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This study focuses on conducting an ab initio evolutionary investigation to search for stable polymorphs of iron diborocarbides with the formula FeB 2 C 2. We also examined other forms of C contents, including FeB 3 C and FeBC 3. Our findings reveal that the lowest energetic structure of FeB 2 C 2 is a semimetallic monoclinic phase with a space group (s.g.) of C2/m and a metastable metallic phase of FeB 2 C 2 is an orthorhombic structure with s.g. of Pmmm. In addition, structural and relative properties of FeB 3 C and FeBC 3 are performed and discussed to compare with FeB 2 C 2. All predicted structures are dynamically and elastically stable, verified without negative phonon frequency and Born criteria, respectively. We also analyzed the energetic stability through calculated cohesive and formation energies, which showed that C2/m- FeB 2 C 2 is stable at low pressure. Interestingly, the C2/m and Pmmm phases of FeB 2 C 2 are hard materials with Vickers hardness ( H v) of 22.40 and 27.52 GPa, respectively. Additionally, we examined the electron–phonon coupling of both FeB 2 C 2 phases. Unexpectedly, we found that the semimetallic C2/m- FeB 2 C 2 phase is a superconductor with a significant superconducting temperature ( T c) exceeding 6 K. These findings provide some novel results for the Fe–B–C system and pave the way for investigating other metal borocarbides and related ternary compounds. [ABSTRACT FROM AUTHOR]

Shape memory composites now have a wide range of applications in aerospace, medical devices, and smart structures. Seven graphene‐carbon oxide/glass fiber (GO‐CF/GF) hybrid reinforced shape memory composites were prepared using vacuum infiltration hot pressing system (VIHPS) and the shape memory properties of the materials were investigated in 100°C test. By comparing and analyzing the microstructure and shape memory properties of composites containing different volume fractions of GFs, the mechanism of the influence of different hybrid contents of GFs on the organizational properties and shape memory properties was investigated. The results show that when the reinforcement of the composites were all carbon fibers, the composites had the largest elasticity modulus, harder material and the fixation rate of 77.15%, the recovery rate of 95.17%, the porosity of 0.80% and the shape recovery force of 7.98 N. When the reinforcement of the composites were glass fibers, the composites had the smallest elasticity modulus, softer material and the fixation rate of 94.89%, the recovery rate of 77.21%, the porosity of 13.56% and the recovery force of 2.28 N. The results of this test can lay a foundation for subsequent research on fibers with different mixing ratios. Highlights: The GO‐CF/GF/EP prepared by VIHPS has excellent shape memory properties.Fiber hybrid ratio affects the composite's porosity and its properties.Fiber hybrid ratio affects the composite's shape fixation, recovery, and memory force.The shape fixation of G6 decreases the lowest with test cycles.Carbon fiber content changes the zero‐stress plane of GO‐CF/GF/EP. [ABSTRACT FROM AUTHOR]

The heavy transition metal borides, carbides, and nitrides are still difficult to synthesize, and certain compositions are not even possible to stabilize. With the help of existing materials databases, we assemble 240 materials of chemical formula M 2 X, that we intend to investigate via density-functional theory (DFT). Our calculations demonstrate the stability of several novel compounds, which are highly likely to be synthesized in experiment, widening the potential applications as structural ceramics. The X site plays the primary role in determining the structural stability, with boron leading to many more stable ceramics than carbon and nitrogen. The chemical bonding is found to arise from a mixture of covalent bonding (M-X) and weak metallic bonding (M-M), which ensures varied elastic properties. Among the newly predicted materials, Tc 2 B ,Os 2 B , and Os 2 C are shown to be ultra-incompressible. A low shear modulus makes these systems prone to plasticity, which leads to an interesting coexistence of hardness and ductility for novel Os 2 B and Os 2 C , as well as existing Mo 2 B and Mo 2 C. Chemically, replacing 4 d with 5 d elements is shown to enhance bulk and shear moduli, which could be used for hardness engineering by selective doping. This report lays the foundations for further experimental research on the mechanical merits of the late transition metal borides, carbides, and nitrides of chemical formula M 2 X. [ABSTRACT FROM AUTHOR]

SiC ceramics are typically hard and brittle materials. Serious surface/subsurface damage occurs during the grinding process due to the poor self-sharpening ability of monocrystalline diamond grits. Nevertheless, recent findings have demonstrated that porous diamond grits can achieve high-efficiency and low-damage machining. However, research on the removal mechanism of porous diamond grit while grinding SiC ceramic materials is still in the bottleneck stage. A discrete element simulation model of the porous diamond grit while grinding SiC ceramics was established to optimize the grinding parameters (e.g., grinding wheel speed, undeformed chip thickness) and pore parameters (e.g., cutting edge density) of the porous diamond grit. The influence of these above parameters on the removal and damage of SiC ceramics was explored from a microscopic perspective, comparing with monocrystalline diamond grit. The results show that porous diamond grits cause less damage to SiC ceramics and have better grinding performance than monocrystalline diamond grits. In addition, the optimal cutting edge density and undeformed chip thickness should be controlled at 1–3 and 1–2 um, respectively, and the grinding wheel speed should be greater than 80 m/s. The research results lay a scientific foundation for the efficient and low-damage grinding of hard and brittle materials represented by SiC ceramics, exhibiting theoretical significance and practical value. [ABSTRACT FROM AUTHOR]

Hydrogen energy is the clean energy with the most potential in the 21st century. The microchannel reactor for methanol steam reforming (MSR) is one of the effective ways to obtain hydrogen. Ceramic materials have the advantages of high temperature resistance, corrosion resistance, and high mechanical strength, and are ideal materials for preparing the catalyst support in microchannel reactors. However, the structure of ceramic materials is hard and brittle, and the feature size of microchannel is generally not more than 1 mm, which is difficult to process using traditional processing methods. Diamond wire saw processing technology is mainly used in the slicing of hard and brittle materials such as sapphire and silicon. In this paper, a microchannel with a periodic corrugated microstructure was fabricated on a ceramic plate using diamond wire sawing, and then as a catalyst support when used in a microreactor for MSR hydrogen production. The effects of wire speed and feed speed on the amplitude and period size of the periodic corrugated microstructure were studied using a single-factor experiment. The microchannel surface morphology was observed via SEM and a 3D confocal laser microscope under different processing parameters. The microchannel samples obtained under different processing parameters were supported by a multiple impregnation method. The loading strength of the catalyst was tested via a strong wind purge experiment. The experimental results show that the periodic corrugated microstructure can significantly enhance the load strength of the catalyst. The microchannel catalyst support with the periodic corrugated microstructure was put into the microreactor for a hydrogen production experiment, and a good hydrogen production effect was obtained. The experimental results have a positive guiding effect on promoting ceramic materials as the microchannel catalyst support for the development of hydrogen energy. [ABSTRACT FROM AUTHOR]

Medium carbon AISI 1045 steel is a hard to machine material attractive to the automotive and construction industries due to its high strength and excellent heat resistance. Finite element method (FEM) is used in this study to obtain the optimal parameters for turning AISI 1045 steel. The simulation data is obtained and analyzed using an L16 Taguchi orthogonal array (TOA). Three input parameters: cutting speed (A), depth of cut (B), and feed rate (C), and three responses: cutting forces (Cf), maximum interfacial temperature (Tmax), and maximum principal stresses (σmax) are considered and analyzed using analysis of variance (ANOVA). The optimal conditions obtained are 60 m min−1 for A, 0.3 mm for B, and 0.4 mm rev−1 for C. The depth of cut and feed rate contribute the largest to the Cf (80.98%) and Tmax (38.56%), respectively. All the parameters contribute approximately equal toward the σmax. Comparison between the FEM values and literature experimental data shows that FEM can be used to predict optimal turning parameters with differences of ≈5%. This study gives a reference prediction model for the optimal machining parameters of medium carbon AISI 1045 steel and other related materials, which can be used, alongside experiments, to reduce the overall machining costs. [ABSTRACT FROM AUTHOR]

This research focuses on enhancing the wear resistance of EN8 steel, commonly used in agricultural implements by applying WC-12Co and WC-10Co-4Cr coatings using the high-velocity oxy-fuel (HVOF) spraying technique. The microstructural characterization, EDS mapping, microhardness, fracture toughness, slurry abrasion, and dry sliding of all coated and uncoated samples were evaluated. Results demonstrate that coated specimens outperform the uncoated EN8 steel in terms of wear resistance. Slurry abrasion tests reveal that the coatings hardness and fracture toughness contribute to their excellent performance. In dry sliding tests, the coated specimens exhibit lower friction coefficients and less mass loss, further emphasizing their better wear resistance. Further, wear mechanisms were found to be different between the materials, with EN8 steel exhibiting ductile wear, primarily due to plastic deformation and chipping, while the coated specimens display brittle wear characteristics, with the detachment of hard coating material and abrasive interactions contributing to wear. [ABSTRACT FROM AUTHOR]

The electrochemical discharge machining (ECDM) is an advanced and promising technology for fabricating micro structures. This method is effectively applicable for non-conductive hard and brittle materials micromachining, such as glass and ceramics. However, the ceramics high melting point and intense heat exchange effects during microchannel fabrication lead to the easy dissipation of thermal energy and the difficulty in processing. To address this issue and expanded the ECDM processing range. This paper dedicated to the investigation of the material removal mechanism and process characteristics for the alumina ceramic surfaces microchannels preparation. Firstly, this study explained the difference of the ECDM critical applied voltage and gas film generation mechanism by analyzing the volt-ampere characteristic curve of 20 wt% NaOH electrolyte with a tool immersed depth of 2 mm and 10 mm respectively. Then, a thermal removal finite element model (FEM) for ECDM was developed. The heat cumulative and intermittent cooling effects applied on the alumina ceramic surface dominated the materiel removal. Additionally, it can be found that the microchannel machining accuracy and bottom surface quality depended on the Gaussian heat source characteristics, gas film formation mechanism, heat accumulation effect, and temperatures spatial and temporal distribution. And a series of single factor experiments for evaluating the parametric studies such as the effect of discharge frequency, applied voltage, duty ratio and tool feed rate on the fabricated microchannel performance are executed. Finally, the complex three-dimensional structures of cross microchannel grid and zigzag microchannel array with variable depth were successfully fabricated on aluminum oxide ceramic surface. Notably, the results highlighted and enriched the ECDM stability, consistency and applicability for alumina ceramic surface microchannel fabrication. [ABSTRACT FROM AUTHOR]

The structure prediction algorithm CALYPSO combined with density functional theory calculations are used to find the high-pressure stable structure of manganese diboride (MnB2) in the pressure range of 0–400 GPa. It is found that the pressure-induced phase transition sequence of MnB2 should be P63/mmc (hP6-MnB2) → Immm (oI18-MnB2) → Pnma (oP12-MnB2) → Imma (oI12-MnB2), and the transition pressure is 35.9, 62.4, and 137.3 GPa, respectively. Among them, oP12-MnB2 is a new stable orthorhombic phase in MnB2 and never have been reported before. At ambient conditions, the calculated hardness of hP6-MnB2 and oI18-MnB2 is 34.5 and 22.9 GPa, respectively, suggesting that they are potentially hard material. However, oP12-MnB2 and oI12-MnB2 just possess a smaller hardness value of 13.9 and 16.2 GPa at the pressure of 80 and 140 GPa, respectively. In addition, the electronic structure and chemical bonds studies showed that the strong covalent bond formed by B-B bonds serve as the primary factor for maintain the structural stability of oP12-MnB2 and oI12-MnB2 under high pressure. Furthermore, at the pressure of 140 GPa, the B-B bonds of oP12 phase exists obvious antibonding characteristics below Femi level. The filling of anti-bonding states is detrimental to the stability of the crystal structure, which is the reason why the oP12 phase is less stable than the oI12 phase at this pressure. [ABSTRACT FROM AUTHOR]

The crystal structures of zirconium diboride have been thoroughly explored up to 200 GPa by applying the particle‐swarm optimization technique in company with first‐principles calculations. The hexagonal ZrB2 with space group of P6/mmm is always stable in the pressure region of 0–200 GPa. Structurally, this structure consists of the intriguing regular ZrB12 hexagonal column and the planar hexagonal B ring unit. In addition, the stable AlB2–ZrB2 configuration is mechanically and dynamically stable as confirmed by the respective calculations of elastic constants and phonon dispersion curves. The hardness values exhibit a shrinking variation upon further compression, which mainly originates from the decreasing brittleness and degree of the directionality of the covalent bonds with the growing pressure. Interestingly, the analyses of the Poisson's ratio, density of states, electron location function and Bader charge substantiate that a combination of covalent and ionic characters exists in the AlB2–ZrB2 crystalline with the formidable covalent interaction in the BB bonds, and partially covalent and partially ionic interactions in the ZrB bonds. The hardness value for this phase unexpectedly reaches 45.41 GPa under ambient pressure, higher than the lower limit of superhard materials. [ABSTRACT FROM AUTHOR]

Machining hard materials with 45–48 HRC is difficult in turning operation because of the improvident cutting parameter selections for the operation. The OHNS (AISI/SAE-01–48HRC) steel is mainly preferred for the production of shafts, gears, cams, and press tools. The OHNS material was turned at a dry state using VP-coated carbide inserts. The seventeen experimental trials were designed by central composite design (CCD) with different levels of cutting parameters, like feed rate, cutting speed, and depth of cut. Design Expert-11 software desirability approach and TOPSIS (Technique for Order Preference by Simulating the Ideal Solution) were used to analyse the experimental results to obtain a single optimal solution that defines better results on metal removal rate (MRR) and surface finish (Ra). RSM solution with 81.3% desirability, the cutting speed of 60 m/min, feed rate of 0.08 mm/rev, and depth of cut 1 mm as the optimal cutting parameters; similarly, TOPSIS algorithm calculation identifies the cutting parameter combinations, such as 40 m/min cutting speed, 0.09 mm/rev feed rate, and 1 mm depth cut to enrich the quality of the machined steel; however, the desirability approach cutting parameter setting is better for the surface finish achievement, while TOPSIS solution is better to obtain significant MRR. The confirmation test results validated for the predicted values of both approaches; as such, the experimental results were maintained better convenience than the predicted one. For the optimum cutting parameter combinations, an MRR of 22.032 gm/min and surface roughness of 0.781 μm were obtained at 60 m/min cutting speed, 0.08 mm/rev feed rate, and 1 mm depth of cut. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) have attracted a significant amount of interest in the past decade as a credible alternative to the lithium‐ion batteries (LIBs) widely used today. The abundance of sodium, along with the potential utilization of electrode materials without critical elements in their composition, led to the intensification of research on SIBs. Hard carbon (HC), is identified as the most suitable negative electrode for SIBs. It can be obtained by pyrolysis of eco‐friendly and renewable precursors, such as biomasses, biopolymers or synthetic polymers. Distinct HC properties can be obtained by tuning the precursors and the synthesis conditions, with a direct impact on the performance of SIBs. In this work, an in‐depth overview of how the synthesis parameters of HC affect their properties (porosity, structure, morphology, surface chemistry, and defects) is provided. Several synthesis‐property relationships are established based on a database created using extensive literature data. Moreover, HC properties are correlated with the electrochemical performance (initial Coulombic efficiency (iCE) and reversible capacity) vs. Na, in half‐cells. The Na‐ion storage mechanisms and solid electrolyte interphase (SEI) formation are discussed along with the HC performance in full‐cell devices, as well as the SIB prototypes and a short history of SIBs enterprises. [ABSTRACT FROM AUTHOR]

This article explores the intricacies of micro-grinding parameter control for hard and brittle materials, with a specific focus on Zirconia ceramics (ZrO2) and Optical Glass (BK7). Given the increasing demand and application of these materials in various high-precision industries, this study aims to provide a comprehensive kinematic analysis of material removal during the micro-grinding process. According to the grinding parameters selected to be analyzed in this study, the ac-max values are between (9.55 nm ~ 67.58 nm). Theoretical modeling of the grinding force considering the brittle and ductile removal phase, frictional effects, the possibility of grit to cut materials, and grinding conditions is very important in order to control and optimize the surface grinding process. This research introduces novel models for predicting and optimizing micro-grinding forces effectively. The primary objective is to establish a micro-grinding force model that facilitates the easy manipulation of micro-grinding parameters, thereby optimizing the machining process for these challenging materials. Through experimental investigations conducted on Zirconia ceramics, the paper evaluates a mathematical model of the grinding force, highlighting its significance in predicting and controlling the forces involved in micro-grinding. The suggested model underwent thorough testing to assess its validity, revealing an accuracy with average variances of 6.616% for the normal force and 5.752% for the tangential force. Additionally, the study delves into the coefficient of friction within the grinding process, suggesting a novel frictional force model. This model is assessed through a series of experiments on Optical Glass BK7, aiming to accurately characterize the frictional forces at play during grinding. The empirical results obtained from both sets of experiments—on Zirconia ceramics and Optical Glass BK7—substantiate the efficacy of the proposed models. These findings confirm the models' capability to accurately describe the force dynamics in the micro-grinding of hard and brittle materials. The research not only contributes to the theoretical understanding of micro-grinding processes but also offers practical insights for enhancing the efficiency and effectiveness of machining operations involving hard and brittle materials. [ABSTRACT FROM AUTHOR]

Transition metal phosphides (TMPs) are promising anode materials for sodium ion battery, thanks to their high theoretical specific capacities. Nevertheless, they suffer from large volume change and from poor conductivity during prolonged cycling. Here we systematically investigate the role of different kinds of single/multi‐wall carbon nanotubes (SWCNTs/MWCNTs) as additives in order to stabilize copper phosphide particles (CuP2) as anode materials in sodium ion batteries (SIBs). All composites show enhancement in the overall capacity and cycling stability compared to the pristine CuP2 due to the well‐connected CNTs on and between the CuP2 particles. At a high currency density of 1 A g−1, CuP2@SWCNTs composite with 13 wt.% SWCNTs can deliver a specific capacity over 400 mAh g−1 for more than 60 cycles, much better than conventional hard carbon materials. The CNTs enhance the conductivity and reduce capacity loss caused by the volume variation of CuP2 based electrode materials. Post‐mortem analysis by scanning electron microscopy depicts a possible battery failure mechanism, whereby the solid electrolyte interface exists in the form of nanospheres distributing at the surface of the electrode. During the repeated cycling (volume change), more fractures and cracks occur resulting in continuous interfacial reactions and consumption of sodium and electrolyte. [ABSTRACT FROM AUTHOR]

Efficient energy storage systems are crucial for the optimal utilization of renewable energy. Sodium‐ion batteries (SIBs) are considered potential substitutes for next‐generation low‐cost energy storage systems due to the low cost and abundance of sodium resources. However, the industrialization of SIBs faces a great challenge in terms of the anode. Hard carbon could be a promising anode material due to its high capacity and low cost which originates from biomass. This study used pre‐treatment and template carbonization methods to extract a hard carbon material from a large amount of discarded biomass in bamboo powder waste. This material has a good initial Coulombic efficiency of 78.6 % and good cycling stability when applied to sodium ion batteries.Typically, the optimal hard carbon material is used as the anode to prepare sodium ion battery prototypes to demonstrate their potential applications. The anode exhibited excellent sodium storage performance with a reversible capacity of 303 mAh ⋅ g−1 at 1 C rate and good cycling performance, retaining 92.0 % of its capacity after 100 cycles. These results demonstrate that BPPHC is a promising candidate for anode material in sodium‐ion batteries. This work suggests that bamboo powder could be a low‐cost anode material for SIBs. [ABSTRACT FROM AUTHOR]

[Display omitted] Hard carbon as a negative electrode material for sodium-ion batteries (SIBs) has great commercial potential and has been widely studied. The sodium-ion intercalation in graphite domains and the filling of closed pores in the low voltage platform region still remain a subject of controversy. We have successfully constructed hard carbon materials with a pseudo-graphitic structure by using polymerizable p -phenylenediamine and dichloromethane as carbon sources. This was achieved by a halogenated amination reaction and oxidative polymerization. It was found that the capacity of hard carbon materials mainly originates from intercalation into graphite domains. The study found that the prepared hard carbon could store 339.33 mAh g−1 of sodium in a reversible way at a current density of 25 mA g−1, and it had an initial coulomb efficiency of 80.23%. It even maintained a reversible sodium storage capacity of 125.53 mAh g−1 at a high current density of 12.8 A g−1. Based on the analysis of hard carbon structure and electrochemical performance, it was shown that the materials conform with an "adsorption-intercalation" mechanism for sodium storage. [ABSTRACT FROM AUTHOR]

High hardness is desirable for thermal insulation materials in various applications to improve wear resistance. However, hard materials like diamond, Si 3 N 4 , and SiC are often accompanied by high thermal conductivity, due to their strong covalent bonds and high Young's modulus, which increase sound velocity and benefit heat transportation. How to achieve concurrent high hardness and low thermal conductivity remains a challenge in thermal insulation materials. In this work, we report (Yb+Ca) co-doped α-SiAlON (Yb 0.5 Ca 0.75 Si 7.5 Al 4.5 O 1.5 N 14.5 , a solid solution of α-Si 3 N 4) with a low thermal conductivity of 3.4 W/(m·K) and a hardness of 18.1 GPa at 25℃. The thermal conductivity of α-SiAlONs co-doped by (Yb+Nd/Lu) were also studied, and we found that phonon scattering could be significantly increased only when there was a remarkable difference in cation mass and radius between the co-doping cations, like that between Yb3+ and Ca2+. Additionally, high-entropy α-SiAlONs co-doped by five kinds of cations were studied (e.g., Nd 0.1 Gd 0.1 Dy0.1Er 0.1 Yb 0.1 Si 9. 5 Al 2.5 ON 15), and we found that the high-entropy strategy is not so effective in pursuing low thermal conductivity in α-SiAlONs. The contribution of different phonon scattering mechanisms in the α-SiAlONs was discussed based on inverse thermal diffusivity. Compared with most other ceramics (e.g., 8YSZ and rare-metal zirconates) with low thermal conductivity, (Yb+Ca) co-doped α-SiAlON has a lower bulk density, higher hardness, and higher toughness, which makes it a potential candidate material for applications requiring both thermal insulation and good mechanical properties. • Concurrent high hardness (18.1 GPa) and low thermal conductivity (3.4 W/(m·K)) are realized in (Yb+Ca) co-doped α-SiAlON. • (Yb+Ca) co-doped α-SiAlON shows advantages in higher hardness, lower bulk density and higher toughness. • The high-entropy strategy seems not so effective in pursuing low thermal conductivity in α-SiAlONs. • The key to achieve low thermal conductivity in α-SiAlONs is to increase extrinsic phonon scattering. [ABSTRACT FROM AUTHOR]

This research focuses on modeling heat transfer in heterogeneous media composed of stacked spheres of paraffin as a perspective polymeric phase-change material. The main goal is to study the requirements of the numerical scheme to correctly predict the thermal conductivity in a periodic system composed of an indefinitely repeated configuration of spherical particles subjected to a temperature gradient. Based on OpenFOAM, a simulation platform is created with which the resolution requirements for accurate heat transfer predictions were inferred systematically. The approach is illustrated for unit cells containing either a single sphere or a configuration of two spheres. Asymptotic convergence rates confirming the second-order accuracy of the method are established in case the grid is fine enough to have eight or more grid cells covering the distance of the diameter of a sphere. Configurations with two spheres can be created in which small gaps remain between these spheres. It was found that even the under-resolution of these small gaps does not yield inaccurate numerical solutions for the temperature field in the domain, as long as one adheres to using eight or more grid cells per sphere diameter. Overlapping and (barely) touching spheres in a configuration can be simulated with high fidelity and realistic computing costs. This study further extends to examine the effective thermal conductivity of the unit cell, particularly focusing on the volume fraction of paraffin in cases with unit cells containing a single sphere. Finally, we explore the dependence of the effective thermal conductivity for unit cells containing two spheres at different distances between them. [ABSTRACT FROM AUTHOR]

Micro-milling of cemented carbides is a challenging task due to their high hardness, low toughness and high wear resistance. Ensuring good surface quality and dimensional accuracy is crucial for extending parts service life, which in turn enhances economical and environmental sustainability. This paper is mainly focused on evaluating surface formation mechanisms, scale effects, fracture behaviour and chip formation using distinct cemented carbide micro-milling tools with multi-layer diamond HF-CVD. In order to achieve higher precision and more efficient micro-milling operations on WC-15Co and WC-10Co, a systematic experimental approach has been carried out. The influence of cutting parameters, achievable surface quality and defects occurrence were thoroughly examined. Experimental results evidence the influence of operational conditions on the chip formation of cemented carbides as well as an important impact of the utilized cutting tool. Micro-pits, cracks, thin ploughing layer and fractured workpiece edges are amongst the observed surface damage mechanisms. A ductile cutting regime of the high-hardness composite material is confirmed, exhibited by the plastic deformation even when small depths of cut are considered. [ABSTRACT FROM AUTHOR]

The practical application of hard carbon in sodium‐ion batteries is limited by insufficient reversible capacity and low initial Coulombic efficiency (ICE), which are caused by the lack of active sites and unstable electrode/electrolyte interface. Herein, a biomass‐derived hard carbon material based on tea stems is proposed, which exhibits an ultrahigh ICE of 90.8%. This remarkable ICE is attributed to the presence of an inorganic‐rich, thin, and robust solid electrolyte interface (SEI) layer. Furthermore, the material demonstrates excellent cycling stability, showing a capacity retention of 99.5% after 500 cycles at 280 mA g−1. Additionally, when it works as the anode material in a sodium‐ion full cell without presodiation, it reaches a high energy density of 212 Wh kg−1 and a superior stability, e.g., retaining 93.1 mAh g−1 after 1000 cycles at 1 A g−1 with a capacity retention of 91.3%. The sodium storage capacity of this material is primarily attributed to a combined adsorption‐intercalation/filling effect as confirmed by in situ XRD and ex situ Raman analyses. These findings make this biomass‐derived hard carbon material a promising candidate for commercial application of sodium‐ion batteries, achieving high performance at low cost. [ABSTRACT FROM AUTHOR]

Grinding damage of hard and brittle materials has a direct impact on part strength and subsequent polishing efficiency. Damage suppression is one of the key research issues in hard and brittle material processing. Due to the uncertain damage evolution law, there is still a lack of optimization methods for the multi-step grinding process under given damage constraints. In this paper, the extended finite element method is used to establish a model between the prefabricated crack depth and final crack depth, which reveals the influence of various existing subsurface damages on crack propagation. It is found that only when the prefabricated crack depth is close to the indentation crack depth on the perfect surface, the final crack depth will be affected to some extent. To optimize the grinding process to achieve low damage, a semi-empirical model for predicting grinding damage is proposed which is suitable for process optimization and does not rely on some difficult-to-obtain parameters. Finally, based on the damage evolution law and prediction model, the core content of this paper is proposed, that is, a multi-step grinding process optimization method with variable grinding depth. This method can minimize the damage while ensuring the same processing efficiency, the damage depth is reduced by 25 %. The effectiveness of the optimization method and the correctness of the damage evolution law are proved by experiments. This method is suitable for engineering applications and has practical significance for understanding the damage evolution mechanism, which is helpful for the suppression of grinding damage and the optimization of the grinding process. • Reveal the evolution mechanism of various existing subsurface damage on crack propagation by XFEM. • Propose a semi-empirical model for grinding damage prediction suitable for process optimization. • Propose a multi-step grinding process optimization method for hard brittle materials with variable grinding depth. • Prove the effectiveness of the optimization method and the evolutionary model through experiments. [ABSTRACT FROM AUTHOR]

In order to achieve high efficiency and low damage processing of hard and brittle materials, composite ultrasonic vibration-assisted face grinding (CUVAFG) has been proposed by comprehensively combining the high efficiency of axial ultrasonic vibration grinding (UVAG) and the low damage of elliptic ultrasonic vibration grinding (EVAG). However, the three-dimensional ultrasonic vibration brings about a more complicated machining mechanism than the previous ultrasonic vibration-assisted grinding methodology. Hence, in order to explore the grinding mechanism in deep, this paper first developed a new model of undeformed chip thickness for CUVAFG from the perspectives of the kinematic mechanism and elastic-plastic deformation mechanism. Then the influences of different processing parameters on interference rate and undeformed chip thickness were further confirmed. Finally, CUVAFG experiments of silicon carbide (SiC) ceramics were conducted to study the relationship between the undeformed chip thickness and the resultant grinding forces, specific grinding energy, ground surface morphology and roughness, and subsurface damage. It is found from the experimental results that the critical chip thickness of brittle-ductile transition in CUVAFG is between 0.31 and 0.35 μm. As the undeformed chip thickness is less than the critical value, the grinding forces and the specific grinding energy increases with the undeformed chip thickness, but the ground surface roughness decreases with improved surface morphology and shallow subsurface damage. After exceeding the critical value, the grinding force remains unchanged, the specific grinding energy decreases, and ground surface roughness increases with deteriorated surface morphology and deepened subsurface damage. For the purpose of good machining surface integrity, it is essential to guarantee that the undeformed chip thickness is less than the critical value. The computational and experimental results have demonstrated the contribution of the developed undeformed chip thickness model to understanding the grinding performance of hard and brittle material by CUVAFG. • A novel undeformed chip thickness model that considers the elastic-plastic deformation of workpiece material is proposed. • The interference area and rate are proposed to explain the influence of processing parameters on undeformed chip thickness. • The critical undeformed chip thickness of brittle-ductile transition for silicon carbide by CUVAFG is confirmed in the range of 0.31–0.35 μm. • The depth of the subsurface damage layer increases from 2.1 μm to 66.7 μm with the increase of undeformed chip thickness. • The grinding forces, ground surface roughness, and specific grinding energy are reduced by 30 %, 42 %, and 93 %, respectively. [ABSTRACT FROM AUTHOR]

Wire cut electric discharge machining (WCEDM) is a flexible and more essential for the precise machining of hard materials like composites and super alloys. In order to improve the surface texture as the main focus of the WCEDM process, the expansion of the fundamental procedural perceptive is very important. This paper mainly focuses on the prediction of surface quality of Al-Fe-Si alloy (AA8011) matrix composites during the WCEDM process. For the fabrication of composites, the varying proportions (0, 5, 10 and 15 wt.%) of ZrO2 ceramic particle were incorporated with AA8011 matrix alloy by using stir casting method. In the machining studies, to investigate the effects of reinforcement (wt. %) and the WCEDM process parameters, namely pulse current (amps), pulse-on time (μ s) and pulse-off time (μ s) on machining performance like surface roughness (SR) of the proposed composites. Based on the selection of parameters and their levels, an L16 (44) orthogonal array was most suitable for conducting the WCEDM experiments. A Taguchi technique was employed in this study to determine the optimal conditions of machining parameters through the signal-to-noise (S/N) ratio analysis. The result shows that the minimum SR is achieved at 5 wt.% of reinforcement, 6 amps of pulse current, 110 μ s of pulse-on time and 50 μ s of pulse-off time, respectively. Analysis of variance (ANOVA) results revealed that the reinforcement wt.% has the primary significant factor on SR, trailed by pulse-on time and pulse current, respectively. Furthermore, the regression equation was also developed to predict the SR and that values well agree with the experimental SR. [ABSTRACT FROM AUTHOR]

A pathological metatarsal of the early-branching megaraptoran Phuwiangvenator yaemniyomi from the Lower Cretaceous of Thailand is here studied. It was CT-scanned and compared with pathology in other dinosaurs and living animals. The result shows that the palaeopathology in Phuwiangvenator was a traumatic fracture, specifically a greenstick fracture, based on the incomplete breakage of the bone, which occurred only on one side and twisted or distorted in the opposite direction to the force that caused the pathology. The cause of the fracture was possibly by accidentally hitting or kicking hard material, fighting, or falling to the ground. Phuwiangvenator was probably an adolescent when it was injured and survived the incident. This is the second report of a greenstick fracture in Theropoda after Akansaurus fridayii; the first detailed analysis of palaeopathology in Megaraptora; and the first record and detailed description of palaeopathology in non-avian theropods in Southeast Asia. [ABSTRACT FROM AUTHOR]

Hard carbon has been widely used in anode of lithium/sodium ion battery, electrode of supercapacitor, and carbon molecular sieve for CO2 capture and hydrogen storage. In this study the lignin derived hard carbon products are investigated, and the conclusions are abstracted as follows. (1) The lignin derived hard carbon products consist of microcrystal units of sp2 graphene fragments, jointed by sp3 carbon atoms and forming sp2–sp3 hybrid hard carbon family. (2) From the lignin precursors to the sp2–sp3 hybrid hard carbon products, most carbon atoms retain their original electron configurations (sp2 or sp3) and keep their composition in lignin. (3) The architectures of lignin-derived hard carbon materials are closely dependent on the forms of their lignin precursors, and could be preformed by different pretreatment techniques. (4) The carbonization of lignin precursors follows the mechanism "carbonization in situ and recombination nearby". (5) Due to the high carbon ratio and abundant active functional groups in lignin, new activation techniques could be developed for control of pore size and pore volume. In general lignin is an excellent raw material for sp2–sp3 hybrid hard carbon products, a green and sustainable alternative resource for phenolic resin, and industrial production for lignin derived hard carbon products would be feasible. [ABSTRACT FROM AUTHOR]

This work aims to provide new insights into the link between the growth mechanisms of functionalized plasma polymer films (PPFs) and the substrate temperature (TS). By means of AFM‐based techniques, it has been demonstrated that the mechanical behavior of the coatings is dramatically affected by TS and the precursor employed (i.e., 1‐propanethiol or 1‐propylamine). While propylamine‐based PPFs behave as hard elastic materials regardless of TS, propanethiol‐based PPFs evolve from viscous liquids to elastic solids with increasing TS. This behavior can be understood considering the glass transition temperature of PPF. For both precursors, the latter is correlated to the cross‐linking density controlled through the energy density brought by positive ions to the growing film. [ABSTRACT FROM AUTHOR]

Flexible, stretchable, and sensitive multidirectional sensing systems that can decouple different mechanical inputs and identify multidirectional signals are crucial for dynamic human signal perception and intelligent human–computer interaction. Most reported multidirectional sensors are suitable for discriminating in‐plane deformation directions, and the sensing materials are difficult to balance between stretchability and mechanical strength. Here, a segmented embedded structure strategy inspired by the interlaced structure of cartilage is proposed. This strategy combines soft and hard materials in a topological and zipper‐shear chain manner and balances the performance of reinforced composites with flexibility and high toughness. In the case of segmented embedded hydrogels (SEHs), a wearable multidirectional sensing system that can decouple and identify planar strain/pressure is constructed. The multidirectional sensing system exploits the inherent anisotropy and layered structure design of composites to decouple the sensing functions. Supported by machine learning algorithms, the high accuracy demonstration of the multidirectional sensors in typical multidirectional motion joint posture monitoring and recognition confirms their potential in practical applications such as personal health sensing and human–computer interaction. [ABSTRACT FROM AUTHOR]

In the pursuit of rare earth-lean permanent magnets for green technologies, microstructural optimisation offers a promising strategy to enhance coercivity while minimising critical element content. For this approach, the combination of experimental work on hard magnetic films and numerical investigations is necessary. However, computational limitations restrict micromagnetics to small systems, motivating the development of a reduced order model for investigating large multigrain systems. The model is based on the embedded Stoner-Wohlfarth method and is used to investigate the influence of a nonmagnetic grain boundary phase thickness and the aspect ratio of the magnetic grains on the overall coercivity. It is possible to simulate large NdFeB multigrain structures which can be compared to hard magnetic films. We derive design recommendations to increase coercivity by increasing the grain boundary phase thickness and the aspect ratio of the grains in hard magnetic materials. [ABSTRACT FROM AUTHOR]

We propose a novel type of spin wave computing device, based on a bilayer structure that includes a "bias layer" made from a hard magnetic material and a "propagation layer" made from a magnetic material with low damping, for example, yttrium garnet or permalloy. The bias layer maintains a stable pre-recorded magnetization pattern, which generates a bias field with a desired spatial dependence, which in turn sets the equilibrium magnetization inside the propagation layer. When an external source applies an RF field to the propagation layer, excited spin waves scatter on the magnetization's inhomogeneities resulting in complex interference behavior. This scattering interference can be utilized to perform a variety of mathematical operations including Vector-Matrix multiplication. The spatial dependence of such magnetization patterns can be estimated via perturbation theory. [ABSTRACT FROM AUTHOR]

The discovery of new magnetic materials is a big challenge in the field of modern materials science. We report the development of a new extension of the evolutionary algorithm USPEX, enabling the search for half-metals (materials that are metallic only in one spin channel) and hard magnetic materials. First, we enabled the simultaneous optimization of stoichiometries, crystal structures, and magnetic structures of stable phases. Second, we developed a new fitness function for half-metallic materials that can be used for predicting half-metals through an evolutionary algorithm. We used this extended technique to predict new, potentially hard magnets and rediscover known half-metals. In total, we report five promising hard magnets with high energy product (|BH|MAX), anisotropy field (Ha), and magnetic hardness (κ) and a few half-metal phases in the Cr–O system. A comparison of our predictions with experimental results, including the synthesis of a newly predicted antiferromagnetic material (WMnB2), shows the robustness of our technique. [ABSTRACT FROM AUTHOR]

Alkaline sodium hydroxide/sodium silicate-activating high-purity metakaolin geopolymerization is described in terms of metakaolin deconstruction in tetrahedral hydrate silicate [O[Si(OH)3]]− and aluminate [Al(OH)4]− ionic precursors followed by their reassembling in linear and branched sialates monomers that randomly copolymerize into an irregular crosslinked aluminosilicate network. The novelty of the approach resides in the concurrent thermo-calorimetric (differential scanning calorimetry, DSC) and rheological (dynamic mechanical analysis, DMA) characterizations of the liquid slurry during the transformation into a gel and a structural glassy solid. Tests were run either in temperature scan (1 °C/min) or isothermal (20 °C, 30 °C, 40 °C) cure conditions. A Gaussian functions deconvolution method has been applied to the DSC multi-peak thermograms to separate the kinetic contributions of the oligomer's concurrent reactions. DSC thermograms of all tested materials are well-fitted by a combination of three overlapping Gaussian curves that are associated with the initial linear low-molecular-weight (Mw) oligomers (P1) formation, oligomers branching into alumina-rich and silica-rich gels (P2), and inter- and intra-molecular crosslinking (P3). The loss factor has been used to define viscoelastic behavioral zones for each DMA rheo-thermogram operated in the same DSC thermal conditions. Macromolecular evolution and viscoelastic properties have been obtained by pairing the deconvoluted DSC thermograms with the viscoelastic behavioral zones of the DMA rheo-thermograms. Two main chemorheological behaviors have been identified relative to pre- and post-gelation separation of the viscoelastic liquid from the viscoelastic solid. Each comprises three behavioral zones, accounting for the concurrently occurring linear and branching oligomerization, aluminate-rich and silica-rich gel nucleations, crosslinking, and vitrification. A "rubbery plateau" in the loss factor path, observed for all the testing conditions, identifies a large behavioral transition zone dividing the incipient gelling liquid slurry from the material hard setting and vitrification. [ABSTRACT FROM AUTHOR]

Due to the unique physical property, the surface integrity is a critical indicator to characterize the processing quality for hard and brittle materials. In this study, the ZrO 2 ceramic is taken as a representative to investigate the surface integrity during ultrasonic vibration-assisted polishing (UVAP) processing. The effects of processing parameters on surface micro-morphology, surface hardness, scratch property and residual stress are analyzed by UVAP orthogonal experiments. The experiment results indicate that the UVAP processing can effectively improve the surface integrity of the ZrO 2 ceramic. The research results are of great significance in guiding the UVAP controlled processing of hard and brittle materials. [ABSTRACT FROM AUTHOR]

Mineralized connective tissues represent the hardest materials of human tissues, and polymer based composite materials are widely used to restore damaged tissues. In particular, light activated resins and composites are generally considered as the most popular choice in the restorative dental practice. The first purpose of this study is to investigate novel highly reinforced light activated particulate dental composites. An innovative additive manufacturing technique, based on the extrusion of particle reinforced photo-polymers, has been recently developed for processing composites with a filler fraction (w/w) only up to 10%. The second purpose of this study is to explore the feasibility of 3D printing highly reinforced composites. A variety of composites based on 2,2-bis(acryloyloxymethyl)butyl acrylate and trimethylolpropane triacrylate reinforced with silica, titanium dioxide, and zirconia nanoparticles were designed and investigated through compression tests. The composite showing the highest mechanical properties was processed through the 3D bioplotter AK12 equipped with the Enfis Uno Air LED Engine. The composite showing the highest stiffness and strength was successfully processed through 3D printing, and a four-layer composite scaffold was realized. Mechanical properties of particulate composites can be tailored by modifying the type and amount of the filler fraction. It is possible to process highly reinforced photopolymerizable composite materials using additive manufacturing technologies consisting of 3D fiber deposition through extrusion in conjunction with photo-polymerization. [ABSTRACT FROM AUTHOR]

The peculiarities of wear of working bodies of housings of steel and matrix drill bits and drill heads were considered and studied, and the criteria for their reparability were determined. The degree of wear of working bodies of the landing sockets for diamond carbide cutters was investigated. The methods of preparing the worn areas of the working body for their restoration by the method of arc surfacing were optimized. Special attention was paid to studying the microstructure of the interface between the base and deposited metals: steel 45 + TeroCote 7888T composite material; steel 45 + self-fl uxing steel bar Diamax M; steel 45 + tape relit LZ-11-7; VK10 hard alloy + TeroCote 7888T composite material. The structure of the TeroCote 7888T protective coating on VK10 hard alloy and steel 45 was found to provide exceptionally eff ective protection against corrosion and abrasive wear. On the basis of research, a technology was developed for repair of the working bodies of the blades of housings of steel and matrix drill bits, which allows extending their operational life. Steel and matrix drill bits and drill heads, after their restoration, passed industrial tests in Poltava, Kharkiv and Donetsk regions during drilling of gas and oil wells. It was established that the use of repaired drill bits when drilling oil and gas wells allows extending their life and saving 30...50% of the initial cost of a specifi c type of drill bit. 11 Ref., 2 Tabl., 10 Fig. [ABSTRACT FROM AUTHOR]

Due to the unique physical property, the surface integrity is a critical indicator to characterize the processing quality for hard and brittle materials. In this study, the ZrO 2 ceramic is taken as a representative to investigate the surface integrity during ultrasonic vibration-assisted polishing (UVAP) processing. The effects of processing parameters on surface micro-morphology, surface hardness, scratch property and residual stress are analyzed by UVAP orthogonal experiments. The experiment results indicate that the UVAP processing can effectively improve the surface integrity of the ZrO 2 ceramic. The research results are of great significance in guiding the UVAP controlled processing of hard and brittle materials. [ABSTRACT FROM AUTHOR]

Vanadium carbide is important for industrial applications because of its high hardness, high temperature resistance, high chemical, and thermal stability. It is generally obtained from the reaction between V and C powders at a high temperature ranging from 1100 to 1500°C. Investigations on these high strength, high abrasion resistant, hard materials have been intensified in recent years and consequently, significant improvements have been achieved. In this study, VC alloys are produced with low cost processes, by reducing the oxides of their components by SHS methods and ball mill-assisted carbothermal reduction. In the experimental stage, V2O5 was used as oxidized Vanadium source, Cblack as carbon source, magnesium and Cblack as reductant. In the study, VC powders were synthesized by two different methods and optimum production conditions were determined. Furthermore, the effect of different stoichiometric charge components and the effect of experiment durations were realized by X-ray diffraction, HSC Chemistry, and SEM analyses for different reductants. [ABSTRACT FROM AUTHOR]

The Gas Additive Powder Mix near Dry Electric Discharge Machining (GAPMND-EDM) serves a manufacturing purpose, specifically for cutting hard materials. This involves the removal of material from a workpiece via fusion, ablation, and evaporation caused by the heat energy generated through electric sparks during energy supply. The process offers several advantages in terms of performance and characteristics. This research project aims to optimize key process parameters, including material removal rate, surface roughness, residual stresses, and microhardness. The study employs a methodology that combines the standard deviation-based objective weighting method with GRA (Gray Relational Analysis) optimization to enhance the hybrid GAPMND-EDM process when applied to EN-31 material. Experimental runs were conducted to evaluate the impact of various input factors, such as pulse-on time, discharge current, dielectric fluid pressure, and metallic powder concentration. The taguchi-based GRA method was utilized for this purpose, and the experimental design followed an L-27 orthogonal array with the assistance of Minitab-19 software. A total of 27 experiments were performed, encompassing diverse combinations of process parameters. Subsequently, an ANOVA (Analysis of Variance) was executed to analyze the influence of pulse-on time, discharge current, dielectric fluid pressure, and metallic powder concentration on Material Removal Rate (MRR), Surface Roughness (SR), Residual Stress (RS), and Microhardness (MH). The result shows the optimal combination of parameters, denoted as A2B2C2D1, was identified as the preferred configuration. [ABSTRACT FROM AUTHOR]

Summary: Hard capsules are a frequently used oral medication delivery form. This study aims to evaluate the potential of tilapia fish gelatine as a suitable material for hard capsules, by analysing various gelatine properties under different extraction temperatures (50, 60, 70, and 80 °C) and extraction periods (6 and 12 h). The results showed a range of values for the gelatine yield (22–33% (w/w)), gel strength (141–360 g), molecular weight distribution (140–300 kDa), and amino acid composition (185–220/1000 residues). FG70‐12 (296) and FG60‐6 (266) were found to have gel strength between 200 and 300 g thus suitable to be used as hard capsule material. Interestingly, the strongest gelatine having 360 g gel strength obtained from FG50‐6 (fish gelatine extracted at 50 °C for 6 h) became the essential ingredient for preparing hard capsules because two times dipping was enough to obtain the standard weight and thickness. A slight loss of moisture was identified during drying and rapid dissolution (4–8 min) detected from fish gelatine capsule at pH 6.8 or below. Therefore, hard capsules for pharmaceutical applications could be developed from fish gelatine as an alternative gelatine with similar properties as commercial hard capsules and satisfying the pharmacopoeia standard. [ABSTRACT FROM AUTHOR]

The machining of extremely hard material in conventional machining requires high energy. Therefore stress-free, burr-free, and high-accuracy machining technique like Electro Chemical Micro Machining (ECMM) with extra features is recommended. To improve efficiency, various electrolytes such as Magnet Associated Electrolytes (MGAE), Metal Particle Mixed Electrolytes (MPME), and Carbon Pellets Mixed Electrolytes (CPME) are employed. The micro-holes were drilled over the work material MONEL 400 alloy. The parameters for the studies are electrolyte type, concentration (g/l), machining voltage (V), and duty cycle (%). The responses of ECMM are estimated through material removal rate (MRR) in μm/sec and overcut in μm. The results are optimized using Multi-objective optimization based on ratio analysis (MOORA) and VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR). Both techniques produce the same optimal parameter, 18th experiment CPME, 50% duty cycle, 11 V machining voltage, and 28 g/l electrolyte concentration. It is the best optimal parameter solution for machining. According to the ANOVA table of both, the type of electrolyte plays a 62.6% and 60.37% contribution, respectively, to machining performance. Furthermore, the scanning electron microscope (SEM) image analysis perused on the micro holes to extend the effect of different electrolytes on machining surfaces. [ABSTRACT FROM AUTHOR]

A Mo2NiB2-type high-entropy boride ceramic with the nominal formula of (Mo0.5W0.5)2(Fe0.3Co0.35Ni0.35)B2 (abbreviated as X3B2) was synthesized by vacuum sintering. The phase structure, crystalline construction, bonding, and hardness properties were clarified in detail by first-principles calculations and experiment. The results show that the as-synthesized sample exhibits single phase and satisfied compositional homogeneity. Moreover, it can be obtained that both Mo–B bonds and W–B bonds in X3B2 exhibit the covalent characteristics, while the binding of Mo–B is stronger than the other. Initial property assessments show that the Vickers hardness of X3B2 is generally more than 20% higher than the reported Mo2NiB2. These results suggest an idea to achieve high hard and high-performance materials via exploring high-entropy ternary-boride ceramic. [ABSTRACT FROM AUTHOR]

This perspective is an overview of the recent advances in teeth microcrack (MC) research, where there is a clear tendency towards a shift from two-dimensional (2D) to three-dimensional (3D) examination techniques, enhanced with artificial intelligence models for data processing and image acquisition. X-ray micro-computed tomography combined with machine learning allows 3D characterization of all spatially resolved cracks, despite the locations within the tooth in which they begin and extend, and the arrangement of MCs and their structural properties. With photoluminescence and micro-/nano-Raman spectroscopy, optical properties and chemical and elemental composition of the material can be evaluated, thus helping to assess the structural integrity of the tooth at the MC site. Approaching tooth samples having cracks from different perspectives and using complementary laboratory techniques, there is a natural progression from 3D to multi-modal imaging, where the volumetric (passive: dimensions) information of the tooth sample can be supplemented by dynamic (active: composition, interaction) image data. Revelation of tooth cracks clearly shows the need to re-assess the role of these MCs and their effect on the structural integrity and longevity of the tooth. This provides insight into the nature of cracks in natural hard materials and contributes to a better understanding of how bio-inspired structures could be designed to foresee crack propagation in biosolids. [ABSTRACT FROM AUTHOR]