High Toughness Research Articles

Bright Bifacial White-Light Illumination by Highly Deformable Electroluminescent Devices Based on Transparent Ionic-Hydrogel Electrodes and Quantum-Dot Color Conversion.

Deformable alternating-current electroluminescent (ACEL) devices are of increasing interest because of their potential to drive innovation in soft optoelectronics. Despite the research focus on efficient white ACEL devices, achieving deformable devices with high luminance remains difficult. In this study, this challenge is addressed by fabricating white ACEL devices using color-conversion materials, transparent and durable hydrogel electrodes, and high-k nanoparticles. The incorporation of quantum dots enables the highly efficient generation of red and green light through the color conversion of blue electroluminescence. Although the ionic-hydrogel electrode provides high toughness, excellent light transmittance, and superior conductivity, the luminance of the device is remarkably enhanced by the incorporation of a high-k dielectric, BaTiO3. The fabricated ACEL device uniformly emits very bright white light (489cdm-2) with a high color-rendering index (91) from both the top and bottom. The soft and tough characteristics of the device allow seamless operation in various deformed states, including bending, twisting, and stretching up to 400%, providing a promising platform for applications in a wide array of soft optoelectronics.

Tailoring the Holocellulose Fiber/Acrylic Resin Composite Interface with Hydrophobic Carboxymethyl Cellulose to Enhance Optical and Mechanical Properties.

Interface engineering is essential for cellulosic fiber-reinforced polymer composites to achieve high strength and toughness. In this study, carboxymethyl cellulose (CMC) functionalized with hydrophobic quaternary ammonium ions (QAs) were utilized to modify the interface between holocellulose fibers (HF) and acrylic resin. The wet HF/CMC papers were prepared by vacuum filtration, akin to papermaking, followed by cationic ion exchange with different hydrophobic QAs. Subsequently, the modified papers were dried, impregnated with an acrylic resin monomer, and cured to produce transparent composite films. The effect of the hydrophobic QA moieties on the structure and optical and mechanical properties of the HF/CMC/acrylic resin composites were investigated. The composite film with cetyltrimethylammonium (CTA)-functionalized CMC showed high optical transmittance (87%) with low haze (43%), while the composite film with phenyltrimethylammonium (PTMA)-functionalized CMC demonstrated high Young's modulus of 7.6 GPa and high tensile strength of 180 MPa. These properties are higher than those of the composites prepared through covalent interfacial modification strategies. The results highlighted the crucial role of hydrophobic functionalized CMCs in facilitating homogeneous resin impregnation in the HF fiber network, producing a composite with enhanced interfacial adhesion strength, increased optical transparency, and mechanical strength. This facile use of hydrophobic CMCs as interfacial compatibilizers provides an energy-efficient route for preparing transparent, thin, and flexible composite films favorable in optoelectronic applications.

Mechanical properties and water resistance study of basic magnesium sulfate cement-emulsified asphalt composite materials

This study introduces a novel semi-flexible composite material (BMSC-EA), formed by merging the favorable properties of emulsified asphalt (EA), known for its high flexibility and crack resistance, with basic magnesium sulfate cement (BMSC), recognized for its high rigidity, early strength, and toughness. The research systematically explores the impact of varying EA dosages on BMSC properties. Furthermore, the study analyzes the phase composition, pore structure, and microstructure of BMSC-EA materials. Results indicate that an increase in EA dosage leads to a corresponding extension in the setting time of BMSC, accompanied by a gradual decrease in compressive and flexural properties. Interestingly, the flexural compression ratio of BMSC increases, suggesting that EA addition significantly enhances BMSC toughness. The principal hydration product of BMSC comprised crystals of 5Mg(OH)2∙MgSO4∙7H2O (5∙1∙7 phase). However, the introduction of EA exerted an inhibitory influence on the generation of Mg(OH)2, leading to a scenario where more MgO remained uninvolved in the hydration reaction. The porosity of the BMSC matrix increases with higher EA content. After subjecting the BMSC-EA material to water immersion treatment, a noteworthy observation emerged: exceptional water resistance was evident when the EA dosage reached 10%. This phenomenon was primarily ascribed to the heightened densification (ultrasonic velocity) observed in the BMSC-EA samples under these conditions. Additionally, the study observes further growth of Mg(OH)2 in BMSC after water immersion treatment, but excessive Mg(OH)2 negatively impacts BMSC-EA. These findings serve as both experimental and theoretical foundations for advancing innovative semi-flexible composite pavement materials.

Influence of clean cooling medium on the hard drilling performance and machined surface integrity of 42CrMo steel

42CrMo ultra-high strength steel has high strength and fracture toughness, which is widely used in key components, such as gears, connecting rods and molds. This type of workpiece material, especially after quenching and hardening treatment, still has prominent issues with hole machining. In this work, the clean cutting media, including dry, cold air and liquid nitrogen (LN2), are selected to investigate the hard drilling performance and machined surface integrity of 42CrMo steel. The feasibility of extending tool life and improving hole machining quality is explored through clean cooling medium. The cutting force and cutting temperature are lower under cold air and LN2 conditions than that under dry cutting conditions. The tool life is extended under cold air and LN2 conditions. The low temperature brought by LN2 promotes the transformation from folded to lamellar for chip free surface. The degree of chip curling becomes larger and easier to break and discharge, which reduces the unfavorable effects of chip clogging. The thermal damage phenomenon on the hole wall surface is disappeared. The surface roughness is reduced by 37.3%, and the maximum microhardness is increased by 6.6%, which significantly improves the machined surface integrity of holes. This work demonstrates the feasibility of improving the machinability of harnessed ultra-high strength steel by LN2 cooling.

Experimental study on Corn Straw Fiber (CSF) toughening EPS concrete

The natural Corn Straw Fiber (CSF), it has the advantages of light weight, high strength, good toughness and renewable, can delay the cracking and improve the toughness of cement-based materials. The effects of different mass fractions of CSF and Expanded-Polystyrene (EPS) particles on the compressive strength, flexural strength, splitting tensile strength and their failure modes, load-displacement curves and toughness of EPS concrete were analyzed by full factorial experimental design method. The compressive toughness index (I0, I1) and fracture energy (Gf) were defined to evaluate the effect of CSF on toughening EPS concrete. The results show that the addition of CSF can improve the compressive strength, flexural strength and cracking toughness of EPS concrete to a certain extent. The maximum compressive strength occurred in the E1F3 specimen with a CSF content of 3 % in Group I, which was 1.12 MPa, and the improvement rate was also the highest among the four groups, reaching 69.7 %. The compressive toughness index I1 also reached its maximum in the E1F3 specimen; The maximum flexural strength occurred in the E3F4 specimen with a 4 % CSF content in Group III, which was 0.885Mpa, with the highest improvement rate of 127.38 %. The maximum fracture energy Gf reached 0.827 in the E3F4 specimen. However, another additive, EPS particles, did not significantly improve the physical and mechanical properties of concrete. According to the SEM images and toughening mechanism analysis, it was discovered that tight adhesion between EPS particles and CSF with cement matrix, and the failure mode of CSF was tensile fracture, which could maximize the effect of CSF high tensile toughness. On the basis of mechanical properties and toughening effect, the relationship formulas between variable factors and strength, toughness index were fitted, and the optimal content of EPS and CSF were determined to be 1.3 % and 3 %, respectively.

Coupling thermogalvanic and piezoresistive effects in a robust hydrogel for Deep-Learning-Assisted Self-Powered sign language and object recognition

Coupling thermogalvanic and piezoresistive effects in a robust hydrogel for Deep-Learning-Assisted Self-Powered sign language and object recognition

Oxygen solutes-regulated low temperature embrittlement and high temperature toughness in vanadium

Oxygen solutes-regulated low temperature embrittlement and high temperature toughness in vanadium

Cover Image, Volume 62, Issue 9

By adjusting the concentration of the solution of hyperbranched poly(o‐hydroxyamide)s and spin‐coating the solution on a silicon wafer, the ultrathin films could be obtained. After heating, the obtained ultrathin films could be converted to the corresponding polybenzoxazole ultrathin films, which have high thermal stability, good durability, and toughness. They are expected to find applications in various fields in the near future. The cover design was created by the first author, Mr. Hiroyuki Maekawa. DOI: 10.1002/pol.20230659 image

Dynamic tensile properties of a novel high strength and high toughness bolt steel: Constitutive models and Microstructures

Dynamic tensile properties of a novel high strength and high toughness bolt steel: Constitutive models and Microstructures

3D printed auxetic metal stiffener for lightweight metal–composite T-joints with high strength and toughness

A novel auxetic structure-based stiffener for stainless steel–carbon reinforced polymer (CFRP) T-joints with outstanding strength and toughness improvement is proposed. The stiffener was composed of a bulk web and re-entrant structure flange that was 3D printed using a selective laser melting 3D printer. The stiffener was bonded to a CFRP skin, and a pull-off test was performed to evaluate the pull-off strength, stiffness, and toughness of the joint. The results demonstrated that the proposed structure has specific strength and toughness that were 3.4 and 77 times greater than those of the baseline joint, respectively. The improvement in strength was due to the delayed damage initiation caused by the mismatch between the bending stiffness of the bulk web and the stiffener under the first re-entrant structure. However, the damage initiation in the baseline joint was located at the stiffener edge. Moreover, the negative Poisson's ratio of the re-entrant structure arrested the delamination growth after damage initiation, which enhances the toughness of the joint. By optimizing the structure of the stiffener, a joint with 2.66 and 38.2 times larger specific strengths and toughness compared to the baseline joint with the same specific stiffness was achieved.

MXene Crosslinked Hydrogels with Low Hysteresis Conferred by Sliding Tangle Island Strategy.

Single-network hydrogels are often too fragile to withstand mechanical loading, whereas double-network hydrogels typically exhibit significant hysteresis during cyclic stretching-releasing process due to the presence of a sacrificial network. Consequently, it is a considerable challenge for designing hydrogels that are both low in hysteresis and high in toughness for applications requiring dynamic mechanical loads. Herein, the study introduced a novel "sliding tangle island" strategy for creating tough and low-hysteresis hydrogels, which are prepared through in situ polymerization of highly concentrated acrylamides (AM) to form numerous entanglements within the MXene spacing without any chemical crosslinker. The MXene entangled with long polyacrylamide (PAM) chains to form tangle island that served as a relay station to transmit stress to neighboring molecular chains. This mechanism helps alleviate stress concentration and enhances energy dissipation efficiency, thereby reducing mechanical hysteresis. The resulting hydrogel exhibited exceptional properties, including high stretchability (≈900%), low hysteresis (less than 7%), high toughness (1.34MJm-3), and excellent sensing performance to rival the commercial hydrogel electrode. Therefore, this work sheds light on feasible design of energy dissipation structure to reduce the hysteresis of the composite hydrogels.

Recyclable and mechanically tough nanocellulose reinforced natural rubber composite conductive elastomers for flexible multifunctional sensor

The development of flexible wearable multifunctional electronics has gained great attention in the field of human motion monitoring. However, developing mechanically tough, highly stretchable, and recyclable composite conductive materials for application in multifunctional sensors remained great challenges. In this work, a mechanically tough, highly stretchable, and recyclable composite conductive elastomer with the dynamic physical-chemical dual-crosslinking network was fabricated by the combination of multiple hydrogen bonds and dynamic ester bonds. To prepare the proposed composite elastomers, the polyaniline-modified carboxylate cellulose nanocrystals (C-CNC@PANI) were used as both conductive filler to yield high conductivity of 15.08 mS/m, and mechanical reinforcement to construct the dynamic dual-crosslinking network with epoxidized natural rubber latex to realize the high mechanical strength (8.65 MPa) and toughness (29.57 MJ/m3). Meanwhile, the construction of dynamic dual-crosslinking network endowed the elastomer with satisfactory recyclability. Based on these features, the composite conductive elastomers were used as strain sensors, and electrode material for assembling flexible and recyclable self-powered sensors for monitoring human motions. Importantly, the composite conductive elastomers maintained reliable sensing and energy harvesting performance even after multiple recycling process. This study provides a new strategy for the preparation of recyclable, mechanically tough composite conductive materials for wearable sensors.

Ultra-Highly Stiff and Tough Shape Memory Polyurea with Unprecedented Energy Density by Precise Slight Cross-Linking.

Shape memory polymers (SMPs) have attracted significant attention and hold vast potential for diverse applications. Nevertheless, conventional SMPs suffer from notable shortcomings in terms of mechanical properties, environmental stability, and energy density, significantly constraining their practical utility. Here, inspired by the structure of muscle fibers, an innovative approach that involves the precise incorporation of subtle, permanent cross-linking within a hierarchical hydrogen bonding supramolecular network is reported. This novel strategy has culminated in the development of covalent and supramolecular shape memory polyurea, which exhibits exceptional mechanical properties, including high stiffness (1347MPa), strength (82.4MPa), and toughness (312.7MJm-3), ensuring its suitability for a wide range of applications. Furthermore, it boasts remarkable recyclability and repairability, along with excellent resistance to moisture, heat, and solvents. Moreover, the polymer demonstrates outstanding shape memory effects characterized by a high energy density (24.5MJm-3), facilitated by the formation of strain-induced oriented nanostructures that can store substantial amounts of entropic energy. Simultaneously, it maintains a remarkable 96% shape fixity and 99% shape recovery. This delicate interplay of covalent and supramolecular bonds opens up a promising pathway to the creation of high-performance SMPs, expanding their applicability across various domains.

Construction of multileveled and oriented micro/nano channels in Mg doped hydroxyapitite bioceramics and their effect on mimicking mechanical property of cortical bone and biological performance of cancellous bone

Drawing on the structure and components of natural bone, this study developed Mg-doped hydroxyapatite (Mg-HA) bioceramics, characterized by multileveled and oriented micro/nano channels. These channels play a critical role in ensuring both mechanical and biological properties, making bioceramics suitable for various bone defects, particularly those bearing loads. Bioceramics feature uniformly distributed nanogrooves along the microchannels. The compressive strength or fracture toughness of the Mg-HA bioceramics with micro/nano channels formed by single carbon nanotube/carbon fiber (CNT/CF) (Mg-HA(05-CNT/CF)) are comparable to those of cortical bone, attributed to a combination of strengthened compact walls and microchannels, along with a toughening mechanism involving crack pinning and deflection at nanogroove intersections. The introduction of uniform nanogrooves also enhanced the porosity by 35.4 %, while maintaining high permeability owing to the capillary action in the oriented channels. This leads to superior degradation properties, protein adsorption, and in vivo osteogenesis compared with bioceramics with only microchannels. Mg-HA(05-CNT/CF) exhibited not only high strength and toughness comparable to cortical bone, but also permeability similar to cancellous bone, enhanced cell activity, and excellent osteogenic properties. This study presents a novel approach to address the global challenge of applying HA-based bioceramics to load-bearing bone defects, potentially revolutionizing their application in tissue engineering.

Compressive Fracture Behavior of Zirconia/Resin Composites Prepared by Fused Deposition Modeling Combined with Vacuum Infiltration

Although bioceramic materials exhibit good biocompatibilities and bone conductivities, their high brittleness and low toughness properties limit their applications. Zirconia (ZrO2)/resin composites with idealized structures and properties were prepared by fused deposition modeling (FDM) combined with a vacuum infiltration process. The porous structure was prepared using the FDM three-dimensional printing technology, with granular zirconia as the raw material, and the relationship between the pore shape, pore size, and deformation was discussed. The results showed that square pores were more suitable than honeycomb pores for printing small pore sizes, and the resolution was high. Scanning electron microscopy observations showed that the superposition of multiple printing paths promoted the emergence of hole defects. The effects of the resin and the pore shape on the compressive strengths of the composites were studied. It was found that the compressive strengths of the honeycomb pore ZrO2/resin composites and porous ceramics were superior to those of the square pore samples. The introduction of the resin had a significant effect on the compressive strengths of the composites. The compressive strength increased in the direction perpendicular to the pores, while it decreased in the direction parallel to the pores.

Impact Toughness Dependent on Annealing Temperatures in 0.16C-6.5Mn Forged Steel for Flywheel Rotors

For the application of forged medium-Mn steels on flywheel rotors, the effect of annealing temperatures from 300 °C to 650 °C on the impact toughness of 0.16C-6.5Mn forged steel was investigated to demonstrate the microstructural characteristics and austenite reverse transformation determining the impact toughness. The results obtained through standard Charpy V-notch impact tests at ambient temperature show that the impact absorbed energy holds at lower than 10 J almost constantly at annealing temperatures of 300 °C to 500 °C, and a representative intergranular fracture is presented. At an annealing temperature of 600 °C, the impact absorbed energy increases to 147 J, with the ductile fracture characteristics showing plenty of fine dimples, and the high impact toughness is attributed to the high volume fraction above 30% and the moderate stability of reverted austenite. Subsequently, the annealing temperature rises higher than 600 °C, the impact absorbed energy decreases, and the fracture morphology shows brittleness characterized by more flat facets of intergranular fractures and small quasi-cleavage facets, presumably corresponding to the insufficient transformation and twinning-induced plasticity effect due to weakening the Mn partitioning from quenched martensite to reverted austenite, which results in lower austenitic stability. Furthermore, the ductile-to-brittle transition temperature (DBTT) of the 0.16C-6.5Mn forged steel annealed at 600 °C, which holds the highest impact absorbed energy, and is explored for the possibility of flywheel rotor application in a service environment. The DBTT reaches −21 °C, obtained through the Boltzmann function, and the impact absorbed energy is approximately 72 J.

Establishing superfine nanofibrils for robust polyelectrolyte artificial spider silk and powerful artificial muscles

Spider silk exhibits an excellent combination of high strength and toughness, which originates from the hierarchical self-assembled structure of spidroin during fiber spinning. In this work, superfine nanofibrils are established in polyelectrolyte artificial spider silk by optimizing the flexibility of polymer chains, which exhibits combination of breaking strength and toughness ranging from 1.83 GPa and 238 MJ m−3 to 0.53 GPa and 700 MJ m−3, respectively. This is achieved by introducing ions to control the dissociation of polymer chains and evaporation-induced self-assembly under external stress. In addition, the artificial spider silk possesses thermally-driven supercontraction ability. This work provides inspiration for the design of high-performance fiber materials.

Ultralight, shapeable, and superhydrophobic polyacrylonitrile/polybenzoxazine aerogel for high oil-water separation capacity

Environmental and human health are significantly threatened by oily wastewater emission and oil spills. Polymeric porous aerogels are ideal materials to absorb oils or organic solvents selectively, thereby mitigating environmental pollution and protecting human health. In this study, a shapeable, super-hydrophobic, polyacrylonitrile fiber/polybenzoxazine (PAN/PBOZ) aerogel with high oil-water separation ability were successful designed. The preparation process of PAN/PBOZ aerogel is as follows: Firstly, PAN micro-nanofibers were prepared by electrospinning, and then benzoxazine was uniformly dispersed into PAN fibers. After freeze-drying and thermal curing, the aerogel was obtained. For comparative analysis, a pure polyacrylonitrile (PAN) fiber aerogel is also presented. The resulting PAN/PBOZ aerogel exhibits ultralight (0.017 g/cm3), remarkable hydrophobicity, as evidenced by a water contact angle of 156°, high adsorption capacity up to 157.7 g/g for oil or organic solvents, and a high water-in-oil emulsion separation flux (9718 ± 45 L m−2 h−1) efficiently. Notably, the rigid cross-linking structure of PBOZ and the toughness structure of PAN make the aerogel exhibit synergistic strengthening and toughening effects. When the PAN/PBOZ fiber aerogel is compressed to 60 %, an outstanding recovery stability of its original size is displayed. While the springback of pure PAN fiber aerogel is poor under the same compression test condition. In conclusion, this study provides a preparation method and design concept of aerogel that can meet the requirements of low density, high toughness and high oil adsorption capacity. The rationally designed PAN/PBOZ aerogel shows significant potential for practical applications in treating oily and organic wastewater.

Effect of Al and Nb addition on the precipitation hardening and deformation mechanism of CoCrNi medium entropy alloy

Single-phase medium-entropy alloys (MEAs) with face-centered cubic (fcc) structure exhibit high elongation and toughness but suffer from insufficient strength. In this work, two novel (CrCoNi)Al4 and (CrCoNi)Al4Nb2 MEAs were designed with the aim of introducing precipitation hardening effect and thus improve strength of the alloys. It was revealed that addition of Al alone, only slightly increased the strength, but the elongation decreased severely. Conversely, the combination of Al and Nb can significantly increase strength and maintain acceptable elongation. The Al addition promotes the formation of a disperse distribution of BCC/B2 composite precipitates, however, the large size and incoherent nature of these composite precipitates produce minor hardening response. Except for the BCC/B2 composite precipitates, a high density of the nanoscale γ′ phase with L12 structure and stoichiometry of (Ni, Co, Cr)3(Al, Nb) is produced in the Al4Nb2 MEA, which significantly increases the strength of the alloy. After the addition of Al and Nb, the deformation mechanism of the alloys is changed from nanotwins to stacking fault (SF) dominated plasticity. Such phenomenon mainly relates to the increasing critical twinning stress affected by the channel width of the matrix. This study provides new insight for the composition design of precipitation-hardening MEAs.

Super-Toughness Carbon Nanotube Yarns by Bio-Inspired Nano-Coiling Engineering.

Lightweight structural materials are commonly used as effective fillers for advanced composites with high toughness. This study focused on enhancing the toughness of direct-spun carbon nanotube yarns (CNTYs) by controlling the micro-textural structure using a water-gap-based direct spinning. Drawing inspiration from the structural features of natural spider silk fibroin, characterized by an α-helix in the amorphous region and β-sheet in the crystalline region, multiscale bundles within CNTYs are reorganized into a unique nano-coil-like structure. This nano-coiled structure facilitated the efficient dissipation of external mechanical loads through densification with the rearrangement of multiscale bundles, improving specific strength and strain. The resulting CNTYs exhibited exceptional mechanical properties with toughness reaching 250Jg-1, making them promising alternatives to commercially available fibers in lightweight, high-toughness applications. These findings highlight the significance of nano-coiling engineering for emulating bio-inspired micro-textural structures, achieving remarkable enhancement in the toughness of CNTYs.