low electronic conductivity. Herein, carbon coated Fe, Cr co-doped Na3V2(PO4)2F3 has been synthesized using rota-tumbler assisted sol–gel method. The effects of co-doping on structure, morphology and electrochemical performances are systematically studied. It is confirmed that co-doping of Fe and Cr can enhance the electrochemical performances of NVPF. Among all, Na3V1.9Fe0.095Cr0.005(PO4)2F3 shows a high initial capacity of 119.85 mAhg−1 at 0.1C and maintains a capacity retention of 88.58 % after 500 cycles at 1C. Increase in the size of the saddle point, planes of monocapped trigonal prisms and the hexagonal cavities help in decreasing the ion diffusion activation energy, thus improving the diffusivity of the doped material. The improved electrochemical performances can be attributed to the increase in the electronic conductivity of the material. Besides, vanadium reduction in the cathode aids in manufacturing cost reduction. Our work demonstrates that carbon coated Na3V1.9Fe0.095Cr0.005(PO4)2F3 can be considered as a potential cathode candidate for practical applications in SIBs.

Optimizing solid electrolytes with 3d transition metal doped Li3YCl6 for Li-ion batteries

Li3YCl6 is a promising candidate for solid electrolytes (SEs) in all-solid-state Li-ion batteries due to its high ionic conductivity, electrochemical stability, and compatibility with metal-oxide electrodes. The monoclinic and trigonal crystal structures of Li3YCl6 with space groups C2/c and P-3m1 have been studied extensively, while little attention has been given to the trigonal P-3c1 phase (space group no. 165). Additionally, Li-ion diffusion mechanism in 3d transition metal (TM) substituted compounds along with their structural stability are interesting to study. Therefore, we investigate the Li diffusion mechanism in Li3YCl6 and TM substituted Li3YCl6 in the P-3c1 phase using first-principles calculations. We have found that all the substituted compounds are thermodynamically stable at room temperature and show high oxidation stability. Li3Y0.875Co0.125Cl6 exhibits the lowest activation energy (0.11 eV) for Li-ion diffusion and the highest Li-ion mobility (σ = 0.39 mS cm−1 at room temperature), which is strongly anisotropic. We used the Crystal Orbital Hamilton Population method to analyze the bonding characteristics of Li3YCl6 and 3d TM substituted Li3YCl6 and found that the Co–Cl bond is weaker than the Cr–Cl bond. This may explain the lower activation energy observed for Li3Y0.875Co0.125Cl6. Our results provide insights into the substitution effect in Li3YCl6 superionic conductors, which could guide the design and development of high-performance SEs for Li-ion batteries.

Hydrogen interaction with vacancy defects in tungsten: Unraveling the influence on diffusion mechanisms and mechanical properties

This study investigates hydrogen diffusion in tungsten at high temperatures using molecular dynamics simulations. It explores the effect of different hydrogen concentrations on diffusion mechanisms, the interaction of hydrogen atoms with vacancy defects, and their impact on the mechanical properties of tungsten. The activation energy for hydrogen diffusion in perfect bulk tungsten with 0.1 % hydrogen concentration is calculated as 0.235 eV, with a diffusion pre-exponential factor of 5.336 × 10-8 m2/s at temperatures ranging from 1000 to 3000 K. The investigation reveals two factors contributing to the increase in activation energy with temperature: migration paths involving TIS-TIS and TIS-OIS-TIS pathways, and an increase in migration energy. Three diffusion regimes are identified, with trapping effects dominating at temperatures below 1500 K, TIS-TIS pathway dominating at intermediate temperatures, and TIS-OIS-TIS pathway becoming more prominent at higher temperatures. Increasing hydrogen concentration up to 2 % (H/W concentrations in fusion environments) has minimal effect on diffusion in perfect tungsten. However, in a W-H-V system with a 1 % vacancy defect, increasing hydrogen concentration increases the effective diffusion coefficient and activation energy. The presence of hydrogen atoms and vacancy defects reduces the tensile strength and elastic modulus of tungsten, with hydrogen atoms having a greater impact on mechanical properties compared to vacancies. The degree of reduction in mechanical properties is proportional to the concentration of hydrogen atoms and vacancy defects.

Superior damping capacity of a C-containing FCC medium-entropy alloy

Construction machinery noise not only affects its service life, but also brings hazards to people's physical and mental health. Achieving a high and stable internal friction characteristic to eliminate noise and mechanical vibrations is always the desired goal in the design of damping alloys. In the study, we present a C-containing Fe-Mn-Cr-Ni medium entropy alloy that exhibits a superior damping capacity with an internal friction peak value of 0.083. The Finkelstein-Rosin relaxation peak appears at 550 K in the internal friction spectrum, which is attributed to the reorientation of C-C pairs and C substitutional atom pairs under stress, with the diffusion activation energy are 155.172 kJ·mol−1 and 166.711 kJ·mol−1, respectively. The relaxation of Finkelstein-Rosin peak enhances the damping capacity of the alloy, which provides an effective method for regulating the damping properties of medium entropy alloys.

Effect of tunable composition-shape of bio-inspired Pt NPs electrocatalyst in direct methanol fuel cell: Process optimization and kinetic studies

Highly efficient bio-inspired platinum nanoparticles (Pt NPs) as an electrocatalyst with superior intrinsic kinetics and high performance for methanol oxidation reaction (MOR) derived from green synthesis of bio-waste utilization is of great interest. The bio-inspired Pt NPs were examined for their kinetic parameters in terms of the Tafel plot, exchange current, square root of the scan rate, methanol diffusion coefficient, activation energy (Ea), and factors influencing current density. Bio-inspired Pt NPs exhibit a fast kinetic reaction with a low Tafel value of 179 mV dec−1 and exchange current, α = 0.33, compared to commercial Pt black (233 mV dec−1, α = 0.25). The bio-inspired Pt NPs display low activation energy, Ea, as the potential increases, indicating improved intrinsic kinetics, and the MOR catalyzed by bio-Pt NPs was discovered to be a diffusion-controlled process. The parametric effect of bio-inspired Pt NPs concentration has a crucial influence on the anisotropic morphological structure and interconnection to the current density (mA mg−1) of MOR. Central Composite Design (CCD) was applied for RSM-based modeling and analyzing the parameter effects, including bio-inspired Pt NPs concentration, methanol concentration, and electrocatalyst loading to optimize the current density. The optimized current density produced by bio-inspired Pt NPs was 640.11 mA mgPt−1 at ideal conditions of 1.5 mM bio-Pt NPs, 1.05 M CH3OH, and 2.14 mg. Ultimately, the passive DMFC single-cell powered by bio-inspired Pt NPs generates power density with Pmax of 5.70, 6.67, and 8.28 mW cm−2 at 25, 80, and 100 °C. Thus, bio-inspired Pt NPs derived from green synthesis pathways and biomass-mediated extract have been proven to be viable and sustainable anode electrocatalysts for utilization in the energy conversion of renewable energy with outstanding performance.

First-principles studies on behaviors of Ni impurities in d-MAX phase Ti3AlC2

The performance and stability in numerous energy and electronic devices can be critically affected by the inter-diffusion along the metal/ceramic interface. Understanding the nickel (Ni) incorporation into the Ti3AlC2 ceramic is necessary to estimate the material performance for the fabrication of the crucial heated end components of aeronautics and astronautics. The effect of Ni diffusion on Ti3AlC2 was investigated using the First-principles method. Calculation results demonstrate that the excellent electrical conductivity of Ti3AlC2 ceramic is mainly contributed by Ti atoms. The binding energy and formation energy of the perfect unit cell of Ti3AlC2 and the single vacancy system at different atomic layer positions were calculated. It is found that, Al vacancy was considered to be the most easily formed defect in Ti3AlC2. The Ni substitutions at different atomic layer of Ti3AlC2 ceramic are introduced. Results shows that the Ni atoms are most likely to be observed on Al sites due to the lowest defect formation energy (1.369eV), which indicating that the activation energy for diffusion along coherent Ni/Ti3AlC2 interfaces is feasible.

Anisotropic growth of nano‐precipitates governed by preferred orientation and residual stress in an Al‐Zn‐Mg‐Cu alloy

Through an understanding of diffusion, precise control of the size distribution of nano-precipitates can be essential to developing superior properties in precipitation-strengthened alloys. Although a significant influence of crystallographic orientation on the diffusion process is known to exist in low-symmetry hexagonal close-packed alloys, such anisotropic diffusion is still unidentified in high-symmetry cubic alloys. In this work, we reveal the diffusion-controlled coarsening induced anisotropic growth process of nano-precipitates in an Al-Zn-Mg-Cu alloy. Our experimental and theoretical studies demonstrate that with an increase in the residual stress, the diffusion-controlled coarsening rate is slow along the 〈112〉 fiber texture in the alloy matrix with smaller grain sizes. As such, we find that the diffusion activation energy will be increased along the preferred orientation with largest residual stress, which leads to a reduced diffusion-controlled coarsening rate. Specifically, we demonstrate that the increase in the volume fraction of nano-precipitates originates from the rapid grain-boundary controlled coarsening of the grain-boundary precipitates. Based on these results, an underlying microstructural design strategy is proposed, involving the crystallographic orientation, the residual stress and the grain boundaries to manipulate the precipitate size distribution in this class of alloys.

Coarsening mechanism of over-aged δ-Ni2Si nanoscale precipitates in Cu-Ni-Si-Cr-Mg alloy

δ-Ni2Si precipitate is the crucial strengthening phase in Cu-Ni-Si alloy, and its coarsening behavior and mechanism impose dramatic effects on mechanical properties. In this paper, Cu-3Ni-0.7Si-0.1Cr-0.05 Mg (wt%) alloy was prepared to systematically investigate the coarsening behavior and elucidate the coarsening mechanism of δ-Ni2Si precipitate during over-aging treatment. Featured core-shell structure was observed via careful characterization during coarsening of δ-Ni2Si phase. Specifically, the core structure was stable δ-Ni2Si, while the shell structure was a metastable interface composed of Cu, Ni and Si elements. At later over-aging stage, the core-shell structure completely transformed into a stable and coarsened δ-Ni2Si phase being coherent with the Cu matrix. It is confirmed for the first time that the coarsening process of δ-Ni2Si precipitate can be interpreted by the trans-interface-diffusion-controlled (TIDC) coarsening theory. The core-shell structure was caused by the disparity between the diffusion activation energy and diffusion rate of Ni, Si, and Cu from the perspective of diffusion kinetics. Moreover, the presence of trace amounts of Cr and Mg components exhibited little effect on the coarsening process of δ-Ni2Si. During over-aging, tensile strength dramatically decreased owing to diminishing precipitation strengthening effect from coarsening of δ-Ni2Si precipitates.

NV centres by vacancies trapping in irradiated diamond: experiments and modelling

Advances in applications of nitrogen-vacancy (NV) spin centres in diamond for sensing and quantum metrology depend critically on the NV fabrication methods. One such technique combines epitaxial diamond growth and electron or ion irradiation (He, C, etc), where NVs are activated by vacancy trapping at the nitrogen donor atoms upon thermal diffusion. In this work we study the efficiency of such method by analyzing NV depth profiles created by 340 keV and also 4 keV He irradiation in high purity CVD and HPHT diamond crystals and subjected to sequent annealing at 950 °C and 1200 °C temperatures. This analysis is coupled with the measurement of NV density in the bulk of CVD diamonds with nitrogen doping at low-ppb and low-ppm levels, exposed to MeV electrons in a wide range of the doses. For data analysis we developed an atomistic model based on probabilistic atomic jumps in a crystal lattice, which considers competitive trapping between di- (V2) or multi-vacancy defects compared to that of NVs. The efficiency of NV formation was defined as a ratio of the corresponding capture cross sections: σ NV vs. σV2 . Applying this model to the experimental data, the σNV/σV2 ratio was estimated about 0.1–0.5, where the activation energy of vacancy diffusion of about 1.7 eV was evaluated by 3D localization of individual NVs in depth profiles in a confocal microscope and sampling their spin coherence properties ( T2 ). In addition, we noted two subsidiary effects also discussed here: (i) reduction of NV density within the stopping range of the implanted He atoms after 1200∘ annealing and, (ii) partial suppression of NVs at near-surface areas visible only at low-dose electron exposures. The results of this study could be helpful to optimize the NV fabrication process reducing the density of ‘collateral’ lattice damage.

Thin‐Layer Drying Model, Drying Rate, and Effective Water Diffusion Coefficient of Pelleted Feed

In this study, classic thin‐layer drying models such as the Page model, Verma model, and Two‐term model were used to fit the thin‐layer drying data of feed. Based on this, a novel thin‐layer drying model for pelleted feed (modified Verma model) was proposed. The results indicate that the new model is the optimal choice for describing the drying kinetics of pelleted feed for growing pig and calf. The drying rate of pelleted feed is linearly correlated with the feed moisture content. The effective water diffusion coefficient for pelleted feed of growing pig and calf ranges from 1.86 × 10−10 to 2.75 × 10−9 m2/s and 3.32 × 10−10 to 3.87 × 10−9 m2/s, respectively. The activation energy (Ea) for moisture diffusion in both types of feed is 26.42 kJ/mol and 25.86 kJ/mol, respectively. By establishing predictive models for model parameters based on air temperature and air velocity variables, the new model demonstrates extrapolation capability, wide applicability, and practical value. This work lays the foundation for developing a similarly characterized deep‐bed cooling drying model for pelleted feed.

Growing sp2 materials on transition metals: calculated atomic adsorption energies of hydrogen, boron, carbon, nitrogen, and oxygen atoms, C2 and BN dimers, C6 and (BN)3 hexamers, graphene and h-BN with and without atomic vacancies.

The growth of graphene and hexagonal boron nitride on hot transition metal surfaces involves the adsorption of precursor molecules, and their dissociation and assembly into two-dimensional honeycomb lattices. In a recent account it was found that h-BN may be distilled on a rhodium metal surface, which yields higher quality h-BN [Cun et al., ACS Nano, 2020, 15, 1351]. In this context, we calculated in a systematic approach the adsorption energies and sites of hydrogen, boron, carbon, nitrogen, and oxygen atoms and from the site dependence the activation energy for diffusion. Existing computed values of the solvation energy into the bulk were compared to the present ones with our calculation scheme and found to be in good agreement. For the distinction of different systems we introduce the concepts of epiphilicity and epiphobicity. The adsorption energies and stabilities of the C2 and BN dimers, the C6 and (BN)3 ring-hexamers and the graphene and h-BN monolayers allow the prediction of the performance of different substrates in chemical vapor deposition (CVD) processes for the growth of graphene and h-BN. Finally, vacancy creation energies were calculated as a criterion for the stability of graphene and h-BN on metallic substrates.

Unraveling fundamental characteristics of Na2Mg3Cl8 as a solid-state electrolyte for Na-ion batteries.

In this theoretical study, we harnessed advanced atomistic computations to unravel several features of Na2Mg3Cl8, an unexplored but promising chloride compound for solid-state electrolytes in Na-batteries. First, Na2Mg3Cl8 exhibits an insulating behavior, characterized by an energy gap of ∼5 eV, arising from the hybridization of [NaCl] trigonal prismatic and [MgCl6] octahedral units. Second, the compound possesses mechanical stability and ductility, which render it suitable for practical fabrication. Improved electrolyte/electrode contact can reduce resistance and enhance battery performance. The electrochemical performance of Na2Mg3Cl8 involves an open cell voltage of 1.2 V and a theoretical capacity of 133 mA h g-1. Finally, its transport characteristics include low activation energy for diffusion and conduction as well as a remarkable room-temperature conductivity of 1.26 mS cm-1, comparable to those of current superionic conductors.