Structural Materials Research Articles

Localized Ionic Reinforcement of Double Network Granular Hydrogels.

Nature produces soft materials with fascinating combinations of mechanical properties. For example, the mussel byssus embodies a combination of stiffness and toughness, a feature that is unmatched by synthetic hydrogels. Key to enabling these excellent mechanical properties are the well-defined structures of natural materials and their compositions controlled on lengths scales down to tens of nanometers. The composition of synthetic materials can be controlled on a micrometer length scale if processed into densely packed microgels. However, these microgels are typically soft. Microgels can be stiffened by enhancing interactions between particles, for example through the formation of covalent bonds between their surfaces or a second interpenetrating hydrogel network. Nonetheless, changes in the composition of these synthetic materials occur on a micrometer length scale. Here, 3D printable load-bearing granular hydrogels are introduced whose composition changes on the tens of nanometer length scale. The hydrogels are composed of jammed microgels encompassing tens of nm-sized ionically reinforced domains that increase the stiffness of double network granular hydrogels up to 18-fold. The printability of the ink and the local reinforcement of the resulting granular hydrogels are leveraged to 3D print a butterfly with composition and structural changes on a tens of nanometer length scale.

Effect of basalt fiber length on the behavior of natural hydraulic lime-based mortars

Abstract The number of studies aimed at the characterization of reinforced lime-based mortars for use in the rehabilitation of historic buildings is still very small. This fact contrasts with the growing interest of the industry in these products as substitutes for cement mortars, both for their constructive advantages (compatibility requirements) and their lower cost (economic and environmental). For this reason, this study investigates the effect of basalt fiber length on the physical, mechanical, and durability properties of reinforced natural hydraulic lime mortars and provides criteria for selecting optical blends to meet the various performance requirements for their use as building materials for traditional and contemporary structures. Specimens with 1% volume of basalt fibers and lengths of 6, 12, 18, and 24 mm have been tested. The results in fresh mortar show that increasing the fiber length decreases the consistency and bulk density, as well as increases the air content. Regarding the durability properties of hardened mortar, no direct relationship is observed between fiber length and the decrease in the water absorption coefficient of reinforced mortars. Nor is there a clear relationship between fiber length and the increase in Shore hardness and the decrease in adhesive strength in the reinforced mortars. On the contrary, for small lengths (up to 12 mm), there is a direct relationship between fiber length and the increase in other fundamental mechanical properties such as flexural and compressive strength. Based on the results obtained, a predictive model is proposed to determine the amplification factor of flexural and compressive strength as a function of fiber length.

Metastable Grain Boundaries: The Roles of Structural and Chemical Disorders in Their Energetics, Non-Equilibrium Kinetic Evolution, and Mechanical Behaviors.

Complex environments in advanced manufacturing usually involve ultrafast laser or ion irradiation which leads to rapid heating and cooling and drives grain boundaries (GBs) to non-equilibrium states, featuring distinct energetics and kinetic behaviors compared to conventional equilibrium or near-equilibrium GBs. In this topical review, we provide an overview of both recent experimental and computational studies on metastable GBs, i.e. their energetics, kinetic behaviors, and mechanical properties. In contrast to GBs at thermodynamic equilibrium, the inherent structure energy of metastable GBs exhibits a spectrum instead of single value for a particular misorientation, due to the existence of microstructural and chemical disorder. The potential energy landscape governs the energetic and kinetic behaviors of metastable GBs, including the ageing/rejuvenating mechanism and activation barrier distributions. The unique energetics and structural disorder of metastable GBs lead to unique mechanical properties and tunability of interface-rich nanocrystalline materials. We also discuss that, in addition to structural disorder, chemical complexity in multi-components alloys could also drive the GBs away from their ground states and, subsequently, significantly impact on the GBs-mediated deformation. And under some extreme conditions such as irradiation, structural disorders and chemical complexity may simultaneously present at interfaces, further enriching of metastability of GBs and their physical and mechanical behaviors. Finally, we discuss the machine learning techniques, which have been increasingly employed to predict and understand the complex behaviors of metastable GBs in recent years. We highlight the potential of data-driven approaches to revolutionize the study of disorder systems by efficiently extracting the relationship between structural features and material properties. We hope this topical review paper could shed light and stimulate the development of new GBs engineering strategies that allow more flexibility and tunability for the design of nano-structured materials.

Accelerated Engineering of ELP-Based Materials through Hybrid Biomimetic-De Novo Predictive Molecular Design.

Efforts to engineer high-performance protein-based materials inspired by nature have mostly focused on altering naturally occurring sequences to confer the desired functionalities, whereas de novo design lags significantly behind and calls for unconventional innovative approaches. Here, using partially disordered elastin-like polypeptides (ELPs) as initial building blocks this work shows that de novo engineering of protein materials can be accelerated through hybrid biomimetic design, which this work achieves by integrating computational modeling, deep neural network, and recombinant DNA technology. This generalizable approach involves incorporating a series of de novo-designed sequences with α-helical conformation and genetically encoding them into biologically inspired intrinsically disordered repeating motifs. The new ELP variants maintain structural conformation and showed tunable supramolecular self-assembly out of thermal equilibrium with phase behavior in vitro. This work illustrates the effective translation of the predicted molecular designs in structural and functional materials. The proposed methodology can be applied to a broad range of partially disordered biomacromolecules and potentially pave the way toward the discovery of novel structural proteins.

Multi-scale lumped modeling of micro-channels cooling structure for W7-X divertor unit target module

A novel concept for the cooling system of the W7-X divertor unit target module has been proposed, which involves tiles equipped with parallel arrays connected by hundreds of sub-millimeter rectangular micro-channels (MCs), obtained using Additive Manufacturing techniques. The structural material proposed for the heat sink substrate is galvanized copper, while the plasma facing material is tungsten. To reduce the high computational cost of thermal-hydraulic simulations of the tiles, a multi-scale lumped modeling approach has been built in previous studies. This involves replacing a group of hydraulic parallel MCs with a porous strip (PS), suitably calibrated to reproduce similar thermal-hydraulic behavior of the MCs. The aim of the current work is to verify that the PS-model is also suitable for the thermo-mechanical stress evaluation, comparing the results from arrays with MCs and PS. Since the heat sink and plasma-facing tiles are bonded, the interfacial delamination and shear stresses are analyzed, being crucial for structural integrity. The analyses, carried out in the elastic regime, show that the PS model returns conservative results when compared to the MCs model, with an overestimation of the delamination and shear stresses at the free edge. Results from both models reveal nearly identical interfacial stress predictions at the free surface edge. Moreover, it is found that both MCs and PS blocks, located near the bond interface, contribute to high-stress fluctuations that could lead to the delamination of the bond interface, suggesting that the distance of the microchannel from the interface should be increased. The PS model can reliably be used to design and verify the most convenient series/parallel connection of the tiles in the divertor unit target module, taking operational constraints into consideration.

Scalable Synthesis of SiOx-TiON Composite As an Ultrastable Anode for Li-Ion Half/Full Batteries.

Among various anode materials, SiOx is regarded as the next generation of promising anode due to its advantages of high theoretical capacity with 2680 mA h g-1, low lithium voltage platform, and rich natural resources. However, the pure SiOx-based materials have slow lithium storage kinetics attributed to their low electron/ion conductive properties and the large volume change during lithiation/delithiation, restricting their practical application. Optimizing the SiOx material structures and the fabricating methods to mitigate these fatal defects and adapt to the market demand for energy density is critical. Hence, SiOx material with TiO1-xNx phase modification has been prepared by simple, low-cost, and scalable ball milling and then combined with nitridation. Consequently, based on the TiO1-xNx modified layer, which boosts high ionic/electronic conductivity, chemical stability, and excellent mechanical properties, the SiOx@TON-10 electrode shows highly stable lithium-ion storage performance for lithium-ion half/full batteries due to a stable solid-electrolyte interface layer, fast Li+ transport channel, and alleviative volumetric expansion, further verifying its practical feasibility and universal applicability.

Overcoming strength-ductility tradeoff with high pressure thermal treatment

Conventional material processing approaches often achieve strengthening of materials at the cost of reduced ductility. Here, we show that high-pressure and high-temperature (HPHT) treatment can help overcome the strength-ductility trade-off in structural materials. We report an initially strong-yet-brittle eutectic high entropy alloy simultaneously doubling its strength to 1150 MPa and its tensile ductility to 36% after the HPHT treatment. Such strength-ductility synergy is attributed to the HPHT-induced formation of a hierarchically patterned microstructure with coherent interfaces, which promotes multiple deformation mechanisms, including dislocations, stacking faults, microbands and deformation twins, at multiple length scales. More importantly, the HPHT-induced microstructure helps relieve stress concentration at the interfaces, thereby arresting interfacial cracking commonly observed in traditional eutectic high entropy alloys. These findings suggest a new direction of research in employing HPHT techniques to help develop next generation structural materials.

Experimental Study of Recycled Aggregate, Fly Ash and Steel Fiber on Properties of Concrete

The use of recycled aggregates in concrete opens a whole new range of possibilities in the reuse of materials in the building industry. The utilization of recycled aggregates is a good solution to the problem of an excess of waste material, provided that the desired final product quality is reached.The use of recycled aggregate in concrete can be useful for environmental protection and economical terms recycled aggregates are the materials for the future.The work focuses on the possibilities of the recycled aggregate concrete as structural material with replacement level of 25%,50% and 75% byweight of concrete. Fly ash is also used as a partial replacement of Portland cement with10, 20 & 30 % by weight of cement in order to improve the properties of RAC. The use of fly ash replacement in Recycled Aggregate concrete (RAC) could improve compressive strength to be higher than that of concrete without fly ash at the same W/B ratio.The fly ash is an organic, non combustible residue of coal after burning in power plant. The steel fiber are available imperforated, corrugated or with wide end for better bending.The volume fraction of the hook end steel fiber used in this study varied from 0.25%,0.5%a and 0.75 %. Key words- Fly Ash, Recycled Aggregate, Recycled Concrete Aggregate, Steel Fiber, Water Cement Ratio.

Crystal-Inspired Cellular Metamaterials and Triply Periodic Minimal Surfaces

Triply periodic minimal surfaces (TPMSs) are found in many natural objects including butterfly wings, sea urchins, and biological membranes. They simultaneously have zero mean curvature at every point and a crystallographic group symmetry. A metamaterial can be created from such periodic surfaces or used as a reinforcement of a composite material. While a TPMS as a mathematical object has been known since 1865, only novel additive manufacturing (AM) technology made it possible to fabricate cellular materials with complex TPMS shapes. Cellular TPMS-based metamaterials have remarkable properties related to wetting/liquid penetration, shock absorption, and the absence of stress concentrators. Recent studies showed that TPMSs are also found in natural crystals when electron surfaces are considered. Artificial crystal-inspired metamaterials mimic such crystals including zeolites and schwarzites. These metamaterials are used for shock, acoustic waves, and vibration absorption, and as structural materials, heat exchangers, and for other applications. The choice of the crystalline cell of a material, as well as its microstructure, plays a decisive role in its properties. The new area of crystal-inspired materials has many common features with traditional biomimetics with models being borrowed from nature and adjusted for engineering applications.

Simulating non-stationary and non-Gaussian cross-correlated fields using multivariate Karhunen–Loève expansion and L-moments-based Hermite polynomial model

In practical engineering, cross-correlated random fields are often used to model structural materials or random loads containing multiple correlations. Effective and accurate simulation of these cross-correlation fields is an important prerequisite for subsequent reliability analysis and uncertainty quantification of complex systems. Therefore, this paper proposes a new simulation method for non-stationary non-Gaussian cross-correlated random fields to satisfy realistic engineering requirements. In this new method, L-moments-based Hermite polynomials model (LHPM) is extended to non-stationary non-Gaussian cross-correlated fields. Then, a transformation model from non-stationary non-Gaussian correlation matrix function (CMF) to the underlying Gaussian CMF is explicitly given. Multivariate K-L expansion is further used to approximate the underlying Gaussian cross-correlated fields, where the eigenvalue and eigenfunctions are estimated via the Nyström method with uniform weights. The approximation permits the application of few random variables to characterize the entire Gaussian cross-correlated fields. Ultimately, the simulated underlying Gaussian cross-correlated fields are mapped back to the target non-stationary non-Gaussian cross-correlated fields based on LHPM. Three typical examples, including exponential kernel, Wiener process kernel and spatially varying non-Gaussian and nonstationary seismic ground motions, are used to validate the effectiveness of the proposed method. The source code is readily available at: https://github.com/zhaozhao23/Simulation-of-non-stationary-and-non-Gaussian-cross-correlated-fields.

Lignocellulosic abaca fibre-reinforced thermoplastic composites as future sustainable structural materials: a bibliometric analysis and literature review

Lignocellulosic abaca fibre-reinforced thermoplastic composites as future sustainable structural materials: a bibliometric analysis and literature review

Study on thermal runaway propagation inhibition of battery module by flame-retardant phase change material combined with aerogel felt

Phase change materials (PCMs) are susceptible to fire and may accelerate heat transfer when thermal runaway propagation (TRP) in lithium-ion battery (LIB) modules, requiring the design and safe use of insulation structures with excellent flame-retardant properties. In this work, the sandwich structure composed of flame-retardant phase change material (FRPCM) combined with aerogel felt (AEGF) is used to study the inhibitory effect on TRP of pouch battery modules (BMs). The structural materials are applied between cells, and the changes of temperature, voltage, mass and other parameters in the TRP process are analyzed by changing the thickness of FRPCMs and AEGFs, and the changes of heat flux of materials were also qualitatively analyzed. The results show that the increase of FRPCM and AEGF thickness can increase the interval time of TRP and reduce the overall thermal risk of the BMs. Compared to Test-1, the increase in TRP time between cells 1 and 2 in Test-2 to Test-5 ranged from 52.7% to 358.7%, and the longest thermal runaway interval reached 844 s. Both the structural materials in Test-6 and Test-7 block the TRP. Combining the thermal conductivity of PCMs and the thermal insulation properties of AEGFs, this work can effectively conduct heat to the environment and block the TRP when applied to BMs, which provides a valuable reference for efficient inhibition and blocking of TRP.

Crystallography applications: A comprehensive review

Crystallography is an essential scientific technique profoundly influencing our understanding of atomic and molecular structures in materials, providing insights into the arrangement and interactions of atoms. This review highlights crystallographys extensive applications across chemistry, biology, physics, and materials science, emphasizing its critical role and adaptability. The paper traces crystallographys historical development, outlines its fundamental principles, and celebrates its significant milestones and contributions to science. By revealing the complex structures and functions of compounds, from simple molecules to complex macromolecules, crystallography has catalyzed advancements in drug development, material innovation, and fundamental scientific understanding. The paper asserts crystallographys continued prominence in scientific research, with its application and influence steadily growing. Its pivotal in enhancing our understanding of matter, driving technological and material advancements, and offering solutions to complex scientific questions. Moreover, the review addresses the current challenges and future directions of crystallography, pointing out potential areas for innovation and improvement. As technology advances, crystallographys significance in various scientific disciplines remains indispensable, solidifying its position as a cornerstone of scientific inquiry and discovery. The paper concludes by reinforcing the techniques vital role in pushing the boundaries of science and technology.

Rate-dependent energy dissipation of graded viscoelastic structures fabricated by grayscale vat photopolymerization

A major benefit of additive manufacturing technologies is precise control over structural topologies and material properties, which allows to tailor, for instance, energy absorption and dissipation. While vat photopolymerization is generally restricted to a single material, grayscale masked stereolithography (gMSLA) allows to customize material behavior by grading the light intensity within a structure. This study investigates the impact and opportunities of grayscale grading strategies on the rate-dependent mechanical behavior of structures fabricated by gMSLA. Considering the viscoelastic nature of polymers, rate-dependent energy dissipation is explored, introducing a parametric linear viscoelastic constitutive model for varying grayscales. The investigation includes the comprehensive characterization of mechanical properties, numerical finite element simulation, validation through experimental procedures, and exploration of dissipation energy under different strain rates. In this way, a rational function successfully determines the critical strain rate at which the maximum dissipation occurs. Overall, the research offers a comprehensive investigation of the mechanical dissipation behavior of graded 3D printed structures, laying the foundation for further studies and advancements aimed at optimizing these structures for enhanced energy absorption capabilities.

Superstrong and tough silk fibers cross-linked with functionalized graphene

Natural silkworm silks with an intriguing integration of good strength, modulus, toughness and biocompatibility, have been widely used in textile and medical industry. However, the strength of silkworm silks is inferior to that of spider dragline silks, which are the strongest natural silks but extremely low yield. Herein, we develop a feasible strategy to continuously produce superstrong and tough regenerated silk fibers (RSFs) through the reconstruction of hierarchical and cross-linked architectures. Amine functionalized graphene (NH2-G) has been introduced to improve the content of β-sheet and crystalline orientation, and glutaraldehyde (GA) has been used to bridge NH2-G and silk micro/nanofibrils (SNFs) to form a highly interconnected and closely packed network, resulting in the remarkably improvement of mechanical properties. The resultant fibers exhibit an excellent tensile strength of 1029.6 ± 144.8 MPa, a Young's modulus of 16.8 ± 1.5 GPa, and a toughness of 277.4 ± 17.0 MJ/m3, exceeding those of the natural silkworm silks, spider dragline silks and most other previously reported regenerated silk fibers. We believe that the high-performance silk-based fibers are promising applications in lightweight and advanced structural materials.

Nanostructured High Entropy Alloys as Structural and Functional Materials.

Since their introduction in 2004, high entropy alloys (HEAs) have attracted significant attention due to their exceptional mechanical and functional properties. Advances in our understanding of atomic-scale ordering and phase formation in HEAs have facilitated the development of fabrication techniques for synthesizing nanostructured HEAs. These materials hold immense potential for applications in various fields including automobile industries, aerospace engineering, microelectronics, and clean energy, where they serve as either structural or functional materials. In this comprehensive Review, we conduct an in-depth analysis of the mechanical and functional properties of nanostructured HEAs, with a particular emphasis on the roles of different nanostructures in modulating these properties. To begin, we explore the intrinsic and extrinsic factors that influence the formation and stability of nanostructures in HEAs. Subsequently, we delve into an examination of the mechanical and electrocatalytic properties exhibited by bulk or three-dimensional (3D) nanostructured HEAs, as well as nanosized HEAs in the form of zero-dimensional (0D) nanoparticles, one-dimensional (1D) nanowires, or two-dimensional (2D) nanosheets. Finally, we present an outlook on the current research landscape, highlighting the challenges and opportunities associated with nanostructure design and the understanding of structure-property relationships in nanostructured HEAs.

High-Entropy Strategy to Achieve Electronic Band Convergence for High-Performance Thermoelectrics.

Multiband convergence has attracted significant interest due to its positive effects on further improving thermoelectric performance. However, the current research mainly focuses on two- or three-band convergence in lead chalcogenides through doping and alloying. Therefore, exploring a new strategy to facilitate more-band convergence has instructive significance and practical value in thermoelectric research. Herein, we first propose a high-entropy strategy to achieve four-band convergence for optimizing thermoelectric performance. Taking high-entropy AgSbPbSnGeTe5 as an example, we found that the emergence of more-band convergence occurs as the configuration entropy increases; in particular, the four-band convergence occurs in high-entropy AgSbPbSnGeTe5. The overlap of multiatom orbitals in the high-entropy sample contributes to the convergence of four valence bands, promoting the improvement of electrical performance. Meanwhile, due to large lattice distortion and disordered atoms, the phonon mean free path is effectively compressed, resulting in low lattice thermal conductivity of high-entropy AgSbPbSnGeTe5. Consequently, AgSbPbSnGeTe5 achieved an intrinsically high ZT value of 1.22 at 673 K, providing a cornerstone for further optimizing thermoelectric performance. For example, by generally optimizing the carrier concentration, a peak ZT value of ∼1.75 at 723 K is achieved. These insights offer a comprehensive understanding of the band structure affected by unique structures of high-entropy materials and also shed useful light on innovation mechanisms and functionalities for future improvement of thermoelectric performance.

The Directions for Improving the Surface Wastewater Treatment Facilities

Prospective directions for increasing efficiency of the drains by improving the systems for collection, disposal and treatment of surface wastewater have been considered. The design and technological features of treatment facilities in operation have been analyzed. The significant shortcomings have been identified, as a result of which the quality of purified water discharged into water bodies, declared by manufacturers, is reduced and the operation is complicated. Promising directions for resolving the identified problems have been recommended: targeted formation of surface wastewater flows, increasing the engineering and technological level of mono-block structures, the use of modern structural materials, providing the possibility of remote monitoring and control of the technological process, as well as timely routine maintenance.

Long-term oxidation of Ti3Al0.8Sn0.2C2 in air at 1200 °C

The addition of Sn into the raw materials is currently one of the most widely used methods to improve the purity and mechanical properties of Ti3AlC2. It follows in this work to investigate the oxidation behavior of the resulting Ti3Al0.8Sn0.2C2 at 1200 °C with the oxidation time up to 500 h. The oxidation kinetics shows that its oxidation resistance is much worse than that of common MAX phases including Ti3AlC2, Ti2AlC, and Cr2AlC. The oxide layer mainly consists of TiO2 and Al2O3, with only a small amount of SnO2 at the beginning of the oxidation stage. Cracks induced by the internal thermal stress penetrate through the entire oxide layer after only 1 h, which is an important reason for the rapid oxidation of the internal substrate layer. This work is expected to provide some inspiration and reference for Ti3Al0.8Sn0.2C2 used as the potential high-temperature structural material.

EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF MODIFIED PERVIOUS CONCRETE AS A RIGID PAVEMENT FOR LOW VOLUME TRAFFIC

The previous concrete which is also known as No-fines concrete is a mixture of cement, water and a particular sized coarse aggregate combined to form a porous structural material. Application of pervious concrete in pavements mainly focuses on storm water control mostly in urban areas where scarcity of land is high. Permeable pavement allows water from precipitation and other sources to pass through it and therefore reduces the runoff from a site, which results in the recharge of ground water and increases the level. In this view it is necessary to study the behavior of pervious concrete by enhancing its mechanical properties by maintaining required permeability. The main objective of this investigation is to develop a strong pervious concrete mix using with waste tyre rubber powder. In addition, it is also aimed to compare the mechanical properties of these modified mixes with pervious concrete. The properties such as compressive strength, indirect tensile strength, flexural strength and permeability tests are performed to determine the suitability. From the study it is concluded that using of fine aggregate and waste tyre rubber powder as partial replacement material in coarse aggregate shows significant improvement in the mechanical properties (i.e. compressive strength, indirect tensile strength and flexural strength) with maintaining required permeability. Among all the considered modified mixes, MPC-4 (i.e. 10% waste tyre rubber powder as partial replacement material in coarse aggregate) performs better.