High-performance Structural Materials Research Articles

The Irradiation Effects in Ferritic, Ferritic–Martensitic and Austenitic Oxide Dispersion Strengthened Alloys: A Review

High-performance structural materials (HPSMs) are needed for the successful and safe design of fission and fusion reactors. Their operation is associated with unprecedented fluxes of high-energy neutrons and thermomechanical loadings. In fission reactors, HPSMs are used, e.g., for fuel claddings, core internal structural components and reactor pressure vessels. Even stronger requirements are expected for fourth-generation supercritical water fission reactors, with a particular focus on the HPSM’s corrosion resistance. The first wall and blanket structural materials in fusion reactors are subjected not only to high energy neutron irradiation, but also to strong mechanical, heat and electromagnetic loadings. This paper presents a historical and state-of-the-art summary focused on the properties and application potential of irradiation-resistant alloys predominantly strengthened by an oxide dispersion. These alloys are categorized according to their matrix as ferritic, ferritic–martensitic and austenitic. Low void swelling, high-temperature He embrittlement, thermal and irradiation hardening and creep are typical phenomena most usually studied in ferritic and ferritic martensitic oxide dispersion strengthened (ODS) alloys. In contrast, austenitic ODS alloys exhibit an increased corrosion and oxidation resistance and a higher creep resistance at elevated temperatures. This is why the advantages and drawbacks of each matrix-type ODS are discussed in this paper.

Shearing brittle intermetallics enhances cryogenic strength and ductility of steels.

Precipitates are crucial for crafting mechanically strong metallic materials. In this work, we report the dislocation cutting of B2 (ordered body-centered cubic) nanoprecipitates, typically considered nonshearable intermetallics, in a lightweight compositionally complex steel during cryogenic tensile loading. Shearing is enabled by the high strength level for dislocation glide within the austenitic matrix, attributed to the substantial strengthening from subnanoscale local chemical ordering zones and the pronounced solid solution strengthening from the multiprincipal elements in the matrix. This mechanism not only harnesses the intense strengthening and strain hardening provided by otherwise impenetrable brittle nanoprecipitates but also introduces ductility through their sequential shearing with ongoing deformation. Our steel thus showcases ultrahigh cryogenic tensile strength up to 2 gigapascal at a remarkable tensile elongation of 34%. This study reveals a new strategy for designing high-performance structural materials.

Hierarchical and reconfigurable interfibrous interface of bioinspired Bouligand structure enabled by moderate orderliness.

Introducing natural Bouligand structure into synthetics is expected to develop high-performance structural materials. Interfibrous interface is critical to load transfer, and mechanical functionality of bioinspired Bouligand structure yet receives little attention. Here, we propose one kind of hierarchical and reconfigurable interfibrous interface based on moderate orderliness to mechanically reinforce bioinspired Bouligand structure. The interface imparted by moderate alignment of adaptable networked nanofibers hierarchically includes nanofiber interlocking and hydrogen-bonding (HB) network bridging, being expected to facilitate load transfer and structural stability through dynamic adjustment in terms of nanofiber sliding and HB breaking-reforming. As one demonstration, the hierarchical and reconfigurable interfibrous interface is constructed based on moderate alignment of networked bacterial cellulose nanofibers. We show that the resultant bioinspired Bouligand structural material exhibits unusual strengthening and toughening mechanisms dominated by interface-microstructure multiscale coupling. The proposed interfibrous interface enabled by moderate orderliness would provide mechanical insight into the assembly of widely existing networked nanofiber building blocks toward high-performance macroscopic bioinspired structural assemblies.

Fabrication of High-Performance Densified Wood via High-Pressure Steam Treatment and Hot-Pressing.

The fabrication of sustainable structural materials with high physical properties to replace engineering plastics is a major challenge for modern industry, and wood, as the most abundant sustainable natural raw material on the planet, has received a great deal of attention from researchers. Researchers have made efforts to enhance the physical properties of wood in order to replace plastics. However, it is also difficult to meet practical demands at a low cost. Herein, we report a simple and efficient top-down strategy to transform bulk natural basswood into a high-performance structural material. This three-step strategy involves partial removal of hemicellulose and lignin via treating basswood by boiling an aqueous mixture of NaOH and Na2SO3, and a high-pressure steam treatment (HPST) was applied to delignified wood followed by hot-pressing, which allowed the wood to absorb moisture uniformly and quickly. HPST-treated dense delignified wood (HDDW) has a tensile strength of ~420 MPa, which is 6.5 times better than natural basswood (~65 MPa). We systematically investigated the various factors affecting the tensile strength of this wood material and explored the reasons why these factors affect the tensile strength, as well as the intrinsic connection between the moisture absorbed through HPST and the increased tensile strength of HDDW. Through our experiments, we realized the enhancement mechanism of HDDW and the optimal experimental conditions for the fabrication of HDDW.

Effect of Si addition on the microstructure and tribological properties of FeCrNi medium entropy alloy

FeCrNi medium-entropy alloys (MEAs) have attracted widespread attention due to the excellent toughness and corrosion resistance, but its relatively low hardness results in poor tribological properties. Herein, a series of FeCrNiSix MEAs (x = 0, 0.1, 0.15, and 0.2) were prepared by arc melting and their tribological behavior was systematically investigated. The results showed that Si doping promoted the precipitation of fine σ particles in the FCC matrix, which not only enhanced the hardness, but also reduced the scratching of the wear surface by the counterpart ball. The friction coefficient and specific wear rate of the Si0.2 MEA decreased significantly (0.53 and 5.53 × 10−4 mm3/(Nm)), which were reduced by 24% and 28%, respectively, compared with the base alloy. This study provides effective guidance for improving the wear resistance of high-performance structural materials.

Novel conformal sandwich lattice structures: Design concept, fabrication and mechanical properties

A novel conformal sandwich lattice is proposed by introducing the design concept of bioinspired sandwich structures into the microstructure design of triply periodic minimal surface (TPMS) lattices, and the mechanical properties of the conformal sandwich lattice (P-SC) with P-TPMS lattice skins and simple cubic (SC) plate lattice cores are investigated numerically and experimentally. The P-SC specimen manufactured by the laser powder bed fusion (L-PBF) with glass bead-filled polyamide composite exhibits negligible anisotropy in its mechanical properties, as confirmed by tensile tests conducted on specimens fabricated at various build orientations. The elastic properties of the P-SC can be widely tailored by modifying the structural parameters. Especially, the anisotropic index can be tailored to obtain an elastically-isotropic P-SC sandwich lattice. Additionally, the P-SC exhibits superior elastic properties and energy absorption compared with the conventional lattices. The findings provide insights into the design flexibility of advanced high-performance structural materials for complex engineering applications.

Nanocomposites as sustainable smart materials: A review

Sustainable nano-composites refer to the development of composite materials that incorporate nano-particles or nanofibres in a matrix of sustainable polymers. These materials offer many benefits, including enhanced mechanical and thermal properties, improved resistance to degradation, and reduced environmental impact. Sustainable nano-composites have emerged as a promising class of materials and have received noteworthy consideration in recent years because of having unique characteristics and latent for numerous industrial applications. Nano-composites are composite materials that comprise a polymer matrix reinforced with nano-sized particles. Properties of sustainable nano-composites are characterized by their enhanced mechanical, thermal, and electrical properties compared to traditional composite materials. Nano-composites have been studied for several decades, and their applications are varied, including biomedical implants, energy storage devices, and high-performance structural materials. Industrial applications of sustainable nano-composites are expanding rapidly due to their improved properties and environmental benefits. Sustainable nano-composites have a wide range of industrial applications, including automotive, aerospace, electronics, packaging, and biomedical industries. Sustainable nano-composites represent a promising area of research and development for creating high-performance materials that are both environmentally friendly and economically feasible. Sustainable nano-composites are also a promising solution to address the environmental concerns associated with conventional nano-composites. The use of these materials is expected to increase in the future as sustainability becomes an increasingly important consideration in material design and manufacturing. This article provides an overview on the sustainable nano-composites.

Sustainability through Optimal Compositional and Thermomechanical Design for the Al-7XXX Alloys: An ANOVA Case Study

The quest for lightweight, high-performance structural materials for demanding applications such as in the fields of automotive, aerospace, and other high-tech and military industries pushes the boundaries of material science. The present work aims to draw attention to a novel, sustainable manufacturing approach for the development of next-generation 7xxx series aluminum alloys that have higher strength by rejuvenating a sustainable compositional and thermomechanical processing strategy. Our innovative strategy integrates two key synergies: trace hafnium (Hf) addition for microstructural refinement, unique thermomechanical treatment involving cryorolling, and a short annealing method. Experimental results revealed that our base alloy exhibited a 33 µm grain size and impressive initial mechanical properties (334 MPa UTS, 150 HV). Adding 0.6 wt.% Hf and employing 50% cryorolling with short annealing led to a remarkable 10 µm grain size reduction and significant mechanical property leaps. The resulting alloy boasts a 452 MPa UTS and 174 HV, showcasing the synergistic advantageous effect of Hf and cryorolling plus annealing treatment. The developed alloys were compositional- and work hardening-dependent, leading to a rich mix of strengthening mechanisms. Optical and scanning electron microscopy reveal several intermetallic phases within the fcc matrix, wherein the Al3Hf phase plays a key role in strengthening by impeding dislocation movement. In addition to experimental results, a 12-full-factorial design experiment via ANOVA analysis was also utilized to validate the significant influence of Hf and cryorolling on properties with (p-values < 0.05). Among the different parameters, cryorolling plus annealing appeared as the most noteworthy factor, followed by the composition. Using the regression model, the ultimate tensile strength and hardness were predicted to be 626 MPa UTS and 192 HV for an alloy with 0.6 wt.% Hf and 85% cryorolling, which opens a new avenue for ultra-high-strength Al7xxx alloys.

Inspection of Surface Damage in Composite Materials with Different Techniques

Due to their excellent physical properties and high strength and stiffness relative to density, aerospace industry research is producing high-performance structural materials, such as composites, which are used in many critical structural parts like airframes, wings, rotor blades, propellers, and other components. However, during flight, these materials may be damaged by impact, thermal stress, moisture, and ultraviolet radiation. One of the most prevalent issues with composite materials is their challenging nature in terms of flaw detection during both manufacturing and use. When they are employed in the crucial areas that were previously indicated, this becomes a very serious issue. When evaluating the structural integrity of composites and looking for any damage, microscopes are a very useful instrument. Effective methods for identifying and analyzing damage include microscopic procedures like optical microscopy, stereomicroscopy, scanning electron microscopy (SEM), scanning ion microscopy (SIM), and atomic force microscopy (AFM). A variety of methods may be employed with microscopes to examine and identify deterioration in composite materials. It is often possible to examine overt deterioration on the surface of composite materials under the microscope utilizing a number of different approaches and procedures. Determining the kind, extent, distribution, and impact of the damage requires these inspections. Often employed techniques consist of: SEM is a method for high-resolution imaging of surface damage. It entails shining an electron beam onto the sample's surface and capturing pictures. SEM is a useful tool for identifying erosion, delamination, and microcracks. It is also possible to measure things like the damage's breadth and depth. Optical microscopes have a large field of view and look at damaged regions. This makes it possible to find tiny fractures or cracks that are invisible to the unaided eye. Furthermore, details on the degree of harm, the roughness of the surface, and the breadth and depth of the fractures may be acquired. To see damaged objects, optical microscopy is utilized. Cracks and damage locations are visible with optical microscopy. Optical microscopes can identify different kinds of damage by looking at the surface of the material. Damage like delamination, fiber breakage, cracks, and deformations are a few examples of these. This study examines the efficacy of microscopic methods and non-destructive testing in assessing the different kinds of damage that can occur at the interfaces between holes in composite materials. Composite test materials were chosen from glass fiber reinforced phenolic matrix composites that were produced in compliance with aerospace standards. The measurements led to the conclusion that using microscopic techniques has benefits like speed and field suitability. However, the continuous development and improvement of new methods in this field will contribute to a better understanding of layered composite materials and the development of safer and more durable structures.

Electrochemically Activated Multifunctional Carbon Fibre Composites

A multifunctional lightweight material combines several functions in a single material entity able to simultaneously bear mechanical loads by acting as a carbon fibre composite component while providing one or more other functionalities at the same time, e.g. storing energy. Carbon fibres are particularly attractive as they can be used both as a high-performance structural material and as an active electrochemical material. Carbon fibres allow for ion insertion into their microstructure with capacities comparable to graphite and hard carbon used in state-of-the-art lithium-ion and other alkali-ion batteries [1]. Carbon fibres are electrically conductive and can therefore replace the conventional metallic current collector. Carbon fibres are thus in this context a truly multifunctional material. A piezo-electrochemical transducer effect (PECT) [2], has also been discovered in ion inserted carbon fibres. The PECT-effect, that mechanical load changes the electrochemical potential of ion-inserted materials, could be used for sensing, where a voltage change is related to the mechanical strain in the material. When carbon fibres are inserted with alkali ions, they expand in the axial direction [3]. This expansion could be used for making linear actuators with high forces or even to create shape-morphing materials [4]. Combing the PECT effect with the expansions allow for using carbon fibres in an electrochemical cell to harvest energy [5],[6]. Such functionalities could be combined with an inherent electrochemical energy storage (battery function) capability. Imagine a solid-state high-performance structural material that senses its own state, can change shape and harvest energy – that is stored in the material itself!In this work, we will show functionalities coming from alkali ion insertion in carbon fibres that goes beyond the battery function, and how these functions can be combined in a single device. The starting point for these concepts are so called structural batteries, which are hybrid and multifunctional composite materials able to carry load while storing electrical energy like lithium-ion batteries. In such a battery, carbon fibres are used as the load carrying material thanks to their excellent strength and stiffness properties, but also as the active negative electrode. They also include a multifunctional matrix system – a structural battery electrolyte (SBE), the material holding the fibres together to make a solid-state load carrying material, but which at the same time is ionically conductive and chemically stable in the voltage window used. It also includes a multifunctional positive electrode – a composite electrode based on conventional ion inserting materials like lithium iron phosphate (LFP) supported by electrochemically active carbon fibres for load carrying and electrical conduction. This can then also be used for inherent strain sensing in the material without any added mass or wiring. The material can also be made to shape-morph with electrical control at low voltages and harvesting energy by converting mechanical strain to electrical power.

Alkaline hydrogen peroxide delignification of three lignocellulosic biomass under atmospheric pressure

The study’s goal was to investigate the delignification characteristics using alkaline hydrogen peroxide (AHP) under atmospheric pressure, intending it as a pre-treatment method for transforming low-value lignocellulosic biomass into high-performance structural materials. The lignocellulosic biomass used in this study were Japanese cedar (Cryptomeria japonica), Hyun aspen (Populus alba x glandulosa), and bamboo (Phyllostachys pubescens), which are underutilized and low-value lignocellulosic biomass in Korea. The delignification conditions used were pH 11, liquor ratio 12.5, H2O2 (3 to 10%), temperature (25 to 100 °C), and time (1 to 24 h). Japanese cedar exhibited <30% delignification even under the most severe conditions. In contrast, Hyun aspen achieved more than double that level of delignification. However, reaching over 60% delignification was challenging. Bamboo was easily delignified, reaching approximately 80% delignification using similar conditions performed in Japanese cedar and Hyun aspen. These differences observed in AHP delignification among three species were likely to be primarily due to the structural differences and proportion of condensed units in lignin. Consequently, for Hyun aspen and bamboo, the AHP delignification process under atmospheric pressure was considered to be feasible as a pre-treatment method for high-performance structural materials.

Influence of interstitial carbon content on the microstructure, mechanical and electrochemical corrosion properties of CoFeNiMn multi-principal component alloys

In this study, the effects of carbon content on the microstructural evolution as well as compression and electrochemical corrosion properties of CoFeNiMn multi-principal component alloys (MPCAs) were investigated. A series of (Co25Fe25Ni25Mn25)100−xCx (x = 4, 5, 6, 7, 8) alloys were prepared by vacuum arc melting. Increasing carbon content, the structure transits from a single face-centered-cubic (FCC) phase into a mixed structure containing FCC phase and M23C6 carbides. The yield strength and hardness of the (Co25Fe25Ni25Mn25)100−xCx alloys were enhanced by increasing carbon content, which in turn decreases the ductility. The alloys containing eutectic carbides had a good combination of high yield strength (880 MPa), high fracture strength (2773 MPa), and large fracture strain (47%). Electrochemical measurements indicated that carbon content evidently affects the corrosion resistance of (Co25Fe25Ni25Mn25)100−xCx alloys in 3.5 wt% NaCl solution. Their corrosion resistance initially increases and then decreases with increasing carbon content. The increase in M23C6 carbides can accelerate pitting corrosion and degenerate their corrosion resistance. These findings not only provide comprehensive understanding of the carbon-alloyed behavior in FCC-type MPCAs but also show their potential engineering application as high-performance structural materials.

Revealing extraordinary work-hardening capacity in a high-entropy alloy with homogeneous composite structures

High performance structural metal materials with high strength and certain ductility have a wide range of critical applications in fields such as aviation, aerospace, transportation. A vein-shaped structure composed of recrystallized ultrafine grains was introduced into a nano-precipitated high-entropy alloy (HEA) by inter-critical annealing after cold rolling. The vein-shaped structure coupled with nanoprecipitates contributes a remarkable improvement of mechanical properties, with yield strength enhanced from 1232 MPa to 1510 MPa, ultimate tensile strength from 1544 MPa to 1745 MPa, and uniform elongation from 1.84 % to ∼7 %, compared to the as-rolled matrix. The synchronized increase in strength and ductility is the outcome of controlling multiscale strengthening mechanisms from tailoring dislocations, nanoprecipitates, bimodal grains, and deformation microbands, which activate the potential work-hardening capacity in the present HEA.

3D printed hierarchical interpenetrating phase composites with multi-scale mechanical energy absorption mechanisms

Lightweight, strong, and energy-absorbing materials are highly sought after in practical engineering applications. To this end, interpenetrating phase composites (IPC) stand as a novel class of composite materials to better leverage the properties of their constituents. Their structural design, however, has been limited to only specific structural features at a certain length scale in the existing studies. Inspired by the hierarchical composite materials in nature, this work proposes a novel concept of hierarchical interpenetrating phase composites (HIPC) by polymer infiltration into 3D printed hierarchical porous ceramic lattices. The hierarchical porous alumina lattices have up to three levels of porosity, including 3D printed macropores (≈300 μm), emulsion-templated micropores (≈10 μm), and sub-micropores (<1 μm) from partial sintering. Upon epoxy infiltration, three-level HIPC is constructed with hierarchically incorporated epoxy domains and alumina-epoxy interfaces, which leads to its unique multi-scale mechanical energy absorption mechanisms. Featuring a particularly porous and lightweight ceramic lattice, three-level HIPC exhibits an excellent combination of high specific compressive strength (64.6 kN m/kg), specific flexural strength (39.2 kN m/kg), and SEA (18.4 kJ/kg). In addition, even with a low ceramic content, three-level HIPC can effectively enhance the thermal conductivity via its hierarchically continuous ceramic microstructure. Therefore, our three-level HIPC has demonstrated impressive mechanical and thermal enhancement with its exquisite hierarchical architecture. The hierarchical structural engineering approach also represents a paradigm shift from constructing single-scale IPCs to multi-scale HIPCs and can be extended to other material combinations for high-performance structural and functional materials.

Symbiotically engineered crystalline-amorphous nanostructure in a strong-yet-stable Al alloy with large twinning-induced plasticity

High performance structural materials with combinations of excellent yet often mutually exclusive properties such as high yield strength, ductility and thermal stability are primarily accessed by synthesizing heterogeneous microstructures. Age-hardened Al alloys with hierarchical nanoprecipitates manifest a good combination of strength and ductility compared to fully amorphous Al alloys, however their thermal stability is in general low, stem from the fast-diffusion element-driven coarsening of nanoprecipitates at elevated temperature. Utilizing the sluggish-diffusion element Cr in the Al matrix, we propose a novel strategy of architecting symbiotically crystalline-amorphous nanostructure (CANS) endowed with self-assembled Cr segregation at crystalline/amorphous interfaces, to develop thermally stable, ultrastrong and ductile Al alloys. The symbiotic CANS-AlCr alloys with homogeneous twinning-induced plasticity of ∼15% strains at room temperature have ultrahigh compressive yield strength of ∼1.75 GPa and outstanding thermal stability up to ∼623 K, simultaneously superior to the parent nanocrystalline and amorphous Al alloys. The interfacial Cr segregation not only promotes twinning-induced plasticity of crystals but also triggers dynamic elemental partitioning between interfaces and amorphous nanolayers, which is critical to their thermodynamic and mechanical stabilization of symbiotic CANS-AlCr alloys. Our strategy advances efficient creation of hierarchical nanostructure and offers a facile route that is regulated across atomic and nanoscopic scales to achieve desirable materials with diverse-yet-precise performances.

First principles prediction of yield strength of body centered cubic structured high entropy alloys

High entropy alloys (HEAs) with a body centered cubic (bcc) crystal structure have emerged as potential high-performance structural materials due to their high strength at room and elevated temperatures. In this study, a computational approach, based on the revised Peierls-Nabarro model and using the inputs solely calculated from the first principles density functional theory, has been developed to predict the yield strength of bcc HEAs. Examining its accuracy and reliability, the developed computational approach was applied to four different types of bcc HEAs. The yield strength was predicted to be 1034 MPa for MoNbTaW, 1489 MPa for MoNbTaV, 1356 MPa for AlCoCrFeNi, and 1740 MPa for AlCoCrFeNiZr0.3 alloy, respectively. These computational predictions are found to agree well with available experimental data. Moreover, the developed computational approach accurately quantifies the changes in the yield strength from MoNbTaW to MoNbTaV with a change of constituent W to V, and from AlCoCrFeNi to AlCoCrFeNiZr0.3 with addition of 6 at% Zr. Therefore, this first-principles based computational approach provides a way for expedite optimization on the mechanical properties of bcc HEAs across vast composition space.

Combining laminated bimodal heterostructure and dislocation source limitation for superior strength-ductility synergy

Many unremitting pursuits have been paid on designing microstructures to enhance the strength-ductility synergy of metallic materials. In this work, laminated bimodal heterostructure and dislocation source limitation were introduced together into pure Ni with various laminate thicknesses by electrodeposition and subsequent annealing to circumvent the limitations of the strength-ductility trade-off. The specimen, composed of alternative fine-grained and ultrafine-grained laminates with the optimized laminate thickness, had a combination of 601 MPa yield strength which was 4.8 times its Hall-Petch yield strength (124 MPa), and 24.5% reasonable ductility. The combination went beyond the range established by the reported pure Ni. When the fine-grained laminates started dislocation slip first and ultrafine-grained ones remained elastic, incompatible deformation between the two different laminates resulted in a high density of piled-up geometrically necessary dislocations (GNDs) against the interfaces, increasing the yield strength. Deformation incompatibility was also present in each of the individual laminates exhibiting bimodal structure, which further facilitated strengthening and strain hardening. Plentiful dislocation cells and walls were found to form inside the fine-grained laminates during work hardening, which could contribute to the production of GNDs. The carefully constructed heterostructures maximized the role of GNDs. Besides, dislocation source limitation induced further hardening, in the form of the yield-point behaviour, and ductilization which resulted from more room inside grains for the accumulation and interaction of dislocations. The superior strength-ductility synergy here paves a promising paradigm for designing high-performance structural metallic materials.

Microstructural evolution and mechanical properties of (FeCoNi)85·84Al7·07Ti7.09 high-entropy alloy by selective laser melting with aging treatment

Faced-centred cubic nanoparticles-strengthened FeCoNiAlTi system high-entropy alloy (HEA) has demonstrated unique mechanical performance advantages with recently developed HEA alloy compositions. One of the key factors determining the performance of an alloy is the efficient manipulation of precipitation. However, the traditional aging method used to achieve this can be problematic. It is time-consuming and difficult to accurately control the distribution of the precipitated phase, which restricts the development of new, high-performance structural materials. Consequently, researchers have been exploring alternative methods to more precisely and effectively manipulate precipitation in alloys. Here, we have utilized both high-efficiency additive manufacturing processes and a short-term aging process to produce (FeCoNi)85·84Al7·07Ti7.09 high-entropy alloys that exhibit outstanding mechanical properties with an ultimate tensile strength of 1625 MPa, yield strength of 1214 MPa and an elongation to failure of 11.6%. Our findings reveal the formation of L12 and L21 nanoparticles phases after aging treatment, and their contents gradually decrease with increasing aging treatment temperature. And, we introduce two strengthening mechanisms of dislocation strengthening and precipitation strengthening into the alloys, and realized the coexistence of high-density dislocations and precipitated phases, thereby exhibiting excellent comprehensive mechanical properties. This approach represents a promising new direction in the development of high-performance alloys, offering a more efficient and effective means of producing materials with improved properties.

All-natural and high-performance structural material based on lignin-reinforced cellulose

Sustainable materials derived from lignocellulosic resources are attractive alternatives to ubiquitous petrochemical plastics. However, it remains a huge challenge to improve the mechanical properties of lignocellulosic materials through efficient and low-energy processing strategy. Herein, we report a facile lignin-reinforced cellulose strategy to manufacture an all-natural and high-performance structural material from bamboo particles via partial delignification followed by hot-pressing. Partial delignification can regulate the amount of lignin in the bamboo particles and release internal cellulose microfibers. The subsequent hot-pressing drives residual lignin into the cellulose matrix to form a dense structure, which acts as a polyphenolic binder to improve the performance of the structural material. The obtained lignin-reinforced cellulose plate (LRCP) demonstrates high isotropic flexural strength (∼162 MPa), which is higher than that of natural bamboo and typical petrochemical plastics. Moreover, LRCP shows outstanding toughness (∼2.58 MPa m1/2), excellent compressive strength (∼178 MPa), improved wet stability and superior flame resistance. LRCP is all-natural and eco-friendly without the need for additional chemical cross-linking reagents. We believe that this facile and cost-effective strategy provides a promising way to process lignocellulosic resources into all-natural and high-performance structural materials that can serve as powerful plastic alternatives in the future.

Automated trackspinning of aligned lignin fibers as precursors of green carbon nanofibers

At present, most carbon fibers are made from non-renewable polyacrylonitrile. Substantial efforts have been made to replace petroleum-based precursors for carbon fiber production. Interestingly, lignin is a carbon fiber precursor material that is cheap, highly available and sustainable. Submicron-scale lignin-based carbon nanofibers are used in numerous areas, such as electronic devices, batteries, supercapacitors and low-cost, high-performance structural composite materials. Trackspinning (TS) technology offers a way to scale up the versatile, but inefficient contact drawing technique to produce small-diameter lignin fibers from environmentally friendly aqueous solutions. In this study, the effects of TS based on probe drawing of low-concentration lignin nanofibers blended with poly(ethylene oxide) and glycerol in sodium hydroxide (NaOH) solution were investigated. The TS lignin fibers were well aligned and reached diameters as small as 500–1000 nm as the drawing length was increased. Lignin fiber macromolecular alignment was isotropic at low levels of draw, and the dichroic ratio increased from 1 to 2.25 with doubling of the drawing length. The most highly drawn trackspun lignin fibers had a mechanical strength of 3.92 MPa and a Young’s modulus of 2.15 GPa, which were similar to reported values for solvent-electrospun lignin nanofibers. These findings support the potential to utilize TS to produce small-diameter lignin fibers using a simple aqueous solvent approach.