Ultrahigh Mechanical Properties Research Articles

Assessing the combination of graphene and graphene oxide nanosheets in cement-based materials

Graphene (Gr) and Graphene Oxide (GO) are graphene-based nanosheet (GNS) materials with ultrahigh mechanical properties. The addition of Gr/GO (from 0.01 % to 2 % in mass) to a cement-based material can significantly enhance its mechanical properties. GO has higher efficiency than Gr, but it is more costly. In this paper, a Gr-GO solution was developed by combining Gr and GO in water. The compressive strengths of the samples with and without Gr-GO were determined. Deep analyses were performed by applying several imaging techniques such as nano-tomography, SEM, and confocal Raman imaging to exploit the correlation between microstructural properties and mechanical properties and durability of cement-based materials. The microstructural properties were also quantified from the 3D images obtained by nano-tomography. The results showed that the GNS-added sample had a higher porosity (about 12.4 %) than that of the reference sample (about 6.1 %) but the GNS-added sample had a more homogeneous distribution of micropores. Raman imaging results explained the formation of hydration product and acceleration of hydration rate by Gr-GO in GNS-added samples. The mechanical properties showed that the addition of 0.03 % Gr-GO could increase the compressive strength of mortar samples by 28 %.

The effect of pre-heat parameters and final-heat parameters on microstructure evolution and mechanical properties of Mg-Gd-Y-Zn-Zr alloy

In this study, an ultra-high strength Mg-13Gd-4Y–0Zn-0.5Zr (wt.%) alloy with tensile yield strength (TYS) of 456 MPa and ultimate tensile strength (UTS) of 486 MPa was prepared by using different pre-heat parameters and subsequent final-heat treatment combined with backward extrusion (BE) deformation process. It was shown that the pre-heat teratment could significantly enhance the UTS and TYS of the secondary backward extruded (BEed) alloy compared with none treatment. The reason was that the pre-heat treatment promoted the particle stimulated nucleation (PSN) mechanism and continuous dynamic recrystallization (CDRX), significantly increasing the fraction of dynamic recrystallization (DRX). The strengthening of the secondary BEed alloy was attributed to the unique microstructure characteristics: (I) the fine DRXed grains pinned by dynamic precipitates, (II) the dense dynamic precipitation phases, (III) the effect of the fine-grain strengthening. However, the overly densely distributed second phase, which increased the local dislocation density due to the narrower spacing, made it difficult to prevent crack propagation and caused premature fracture of the alloy. In addition, the subsequent final-heat treatment also facilitated the precipitation of the second phases of the secondary BEed alloys and brought in the ultra-high mechanical properties.

Surface engineered covalent bridging strategy to in-situ fabricate MXene-based core-sheath fiber for flexible supercapacitors with ultrahigh volumetric energy density and mechanical properties

MXene fiber-based supercapacitors (SCs) are expected to make a major contribution to the ongoing development of wearable electronics and metaverse technologies in future. However, to fabricate fiber electrodes with high energy density and strong mechanical properties remains a major challenge for their usage in SCs. Herein, we fabricated a flexible core-sheath structural Ti3C2Tx MXene@polyaniline (MX@PA) fiber electrode with ultrahigh volumetric energy density and good tensile strength through surface engineered covalent bridging strategy via wet spinning and in situ oxidant-freepolymerization processes. Benefiting from the high-order core-sheath structure and strong Ti-O-N covalent bonds between MXene and PANI, an ultrahigh tensile strength (∼168.1 MPa) and super-toughed (∼1.75 MJ cm−3) fiber electrode was achieved. The assembled SC provided much higher volumetric capacitance of 631F cm−3 (based on the SC device) at a current density of 0.5 A cm−3 and ultralong-term cycling stability with 92.6 % capacitance retention after 10000 cycles due to the rapid electron conduction of core (MXene) and large pseudocapacitive charge transfer of the sheath (PANI). As a result, the SC delivers excellent volumetric energy density of 56.1 mWh cm−3 at a power density of 204.9 mW cm−3. The integrated SC found actual application to power a 2.5 V red LED.

Micro-structure evolution, precipitation behavior and strengthening mechanism of Ni-Cr-Mo system steel fabricated via laser powder bed fusion and subsequent quenching control

High-performance 24CrNiMo steel was fabricated using Laser Powder Bed Fusion (LPBF). Subsequent quenching treatment was applied and the influence of quenching temperatures on micro-structure evolution and properties was systematically characterised and analysed. The micro-structure of the as-built steel consisted of two parts. The first part comprised martensite with twins combined with ω-Fe nano-particles, and the second part consisted of lower bainite in the molten pool, as well as upper bainite, granular bainite and tempered martensite in the heat-affected zone. With the quenching temperatures varying from 800 °C to 950 °C, the micro-structure gradually transformed from acicular ferrite + martensite to tempered martensite +θ-Fe3C carbides, and the grain size exhibited noticeable growth. Moreover, quenching treatments could eliminate the anisotropy and inhomogeneity of the micro-structure. The rod-shaped nanosized η-Fe2C and θ-Fe3C precipitates were clearly observed, which were converted from ω-Fe and distributed at multiple angles in the lath. The size and number of nano-precipitates, triggered by the high self-tempering degree of martensite, gradually increased. The relationships among grain size, the twins, dislocation density and nano-precipitation and the dramatically improved performance of quenched samples were analysed using strengthening mechanisms. After quenching at 850 °C, the as-built 24CrNiMo steel attained ultra-high mechanical properties including hardness, Ultimate Tensile Strength (UTS), Elongation (El) and impact energy with values of 480.9 HV1, 1611.4 MPa, 9.8% and 42.8 J, respectively. Meanwhile, both the wear and thermal fatigue resistance increased by approximately 40%. This study demonstrated that LPBF-fabricated 24CrNiMo steel, with matching good performances, can be achieved using a subsequent one-step quenching process.

Filler-size matching strategy for highly thermal-conductive insulating BN/PMIA composite paper

PMIA paper has received intensive interests because of its ultrahigh mechanical properties and insulating potential as an ideal packaging material for electrical and electronic devices. However, its low thermal conductivity arouses the risk of heat breakdown. In this study, the filler-size matching strategy is proposed by combining micro- and nano-scale BN fillers for the preparation of BN/PMIA composites. 15 wt% BN/PMIA composites have better thermal conductivity and breakdown strength than PMIA and each parameter could be pertinently improved by adjusting the matching ratio. The enhanced thermal conductivity of 205% is achieved at micro-BN dominated composites by constructing an effective heat flow pathway. The breakdown strength is increased by 48% in the composites governed by nano-BN, which acts as the scattering center for the electron transport that impedes the discharge process. Wet-laid PMIA composite papers can be tailored by matching filler sizes to achieve either high thermal conductivity or excellent insulation strength while maintaining stable mechanical performance. Assisted with the theoretical studies, our results provide a deeper understanding of the filler-size matching strategy in the polymer matrix.

Facile Preparation of Irradiated Poly(vinyl alcohol)/Cellulose Nanofiber Hydrogels with Ultrahigh Mechanical Properties for Artificial Joint Cartilage.

In this study, Poly(vinyl alcohol)/cellulose nanofiber (PVA/CNF) hydrogels have been successfully prepared using γ-ray irradiation, annealing, and rehydration processes. In addition, the effects of CNF content and annealing methods on the hydrogel properties, including gel fraction, micromorphology, crystallinity, swelling behavior, and tensile and friction properties, are investigated. Consequently, the results show that at an absorbed dose of 30 kGy, the increase in CNF content increases the gel fraction, tensile strength, and elongation at break of irradiated PVA/CNF hydrogels, but decreases the water absorption. In addition, the cross-linking density of the PVA/CNF hydrogels is significantly increased at an annealing temperature of 80 °C, which leads to the transition of the cross-sectional micromorphology from porous networks to smooth planes. For the PVA/CNF hydrogel with a CNF content of 0.6%, the crystallinity increases from 19.9% to 25.8% after tensile annealing of 30% compared to the original composite hydrogel. The tensile strength is substantially increased from 65.5 kPa to 21.2 MPa, and the modulus of elasticity reaches 4.2 MPa. Furthermore, it shows an extremely low coefficient of friction (0.075), which suggests that it has the potential to be applied as a material for artificial joint cartilage.

Autonomous self-healing strategy for flexible fiber lithium-ion battery with ultra-high mechanical properties and volumetric energy densities

The development of wearable devices urgently requires flexible, lightweight, and high-performance power solutions. Flexible fiber batteries are flexible and deformable, which holds great potential in this field. However, it still face significant challenges in achieving excellent electrochemical performance and good mechanical properties. Herein, we developed a new method for preparing flexible fiber lithium-ion batteries by surface etching and in-situ chemical cross-linking strategies using direct ink writing-based 3D printing technology. On the one hand, the surface of graphene oxide undergoes oxidation and etching to form pores. This unique pore structure provides additional channels for ions, which increases the ion transmission rate. On the other hand, polyvinyl alcohol/sodium metaborate is introduced into the printing ink/coagulation bath. In-situ chemical cross-linking occurs during the printing and curing process, which exhibits self-healing properties. The flexible fiber electrode has excellent strain (∼30 %) at the macro level, and the assembled fiber lithium-ion battery exhibits impressive volumetric energy density (157.9 mWh cm−3), which exceeds previously reported flexible fiber batteries. And it is also integrated into wearable smart watches for use in daily life. This work proposes an innovative method to fabricate high-performance flexible fiber electrodes, which is of great significance for promoting the development of future portable/wearable electronics.

Selected challenges in solidification processing of graphene nanoplatelets (GNPs) reinforced aluminum alloys composites

Solidification processing of aluminum graphene composite is an attractive option for synthesis of metal matrix composites. Graphene reinforced aluminum metal matrix composites (GAMMCs) are of interest due to the low density and ultrahigh physical and mechanical properties of Graphene which can improve the properties of Al-Graphene composites. However, solidification processing of aluminum graphene composites has served challenges, including agglomeration of reinforcement and porosity resulting in decrease in properties above 0.five to three wt% graphene. Also, the graphene surface can react with molten aluminum alloys to form aluminum carbide. Challenges with particle distribution and porosity are frequently caused by the poor wetting of reinforcement by melt, requiring additions of selected wetting agents. The other problems include movement of reinforcement within the melt due to density differences and convection leading to nonuniform distribution of reinforcements. The graphene reinforcements can be pushed by solidifying interfaces under certain conditions during solidification leading to segregation of reinforcements in the interdendritic regions. The paper critically analyzes the above problems related to solidification processing of Aluminum- Graphene composites which has not been done in previous publications aluminum-graphene composites. The objective of this paper is to examine the challenges, and suggest possible solutions including addition of elements like silicon and magnesium to aluminum melt, coating graphene with metals like nickel and copper, controlling rate of advancement and nature of advancing solid liquid interface in a manner that they engulf graphene with dendrites or grains.

Extremely sensitive mechanochromic photonic hydrogels with ultrahigh mechanical properties for multicolor displays by naked eyes

Photonic soft materials, especially responsive photonic hydrogels (RPHs) with periodic permittivity on the submicroscale, have been garnering interest as colorimetric indicators and mechanochromic sensors. However, the fabrication of RPHs with both bright discoloration, satisfactory mechanical properties, and excellent mechanochromic sensitivity to meet the practical applications is still a great challenge. Herein, we develop a novel photonic crystal material using a Fe3O4 array embedded poly(N-isopropylacrylamide-co-acrylamide)/ laponite-XLS (PNA-XLS) hydrogel, which is dual-cross-linked by chemical and physical cross-linkers. Due to the interaction of sparse chemical links and apposite physical links between the polymeric networks, the PNA-XLS exhibits a significant energy dissipation and high deformation capacity, with an enhanced tensile strength above 819 kPa and elongation above 1015 %. It almost has a full-color tunable range and shows bright discoloration that can be reversibly actuated by bending, stretching, and small pressures (Pa level), with extremely high sensitivities of pressure (161 nm kPa−1) and tension (1.52 nm %−1). Moreover, its self-adhesion (133 kPa) would make it be an appealing candidate to develop portable sensors or wearable devices without auxiliary adhesive tools. Besides, elastic hydrogels with programmable and multicolor patterns can be designed by the mask-assisted UV photopolymerization of regional pregel solution. Therefore, such hydrogel has a great application potential in colorimetric indicators, mechanochromic sensors, anti-counterfeiting and wearable devices.

Enhanced mechanical properties of continuous carbon fiber reinforced polyether-ether-ketone composites via infrared preheating and high fiber volume fraction

The field of additive manufacturing encounters an innate challenge regarding insufficient interlayer adhesion and anisotropy, which consequently constrains the mechanical properties of printed materials. Continuous fiber-reinforced thermoplastic composite (CFRTP) printing allows ultra-high mechanical properties using a material extrusion (ME) platform but is still significantly affected by the mentioned inherent challenges. The expansion of the usage spectrum for composites manufactured with additive methods depends on overcoming these challenges. Achieving higher fiber volume fractions is a primary method for enhancing the mechanical properties of CFRTP parts. However, it has been proven that high fiber volume fractions can adversely affect mechanical properties due to lower impregnation and reduced interlayer strength. In this study, a high fiber volume fraction of 50 % was utilized, and interlayer strength was further improved by employing an infrared heater to preheat the previous layers. This approach resulted in better interlaminar strength and overall mechanical properties, demonstrating the effectiveness of infrared heating in mitigating the challenges associated with high fiber volume fractions. The infrared heater was positioned in a rotating printing head so it could continuously stay in front of the print path. Mechanical tests showed a flexural strength of 1304 MPa and tensile strength of 995 MPa, with high fiber volume fraction and infrared assistance. As far as we know, these values represent the highest achieved in the literature for CFRTP printing without any post-processing. Optical images and differential scanning calorimeter (DSC) tests were used to investigate the microstructure and thermal properties of the printed samples.

Supramolecular metallic foams with ultrahigh specific strength and sustainable recyclability

Porous materials with ultrahigh specific strength are highly desirable for aerospace, automotive and construction applications. However, because of the harsh processing of metal foams and intrinsic low strength of polymer foams, both are difficult to meet the demand for scalable development of structural foams. Herein, we present a supramolecular metallic foam (SMF) enabled by core-shell nanostructured liquid metals connected with high-density metal-ligand coordination and hydrogen bonding interactions, which maintain fluid to avoid stress concentration during foam processing at subzero temperatures. The resulted SMFs exhibit ultrahigh specific strength of 489.68 kN m kg−1 (about 5 times and 56 times higher than aluminum foams and polyurethane foams) and specific modulus of 281.23 kN m kg−1 to withstand the repeated loading of a car, overturning the previous understanding of the difficulty to achieve ultrahigh mechanical properties in traditional polymeric or organic foams. More importantly, end-of-life SMFs can be reprocessed into value-added products (e.g., fibers and films) by facile water reprocessing due to the high-density interfacial supramolecular bonding. We envisage this work will not only pave the way for porous structural materials design but also show the sustainable solution to plastic environmental risks.

Experimental study on bond performance of staggered lap rebars in ultra-high performance concrete (UHPC)

Ultra-high performance concrete (UHPC) has received extensive attention worldwide due to its ultra-high mechanical properties and durability. The bond performance between steel bars and UHPC is crucial for the design of Reinforced-UHPC structures. To study the bond performance of overlapping steel bars in UHPC, a total of 13 groups of 39 pull-out tests were conducted with overlapping lengths, cover thickness, steel bar diameter, and clear spacing of steel bars as influencing variables in this study. According to the results, when the lap length increased from 4 times the bar diameter (4db) to 5db and 6db, the maximum bond strength decreased by 10% and 20%, respectively. Moreover, with an increase in the cover thickness from 25 mm to 35 mm and 45 mm, the maximum bond strength increased by 6% and 14%, while the residual bond strength increased by 15% and 48%, respectively. When the diameter of the reinforcing bars increased from 16 mm to 20 mm and 25 mm, the ultimate load capacity increased by 50% and 70%, respectively, while the bond stress decreased by 16% and 27%. Additionally, the bond strength showed less sensitivity to the clear spacing of steel bars, with a decrease of 3% and 10% in bond strength when the clear spacing increased from 1.5db to 2db and 3db, respectively. The ductility of the specimen decreases when the bar diameter or the clear distance between bars is too large. A theoretical calculation formula for splitting bond strength was established, which yielded accurate results. Furthermore, a bond-slip model was fitted based on the test results, providing reference for finite element analysis of steel bar-UHPC structures.

Multi-component 20La2O3–20TiO2–20Nb2O5-20(Al2O3/ZrO2)-20(ZrO2/Ta2O5) glasses with ultra-high refractive index and mechanical properties inspired by high-entropy design

The highly refractive glasses with excellent mechanical properties (hardness, Young's modulus, and fracture toughness) are highly desired for the lenses used in small optical devices. In this study, a series of five-primary-component 20La2O3–20TiO2–20Nb2O5-20(Al2O3/ZrO2)-20(ZrO2/Ta2O5) (LTNAZ, LTNAT, LTNZT) glasses were designed by using high-entropy strategy and successfully elaborated through a containerless melting-solidification process. The highest refractive index (nd) of the glasses reach up to 2.25. The maximum vickers hardness (HV), Young's modulus (E), and indentation fracture toughness (KIFT) are 10.74 GPa, 157.5 GPa, and 1.23 MPa m0.5 respectively. The glasses exhibit good glass forming ability with kinetic window (ΔT) ranging from 80 to 116 °C. The excellent comprehensive performances of the glasses are attributed to the high electronic polarizability and dissociation energy, as well as the synergistic effect of multiple components in the high-entropy effect. The glasses will be promising host materials for optical applications such as digital product lenses, endoscopes and mini size lasers.

Dislocation-mediated ultrahigh mechanical properties in nano-TiN

Dislocation-mediated ultrahigh mechanical properties in nano-TiN

High-temperature tensile strength of C/SiC composite under laser-induced high heating flux in an aerobic environment

Based on the advantages of laser high brightness, a high-temperature mechanical property measuring device has been developed, which can measure the high-temperature strength of C/SiC composites under the condition of short-term high-temperature rise rate and solve the problem of over-oxidation of materials in conventional high-temperature mechanical properties experiments. The experimental results show that the maximum temperature rise rate is 260 ℃/s at the initial heating stage, and the test time is controlled within 35 s. The tensile strength of the prepared C/SiC composites decreased first and then increased at high temperatures and laser-induced high temperatures. The experimental results are similar to those in the literature under the inert atmosphere. Oxidation has less of an effect on the mechanical characteristics of materials under conditions of rapid temperature rise. The system can be used to test the mechanical properties of composite materials at high temperatures and as a simulation platform for the thermal response of specific thermal protection systems subjected to a constant heat flux. This study can provide a new idea for testing ultra-high temperature mechanical properties of C/SiC materials and provide key technical support for the engineering application and high-temperature testing of C/SiC materials in high-temperature environments.

A fluoride gradient, Zn-salt-rich hydrophobic interphase formed by a zincophilic, hydrophobic, anion-philic polymer “skin” for an anode-free solid Zn battery

A Zn2+·OC group-derived contact ion pair (CIP)/aggregate (AGG)-rich electrolyte is fabricated to generate a fluoride gradient, Zn-salt-rich hydrophobic solid electrolyte interface (SEI) layer with ultrahigh mechanical properties.

Elastomers with ultrahigh mechanical properties for flexible sensing and triboelectric nanogenerators

With the continuous development of technology, flexible wearable electronic devices have received widespread attention. However, flexible substrate materials with high strength and toughness and flexible stretchable electrode materials that can meet practical needs are still full of challenges. Here, we successfully prepared elastomeric substrate materials with high tensile strength (30.95 MPa), high toughness (134.16 MJ/m3), solvent resistance and puncture resistance by modulating the reaction conditions of maleic anhydride and polystyrene-b-polybutadiene-b-polystyrene. Subsequently, the preparation of flexible and stretchable electrodes was achieved by mixing an elastomeric substrate with carbon nanotubes. The capacitive sensor designed and assembled based on this stretchable electrode has fast response characteristics and can be used for human movement detection. Additionally, the triboelectric nanogenerator (TENG) fabricated using this material for the friction layer exhibits a high open-circuit voltage of 848 V along with a short-circuit current of 20 μA. Its excellent stability is evidenced by its ability to withstand up to 10,000 cycles, and it also possesses an impressive power density of 3.8 W/m2. These characteristics provide a solid foundation for advancing research in intelligent sensing technologies and lay the groundwork for its future incorporation into energy-harvesting devices.

Mechanical and fatigue properties of graphene oxide concrete subjected to sulfate corrosion

Concrete structures usually have to experience some unfavorable environmental actions during their service life, leading to the mechanical properties degradation, moreover, cyclic loadings such as traffic loads, wind loads may further accelerate structural damage, therefore, improving durability of concrete is of vital for structures servicing in severe environment. Graphene oxide (GO), as a new nano-reinforced material, has ultra-high mechanical properties and large specific surface area as a concrete reinforcing material. This study entailed an examination of the properties of Graphene Oxide Concrete (GOC) with varying levels of GO incorporation (0, 0.02, 0.05, 0.08 wt%). It also encompassed an analysis of the fatigue properties of GOC under different stress levels and varying sulfate wetting and drying cycles. Additionally, the investigation delved into the degradation mechanisms affecting Graphene Oxide Concrete (GOC) when subjected to sulfate erosion conditions. Furthermore, the study assessed the mass loss of specimens and their fatigue life under diverse environmental conditions. The results showed that appropriate GO incorporations could enhance concrete’s mechanical and fatigue properties after sulfate attack. In addition, scanning electron microscope (SEM) analysis showed that GO could adjust the aggregation state of cement hydration products and its own reaction with some cement hydration crystals to form strong covalent bonds, to improve and enhance microstructural denseness.

Achieving ultra-high mechanical properties in metastable Co-free medium entropy alloy via hierarchically heterogeneous microstructure

A new metastable dual-phase Fe59Cr13Ni18Al10 medium entropy alloy (MEA) with hierarchically heterogeneous microstructure from micro- to nano-scale was designed in this work. Partially recrystallized FCC phase and lots of NiAl-rich B2 precipitates are obtained by annealing and aging treatment. The yield strength of the MEA at room temperature (298 K) and liquid nitrogen temperature (77 K) increased from ∼910 MPa and ∼1250 MPa in the annealed state, respectively, to ∼1145 MPa and ∼1520 MPa in the aged state, while the uniform elongation maintained more than 15%. The excellent mechanical properties of the MEA both at 298 and 77 K are attributed to the co-activation of multiple strengthening mechanisms, including fine grain, dislocation, precipitation, transformation-induced plasticity, stacking faults, and nano-twins.

Ultra-high strength and high toughness 24CrNiMo alloy steel fabricated by laser powder bed fusion and subsequent quenching

A nearly fully dense grade 24CrNiMo alloy steel with superior comprehensive performance was fabricated by laser powder bed fusion (LPBF) under optimum laser parameters and subsequent quenching treatment was applied. The effect of quenching temperatures on microstructure evolution and mechanical properties of the LPBF 24CrNiMo parts were first systematically characterized and analyzed. The results demonstrated that the microstructure of LPBF 24CrNiMo steel (submicron grain size of 2.99 μm on average) was mainly constituted by block and stripe granular bainite containing twin substructure and θ-Fe3C carbides with no macroscopic segregation and anisotropy. After quenching, with the increase of quenching temperature from 800 to 1000 °C, the microstructure gradually changed from the acicular ferrite to martensite, finally to tempered martensite. The fine grains, the numerous twins were retained and the nanoscale carbides η-Fe2C were precipitated after quenching at 850 °C, simultaneously obtaining ultra-high mechanical properties including the hardness, yield strength, ultimate tensile strength and elongation were 446 HV and 1380 MPa, 1517 MPa, 13.8 %, respectively as well as the surface scratch resistance improved about 25 %. As quenching temperatures varied to 1000 °C, the mechanical properties lowered due to the coarsening and uneven distribution of the grain and θ-Fe3C carbides as well as the decrease in the number of twins. The improved mechanical properties via quenching treatment was attributed to phase transformation strengthening, grain refinement strengthening and precipitate strengthening.