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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]

Lithium niobate (LN) is used in diverse applications, such as spectroscopy, remote sensing, and quantum communications. The emergence of lithium-niobate-on-insulator (LNOI) technology and its commercial accessibility represent significant milestones. This technology aids in harnessing the full potential of LN's properties, such as achieving tight mode confinement and strong overlap with applied electric fields, which has enabled LNOI-based electro-optic modulators to have ultra-broad bandwidths with low-voltage operation and low power consumption. As a consequence, LNOI devices are emerging as competitive contenders in the integrated photonics landscape. However, the nanofabrication, particularly LN etching, presents a notable challenge. LN is hard, dense, and chemically inert. It has anisotropic etch behavior and a propensity to produce material redeposition during the reactive-ion plasma etch process. These factors make fabricating low-loss LNOI waveguides (WGs) challenging. Recognizing the pivotal role of addressing these fabrication challenges for obtaining low-loss WGs, our research focuses on a systematic study of various process steps in fabricating LNOI WGs and other photonic structures. In particular, our study involves (i) careful selection of hard mask materials, (ii) optimization of inductively coupled plasma etch parameters, and finally, (iii) determining the optimal post-etch cleaning approach to remove redeposited material on the sidewalls of the etched photonic structures. Using the recipe established, we realized optical WGs with a total (propagation and coupling) loss value of −10.5 dB, comparable to established values found in the literature. Our findings broaden our understanding of optimizing fabrication processes for low-loss lithium-niobate WGs and can serve as an accessible resource for advancing the LNOI technology. [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]

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]

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]

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]

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]

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]

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]

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]

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]

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 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]

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]

Electrochemical micromachining (ECM) is a nontraditional method used for machining operations in hard and light materials with fixed or varying parameters. In this study, magnesium AZ31 alloy was micro machined using two types of electrolyte supply systems, namely electrolyte flooding and minimum quantity electrolyte (MQE). Experimental investigations were performed using TOPSIS and artificial neural network (ANN) techniques with types of electrolyte supply system, electrolyte concentration (EC), duty cycle (%), and machining voltage (V) as the input parameters, and material removal rate (MRR) and over cut (OC) as the outputs. Single and multi-objective parameter optimization was performed using Taguchi, TOPSIS, and ANN techniques. The machined microholes were analyzed using scanning electron microscopy. According to the TOPSIS results, under optimal conditions, a high MRR value and minimum OC of 1.282 µm/s and 66 µm, respectively, were obtained. The results of TOPSIS were verified using the developed ANN architecture. [ABSTRACT FROM AUTHOR]

Boron carbide is one of the hardest materials in the world which can be synthesized by various methods. The most common one is a carbothermic or magnesiothermic reduction of B2O3 performed at high temperatures, where the obtained powder still requires grinding and purification. The goal of this research is to present the possibility of synthesizing B4C nanoparticles from elements via vapor deposition and modifying the morphology of the obtained powders, particularly those synthesized at high temperatures. B4C nanoparticles were synthesized in the process of direct synthesis from boron and carbon powders heated at the temperature of 1650 °C for 2 h under argon and characterized by using scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction analysis, and dynamic light scattering measurements. The physicochemical characteristics of B4C nanoparticles were determined, including the diffusion coefficients, hydrodynamic diameter, electrophoretic mobilities, and zeta potentials. An evaluation of the obtained B4C nanoparticles was performed on several human and mouse cell lines, showing the relation between the cytotoxicity effect and the size of the synthesized nanoparticles. Assessing the suitability of the synthesized B4C for further modifications in terms of its applicability in boron neutron capture therapy was the overarching goal of this research. [ABSTRACT FROM AUTHOR]

A new martensitic stainless steel with high nitrogen and carbon content at low pressures was designed using the CALPHAD method. The chemical composition of the steel was checked by optical emission spectrometry, obtaining 0.17 wt%-N and 1.33 wt%-C. Scanning electron microscopy (SEM) analyses were carried out for microstructural characterization. The properties of the steel were assessed by Rockwell hardness and potentiodynamic polarization tests in 0.6M NaCl. The steel showed maximum hardness values of 60 HRC, regarded as a hard material. However, the passive film formation was prevented by the high carbon content promoting excessive Cr-rich carbides. [ABSTRACT FROM AUTHOR]

The search for novel multifunctional alternative materials remains a prominent and active area of research in materials science. Transition-metal borides have gained significant attention due to their exceptional performance in various materials applications. However, the understanding of the Cr–Mo–B system is currently limited. In this study, we employ first-principles calculations to explore and analyse the structural properties, stability, mechanical properties, and electronic properties of fourteen ternary compounds within the Cr–Mo–B system. Our calculations demonstrate that these compounds exhibit both thermodynamic and mechanical stability, with metallic properties observed. Remarkably, the Vickers hardness values of these compounds exceed 20 GPa, signifying their classification as hard materials. The findings of our studies provide valuable insights that can facilitate experimental synthesis and validation of such materials, further advancing the field of transition-metal borides. [ABSTRACT FROM AUTHOR]

Rare earth doped cobalt ferrites with the chemical formula CoFe2-xPrx O4 and CoFe2-xHoxO4, (x = 0.00 to 0.1 in the step of 0.025) successfully synthesized by sol-gel auto combustion method. The synthesised precursors calcinated at 600 oC for 4 hours in an air atmosphere. XRD patterns of calcinated Pr3+ and Ho3+ substituted cobalt ferrite samples show the formation of cubic spinel structure. The Lattice constant, X-ray density, and hopping lengths increase with increasing Pr3+ and Ho3+ concentration. IR spectra of calcinated samples illustrate two distinguishable absorption bands in the range 700 - 755 cm-1 (1) and 452 - 495 (2) cm-1 and are the characteristics of spinel ferrites. SEM micrographs show spherical-shaped particles in the samples. The TEM micrograph shows a homogeneous and uniform distribution of the sample particles. Observed hysteresis loops illustrate the characteristic behavior of hard magnetic material. The remanence ratio was served from 0.317 to 0.347 for Pr3+ substituted cobalt ferrite and 0.451 to 0.467 for Pr3+ and Ho3+ substituted cobalt ferrite. [ABSTRACT FROM AUTHOR]

Hard and brittle materials have excellent physical and mechanical properties and are widely used in the fields of microelectronics and optoelectronics. However, due to their high hardness and brittleness, the machining quality of a workpiece struggles to meet the requirements of practical applications. In order to improve the surface quality of deep-hole machining of hard and brittle materials, this article analyzes the formation mechanism of surface roughness and the exit-chipping width during the drilling machining of hard and brittle materials and establishes a mathematical prediction model for the surface roughness and the exit-chipping width of hard and brittle materials using a trepanning cutter. The experimental study on K9 optical glass machining shows that the surface roughness of the workpiece and the exit-chipping width increase with the increase in feed rate, and decrease with the increase in rotational speed. Through comparison and verification between theoretical and experimental values, the average errors of workpiece surface roughness and the exit-chipping width are 13.15% and 6.73%, respectively. This article analyzes the reasons for the errors. The results indicate that the theoretical model proposed in this article can be used to predict the surface roughness and the exit-chipping width of hard and brittle materials processed under the same conditions, providing a theoretical basis to optimize process parameters to improve the surface quality of the workpiece. [ABSTRACT FROM AUTHOR]

In this paper, spark plasma sintering was used to obtain and investigate (Pb0.97Ba0.03)(Zr0.98Ti0.02)1−xSnxO3 (PBZTS) ceramic materials for x = 0, 0.02, 0.04, 0.06, and 0.08. Crystal structure, microstructure, dielectric and ferroelectric properties, and electrical conductivity tests of a series of samples were carried out. The SPS sintering method ensures favorable dielectric and ferroelectric properties of PBZTS ceramic materials. X-ray studies have shown that the material has a perovskite structure. The samples have a densely packed material structure with properly crystallized grains. The fine-grained microstructure of the PZBZTS material with high grain homogeneity allows the application of higher electric fields. Ceramic samples obtained by the SPS method have higher density values than samples obtained by the classical method (FS). The permittivity at room temperature is in the range of 245–282, while at the phase transition temperature is in the range of 10,259–12,221. At room temperature, dielectric loss factor values range from 0.006 to 0.036. The hysteresis loops of PBZTS ceramics have a shape typical for ferroelectric hard materials, and the remnant polarization values range from 0.32 to 0.39 µC/cm2. The activation energy Ea values of the PBZTS samples result mainly from the presence of oxygen vacancies. The PZT material doped with Ba and Sn and sintered via the SPS method has favorable physical parameters for applications in modern devices such as actuators or pulse capacitors. [ABSTRACT FROM AUTHOR]

A new monoclinic carbon crystal with the space group C2/c was uncovered; its unit cell comprises 32 carbon (C32) atoms. This full sp³-bonded carbon phase is dynamically and mechanically stable. The results show that C2/c-C32 has excellent mechanical properties, with its shear modulus and Vickers hardness being 343 and 56 GPa, respectively. Based on the elastic anisotropic calculations, C2/c-C32 is confirmed to be an anisotropic material. Notably, C2/c-C32 has a direct band gap structure with a band gap of 2.50 eV. [ABSTRACT FROM AUTHOR]

Bulk metallic glass (BMG) is one of the predominant materials that are progressively used in the aerospace, medical devices, electronics, sporting goods, and engineering materials. Making of components by BMG is still confrontation. Conventional methods of machining are restricted in use due to more tool wear and slower processing efficiency. Non-traditional methods of machining have been widely used for processing hard materials. Wire electrical discharge machining (WEDM) is one among the promising approaches of machining for hard and conductive materials, especially for the new BMG metal material. The preliminary aim of this exploration is to predict the temperature field distribution using the modified Gaussian heat source mode during WEDM multi-pulse discharge process. The effects of various variables (pulse off time and peak current) on the pit depth and surface roughness were investigated. The influence of the main parameters on the machining performance was investigated using Taguchi's orthogonal arrays. The excellent surface quality is obtained at the optimized condition of a pulse on time of 4 μs, pulse off time of 25 μs, and a peak current of pulse on time. [ABSTRACT FROM AUTHOR]

Due to the excellent properties of Ti (C,N)-based ceramics, such as high hardness, excellent wear resistance, exceptional thermal deformation resistance, and sound chemical stability, they have been widely used in cutting tools or molds. Thus, revealing their tribological behavior against hard materials is of great significance. Some studies have reported the tribological behavior of Ti(C,N)-based cermets and hard cermets, but so far, the effects of Mo2C additions on the frictional properties of Ti(C,N)-based cermets are still unclear. In this study, Ti(C,N)-10WC-1Cr3C2-5Co-10Ni-x Mo2C cermets (x = 4, 6, 8, 10 and 12 wt.%) were sintered using a vacuum hot-pressing furnace. Furthermore, the core–rim morphologies of the sintered samples were observed in SEM images. Then, the wear resistance of the cermets was studied against a Si3N4 ball at a 50 N load using the fretting wear test. Finally, the wear mechanism was characterized using a combination of SEM, EDS and XPS. The experimental results indicated that the wear mechanisms of the cermets were mainly abrasive wear, adhesive wear, and the formation of an oxide film. As the content of Mo2C increased from 4 wt.% to 12 wt.%, the friction coefficient and wear volume had a variation law of first decreasing and then decreasing, and reached minimum values at 6 wt.% and 12 wt.%, and the lowest friction coefficient and wear rate were 0.49 and 0.9 × 10−6 mm3/Nm, respectively. The 6 wt.% Mo2C greatly improved the hardness and fracture toughness of the cermet, while the 12 wt.% Mo2C promoted the formation of an oxide film and protected the friction surface. The cermet with 6 wt.% Mo2C is recommended because it has comprehensive advantages in terms of its mechanical properties, tribological properties, and cost. [ABSTRACT FROM AUTHOR]

The exploration of coarse-grained WC cemented carbide has become a research hotspot for its application in the fields of rock cutting and mining; a key issue is how to achieve uniform dispersion and densification of the sintered phase, as well as how to obtain better mechanical properties. In this paper, chemical co-precipitation, combined with hydrogen reduction, was adopted. CoCl2·6H2O and CeCl3 were used as precursors to coat Co nanoparticles on the surface of WC powder while introducing different contents of cerium; the samples were then sintered and densified to obtain WC-Co(Ce) hard alloy materials. On the surface of the obtained WC particles, the distribution of Co(Ce) nanoparticles was uniform and dense, and the average particle size after sintering was 4.2 μm, which lies in the coarse-grained range. The addition of cerium elements significantly improves the flexural strength and impact toughness; when the cerium content was 0.5% and 0.6%, they increased to 2487 MPa and 36.1 kJ/m2, respectively. The addition of Co(Ce) through the co-precipitation method could achieve a uniform coating of the Co phase, along with the uniform dispersion and densification of the sintered phase, giving the WC-Co(Ce) cemented carbide excellent properties. [ABSTRACT FROM AUTHOR]

High performance magnetic abrasive particles (MAPs)can contribute to the promotion of magnetic abrasive finishing (MAF) industry. In this work, environmentally friendly spherical polycrystalline diamond magnetic abrasive particles (PCD-MAPs) were prepared by plasma molten metal powders bonding with hard materials. The effects of inlet mode, outlet angle and powder concentration on the erosion wear of the spray tray were first investigated, followed by the effect of PCD powder concentration on the preparation of MAPs, and finally the microscopic morphology, phase composition, particle size distribution, magnetic properties and finishing performance of the MAPs were characterised and analyzed. The results revealed that: the erosion wear of the spray tray was smaller for the opposing inlet type with an outlet angle of 65°; the PCD-MAPs were regular spherical; the cutting edge of PCD was not carbonized and mechanically bonded to the surface layer of iron powder tightly and uniformly; the concentration of PCD powder affected the bonding number on the surface of iron powder particles; the proportion of particle size distribution between 160–212 μm and the saturation magnetic induction intensity decrease with increasing PCD concentration; the recovered PCD powder can still be used; the Ra value of TC4 titanium alloy decreases from 0.386 μm to 0.096 μm within 25 min, and the service life of PCD-MAPs exceeds 60 min. This study can provide technical support for the bonding of PCD/metal composites. [ABSTRACT FROM AUTHOR]

Ultrasonic-assisted inner diameter machining is a slicing method for hard and brittle materials. During this process, the sawing force is the main factor affecting the workpiece surface quality and tool life. Therefore, based on indentation fracture mechanics, a theoretical model of the cutting force of an ultrasound-assisted inner diameter saw is established in this paper for surface quality improvement. The cutting experiment was carried out with alumina ceramics (99%) as an exemplar of hard and brittle material. A six-axis force sensor was used to measure the sawing force in the experiment. The correctness of the theoretical model was verified by comparing the theoretical modeling with the actual cutting force, and the influence of machining parameters on the normal sawing force was evaluated. The experimental results showed that the ultrasonic-assisted cutting force model based on the six-axis force sensor proposed in this paper was more accurate. Compared with the regular tetrahedral abrasive model, the mean value and variance of the proposed model's force prediction error were reduced by 5.08% and 2.56%. Furthermore, by using the proposed model, the sawing processing parameters could be updated to improve the slice surface quality from a roughness Sa value of 1.534 µm to 1.129 µm. The proposed model provides guidance for the selection of process parameters and can improve processing efficiency and quality in subsequent real-world production. [ABSTRACT FROM AUTHOR]

Zirconia toughened alumina (ZTA) cutting tools are widely used for machining hard and wear-resistant materials. However, the processing of ZTA ceramic cutting tools with complex shapes using traditional methods is difficult and time-consuming. Until now, to the best of our knowledge, commercial ceramic cutting tools do not contain grooves because it is very difficult to process grooves on the ceramic cutting tool, resulting from the feature of high hardness and brittle attribute of ceramics. This study investigated high-performance, complex-shaped zirconia-toughened alumina (ZTA) ceramic cutting tools equipped with a chip breaker for the first time. The investigated samples were prepared using vat photopolymerization based 3D printing combined with a hot isostatic sintering process. The relative density of 99.34%, Vickers hardness of 17.98 ± 0.20 GPa, bending strength of 779 ± 47 MPa and fracture toughness of 5.41 ± 0.29 MPa m1/2 of the ZTA cutting tools were obtained. The effects of three cutting parameters, namely the cutting speed v c , feed rate f , and back cutting depth a p , on the cutting performances of the cutting tools were investigated, and the wear mechanisms of the cutting tools were examined. We believe that our study makes a significant contribution to the literature because this study provides an in-depth investigation of the properties and wear mechanisms of ZTA ceramic cutting tools with chip breaker grooves. The findings of this study provide insight into the preparation of high-performance, complex-shaped ZTA ceramic cutting tools. Further, the preparation methods investigated in this study and the evaluation of the properties of the fabricated specimens in comparison with a commercially available cutting tool illustrate the potential advantages that may be obtained via the further development of these materials. [ABSTRACT FROM AUTHOR]

The quality characteristics of the finishing treatment of deposited materials with cutters made of hard alloy and super hard material (hexanite-R) were investigated. During finishing treatment of the deposited parts, the low roughness of the treated surface was achieved when treated with hexanite-R cutters. The roughness of the treated surface depends on feed, cutting speed, shape of the cutter tip, its wear and hardness of deposited layer. The depth of the surface hardening of the layer treated with cutters is greater than turning the weld materials of low hardness. During turning with hexanite-R cutters compressive residual stresses are formed in the surface layer, which improve the operating characteristics of parts. [ABSTRACT FROM AUTHOR]

The influence of prior pack boriding on the microstructure and properties of nanobainitised X37CrMoV5-1 hot-work tool steel was investigated in the present work. Pack boriding was conducted at 950 °C for 4 h. Nanobainitising consisted of two-step isothermal quenching at 320 °C for 1 h, followed by annealing at 260 °C for 18 h. A combination of boriding with nanobainitising constituted a new hybrid treatment. The obtained material exhibited a hard borided layer (up to 1822 ± 226 HV0.05) and a strong (rupture strength 1233 ± 41 MPa) nanobainitic core. However, the presence of a borided layer decreased mechanical properties under tensile and impact load conditions (total elongation decreased by 95% and impact toughness by 92%). Compared with borided and conventionally quenched and tempered steel, the hybrid–treated material retained higher plasticity (total elongation higher by 80%) and higher impact toughness (higher by 21%). It was found that the boriding led to the redistribution of carbon and silicon atoms between the borided layer and substrate, which could influence bainitic transformation in the transition zone. Furthermore, the thermal cycle in the boriding process also influenced the phase transformations during subsequent nanobainitising. [ABSTRACT FROM AUTHOR]

The multi-field compound polishing method based on the shear thickening has been applied to the processing of various hard materials due to its characteristics of low damage and adaptability to complex surface shapes. The surface defects on the carbide twist drill are usually produced during the grinding. This paper proposes a magnetic field-assisted shear thickening polishing (MASTP) method based on shear thickening and pumping effect, aiming to enhance surface quality of twist drill and passivate cutting edges to improve its cutting performance. The microscopic material removal mechanism of the twist drill and the rheological properties of magnetic shear thickening fluid were analyzed. The magnetic field intensity distribution in the polishing area for two types of magnetic pole arrangements is simulated. A numerical simulation was used to investigate the effect regularity of the polishing gap and spindle speed on the flow field shear stress. Experimental validation was carried out based on the processing platform. The results show the effects of processing parameters on twist drill surface roughness improvement rate and edge radius correspond to the simulated shear stress. After 60 min of polishing, the surface roughness improvement rate reached 94.7% and 80.4% at the body clearance and margin of the twist drill, respectively. The passivating radius of the major cutting edge can reach 12.92 μm, while the passivating radius of the minor cutting edge can reach 15.73 μm. At the same time, the edge defects caused by the grinding are also removed. [ABSTRACT FROM AUTHOR]

Hard and brittle materials such as monocrystalline silicon still occupy an important position in the semiconductor industry, but hard and brittle materials are difficult to process because of their physical properties. Fixed-diamond abrasive wire-saw cutting is the most widely used method for slicing hard and brittle materials. The diamond abrasive particles on the wire saw wear to a certain extent, which affects the cutting force and wafer surface quality in the cutting process. In this experiment, keeping all the given parameters unchanged, a square silicon ingot is cut repeatedly with a consolidated diamond abrasive wire saw until the wire saw breaks. The experimental results show that the cutting force decreases with the increase in cutting times in the stable grinding stage. The wear of abrasive particles starts at the edges and corners, and the macro failure mode of the wire saw is fatigue fracture. The fluctuation of the wafer surface profile gradually decreases. The surface roughness of wafer is steady during the wear steady stage, and the large damage pits on the wafer surface are reduced in the whole process of cutting. [ABSTRACT FROM AUTHOR]

MoCoB–Co cermets with different Mn contents were synthesized using an in-situ sintering reaction, and the effect of Mn addition on the microstructure, interfaces, and mechanical properties was investigated. The addition of Mn inhibited the transition of the binder phase from fcc to hcp. Adding an appropriate Mn can increase the density of the material and refine the hard phase grain. With increasing Mn content, the hardness decreased marginally and then gradually increased, and the transverse rupture strength (TRS) and fracture toughness (K IC) gradually decreased. The cermet with 6 wt% Mn addition had the smallest grain size and lower porosity. The hardness of the cermet increased from HRA 89.0 to HRA 91.7. The interface bonding strength of MoCoB/hcp-Co is higher than that of MoCoB/fcc-Co. After isothermal aging treatment, the content of hcp-Co in the binder phase increased markedly; thus, the K IC and TRS increased from 11.3 MPa m1/2 and 1200 MPa–13.3 MPa m1/2 and 1750 MPa, respectively. [ABSTRACT FROM AUTHOR]

Although ultra-precision diamond milling has been widely used for free-form machining surfaces on hard and brittle materials, there has been little research on its semi-ductile machining methods. Ultra-precision diamond milling can produce high-quality microstructured surfaces by ductile machining, but the machining efficiency is low. This study proposes a semi-ductile diamond milling method by fully considering the curvature variation of the surface, microstructure geometry characteristics, and machining parameters. Firstly, we consider the kinematic characteristics of ultra-precision diamond milling, establish the semi-ductile machining model, and also establish the relationship between machining parameters and fragmentation length. Moreover, by taking into account microstructural morphological characteristics, matching the chip thickness produced by subsequent tool rotation cycles in the feed direction with the material's critical cutting depth of ductile–brittle transition and maintaining a constant tool residual height in the step direction, and using an iterative algorithm to plan the position of the tool center of rotation during cutting, the dynamically changing tool trajectory is determined. Finally, the results of the comparison experiment between the semi-ductile diamond milling method and the conventional diamond milling method demonstrate that the sinusoidal surface machined by the SDDM has a surface roughness of only 18 nm and a consistent face shape accuracy, demonstrating the high quality and high efficiency of the method in creating microstructures on hard and brittle materials. [ABSTRACT FROM AUTHOR]

In order to meet the growing energy demand, more environmentally friendly and efficient GEN-IV reactors have emerged. Additionally, nuclear structural materials need larger more safety margins for accident scenarios as a result of the Fukushima accident. In order to extend the failure time and lessen the effect of accidents, this design method for accident-tolerant fuel materials calls for cladding materials to maintain good corrosion resistance and mechanical properties during a beyond design basis accident (BDBA). Accidents involving nuclear reactors would undoubtedly result in higher temperatures, which would make it much harder for materials to withstand corrosion. Oxide dispersion strengthened (ODS) FeCrAl alloys have shown promise as candidate materials because of their extraordinarily slow reaction rates under high-temperature steam. However, the addition of the Al element renders the alloy's high-temperature mechanical properties insufficient. In particular, studies on the alloy's creep properties are extremely rare, despite the fact that the creep properties are crucial in the real service environment. Therefore, this paper focuses on the creep properties of ODS FeCrAl alloy, summarizes and analyzes the research results of this material, and provides a reference for future research and applications. [ABSTRACT FROM AUTHOR]

The effect of a new hybrid heat treatment consisting of pack-boriding and nanobainitising on the microstructure and properties of EN 66SiMnCrMo6-6-4 bearing steel was investigated. The hybrid treatment produces a new high-strength (ca. 1480 MPa) material with a hard boride (ca. 2000 HV0.05) surface layer and a relatively ductile nanobainitic core. The formation of the boride layer significantly improves wear resistance. The boride layer, which is hard but susceptible to cracking, reduces the mechanical properties under tensile and impact loads. However, the borided and nanobainitised steel exhibits much higher tensile strength and ductility and slightly better impact toughness than steel after post-boriding quenching and tempering. [ABSTRACT FROM AUTHOR]

Amorphous boron carbide compositions having high B contents (BxC1−x, 0.50 ≤ x ≤ 0.95) are systematically created by way of ab initio molecular dynamics calculations, and their structural, electrical, and mechanical characteristics are inclusively investigated. The coordination number of both B and C atoms increases progressively with increasing B/C ratio and more close‐packed materials having pentagonal pyramid motifs form. An amorphous diamond‐like local arrangement is found to be dominant up to 65% B content, and beyond this content, a mixed state of amorphous diamond– and B‐like structures is perceived in the models because sp3 hybridization around C atoms is still leading one for all compositions. The pentagonal pyramid motifs around C atoms are anticipated to appear beyond 65% content. The intericosahedral linear C–B–C chains do not form in any model. All amorphous boron carbides are semiconducting materials. The mechanical properties gradually increase with increasing B concentration, and some amorphous compositions are proposed to be hard materials on the basis of their Vickers hardness estimation. [ABSTRACT FROM AUTHOR]

Wire electrical discharge machining (WEDM) is one of the efficient technologies of unconventional machining used to construct complex shape components, of hard materials or non-ferrous metals such as aluminum alloys. Qualitative assessment of wire electrical discharge machining (WEDM) of 2017T451 and 7075T651 aluminum alloys in terms of surface finish is studied. Three-factor and 3-level WEDM trials are operated by an L9 Taguchi's orthogonal array to determine the influence of process parameters. Based on surface roughness (Ra) value, the signal-to-noise (S/N) ratio and analysis of variance (ANOVA) results reveal that the pulse on time (TON) and pulse off time (TOFF) are significant cutting parameters affecting the surface roughness (Ra). Surface topography of the treated materials shows that no cracks for the two aluminum alloys are considered in this work. [ABSTRACT FROM AUTHOR]

With the goal of substituting a hard metallic material for the soft Ultra High Molecular Weight Polyethylene (UHMWPE) presently used to make the bases of skis for alpine skiing, we used two non-thermodynamic equilibrium surface treatments with ultra-short (7–8 ps) laser pulses to modify the surface of square plates (50 × 50 mm2) made of austenitic stainless steel AISI 301H. By irradiating with linearly polarized pulses, we obtained Laser Induced Periodic Surface Structures (LIPSS). By laser machining, we produced a laser engraving on the surface. Both treatments produce a surface pattern parallel to one side of the sample. For both treatments, we measured with a dedicated snow tribometer the friction coefficient µ on compacted snow at different temperatures (−10 °C; −5 °C; −3 °C) for a gliding speed range between 1 and 6.1 ms−1. We compared the obtained µ values with those of untreated AISI 301H plates and of stone grinded, waxed UHMWPE plates. At the highest temperature (−3 °C), near the snow melting point, untreated AISI 301H shows the largest µ value (0.09), much higher than that of UHMWPE (0.04). Laser treatments on AISI 301H gave lower µ values approaching UHMWPE. We studied how the surface pattern disposition, with respect to the gliding direction of the sample on snow, affects the µ trend. For LIPSS with pattern, orientation perpendicular to the gliding direction on snow µ (0.05) is comparable with that of UHMWPE. We performed field tests on snow at high temperature (from −0.5 to 0 °C) using full-size skis equipped with bases made of the same materials used for the laboratory tests. We observed a moderate difference in performance between the untreated and the LIPSS treated bases; both performed worse than UHMWPE. Waxing improved the performance of all bases, especially LIPSS treated. [ABSTRACT FROM AUTHOR]

Biomass-derived hard carbon materials are considered as the most promising anode materials for sodium-ion batteries (SIBs) due to their abundant sources, environmental friendliness, and excellent electrochemical performance. Although much research exists on the effect of pyrolysis temperature on the microstructure of hard carbon materials, there are few reports that focus on the development of pore structure during the pyrolysis process. In this study, corncob is used as the raw material to synthesize hard carbon at a pyrolysis temperature of 1000~1600 °C, and their interrelationationship between pyrolysis temperature, microstructure and sodium storage properties are systematically studied. With the pyrolysis temperature increasing from 1000 °C to 1400 °C, the number of graphite microcrystal layers increases, the long-range order degree rises, and the pore structure shows a larger size and wide distribution. The specific capacity, the initial coulomb efficiency, and the rate performance of hard carbon materials improve simultaneously. However, as the pyrolysis temperature rises further to 1600 °C, the graphite-like layer begins to curl, and the number of graphite microcrystal layers reduces. In return, the electrochemical performance of the hard carbon material decreases. This model of pyrolysis temperatures–microstructure–sodium storage properties will provide a theoretical basis for the research and application of biomass hard carbon materials in SIBs. [ABSTRACT FROM AUTHOR]

A sulfur doping strategy has been frequently used to improve the sodium storage specific capacity and rate capacity of hard carbon. However, some hard carbon materials have difficulty in preventing the shuttling effect of electrochemical products of sulfur molecules stored in the porous structure of hard carbon, resulting in the poor cycling stability of electrode materials. Here, a multifunctional coating is introduced to comprehensively improve the sodium storage performance of a sulfur-containing carbon-based anode. The physical barrier effect and chemical anchoring effect contributed by the abundant C-S/C-N polarized covalent bond of the N, S-codoped coating (NSC) combine to protect SGCS@NSC from the shuttling effect of soluble polysulfide intermediates. Additionally, the NSC layer can encapsulate the highly dispersed carbon spheres inside a cross-linked three-dimensional conductive network, improving the electrochemical kinetic of the SGCS@NSC electrode. Benefiting from the multifunctional coating, SGCS@NSC exhibits a high capacity of 609 mAh g−1 at 0.1 A g−1 and 249 mAh g−1 at 6.4 A g−1. Furthermore, the capacity retention of SGCS@NSC is 17.6% higher than that of the uncoated one after 200 cycles at 0.5 A g−1. [ABSTRACT FROM AUTHOR]

Crack propagation is critical in determining the surface forming process and machined surface quality of hard brittle materials. However, there is still a lack of research on this subject. In this work, the effect of crack propagation on the surface formation mechanism and surface morphology of silicon nitride ceramics was investigated via longitudinal–torsional composite ultrasonic-assisted mill grinding, and a reconstruction model of the machined surface morphology considering crack propagation was proposed. This model was quantitatively characterized and evaluated by the average roughness Sa and the kurtosis Sku. It was found that the simulation results considering crack expansion are in good agreement with the experimental results. The average relative errors in the average roughness and kurtosis were found to be 7.95% and 9.46%, respectively. A primary effect analysis was performed to understand the influence of the process parameters on the machined surface morphology. It was found that ultrasonic vibrations lead to changes in the shear angle and shear velocity of abrasive grains, thereby changing the machined surface morphology. The results presented here provide a practical method for predicting and controlling the machined surface quality during precision machining of ceramic materials. [ABSTRACT FROM AUTHOR]

In order to realize plastic processing in the continuous-wave laser-assisted machining (LAM) of SiC ceramics, the thermal effect of the laser and the influence of preheating the surface morphology and the laser power on the roughness of the machined surface are investigated. A three-dimensional transient heat transfer model is established and confirmed to be accurate with a maximum error in the surface reference temperature of 10.8%. Furthermore, the oxidation and ablation behavior of the SiC ceramics is investigated via temperature field simulations and laser preheating experiments to determine the critical temperature (1650 °C) for ablation of the machined surface. The most suitable cutting depth is then determined to be between the ablation depth and the softening depth. The surface morphology of the machined surface is also investigated by varying the laser power to determine the three processing states and corresponding laser power ranges, namely, brittleness (0–185 W), plasticity (185–225 W), and thermal damage (> 225 W). The surface roughness first decreases and then increases, and the corresponding maximum (1.298 μm) and minimum (0.45 μm) values are obtained at a laser power of 0 and 215 W, respectively. The plastic turning of SiC ceramics provides theoretical guidance for the turning of other hard and brittle materials. [ABSTRACT FROM AUTHOR]

Rare-earth permanent magnets are coated in order to avoid corrosion. When considering the rated geometrical properties of a sample, the coating thickness has to be known precisely as it wrongly enlarges the magnetically active volume which in turn affects the accuracy of the measured magnetic properties. In this work, the sensitivity of hard magnetic material property measurements regarding the consideration of different coating thicknesses is evaluated. Moreover, the impact of eddy current effects on the magnetic properties is studied when measuring in an open circuit. Additionally, an outlook for a measurement-based determination of the electric conductivity of permanent magnet samples is given. [ABSTRACT FROM AUTHOR]