Elastic Strain Limit Research Articles

Tough and elastic hydrogel thermocells for heat energy utilization

Hydrogel thermocells possess great potential in the energy conversion field as they directly absorb waste heat from the environment to drive redox reactions for continuous electricity generation. However, achieving high toughness and good elasticity simultaneously in hydrogel thermocells remains a challenge because of the inherent contradiction of energy dissipation mechanisms, severely limiting their practical applications and lifespan. To address this, a skin-like hydrogel network with a highly dense interwoven network is developed to construct hydrogel thermocells with good elasticity and high toughness. The dense network structure can effectively disperse the stress and hinder crack propagation, thus breaking the contradiction between high toughness and good elasticity. The thermocell realizes a toughness of 460 J m−2 while reaching an elastic limit strain of 350 %, far exceeding the elasticity of previous stretchable hydrogel thermocells. Meanwhile, it exhibits ultra-low hysteresis and excellent fatigue resistance under tensile and compressive cyclic loads. Moreover, the thermocell can work stably over long periods, enabling stable voltage output even under compression, bending, and stretching. In addition, the thermocell can power the LED lamp and calculator, and can also be connected in series to form large arrays, thus rendering it an ideal power source for wearable devices.

In-situ failure behavior and interfacial bonding of an interpenetrating metal matrix composite reinforced with lattice-like metallic glass (Ni60Nb20Ta20) preform

Metallic glasses (MG) have an amorphous atomic structure and exhibit several exceptional properties such as high strength, hardness associated with high elastic strain limit and elastic energy storage. But MGs are also prone to brittle fracture, making them difficult to use as monolithic structural components and might better be used as a reinforcement phase in hybrid composites such as metal matrix composites (MMC). The failure behavior of composites depends on the structure of the reinforcement phase. In this work, the failure behavior of an interpenetrating MMC reinforced with a MG (Ni60Nb20Ta20) lattice-like preform and AlSi12-matrix was investigated by in-situ compression tests under scanning electron microscopy to get a better understanding of the influence of the lattice-like preform and mechanical interference between both phases. Additionally, microstructure analysis by scanning transmission electron microscopy and energy dispersive X-ray measurements were carried out to gain insight into the chemical composition of the interfaces. The failure behavior in manufacturing direction of the MMC is dominated by shear stress whereas transversely to manufacturing direction by normal stress and exhibits therefore an anisotropic failure behavior. Investigations of the interfaces show more of a mechanical than chemical bonding but in general a good interfacial bonding was confirmed.

Flexible Mini‐Inductors with Ultra‐High Inductance Density Directly Cut from Soft Magnetic Amorphous Alloys by Femtosecond Laser

AbstractInductors are indispensable parts in power modules of electronic devices. With the rapid development of flexible and wearable electronic devices, developing flexible micro‐inductors with large energy storage has become an urgent task. In this research, a sophisticated femtosecond laser ablation technique is employed to craft circular spiral mini‐inductors via selective etching of soft magnetic amorphous alloy ribbons. Remarkably, while these inductors possess dimensions akin to human fingerprints, they demonstrate an impressively elevated inductance value of ≈1.15 µH at 1 MHz. The inductance density is ≈280–390 nH mm−2, which is ≈10 times larger than conventional circular spiral inductors and is attributed to the high permeability of the amorphous alloys. Furthermore, the inductors showcase commendable flexibility, marked by stellar elasticity and a bending endurance exceeding 2500 cycles, thanks to the amorphous alloys' superior elastic strain limit. When integrated with an LM2576‐3.3BT buck converter, the fabricated inductor achieved a peak power conversion efficiency nearing 70%. These findings underscore the potential of such flexible mini‐inductors in the landscape of flexible electronics.

Determining fatigue threshold of elastomers through an elastic limit strain point.

Determining the fatigue threshold of elastomers is particularly important to predict their durability and lifespan. However, there has been almost no effective approach to calculate this threshold fast and accurately so far. To realize rapid fatigue performance testing, in this paper, a new method is proposed to calculate the fatigue threshold through the elastic limit strain point of elastomers that can be obtained from the continuous Mullins test. Compared with the traditional binary method to predict fatigue threshold, this method significantly reduces the time required for fatigue testing of elastomers, which can save approximately 2-3 sampling points in the fatigue test, i.e. a time savings of around 40%. Our method also proved to be effective for the elastomers at 0 °C. Additionally, a dual-network elastomer was synthesized using the interpenetrating network method, exhibiting improved elasticity (2.1 MPa and 3.1 MPa), toughness (1423 J m-2 and 2100 J m-2), and higher fatigue threshold (125 J m-2 and 385 J m-2) at 0 °C and room temperature. This material presents great application potential in marine anti-fouling.

Cyclic load behaviour of reinforced concrete columns with SMA and ECC in the critical regions

Design techniques that can reduce the residual deformation are necessary to ensure that reinforced concrete (RC) structures function properly after earthquakes. The use of superelastic materials in the plastic hinge region permits the structure to undergo large displacements with less residual displacement upon load removal. The present study deals with the incorporation of two innovative materials, super-elastic shape memory alloy (SMA) and engineered cementitious composites (ECC), in the critical region or plastic hinge zone of the column. This numerical study focused on the seismic performance evaluation of full-scale RC circular cantilever columns reinforced with two types of nickel-based and two iron-based SMA and ECC in the critical region. The specimens were subjected to a reverse cyclic lateral loading with a constant axial load at the top. The performance of these hybrid columns was compared with those of conventional steel-reinforced columns and steel-reinforced columns with ECC in the critical region. The results of the study revealed that the columns reinforced with SMA and ECC in the critical region showed negligible residual displacement compared to the normal and ECC columns. The column reinforced with the FeNCATB SMA and ECC in the critical region showed better behaviour in terms of a higher load-carrying capacity and ultimate displacement/rotation under a higher drift ratio. From the longitudinal rebar strain profile, it is evident that this hybrid column specimen did not reach the elastic strain limit at a higher drift ratio than the other specimens.

Manufacturing and characterization of an interpenetrating metal matrix composite reinforced with a 3D-printed metallic glass lattice structure (Ni60Nb20Ta20)

Metallic glasses (MG) exhibit remarkable properties, like high strength, hardness, and elastic strain limit due their amorphous structure. But they also exhibit low ductility and brittle behavior, making them less suitable for monolithic components. Therefore, MG offer high potential for use as a reinforcing phase in a ductile matrix. Especially interpenetrating metal matrix composites (MMCs) are suitable, since good interfacial adhesion can be achieved due to the metallic character of the MG and mechanical properties can be further enhanced by the interpenetrating structure. Temperature during manufacturing process must be below crystallization temperature of the MG. Until now, interpenetrating MMCs have been manufactured by infiltrating the metal matrix foam with MG, requiring a high melting temperature of the matrix and thus excludes lightweight metals. In this work it was possible to infiltrate an open porous lattice structure of MG (Ni60Nb20Ta20) due to its high crystallization temperature with AlSi12 by gas pressure infiltration resulting in a novel MMC. X-ray diffraction measurements confirm that no crystallization occurred during infiltration. Micrographs show a good infiltration quality and interfacial bonding between both phases. An increase in Young's modulus of 28 % and compressive strength in the MMC can be achieved compared to the AlSi12-matrix.

Orientation-dependent extreme shear strain in single-crystalline silicon - from elasticity to fracture

Measuring strain accurately at small length scales poses a significant challenge, making it difficult to obtain precise elastic properties of small materials. This becomes particularly pronounced for test geometries beyond micro-pillars and for materials with high elastic limits and high Peierls stresses. This study investigates the elastic strain limits and strain distribution in micro double shear tests conducted on single-crystalline silicon with different crystallographic orientations. In situ scanning electron microscopy images were used to obtain full-field strain maps using digital image correlation. This local strain analysis approach revealed that the shear zones of the test geometry are not solely under pure shear conditions, but also experience superimposed bending. The local strain analysis approach increases the precision of measured elastic properties to ±15% of the literature value compared to deviations of 75-80% using the traditional global strain analysis approach. This study highlights the limitations of the global strain analysis approach in complex specimen geometries and demonstrates the effectiveness of digital image correlation in accurately determining elastic strain at the small length scale. Furthermore, both the low defect density in the samples as well as the small length scales allow for the exploration of orientation dependent strength levels close to the theoretical limit.

A scheme for achieving strength-ductility trade-off in metallic glasses

The strength-ductility paradox in structural materials remains a long-standing dilemma in advanced materials synthesis. Metallic glasses (MGs) that are structural materials of remarkably high-strengths are not exclusive in structural applications due to their inherently poor plasticity. This study addresses this conundrum by presenting a scheme for achieving excellent strength-ductility synergy in MGs from structural and energetic standpoints. By applying a two-step pathway of mechanical rejuvenation and cyclic stress loadings upon a Zr2Cu as-constructed MG model, deformation behavior was analyzed by molecular dynamics simulations. As higher energy states of the MG characterized by enhanced compressive plasticity was found by mechanical rejuvenation due to internal stress accumulation accompanied with an unusual increase in free volume and atomic energy, cyclic stress loading upon rejuvenation annihilated loosely-packed regions to advance a more stable state with less energy to enhance structural stability with an improvement in elastic strain limit and strength. By theoretical modelling, strength-ductility trade-off was demonstrated by the delay in shear transformation zone activities that orchestrated the generation and intersection of multiple shear bands. As a result, a two-step scheme in which soft regions are aggregated to a concentered mass intensified to higher potential energy followed by dissipating the consolidated mass into randomly dispersed soft regions is the key to achieve the strength-ductility trade-off in MG materials. The outcome of this study will further advance structure-property characterization in amorphous solids.

TiNbN Hard Coating Deposited at Varied Substrate Temperature by Cathodic Arc: Tribological Performance under Simulated Cutting Conditions.

This study focused on investigating the adhesion and tribological properties of niobium-doped titanium nitride (TiNbN) coatings deposited on D2 steel substrates at various substrate temperatures (Ts) under simulated cutting conditions. X-ray diffraction confirmed the presence of coatings with an FCC crystalline structure, where Nb substitutes Ti atoms in the TiN lattice. With increasing Ts, the lattice parameter decreased, and the crystallite material transitioned from flat-like to spherical shapes. Nanoindentation tests revealed an increase in hardness (H) with Ts, while a decrease in the elastic modulus (E) resulted in an improved elastic strain limit for failure (H/E) and plastic deformation resistance (H3/E2), thereby enhancing stiffness and contact elasticity. Adhesion analysis showed critical loads of ~50 N at Ts of 200 and 400 °C, and ~38 N at Ts of 600 °C. Cohesive failures were associated with lateral cracking, while adhesive failures were attributed to chipping spallation. The tribological behavior was evaluated using a pin-on-disk test, which indicated an increase in friction coefficients with Ts, although they remained lower than those of the substrate. Friction and wear were influenced by the surface morphology, facilitating the formation of abrasive particles. However, the absence of coating detachment in the wear tracks suggested that the films were capable of withstanding the load and wear.

Self-deploying amorphous metal origami structures for environmental protection of lunar payloads

The development of small subterranean deployable structures provides a novel methodology for thermal insulation and radiation protection of scientific payloads for future lunar missions. This work showcases the fabrication and characterization of an origami-inspired self-deploying dome fabricated from amorphous metal foil, taking advantage of the high elastic strain limit of amorphous metals to store energy for deployment in the foil folds when the structure is in the stored configuration. Experiments are performed to understand the influence of material selection on stored energy and springback. A cylindrical structure is fabricated to develop a simulation model for origami-inspired amorphous metal structures and probe the structural integrity of amorphous metal foil structures during repeated loading cycles. Finally, a prototype deployable dome structure is manufactured to showcase the self-deployment strategy and investigate deformation under a simulated lunar regolith load.

Microstructure characterization and mechanical properties of AB-typed high-entropy intermetallics with high strength and thermal stability

In this work, we developed a new system of AB-typed high-entropy intermetallics (HEIs) based on CoHf-like B2 crystal structure. The microstructure and mechanical properties of the targeted CoxCuxTiZrHf alloys were detailedly investigated. With the increase of CoCu content, the alloys’ structure changes from multiphase to single phase. In particular, the multi-principal Co1.7Cu1.7TiZrHf alloy with single B2 crystal structure shows ultrahigh compressive yield strength of 1.77 Gpa and fracture strength of 2.15 Gpa at room temperature, as well as high elastic strain limit of approximately 1.5%. Moreover, it can maintain single-phase B2 structure and high strength after annealing at 900 °C.

The deformation of the icosahedral gold 13-atom cluster

As a building block, the icosahedral gold 13-atom cluster has attracted much attention for many years. In this paper, the tensile and compressive deformation of the icosahedral gold 13-atom cluster are investigated and some interesting results different from bulks and nanowires are obtained. It is found that the elastic strain limits of the cluster are much larger than those of the gold bulks and the nanowires. Within the elastic strain limit, the loading force–strain relationship is not linear. And the stiffness coefficient decreases with increasing strain under the tensile loading, and increases with increasing strain under the compressive loading. Under the influence of temperature, the loading force and the stiffness coefficient decrease with the increasing temperature at the same strain. The elastic strain limit and the break-up strain are also reduced as the temperature rises. Although the bulks and nanowires cannot return to their original configurations when they are in a plastic state, however, the calculation shows that the cluster can return spontaneously to its original icosahedral structure even if the cluster has been at plastic deformation when the loading is released above a certain temperature. A monatomic chain is formed when the cluster is close to rupture. The interatomic distance and the tensile force for the monatomic chain are consistent with the experimental data.

Laser-Based Additive Manufacturing and Characterization of an Open-Porous Ni-Based Metallic Glass Lattice Structure (Ni60Nb20Ta20).

Due to their amorphous structure, metallic glasses exhibit remarkable properties such as high strength, hardness, and elastic strain limit. Conversely, they also exhibit high susceptibility to brittle fracture, making them less qualified for the use as monolithic structural components. Therefore, they may be preferably used as the reinforcing phase in hybrid materials combined with ductile matrix materials. Especially metal matrix composites with interpenetrating structures are suitable. This requires an open-porous structure of the metallic glass. In the study at hand, an open-porous lattice structure was manufactured from metallic glass powder (Ni60Nb20Ta20) by laser powder bed fusion. A parameter study was carried out with various scanning strategies to manufacture a mechanically stable lattice structure while maintaining the amorphous structure of the metallic glass. Thus, X-ray diffraction measurements were conducted to validate the parameter study. A stable lattice structure with a largely amorphous structure was successfully achieved with a scanning strategy of single scanned lines and a rotation of 90° for each layer. However, nanocrystallization of 7% occurred in the heat-affected zones formed between the individual printed layers during reheating. Conducting compression tests, a compressive modulus of 18 GPa and a maximum strength of 90 MPa in 0°-direction were achieved. In 90°-direction, no compressive modulus could be determined but compressive strength resulted in 15 MPa. Performing nanoindentation with a Young's modulus of 195.1 GPa and Vickers hardness of HVIT = 956.1 was achieved for the printed bulk metallic glass alloy. The resulting lattice structure was further characterized by differential scanning calorimetry for thermal behavior.

Non-Hookean large elastic deformation in bulk crystalline metals

Crystalline metals can have large theoretical elastic strain limits. However, a macroscopic block of conventional crystalline metals practically suffers a very limited elastic deformation of <0.5% with a linear stress–strain relationship obeying Hooke’s law. Here, we report on the experimental observation of a large tensile elastic deformation with an elastic strain of >4.3% in a Cu-based single crystalline alloy at its bulk scale at room temperature. The large macroscopic elastic strain that originates from the reversible lattice strain of a single phase is demonstrated by in situ microstructure and neutron diffraction observations. Furthermore, the elastic reversible deformation, which is nonhysteretic and quasilinear, is associated with a pronounced elastic softening phenomenon. The increase in the stress gives rise to a reduced Young’s modulus, unlike the traditional Hooke’s law behaviour. The experimental discovery of a non-Hookean large elastic deformation offers the potential for the development of bulk crystalline metals as high-performance mechanical springs or for new applications via “elastic strain engineering.”

Phase-transforming Ag-NiTi 3-D interpenetrating-phase composite with high recoverable strain, strength and electrical conductivity

It is of particular interest to achieve high elastic recoverable strain in the electrical contact materials while maintaining good electrical conductivity and decent tensile strength. It remains a challenge, especially for bulk-sized metallic materials, as the electrical conductivity and elastic strain limit (or tensile strength) are often mutually exclusive. Here, we present a material design strategy for overcoming this conflict by developing a Ag-NiTi composite with an interpenetrating-phase architecture via infiltrating Ag melt into the partially sintered porous NiTi scaffold. The composite exhibits a good combination of properties with high electrical conductivity comparable to metals, large elastic recoverable strain superior to most of bulk-sized conductive metals as well as higher tensile strength than most of alloys/composites based on silver and other noble metals. This new finding demonstrates that the interpenetrating-phase architecture design is promising for developing new materials for electrical contact application.

Ultrahigh elasticity and anomalous softening of α-Ag2S under pressure

Inorganic semiconductors are often brittle at room temperature, but α-Ag2S was recently observed to own extraordinary metal-like ductility and reversible pressure-induced isosymmetric phase transitions. Here, we report findings from first-principles calculations that α-Ag2S exhibits ultrahigh elasticity and anomalous softening under pressure. Such unusual mechanical behaviors have their underlying origins. Subsequent experimental measurements confirm that α-Ag2S is very soft with a large elastic strain limit of ∼1.7%. This study provides crucial insights into the understanding of high elasticity in semiconducting materials, which is beneficial for the design of semiconductors for flexible and stretchable electronic devices.

Recent Trends in Carbon Nanotube Electrodes for Flexible Supercapacitors: A Review of Smart Energy Storage Device Assembly and Performance

In order to upgrade existing electronic technology, we need simultaneously to advance power supply devices to match emerging requirements. Owing to the rapidly growing wearable and portable electronics markets, the demand to develop flexible energy storage devices is among the top priorities for humankind. Flexible supercapacitors (FSCs) have attracted tremendous attention, owing to their unrivaled electrochemical performances, long cyclability and mechanical flexibility. Carbon nanotubes (CNTs), long recognized for their mechanical toughness, with an elastic strain limit of up to 20%, are regarded as potential candidates for FSC electrodes. Along with excellent mechanical properties, high electrical conductivity, and large surface area, their assemblage adaptability from one-dimensional fibers to two-dimensional films to three-dimensional sponges makes CNTs attractive. In this review, we have summarized various assemblies of CNT structures, and their involvement in various device configurations of FSCs. Furthermore, to present a clear scenario of recent developments, we discuss the electrochemical performance of fabricated flexible devices of different CNT structures and their composites, including additional properties such as compressibility and stretchability. Additionally, the drawbacks and benefits of the study and further potential scopes are distinctly emphasized for future researchers.

High-entropy intermetallics with striking high strength and thermal stability

In this work, we report on a serious of high-entropy intermetallics (HEIs) based on CoHf-like B2 crystal structure. The microstructure evolution and mechanical properties of the targeted TiZrHfCoxNixCux alloys were detailedly investigated. In particular, the equal atomic ratio TiZrHfCoNiCu intermetallic with single-phase B2 structure shows ultrahigh compressive yield strength of 1.58 GPa and fracture strength of 2.48 GPa. It is striking that TiZrHfCoNiCu intermetallic exhibits a certain toughness and very high elastic strain limit of approximately 1.5%. Furthermore, it can maintain single-phase B2 structure and high strength after annealing at 900 °C, indicating its exceptional elevated temperature phase stability. This work not only broadens the family of high-entropy materials, but also provides a new perspective for the design of superalloys based on multi-principal element intermetallics.

Topoarchitected polymer networks expand the space of material properties

Many living tissues achieve functions through architected constituents with strong adhesion. An Achilles tendon, for example, transmits force, elastically and repeatedly, from a muscle to a bone through staggered alignment of stiff collagen fibrils in a soft proteoglycan matrix. The collagen fibrils align orderly and adhere to the proteoglycan strongly. However, synthesizing architected materials with strong adhesion has been challenging. Here we fabricate architected polymer networks by sequential polymerization and photolithography, and attain adherent interface by topological entanglement. We fabricate tendon-inspired hydrogels by embedding hard blocks in topological entanglement with a soft matrix. The staggered architecture and strong adhesion enable high elastic limit strain and high toughness simultaneously. This combination of attributes is commonly desired in applications, but rarely achieved in synthetic materials. We further demonstrate architected polymer networks of various geometric patterns and material combinations to show the potential for expanding the space of material properties.

A highly distorted ultraelastic chemically complex Elinvar alloy.

The development of high-performance ultraelastic metals with superb strength, a large elastic strain limit and temperature-insensitive elastic modulus (Elinvar effect) are important for various industrial applications, from actuators and medical devices to high-precision instruments1,2. The elastic strain limit of bulk crystalline metals is usually less than 1 per cent, owing to dislocation easy gliding. Shape memory alloys3-including gum metals4,5 and strain glass alloys6,7-may attain an elastic strain limit up to several per cent, although this is the result of pseudo-elasticity and is accompanied by large energy dissipation3. Recently, chemically complex alloys, such as 'high-entropy' alloys8, have attracted tremendous research interest owing to their promising properties9-15. In this work we report on a chemically complex alloy with a large atomic size misfit usually unaffordable in conventional alloys. The alloy exhibits a high elastic strain limit (approximately 2 per cent) and a very low internal friction (less than 2 × 10-4) at room temperature. More interestingly, this alloy exhibits an extraordinary Elinvar effect, maintaining near-constant elastic modulus between room temperature and 627 degrees Celsius (900 kelvin), which is, to our knowledge, unmatched by the existing alloys hitherto reported.