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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]

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]

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]

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]

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]

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]

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]

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]

Nature fabricates hard functional materials from soft organic scaffolds that are mineralized. To enable an energy‐efficient locomotion of these creatures while maintaining their structural stability, nature often renders parts of these minerals porous. Unfortunately, methods to produce synthetic minerals with a similar degree of control over their multi length scale porous structure remain elusive. This level of control, however, would be required to design lightweight yet robust biominerals. Here, a room temperature process is presented that combines a localized mineralization with emulsion‐based 3D printing to form cm sized biominerals possessing pores whose diameters range from the 100 s of nm up to the mm length scale. The samples encompass up to 80 wt% of CaCO3 and display a specific compressive strength that is significantly higher than that of previously reported 3D printed porous biominerals and close to those of trabecular bones. The universality of this approach by forming different types of bioactive minerals, including calcite, aragonite, and brushite is demonstrated. The ability to 3D print these materials under benign conditions renders this energy‐efficient process well‐suited to construct cm‐sized lightweight yet load‐bearing structures that might find applications, for example, in the design of the next generation of flying or motile objects. [ABSTRACT FROM AUTHOR]

Micro‐optical components exhibit significant potential applications in various fields such as imaging, optical fiber communication, and aerospace owing to their small size, light weight, and flexible design. It is imperative to fabricate micro‐optical components on hard brittle materials to improve stability and broaden the optical transmission range. Therefore, femtosecond laser processing technology is demonstrated to be an efficient processing strategy for preparing refractive/diffractive micro‐optical components on hard brittle materials compared to other established micromachining techniques. This study reviews recent advances in refractive/diffractive micro‐optical components using femtosecond laser processing technologies. The applications of refractive/diffractive micro‐optical components with high accuracy, efficiency, and quality in the fields of imaging, sensing, display, and integration are also summarized. Moreover, the challenges of femtosecond laser processing technologies and the outlook of micro‐optical components are highlighted. [ABSTRACT FROM AUTHOR]

The excellent characteristics of transparent hard materials such as high hardness, high transparency, corrosion resistance, and high temperature resistance enable their applications in microfluidic substrates even in harsh environments. Microchannels are important parts in microfluidic systems, and the preparation of microchannel structures in transparent hard materials deserves further in‐depth study. The traditional processing method is contact processing with large thermal influence and low processing efficiency, so it is impossible to obtain complex microchannels with high quality and high aspect ratio. The femtosecond laser processing is a non‐contact processing approach with no thermal damage, high processing accuracy, and easy to form complex microchannels, making it the best choice for processing microchannels in transparent hard materials. This work reviews the recent advances in femtosecond laser processing of transparent hard materials to form microchannel structures, focusing on the reaction mechanism, processing methods, and the obtained microchannel structures, including surface microchannels, 2D microchannels, and 3D microchannels. Furthermore, the application of microchannel structure in microfluidic field, including optical inspection and biochemical reaction, is also described. [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]

The advancements in medical treatment necessitated the development of advanced bio‐implant materials for hard tissue replacement and bone regeneration. Hydroxyapatite (HA), an extreme bioresorbable material having physicochemical similarities with natural bone, seems to be a good bioimplant. Still, the ineffective mechanical properties, viz. fracture toughness, wear resistance, and tensile strength, restrict its practical utility in bioimplants. Recently, graphene‐HA nanocomposites have been explored for potential bioimplant applications ascribed to their superior biocompatibility, bioactivity, osteoconductivity, and enhanced mechanical properties. The huge surface area with a two‐dimensional sheet structure facilitates graphene's strong integration with HA, thus enhancing mechanical properties. These enhanced mechanical properties of graphene‐HA nanocomposite are chiefly attributed to the pull‐out, ridge growth, crack deflection, and grain bridging characteristics exhibited by graphene filler in the HA matrix. Further, graphene is neutral and biocompatible, thus improving the graphene‐HA nanocomposite's biocompatibility. These qualities made this nanocomposite a rising star among bio‐ceramic implant materials. This review presents the current scenario on the synthesis and mechanical and biological properties of graphene‐hydroxyapatite nanocomposite, which seems to be a propitious material for implants in orthopaedic applications. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is one of the hardest known materials. Its exceptional mechanical properties combined with its high thermal conductivity make it a very attractive material for a variety of technological applications. Recently, it is discovered that two‐layer epitaxial graphene films on SiC can undergo a pressure activated phase transition into a sp3 diamene structure at room temperature. Here, it is shown that epitaxial graphene films grown on SiC can increase the hardness of SiC up to 100% at low loads (up to 900 µN), and up to 30% at high loads (10 mN). By using a Berkovich diamond indenter and nanoindentation experiments, it is demonstrated that the 30% increase in hardness is present even for indentations depths of 175 nm, almost three hundred times larger than the graphene film thickness. The experiments also show that the yield point of SiC increases up to 77% when the SiC surface is coated with epitaxial graphene. These improved mechanical properties are explained with the formation of diamene under the indenter's pressure. [ABSTRACT FROM AUTHOR]

In seismology, the rupture mechanisms of an earthquake, a glacier stick‐slip and a landslide are not directly observed, but inferred from surface measurements. In contrast, laboratory experiments can illuminate near field effects. The near field reflects the rupture mechanism but is highly attenuated in the case of real‐world surface data. We directly image the elastic wave‐field of a nucleating rupture non‐invasively in its near‐field with ultrasound speckle correlation. Our imaging yields the particle velocity of the full shear wave field at the source location and inside the 3D frictional body. We experimentally show that a strong bimaterial contrast, as encountered in environmental seismology, yields a unidirectional or linear force mechanism for pre‐rupture microslips and decelerating supershear ruptures. A weak contrast, characteristic for earthquakes, generates a double‐couple source mechanism for sub‐Rayleigh ruptures, sometimes preceded by slow deformation at the interface. This deformation is reproduced by the NF of a unidirectional force. Plain Language Summary: Earthquakes, avalanches, icequakes and landslides originate from a common process: rupture at a material interface. During a rupture, for example, when a landslide slips, a characteristic pattern of seismic waves is created. This pattern differs at the earth's surface and the rupture interface, which is the source of the seismic waves inside the earth. Usually scientists only measure the waves arriving at the surface and need to deduce the wave pattern inside the earth from the surface measurement. We build a laboratory experiment which enables us to film wave propagation around the rupture surface, as if we had a camera inside the material. We film waves emitted during and prior to a rupture. For a soft material on a hard surface, such as encountered in icequakes or landslides, a single force model better explains the observed wave pattern than the commonly used model of four distributed forces. The rupture moves faster than shear waves propagate which results in a supershear cone, the elastic equivalent to the acoustic Mach cone created by supersonic aircrafts. For two materials of similar hardness, such as encountered in earthquakes, the classic model of four forces better explains the ruptures, which travel at sub‐shear speed. Key Points: Noninvasive elastic near‐field laboratory observations reveal source mechanisms of micro‐slips, supershear and sub‐Rayleigh rupturesStrong material contrasts as encountered in glacier stick‐slip and landslides cause single force micro‐slips and supershear rupturesWeak contrasts, which are found in natural faults, show a double‐couple mechanism that is at times preceded by a slowly rising single force [ABSTRACT FROM AUTHOR]

The magnetization of cobalt ferrite nanocubes of similar size, but with varying Co/Fe ratio, is extensively characterized on atomistic and nanoscopic length scales. Combination of X‐ray diffraction, Mössbauer spectroscopy, magnetization measurements and polarized small‐angle neutron scattering (SANS) reveals that a lower amount of cobalt leads to an enhanced magnetization. At the same time, magnetic SANS confirms no or negligible near‐surface spin disorder in these highly crystalline, homogeneously magnetized nanoparticles, resulting in an exceptionally hard magnetic material with high coercivity. [ABSTRACT FROM AUTHOR]

The industry is looking forward to technological advancements for productivity improvement, and this can be achieved by improving the machining performance concerned with the machinability challenges. The machinability investigation of carbon nanotubes/carbon fiber (CNTs/CF) reinforced composites is emerging with a strong application potential in the aviation industry because of their high strength and lightweight nature. However, the conventional machining practices pose a major challenge of excessive tool wear and dimensional accuracy which lead to a high production cost. Electric discharge machining is considered one of the possible solutions to treat with hard to machine materials like CNT/CF. Therefore, this work involves the machinability investigation to study the effect of pulse on duration, pulse peak current, duty factor, and gap voltage to investigate the material removal mechanism for achieving machining stability along with improved dimensional accuracy. Experiments were designed using Taguchi design followed by the analysis of variance, parametric effects, along with signal to noise ratio‐based multi‐response optimization. Findings have inferred that peak current and gap voltage were found to be significant for radial over‐cut, contributing 47.27% and 40.25%, respectively. The gap voltage was also shown to be notable for electrode wear rate and material removal rate, with contribution percentages of 43.59% and 20.11%, respectively. As a result, Vg was identified as the most influential variable in this study. This machinability study imparts a significant potential to improve the dimensional accuracy and productivity for aerospace applications. [ABSTRACT FROM AUTHOR]

A metallic, covalently bonded carbon allotrope is predicted via first principles calculations. It is composed of an sp3 carbon framework that acts as a diamond anvil cell by constraining the distance between parallel cis‐polyacetylene chains. The distance between these sp2 carbon atoms renders the phase metallic, and yields two well‐nested nearly parallel bands that cross the Fermi level. Calculations show this phase is a conventional superconductor, with the motions of the sp2 carbons being key contributors to the electron–phonon coupling. The sp3 carbon atoms impart superior mechanical properties, with a predicted Vickers hardness of 48 GPa. This phase, metastable at ambient conditions, could be made by on‐surface polymerization of graphene nanoribbons, followed by pressurization of the resulting 2D sheets. A family of multifunctional materials with tunable superconducting and mechanical properties could be derived from this phase by varying the sp2 versus sp3 carbon content, and by doping. [ABSTRACT FROM AUTHOR]

A metallic, covalently bonded carbon allotrope is predicted via first principles calculations. It is composed of an sp3 carbon framework that acts as a diamond anvil cell by constraining the distance between parallel cis‐polyacetylene chains. The distance between these sp2 carbon atoms renders the phase metallic, and yields two well‐nested nearly parallel bands that cross the Fermi level. Calculations show this phase is a conventional superconductor, with the motions of the sp2 carbons being key contributors to the electron–phonon coupling. The sp3 carbon atoms impart superior mechanical properties, with a predicted Vickers hardness of 48 GPa. This phase, metastable at ambient conditions, could be made by on‐surface polymerization of graphene nanoribbons, followed by pressurization of the resulting 2D sheets. A family of multifunctional materials with tunable superconducting and mechanical properties could be derived from this phase by varying the sp2 versus sp3 carbon content, and by doping. [ABSTRACT FROM AUTHOR]

A nominally pure and dense (Ti0.9Cr0.1)B2 ceramic was produced by spark plasma sintering of powders synthesized by boro/carbothermal reduction of oxides. The synthesized powders were a single phase and had an average particle of 0.4 ± 0.1 μm and an oxygen content of 1.2 wt%. Average Vickers hardness values of the resulting ceramics increased from 25.9 ± 0.8 GPa at a load of 9.81 N, to 46.3 ± 0.8 GPa at a load of 0.49 N. Compared to the nominally pure TiB2 ceramic obtained under the same processing conditions, the (Ti0.9Cr0.1)B2 ceramic had higher values under the same load due to the finer average grain size (2.4 ± 1.0 μm), higher relative density, and solid solution hardening. The results indicated that the Cr addition promoted densification, suppressed grain growth, and improved the hardness of TiB2 ceramics. This is the first report for dense and single‐phase (Ti,Cr)B2 ceramics as superhard materials. [ABSTRACT FROM AUTHOR]

Amorphous and low‐crystallinity thermoplastic polyurethane elastomers are shot back and forth between two elongation levels (ε=0.2$\epsilon =0.2$ and ε=1.2$\epsilon =1.2$) and observed between the excitations for 10 s using wide‐angle X‐ray scattering (WAXS) (50 Hz). For orientation analysis, the fiber patterns are projected, expanded in multipoles, and discussed as a function of relaxation time. Normalized WAXS suggests that the oriented halo observed during extension is predominantly due to selective extinction of unfavorably oriented probes (chain bundles). During retraction, neighborhoods and thus clusters are restored. Discussed are the relaxation curves depending on material and the number of load cycles. The separation of the halo into narrow rings introduces "bundle airiness" as a second coordinate. The now bivariate cluster density is the product of two univariate functions. Its factor "airiness distribution" seems to be a material property which is not changed by annealing. In contrast, the bivariate preferred orientation is not product‐separable. Especially with harder materials it shows two bundle ensembles of different airiness. Interactions between the ensembles explain complex trajectories of the orientation–relaxation curves. The formation of the additional airier oriented component is inhibited by annealing in most of the materials studied. In contrast, multiple load changes promote its formation. [ABSTRACT FROM AUTHOR]

Hard carbon has the potential to serve as a high‐capacity anode material for sodium‐ion batteries (SIBs), however, its Na+ storage mechanism, particularly on the low potential plateau, remains controversial. To overcome this issue, two types of hard carbons with different microstructures are employed and the relationship between the microstructures and Na+ storage behaviors is evaluated. By the combination of operando X‐ray diffraction, ex situ Raman spectroscopy, NMR, and theoretical calculation, it is found that the sodium storage capacities of the hard carbons in the low potential plateau region contain the concurrent contributions from both interlayer intercalation and micropores filling, and the ratio of the two contributors greatly depends on the microstructure of hard carbon materials. Moreover, an electrochemical pointer (potential inflection point at the end of the discharge curve) is found to distinguish the dominance of interlayer intercalation and the micropores filling processes of sodium ions in the low potential plateau region. Based on this new finding, a microstructure‐dependent mechanism ("adsorption‐intercalation/filling" hybrid mechanism) is proposed to achieve an overall understanding of the sodium storage behaviors in different hard carbon materials, which may provide deep insight into the rational design of hard carbon structures as high‐performance anode materials for advanced SIBs. [ABSTRACT FROM AUTHOR]

Superhard materials are indispensable for use in cutting and polishing, as well as for nuclear reactor construction. As a candidate for hard material, ZrC has been extensively studied but not in its pressurized phase. Through evolutionary algorithm and density functional theory, we narrowed down the stoichiometry of Zr and C elements at various elevated pressures. The semimetal property of Zr4C4 continues to exist at high pressures but with lower electrical conductivity. Ionic and covalent bonding coexist around the pseudogap for high pressure phases. Both elastic constants and elastic moduli are found to increase steadily with surrounding pressure, connoting the superior mechanical and thermal characteristics of Zr4C4. This can be seen in the increased hardness values, higher melting temperatures, and better machinability indices for Zr4C4 as pressure rises. The predicted G/B and Poison's ratios have both agreed that Zr4C4 exhibits a transition from brittle to ductile behavior when the applied pressure goes above 85 GPa, displaying an overall improved mechanical performance. [ABSTRACT FROM AUTHOR]

In comparative life cycle assessment (LCA) studies of materials, there is a mismatch between the current practice and existing guidelines regarding functional unit definition. The purpose of this study is to develop a practice‐based framework for defining functional units in comparative LCAs of materials and provide guidance regarding in which situations different functional unit types are relevant. A literature review of comparative LCAs of materials identified three types of functional units: (i) the reference flow functional unit, (ii) the property functional unit, and (iii) the performance functional unit. These functional unit types, of which only the latter strictly complies with LCA guidelines, represent varying degrees of functional equivalence and technological maturity. The most relevant functional unit type depends on the goal of the study. We suggest that screening assessments of whether materials have comparable environmental impacts can apply reference flow functional units. Material comparisons for certain application areas with some important properties can apply property functional units. For comparisons of end products, performance functional units can be applied. However, even in such cases, complete functional equivalence can hardly be achieved due to more or less relevant product differences. The applicability of the framework is demonstrated for the case of comparing cemented carbide and polycrystalline diamond hard materials. [ABSTRACT FROM AUTHOR]

Changes in the global bulk and local structures, of three different barium compounds (BaZrO3, BaF2, and BaFCl),were induced by mechanical milling and followed using X‐ray powder diffraction (PXRD), subsequent microstructure analysis, and 137Ba solid state NMR spectroscopy. Harder materials like BaZrO3 experience significantly higher structural changes upon milling than softer materials like BaF2. Moreover, soft materials with layered structures, like BaFCl, show a pronounced structural change during the milling process. By combining PXRD and solid state NMR, detailed information on the changes to the global and local structures were obtained, which are of interest for mechanochemical synthesis, mechanically treated catalysts or ionic conductors. [ABSTRACT FROM AUTHOR]

The design and fabrication of novel hard materials with excellent electrical conductivity is attractive in scientific and technological application under extreme conditions. Metal borides have brought substantial interest for decades in material science because of their strong covalent BB bonding network for intrinsic incompressibility and MM bonding for electron transportation. Here the successful synthesis of a novel hard alkali metal boride as NaB4 with high thermal stability (873 K) and metallic behaviors is reported. The relatively low synthetic P/T conditions (lowest at 1.5 GPa and 1000 K) enable the easy fabrication of large bulk materials (several centimeters in diameter). The studies reveal that the Vickers hardness value of NaB4 can reach up to 26 GPa, associated with superior incompressibility along (001) direction of honeycomb‐like boron structure that exhibits the highest shear modulus up to 96 GPa for borides. The NaB4 structure undergoes an interesting metallic‐semiconducting transition under compression up to 61 GPa. This new form of hard metal boride material with pressure‐tunable electrical properties enables the development of industrial applications as future electrical devices. [ABSTRACT FROM AUTHOR]

1D cylindrical magnetic nanostructures (FeNi, FeCo, FeCoP) of complex topology such as nanowires (NWs), nanotubes (NTs), multilayered nanowires, and core–shell structures are discussed from the perspective of engineering a wide variety of magnetic materials from hard to semihard to soft. Most of recent data are given for the materials synthesized in the pores of polymer ion‐track membranes, which makes it possible to tune systematically the geometrical parameters, morphology, and composition. The key properties including crystal and micromagnetic structure, magnetic anisotropy, and coercivity are analyzed. Co‐based NWs with uniform morphology demonstrate coercivity of more than 10 kOe due to the combination of crystalline and shape anisotropies. In the case of NTs, the demagnetizing effect is reduced owing to a helical arrangement of the magnetization, which leads to low values of coercivity and remanence magnetization. Varying the geometrical parameters of multilayered NWs, the alternating soft and semihard magnetic layers can be made within a single nanowire, which is important for spin‐valve magnetoresistance. Au‐coated ferromagnetic nanostructures are biocompatible and can be used to enhance optical absorption. Ni@Au NTs used as substrates for Raman spectroscopy demonstrate the enhancement factor of the order of 104. Some aspects related to applications of 1D magnets are briefly overviewed. [ABSTRACT FROM AUTHOR]

Nanoskiving is a unique nanomanufacturing method that can be used to cut out nanostructures directly with well‐controlled shapes and sizes. Over the past 10 years, nanoskiving techniques have evolved in terms of optimization of the sectioning parameters and development of the transfer and alignment approaches. In addition, the range of compatible materials for nanoskiving is expanding via combination of the technique with other bottom–up and top–down methods; for example, soft materials such as block polymers and hard materials such as cemented carbide and semiconductor materials are now able to be nanosized successfully, despite previously being considered incompatible with nanoskiving technology. The preparation of these structures by the nanoskiving method opens a convenient door to verification of the application of this technique to device miniaturization in fields including optics, electrochemistry, electronics, and biology. This review outlines the advances made in nanoskiving, including those in the fabrication process, the development of suitable applications, and the challenges and opportunities for future exploration of the technology. [ABSTRACT FROM AUTHOR]

The Poynting effect generically manifests itself as the extension of the material in the direction perpendicular to an applied shear deformation (torsion) and is a material parameter hard to design. Unlike isotropic solids, in designed structures, peculiar couplings between shear and normal deformations can be achieved and exploited for practical applications. Here, a metamaterial is engineered that can be programmed to contract or extend under torsion and undergo nonlinear twist under compression. First, it is shown that the system exhibits a novel type of inverted Poynting effect, where axial compression induces a nonlinear torsion. Then the Poynting modulus of the structure is programmed from initial negative values to zero and positive values via a pre‐compression applied prior to torsion. The work opens avenues for programming nonlinear elastic moduli of materials and tuning the couplings between shear and normal responses by rational design. Obtaining inverted and programmable Poynting effects in metamaterials inspires diverse applications from designing machine materials, soft robots, and actuators to engineering biological tissues, implants, and prosthetic devices functioning under compression and torsion. [ABSTRACT FROM AUTHOR]

Carbonaceous materials have been accepted as a promising family of anode materials for lithium‐ion batteries (LIBs) owing to optimal overall performance. Among various emerging carbonaceous anode materials, hard carbons have recently gained significant attention for high‐energy LIBs. The most attractive features of hard carbons are the enriched microcrystalline structure, which not only benefits the uptake of more Li+ ions but also facilitates the Li+ ions intercalation and deintercalation. However, the booming application of hard carbons is significantly slowed by the low initial Coulombic efficiency, large initial irreversible capacity, and voltage hysteresis. Many efforts have been devoted to address these challenges toward practical applications. This paper focuses on an up‐to‐date overview of hard carbons, with an emphasis on the lithium storage fundamentals and material classification of hard carbons as well as present challenges and potential solutions. The future prospects and perspectives on hard carbons to enable practical application in next‐generation batteries are also highlighted. [ABSTRACT FROM AUTHOR]

Tungsten monocarbide (WC) is one of the highly valuable hard materials for industry, widely used as reinforcement in hardfacing overlays, thermal spray coatings, composites, and various alloys. However, its large density leads to the inhomogeneous distribution of WC particles in the metal‐matrix hardfacing overlays. It is highly wished to have appropriate reinforcing phases with an optimal combination of high strength, compatible density, and physical properties. In this study, we tailored WC by partially substituting W with 3d and 4d transition metals through first‐principles calculations. It is demonstrated that WC can be tailored by element‐substitution with desired properties. Identified stable (W1‐x,Mx)C carbides possess lowered density and mechanical properties that are comparable to those of WC. Physical properties, for example, the Debye temperature, Grüneisen parameter, and thermal conductivity, of the tailored carbides are also studied for widened applications. Efforts are made to generate comprehensive information on metal‐substituted (W1‐x,Mx)C with elucidated underlying mechanisms through analyzing the corresponding electronic characteristics. [ABSTRACT FROM AUTHOR]

Hyperbolic metamaterials (HMMs) are highly anisotropic optical materials that behave as metals or as dielectrics depending on the direction of propagation of light. They are becoming essential for a plethora of applications, ranging from aerospace to automotive, from wireless to medical and IoT. These applications often work in harsh environments or may sustain remarkable external stresses. This calls for materials that show enhanced optical properties as well as tailorable mechanical properties. Depending on their specific use, both hard and ultrasoft materials can be required, although the combination with optical hyperbolic response is rarely addressed. Here, the possibility to combine optical hyperbolicity and tunable mechanical properties in the same (meta)material is demonstrated, focusing on the case of extreme mechanical hardness. Using high‐throughput calculations from first principles and effective medium theory, a large class of layered materials with hyperbolic optical activity in the near‐IR and visible range is explored, and a reduced number of ultrasoft and hard HMMs is identified among more than 1800 combinations of transition metal rocksalt crystals. Once validated by the experiments, this new class of metamaterials may foster previously unexplored optical/mechanical applications. [ABSTRACT FROM AUTHOR]

Summary: This article discusses four applications for ultraviolet light: material inspection and characterization, plasma characterization, solar physics, and crystallography, and how each of the UV‐ subcategories (near, mid, far and extreme UV) can be utilized to determine different properties within each application. This article also touches on the specific technology required for each of these applications, and subsequently each wavelength subcategory within that. [ABSTRACT FROM AUTHOR]

As hard and brittle materials are widely used in the modern industry, it is essential to effectively achieve uniform material removal. In the present study, a contact stress prediction model for double‐layer elastomer under uniform displacement load was proposed. It aims to predict the contact stress distribution based on the structure size and material parameters of the double‐layer elastomer and optimize the relevant parameters to improve the uniformity of material removal. The functionally graded and composite structured lapping and polishing plate (FG/CS‐LPP) was developed by mixing abrasive particles and rubber with different mass ratios to get different Young's moduli. Through optical microscope, the surface morphology was observed, and the mechanism of Young's modulus gradient change was demonstrated. After numerical simulation analysis, the effect of Young's modulus fluctuation on contact stress distribution trend was evaluated. As for the contact stress prediction model, an equivalent Young's modulus model and compensation function H(z) was introduced to simplify the analytical process. Further, the obtained equivalent equation was verified by simulations and experiments with an average percentage deviation of ~2% and ~6%, respectively. By fitting calculated and simulated values with a deviation of less than 5%, the compensation function H(z) was established. Finally, the contact stress prediction model was obtained and validated by simulations and experiments, the percentage deviation is less than 13%. Accordingly, the contact stress prediction model can provide a theoretical basis for FG/CS‐LPP to achieve uniform material removal. [ABSTRACT FROM AUTHOR]

In this contribution, a soft sensor configuration based on silicone foam is developed to measure compressive forces in the range of 50 N with the aim of providing proprioceptive capabilities to conventional robotic manipulators based on hard materials. This then makes them capable of interacting with soft and fragile objects without damage. The concept relies on interdigitated electrodes that are patterned on the backside of the sensor to generate a fringing electric field into a soft compressible polymeric foam. The deformation of the foam causes changes to relative permittivity as the air‐filled cells compress. The model in this article shows how the different parameters of the foam, such as air volume fraction, permittivity, and Young's modulus, affect the stiffness and electrical sensitivity of the sensor, and how controlling the porosity of the foam is key to optimizing the sensitivity of the sensor. This sensor is easy to fabricate and does not require compliant electrodes, while exhibiting high sensitivity values of 33% capacitance change for as little as 10 N applied force. [ABSTRACT FROM AUTHOR]

In this special issue, we believe it is a good opportunity to summarize nanoceramics in depth. This special issue highlights the papers of speakers at the International Symposium on Novel and Nano Materials 2022 (ISNNM 2022). The symposium provided the latest research results and state-of-the-art overview of technology in the exciting and rapidly evolving fields of nanomaterials. [Extracted from the article]

Hard and brittle solids with covalent/ionic bonding are used in a wide range of modern‐day manufacturing technologies. Optimization of a shaping process can shorten manufacturing time and cost of component production, and at the same time extend component longevity. The same process can contribute to wear and fatigue degradation in service. Educated development of advanced finishing protocols for this class of solids requires a comprehensive understanding of damage mechanisms at small‐scale contacts from a materials perspective. The basic science of attendant deformation and removal modes in contact events is here analyzed and discussed in the context of brittle and ductile machining and severe and mild wear. Essentials of brittle–ductile transitions in micro‐ and nano‐indentation fields are outlined, with distinctions between blunt and sharp contacts and axial and sliding loading. The central role of microstructure in material removal modes is highlighted. Pathways to future research—experimental, analytical, and computational—are indicated. [ABSTRACT FROM AUTHOR]

This study presents the design of a 2‐pole high‐speed BLDC motor for kitchen blenders and its control method with the aim to reduce the speed ripple that decreases the grinding performance in the high‐speed region. In blender machines, the high pulsating load caused by the blending materials such as ice cubes acting on the grinding blade, create significant speed ripple in the constant power region. Because current and torque are limited to protect the drive, the actual motor torque cannot overcome the pulsated load if the speed reference is maintained. Therefore, the speed fluctuates, and the grinding performance is lowered. In the proposed variable speed reference control scheme, the speed command is continuously modified to overcome the maximum pulsating torque requirement which results in lower speed ripple. To achieve this, if the load torque suddenly increases, the current value is then set based on the maximum load and speed reference value is temporarily lowered. If then the load torque becomes lower than the actual torque, the previously set speed reference value is reused. The design result and grinding performance of the proposed control method are verified by simulations and experiments. Hard white beans are used for actual performance testing. [ABSTRACT FROM AUTHOR]

Indentation fracture models of ductile machining in hard and brittle materials are critically appraised. Relations obtained in a seminal study for critical depths of cut below which fracture is suppressed are examined and amended. Limitations inherent in any such materials‐based analysis, in addition to uncertainties in empirical measurements of underpinning mechanical properties (modulus, hardness, toughness) and of threshold grinding depths, suggest that caution should be exercised in unconditional usage. Notwithstanding these limitations, the value of the indentation fracture methodology in placing ductile machining on a sound materials science footing is maintained. [ABSTRACT FROM AUTHOR]

The recent theoretical prediction of a new compound, WB5, has spurred the interest in tungsten borides and their possible implementation in industry. In this research, the experimental synthesis and structural description of a boron‐rich tungsten boride and measurements of its mechanical properties are performed. The ab initio calculations of the structural energies corresponding to different local structures make it possible to formulate the rules determining the likely local motifs in the disordered versions of the WB5 structure, all of which involve boron deficit. The generated disordered WB4.18 and WB4.86 models both perfectly match the experimental data, but the former is the most energetically preferable. The precise crystal structure, elastic constants, hardness, and fracture toughness of this phase are calculated, and these results agree with the experimental findings. Because of the compositional and structural similarity with predicted WB5, this phase is denoted as WB5−x. Previously incorrectly referred to as "WB4," it is distinct from earlier theoretically suggested WB4, a phase with a different crystal structure that has not yet been synthesized and is predicted to be thermodynamically stable at pressures above 1 GPa. Mild synthesis conditions (enabling a scalable synthesis) and excellent mechanical properties make WB5−x a very promising material for drilling technology. [ABSTRACT FROM AUTHOR]

Human skin plays an important role in hand manipulation by making a stable grasp with an enlarging contact area while providing a firm hold on the object. However, satisfying these two functions is contradictory in conventional single‐layer artificial skin. Softer skin material would increase the contact area, which is advantageous in maintaining the stability, but it decreases the manipulability since the object tends to make uncontrollable movement within the softer skin, and vice versa for harder skin material. This paper presents a biomimetic three‐layer skin structure inspired by human palm skin and shows that both stability and manipulability can be enhanced with the three‐layer structure. To achieve the unique stiffness characteristics of the human palm skin, a porous latex structure, which is highly compressible but tough in tensile direction, is chosen as the subcutaneous fat layer. Through the novel experimental setup and the finite element method simulations, it is found that the porous latex structure is the key structure contributing to both stability and manipulability. Furthermore, it is demonstrated that a robotic hand with the proposed skin material shows enhanced robustness in grasping tasks. With the proposed skin material, the robotic hands would be more advantageous for challenging manipulation tasks. [ABSTRACT FROM AUTHOR]

Summary: TiAlN‐coatings by means of high‐energy sputtering According to current knowledge, high‐energy plasmas represent a promising tribological property profile for nitride hard material coatings and their applications. However, the increased ionization rate results in a high level of residual compressive stresses in TiAlN thin films (σTiAlN ∼ –6000 MPa), which can negatively influence the adhesion between substrate and coating and thus can lead to delamination and damage. In this context, the presented investigations prove that a hybrid process consisting of the synchronous use of direct current (DC) and high power pulse sputtering (HiPIMS) can be used to reduce the residual stress state in the coating. This allows to combine the advantages of both technologies and thus to qualify TiAlN thin films for an extended range of applications as tribological coatings for heat treated tool steels. [ABSTRACT FROM AUTHOR]

Molybdenum boride is an ideal hard and wear‐resistant material. In this study, a new method is proposed for preparing molybdenum boride, by which Mo first reacts with B4C to generate the mixture of molybdenum boride and C, and then the product is decarburized by molten Ca to generate CaC2. Pure molybdenum boride could be obtained after acid leaching to remove the by‐product CaC2. According to the experimental and thermodynamic calculation results, it is concluded that the single‐phase MoB could be successfully prepared, while Mo2B, Mo2B5, and MoB4 could not be synthesized by this method. Moreover, it was found that the particle size of finally prepared MoB is determined by particle size of raw Mo powder. The residual carbon content of the product could be decreased to 0.10 wt% after first reaction at 1673 K for 6 hours and then decarburization reaction at 1673 K for 6 hours. [ABSTRACT FROM AUTHOR]

Currently, a paradigm shift of technology from 'hard and dry' to 'soft and wet' is taking place, that is, the industrial importance is moving from heavy materials and silicon semiconductors to artificial intelligence (AI) and life science. Electronic materials of hard and dry technologies are silicon and inorganic semiconductors; electrons are playing the role of functions. Of course, the materials for soft and wet are organics, and ions are working with electrons. In other words, the recent progress witnessed by ground‐breaking research in the robotics by AI and tissue engineering by induced pluripotent stem (iPS) cell made it hard to anticipate about the future social life. However, food, life‐sustaining biomaterials (hormone, virus, enzyme, etc.), and energy, which are essential for life, are constantly being improved based on existing materials and technology. Biologically active organic compounds control various life functions; therefore, a fusion of biomaterials, energy, and informatics are expected to provide an efficient novel system for our sustainable growth and development. Biological functions can be imitated by dynamic control of mass and ion transfer, including conventional electronics. The author is sure that this review article will provide key technologies in the future to solve the issues on environmental protection and energy problems for the life sustainability and the need to be organized successively. The main purpose of this review article is to provide an opportunity for researchers who are interested in organic 'iontronics', to come together in an informal and friendly atmosphere and exchange their technical information and experiences. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

We generate a tetrahedrally coordinated amorphous boron nitride (BN) model by means of first principles molecular dynamics calculations and report its mechanical and electrical properties in detail. The amorphous configuration is almost free from chemical disorder and consists of about 20% coordination defects, similar to tetrahedral (diamond‐like) amorphous carbon. Its theoretical band gap energy is about 2.0 eV, less than 4.85 eV estimated for cubic BN. The bulk modulus and Vickers hardness of tetrahedral amorphous BN are computed as 206 GPa and 28‐35 GPa, respectively. Based on these findings, we propose that tetrahedral noncrystalline BN can serve as electronic and hard materials as well. [ABSTRACT FROM AUTHOR]

The architectures of biological hard materials reveal finely tailored complex assemblies of mineral crystals. Numerous recent studies associate the design of these local assemblies with impressive macroscopic response. Reproducing such exquisite control in technical ceramics conflicts with commonly used processing methods. Here, we circumvent this issue by combining the recently developed Magnetically Assisted Slip Casting (MASC) technique with the well‐established process of templated grain growth (TGG). MASC enables the local control over the orientation of platelets dispersed among smaller isotropic particles. After a high‐temperature pressureless heat treatment, the grains of the final ceramic follow the same orientation as of the initial platelets. This combination allows us to produce 95% dense alumina part with a grain orientation following any deliberate orientation. We successfully fabricated microstructures inspired from biological materials with ceramics that present periodically varying patterns with a programmable pitch down to a few tens of micrometers. The periodically textured dense ceramics exhibit matching variation of local hardness, confirming the capacity of the process to tailor local properties. This unique micrometer scale control over the local mechanical properties could be applied to adapt ceramic structures to complex loads using this inexpensive and scalable process. In systems where functional properties also depend on anisotropic grain orientation, the principle presented here could enable the creation of new multifunctional ceramics. [ABSTRACT FROM AUTHOR]

The development of efficient and stable red and near‐IR emitting materials under hard radiation doses and/or prolonged times is a sought‐after task due to their widespread applications in optoelectronics and biophotonics. To this aim, novel symmetric all‐BODIPY‐triads, ‐pentads, and ‐hexads have been designed and synthesized as light‐harvesting arrays. These photonic materials are spectrally active in the 655–730 nm region and display high molar absorption across UV–visible region. Furthermore, they provide, to the best of our knowledge, the highest lasing efficiency (up to 68 %) and the highest photostability (tolerance >1300 GJ mol−1) in the near‐IR spectral region ever recorded under drastic pumping conditions. Additionally, the modular synthetic strategy to access the cassettes allows the systematic study of their photonic behavior related to structural factors. Collectively, the outstanding behavior of these multichromophoric photonic materials provides the keystone for engineering multifunctional systems to expedite the next generation of effective red optical materials. [ABSTRACT FROM AUTHOR]