Excellent Tensile Properties Research Articles

Nickel catalysts with asymmetric steric hindrance for ethylene polymerization

α-Diimide catalysts have attracted widespread attention due to their unique chain walking characteristics. A series of α-diimide nickel/palladium catalysts with different electronic effects and steric hindrances were designed and synthesized for olefin polymerization. In this work, we synthesized a series of asymmetric α-diimide nickel complexes with different steric hindrances and used them for ethylene polymerization. These nickel catalysts have high ethylene polymerization activity, up to 6.51×10<sup>6</sup> g·mol<sup>−1</sup>·h<sup>−1</sup>, and the prepared polyethylene has a moderate melting point and high molecular weight (up to 38.2 × 10<sup>4</sup> g·mol<sup>−1</sup>), with a branching density distribution between 7 and 94 branches per 1000 carbons. More importantly, the polyethylene prepared by these catalysts exhibits excellent tensile properties, with strain and stress reaching 800% and 30 MPa, respectively.

Mechanical Properties and Development of Steel Fiber, Polypropylene Fiber and Steel-Polypropylene Fiber Concrete Structures

Fibre concrete is a commonly improved concrete. Compared with ordinary concrete, it has more excellent characteristics and has been widely used in engineering structures and other fields. This paper describes the mechanical properties of polypropylene fibres, steel fibres, and hybrid fibres (steel fibres and polypropylene fibres); it discusses the use and development of these three kinds of fibre concrete in various professional fields. Steel fibre concrete overcomes the shortcomings of concrete, such as low tensile strength, slight ultimate elongation, brittle, et al., with excellent tensile, flexural, shear, crack resistance, fatigue resistance, high toughness and other properties, has been applied in the field of hydraulics, roads and bridges, construction and other engineering fields. Polypropylene has better crack and impact resistance because of its ability to be uniformly dispersed in the concrete; chemically stable, simple construction has been widely used in the world. Steel-polypropylene hybrid fibre concrete has excellent mechanical properties and economy due to the integration of steel fibres and polypropylene fibres with high strength and toughness. It has a broader prospect in the application of engineering materials.

Skin-Inspired, Highly Sensitive, Broad-Range-Response and Ultra-Strong Gradient Ionogels Prepared by Electron Beam Irradiation.

Skin, characterized by its distinctive gradient structure and interwoven fibers, possesses remarkable mechanical properties and highly sensitive attributes, enabling it to detect an extensive range of stimuli. Inspired by these inherent qualities, a pioneering approach involving the crosslinking of macromolecules through in situ electron beam irradiation (EBI) is proposed to fabricate gradient ionogels. Such a design offers remarkable mechanical properties, including excellent tensile properties (>1000%), exceptional toughness (100MJ m-3), fatigue resistance, a broad temperature range (-65-200°C), and a distinctive gradient modulus change. Moreover, the ionogel sensor exhibits an ultra-fast response time (60ms) comparable to skin, an incredibly low detection limit (1kPa), and an exceptionally wide detection range (1kPa-1MPa). The exceptional gradient ionogel material holds tremendous promise for applications in the field of smart sensors, presenting a distinct strategy for fabricating flexible gradient materials.

Microstructural feature-driven machine learning for predicting mechanical tensile strength of laser powder bed fusion (L-PBF) additively manufactured Ti6Al4V alloy

The rapid solidification inherent in laser powder bed fusion (L-PBF) additive manufacturing (AM) introduces segregation phenomena and formation of non-equilibrium phases in duplex titanium alloy components, thereby impeding their suitability for high-reliability engineering applications. Consequently, heat treatment becomes indispensable for optimizing both the microstructure and mechanical properties to meet application requirements. This study aims to investigate the influence of varied annealing temperatures on the evolution of L-PBF-built Ti6Al4V alloy microstructure, subsequently elucidating their impact on tensile properties by analyzing of L-PBF process parameters, building orientations, and annealing temperatures. The findings reveal that annealing at 850 °C for 2 h facilitates the transformation of brittle martensite into a ductile lamellar (α + β) microstructure, thereby conferring excellent tensile properties upon the L-PBF-built Ti6Al4V alloy. Furthermore, to accurately predict the tensile strengths of the Ti6Al4V, we take into account the L-PBF process parameters and the as-built microstructures in a comprehensive manner, extracting the pertinent microstructural features. A machine learning (ML)-based model is built to facilitate accurate predictions. Accurate and reliable predictions are demonstrated by this model when applied to Ti6Al4V. This data-driven approach establishes a novel avenue for AM material property prediction and process parameter optimization.

Effect of Al on microstructure and mechanical properties of HPDC Mg-6Y-3Zn alloys

The effect of Al on microstructure and mechanical properties is investigated in novel Mg-6Y-3Zn (WZ63) alloys produced by high-pressure die-casting (HPDC). The morphology of (Al,Zn)2Y phase varies from lamellar to flower-like and then to block shape with 0.4–1.0 wt% Al. The HPDC alloys exhibit fine grain sizes ranging from 4 μm to 7.4 μm, and significant grain refinement is obtained with Al as low as 0.4 wt%, which is different from that in gravity casting. The (Al,Zn)2Y phase is the crack source, and the dimple depth and elongation (EL) reduce with increasing Al content. Still, all the studied HPDC WZ63-xAl alloys maintain excellent tensile properties, keeping 256–274 MPa for tensile strength (UTS) and 7.4–9.7 % EL at room temperature and 188–213 MPa UTS and 10–35 % EL at 250 °C. Optimal mechanical properties are obtained with Al content around 0.4–0.5 wt%.

Preparation and properties of electrochromic polyimide hybrid materials containing graphene oxide

The aminosylated graphene oxide was synthesized using the compound E3, three anhydrides (3,3′,4,4′ -diphenyl ether tetracarboxylic acid dianhydride, 3,3′,4,4′ -biphenyl tetracarboxylic acid di anhydride and 1,2,4, 5-phenyl tetracarboxylic acid di anhydride) is a series of electrochromic polyimide hybrid materials containing carbazole groups prepared by polypolymerization with aminated graphene oxide (F2). These PIs not only have good solubility and thermal properties,but also the introduction of 0.5 wt% GO increased the contact area between the film and electrolyte ions, which was beneficial to transport and diffusion of ions, thus improving the response speed of the electrochromic materials. Moreover, its excellent tensile properties make it an ideal material for manufacturing flexible devices. In addition, the polyimide hybrid materials exhibit excellent electrochemical and electrochromic properties as well as electrofluorescent properties. Therefore, the new material will be suitable for hole transmission, electrochromic, chemical sensing and other fields.

Achieving Record-High Stretchability and Mechanical Stability in Organic Photovoltaic Blends with a Dilute-absorber Strategy.

Organic solar cells (OSCs) have potential for applications in wearable electronics. Except for high power conversion efficiency (PCE), excellent tensile properties and mechanical stability are required for achieving high-performance wearable OSCs, while the present metrics barely meet the stretchable requirements. Herein, this work proposes a facile and low-cost strategy for constructing intrinsically stretchable OSCs by introducing a readily accessible polymer elastomer as a diluent for all-polymer photovoltaic blends. Remarkably, record-high stretchability with a fracture strain of up to 1000% and mechanical stability with elastic recovery>90% under cyclic tensile tests are realized in the OSCs active layers for the first time. Specifically, the tensile properties of best-performing all-polymer photovoltaic blends are increased by up to 250 times after blending. Previously unattainable performance metrics (fracture strain >50% and PCE >10%) are achieved simultaneously for the resulting photovoltaic films. Furthermore, an overall evaluation parameter y is proposed for the efficiency-cost- stretchability balance of photovoltaic blend films. The y value of dilute-absorber system is two orders of magnitude greater than those of prior state-of-the-art systems. Additionally, intrinsically stretchable devices are prepared to showcase the mechanical stability. Overall, this work offers a new avenue for constructing and comprehensively evaluating intrinsically stretchable organic electronic films.

Polymer-Entangled Spontaneous Pseudo-Planar Heterojunction for Constructing Efficient Flexible Organic Solar Cells.

Flexible organic solar cells (FOSCs) have attracted considerable attention from researchers as promising portable power sources for wearable electronic devices. However, insufficient power conversion efficiency (PCE), intrinsic stretchability, and mechanical stability of FOSCs remain severe obstacles to their application. Herein, an entangled strategy is proposed for the synergistic optimization of PCE and mechanical properties of FOSCs through green sequential printing combined with polymer-induced spontaneous gradient heterojunction phase separation morphology. Impressively, the toughened-pseudo-planar heterojunction (Toughened-PPHJ) film exhibits excellent tensile properties with a crack onset strain (COS) of 11.0%, twice that of the reference bulk heterojunction (BHJ) film (5.5%), which is among the highest values reported for the state-of-the-art polymer/small molecule-based systems. Finite element simulation of stress distribution during film bending confirms that Toughened-PPHJ film can release residual stress well. Therefore, this optimal device shows a high PCE (18.16%) with enhanced (short-circuit current density) JSC and suppressed energy loss, which is a significant improvement over the conventional BHJ device (16.99%). Finally, the 1cm2 flexible Toughened-PPHJ device retains more than 92% of its initial PCE (13.3%) after 1000 bending cycles. This work provides a feasible guiding idea for future flexible portable power supplies.

A novel configuration design of strong and ductile (TiC + Ti5Si3)/Ti laminated composites

To solve the low ductility of the uniformly particle-reinforced composites, novel (TiC + Ti5Si3)/Ti laminated composites are fabricated by electrophoretic deposition (EPD) silicon (Si) powders + graphene oxide (GOs) and spark plasma sintering (SPS) technology. The microstructure evolution, mechanical properties, strengthening and fracture mechanisms of laminated composites were systematically studied. Results show that the GOs and Si powders are evenly attached to Ti foils after EPD, and the (TiC + Ti5Si3) reinforcements are in situ formed at the interface after SPS. TiC phases are distributed along the original interface, and most of the Ti5Si3 reinforcements are located in the Ti foil matrix. The 50 μm - 120 s sample possesses obvious shell nacre containing particular ‘‘brick-and-mortar’’ architecture structure. And the 100 μm - 120 s sample displays excellent room temperature tensile properties, with the ultimate tensile strength (UTS) of 759 MPa, yield strength (YS) of 688 MPa and elongation (EL) of 24.3 %. The change of microstructure leads to the increase of strength, which is caused by the solid-solution strengthening, grain boundary strengthening and reinforcements strengthening. At this time, the design of laminated structure can change the crack propagation direction, extend the crack propagation path and thereby increases the energy required for crack propagation, obstructing the fracture of composites. This work provides an effective method to prepare Ti matrix composites with synergy of strength and ductility.

Preparation and characterization of shear thickening fluid/carbon nanotubes/Kevlar composite materials

AbstractShear thickening fluid (STF), carbon nanotubes (CNTs) are both promising in body protection and anti‐impact for the drastic viscosity change of STF and the extremely high tensile strength and elongation of CNTs. The excellent performance of the above two combined with traditional Kevlar fabrics can significantly improve the mechanical properties and reduce the number of layers used for body protection. This work reports a new method to prepare STF/CNTs/Kevlar with excellent tensile properties and anti‐impact performance by spraying method with 1 wt% polyvinyl alcohol (PVA) solution as a binder for better integration between CNTs and Kevlar. Surface morphology changes in the preparation process indicate the combined structure of PVA binder, CNTs, and STF, presenting a uniform macroscopic and nonuniform microscopic surface of STF/CNTs/Kevlar composite. The tensile strength and anti‐impact properties including punch residual velocity and energy absorbed were studied and results for STF/CNTs/Kevlar composite are 669.8 ± 18.1 MPa, 1.602 ± 0.045 m/s, and 21.683 ± 1.182 J in 12 ms, increased by 46.4%, 23.0%, and 240.2%, respectively, compared with neat Kevlar, owing to the improved tight bonding and friction between fabrics yarns caused by PVA adhesive and tangled CNTs, accompanied with the enhanced viscosity of STF under forces.Highlights Composites were made by spraying PVA, CNTs, and STF onto Kevlar fabrics; The tensile strength of the composite was 46.4% higher than Kevlar; The energy absorbed in 12 ms in anti‐impact tests was improved by 240.2%; Tight bonding and friction between yarns are reasons to improve properties; The raised viscosity of STF under forces is useful for mechanical properties.

Enhanced Dynamic Impact Resistance of 3D-Printed Continuous Optical Fiber-Reinforced Helicoidal Polylactic Acid Composites.

Characterized by light weight and high strength, composites are widely used as protective materials in dynamic impact loading under extreme conditions, such as high strain rates. Therefore, based on the excellent tensile properties of continuous fiber and the good flexibility and toughness of the bionic spiral structure, this study uses a multi-material 3D printer to incorporate continuous fiber, and then modifies the G-CODE file to control the printing path to achieve the production of a continuous fiber-reinforced Polylactic Acid composite helicoidal (spiral angle 60°) structure (COF-HP). Dynamic behavior under high-strain-rate impact experiments have been conducted using the Split Hopkinson Pressure Bar (SHPB). Stress-strain curves, impact energy curves and high-speed camera photographs with different strain rates at 680 s-1 and 890 s-1 have been analyzed to explore the dynamic process and illustrate the damage evolution. In addition, some detailed simulation models considering the incorporation of continuous optical fiber (COF) and different strain rates have been established and verified for deeper investigations. The results show that the COF does enhance the impact resistance of the laminates. When the porosity is reduced, the maximum stress of the continuous fiber-reinforced composite material is 4~7% higher than that of the pure PLA material. Our findings here expand the application of COF and provide a new method for designing protective materials, which have broad application prospects in the aerospace and automotive industries.

Fabrication of a twisted sensing yarn for multifunctional wearable applications

Nanofibers are ideal for the fabrication of fiber-based sensors owing to the wide applicability of such sensors in various fields. However, achieving high sensitivity and excellent tensile properties while maintaining high electrical conductivity in such sensors is difficult. This study proposes a simple fabrication method for a helical conductive yarn, core–sheath helical yarn (CSHY), in which the electrospun thermoplastic polyurethane (TPU) /boron nitride (BN) film is used as the fibrous material and coated with a liquid metal (LM), EGaIn. The fiber is then stretched and twisted to obtain the CSHY with high sensitivity, tensile stability, and durability as well as fast response and recovery. Experimental results show that the sensor fabricated by weaving the CSHY has a water contact angle of 143.2°, indicating that it can be used for human motion monitoring and underwater applications. In addition, the LM has excellent electrical conductivity and thermal conductivity and exhibits a synergistic effect with BN that is uniformly arranged along the fiber length. Thus, the fabric-based sensor exhibits excellent heat-dissipation, temperature-sensing, and electric-heating performances. Consequently, the proposed multifunctional smart yarn exhibits excellent strain sensing, self-controlled thermal management, and hydrophobic performance, with potential applications in future wearable electronics.

Lightweight Fe47Mn25Al13Cr7Ni5C3 medium-entropy alloy with enhanced mechanical properties

In this study, we designed a lightweight Fe47Mn25Al13Cr7Ni5C3 medium-entropy alloy (MEA) (calculated density of 6.803 g/cm3) with enhanced mechanical properties. The MEA samples were produced in three conditions with varying microstructures via thermomechanical processing. They achieved excellent tensile properties through strengthening mechanisms such as partial recrystallization, ultrafine grains, and M23C6 and B2 precipitates. Different strengthening mechanisms were applied depending on the annealing heat treatment conditions, resulting in three different strength-elongation combinations. Furthermore, the MEA, under all designed conditions, exhibited superior specific yield strength-uniform elongation and specific ultimate tensile strength-uniform elongation combinations compared to previously studied lightweight high-entropy alloys (HEAs) and lightweight steel. This was primarily attributed to the combination of benefits obtained from the low proportion of iron (47 at%) as a principal element and the large amount of aluminum addition (13 at%). The proposed MEA and its design strategy can satisfy the requirements for lightweight, cost-effective, strong, and ductile metallic materials, making a great contribution to the automotive industry in terms of crash resistance and fuel efficiency.

Transparent core-sheath composite fibers as flexible temperature sensor based on liquid crystal color change for smart sportswear

The characteristic of color changes in response to external temperature stimuli has made thermochromic fibers a subject of widespread research interest. However, for practical applications, improvements are still needed in terms of color rendering and the prevention of temperature-sensitive material leakage. This study utilized an optimized thermally induced coaxial dry spinning process to prepare a transparent temperature sensing fiber (PCCF) with a core-sheath structure. The sheath layer and the core layer of the PCCF were polydimethylsiloxane (PDMS) and cholesteric liquid crystal (CLC), respectively. The high transmittance exhibited by PCCF was attributed to the pellucid PDMS, which quickly cured in oil bath to form a complete core-sheath structure. The research results indicated that PCCF displayed uniform morphology (average diameter ∼539 μm), excellent tensile properties (elongation at break up to 183 %), as well as good mechanical, thermal, and sweat resistance stability. In addition, the PCCF showed a colorful variation of hues including yellow, green, blue and purple at a very narrow temperature change from 34 °C to 38 °C, attributing to that the molecular pitch was altered to selectively reflect visible light when the CLC was stimulated by temperature. Meanwhile, high sensitivity and short response time were obtained. When the PCCF was directly integrated into sportswear, the remarkable color changes could be observed as the wearer's body temperature increases. PCCF demonstrates a great potential application in smart sportswear and healthcare area.

Preparation of high strength Mg–Li–Zn–Y alloy by MgLi2Zn precipitation

For ultralight Mg–Li alloys, the improvement of strength is the most concerned issue. In this work, we successfully realize the incredible enhancement of strength in the Mg-8.5Li-7.5Zn-1.5Y alloy via a series of preparation processes, and the excellent tensile properties containing high yield strength of 312.4 MPa and good elongation of 14.2 % are obtained. Yield strength increment is as high as 213 MPa through deformation processing, which is rarely reported in Mg–Li alloys. Qualitative and quantitative studies reveal that the dislocation cutting of semi-coherent MgLi2Zn nano-precipitates is mainly responsible for such a high yield strength. The new finding for strengthening way is expected to contribute to the design of high-performance Mg–Li alloys.

2 GPa H13 steels fabricated by laser powder bed fusion and tempering: Microstructure, tensile property and strengthening mechanism

The successful manufacture of crack-free and highly dense H13 tool steel using laser powder bed fusion (LPBF) has been widely reported. Although the phases contain only martensite and some (<20 %) of residual austenite (RA), the differences in tensile properties are very large in previous studies. Here, the microstructure and tensile properties of the LPBF-fabricated H13 steels with different heat treatments were comparatively studied. Tensile strengths ranged ∼2.0–2.2 GPa for the optimal as-built and direct-tempered samples. By increasing the heat input, the RA content was reduced to 0.1 % and the microstructure contained only hierarchically fine martensite with improved tensile properties and anisotropy. Based on the full-martensitic microstructure in the optimal as-built samples, secondary hardening was achieved by direct tempering at 530–590 °C with tensile strengths of ∼2.1–2.2 GPa and improved elongations (4.93–6.43 %). The optimal direct-tempered samples yielded higher tensile strengths compared to the standard heat-treated counterparts. For the direct-tempered samples, the substantial retaining of the fine martensitic structure and high density of dislocations introduced by LPBF was the key to the excellent properties rather than the precipitates. This work elucidated the effect of the LPBF process, direct tempering, and standard heat treatment on the tensile property of H13 steel. It is concluded that process optimization for LPBF fabrication of H13 steel requires not only defect avoidance but also fine martensite and low-content RA. On this base, the LPBF-prepared H13 steel can be directly tempered to further obtain components with excellent tensile properties, which are superior to the standard heat-treated counterparts.

Strengthening mechanism of a Ni-based superalloy prepared by laser powder bed fusion: The role of cellular structure

The unique cellular structure has been reported to be the dominant reason for the remarkable mechanical properties in laser powder-bed fusion (LPBF) superalloys. However, the specific strengthening mechanism of the cellular structure needs to be further researched. In this study, the microstructure and tensile properties of a composition-optimized Haynes 230 alloy fabricated by the LPBF method were systematically investigated. The post-heated HT1 and HT2 samples with different cellular and grain structures served as the reference. The results show that the micron-scale grain and submicron-scale cellular structures are present in the as-built (AB) sample. The cellular boundaries are characterized by solute Nb segregation and high-density dislocations. The tensile tests show that the AB sample illustrates excellent tensile properties with ultimate tensile strength (UTS) of 1180.2 MPa, yield strength (YS) of 842.5 MPa and elongation (EL) of 29.3 %. The high YS mainly results from the strengthening effects of the cellular structure, which can be considered as a combination of dislocation and elemental segregation strengthening. The contribution of cellular structure to YS is much higher than that of GB strengthening. Furthermore, the deformation incompatibility of heterogeneous grain and cellular structures leads to high hetero-deformation induced (HDI) strengthening, which is also the primary reason for the abnormal upturn of strain hardening rate (SHR) in the AB sample.

Colored textiles based on noniridescent structural color of ZnS@SiO2 colloidal crystals for daytime passive radiative cooling

Passive radiative cooling (PRC) technology, which utilizes the optical properties of materials to achieve electricity-free and spontaneous cooling, holds great promise for energy conservation and combating global warming. Integrating PRC with textiles enables precise regulation of the microclimate of the human body, facilitating sustainable and effective individual thermal comfort. However, such PRC materials typically exhibit a white or mirror-like appearance to minimize solar energy absorption, severely limiting their aesthetic appeal and practical application in real-life scenarios. Herein, we present a colored textile for PRC by employing the spray coating method with noniridescent structural color pigments consisting of carbon-modified ZnS@SiO2 core–shell microspheres (colloidal crystals). This approach simultaneously achieves noniridescent colors and efficient cooling. By using the photonic properties of ZnS and the core–shell structure, the ZnS@SiO2 colored textile selectively reflects visible light, resulting in coloration while reducing solar absorption. Furthermore, the phonon resonance (Fröhlich mode) of the SiO2 shell ensures high emissivity of the ZnS@SiO2 colored textile within the atmospheric window, allowing for substantial radiative heat dissipation. Outdoor experiments demonstrate that both the green and amaranth ZnS@SiO2 textiles could lower the simulated skin temperature by 5 ∼ 6 ℃ in direct sunlight, compared to ZnS and dye textiles of the same hue. Additionally, the ZnS@SiO2 colored textiles also exhibit excellent softness, washability, hydrophilicity, breathability, and tensile properties, making them suitable for practical applications. This work not only provides a practical method for synthesizing noniridescent structural color pigments with high color saturation but also offers new insights into the design of colored passive radiative cooling textiles.

Sub-rapid solidified high copper-bearing steel with excellent resistance to hot shortness

The removal of accumulated impurity elements during scrap refining has been regarded as the bottleneck to limiting scrap usage, among which copper is the crucial tramp element in scrap steel recycling, resulting in the final product's hot shortness and surface cracking. This study proposes sub-rapid solidification-based strip casting technology to eliminate the copper impurity introduced problems. The results reveal that strip casting could improve copper behavior in the as-cast sample. More importantly, the sub-rapid solidified sample has excellent high-temperature tensile properties and resistance to hot shortness. It suggested that strip casting technology could produce copper-bearing steel, which can tackle the hot shortness problem and provide a unique idea for steelmaking with scrap as raw materials.

Microstructural Evolution and Mechanical Behavior of Co‐Free (Fe40Ni30Cr20Al10)100−xTix High‐Entropy Alloys

In this work, microstructural evolution and mechanical behavior of Co‐free (Fe40Ni30Cr20Al10)100−x Ti x (x = 0, 2, 4, 6, and 8 at%) high‐entropy alloys (HEAs) are investigated. All as‐cast HEAs consist of face‐centered‐cubic (FCC)‐ and body‐centered‐cubic (BCC)‐structured phases, wherein the BCC‐structured phase is composed of disordered BCC (A2) and ordered BCC (B2) phases. The HEAs show FCC dendrite and BCC inter‐dendrite microstructure when x ≤ 4. As the Ti content increases to 6 and 8 at%, the microstructure evolves from dendrite structures to complex lamellar structures, leading to a significant loss in ductility. With the increase of Ti, the strength is enhanced with the sacrifice of ductility. The (Fe40Ni30Cr20Al10)96Ti4 alloy exhibits promising combinations of strength and ductility, displaying a yield strength of 680 MPa, an ultimate tensile strength of 1132 MPa, and a total elongation of 16.6%. The simple FCC + BCC dendrite microstructure and optimal content of the BCC‐structured region containing A2 + B2 phases are responsible for the excellent tensile properties of the as‐cast (Fe40Ni30Cr20Al10)96Ti4 HEA. In this work, it is suggested that good combinations of strength and ductility of low‐cost Co‐free FeNiCrAl‐based HEAs can be achieved by tailoring Ti addition.