Nucleation Energy Research Articles

Thermodynamic and kinetic analyses of Janus membrane scaling in membrane distillation for zero liquid discharge engineering

Scaling phenomena are the principal obstacle to the factual application of membrane distillation (MD). In this study, we fabricated a Janus membrane composed of a commercial polytetrafluoroethylene substrate, a superhydrophobic surface layer, and a hydrophilic reverse side coated by MXene nanosheets via a simple spraying method. The virgin and modified membranes were carried out and compared in zero liquid discharge (ZLD) MD experiments. MD flux analysis showed that all the membranes experienced severe flux decline during the ZLD process. Saturation index, Gibbs free energy and nucleation energy barrier were calculated to explain the observed difference in scaling behavior. Screenage assessment of the homogeneous nucleation and heterogeneous nucleation showed that the severe scaling developed from some small clusters of the new phase, wherein the thermodynamic energy barrier played a critical role in determining the anti-scaling behavior for these unsmooth surfaces. Model analysis and data fitting were used to conclude the kinetic behavior of the virgin and modified membranes in the ZLD engineering. Finally, we evaluated the reversible and irreversible scaling after twice washing. Therefore, this study may provide instructive insights to design novel anti-fouling membranes and promote practical applications such as industrial brine treatment and ZLD engineering.

THERMAL STABILITY OF CAST CONDUCTOR MICROALLOYED ALUMINUM ALLOYS

The nucleation of the Al3X (X = Zr, Yb, Er, Hf) particles in the cast conductor Al alloys including the alloys additionally doped with Mg and Si was studied. The alloys were made by induction casting. To investigate the particle nucleation kinetics, the specific electrical resistivity (SER) and microhardness measurements were applied. It was shown that the investigated alloys can be subdivided into three groups. Group I includes the alloys, which the decrease in the SER with increasing annealing temperature takes place in due to the particle nucleation. Group II includes the alloys, which the particle nucleation takes place in during the bulk crystallization. The SER magnitude of such alloy was close to the SER of pure Al. The SER of the alloys of Group III almost doesn’t change during annealing and is 3.0-3.4 ·cm that evidences a high alloy solid solution stability. Using Jonhnson-Mehl-Avrami-Kolmogorov equation, the particle nucleation kinetics in the Group I alloys was analyzed. The activation energy of the particle nucleation in the Group I alloys was found to be close to the activation energy of volume diffusion, but the values of the decomposition intensity coefficient (n = 0.5-0.8) in Johnson-Mehl-Avrami-Kolmogorov equation appeared to be smaller that the theoretical value n = 1.5 typical for the particle nucleation inside the bulk crystal lattice. This contradiction was related to the presence of large primary or eutectic Al3X particles in the alloy structure. The Al-0.25%Zr-0.25%Er-0.15%Si alloy was shown to have the optimal set of properties: the characteristics of this alloy after annealing match the requirements to the alloys being developed: SER less than 2.95 ·cm, microhardness Hv ~ 550 MPa.

Dendrite-free potassium metal anode induced by in-situ phase transitions of MoS2

Potassium ion batteries (PIBs) are identified as an imperative alternative for next-generation energy storage devices due to its abundant reserves. Even potassium (K) metal is a promising anode for its high theoretical capacity and intrinsic low potential, however, it still suffers from uncontrollable dendrite growth. Herein, a dendrite-free K anode is obtained by plating K metal on MoS2-modified carbon cloth (MoS2/CC@K). Specifically, MoS2 undergoes a series of phase transitions from initial MoS2 to KxMoS2 and final K2S4 with gradual insertion of K, then K metal is uniformly deposited on K2S4 with further discharging. This phase transition significantly reduces the K nucleation energy barrier. The strong interaction between K and K2S4 interface induces K in uniformly depositing to suppress the formation of K dendrites. Owing to these merits, the symmetric MoS2/CC@K cells exhibit low voltage hysteresis and superior cycling stability. When paired with perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) cathode, the full cells display superior rate capability and long lifespan (10,000 cycles). Additionally, this strategy is also performed on Li and Na metal anodes, the MoS2/CC substrate still expresses superior electrochemical performance. This work provides a new view to induce the uniformly deposition of K, Li and Na metals.

Iodine-assisted ultrafast growth of high-quality monolayer MoS<sub>2</sub> with sulfur-terminated edges

Two-dimensional (2D) semiconductors have attracted great attention to extend Moore’s law, which motivates the quest for fast growth of high-quality materials. However, taking MoS2 as an example, current methods yield 2D MoS2 with low growth rate and poor quality with vacancy concentrations three to five orders of magnitude higher than silicon and other commercial semiconductors. Here, we develop a strategy of using intermediate product of iodine as a transport agent to carry metal precursors efficiently for ultrafast growth of high-quality MoS2. The grown MoS2 has the lowest density of sulfur vacancies (~ 1.41 × 1012 cm-2) reported so far and excellent electrical properties with high on/off current ratios of 108 and carrier mobility of 175 cm2V-1s-1. Theoretical calculations show that by incorporating iodine, the nucleation barrier of MoS2 growth with sulfur-terminated edges reduces dramatically. The sufficient supply of precursor and low nucleation energy together boost the ultrafast growth of sub-millimeter MoS2 domains within seconds. This work provides an effective method for ultrafast growth of 2D semiconductors with high quality, which will promote their applications.

The co-precipitation evolution of NiAl and Cu nanoparticles and its influence on strengthening and toughening mechanisms in low-carbon ultra-high strength martensite seamless tube steel

The designed low-carbon ultra-high strength martensite seamless tube steel was manufactured by hot rolling and quenching-tempering processes. The multiple strengthening mechanisms are evaluated depending on the microstructure and co-precipitation evolution mechanism of Cu and NiAl, and the toughening mechanisms associated with multiscale microstructures are systematically discussed. The results show that the microstructure of the experimental steel in the quenched state consists of 87.8% lath martensite (LM) and 12.2% granular bainite (GB), while the microstructure in the QT state includes tempered martensite (TM), GB and a small amount of reversed austenite. The TEM morphology of QT steel shows three types of nanoparticles co-precipitated by Cu-rich, NiAl and Cu-NiAl, and the nanoparticles coarsen significantly and the number density decreases dramatically as the aging temperature increases from 500 °C to 650 °C. The co-precipitation evolution mechanism of nanoparticles elucidates that high density of small-sized BCCCu and B2-NiAl particles is optimal for strengthening increment. The experimental steel has an maximum yield strength of 1332.5 MPa aged at 500 °C, which is attributed to high precipitation strengthening of 651.2 MPa (general superposition of shear strengthening and Orowan strengthening) and dislocation strengthening of 454.8 MPa. The experimental steel has obvious low-temperature toughening, and the impact energy at -40 °C increases from 5 J to 237 J as the aging temperature increases from 500 °C to 650 °C. The excellent low-temperature toughness is attributed to the reduction of dislocation density, the weakening of the shear mechanism and the transformation of a small amount of reversed austenite to increase the crack nucleation energy, and the increase of the number fraction of HAGB and the significant plastic deformation increase the crack propagation energy.

The heterointerface of graphene in-situ growth for enhanced microwave attenuation properties in La-doped SiBCN ceramics

The electromagnetic wave (EMW) absorbing materials are widely applied to attenuate the useless and harmful EMW generated from wireless communication and 5G networks, which could protect the human health and electronic device safety. In this study, La-doped SiBCN ceramics with broadband EMW absorption capability were prepared via generating abundance of heterointerfaces, as graphene were in-situ grown by La2O3 catalyzing. The graphene in-situ formed in the ceramics can be attributed to the La atom decreasing the potential energy of the free carbon ring nucleation from −760.9 Ha to −8984.3 Ha. Consequently, the electrical conductivity of the SiBCN ceramics improved from 12.360 S/m to 18.025 S/m, the minimum reflection loss (RLmin) obtained was −26.48 dB at 7.2 GHz and the effective absorption bandwidth (EAB) was 6.32 GHz (11.68–18.00 GHz) at a thickness of 1.7 mm. At 700 °C, the RLmin and EAB values reached −43.18 dB and 4.2 GHz, respectively. The enhanced EMW absorbing capability can be attributed to the rationally tailor the heterointerfaces to improve the polarization loss and conduction loss of the SiBCN ceramics. The interfaces between graphene and amorphous phases generate built-in electric fields and space chare regions to strengthen the interface polarization, while the electrons migrating rapidly in the graphene and other crystals improved the electrical conductivity. The positive effect of heterointerfaces regulation of graphene in-situ growth improved the dielectric loss capacity of the SiBCN ceramics; therefore, this study provides a feasible method to enhance the EMW absorption capability of polymer-derived ceramics.

Ionic accelerator based on metal–semiconductor contact for fast electrode kinetics and durable Zn-metal anode

The development of Zn metal anodes with high reversibility and fast kinetics is critical for achieving high-performance aqueous Zn-metal batteries. Herein, we report a Zn@SiC electrode with an Ohmic contact that exhibits excellent durability and enhanced electrode process kinetics. The Ohmic contact barrier (Φb) inhibited electron transfer from the metal to the SiC passivation layer and effectively regulated Zn deposition under the passivation layer, thus suppressing dendrite growth. The built-in potential (Vbi) accelerated the Zn transfer and reaction kinetics and decreased the nucleation energy, thereby enhancing the charge–discharge platform potential (∼40 mV) in full cells. Coupled with the good anti-side reaction ability of the SiC layer, the Zn@SiC electrode successfully delivered a highly reversible stripping/plating process after 3770 h under a 1.0 mA cm−2 current density with a low overpotential of 33.7 mV. Furthermore, by analyzing the energy band structure of the Ohmic contacts, the critical current density was quantitatively determined. This clarified the relationship between the deposition position and the current density, thus providing a standard for practical semiconductor design.

Triacylglyceride melting point determination using coarse-grained molecular dynamics.

This study is carried out using the COGITO force field to determine whether the thermodynamic melting point of pure triacylglyceride crystals can be predicted using molecular dynamics simulations. The triacylglycerides used in this study are both saturated and unsaturated, as well as symmetrical and asymmetrical, to test the robustness of both the force field and the direct heating methodology described in this paper. Given the nonequilibrium nature of a melting system, a larger number of simulations are required to ensure that the results are sufficiently converged, that is, with little fluctuation and a small confidence interval. The study also highlights the importance of the presence of defects, in this case as voids, to lower the melting nucleation energy barrier of the crystals and avoid superheating of the systems being tested. The size of these defects is much larger than what would be found in a physical crystal, however, the simple and robust procedure that was developed allows the accurate prediction of melting points of the different triacylglycerides.

Stochastic Monte Carlo Model for Simulating the Dynamic Liquid-Liquid Phase Separation in Bacterial Cells.

There is growing evidence showing that many critical biological processes are driven by biomolecule condensates through liquid-liquid phase separation (LLPS). Although the qualitative observation and description of LLPS have been well documented, quantitative simulations of the time-dependent progression of LLPS in live cells are generally lacking. In this work, we build a stochastic Monte Carlo model to simulate the dynamic LLPS process during the formation of bacterial aggresomes. We demonstrate that the size distribution of the protein condensates evolves from an exponential-like to a bimodal-like pattern, and the number of condensates increases at the beginning and then decreases after reaching a maximum. Incorporating diffusion and collision, our simplified model recapitulates the two-step LLPS process in which many smaller condensates are formed in the first step and then merged into a few larger ones. We further reveal that the condensation speed, which can be defined by the condensates formed in unit time during the first step, is mainly determined by both the collision energy barrier and the initial protein density, while the number of condensates at the equilibrium is mainly associated with the dissociation energy barrier. Moreover, the LLPS process is not sensitive to temperature changes ranging around physiological conditions. Additionally, we consider the effect of the nucleation energy barrier on LLPS. We find that a higher nucleation energy barrier brings a slower condensation speed. Overall, we simulate the spatiotemporal dynamics of the LLPS process and provide qualitative guidance for understanding the dynamics of LLPS in bacterial cells, which can faithfully recapitulate experimental observations and facilitate the design of future experimental tests.

Structure-Controlled Carbon Hosts for Dendrite-Free Aqueous Zinc Batteries.

The surging demand for environmental-friendly and safe electrochemical energy storage systems has driven the development of aqueous zinc (Zn)-ion batteries (ZIBs). However, metallic Zn anodes suffer from severe dendrite growth and large volume change, resulting in a limited lifetime for aqueous ZIB applications. Here, it is shown that 3D mesoporous carbon (MC) with controlled carbon and defect configurations can function as a highly reversible and dendrite-free Zn host, enabling the stable operation of aqueous ZIBs. The MC host has a structure-controlled architecture that contains optimal sp2 -carbon and defect sites, which results in an improved initial nucleation energy barrier and promotes uniform Zn deposition. As a consequence, the MC host shows outstanding Zn plating/stripping performance over 1000 cycles at 2mAcm-2 and over 250 cycles at 6mAcm-2 in asymmetric cells. Density functional theory calculations further reveal the role of the defective sp2 -carbon surface in Zn adsorption energy. Moreover, a full cell based on Zn@MC900 anode and V2 O5 cathode exhibits remarkable rate performance and cycling stability over 3500 cycles. These results establish a structure-mechanism-performance relationship of the carbon host as a highly reversible Zn anode for the reliable operation of ZIBs.

Sandpaper grinding stable interface for reversible and durable zinc metal anode

Zinc-ion batteries (ZIBs) are promising energy storage system owing to the low cost and high safety features. As the most-used anode material, zinc metal always encounters poor coulombic efficiency (CE) and cycling stability, because of the serious zinc dendrite and harmful side reactions on Zn surface. Here, a solid-phase non-adhesive homogeneous Nano-Si layer has been embedded on the Zn surface (Zn-Si) via an ultra-facile grinding method. The Nano-Si layer can regulate an even electric field distribution to achieve a homogeneous zinc deposition, and it also can greatly lower the charge transfer resistance and nucleation energy barrier of Zn2+ to facilitate the zinc deposition, thus achieving a dendrites-free and long-life Zn anode. Encouragingly, the zinc symmetrical battery with Zn-Si anode delivers a superior CE of 99.6 % in 1000 cycles under 5 mA cm−2, and a stable cycle lifespan of 3600 h under 1 mA cm−2 with much lower polarization potential (42 mV), outperforming the symmetrical battery with pure Zn anode (455 h, 59 mV) and various previously reported strategies. Additionally, the effectiveness of Nano-Si layer is further proved in the Zn-Si/MnO2 battery, which presents a greatly improved capacity retention and cycling performance.

Microstructure changes in Sn-Bi solder joints reinforced with Zn@Sn particles in thermal cycling and thermomigration

BackgroundIn the field of electronic packaging, Sn-58Bi solder paste is a promising low-temperature option for step soldering. However, the tendency for the Bi-rich phase to coarsen and segregate poses a significant challenge to the long-term reliability of the solder joints. MethodsThe Sn coated Zn (Zn@Sn) core-shell particles were prepared through a chemical plating process and incorporated into the Sn-58Bi low-temperature solder paste to enhance its reliability. The microstructural and mechanical characteristics of the solder joints were evaluated under thermal cycling and thermomigration conditions to assess their long-term service reliability. Significant findingsThe addition of Zn lowers the nucleation energy and promotes the refinement of the eutectic structure, avoiding a significant reduction in shear strength after thermal cycling. In thermomigration, the heat transfer Q* of Bi is calculated to be 22.5 kJ/mol. The Zn-rich phases hardly move and are evenly distributed within the solder joints, acting like a barrier to prevent the Bi phase diffusing from the hot end to the cold end.

Novel agricultural waste based hardening accelerator for early strength development of fly ash-based concrete

Rapid urbanization is leading to a rise in demand for precast elements to reduce the time and cost of construction. However, precast elements consume the time to remove formwork during production depends on the early strength development of fresh concrete. On the other hand, thermal power plants produce a significant amount of fly ash, which also cause environmental issues. One solution to this problem is to use fly ash in cement and concrete to enhance their pozzolanic properties and address environmental concerns. However, using fly ash can delay the early strength development of concrete resulting deacceleration in the production cycle of precast elements. To speed up the process, some may opt for chemical-based hardening accelerator and high temperature curing. However, this may negatively impact the hydration kinetics of the concrete, pose environmental risks, and compromise the reinforced concrete’s durability.To overcome such limitations, impurity free C-S-H seed based hardening accelerator was synthesized from agricultural waste product namely, bagasse ash using novel chemical synthesis process which could effectively accelerates the early strength development of concrete without altering the conventional hydration process. The proposed synthesis process provides a platform for the reaction between the target calcium and silicate ions simultaneously eliminating the harmful elements (like chloride etc.) responsible for degradation of health of reinforced concrete structure.In order to study the effectiveness of a synthesized C-S-H seed, a blended ordinary Portland cement (OPC) was prepared by replacing 10%, 15%, and 20% of the cement weight with fly ash. Various amounts of the C-S-H seed were then added to the blend. Presence of developed C-S-H seed effectively reduced the setting time and eliminated the induction period during hydration of fly ash blended cement. Presence of additional seeds effectively reduces the critical free energy of nucleation which in turn accelerates the precipitation of hydration product responsible for the early strength development of fly ash-based concrete. Based on the setting time and heat of hydration analysis, it has been observed that the presence of C-S-H seed has the potential to accelerate the early strength gain process of fly ash-based concrete.

In Situ Reaction Fabrication of a Mixed‐Ion/Electron‐Conducting Skeleton Toward Stable Lithium Metal Anodes

Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density. However, the uncontrollable lithium dendrites and volume change of lithium metal anodes severely hinder its application. In this work, the porous Cu skeleton modified with Cu6Sn5 layer is prepared via dealloying brass foil following a facile electroless process. The porous Cu skeleton with large specific surface area and high electronic conductivity effectively reduces the local current density. The Cu6Sn5 can react with lithium during the discharge process to form lithiophilic Li7Sn2 in situ to promote Li‐ions transport and reduce the nucleation energy barrier of lithium to guide the uniform lithium deposition. Therefore, more than 300 cycles at 1 mA cm−2 are achieved in the half‐cell with an average Coulombic efficiency of 97.5%. The symmetric cell shows a superior cycle life of more than 1000 h at 1 mA cm−2 with a small average hysteresis voltage of 16 mV. When coupled with LiFePO4 cathode, the full cell also maintains excellent cycling and rate performance.

Controlling the formation energy of perovskite phase via surface polarity of substrate for efficient pure-blue light-emitting diodes

Quasi-two-dimensional (quasi-2D) perovskites are composed of self-organized multiple-quantum-well structures. Imbalanced crystallization during the solution-processed deposition results in the formation of different 2D phases, which are affected by the surface polarity of substrates. Herein, we investigate the influence of the surface polarity of the underlying hole injection layer (HIL) on the crystallization dynamics of each 2D phase and the luminescence properties of resulting quasi-2D perovskite films. Incorporating L-dopa involving hydroxyl groups into the HIL gives the substrate a higher surface polarity, allowing the decrease in the critical free energy of nucleation. This HIL ensures the formation of dense nuclei involving a small-sized nucleus, which enables the quasi-2D perovskite film to entail a lower-n-dominated phase distribution. The modulated phase distribution eventually induces a hypsochromically shifted luminescence spectrum. Furthermore, by controlling the ratio of L-phenylalanine and L-dopa, efficient perovskite light-emitting diodes (PeLEDs) having well-matched electronic structure and pure-blue perovskite emitter are realized with a maximum external quantum efficiency of 5.57% at 472 nm. This work provides a facile approach to achieving efficient pure-blue PeLEDs.

Structure–energy relationship of food materials using differential scanning calorimetry

AbstractThe use of differential scanning calorimetry (DSC) in the food authentication and process‐chain traceability has raised significant amelioration in terms of structure and stability of some structured foods. In this review article DSC is used to raise other quantitative energy parameters related to structural reconformation and variation in the intra‐molecular dimension of studied materials. These properties are explained by the respective energy models involving (1) quantum energy, (2) quantum mass, and (3) quantum velocity. These models parameters are explored as well as on from enthalpy, entropy, heat capacity, and Gibbs free energy of transition in determining the nucleation energy relevant to crystallization and polymorphic transformation of some studied food‐materials.Practical ApplicationDifferential scanning calorimetry is remaining the powerful thermoanalytical tool used in studying the mechanism of crystallization, polymorphism, and structural reconformation of biological matters. The expression of energetic parameters on from enthalpy, entropy, heat capacity, and Gibbs free energy of transition help in determining the nucleation energy whether is stable or in the meta‐static forms. In addition these energy parameters are the key elements in understanding whether the food materials undergoing denaturation, unfolding or reversible folding, meaning that DSC is able in determining the status of food materials whether is stable or instable as well as the texture whether is soft, grainy, or coarse and also the polymorphic forms of the crystals and stability of the emulsions. Thus, gathering information on the thermal analysis using DSC helped in establishing some model correlation between energy and structure in association with the chemical composition changes of some model of oils and fats.

Unraveling the ferroelectric switching mechanisms in ferroelectric pure and La doped HfO2 epitaxial thin films

Epitaxial orthorhombic phase La doped HfO2 films are promising for achieving robust ferroelectric polarization without wake-up effect. However, lowering the coercive field is crucial for achieving low-power memory devices.In this work, we have investigated the influence of the La content effect on the structural and ferroelectric properties of epitaxial HfO2 thin films. We show that while the remanent polarization is optimum for 2–5 at. % La-doped HfO2 films, the coercive field is decreased with La doping. The experimental work is supported by density functional theory (DFT) calculations which show that the polarization switching in epitaxial La:HfO2 films can be understood based on the synergetic contribution of the presence of a non-ferroelectric monoclinic phase and the La doping itself that causes a reduction of the nucleation and DW motion energy barriers for the crossing path, which makes it more probable than the non-crossing one.

Transformation kinetics for low temperature post-deposition crystallization of TiO 2 thin films prepared via atomic layer deposition (ALD) from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water

Background: We report on the fundamental crystallization kinetics of atomic layer deposited (ALD) TiO2 thin films undergoing a post-deposition anneal (PDA) at low temperatures to probe differences in the as-deposited film microstructure. Methods: The system of study is ALD TiO2 thin films prepared from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water at 120 °C, 140 °C and 160 °C followed by ex situ low temperature annealing at temperatures ranging from 140 °C to 220 °C. All as-deposited TiO2 thin films are amorphous by X-ray diffraction (XRD). Post-deposition annealing (PDA) produces large grain anatase crystals, confirmed by XRD and top-view scanning electron microscopy (SEM). A detailed SEM study is performed to quantify the nucleation and growth kinetics by fitting microstructural data to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a time-temperature-transformation (TTT) diagram is constructed to summarize the differences in crystallization behavior at different ALD deposition temperatures. Results and conclusions: Fitting microstructural data to the JMAK equation reveals an Avrami exponent close to 3 with continuous nucleation, suggesting two-dimensional, plate-like crystal growth. Applying an Arrhenius relationship to the phase transformation data, the combined activation energy for nucleation and growth is found to be 1.40–1.58 eV atom-1. Nucleation rates are determined, and an Arrhenius relationship is used to calculate the critical Gibbs free energy for nucleation (~1.3–1.4 eV atom-1). As such, nucleation is the rate-limiting step for the amorphous to anatase phase transformation. ALD growth temperature is found to dictate film microstructure with lower deposition temperatures reducing the nucleation rate and leading to larger grain sizes irrespective of PDA conditions. The nucleation rate pre-exponential frequency factor increases with increasing deposition temperature, thereby increasing the likelihood for nucleation. Interestingly, it is this difference in the vibrational modes of the amorphous structure, as indicated by the variation in the nucleation rate pre-exponential frequency factor, that alters the phase transformation rates and not a change in the activation energies for the transformation.

Large reversible magnetocaloric effect across the first-order magneto-structural transition in (Mn0.45Fe0.55) (Ni0.6Co0.4) Si alloy

Magnetic materials with reversible magnetocaloric effect across their respective first-order magneto-structural transitions (MST) have vital significance for further advancement towards the ultimate goal of practical magnetic cooling applications. In this present study, the reversibility of the MST is investigated by analyzing the isofield curves under different minor and major thermal hysteresis loops and the isothermal curves under different magnetic field cycles. The reversibility of the magnetocaloric effect (MCE) depends upon the width of the nucleation energy barrier existing across the MST. Minor hysteresis loops are found to be minimizing the energy loss by preventing the nucleation of the martensite phase and can be easily returned to the austenite phase immediately while switching from cooling to heating. A large reversible isothermal magnetic entropy change ΔSM of −14.4 J kg−1 K−1 nearly at 322 K is observed for the (Mn0.45Fe0.55) (Ni0.6 Co0.4) Si alloy under a low magnetic field change of 3 T. The observed large reversible MCE, very low magnetic field-induced hysteresis loss, and large reversible RCeffe ∼ 155 J kg−1 will be beneficial for reducing the energy loss during several magnetic field cycles in practical cooling applications which makes this alloy promising for the development of efficient magnetic refrigerants.

Synthesis and characterization of nano-polycrystal diamonds on refractory high entropy alloys by chemical vapour deposition

Growing diamond has been a long-standing challenge. It is found the diamond grows on refractory metals (such as Zr, Hf, Ti) hardly to form a continuous film with a high nucleation density because of diffusion of carbon. In this study, we reported an approach to grow diamond on high entropy alloys (HEAs) of TiZrHfTaMo, TiZrHfNbMo, TiHfNbTaMo as substrates by chemical vapour deposition. Diamond films with a nucleation density as much as 108 ∼ 1010 site/cm2 grow on the mixed-carbides XC (X = Hf, Zr and Ta etc.) layer, which is 2 ∼ 3 orders of constituent metals. The orientation relationship is identified as diamond[011] // XC[001] with XC mixed-carbides by high resolution transmission electron microscope. The continuous diamond films can be obtained within 30 min. The high nucleation density and rapid growth on HEAs refer to solubility of carbon and relative nucleation energy barrier. Moreover, the corrosion of current specimens in 3.5 wt% NaCl solution have been improved (e.g., corrosion potential value is as much as −0.02 V/SCE) because of the continuous diamond film. Current result facilitates promising industrial applications of HEAs and diamonds by combining the advantages of them.