Crystalline Phase Research Articles

Enhancing Cyclability of Fe2O3-V2O5-P2O5 Ceramic Cathode for High-Performance Sodium-ion Batteries through Heat Treatment

Due to the ability to form more open structures, glass and glass-ceramic materials can accommodate larger Na+ ions and enable rapid solid-state diffusion of Na+ at room temperature (RT). Regardless of the larger ionic radius of Na, iron-based mixed-vanadium-phosphate ceramics show promising potential as cathode materials in sodium-ion batteries (SIBs). However, their practical applicability is significantly hindered by slow Na+ diffusion and low intrinsic electrical conductivity. In the present study, a ceramic sample with the composition of 5Na2O−45Fe2O3−10V2O5−40P2O5, denoted as (5NFVP), was synthesized before (BHT) and after heat treatment (HT) at 500, 600, and 700 °C for 2h to be used as a cathode material in SIBs. The outstanding electrochemical performance of the 5NFVP ceramic is attributed to improved electronic and ionic conductivity and enhanced structural stability during Na+ insertion/de-insertion. This is supported by various analyses, including X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), 57Fe Mössbauer spectroscopy, and electrochemical impedance spectroscopy (EIS). All prepared samples show two doublets, with the first doublet associated with Fe3+(Td), confirming the XRD results that indicate the main crystalline phase of FePO4. The second doublet observed in the 5NFVP-HT500 and 600°C is related to Fe3+(Oh), while 5NFVP-BHT exhibits a large δ value of 1.19 mm s−1, indicating the presence of Fe2+(Oh) due to NaFePO4 crystalline phase. The Fe-K absorption edge analysis reveals that 5NFVP-HT600°C ceramics predominantly consist of Fe3+, whereas 5NFVP-BHT has the most abundant Fe2+ compared with HT samples. The largest DC conductivity is achieved by the 5NFVP-HT600°C ceramic, reaching 5.08×10−9S cm−1 at RT. The initial capacity of 5NFVP-HT ceramics is approximately doubled compared to 5NFVP-BHT. The 5NFVP-HT600°C ceramic as a cathode demonstrates excellent long-cycling stability, retaining 60 % of its capacity over 100 cycles under a current rate of 50 mA g−1. These findings underscore the significant potential of 5NFVP-HT600°C for advanced energy storage systems, given its affordability and robust cyclability.

The Biological Properties of Co-Doped Monetite Are Influenced by Thermal Treatment.

Calcium phosphates, notably monetite, are valued biomaterials for bone applications owing to their osteogenic properties and rapid uptake by bone cells. This study investigates the enhancement of these properties through Cobalt doping, which is known to induce hypoxia and promote bone cell differentiation. Heat treatments at 700°C, 900°C, and 1050°C are applied to both monetite and Cobalt-doped monetite, facilitating the development of purer, more crystalline phases with varied particle sizes and optimized cellular responses. Comprehensive physicochemical characterization through XRD, FTIR, Raman, SEM/EDS, and ASAP analyses shows significant phase transformations into pyrophosphate, influencing the materials' structural and functional attributes. When utilized to condition a culture medium for MC3T3-E1 cells, these materials demonstrate non-cytotoxic behavior and provoke specific gene responses associated with the osteoblastic phenotype, angiogenesis, adhesion, and extracellular matrix remodeling. Significantly, non-heat-treated Cobalt-doped Monetite retains properties advantageous for clinical applications such as dental and orthopedic implants, where lower processing temperatures are crucial. This attribute, combined with the material's straightforward production, highlights its practicality and potential cost-effectiveness. Further research is essential to assess the long-term safety and efficacy of these materials in clinical settings. Our findings underscore the promising role of Cobalt-doped Monetite in advancing bone repair and regeneration, setting the stage for future innovations in treating bone lesions, enhancing implant integration, and developing advanced prosthetic coatings within the field of tissue engineering.

Synthesis of spherical and rods-like titanium oxide nanoparticles (TiO2 NPs) and evaluation of their cytotoxicity towards colon cells in vitro.

Titanium oxide nanoparticles (TiO2 NPs) are currently used as ingredients in medicines and sunscreens. Unfortunately, recent information about TiO2 NPs indicates their undesirable biological effect on colon cells. Therefore, the aim of this work was to synthesize and evaluate the physicochemical characterization of spherical (TiO2 NSs) and rods-like (TiO2 NRs) NPs, followed by assessment their cytotoxicity. For this purpose, both normal colon epithelial cells (CRL-1790) and cancerous colon cells (SW480) were used. Scanning transmission electron microscopy (STEM) showed that TiO2 NSs with a diameter of ≈10nm and TiO2 NRs with the size of the longer axis ≈25nm and shorter axis ≈3nm were obtained. Based on the selected area electron diffraction (SAED) patterns, it was found that crystalline phases were obtained for both TiO2 NPs. The UV-Vis spectra showed no contamination of TiO2 NPs. Zeta potential values were 9.7mV and 3.1mV for NSs and NRs, respectively. Cytotoxicity of TiO2 NPs was assessed using the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxy-methoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium) test for various concentration of NPs. The cytotoxic effect for both TiO2 NPs was visible for concentration of 75μg/ml (for CRL-1790) and 50μg/ml (for SW480) and higher, and it did not depend on the shape. Moreover, both types of TiO2 NPs (in higher concentration) induce the generation of reactive oxygen species (ROS) in cells cultured with these NPs. Holotomographic microscopy studies showed increased cellular uptake of TiO2 NPs by SW480. The obtained results for the synthesized TiO2 NPs are a promising prospect for their use in biomedical application.

H2 production from the photocatalytic reforming of ethylene glycol: Effect of TiO2 crystalline phase on photo-oxidation mechanism

In this work, the mechanism of H2 production from ethylene glycol as a model compound for photoreforming over platinized TiO2 is presented with particular focus on the effect of the TiO2 polymorph. It was found that Pt/anatase and Pt/anatase:rutile (P25) had similar H2 production activities and both catalysts followed an indirect oxidation pathway where ethylene glycol was oxidised via hydroxyl radicals to glycolaldehyde. In contrast, Pt/rutile primarily oxidised ethylene glycol directly into formaldehyde. The formaldehyde was unable to react further, which significantly reduced the formation of hydrogen despite similar conversion of ethylene glycol compared with the other supports used. We propose that these differences are due to different adsorption behaviour and hole transfer mechanism on the different TiO2 crystalline phases. In particular, ethylene glycol complexation on Ti5c sites on the dominant (110) facet of rutile leads to a direct hole transfer and an oxidative C–C cleavage mechanism prevailing.

Studying novel high-pressure phases in laser-shock-affected silicon using poly: an algorithm for spot-wise phase identification

Fast quenching dynamics in confined laser-induced microexplosions have been shown to lead to localized shockwaves that can create nanometre-scale domains in novel high-pressure crystalline phases. In the case of silicon, new silicon polymorphs such as bt8-Si and st12-Si have been recently observed, which are predicted to have bandgaps desirable for photovoltaic applications. Identification of these phases has been previously achieved by analysis of selected-area electron diffraction (SAED) patterns taken from laser-shock-affected areas. However, this analysis was complicated by pattern overlap from the many crystallites in the selected area, and many spots were found to agree with multiple potential phases. To overcome this ambiguity and enable the identification of the phase of Bragg spots observed in SAED patterns from polymorphic nanomaterials, we developed a new algorithm that we termed poly. This method is based on maximizing the magnitude and angular correlation between observed diffraction spots and those values derived from a known potential phase. We present the performance of this algorithm on simulated electron diffraction patterns as well as experimental SAED patterns measured from laser-shock-affected silicon samples. We find that the most abundant phases in the affected areas are t32-Si and t32*-Si and report on their relaxation into other high-pressure silicon phases over the course of 90 days after the laser-induced confined microexplosion.

New Insights into Interfacial Dynamics and Mechanisms of Biochar–Derived Dissolved Organic Matter on Arsenic Redistribution in Schwertmannite

Biochar is extensively utilized for the remediation of environments contaminated with heavy metals (HMs). However, its derived-dissolved organic matter (BDOM) can interact with iron oxides, which may adversely influence the retention of HMs. This study investigates the effect of BDOM derived from tobacco stalk (TS) and tobacco petiole (TP) biochar on the redistribution behavior of As(V) in acid mine drainage (AMD)–impacted environments, particularly concentrating on the interactions with Schwertmannite (Sch). Results showed that TP–BDOM, abundant in lignin–like compounds, led to a low–amplitude release of As(V) from Sch under acidic conditions, reaching a maximum value (19.84 μg L–1), significantly lower than the release caused by TS–BDOM (87.46 μg L–1). Subsequently, 88.2% of the released As(V) were re–adsorbed in the TS–BDOM system, while 47.5% were retained in the TP–BDOM system. XRD analysis, in conjunction with SEM and STEM characterizations, confirmed that there were no additional crystalline phases or alterations in the microscopic morphological features of the particles throughout the reaction process. In–situ ATR–FTIR, complemented by 2D–COS analysis, demonstrated that aromatic N–OH groups and carboxylic in BDOMs coordinated to As–Sch, enhancing sulfate and As(V) release. It was also noted that no As(III) was detected under the influences of TP– and TS–BDOM. XPS results indicated that As(V) remained the predominant redox species even in the presence of BDOMs. These findings enhance our insight into BDOM’s role in As(V) fate and transport within AMD-contaminated environments.

Influence of Alkyl Chain Length and Bromine Substitution on Thermal, Photophysical, and Optical Properties of Biphenyl Luminescent Molecules

This study investigates a series of bromine-substituted alkoxy biphenyl derivatives to explore their potential as luminescent and optical materials for applications in display technologies, sensors, and photonic devices. Four compounds were synthesized, including 5-Br, 6-Br, 7-Br, and a comparative non-halogenated molecule 6-H. The findings reveal that the bromine-substituted derivatives exhibit enhanced thermal stability as the alkoxy chain length increases, though none of the compounds displayed liquid crystalline phases, likely due to molecular flexibility and steric hindrance from the bromine atoms. Photophysical studies showed that the compounds exhibit tunable emission colors ranging from green to blue, depending on the side chain length and the presence or absence of bromine. Importantly, the introduction of bromine was found to enhance the photophysical properties, including increased quantum yields and longer emission lifetimes, compared to the non-halogenated analog. Moreover, these luminescent molecules can maintain strong fluorescence both in solution and when forming aggregates. Furthermore, the optical properties, such as dielectric constant, extinction coefficient, refractive index, and optical conductivity, were thoroughly examined. The results indicate that structural variations, including alkyl chain length and bromine substitution, significantly influence the capability of these materials to store and dissipate electrical energy. Their strong optical responses, high energy storage capabilities, and sensitivity to structural modifications suggest that the studied materials have substantial potential for applications in energy storage, sensing, optoelectronics, and non-linear optics. These findings offer important guidelines for the rational design of multifunctional luminescent and optical materials, representing a significant step forward in the development of practical applications of smart materials and advanced photonic devices.

Cadmium-rich intermetallic phases ARh2Cd20 - structure, magnetic behavior, 151Eu Mössbauer and 113Cd solid-state NMR spectroscopy.

The cadmium-rich intermetallic compounds ARh2Cd20 (A = Ca, Sr, Y, La-Nd, Sm-Lu) were synthesized from the elements in sealed tantalum tubes. The elements were reacted in an induction furnace and the samples were post-annealed to increase phase purity and crystallinity. The ARh2Cd20 phases crystallize with the cubic CeCr2Al20 type structure, space group Fd3̄m. The polycrystalline samples were characterized by X-ray powder diffraction. The structures of SrRh2Cd20, LaRh2Cd20, CeRh2Cd20, TbRh2Cd20 and DyRh2Cd20 were refined from X-ray single crystal diffractometer data. Temperature dependent magnetic susceptibility data show diamagnetism for CaRh2Cd20, SrRh2Cd20, YRh2Cd20, LaRh2Cd20 and YbRh2Cd20, thus substantiating stable divalent ytterbium in the latter phase. The remaining phases are Curie Weiss paramagnets. EuRh2Cd20 contains stable divalent europium and orders ferromagnetically at TC = 13.8 K. Antiferromagnetic ordering was detected for SmRh2Cd20 (TN = 4.3 K), GdRh2Cd20 (TN = 9.3K), TbRh2Cd20 (TN = 6.6 K) and DyRh2Cd20 (TN = 3.9 K). TbRh2Cd20 and DyRh2Cd20 exhibit metamagnetic transitions at critical fields of 19 respectively 10 kOe. The divalent ground state in EuRh2Cd20 was also confirmed by a 151Eu Mössbauer spectrum which shows an isomer shift of δ = -10.86(1) mm s-1. Solid-state NMR spectroscopy was performed for the samples YRh2Cd20, LaRh2Cd20, and YbRh2Cd20. The 113Cd NMR spectra include three distinct Cd sites for each sample in accordance with the crystallographic data. All samples further show negative Knight shifts for 103Rh, suggesting high s-d exchange interaction at the Rh site. In the case of 139La, a residual quadrupolar coupling was observed despite cubic site symmetry, confirming the existence of local defect sites. 89Y and 171Yb NMR spectra were recorded, the latter confirming the divalent nature of Yb in YbRh2Cd20.

Nanoclay-Mediated Crystal-Phase Engineering in Biofunctions to Balance Antibacteriality and Cytotoxicity.

The crystalline phase of metal oxides is a key determinant of the properties and functions of the nanomaterials. Traditional approaches have focused on replicating bulk-phase structures, with limited exploration of phase diversity due to challenges in controlling the crystal morphology. Here, we introduce a nanoclay-mediated strategy for crystal-phase engineering, using talc to modulate the morphology and phase of manganese oxide (MnOx) nanoparticles. This approach enhances the oxidase activity of the MnOx composite (M/T), optimizing the antimicrobial efficacy while minimizing cytotoxicity. M/T-190 demonstrated 99% bactericidal activity against Escherichia coli and Staphylococcus aureus, coupled with 84% cytocompatibility. Theory calculations suggest that talc modulates the charge distribution and d-band center tuning at the Mn3O4/MnOOH interface, enhancing oxygen activation. When integrated into gauze, M/T exhibits strong antimicrobial activity, low toxicity, and promotes wound healing in both in vitro and in vivo studies. These findings highlight the potential of natural minerals for crystal-phase engineering in biomedical applications.

Activating Reversible V4+/V5+ Redox Couple in NASICON-Type Phosphate Cathodes by High Entropy Substitution for Sodium-Ion Batteries.

Vanadium-based Na superionic conductor (NASICON) type materials (NaxVM(PO4)3, M = transition metals) have attracted extensive attention when used as sodium-ion batteries (SIBs) cathodes due to their stable structures and large Na+ diffusion channels. However, the materials have poor electrical conductivity and mediocre energy density, which hinder their practical applications. Activating the V4+/V5+ redox couple (V4+/V5+≈4.1 V vs Na+/Na) is an effective way to elevate the energy density of SIBs, whereas the irreversible phase transition of V4+/V5+ and severe structural distortion will inevitably result in fast capacity fading and unsatisfactory rate capability. Herein, a high entropy regulation strategy is proposed to optimize the detailed crystal structure and improve the reversibility of crystalline phase transformation and electrical conductivity of the material. With the activated reversible V4+/V5+ redox couple, stable structure, and fast electrochemical kinetics, the high entropy material Na3.2V1.5Fe0.1Al0.1Cr0.1Mn0.1Cu0.1(PO4)3 (NVMP-HE) exhibits an outstanding electrochemical performance with highly reversible specific capacity of 120.1 mAh g-1 at 0.1 C and excellent cycling stability (92.4% retention after 1000 cycles at 20 C). Besides, the in situ X-ray diffraction (XRD) measurement reveals that a smooth three-phase transition reaction is involved in this high-entropy cathode and the existence of mesophase facilitates a fast phase transition.

Impact of charge distribution on the stability of ferroelectric nematic liquid crystals.

This study explores the influence of charge distribution and molecular shape on the stability of ferroelectric nematic liquid crystalline phases through atomistic simulations of DIO molecules. We demonstrate the role of dipole-dipole interactions and molecular shape in achieving polar ordering by simulating charged and chargeless topologies, and analysing positional and orientational pair-distribution functions. The charged DIO molecules exhibit head-to-tail and side-by-side parallel alignments conducive to long-range polar order, whereas the chargeless molecules show no polar ordering. The 2D x-y cross-section of the correlation pair-distribution function shows that lateral local dipoles in the molecular structure are critical for the formation of the ferroelectric phase, highlighting the importance of charge asymmetry and electrostatic interactions in stabilizing long-range polar order.

Microstructure modulation and mechanical properties of multicomponent Fe50Cr14Mo14C9B8Tm5 bulk metallic glass through controlled crystallization processing

Fe50Cr14Mo14C9B8Tm5 bulk metallic glass was prepared at a cooling rate of 6.36 × 104 K s−1. Its Young's modulus and compressive strength were modulated through controlled crystallization processing. A low cooling rate induced the formation of the Tm2Mo2C3 phase while preserving free volume. Thus, the elastic deformation limit was increased to 2.39%. After low-temperature annealing, the (Fe, Cr)23(C, B)6 phase was formed at first. As the annealing temperature increased, four types of crystalline phases appeared as dispersions in this alloy, where the hardness of the Fe3Mo3C phase reached 32.5 GPa. Even when the annealing temperature reached 1260 K, the average grain size was only 180 nm. The large volume fraction of the Fe3Mo3C phase and uniform microstructure of crystallized alloy resulted in a high strength of 4.01 GPa and a low Young's modulus of 237.11 GPa.

Preparation and corrosion resistance to cathode materials for lithium‐ion batteries of CA6 foam ceramics

AbstractCA6 foam ceramics (CA6‐FCs) with CA6 as the main crystalline phase were prepared by adding CA6 powder through gel casting process, which reduced the severe shrinkage in the reaction synthesis process of CA6. This simple preparation process can realize the industrial production of CA6‐FCs. The linear change and physical properties of CA6‐FCs can be controlled by adjusting the additional amount of CA6 powder and the solid content of the slurry. The corrosion resistance of CA6‐FCs is better than that of the current mainstream mullite thermal insulation materials in lithium‐ion battery cathode materials. Through the simple process of this study, on the basis of industrial production, CA6‐FCs can replace mullite lightweight thermal insulation materials to improve the alkali corrosion resistance, service life, and maintain production safety of kiln lining.

Crystalline-symmetry-protected Majorana modes in coupled quantum dots

We propose a minimalist architecture for achieving various crystalline-symmetry-protected Majorana modes in an array of coupled quantum dots. Our framework is motivated by the recent experimental demonstrations of two-site and three-site artificial Kitaev chains in a similar setup. We find that introducing a π-phase domain wall in the Kitaev chain leads to a pair of mirror-protected Majorana zero modes located at or near the junction. Joining two π junctions into a closed loop, we can simulate two distinct classes of two-dimensional higher-order topological superconducting phases, both carrying symmetry-protected Majorana modes around the sample corners. As an extension of the π junction, we further consider a general vertex structure where n Kitaev chains meet, i.e., a Kitaev n vertex. We prove that such an n vertex, if respecting a dihedral symmetry group Dn, necessarily carries n vertex-bound Majorana modes protected by the Dn symmetry. Resilience of the junction and vertex Majorana bound states against disorder and correlation effects is also discussed. Our architecture paves the way for designing, constructing, and exploring a wide variety of artificial topological crystalline phases in quantum-dot experiments. Published by the American Physical Society 2025

Reversibly Alterable Hot-Electron Photodetection Without Altering Working Wavelengths Through Phase-Change Material Sb2S3

Generally, the responsivities of hot-electron photodetectors (HE PDs) are mainly dependent on the device working wavelengths. Therefore, a common approach to altering device responsivities is to change the working wavelengths. Another strategy for manipulating electrical performances of HE PDs is to harness electric bias that can be used to regulate hot-electron harvesting at specified working wavelengths. However, the reliance on bias hampers the flexibility in device operations. In this study, we propose a purely planar design of HE PDs that contains the phase-change material Sb2S3, realizing reversibly alterable hot-electron photodetection without altering the working wavelengths. Optical simulations show that the designed device exhibits strong absorptance (>0.95) at the identical resonance wavelengths due to the excitations of Tamm plasmons (TPs), regardless of Sb2S3 phases. Detailed electrical calculations demonstrate that, by inducing Sb2S3 transitions between crystalline and amorphous phases back and forth, the device responsivities at TP wavelengths can be reversibly altered between 59.9 nA/mW to 128.7 nA/mW. Moreover, when device structural parameters are variable and biases are involved, the reversibly alterable hot-electron photodetection at specified TP wavelengths is maintained.

High-Performance Mechano-Sensitive Piezoelectric Nanogenerator from Post-Treated Nylon-11,11 Textiles for Energy Harvesting and Human Motion Monitoring.

Piezoelectric polymer textiles offer distinct advantages in the fabrication of wearable nanogenerators (NGs). One effective strategy to enhance the output capacity of NGs is to modulate the piezoelectric performance of the textiles. This paper focuses on further improving the piezoelectric properties of nylon-11,11 textiles through post-drawing and annealing treatments. We elucidate the evolution of morphology and the ferroelectric phase in the submicron/nanoscale fibers during post processing as well as the corresponding changes in performance. The drawing process primarily enhances the orientation of the crystalline phase and reduces the fiber diameter, while the annealing process more effectively promotes the crystal size and crystallinity. Afterward, we propose an optimal postdrawing and annealing assisted-electrostatic spinning process. Under the synergistic effects of these post-treatments, the remanent polarization (Pr) of nylon-11,11 textile increased to 4.7 times that of the untreated textile, resulting in amplified piezoelectric outputs. The output voltage, current, and power density of the prepared PENG reached 21.5 V, 800 nA, and 1.88 mW·m-2 (80 MΩ), respectively. Notably, at pressures exceeding 8 kPa, the mechano-voltage and current sensitivity reached as high as 266 mV/kPa and 13.99 nA/kPa, respectively, which is extraordinary compared to other piezoelectric NGs and comparable to the performance of nylon-based triboelectric NGs. Furthermore, we investigated the potential application of the prepared PENG in biomechanical energy harvesting and human movement monitoring. Experiments demonstrated its effectiveness in powering light bulbs, tracking walking status, and monitoring finger/hand/wrist gestures.

Adaptability of Electrospun PVDF Nanofibers in Bone Tissue Engineering

This study focused on the development of a suitable synthetic polymer scaffold for bone tissue engineering applications within the biomedical field. The investigation centered on electrospun polyvinylidene fluoride (PVDF) nanofibers, examining their intrinsic properties and biocompatibility with the human osteosarcoma cell line Saos-2. The influence of oxygen, argon, or combined plasma treatment on the scaffold’s characteristics was explored. A comprehensive design strategy is outlined for the fabrication of a suitable PVDF scaffold, encompassing the optimization of electrospinning parameters with rotating collector and plasma etching conditions to facilitate a subsequent osteoblast cell culture. The proposed methodology involves the fabrication of the PVDF tissue scaffold, followed by a rigorous series of fundamental analyses encompassing the structural integrity, chemical composition, wettability, crystalline phase content, and cell adhesion properties.

Impact of artificial aging on the physical and mechanical properties of polycaprolactone under the combined effect of UV-radiation and elevated temperatures

ABSTRACT Annotation In this work the effect of long-term UV-radiation and temperature degradation on physical and mechanical properties of PCL was experimentally studied. Artificial aging of PCL at 30, 35 and 40°C and UV irradiation for 166, 360 and 554 h was carried out on a specially designed bench. Microstructure evaluation, spectroscopic studies and tensile tests were performed on aged specimens. On the surface of aged PCL there appear zones of irregular degradation with pronounced detachment of separate polymer fragments. Fragmentation occurs as a result of more intensive photodegradation and oxidative processes. According to the results of FTIR analysis, a strong effect on crystallinity is shown with two-factor exposure to PCL over time. At 30°C, with increasing UV degradation time, the crystallinity of PCL decreases by 7% in 504 hours. It was found that increasing the temperature during aging to 40°C leads to a more intense degradation of the crystalline phase of PCL and a decrease in crystallinity by 10% over the same period. Curves of changes in the mechanical properties of PCL versus aging time were obtained. The Young’s modulus is reduced by 20% from 326 to 252 MPa, the tensile strength is 2 times (from 16.1 to 8.5 MPa), and the relative elongation at break is 5 times compared to the initial PCL, from 528 to 103%. Based on physical observations of the properties of environmentally friendly biodegradable polymers, it is possible to provide controlled representations of their use for packaging and biomedical applications to replace petroleum-based plastics as a structural material.

Microstructure and Wear and Corrosion Resistance of CoCrFeMoNiSix (x = 0.25, 0.50, 0.75) HEACs Prepared by Plasma Cladding

CoCrFeMoNiSix (x = 0.25, 0.50, 0.75) HEACs were successfully prepared on Q235 steel substrates by the plasma cladding method. The phase structure, microstructure, element distribution, and wear and corrosion resistance of these coatings were investigated by XRD, OM, SEM, EDS, a friction and wear tester, and an electrochemical workstation. The results show that the CoCrFeMoNiSix (x = 0.25, 0.50, 0.75) coatings are composed of a major FCC phase and minor BCC phase. With an increase in Si content, the lattice constant and cell volume of both phases and the BCC phase content in these alloys gradually increase, while the enthalpy of mixing, Gibbs free energy, atomic radius difference, VEC, and phase density decrease. All the three alloys exhibit typical dendritic structures. With an increase in Si content, the enrichment of Mo and Si in the interdendrite region is significantly reduced. The friction coefficients of CoCrFeMoNiSix (x = 0.25, 0.50, 0.75) HEACs show a trend of first increasing, then decreasing, and gradually stabilizing with an increase in time, and are 0.604, 0.526, and 0.534, respectively. The wear resistance of the three alloys is mainly related to the changes in crystallinity and high-strength BCC phase content caused by different Si contents. The polarization curves of CoCrFeMoNiSix (x = 0.25, 0.50, 0.75) high-entropy alloy coatings show an obvious passivation zone, and the corrosion resistance is significantly better than that of Q235 steel substrate. The CoCrFeMoNiSi0.75 coating has the highest self-corrosion potential, smallest self-corrosion current, largest capacitive reactance arc radius, and best corrosion resistance in a 3.5% NaCl solution.

Defect Migration and Phase Transformations in Two-Dimensional Iron Chloride inside Bilayer Graphene.

The intercalation of metal chlorides, and particularly iron chlorides, into graphitic carbon structures has recently received lots of attention, as it can not only protect this two-dimensional (2D) magnetic system from the effects of the environment but also substantially alter the magnetic, electronic, and optical properties of both the intercalant and host material. At the same time, intercalation can result in the formation of structural defects or defects can appear under external stimuli, which can affect materials performance. These aspects have received so far little attention in dedicated experiments. In this study, we investigate the behavior of atomic-scale defects in iron chlorides intercalated into bilayer graphene by using scanning transmission electron microscopy and first-principles calculations. We observe transformations between the FeCl2 and FeCl3 phases and elucidate the role of defects in the transformations. Specifically, three types of defects are identified: Fe vacancies in FeCl2 domains and Fe adatoms and interstitials in FeCl3 domains, each exhibiting distinct dynamic behaviors. We also observed a crystalline phase with an unusual stoichiometry of Fe5Cl18 that has not been reported before. Our findings not only advance the understanding of intercalation mechanism of 2D materials but also highlight the profound impact of atomic-scale defects on their properties and potential technological applications.