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Ferroelectric materials are widely used in actuators, exciters, and memory devices due to their excellent electromechanical properties. However, the instinctive brittleness of ferroelectric materials makes them easy to fracture under external load. Since giant strain gradient can be easily generated near the crack tip, the flexoelectric effect is indispensable in the research of fracture properties of ferroelectric materials. With the combination of time-dependent Ginzburg–Landau theory and phase-field model, the electromechanical behavior of PbTiO 3 in the vicinity of the crack tip is determined in this work. The simulation results demonstrate that the domain structure near the crack tip becomes asymmetric with the flexoelectric effect. The polarization switching-induced toughening, which is characterized by the J -integral, depends on the direction of the crack relative to the original polarization orientation. Furthermore, the longitude flexoelectric coefficient f 11 has more significant impact on the fracture toughness than that of the transverse flexoelectric coefficient f 12 and the shear flexoelectric coefficient f 44. The results of the present work suggest that the flexoelectric effect must be considered in the reliable design of ferroelectric devices. [ABSTRACT FROM AUTHOR]

Amorphous intergranular films (AIFs) have been proven in experiments to improve the damage tolerance of nanocrystalline materials. However, a quantitative study is still lacking. Molecular dynamics simulations were performed here to investigate the effect of CuNb AIFs on the fracture toughness of nanocrystalline Nb. In order to clarify the role of AIFs, a bicrystal Nb model with one straight symmetrical tilt grain boundary and a mode-I crack in one of the grains was constructed, in which the AIF effect was introduced by replacing the normal grain boundary with a CuNb AIF. Then, AIF thickness-dependent tensile deformation of the bicrystal Nb samples was simulated. The work-of-fracture, which is defined as the released strain energy due to the newly generated unit area in the crack during stretching, was employed to quantify the fracture toughness of the bicrystal systems. The results show that the fracture toughness of the AIF sample can be tripled due to the blunted crack tip and the relieved stress concentration at the crack tip as compared to the AIF-free one that exhibits a brittle crack propagation behavior. Also, the thicker the AIFs, the more pronounced this reinforcing effect. More importantly, it is found that there exists a critical AIF width of 1.7 nm, below which the crack will eventually break through the AIF, and above which the crack failed to do this. It is revealed that the enhanced fracture toughness originated from the transformation of brittle crack propagation to abundant dislocation emission from AIFs. [ABSTRACT FROM AUTHOR]

Amorphous solids are known to fail catastrophically via fracture, and cavitation at nano-metric scales is known to play a significant role in such a failure process. Micro-alloying via inclusions is often used as a means to increase the fracture toughness of amorphous solids. Modeling such inclusions as randomly pinned particles that only move affinely and do not participate in plastic relaxations, we study how the pinning influences the process of cavitation-driven fracture in an amorphous solid. Using extensive numerical simulations and probing in the athermal quasistatic limit, we show that just by pinning a very small fraction of particles, the tensile strength is increased, and also the cavitation is delayed. Furthermore, the cavitation that is expected to be spatially heterogeneous becomes spatially homogeneous by forming a large number of small cavities instead of a dominant cavity. The observed behavior is rationalized in terms of screening of plastic activity via the pinning centers, characterized by a screening length extracted from the plastic-eigenmodes. [ABSTRACT FROM AUTHOR]

Fine-grained nuclear graphite is one of the key structural materials for high temperature gas-cooled reactors as well as several Generation IV nuclear fission reactor designs. However, its deformation and fracture behaviours at elevated temperatures are not well understood. In light of this, the current study focused on investigating the flexural strength and fracture toughness of two fine-grained graphite (SNG623 and T220) using real-time X-ray computed micro-tomography imaging at room temperature, 750 °C and 1100 °C. Specifically, nonlinear-elastic fracture mechanics-based JR(Δa) R-curves at these temperatures were presented with evolution of damage and failure micro-mechanisms, local strain distributions and J-integral fracture analysis, purveying notable findings. Compared to the coarser-grained Gilsocarbon nuclear graphites used in the current UK Advanced Gas-cooled Reactors (AGRs), these modern fine-grained graphites display deficient fracture resistance in the form of far less stable crack growth prior to catastrophic fracture and reduced failure strain at 1100 °C. Moreover, their elevation in strength and toughness at high temperatures is remarkably lower than that of Gilsocarbon graphite. Based on in situ high-temperature Raman spectroscopy mapping, we believe that one of the major causes of this behaviour can be attributed to the smaller magnitude of ‘frozen-in’ residual stress relaxed at elevated temperatures compared with Gilsocarbon graphite.

A novel (MoCrVMn) 2 FeB 2 based high-entropy cermets were prepared by two-steps method and the microstructure and mechanical properties were investigated. The single-phase (MoCrVMn) 2 FeB 2 powders were synthesized at 1400 °C for 2 h, and subsequently the (MoCrVMn) 2 FeB 2 based high-entropy cermets were prepared via pressureless sintering technique. The results revealed that the phase evolution was as follows: (Mo, Cr, V, Mn, Fe, B) → (Fe 2 B, V 2 B 3 , MoB) → ((FeVMn) 2 B, (FeVMnCr) 2 B, Mo 2 FeB 2) → (MoCrVMn) 2 FeB 2. The (MoCrVMn) 2 FeB 2 based high-entropy cermets sintered at 1250 °C showed good denseness and the ceramic phases were uniformly distributed in the metal bond, with the optimal mechanical properties of hardness 1355 HV 30 and fracture toughness 19.09 MPa m1/2. With the increase of temperature, the hardness increased first and then decreased, and the fracture toughness was basically unchanged first and then increased, and then decreased. This study provides a new route to further optimize the performance of Mo 2 FeB 2 based cermets. [ABSTRACT FROM AUTHOR]

This investigation comprehensively examines the nano - mechanical properties of AlTaO 4 for the first time, including Young's modulus (E), hardness (H), and fracture toughness (K IC). Variability in the regional distribution of E and H within AlTaO 4 is elucidated through an examination spanning both the grain and bulk material scales, and offers a correlational equation of E and H from fit statistical outcomes. Additionally, the H/E ratio and micro-hardness dissipation parameter of AlTaO 4 reach 0.063 and 0.61, respectively, which demonstrate its exceptional wear resistance. Further investigation emphasizes that the distinctive crystalline structure, short bond lengths, high bond strength, and elevated charge density around aluminum ions significantly contribute to the high E (208 GPa) and H (13.1 GPa) of AlTaO 4. The capacity for energy absorption during elastic deformation enhances crack formation energy and contributes to the relatively high fracture toughness (2.6 MPa m1/2) of AlTaO 4. This work elucidates the excellent mechanical properties of AlTaO 4 by applying nanoindentation and first-principle calculation, which will advance the applications of AlTaO 4 as high-temperature materials. [ABSTRACT FROM AUTHOR]

Functionally graded material (FGM) combines two or more constituents in which one gradually varies toward the other along the structure, improving properties. The contribution of this study is to present the characterisation results of an FGM composed of two groups of cutting tool materials, Al2O3-ZrO2 (ceramic-based alumina) and WC–Co (cemented carbide), designed by a thermomechanical model for predicting the residual stress to avoid thermal cracking. The main result comes from the sample manufactured by pulsed electric current sintering (PECS) at 1300 °C, 50 MPa, and a dwell time of 7 min. Microstructure, density, and mechanical and tribological properties were characterised. Two additional experiments were included to support the observations of the main result. Furthermore, homogeneous commercial materials, cemented carbide and aluminium oxide ceramic, were used to compare with the FGM results. Microscopic analysis revealed an eight-layer structure with no cracks. The relative density result indicated a porosity of 5.27%, mainly concentrated in the first layers. Thus, the Vickers hardness values showed that the first layer, rich in alumina-based ceramic (817 HV), was softer than the last layer, rich in cemented carbide (1272 HV). Conversely, the fracture toughness values were higher in the first layer (8 MPa.m1/2) and decreased towards the last layer (5 MPa.m1/2). Variations in properties along the structure were also observed in the scratch test. Scratch hardness increased towards the final layer. The FGM sample exhibited microcutting as an abrasive wear mechanism for the first three layers and a mixture of microcutting and microploughing for the last three layers. Finally, the drag coefficient results indicated greater friction in the first layers because of their toughest characteristics. Although the sample did not achieve full densification, changes in properties were observed; these properties may be improved by adjusting the sintering parameters. [ABSTRACT FROM AUTHOR]

The preparation of dense single-phase boride ceramics has always been a challenge. In this paper, single-phase W 2 B 5 ceramic with excellent performance was successfully prepared using W 2 B 5 powder and SPS-HF technology. Under the sintering condition of 1800 °C and 50 MPa, a nearly dense W 2 B 5 ceramic material with excellent mechanical properties was obtained. The relative density of the as-sintered W 2 B 5 ceramic achieved 96.72 % without any sintering additive. Additionally, the Vickers hardness, fracture toughness as well as bending strength were 30 GPa (9.8 N), 5.39 MPa·m1/2 and 522.7 MPa, respectively. The outstanding hardness and bending strength of W 2 B 5 ceramic could be attributed to its monophase W 2 B 5 structure and high densification degree. The primary fracture mode of W 2 B 5 ceramic was transgranular fracture, and the toughening mechanisms included crack deflection, crack bridging, and crack branching. [ABSTRACT FROM AUTHOR]

A novel high-entropy M 4 AlC 3 phase ceramic (M=Ti, V, Mo, Nb, Ta) was synthesized by three-step solid phase sintering, and the textured high-entropy M 4 AlC 3 composites were prepared for the first time by SPS uniaxial pressing of nano flakes generated via reactive ball milling. The microstructure were characterized in detail and Maud software was used for Rietveld refinement analysis of phase composition content. The results showed that Ti, V, Mo, Nb, Ta were successfully dissolved in M 4 AlC 3. On this basis, the density, hardness and mechanical properties before and after texture were tested. The results showed that the textured composite achieved 12.1 GPa Vickers hardness (//C-axis), 2.2 GPa compressive strength (//C-axis), 8.8 fracture toughness of MPa m1/2 (//C-axis) and 726 MPa bending strength (//C-axis). Dispersively distributed nano-Al 2 O 3 and texturization played a key role in strengthening and toughening. This work can provide an important reference for the subsequent preparation and texturing of high-entropy MAX ceramics. [ABSTRACT FROM AUTHOR]

Research laboratories worldwide use the spark plasma sintering (SPS) technique for sintering metallic and ceramic matrix composites. Typically, the SPS sintered parts are low circular cylinders (discs). The upscaling and industrialization of SPS technology face two challenges: the limitation of shaping non-cylindrical parts and the inhomogeneous sintering of large-sized products. This paper addresses these challenges in sintering axisymmetric shells within an SPS setup with improved thermal insulation. The paper considers the sintering of a 75 mm shell as a case study. The shell material is a zirconia-carbon nanotube composite. Finite element analysis revealed that homogeneous sintering of such a shell requires careful thermal insulation of the entire setup. Investigation of phases, microstructure, density, microhardness, and fracture toughness in the sintered shell showed a homogeneous structure and uniform properties. [ABSTRACT FROM AUTHOR]

Hydroxyapatite, commonly employed in bone defect repair, demonstrates limitations in load-bearing applications due to its poor mechanical property and biodegradability. This research introduces an innovative bone substitute material, namely, in situ magnesium-doped calcium phosphate microtube (Mg-CaP MT)-reinforced magnesium-doped hydroxyapatite composites (Mg-CaP MT /Mg-HA) inspired by microtube material with outstanding mechanical property and capillary tube in a plant. The in situ Mg-CaP MT , with a ∼7 μm diameter and 400–500 nm wall thickness, was formed by pore-forming carbon fiber (CF) and the coating on it. These microtubes are uniformly distributed within Mg-HA matrix. The composites can meet load-bearing bone requirements, demonstrating compressive strength of 167.0±20.7 MPa and fracture toughness of 2.04±0.13 MPa·m1/2. Notably, it exhibits exceptional permeability and biodegradability, attributed to capillary action by the Mg-CaP MT structure. The adjustable mechanical and biological properties of Mg-CaP MT /Mg-HA, based on microtube dimensions, content, and composition, offer a versatile solution for repairing various bone defects in load-bearing areas. [Display omitted] [ABSTRACT FROM AUTHOR]

ZrC-SiC-ZrB 2 ceramics were prepared via ultra-high pressure sintering under 15 GPa at 1200 °C. The densification mechanism, microstructures, and properties of the prepared ceramics were investigated. The sintered ceramics with ZrB 2 content of 15 vol % showed the improved comprehensive mechanical properties, including Vickers hardness of 26.6 GPa, Young's modulus of 469.1 GPa, and fracture toughness of 5.0 MPa·m1/2, which was 86.7 % higher than that of pure ZrC ceramics. In the sintered sample, the ultra-high pressure induced new microstructure, such as L-C lock in ZrC phase, stacking faults and nanotwins in SiC phase, and severe lattice distortion in ZrB 2 phase, jointly contributed to the improvement in Vickers hardness. Deflection and bridging during crack propagation were ascribed to the uniform combination of various phases. [ABSTRACT FROM AUTHOR]

In the present study, we optimized the fabrication process, characterized the microstructures and evaluated the mechanical properties of a high entropy carbide ceramic with novel composition, (HfNbTaTiW)C. Our results show that 1700 °C carbon thermal reduction (CTR) and 1800 °C spark plasma sintering (SPS) can yield a single phase (HfNbTaTiW)C with high relative density, low residual C/O and fine grain structure. The nanohardness of (HfNbTaTiW)C is on the lower end (28.16 GPa), but its fracture toughness (4.84 MPa m1/2) is superior to both its constituent monocarbides and most existing multi-cation transition metal carbides. The lattice distortion, bonding strength and stacking fault energy of (HfNbTaTiW)C are compared with (HfNbTaTiZr)C through First Principle Calculations to help understand the observed mechanical properties. The results indicate first, the reduced bonding strength contributes more importantly than the large lattice distortion to the hardness, leading to the observed low hardness of (HfNbTaTiW)C and second, the reduced bonding strength and low intrinsic stacking fault energy synergistically contribute to the observed high toughness of (HfNbTaTiW)C. [ABSTRACT FROM AUTHOR]

A series of (Yb 1-x Gd x) 4 Hf 3 O 12 (x=0, 0.1, 0.2, 0.3 and 0.4) ceramics were synthesized by a solid-state reaction at 1600 °C for 10 h. The phase compositions, microstructure, mechanical properties and thermophysical properties of (Yb 1-x Gd x) 4 Hf 3 O 12 ceramics were investigated. Yb 4 Hf 3 O 12 exhibited a δ-phase structure, while Gd3+ doped Yb 4 Hf 3 O 12 had a defect fluorite structure. The Gd3+ doped Yb 4 Hf 3 O 12 showed higher Vicker's hardness, fracture toughness and Young's modulus compared to Yb 4 Hf 3 O 12. The thermal conductivities of (Yb 1-x Gd x) 4 Hf 3 O 12 ceramics firstly decreased with increasing Gd3+ doping, but subsequently increased with further Gd3+ doping. The (Yb 0.7 Gd 0.3) 4 Hf 3 O 12 exhibited the lowest thermal conductivity of 1.33 W m-1·K-1 at 1200 °C. The thermal expansion coefficients (TECs) of Gd3+ doped Yb 4 Hf 3 O 12 were higher than that of Yb 4 Hf 3 O 12. The (Yb 0.7 Gd 0.3) 4 Hf 3 O 12 showed promising comprehensive properties, suggesting that it could be a potential candidate material for thermal/environmental barrier coatings (T/EBCs). [ABSTRACT FROM AUTHOR]

In this study, fracture behaviors of base metal and weld metal of ferritic steel welded joint in the thick wall pipeline for hydrogen transportation were investigated and the effects of hydrogen and specimen thickness (B) on fracture toughness were comprehensively considered in detail. A series of single edge notched tensile (SENT) tests for base metal and weld metal with B/W (width) ratio of 0.5, 1 and 2 were conducted with and without pre-electrochemical hydrogen charging, and crack tip opening displacement (CTOD) of δ m value was obtained by the double clip gauges method. It was found that fracture toughness (δ m) of base metal and weld metal decreased with increasing specimen thickness or hydrogenating, and δ m of hydrogenating specimen with B/W ratio of 2 was smallest. It was believed that large specimen thickness decreased fracture toughness by constraining plastic deformation at crack tip and restricting dislocations movement, while hydrogen promoted embrittlement by reducing cohesive energy of fracture. In the hydrogenating specimen with larger thickness, there was lower dislocation density near crack tip, leading to a decrease in trapped hydrogen and intensifying the cohesive energy reduction effect, which resulted in reduced δ m and the worse fracture toughness, and it means that hydrogen and specimen thickness synergistically affected fracture toughness. In addition, effect of thickness and hydrogen on decreasing fracture toughness was more pronounced for weld metal than base metal, which could be attributed to poorer plastic deformation ability of weld metal and lower dislocation density at crack tip. It is concluded that the hydrogen and thickness effects should be taken into account for the structural integrity evaluation of welded joint in hydrogen transportation pipeline. • Hydrogen coupled with specimen thickness severely deteriorated fracture toughness of base metal and weld metal. • Significant hydrogen embrittlement in thicker specimen was due to hydrogen, plastic deformation and dislocation interaction. • The hydrogen embrittlement effect was more pronounced for weld metal than base metal. • Structural integrity evaluation for welded pipelinemust take hydrogen and thickness into account. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT)‐polyetherimide (PEI) hybrid nanofibrous veils were prepared through the electrospinning process to function as an interlayer in carbon fiber reinforced polymer composites (CFRP), and the effects of the addition of the hybrid fiber veils on the interlaminar fracture properties and flexural properties of CFRP were investigated. The results showed that interleaving CNT/PEI hybrid veils can effectively avoid long‐troubled trade‐off between mode‐I interlaminar fracture toughness and in‐plane properties when using thermoplastic toughening materials. Specifically, the GIc value and flexural strength of the laminates were increased by as much as 86.2% and 14.3%, respectively when CNT content was reached up to 0.7 wt% in CNT/PEI hybrid veil. This method adopts ultra‐low PEI and CNT additions, and the limited quantity of these additives demonstrates a notably high interlaminar toughening efficiency while concurrently enhancing the strength, rendering it a promising strategy for both toughening and strengthening. Highlights: PEI is used as a carrier to transport CNT to the CFRP interlaminar layers.PEI‐CNT hybrid fiber veils improve GIC and flexural strength of CFRP.PEI‐CNT hybrid fiber veils impede crack expansion through various mechanisms.This method adopts ultra‐low PEI and CNT additions. [ABSTRACT FROM AUTHOR]

This study investigates the effect of incorporating polyethylene terephthalate (PET), polyetherimide (PEI), and polyether‐ether‐ketone (PEEK) thermoplastic films in melt form as interlayers to toughen carbon fiber/epoxy composites. The addition of melt‐infused PET, PEI, and PEEK film into carbon fiber/epoxy composite enhanced the mode‐I interlaminar fracture toughness (ILFT) by 60%, 156%, and 284%, respectively. The primary toughening mechanisms found were plastic deformation and mechanical interlocking through fiber bridging, which left fiber imprint traces on the fracture surface. The mode‐II ILFT of PET, PEI, and PEEK film interleaved laminates was improved by 80%, 188%, and 96%, respectively. Plastic deformation was observed to be the principal toughening mechanism. Notably, these enhancements in ILFT were achieved while simultaneously increasing interlaminar shear strength. These findings show the role of hot‐melt‐infused PET, PEI, and PEEK thermoplastic films in the improvement of ILFT of composites which is crucial in the design of damage‐tolerant composite structures. Highlights: Composites were interleaved with PET, PEI, and PEEK films via melt‐infusion.Mode‐I and mode‐II ILFT were significantly enhanced, up to 284% for PEEK.Failure exhibited plastic deformation, extensive fiber bridging, and pull‐out.Melt‐infusion created complex, mechanically interlocked interfaces. [ABSTRACT FROM AUTHOR]

Chemical grafting is commonly employed to functionalize carbon fiber (CF) surface to enhance the interfacial properties of CF reinforced polymer composites (CFRP) by forming a robust interface. However, an overly rigid interface layer can result in relatively poor interface toughness. To balance interfacial strength and toughness, this paper proposes an effective method to simultaneously strengthen and toughen the interface of CF/epoxy composites by grafting branched polyethyleneimine (PEI) on CF surface using hexachlorophosphazene (HCCP) as active intermediate, which features a rigid ring structure and six active P‐Cl groups. The introduction of PEI provided a large number of amine and imine groups on CF surfaces, which were contributive to improving surface wettability and reactivity of CF, thus resulting in strong chemical bonding between CF and epoxy matrix. Additionally, the long and flexible molecular skeleton of PEI constructed a rigid‐flexible composite interface, which could effectively reduce stress concentration and absorb impact energy. After surface modification with PEI, the interfacial shear strength and fracture toughness of CF/epoxy composite were increased to 89.9 MPa and 200.3 J m−2, by 64.3% and 149.7%, respectively, in compared with desized CF reinforced epoxy composites. Highlights: A rigid‐flexible interface was constructed between CF and epoxy resin.The interfacial strength and toughness of CFRP were synergistically improved.IFSS and interfacial toughness increased by 64.3% and 149.7%, respectively. [ABSTRACT FROM AUTHOR]

Three‐dimensional molybdenum disulfide (MoS2) functionalized MWCNTs hybrid nanoparticles were synthesized using in‐situ hydrothermal reaction. Two types of hybrids, MoS2/MWCNTs‐1 and MoS2/MWCNTs‐2 with MWCNTs to MoS2 precursor weight ratios 1:2 and 1:1 respectively were prepared with varying degrees of hybridization and the effects of their incorporation on tensile strength and fracture toughness properties of epoxies were investigated. Epoxy/MoS2/MWCNTs‐2 nanocomposites showed exceptional mechanical properties due to their improved dispersion, constrained chain mobility and excellent interfacial interactions. MoS2/MWCNTs‐2 nanocomposites showed maximum improvement of tensile strength by 28.52% at 0.5 wt% nanofiller concentration and the highest improvements in fracture toughness by 172% at 0.2 wt% nanofiller concentration. The excellent enhancement of fracture toughness properties was due to the synergic effect of MoS2/MWCNTs hybrid nanoparticles due to the crack pinning and bifurcation properties of MoS2 nanoparticles along with the pull‐out and crack bridging mechanisms of MWCNTs as observed in morphological analysis of fractures nanocomposites. The incorporation of 0.2 wt% of MoS2/MWCNTs‐2 increased the degradation temperatures of epoxy from 591 to 796°C at 95% weight loss due to the improved physical barrier effect. Highlights: MoS2/MWCNTs nanoparticles were synthesized using in‐situ hydrothermal reaction0.5 wt% MoS2/MWCNTs‐2 incorporated epoxies showed highest tensile strength0.2 wt% MoS2/MWCNTs‐2 incorporated epoxy composites show improved K1c valueIncorporation of MoS2/MWCNTs improved the thermal stability of epoxySynergistic effect of nanocomposite due to crack pinning, bifurcation & bridging [ABSTRACT FROM AUTHOR]

Flexible hydrogel film sensors have great advantages as human–machine interfaces for conformal contact with bio‐tissues, but suffer from weakness and dehydration, compromising flexibility and performance. Here, a breathable, highly stretchable, and anti‐dehydrating ultrathin organohydrogel film as a skin‐attachable strain sensor for long‐term motion monitoring is developed. An electrospun TPU (eTPU) nanomesh with hidden strength is used as skeleton to host in situ free radical polymerization of 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) and acrylamide (AAm) to form an interpenetrating double network organohydrogel with glycerol and water as solvent. Extensive hydrogen bonding between eTPU nanomesh and P(AMPS‐co‐AAm) network yields ultrathin organohydrogel film (≈200 µm) with synergetic deformation and energy dissipation upon stretching, leading to record‐high stretchability up to 920%, fracture toughness of 20.14 MJ m−3, fracture energy of 10 000 J m−2, and robustness over 4000 notched stretching cylcles to 50% strain. The binary glycerol/water solvent imparts excellent anti‐dehydration at room temperature for 10 d, and stable sensory performance from −20 to 60 °C. With a high water vapor transmission rate of 1.3 kg m−2 d−1, the film sensor ensures comfortable skin contact for continuous knee flexion monitoring throughout the day with stable signals. These organohydrogel film strain sensors are promising for wearable and long‐term motion monitoring applications. [ABSTRACT FROM AUTHOR]

Core–shell structural B 4 C@TiB 2 composite powders were synthesized via the molten salt method using micron-sized B 4 C and TiH 2 powders as raw materials. Furthermore, a SiC composite ceramic with B 4 C@TiB 2 core–shell structural units as the toughening phase was prepared by spark plasma sintering using SiC powder and the obtained B 4 C@TiB 2 composite powder as starting powders. The effects of calcination temperature and raw material ratio on the phase compositions and microstructure of the B 4 C@TiB 2 composite powders were studied, and the synthesis mechanism of the B 4 C@TiB 2 composite powder was explored. The formation mechanism of B 4 C@TiB 2 core–shell toughening units inside the SiC matrix was investigated, and the toughening mechanism of the SiC–B 4 C@TiB 2 composite ceramic was discussed. Results show that the B 4 C@TiB 2 core–shell units in the SiC matrix can induce a complex crack propagation mode and consume abundant crack propagation energy. Therefore, a high fracture toughness of 6.47 ± 0.32 MPa m1/2 is realized for the SiC–B 4 C@TiB 2 composite ceramics. [ABSTRACT FROM AUTHOR]

Zirconia-toughened alumina (ZTA) is widely applied in total hip arthroplasty (THA). However, problems with insufficient fracture toughness and lubrication remain, leading to wear, squeaking, and fracturing. In this study, the Cu doping of ZTA (Cu-ZTA) is proposed to solve these problems. To further promote the use of Cu-ZTA, the role of Cu doping on its tribological properties must be studied. In this study, the microstructure, mechanical properties, and stability capacity in a physiological environment, as well as the tribological behaviors of Cu-ZTA in phosphate-buffered saline (PBS) and bovine serum albumin (BSA), were systematically studied with varying amounts of Cu. The results demonstrated that holes and soft Cu-rich phases appeared, and grains grew after Cu doping, causing a decrease in hardness. The fracture toughness increased after Cu doping because the Cu-rich particles formed "bridges" during crack propagation and release energy. The incorporation of Cu improved the stability of ZTA in physiological environments, which enhanced the long-term stability of Cu-ZTA. The protein adsorption results indicated that a higher hydrophobicity and roughness contributed to a greater protein adsorption on the Cu-ZTA surfaces after Cu incorporation. In the BSA solution, the 5.0 wt% Cu-ZTA ceramics achieved a lower coefficient of friction (COF) and wear rate compared to ZTA, and a higher protein adsorption and formation of the denatured protein layer catalyzed by Cu ions in the wear track during friction, thus clearly improving the tribological properties of the Cu-ZTA. [ABSTRACT FROM AUTHOR]

This research aimed to create a new Li metasilicate-based glass-ceramic for dental use, prioritizing improved chemical durability (CD) and machinability while preserving good glass-forming ability (GFA) and adequate mechanical properties. Characterization also involved examining fracture strength (S f) and fracture toughness (K IC). The experimental approach involved precise microstructural adjustments through designed compositional changes and controlled thermal treatments. Four compositions underwent scrutiny using mechanical tests, microscopy, differential scanning calorimetry, and X-ray diffraction to analyze the impact of lithium metasilicate (LS) and disilicate (LS2) crystals on these properties. Machinability was evaluated by weight loss measurements during controlled grinding experiments. The developed GCs exhibited interconnected acicular LS and LS2 crystals, which resulted in favorable S f ∼300 MPa and K IC ∼1.7 MPa m1/2 (SEVNB). Although the K IC was smaller than that of an experimental LS-LS2 GC (285 MPa and 3 MPa m1/2(double torsion)) used as a reference, the chemical durability (126 μg/cm2 for ML14F GC) improved by nearly 50 % compared to the reference (∼220 μg/cm2). This study introduced three new GCs with LS as the major phase (rather than the traditional LS2), showcasing commendable GFA, chemical durability and machinability, with satisfactory flexural strength and fracture toughness. [ABSTRACT FROM AUTHOR]

3D printing of ceramics is a novel technology that allows for the rapid preparation of complex ceramic structures, with potential applications in various industrial fields. However, the high porosity often observed in ceramics prepared via 3D printing can negatively affect their mechanical properties. In this paper, a novel process for manufacturing silicon carbide ceramics reinforced with short carbon fibers (C f /SiC) is proposed. The process employs direct ink writing (DIW) and solid-phase sintering technology, leading to a substantial improvement in the mechanical properties of ceramics and a shorter preparation cycle. Bending properties and fracture toughness of C f /SiC ceramics were evaluated by a series of mechanical tests, including three-point bending and single-edge notched beam tests. The findings showed that the bending strength and fracture toughness of the ceramics were 446.0 MPa and 6.021 MPa•m1/2, respectively. Moreover, a theoretical model was developed to predict the strength of symmetrically distributed laminated beams with different fiber orientation, prepared by varying the printing direction. Simulation results on bending strength from the theoretical model are in good agreement with experimental result with prediction difference less than 11.41 %. [ABSTRACT FROM AUTHOR]

Si 3 N 4 ceramics now face new applications and challenges in the semiconductor field. The preparation of h-BN/Si 3 N 4 machinable ceramics incorporating 5–30 vol% h-BN via hot-pressing was carried out. This study systematically explored how the varying h-BN content influenced the composite's microstructure, mechanical attributes, and machinability. The results showed that some of the h-BN was encapsulated by growing Si 3 N 4 grains to form an intragranular structure during the process of hot-pressing, while the remaining h-BN exhibited uniform distribution along grain boundaries. The Si 3 N 4 phase transition in composites was inhibited by excessive h-BN, accompanied by a higher decrease in densification. The sample containing 20 vol% h-BN exhibited the best comprehensive performance, with high mechanical strength and excellent machinability. The bending strength and fracture toughness remained high at 862 MPa and 10.3 MPa m1/2, and could be effortlessly machined with cemented carbide drills. Additionally, the machinability of the composites was systematically characterized through observations of crack propagation paths, fitting of R-curves, and mechanical drilling tests. [ABSTRACT FROM AUTHOR]

Although Hf x Ta 2 O 2 x+ 5 shows great potential as a next-generation thermal barrier coating (TBC) material, the diversity of its potential modulated structures presents challenges in determining their mechanical properties. Hf x Ta 2 O 2 x+ 5 (x = 4, 6, 8) ceramics were successfully fabricated using the sol–gel method. Research on growth kinetics has indicated that grain boundary diffusion is the speed-controlling step. The activation energy increased with a larger modulated structure. In addition, the fracture toughness also increased from 1.98 MPa m1/2 for Hf 4 Ta 2 O 13 to 3.30 MPa m1/2 for Hf 8 Ta 2 O 21. Density functional theory calculations revealed that Hf x Ta 2 O 2 x+ 5 exhibited intrinsic ductility owing to the denser packing of atoms in its larger modulated structure. Thus, the tight-knit chemical bond net may contribute to a large surface energy. The results of this study provide deep insights into the toughening mechanism of modulated structures and pave the way for the design of next-generation TBCs. [ABSTRACT FROM AUTHOR]

When porous materials are subjected to compressive loads, localized failure chains, commonly termed anticracks, can occur and cause large-scale structural failure. Similar to tensile and shear cracks, the resistance to anticrack growth is governed by fracture toughness. Yet, nothing is known about the mixed-mode fracture toughness for highly porous materials subjected to shear and compression. We present fracture mechanical field experiments tailored for weak layers in a natural snowpack. Using a mechanical model for interpretation, we calculate the fracture toughness for anticrack growth for the full range of mode interactions, from pure shear to pure collapse. The measurements show that fracture toughness values are significantly larger in shear than in collapse, and suggest a power-law interaction between the anticrack propagation modes. Our results offer insights into the fracture characteristics of anticracks in highly porous materials and provide important benchmarks for computational modeling. Porous materials such as snow can collapse under compression, forming anticracks. The authors show that anticrack fracture modes vary with loading direction and find a mechanism that suggests that cracks grow more easily under compression than under shear, advancing stability models for porous materials. [ABSTRACT FROM AUTHOR]

Silicon carbide nanofiber/silicon carbide (SiCnf/SiC) composites with a laminar stacking structure were prepared by the slurry impregnation hot‐press sintering using aluminum (Al) powder, boron (B) powder, and carbon black as sintering aids. SiCnf paper was fabricated using nanofibers and impregnated with the slurry of SiCnp and sintering aids, and the SiCnf/SiC preforms were fabricated by the alternating stack of the SiCnf paper and SiCnp. The pyrolysis carbon and boron nitride interface layers were deposited on the surface of SiCnf by chemical vapor deposition and vacuum impregnation‐pyrolysis methods. The effects of different sintering temperatures on the relative density, porosity, sectional microscopic morphology, and mechanical properties of the composites were investigated. The results show that the fracture toughness of SiCnf/SiC composites is significantly improved. The mechanical properties of the composites were optimized at a sintering temperature of 1950°C and a sintering pressure of 30 MPa, with flexural strength and fracture toughness of 548 MPa and 15.86 MPa·m1/2, respectively. The liquid phase Al8B4C7 compound generated at the high temperature promoted the densification of the composites. [ABSTRACT FROM AUTHOR]

In the present investigation, diverse functionalized states of multi-walled carbon nanotubes (MWCNT) were employed in fabricating glass/epoxy composites, with the MWCNT consistently incorporated at a 0.5 wt.% concentration. These functionalization states included pristine, hydroxyl, amine, and carboxylic conditions, systematically compared against neat glass/epoxy composites. The findings elucidated that all three functionalizations positively influenced the enhancement of interlaminar shear strength, mode-I interlaminar fracture toughness, and mode-II interlaminar fracture toughness properties. Notably, the amine-functionalized MWCNT exhibited superior performance relative to other formulations. The composite reinforced with amine MWCNT demonstrated significant improvements in ILSS, mode-I ILFT, and mode-II ILFT by 41.82%, 37.75%, and 40.93%, respectively. These enhancements are attributed to factors such as the presence of a more functional group, the quantity of individual MWCNT, and the introduction of additional damage mechanisms, including MWCNT pullout and bridging. Highlights: Improvement in ILSS of glass/epoxy composite by functionalized MWCNT by 20.11-41.82% range. Improvement in mode-I ILFT of glass/epoxy composite by functionalized MWCNT by 5.54-30.81%. Improvement in mode-II ILFT of glass/epoxy composite by functionalized MWCNT by 8.46-40.93%. Microscopic characterization using field-emission scanning electron microscopy revealed existence of MWCNT pullout and bridging. [ABSTRACT FROM AUTHOR]

The fracture resistance of adhesive joints depends on the bondline thickness, especially in the toughest systems. While increasing the adhesive thickness to operate at peak fracture toughness is anticipated to be attractive, it leads to a mass increase and to a decrease of the effective shear stiffness and strength, calling for a trade-off. Here, we follow a rational materials selection approach for mechanical design to address different sets of objectives and constraints representative of different classes of applications. The approach is applied to select the best conventional adhesive based on a novel database. Mechanical analysis with two different degrees of complexity is considered. The elementary level only accounts for the influence of thickness on toughness, while more advanced models introduce the dependence of shear strength on thickness as well as the stiffness mismatch with the adherends. The best adhesive choice strongly depends on the objectives, constraints, and loading configuration. However, the ranking is not drastically affected by the adherends' stiffness. Gaps found for stiff/strong and tough adhesives motivate the development of architected joints. Inserting stop holes improves damage tolerance and density but reduces the shear strength and stiffness, requiring an optimum design. [ABSTRACT FROM AUTHOR]

The aim of achieving integration of lightweight, high strength, high‐temperature resistant, and satisfactory electromagnetic (EM) wave absorption was successfully accomplished in the present study by synthesizing TiC–TiB2 fibers reinforced Si3N4 composites, which were pressureless sintered at 1650°C for 2 h. The preparation of TiC–TiB2 fibers was conducted through a chloride‐assisted carbothermic method. This work focused on investigating the effects of incorporating TiC–TiB2 fibers on the mechanical properties and EM wave absorption characteristics of the composites. The 30 wt% TiC–TiB2/Si3N4 composite displayed the bulk density of 1.89 g/cm3, bending strength of 93.11 ± 3.91 MPa, fracture toughness of 1.81 ± 0.10 MPa m1/2, minimum reflection loss of −38.87 dB, and effective absorption bandwidth of 1.43 GHz in the Ku‐band, respectively. The as‐synthesized TiC–TiB2/Si3N4 composites are promising candidates for EM wave absorbing load‐bearing materials due to their outstanding mechanical properties and microwave absorption properties. [ABSTRACT FROM AUTHOR]

In this work, stacked SiC fibers paper‐reinforced SiC ceramic matrix composites (SiCnf/SiC CMCs) were prepared by nanoimpregnation and transient eutectic (NITE) process using ultra‐long single‐crystal SiC nanofibers. The effect of the SiCnf surface modification via boron nitride (BN) interphase deposition as well as the sintering additive (Al2O3–Y2O3) content on the density, microstructure, and mechanical properties of SiCnf/SiC CMCs has been investigated systematically. The results revealed that the laminated SiCnf/SiC CMCs feature a significant saw‐tooth‐like curve on the load–displacement test, which indicates that the obtained laminated structure with the weak interlayer binding owning to the BN coating treatment possesses significant toughening to the SiC ceramics. Specifically, the SiCnf/SiC CMCs with the sintering additive content of 12 wt% revealed a fracture toughness of over 10 MPa m1/2 after 60 min of BN interface deposition, which is 104.31% higher than that of the composites prepared without BN coating. [ABSTRACT FROM AUTHOR]

To broaden the applications of yttria‐stabilized zirconia (YSZ) in mobile phone back panels and high‐end decorative materials, the 3 mol% YSZ (3YSZ) ceramics doped with erbium oxide (Er2O3) as colorant were successfully sintered at 1250 and 1350°C in air. The influences of Er2O3‐doping concentration and sintering temperature on the phase, microstructure, color, and mechanical properties of the pink Er2O3‐3YSZ ceramics were investigated. As the Er2O3 concentration increased, the redness value a* gradually increased, while the yellowness value b* and the lightness value L* gradually decreased. The highest value a* and b* of Er2O3‐3YSZ ceramics reached absolute values of 15.2 and 4.5, respectively. The effect of Er2O3 concentration is also depicted in detail, which also affects the mechanical properties including hardness and fracture toughness of the ceramics. The maximum hardness and fracture toughness of Er2O3‐3YSZ ceramics reached 13.9 ± 0.3 GPa and 6.21 ± 0.20 MPa·m1/2, respectively. The hardness of the ceramics exceeds 12.5 GPa, which is the required market index for further practical application. This work provides a method for preparing 3YSZ ceramics with excellent mechanical properties and bright pink color, which has the potential to be used in the fields of advanced and superior electronics in particular. [ABSTRACT FROM AUTHOR]

Ti(C, N)‐based cermets have been considered to be the most potential candidates for WC‐Co cemented carbides as tool material due to their various advantages. However, the trade‐off between hardness/strength and toughness limits their further application. Herein, we present new (Ti, W, Mo, Cr)(C, N)‐based cermets showing superior mechanical properties with hardness of 1525 MPa, transverse rupture strength of 2428 MPa, and fracture toughness of 11.44 MPa·m1/2 by compositional and interfacial modification. The strengthening and toughening mechanisms were revealed by experimental observation and theory calculation. It could be clarified that the high elastic modulus caused by a polar covalent bond in the hard phase and solid solution strengthening of the binder phase attributed to the hardness. The strong interface bonding between the core/rim, inner/outer rim, and rim/binder phases stemming from the composition optimization contributed to super crack resistance. Intergranular fracture in submicron‐scaled hard phases led to the crack deflection, transgranular fracture in the micron‐scaled hard phases consumed more energy due to their high intrinsic hardness and excellent interface coordination. The synergy of multi‐scaled hard particles brought about excellent comprehensive mechanical properties. [ABSTRACT FROM AUTHOR]

Improving asphalt mixtures has become increasingly important due to the rise in traffic volume, high maintenance costs, and the challenges associated with their implementation. Previous studies have examined various additives and modifiers. This study investigated the effect of nano Al2O3 on two significant potential damages in asphalt pavements: low-temperature cracking and moisture sensitivity. The results of this study can be used to propose a suitable solution to minimize the probability of these failures occurring in asphalt pavements. Moreover, this study examined the impact of loading modes, temperature, and crack type on the fracture toughness of asphalt mixtures. In addition to exploring pure mode I and pure mode II, four distinct mixed modes (I/II) were also studied because, usually, this mode is the critical mode of the asphalt mixture. Temperature was another variable observed to validate the elasticity of asphalt mixtures at low temperatures. Lastly, the study investigated the effect of incorporating nano Al2O3 on the fracture toughness of the asphalt mixture under different temperatures and crack geometries. To achieve the objectives of this study, the semicircular bending and indirect tensile tests were conducted. The results showed that adding 0.6% nano Al2O3 can increase the crack resistance of asphalt mixtures by up to 12%. Additionally, the study demonstrated that incorporating 0.6% nano Al2O3 can decrease the vulnerability of asphalt mixtures to moisture by 5.1%. The response surface method technique was employed to analyze the laboratory data statistically. A reduced cubic model was utilized to assess the relationship between independent factors (loading mode, temperature, crack type, and nano Al2O3 content) and fracture toughness due to its superior fit with the laboratory results Next, sensitivity analysis was used to find the effect value of each parameter on the fracture toughness of the asphalt mixture. The sensitivity analysis results showed that the loading mode, temperature, crack type, and use of nano Al2O3 , respectively, will significantly impact the fracture toughness of the asphalt mixture. [ABSTRACT FROM AUTHOR]

To assess the influence of calcination process on the properties of minimally processed recycled 3Y-TZP, and to compare it with its commercial counterpart. Non-milled 3Y-TZP waste was collected, fragmented and ball-milled to a granulometric < 5 µm. Half of the recycled powder was calcined at 900 °C. Recycled 3Y-TZP disks were uniaxially pressed and sintered to create two recycled groups: 1) Calcined and 2) Non-calcined to be compared with a commercial CAD/CAM milled 3Y-TZP. The microstructure of experimental groups was assessed through density (n = 6), scanning electron microscopy (n = 3) and energy-dispersive X-ray spectroscopy (n = 3); and the crystalline content was evaluated through X-ray diffraction (XRD) (n = 3). Optical and mechanical properties were investigated through reflectance tests (n = 10), and Vickers hardness, fracture toughness (n = 5), and biaxial flexural strength tests (n = 16), respectively. Fractographic analysis was performed to identify fracture origin and crack propagation. Statistical analyses were performed through ANOVA followed by Tukey´s test, and by Weibull statistics. Particle size distribution of recycled powder revealed an average diameter of ∼1.60 µm. The relative density of all experimental groups was > 98.15 % and XRD analysis exhibited a predominance of tetragonal-phase in both recycled groups, which were similar to the crystallographic pattern of the control group. Cross-section micrographs presented flaws on the non-calcined group, and a more homogeneous microstructure for the calcined and commercial groups. Commercial samples showed lower contrast-ratio and higher translucency-parameter than the recycled groups, where non-calcined presented higher translucency-parameter and lower contrast-ratio than its calcined counterpart. The commercial group presented higher fracture toughness and characteristic strength than the recycled groups. Moreover, the calcined group exhibited higher hardness, characteristic strength, and probability of survival at higher loads than the non-calcined group. Fractographic analysis depicted the presence of microstructural flaws in the non-calcined group, which may have acted as stress-raisers and led to failures at lower flexural strengths values. The calcination process improved the microstructure, optical, and mechanical properties of the recycled 3Y-TZP. • Effect of calcination on minimally processed recycled zirconia powder was assessed. • Calcination enhanced the microstructure, optical, and mechanical features of the recycled 3Y-TZP. • Calcination did not promote alterations to the crystalline structure of the recycled 3Y-TZP. • Calcined powder resulted in a more homogeneous microstructure. • Recycled 3Y-TZP demonstrated a potential for applications in reconstructive dentistry. [ABSTRACT FROM AUTHOR]

In this study, AlSi10Mg samples were manufactured by laser-powder bed fusion process to explore the fracture toughness dependence on both built orientation and aging treatment. The experiments were performed on as-built and directly-aged (200 ∘ C/4 h) conditions, with the latter revealed to be a valuable treatment for improving fracture toughness. A comprehensive investigation involving detailed microstructural analysis, grain-orientation mapping, and crack-tip strain measurements was conducted to investigate the mechanisms governing the material behavior. The results revealed that specimens subjected to direct aging display higher toughness, thereby enhancing the fracture resistance of AlSi10Mg. Moreover, a considerable variation in fracture toughness values was observed for the different printing orientations, indicating the existence of manufacturing-induced anisotropy. The findings highlight that this anisotropy mainly correlates with the distinctive microstructure induced by the additive manufacturing process. In particular, this study focuses on the different preferential crack paths dictated by the melt pool boundaries orientation respective the crack propagation direction. A substantial reduction in fracture toughness was observed when the crack propagates along the melt pool boundaries. [ABSTRACT FROM AUTHOR]

In this letter, we present interfacial fracture toughness data for a polymer-metal interface where tests were conducted at various test temperatures T and loading rates δ ˙ . An adhesively bonded asymmetric double cantilever beam (ADCB) specimen was utilized to measure toughness. ADCB specimens were created by bonding a thinner, upper adherend to a thicker, lower adherend (both 6061 T6 aluminum) using a thin layer of epoxy adhesive, such that the crack propagated along the interface between the thinner adherend and the epoxy layer. The specimens were tested at T from 25 to 65 °C and δ ˙ from 0.002 to 0.2 mm/s. The measured interfacial toughness Γ increased as both T and δ ˙ increased. For an ADCB specimen loaded at a constant δ ˙ , the energy release rate G increases as the crack length a increases. For this reason, we defined rate effects in terms of the rate of change in the energy release rate G ˙ . Although not rigorously correct, a formal application of time–temperature superposition (TTS) analysis to the Γ data provided useful insights on the observed dependencies. In the TTS-shifted data, Γ decreased and then increased for monotonically increasing G ˙ . Thus, the TTS analysis suggests that there is a minimum value of Γ. This minimum value could be used to define a lower bound in Γ when designing critical engineering applications that are subjected to T and δ ˙ excursions. [ABSTRACT FROM AUTHOR]

LaMgAl 11 O 19 (LMA) with magnetoplumbite structure has emerged as a promising candidate for thermal barrier coating (TBC). However, the inherent high thermal conductivity and relatively low thermal expansion coefficient (TEC) of LMA impose limitations on its further application. In this work, a novel high-entropy hexaluminate (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2)MgAl 11 O 19 (HE-LMA) has been designed and prepared to overcome these obstacles. HE-LMA with homogeneous chemical composition distribution possesses excellent phase stability up to 1600°C. Moreover, the TEC of HE-LMA (9.22 × 10−6 K−1 at 1300°C) is larger than that of LMA. The high-entropy strategy effectively decreases the thermal conductivity of HE-LMA (from 3.27 W/(m⋅K) at room temperature to 2.19 W/(m∙K) at 1000°C) in comparison to that of LMA (3.63–2.62 W/(m∙K)). Furthermore, HE-LMA demonstrates higher microhardness and fracture toughness due to the lattice distortion. These results indicate that (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2)MgAl 11 O 19 has the potential to be applied as a TBC. [ABSTRACT FROM AUTHOR]

Dense silicon carbide (SiC) composites with 0–30 vol% (ZrN-TiB 2) were fabricated by using liquid phase spark plasma sintering at a relatively lower sintering temperature (1800 °C) and shorter holding time (5 min). The effects of co-addition of ZrN and TiB 2 on densification, mechanical properties, and electrical conductivity of SiC ceramics were investigated. The reinforcement significantly enhanced density of sintered composites, while the phase analysis and microstructure confirm the suppression of β→α phase transformation in the SiC matrix. The fracture toughness ranged from 4.1 to 4.6 MPa·m0.5, hardness from 19.5 to 20.3 GPa, and electrical conductivity from 4.85 ×101 to 1.25 ×103 (Ω·cm)−1. Incorporating conductive reinforcements and nitrogen additives enhanced electrical conductivity. Successful wire-EDM cutting of SiC-ZrN-TiB 2 composites demonstrate the feasible alternative to conventional machining of non-oxide ceramics with a maximum material removal rate of 8.54 mm2/min. [Display omitted] [ABSTRACT FROM AUTHOR]

The sintering of zirconium hydride (ZrH 2- x) without hydrogen atmosphere faces the challenge of thermal dehydrogenation problem, which is overcome by the high-pressure spark plasma sintering (HPSPS) technique in this study. The application of high pressure remarkably reduces the initial densification temperature and effectively restrains the thermal dehydrogenation of ZrH 2- x in SPS. Under 500 MPa loading, ε-ZrH 1.72 monolith with high densification (96.62 %) and high hydrogen density (6.04 × 10 22 atoms H/cm3) is sintered at a relatively low temperature of 700 °C for only 5 min. Meanwhile, the grain growth of ZrH 2- x is very limited. The Young's modulus and hardness of the sintered ε-ZrH 1.72 are 58.68 GPa and 2.61 GPa respectively. Compared with the directly hydrided ε-ZrH 2- x , the sintered ε-ZrH 1.72 has a more uniform hardness distribution and improved fracture toughness of 3.19 MPa m1/2. This study provides a valuable reference for the sintering of other easily decomposable materials. [ABSTRACT FROM AUTHOR]

Novel dual plate-like grains of (Ti, Zr)B 2 and W 2 B 5 toughened solid solution composites were fabricated by the in-situ reaction spark plasma sintering at 1800 °C using (Ti, W)C and ZrB 2 powders. The composites were predominated and composed of the (Zr, Ti, W)C solid solutions and plate-like (Ti, Zr)B 2. In the (Ti, W)C-ZrB 2 reaction system, W promotes the anisotropic growth of (Ti, Zr)B 2 grains, while Ti makes the formation reactions of W x B y thermodynamically feasible. When the addition of ZrB 2 exceeds 40 mol%, W begins to be boronized into W x B y which is mainly composed of plate-like W 2 B 5. The (Ti, W)C-50 mol% ZrB 2 composite with dual plate-like grains of (Ti, Zr)B 2 and W 2 B 5 exhibited the best comprehensive mechanical properties of hardness of 26.5 GPa, flexural strength of 620 MPa, and fracture toughness of 6.6 MPa·m1/2, which provide a new approach for the enhanced toughness without the introducing of metal impurities. • Dual plate-like grains of (Ti, Zr)B 2 and W 2 B 5 toughened (Zr, Ti, W)C ceramics were fabricated by the in-situ reaction SPS. • Ti makes the formation of W x B y thermodynamically feasible, while W promotes the anisotropic growth of (Ti, Zr) B 2 grains. • The 50ZB exhibited a high fracture toughness of 6.6 MPa·m1/2, which provide a new approach for the enhanced toughness. [ABSTRACT FROM AUTHOR]

Background: Lithium penetration-induced fracture within solid electrolytes (SEs) is a major issue hindering the commercialization of solid-state lithium-ion batteries (SS-LIBs). Such fracture has been frequently observed during electrochemical plating of lithium (Li)-metal anodes, but its mechanistic origin is still largely unclear. Objective: We present the first quantitative operando analysis of the fracture characteristics of a model SE material under battery-relevant electrochemical cycling conditions. Methods: Full-field deformation during Li deposition-induced cracking of garnet-type LLZTO was measured using the digital image correlation (DIC) method. The obtained displacement data were denoised via equilibrium smoothing, and then fitted to the linear elastic asymptotic crack-tip field to extract the electrochemical fracture toughness values under different current densities. Results: The physics-based equilibrium smoothing method demonstrated effectiveness in enhancing the accuracy of DIC measurements. The electrochemical fracture toughness obtained was substantially lower than the mechanical fracture toughness of the same material determined through indentation, attributed to combined effects of electrochemical embrittlement and a transition in fracture mode from intergranular to transgranular. Conclusion: The discrepancy between the two types of fracture toughness suggests that electrochemical cycling could have a significant impact on the fracture mode and resistance of a solid electrolyte. [ABSTRACT FROM AUTHOR]

Background: The surface brittle fracture of cermet coating seriously restricts its application. Accurate evaluation of the fracture toughness of cermet coating is a prerequisite for improving its life. Objective: This paper aims to propose an accurate characterization method for fracture toughness of cermet coating. Methods: By coupling instrumented indentation and X‑ray computed tomography (XCT), the indentation-induced fracture behaviors under various loads within WC-12%Co coatings were studied. The three-dimensional subsurface crack morphologies and the damage evolution within the coating were nondestructively observed by XCT. The indentation response was correlated with the damage evolution. The impact of substrate effects on indentation-induced fracture behaviors was further studied using finite element analysis (FEA). Results: The Palmqvist shape of the indentation crack under low loads was successfully identified. The first pop-in event in the load-displacement (P-h) curve was determined to be triggered by bottom cracking, marking the onset of the multiple fracture mode. Laugier's equation offered a stable and reliable estimation of fracture toughness for the coating in the radial cracking mode. Conclusions: XCT plays a crucial role in selecting the appropriate equation for indentation toughness calculation. The critical indentation depth for the first pop-in was suggested as the threshold for reliably extracting intrinsic fracture toughness of cermet coatings. Numerical results revealed a constant linear relationship between the critical depth and coating thickness, and a high sensitivity of the critical depth to yield stress of the substrate. The proposed analytical procedure holds potential for generalization to diverse cermet coatings on metal substrates. [ABSTRACT FROM AUTHOR]

Achieving an optimal balance between mechanical properties, dielectric properties, and thermal shock resistance presents a significant challenge in the development of advanced ceramics. This study investigates Si 3 N 4 -BN composite materials, prepared by hot-press sintering with magnesium aluminum silicate (MAS) as the sintering additive, to assess the impact of varying hexagonal boron nitride (h -BN) content on their mechanical and dielectric properties, as well as their thermal shock resistance. At an h -BN content of 20 wt%, the BN layers act as a toughening phase through a pull-out mechanism, minimally impacting the composite's density. This composition results in superior fracture toughness (7.4 MPa m1/2), high strength (598 MPa), low dielectric constants (∼6.8), and dielectric loss (∼7.4 × 10−3). Notably, after a thermal shock at 1000 °C, the composite exhibits a peak residual strength of 621 MPa, surpassing its initial strength. This enhanced performance is attributed to the formation of a dense Mg–Al–Si–B–O oxide glass layer on the surface during thermal shock, which not only repairs surface defects but also induces compressive stress. The development of the Si 3 N 4 -BN-MAS composite, with its outstanding comprehensive performance, marks a significant advancement for materials used in high-temperature wave transmission applications. [ABSTRACT FROM AUTHOR]

In this paper, high transmittance glass-ceramics containing Zirconium Yttrium Oxide (Zr 0.82 Y 0.18 O 1.91) nanocrystals were successfully prepared by melt cooling and crystallization heat-treatment method. The effects of Y 2 O 3 concentration on the structure, crystallization performance, transmittance, and indentation fracture toughness of Na 2 O–Al 2 O 3 –B 2 O 3 –SiO 2 –ZrO 2 glass and glass-ceramics were explored. The addition of Y 2 O 3 improved the Vickers hardness (4.81 GPa–5.25 GPa) and indentation fracture toughness (0.78 MPam1/2 to 0.95 MPam1/2) of the glasses. Y 2 O 3 successfully facilitated the precipitation of the non-alkaline crystalline phase Zr 0.82 Y 0.18 O 1.91 at low heat-treatment temperatures. The precipitation of Zr 0.82 Y 0.18 O 1.91 nanocrystals improves the Vickers hardness (5.17 GPa–5.56 GPa) and indentation fracture toughness (0.90 MPam1/2 to 1.01 MPam1/2) in glass-ceramics, while concurrently preserving a high level of visible light transmittance (∼90 %). This demonstrates its potential applications in the field of protective covers for electronic displays. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN), prized for its high thermal conductivity and electronic insulating properties, finds widespread use in electronic applications, particularly as a substrate material. However, its relatively low fracture toughness limits its application. In this study, to enhance both the thermal and mechanical properties of AlN ceramics, we thoroughly investigate the microstructure, thermal, and mechanical properties of self-reinforced AlN ceramics fabricated by spark plasma sintering, with self-reinforcement achieved through the integration of AlN whiskers within the AlN matrix. Unlike previous studies utilizing conventional pressureless sintering with limited sintering conditions, this work employs spark plasma sintering with a wide range of temperatures (1600–1900 °C) and holding times (10–30 min), providing a comprehensive understanding of the sintering behavior. Microstructural features, observed through optical and scanning electron microscopy, reveal distinct toughening mechanisms via crack deflection and branching, with a maximum 20% enhancement. The self-reinforced AlN ceramics exhibit remarkable improvements in thermal conductivity, reaching up to 150 W m−1 K−1, surpassing reported values for spark plasma-sintered AlN ceramics. Adding AlN whiskers enhances the thermal and mechanical properties of AlN simultaneously, particularly at 1800 °C for 10 min with controlled grain size and nicely integrated AlN whiskers. This work not only contributes valuable insights into the complex relationship between processing parameters, microstructure, and resulting thermal and mechanical properties but also highlights the enhanced thermal and mechanical properties of self-reinforced AlN ceramics. [ABSTRACT FROM AUTHOR]

As a thermal barrier coating (TBC) material, 8 wt% yttria-stabilized zirconia (8YSZ) exhibits poor resistance against calcium–magnesium–aluminosilicate (CMAS) corrosion. This is caused by the penetration of molten CMAS glass and the depletion of Y3+, which limits the lifetime of 8YSZ. In this study, a multi-rare-earth-oxide-doped zirconia (15 wt% (Lu 0.2 Yb 0.2 Dy 0.2 Gd 0.2 Y 0.2)–ZrO 2 , denoted as 15LYDGY–SZ) ceramic was prepared to examine its interaction with CMAS. The sluggish diffusion effect and the competition between various dopant elements toward reaction with CMAS effectively slow down the atomic diffusion and limit the transformation of tetragonal phase into monoclinic phase in 15LYDGY–SZ ceramic. Compared with the currently used 8YSZ ceramic, the corrosion resistance of 15LYDGY–SZ to CMAS and its retention rate of fracture toughness after CMAS corrosion are improved. The results show that the multi-rare-earth-oxide-doped zirconia ceramic prepared in this study is a promising candidate material for the development of future TBCs. [ABSTRACT FROM AUTHOR]

In the present work nano-sized TiN powders were consolidated and sintered in nitrogen, argon and air using microwave power of 900 W at frequency 2.45 GHz. Green compacts were exposed to microwave energy, and heated at an in-situ temperature of 1500 °C without holding time. The relative density achieved was ∼92 %. X-ray diffraction analysis showed presence of TiN as the dominant major phase. The microstructures indicate that the sintered samples retained their nanocrystallinty, though aggregates comprising clusters of nanoparticle was noticed with size in the range of 80–400 nm due to high heating rate. Micro indentation assessment indicates average Vickers hardness of 15.2 ± 0.5 GPa. The lengths of cracks originating from the indentation edges were measured; the indentation fracture toughness were obtained between 4.0 and 4.5 MPa.m1/2. The observed properties indicate the suitability of the sintered material in tribological applications. [Display omitted] • TiN ceramics without binders and additives was processed using microwave energy. • Use of SiC and graphite powder susceptors significantly reduced processing time. • Compacts sintered at high heating rate attained ∼92 % relative density. • Sintering was accomplished with comparable mechanical properties while retaining nanocrystallinity. [ABSTRACT FROM AUTHOR]