Typical Layered Structure Research Articles

Optical temperature sensing properties of novel RE3+ (RE=Er, Ho) doped BaLa2Ti3O10 phosphors

A novel luminescent material of BaLa2Ti3O10:RE3+ was synthesized by the high-temperature solid phase method, with a typical layered structure belonging to a special crystal system. Under the excitation of 980 nm, BaLa2Ti3O10:4%Er3+ exhibits characteristic emissions centered at 531 nm, 551 nm and 668 nm. It is noteworthy that the color of BaLa2Ti3O10:3%Ho3+ shows a strong green emission at 551 nm and a weak red emission near 664 nm, also represents adjustable yellow-green light with the change of 980nm laser pumped powers. The optical temperature sensing properties were checked by employing different strategies, relating to the thermally-coupled-levels (TCLs) and nonthermally-coupled-levels (NTCLs). The results show that the maximum relative sensitivity of TCLs based on BaLa2Ti3O10:Er3+ is 0.68% K-1(305 K). Similarly, the maximum sensitivity of TCLs is 0.89% K-1(313 K) in BaLa2Ti3O10:Ho3+, which performs well from 313 K to 513 K. It has been found the samples using FIRs of TCLs can produce higher absolute (Sa) and relative (Sr) sensitivities compared with those using Fluorescence Intensity Ratios (FIRs) of NTCLs. The multiple FIRs also achieved superior levels of temperature resolution and repeatability in all cases. Generally, this work provides favorable candidates for the temperature sensors.

The microstructure and mechanical properties of the laser-welded joints of as-hot rolled AlCoCrFeNi2.1 high entropy alloy

AlCoCrFeNi2.1 hot-rolled eutectic high entropy alloys were welded by laser welding, yielding a free-defect laser-welded connection. With the use of optical microscopy, EDS, EBSD, and XRD, the microstructure of the base metal (BM), fusion zone (FZ), and heat-affected zone (HAZ) of the joint was examined. The produced joint underwent tensile and micro-hardness testing as well as a fracture morphology examination. A similar tensile strength in the FZ and BM is measured, while a decrease in the elongation. The typical layered lamellar structures, in particular an FCC + BCC dual-phase structure, were all visible in the HAZ, BM, and FZ zones. The α-fiber and γ-fiber as well as other textures are determined by the ODF figure, indicating a potential orientation distribution of the as-hot rolled AlCoCrFeNi2.1 joint. A clear grain refinement characteristics in the fusion zone as a result of the uneven thermal cycling during the welding process. The results of the mechanical test demonstrate the base metal has the highest hardness value, i.e. 500–550 HV0.2, within the welded joint zone. The welded joint has a tensile strength ∼1200 MPa, which is marginally higher than ∼1150 MPa in the base metal, and an elongation that decreases by 20 % from base metal to welded joint, indicating a decrease in the plasticity of the welded joint. A combination of brittle and ductile fracture occurs in welded joints during tensile failure. This study may give possibilities for the engineering application of laser welding of AlCoCrFeNi2.1 eutectic high entropy alloy in the future.

Understanding the impact of Li2CO3 distribution within solid electrolyte interphases on lithium metal via thermal conditioning

The formation of a solid electrolyte interphase (SEI) is crucial for the performance and safety of Li metal batteries (LMBs). The SEI consists of various compounds that are assumed to prevent electrolyte decomposition and dendrite growth. Among these constituents, Li2CO3 has a contentious position; some studies stated that it is a beneficial component, whereas others viewed it as an impurity. This study investigated the influence of strategic heat treatments on the distribution of Li2CO3 formed in the SEI of Li metal. These treatments affect the cycling performance of Li/LiCoO2 cells, as evidenced by the differences in cycle life and capacity. In particular, the study showed that samples heat-treated at higher temperatures generally exhibited enhanced performances, illustrating the impact of heat treatment on SEI quality. The quality of the SEI, which depends on the Li2CO3 formation model (solid electrolyte interface layer or a solid polymer electrolyte layer), varies depending on the applied heat treatment. The samples heat-treated at 120 °C followed the solid polymer electrolyte layer model, resulting in the mosaic-style formation of Li2CO3. This intricate pattern provides superior mechanical stability compared with that of a plain layer-type structure and can be used to develop potential strategies for the enhancement of the cycling stability and overall longevity of LMBs.

Investigation of scale formation and degeneration of silicide coating on Nb–Si based alloy in the temperature range from 1250 °C to 1560 °C

Nb silicide coatings modified with active elements have good oxidation resistance, but there is a lack of systematic research on their oxidation behavior at high temperatures above 1250 °C. The aim of this work is to investigate the oxidation behavior of an Al–Y modified silicide coating on Nb–Si based alloy in the temperature range from 1250 °C to 1560 °C. After oxidation at 1250 °C, the scale displays a typical layered structure consisting mainly of a TiO2 outer layer, an amorphous SiO2 matrix layer embedded with TiO2 and ZrSiO4, and an inner layer consisting of SiO2 and Cr2O3. Above 1350 °C, the evaporation reaction of Cr2O3 into CrO3 (g) is significantly accelerated and Cr2O3 disappeared gradually with temperature or time. The TiO2 layers covering on the scales formed at 1250–1500 °C grow along the crystallographic orientation of [100]. The micropores formed on the surface of TiO2 should be attributed to the further oxidation of Cr2O3 into volatile oxide CrO3 (g). The scales exhibit a similar structure consisting mainly of a SiO2 glass matrix embedded with ZrSiO4 and a surface TiO2 layer until 1500 °C. Above the eutectic temperature of SiO2–TiO2 system, the scale is mainly composed of a matrix layer of SiO2–TiO2 eutectic embedded with block TiO2 particles, and a thin SiO2 interface layer at 1560 °C. The degeneration path of the (Nb,X)Si2 coating is (Nb,X)Si2 → (Ti,Nb)5Si4 → γ-(Nb,X)5Si3.

Investigation on the pullout bearing properties and stress characteristics of fully grouted bolts in layered rock mass

AbstractCoal‐measure strata is a typical layered structure, a better understanding of the bearing characteristics of fully grouted bolts in layered rock mass is of great significance for roadway support. However, limited studies have been conducted to investigate the bearing performance of fully grouted bolts in layered rock mass. In this paper, a numerical model of fully grouted bolt in layered rock mass was established, and a tri‐linear bond–slip model of the anchorage interface was imported into the numerical model by the user‐defined Fish language. The effects of strata sequence, strata thickness, and strata number in layered rock mass on the bearing performance of fully grouted bolts were systematically analyzed. The results show that fully grouted bolts in soft–hard type (SH‐type) layered rock mass has higher bearing capacity. The greater the thickness of the soft rock in the layered rock mass, the more significant the influence of the strata sequence on the bearing performance of fully grouted bolts. The bearing capacity of fully grouted bolts decreases with the increase of the thickness ratio of soft rock to hard rock. The greater the thickness of the hard rock in the layered rock mass, the more beneficial to the bearing performance of fully grouted bolts. With the increase of the strata number, the bearing capacity of fully grouted bolts gradually decreases. For bolt support of layered rock mass, the deep anchoring foundation of fully grouted bolts should be arranged in hard rock or elastic zone rock as much as possible, and rock grouting can be adopted to reduce the difference in mechanical properties between layered rock mass and improve the durability of fully grouted bolts. The research results may provide useful guidance and reference for the support design of fully grouted bolts.

Printable MXene Ink Hybridized with ZSM-5 for Gas Sensing and CO2 Capturing

MXene has garnered significant attention as a two-dimensional material with exceptional physicochemical properties for gas sensing development. This study utilized ZSM-5 nanoparticles loaded with MXene to prepare printable inks, aiming to explore novel applications of MXene in the gas sensing field. The morphology of MXene/ZSM-5 was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), demonstrating the typical layered structure of MXene and particle morphology of composite ZSM-5. X-ray photoelectron spectroscopy (XPS) confirmed no production of TiO2 by providing valence information on elements. Thermogravimetric analysis (TG) revealed excellent thermal stability. To verify functional gas sensing feasibility, various hydrocarbons and common gases underwent adsorption and desorption tests (BET). Results showed that MXene loaded with ZSM-5 exhibited good adsorbability for C4H10, C7H8, SF6, H2O and O2 while having a certain trapping effect on CO2. Through testing and analyzing printing results, it was found that the MXene/ZSM-5 ink overcame dispersion issues present in pure MXene ink.

Cellulose nanofiber-connected covalent organic framework nanosheets composite membrane for proton conduction

Covalent organic framework (COF) nanosheets have been considered as promising materials for proton exchange membranes (PEM) due to their orderly, adjustable pores and relatively improved membrane forming properties. Here, we introduced the one-dimensional sulfonated bacterial cellulose nanofibers (SBCNF), originating from coconut and binding TpBd-2SO3H nanosheets to prepare a series of SBCNF/TpBd-2SO3H composite membranes. The composite membranes present a typical layered structure due to the presence of SBCNF. Moreover, extensive hydrogen bond network is formed between the embedded TpBd-2SO3H nanosheets and SBCNF, which is beneficial for improving the proton conductivity and mechanical strength of the membrane. As a result, the composite membrane achieved a proton conductivity of 147.5 mS/cm at 80 °C, 100 %RH and a highest tensile strength of 88.49 MPa.

High stability and selectivity of butterfly pea flower extract-NiAl LDH-based catalysts in the tetracycline degradation.

Layered double hydroxide (LDH) is an applicable material that can be modified in various ways. Modifications using natural extracts fulfill the principles of "green chemistry." The preparation of butterfly pea flower extract (BPE)-modified NiAl LDH was completed using the calcination and restacking method. The characteristics of the prepared composites were identified through analysis of functional groups, crystal phase, bandgap energy, surface area and surface morphology. Fourier transform-infrared (FT-IR) characterization revealed that the active group of the catalyst is -OH except for NiAl layered double oxide (LDO), which has the metal oxide-like functional groups. X-ray diffraction patterns expressed a typical layered material structure of NiAl LDH dan NiAl LDH-BPE, but not for NiAl LDO and NiAl LDO-BPE. Introducing BPE into NiAl LDH and NiAl LDO effectively decreased the bandgap energy and changed the surface morphology. The prepared catalysts were applied in a batch system with pH 5 to degrade tetracycline (TC). NiAl LDO demonstrated the highest activity as a catalyst in TC degradation, with a 93.61% degradation rate. In contrast, NiAl LDO-BPE demonstrated the highest structural stability in TC degradation and repeated use, with an initial degradation percentage of 82.58% and a fifth regeneration percentage of 71.4%.

Simultaneous removal of arsenic and cadmium in aqueous solution by a novel hydrotalcite-like absorbent FeMnCa-LDHs

As(III) and Cd(II) pose a significant threat to the ecological environment and human health due to their high toxicity and carcinogenicity, the simultaneous removal of hazardous anions and cations in wastewater has always been a challenging problem. This study employed the co-precipitation method to synthesize FeMnCa-LDHs, a novel ternary metal material devoid of toxic metals, enabling simultaneous removal of As(III) and Cd(II) from aqueous solutions. The XRD patterns and SEM-EDS images showed that the prepared FeMnCa-LDHs exhibited characteristic peaks and a typical layered structure of hydrotalcite-like compounds with high crystallinity. In the composite adsorption system, FeMnCa-LDHs showed synergistic sorption of As(III) and Cd(II) in water, and their adsorption kinetics conformed to the quasi-secondary kinetic model, with adsorption rates of 0.31 and 0.136 g·(mg·h)−1, respectively, and the isothermal adsorption curves conformed to the Langmuir model, with the maximum adsorption amounts of 216.08 and 193.18 mg·g−1 (pH = 5.0, 25 °C), respectively, higher than those of the other LDHs. In the pH range of 3–6, FeMnCa-LDHs exhibited excellent adsorption performance on As(III) and Cd(II), and the adsorption capacity can reach 89.0 and 82.9 mg·g−1, respectively. The coexistence of both PO43− and CO32– ions in water had a competitive effect on the adsorption of As(III) but had little effect on Cd(II) adsorption. The main adsorption mechanism between Cd(II) and FeMnCa-LDHs was found to be isomorphic substitution and surface precipitation, as revealed by XRD, XPS, and FT-IR analyses. On the other hand, the adsorption mechanism that bonded As(III) involved oxidation, ion exchange, surface complexation, and surface precipitation. Furthermore, it maintains a specific adsorption capacity even after undergoing five adsorption cycles. This study demonstrates the potential of FeMnCa-LDHs in treating wastewater that contains As(III) and Cd(II).

Development of Molybdenum trioxide (MoO3) by spin coating method for photovoltaic application

Molybdenum trioxide, MoO3 , thin films have been deposited on glass substrates by Spin-coating method using ammonium heptamolybdate tetrahydrate ((NH4 )6Mo7O244H2O ) as a single source precursor of Mo and O and. They were subjected to atmospheric heat treatment at different temperatures (200°C, 400°C and 500°C). MoO3 thin films obtained, were characterized using X-ray diffraction techniques (XRD), Scanning Electron Microscopy (SEM), Energy Dispersed Spectroscopy (EDS) and integrating sphere. The XRD patterns of annealed films show the formation of ΜοΟ3 in a polycrystalline phase, formation of MoO3 was also confirmed by EDS. The SEM photographs show that the thin films obtained are in layer-type structure and their grains size increases with increasing of annealing temperatures. The measurement results of integrating sphere show that the MoO3 thin film prepared at 500°C transmit about 72% and reflect about 12% of the visible spectrum.

The Phosphidosilicates AE2 Li4 SiP4 (AE=Ca, Sr, Eu) Ba4 Li16 Si3 P12.

The quaternary phosphidosilicates AE2 Li4 SiP4 (AE=Ca, Sr, Eu) and Ba4 Li16 Si3 P12 were synthesized by heating the elements and Li3 P under argon atmosphere. Their crystal structures were determined by single crystal X-ray diffraction. AE2 Li4 SiP4 crystallize in a new layered structure type (P21 /m, Z=2) with CdI2 -analoguos layers. Edge sharing CaP6 octahedra are separated by layers of vertex-sharing SiP4 and LiP4 tetrahedra, which contain additional chains of LiP6 octahedra. Ba4 Li16 Si3 P12 forms likewise a new structure type (P21 /c, Z=16) with a three-dimensional network of SiP4 , Si2 P6 and LiP4 entities as well as one phosphorus site not bonded to silicon. Barium is located in capped trigonal prisms of phosphorus which form strongly corrugated layers. 31 P and 29 Si solid-state NMR spectra confirm the crystal structures of the compounds AE2 Li4 SiP4 . 7 Li spectra show only one signal in spite of quite different crystallographic positions, which indicate possible Li+ mobility. However, this signal is much broader compared to the known Li+ conducting phosphidosilicates. Accordingly, electrochemical impedance measurements show low Li+ conductivities.

Surface-Modified LDH Nanosheets with High Dispersibility in Oil for Friction and Wear Reduction.

Surface and interfacial engineering of nanomaterials is essential for improving dispersion stability in liquids. In this study, we report that oleic acid (OA)- and stearic acid (SA)-functionalized layered double hydroxide (LDH) nanosheets as lubricant additives can achieve high dispersion and reduce friction and wear. LDH is a typical layered structure, and OA and SA are long-chain organic molecules that are not only compatible with base oils but also act as friction-reducing agents. The OA and SA molecules were branched onto ZnMgAl LDH nanosheets using dehydration condensation between the exposed OH groups on the surface of LDH and the COOH groups on the OA and SA molecules. Compared with that of the pristine ZnMgAl LDH, the dispersion of OA-ZnMgAl LDH and SA-ZnMgAl LDH was significantly improved. The surface-modified LDH exhibited superior tribological properties and great stability due to the synergistic lubrication effect between OA, SA, and LDH. Even at an ultralow concentration (0.15 wt %), the coefficient of friction and wear volume were reduced by ∼65 and ∼99%, respectively, compared to those of the base oil. Due to the green and simple synthesis method and excellent tribological properties, surface-functionalized LDH has enormous possibilities for future industrial applications.

Synthesis, Crystal structure, electronic structure, and Raman spectra of Li4Sr2SiP4

AbstractRecently, ternary lithium phosphides have been studied intensively owing to their high lithium ion conductivities. During investigations aiming for derivatives with less lithium content the new compound Li4Sr2SiP4 was obtained. It crystallizes in the monoclinic space group P21/m (N°11) with lattice parameters of a=7.2919(8) Å, b=8.3679(6) Å, c=6.9965(8) Å, and β=90.061(9)°. The crystal structure contains isolated [SiP4]8− tetrahedra that are charge balanced by two Sr2+ and four Li+ counter ions. The structure can be derived as a superstructure of the layered CaAl2Si2 structure type comprising a hexagonal closest packing of P atoms and tetrahedral voids filled with Si and Li atoms, whereas octahedral voids are filled with Sr and Li atoms. DFT calculations confirm the structure with ordered atom positions as a global minimum and predict an indirect band gap of 2.23 eV. In addition, the experimental Raman spectrum is in good agreement with the calculated one.

Comparative analysis of ground thermal conductivity and thermal resistance of borehole heat exchanger in different geological layered sequence

Borehole heat exchanger usually passes through many geological layers of the different thermo-physical properties from one layer to another in practical project of ground-coupled heat pump system. Considering the effect of heterogeneity in geological structures on heat transfer of borehole heat exchanger, it is necessary for in-situ thermal response test analysis to investigate the effect of geological layered sequence on ground thermal conductivity and borehole thermal resistance. Firstly, based on the validated numerical layered borehole heat exchanger model and numerical homogenous borehole heat exchanger model, the simulated distributions of water temperatures in U-pipe and heat flux along the depth in thermal response test are respectively compared and analysed. Then, the effective thermal conductivity and effective borehole thermal resistance estimated by the infinite line source model are respectively obtained based on the simulated thermal response tests carried out in the borehole heat exchanger installed in the six types of geological layered structures. The borehole thermal resistances in the two numerical model were respectively calculated by integrating the local thermal resistance along the depth. Finally, the ground thermal conductivities and borehole thermal resistances are compared in six types of geological layered structures. The results show that the maximum relative error of 7 % between the effective thermal conductivity and the thickness-weighted thermal conductivity in the numerical layered borehole heat exchanger model is located in the sequence of S-L-C due to BOTTOM 60m-thickness clay with lowest thermal conductivity. The relative error between effective borehole thermal resistance and borehole thermal resistance in the numerical layered borehole heat exchanger model are 3.5 %∼7.9 % in the six types of layered geological structures, and the maximum relative error between the two borehole thermal resistances corresponding to the two numerical models is only 1.1 %, which proves that effect of geological layered sequence on the deviation is limited in the two numerical models.

Ambient melting behavior of stoichiometric uranium oxides

As UO2 is easily oxidized during the nuclear fuel cycle it is important to have a detailed understanding of the structures and properties of the oxidation products. Experimental work over the years has revealed many stable uranium oxides including UO2, U4O9 (UO2.25), U3O7 (UO2.33), U2O5 (UO2.5), U3O8 (UO2.67), and UO3, all with a number of different polymorphs. These oxides are broadly split into two categories, fluorite-based structures with stoichiometries in the range of UO2 to UO2.5 and less dense layered-type structures with stoichiometries in the range of UO2.5 to UO3. While UO2 is well characterized, both experimentally and computationally, there is a paucity of data concerning higher stoichiometry oxides in the literature. In this work we determine the ambient melting points of all the six stoichiometric uranium oxides listed above and compare them to the available experimental and/or theoretical data. We demonstrate that a family of the six ambient melting points map out a solid-liquid transition boundary consistent with the high-temperature portion of the phase diagram of uranium-oxygen system suggested by Babelot et al.

Monitoring of Energy Storage Mechanism of Zn/Meso-MnO2 Battery System Using X-Ray Absorption Fine Structure

As energy storage systems, LIBs, which are most frequently used, have excellent capacity, power, and long lifespan performance [1]. However, as the reserves of the raw minerals used—lithium and cobalt—are exhausted, prices are escalating. A further issue with LIB is that it heats up to a high temperature during charging, which leads to a string of fire or explosion catastrophes. To solve these safety or cost challenges, various next-generation batteries are being developed, and we are exploring about aqueous zinc ion battery (AZIB), which attracting attention as the next-generation battery due to outstanding safety and cost competitive advantage. Generally, zinc metal acting as an anode, has a high theoretical capacity of 820mAh/g as it is gives two electrons (2e-). Also, because of its sparse reactivity with water and ability to employ water-based electrolytes with strong ion conductivity and low ignition risk, it is particularly advantageous in terms of safety. There have been a variety of cathode materials utilized, such as manganese oxide, vanadium oxide, Prussian blue analogues (PBAs), polyanion compounds, and Chevrel phase compounds [2-4]. Especially, manganese dioxide (MnO2) has been addressed by prior studies that Zn2+ can be inserted into crystal structure because it exhibits several crystal structures (α, β, γ, δ, and λ) with tunnel-type or layer-type structure. Mn4+ ions occupying octahedral holes formed by hexagonal close-packed (hcp) oxide ions compose the fundamental unit of the crystal structure of MnO2 polymorphs. To construct a [MnO6] octahedral unit, each Mn4+ ion is precisely surrounded by six oxygen neighbors, and these units are connected by the edges and/or corners [5]. Understanding the energy storage mechanisms is essential for the one-step evolution of cathode materials for AZIB. However, these polymorphs significantly affect the electrochemical reaction, thus involving complex reaction mechanisms [5-7]. Additionally, it is extremely challenging to research the mechanisms of AZIB since protons (H+) are known to participate in the reaction by acting as charge transfer as well as Zn2+ ions. Therefore, while several efforts are being conducted to unveil the exact reaction mechanism, a mesoporous nanostructured material with a large specific surface area is adopted, which can more precisely grasp the electrochemical reaction studies of electrode/electrolyte surface [8,9]. X-ray absorption fine structure (XAFS) is a powerful technique used for the analysis of nanostructured materials, widely used in the field of battery research [10]. It involves the measurement of the absorption of X-ray by the material, which can provide information about oxidation state, chemical bonding of the materials and the local geometry structure during charge/discharge process. This analysis method gives great insight into the complex energy storage pathway of MnO2 materials with various polymorphs. Based on this knowledge, we synthesized ordered mesoporous β-MnO2 through nano-casting method by using KIT-6 as hard-template and used it as the cathode active material. As depicted in Figure 1, we performed ex-situ XAFS analysis at the states of charge during 2nd cycle to monitor energy storage mechanisms. The oxidation state changes could be quantitatively estimated by edge energy analysis by comparing the reference MnO2 and Mn2O3 samples. It was also possible to unveil further about the reaction mechanism at each voltage by examining the structural change in the local geometry of [MnO6] unit through a careful analysis of pre-edge region and EXAFS spectra. During discharge process, insertion mechanism, which causes relatively larger distortion in the local geometry compared to conversion mechanism, results in a increment of pre-edge intensity, which opposes the decline in pre-edge intensity due to the reduction of the oxidation state. This fact demonstrates that although H+ conversion could not have a significant effect on pre-edge intensity in the early discharge stage, Zn2+ insertion was the phenomenon responsible for the rise in pre-edge intensity during late discharge stage. In addition, through EXAFS spectra analysis, the irreversible change in corner sharing Mn-Mn bond distance during charge/discharge process could be seen that an irreversible phase transition of MnO2 occurred due to Zn2+ insertion, indicating clue to identify the cause of capacity fading. These findings contribute to further understanding of the reaction mechanisms and capacity fading phenomenon and suggest practical strategies for next-generation zinc-ion batteries.

Electrocatalytic Activities of Sr2BO3Cl (B = Mn, Fe, Co, Ni) for Oxygen Reactions in Alkaline Solutions

The practical application of zinc-air rechargeable batteries, which are expected to be the next-generation rechargeable batteries, is challenged by the kinetically very slow oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Therefore, an air electrode catalyst with high activity for OER and ORR is required, and perovskite oxides have attracted attention as a candidate. To improve the catalytic activity of perovskite oxides, optimization of metal cations has been studied. On the other hand, anion substitution has also been reported to improve activity, and the oxychloride Sr2CoO3Cl with the Ruddlesden-Popper (RP) structure (composition: An+1BnO3n+1), which is a type of layered perovskite structure showed superior catalytic activities. However, there are still few studies on oxychlorides and the effect of anion substitution on the catalytic activity is still unknown. In this study, we compared the air electrode catalytic activity of RP-type acid chlorides Sr2 BO3Cl (B = Mn, Fe, Co, Ni) and LaSrBO4, an oxide with the same structure and valence, and investigated the B-site element dependence of the chloride ion substitution effect.The ORR activity measurement results show that the oxychlorides with Co and Mn at the B site exhibited lower ORR overpotentials than the oxides, and that the ORR reaction electron number calculated from the Koutecký-Levich plots increases. Comparing the results for the same B-site elements, the oxychlorides had higher OER activity for all B-site elements. This suggests that chloride ion substitution may be effective in improving OER activity for all B-site elements, not only Co.

Phase Transition Behavior in Antiferroelectric Copper Formate Tetrahydrate Crystal

Antiferroelectric properties of copper formate tetrahydrate (CFT) crystal having phase transition temperature at were investigated theoretically. CFT have a layer-type structure in which layers of are sandwiched between the layers of copper formate in the lattice plane. By considering modified two sublattice pseudospin lattice coupled mode model Hamiltonian and double-time temperature-dependent Green function method for antiferroelectric copper formate tetrahydrate (CFT) crystal, the phase transition properties of crystal have been studied. Expressions are derived for soft mode frequency, dielectric constant and loss tangent for considered crystal. Model values are fitted in the derived expressions and the dependence of the above properties on temperature have been calculated. Theoretically obtained results are compared with experimental data and show similarities between them. Dielectric constant as a function of temperature shows a behaviour of the first-order transition with a large discontinuity at the transition point. These properties can be employed in a wide range of applications including memory devices, solar cells, biosensors and photovoltaic devices.

Effect of Y2O3 content on the microstructure and wear performance of plasma-sprayed Cr2O3–Y2O3 composite coatings

As the inner working surface of a diesel engine, the cylinder liner is subjected to a harsh frictional wear environment, which can lead to performance degradation and ultimately affect the engine's service life. Ceramic coatings can improve the wear resistance of the cylinder liner, thereby enhancing the reliability and stability of the diesel engine. In this study, Cr2O3–Y2O3 ceramic composite coatings were deposited on the substrate of 304 stainless steel by atmospheric plasma spraying (APS). The influence of Y2O3 content on the microstructure, porosity, phase composition, microhardness and wear performance of the composite coating was investigated. The results showed that the composite coatings exhibited a typical layered structure, and Y2O3 and Cr2O3 were dispersed relatively evenly. When the Y2O3 content was 10 %, the coating had the lowest porosity rate of 5.41 % and the highest hardness of 1094.6 HV1. As the Y2O3 content increased, the coating exhibited an increase in porosity and a decrease in hardness. Under dry friction conditions, the friction coefficient curve underwent a rapid increase phase, followed by stabilizing within the range of 0.29–0.40. When the Y2O3 content is 10 %, the coating exhibits the best wear resistance, including the lowest coefficient of friction, wear rate, and scratch depth. However, the composite exhibits the worst wear resistance when the Y2O3 content reaches 50 %. The wear mechanism was altered by the addition of Y2O3. At lower Y2O3 content, the predominant wear mechanism was abrasive wear resulting from particle refinement. Conversely, at higher content, adhesive wear caused by wear transfer from the milling balls became more prominent.

Hierarchically Multiscale Vertically Oriented NiFeCo Nanoflakes for Efficient Electrochemical Oxygen Evolution at High Current Densities

AbstractCrucial advancements in versatile catalyst systems capable of achieving high current densities under industrial conditions, bridging the gap between fundamental understanding and practical applications, are pivotal to propel the hydrogen economy forward. In this study, vertically oriented hierarchically multiscale nanoflakes of NiFeCo electrocatalysts are presented, developed by surface modification of a porous substrate with nano‐structured nickel. The resulting electrodes achieve remarkably low overpotentials of 139 mV at 10 mAcm−2 and 248 mV at 500 mAcm−2. Further, scaled‐up electrodes are implemented in a water‐splitting electrolyser device exhibiting a stable voltage of 1.82 V to deliver a constant current density of 500 mA cm−2 for over 17 days. Moreover, the role of the unique structures on electrochemical activity is systematically investigated by fractal analysis, involving computation of structure factors such as Minkowski connectivity, fractal dimension, and porosity using scanning electron microscope images. It is found that such structures offer higher surface area than typical layered double hydroxide structures due to morphological coherence that results in a superhydrophilic surface, while the base Ni layer boosts the charge transfer. This study demonstrates a Ni/NiFeCo(OH)x heterostructure with highly porous morphology, a key to unlocking extremely efficient oxygen evolution reaction activity with exceptional stability. Moreover, fractal analysis is presented as a valuable tool to evaluate the electrochemical performance of catalysts for their structured morphology.