Maximum Toughness Research Articles

Interfacial Hydrogen Bond-Reinforced Adhesion and Cohesion Enabling an Ultrastretchable and Wet Adhesive Hydrogel Strain Sensor.

Historically, research on silicotungstic-acid-based hydrogels has primarily focused on their adhesive properties, often at the expense of mechanical strength (cohesion). In this study, we present a novel approach to fabricate a polysaccharide hydrogel that harmoniously balances both adhesion and cohesion via interfacial hydrogen bonds. This hydrogel, composed of carboxymethyl cellulose (CMC), polyacrylamide (PAM), silicotungstic acid (SiW), and lithium chloride (LiCl), showcases a unique combination of properties: strain-responsive ionic conductivity, superior transparency, remarkable stretchability, and robust adhesion. Contrary to conventional PAM hydrogels, our PAM-SiW networked hydrogel addresses the common challenge of achieving good adhesion without compromising on cohesion. Specifically, our hydrogel demonstrates a maximum toughness of 20.3 MJ/m3 and a strain of 4079%, an accomplishment rarely observed in other adhesive hydrogel. Furthermore, the hydrogel's adhesion is both reversible and versatile, adhering effectively to a variety of wet and dry substrates. This makes it a promising candidate for advanced healthcare applications, particularly as a mechanically reinforced underwater adhesive with unparalleled stability. We also provide insights into the role of LiCl in the hydrogel matrix, emphasizing its influence on electrostatic interactions without affecting the hydrogen bonds. This study serves as a testament to the potential of harmonizing adhesive and cohesive properties in hydrogels, paving the way for future innovations in the field.

Microstructure and Mechanical Properties of IN690 Ni-Based Alloy/316LN Stainless-Steel Dissimilar Ring Joint Welded by Inertia Friction Welding.

Inertia friction welding (IFW) was used to join large-diameter hollow bars made of Inconel 690 and 316LN successfully. The interfacial characteristics, microstructure, mechanical properties and fracture mechanism of welded joints under different process parameters were investigated. The results indicated that a joining mechanism with mechanical interlocking and metallurgical bonding was found in IFW joints. There was a significant mechanical mixing zone at the welding interface. The elemental diffusion layer was found in the "wrinkles" of the mechanical mixing zone. A tiny quantity of C elements accumulated on the friction and secondary friction surfaces. The tensile strength and impact toughness of the joints increased with the total welding energy input. Increasing the friction pressure could make the grain in all parts of the joint uniformly refined, thus enhancing the mechanical properties of welded joints. The maximum tensile strength and impact toughness of the welded joint were 639 MPa and 146 J/cm2, reaching 94% and 68% of that for Inconel 690, respectively, when the flywheel was initially set at 760 rpm, 200 MPa for friction pressure, and 388 kg/m2 for rotary inertia. Due to the Kirkendall effect in the welded joint, superior metallurgical bonding was at the welding interface close to the Inconel 690 side compared to the 316LN side.

Investigating the applicability of deep learning and machine learning models in predicting the structural performance of V-shaped RC folded plates

Reinforced concrete folded plates (RC-FPs), which are a special class of shell structures, have recently become very popular in modern architectural and engineering applications because of the need for lightweight and aesthetic structures to cover large areas. However, it is known that studies on the structural performance of RC-FPs are insufficient. Therefore, this article presents a study on the development and comparison of different deep learning (DL) and machine learning (ML) models for the prediction of the structural performance of full-scale V-shaped RC-FPs produced from hybrid fiber-reinforced self-consolidating concrete (HFR-SCC) having different plate thicknesses (50, 60, 70, and 80 mm), fiber volumes (1.00% and 1.25%), and combinations (single, binary, and ternary). While vanilla long short-term memory (VLSTM) and bidirectional long short-term memory (BILSTM) are used as DL models, random forest (RF), extremely randomized trees (ERT), and adaptive boosting (AdaBoost) are preferred for ML models. To construct the models, the structural performance results of a total of 44 full-scale V-shaped RC-FPs subjected to four-point bending loading were adopted as the database. In addition to all these, the AdaBoost model is used to determine the relative feature importance of the input parameters. Based on the results, among the DL models, the BILSTM has the best ability to predict the structural performance values of V-shaped RC-FPs (such as R-squared values for maximum load-bearing capacity, cracking load, toughness, and deflection ductility are 0.934, 0.987, 0.972, and 0.812, respectively), while in ML models, this is valid for the ERT (such as R-square values are 0.917 for maximum load-bearing capacity, 0.936 for cracking load, 0.947 for toughness and 0.825 for deflection ductility). On the other hand, DL models predicted all other structural performance values better than ML models, except for deflection ductility. Besides, the most relative important input features for maximum load-bearing capacity and toughness values is plate thickness, whereas for cracking load and deflection ductility values compressive strength is important. In conclusion, it can be emphasized that the use of DL models can provide significant advantages in engineering applications, such as predicting the structural performance of V-shaped RC-FPs.

Fracture behaviors of nacre-like composites via phase-field fracture modeling

Nacre-inspired composites, composed of hard and soft phases, exhibit exceptional combinations of stiffness, strength, and fracture toughness. However, the fracture behaviors of these composites are significantly influenced by the geometric factors and material properties of their constituents. In this study, we systematically investigate the fracture behaviors of nacre-like composites by employing a phase-field fracture model considering the effects of oblique angle between loading and platelet directions, a critical factor often overlooked in previous studies, coupled with the effect of other geometric and material parameters, such as the aspect ratio, Young's modulus and fracture toughness ratio between hard and soft phase. Our findings highlight the significant influence of the oblique angle on the mechanical properties and fracture behaviors of these composites. Particularly, it is found the maximum Young’s modulus and strength are obtained when the direction of hard platelet is aligned with the tension direction, while the maximum toughness is achieved at a moderate oblique angle, especially in cases of large aspect ratios, small Young's modulus and fracture toughness ratios between the hard and soft phases. Besides, the maximum fracture toughness is more likely to be obtained at a small aspect ratio and large Young's modulus ratio between hard and soft phases. The insights gained from our study would offer valuable guidance for the design and practical application of nacre-mimetic composites.

Properties of Ultra-High Performance Concrete incorporating iron tailings powder and iron tailings sand

Iron tailings (IT) is a kind of solid waste, which is usually divided into iron tailings powder (ITP) and iron tailings sand (ITS). It has been reported that IT has potentials to be used in ultra high performance concrete (UHPC). However, the recovery rate of IT is relatively low, and rare research mentioned the co-utilization of ITP and ITS to get full-scale use of IT. Therefore, in this study, ITP and ITS with different replacement ratio were used to replace cement and quartz sand, respectively, in UHPC. The effects of ITP and ITS substitution on the mechanical properties, microstructure, hydration products, durability and environmental evaluation of UHPC mixtures were studied. The optimal ITP replacement ratio is 20% that 20% ITP-contained UHPC mixtures had better mechanical properties. Further increasing the ITS replacement ratio, the mechanical properties initially increased and then suffered a reduction. The UHPC with 20% ITP and 50% ITS had the maximum compressive strength (145.6 MPa) and flexural toughness (110.99 N·m). Appropriate addition of IT could improve the microstructures of UHPC mixtures by its filler effect and pozzolanic potential. The average pore diameter was reduced from 97.00 nm to 27.04 nm, and the ratio of harmful pores (＞ 100 nm) was reduced from 85.7% to 60.9% when ITP and ITS were added. In the durability tests, the addition of IT has less effect on the electric flux passed. Owing to the pores refining effect of IT, the drying shrinkage of UHPC mixtures was reduced. According to the environmental evaluation, the amount of leached heavy metal ions can be neglected. The IT contained UHPC had relatively low green degree and ITS/ITP surplus in 1 m3 UHPC production which implies its good environmental performance. Overall, ITP and ITS can be co-used in developing environmentally friendly UHPC to minimize the environmental burdens.

Augmenting the mechanical performance of three‐dimensional woven composites by the synergistic effect of fabric architecture and interfacial interaction of carbon nanotubes

AbstractThree‐dimensional (3D) woven fabrics offer many advantages over planar woven fabrics for composite applications. Because of the complex structure of 3D woven fabrics, an in‐depth investigation is needed to understand the effects of fabric architecture and nanofillers on the mechanical and failure behavior of 3D woven composites. The present study investigates the effect of 3D woven ultrahigh‐molecular‐weight polyethylene (UHMWPE) orthogonal fabric architecture, with or without nanofillers, on the mechanical properties of composites. 3D woven orthogonal fabrics with varying proportions of stuffer‐to‐binder (S/B) yarns were manufactured and reinforced with an epoxy (EP) matrix. Multiwalled carbon nanotubes (MWCNTs) were infused as nanofillers to improve the interaction between the UHMWPE fabric and the EP matrix. 3D woven composite having an S/B ratio of 2:1 showed the maximum tensile strength and toughness. On the other hand, 3D woven composite with an S/B ratio of 4:1 showed higher flexural strength and impact resistance. The failure mechanism was also studied by examining the fractured surfaces of composites, which revealed matrix cracking, fiber pullout, predominant binder yarn failure, and yarn slippage. From this study, it is understood that for 3D fabric reinforcement, a balance between structural integrity and load‐bearing capacity of yarns is decisive, whereas for the matrix, the incorporation of MWCNTs is found to be advantageous.Highlights The role of structure of 3D woven orthogonal fabric on the mechanical behaviour of the UHMWPE‐epoxy composite is investigated. The addition of functionalized MWCNTs improves the tensile, flexural, and impact properties. The decisive role of the ratio of stuffer‐to‐binder yarns is established. Matrix cracking, debonding, and yarn failure are observed during tensile failure.

Fully biomass-derived polyurethane based on dynamic imine with self-healing, rapid degradability, and editable shape memory capabilities

In this study, a novel bio-based diol containing imine dynamic bonds (Vanp2) were synthesized using vanillin and bio-based 1,5-pentanediamine. Vanp2 was then introduced into the cross-linking network of betulin-based polyurethanes to obtain betulin-based polyurethanes containing covalent adaptive networks (CANs). Imine dynamic bonds within CAN endowed these betulin-based polyurethanes with self-healing, re-processability, degradability, and editable shape memory functionalities. Meanwhile, the mechanical and thermal properties of these fully bio-based polyurethane materials were characterized. The maximum tensile strength reached 9.5 MPa, while the maximum strain at break was 248 % and the maximum toughness was 13.2 MJ/m3. Thermal decomposition temperature was greater than 300 °C. Since the imine structure could be dissociated under acidic conditions, these polyurethanes could be rapidly degraded in a mixed acid solution at 50 °C in 4 h. This study demonstrated a strategy for synthesizing betulin-based polyurethane elastomers containing CAN using only bio-based feedstock.

4D printed and multi-stimulus responsive shape memory polymer nanocomposites developed on hydrogen bonding–metal-phenolic sacrificial network: Application for hazardous chemical operations soft robots

Designing 4D printed shape memory polymers (SMPs) with mechanical robust and multi-stimulus responses applied in soft robot holds vast promise. While significant progress has been made in this area, implementing SMP composites with multi-stimulus response capabilities for fused filament fabrication (FFF) 4D printing typically sacrifices the inherent mechanical properties of the materials, limiting the requirements for robust and tough applications of SMP in soft robotics. In this work, Fe3O4 nanoparticles are employed as functional particles, and the "hydrogen bonding–metal-phenolic" sacrificial network in the nanoparticles and polymer is designed to achieve NIR light and magnetic stimulation response without sacrificing the maximum strength and toughness of the 4D printable SMP. The SMP nanocomposite developed from the sacrificial network has a tensile strength of 18.98 MPa and an elongation at break of 897 %, a 40 % increase in strength and 196 % increase in elongation at break compared to SMP nanocomposites with direct Fe3O4 addition. In addition, the shape-programmable soft robot with NIR light and magnetic stimulation response is developed based on 4D printing. The remote precision control and drugs release demonstrates the potential application of 4D printed soft robots in hazardous chemical operations.

Bone-like apatite formation in biocompatible phosphate-crosslinked bacterial cellulose-based hydrogels for bone tissue engineering applications

Addressing major bone injuries is a challenge in bone regeneration, necessitating innovative 3D hydrogel-based therapeutic approaches to enhance scaffold properties for better bioactivity. Bacterial cellulose (BC) is an excellent scaffold for bone tissue engineering due to its biocompatibility, high porosity, substantial surface area, and remarkable mechanical strength. However, its practical application is limited due to a lack of inherent osteogenic activity and biomineralization ability. In this study, we synthesized bone-like apatite in biocompatible BC hydrogel by introducing phosphate groups. Hydrogels were prepared using fibrous BC, acrylamide (AM), and bis [2-methacryloyloxy] ethyl phosphate (BMEP) as a crosslinker through free radical polymerization (P-BC-PAM). P-BC-PAM hydrogels exhibited outstanding compressive mechanical properties, highly interconnected porous structures, good swelling, and biodegradable properties. BMEP content significantly influenced the physicochemical and biological properties of the hydrogels. Increasing BMEP content enhanced the fibrous structure, porosity from 85.1 % to 89.5 %, and compressive mechanical strength. The optimized hydrogel (2.0P-BC-PAM) displayed maximum compressive stress, toughness, and elastic modulus at 75 % strain: 221 ± 0.08 kPa, 24,674.2 ± 978 kPa, and 11 ± 0.47 kPa, respectively. P-BC-PAM hydrogels underwent biomineralization in simulated body fluid (SBF) for 14 days, forming bone-like apatite with a Ca/P ratio of 1.75, similar to hydroxyapatite. Confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM), this suggests their potential as scaffolds for bone tissue engineering. MC3T3-E1 osteoblast cells effectively attached and proliferated on P-BC-PAM. In summary, this study contributes insights into developing phosphate-functionalized BC-based hydrogels with potential applications in bone tissue engineering.

Digital light processing of customized elastic scaffolds by efficient thiol-yne crosslinking

Digital light processing (DLP) based 3D printing technology has the advantages of fast printing rate and high spatial resolution in the manufacture of tissue engineering scaffolds. However, the limited availability of printable materials for DLP technology, especially the lack of biodegradable elastomeric materials hinders the development of customized soft tissue scaffolds. Herein, liquid poly(4-methyl-ε-caprolactone) dialkynylate (PMCLDY) was prepared as a DLP printable ink based on efficient thiol-yne photocrosslinking. With the aid of photorheology and in situ FT-IR and tensile tests, an ink formulation for DLP printing was optimized as the P50 ink (PMCLDY to diluent PEGDY mass ratio of 1), which possessed fast cure rates (<15 s), low viscosity (<2 Pa·s), moderate mechanical properties (failure strain > 40 %) and maximum toughness (0.153 MJ·m−3). A commercial DLP printer equipped with the P50 ink realized 3D scaffolds models with microstructure and macroscopic shape precisely. It was demonstrated that the 3D printed scaffold with biodegradability could withstand dynamic compression cycles. Furthermore, the cytocompatibility experiments showed that the scaffold could effectively support the growth and proliferation of rat bone marrow stromal cells (BMSCs). These results demonstrate that the P50 ink is a promising material for manufacturing elastic scaffolds by DLP printing for tissue engineering applications.

OPTIMIZATION OF PROCESS PARAMETERS FOR A SOLID-STATE-WELDED AISI 430 STEEL JOINT WITH THE GRG REINFORCED RESPONSE SURFACE METHODOLOGY

High-temperature applications such as heat exchangers and burner tubes employ AISI 430 steel. A larger heat-affected zone, undesired metallurgical changes and higher hardness in the weld area occur when fusion welding this type of steel. The study investigates the feasibility of welding ferritic stainless steel AISI 430, utilizing a solid-state method (continuous drive friction welding). The experiment uses an L27 orthogonal array and three levels of variation in the welding parameters such as frictional pressure, forging pressure, friction time, forging time and rotational speed. Tensile strength, axial shortening and impact toughness are the observed quality characteristics. In an integrated approach of the grey incidence reinforced response surface methodology, the benefits of the grey relational theory are merged with the statistical analysis of the response surface methodology to determine the ideal friction welding inputs (frictional pressure – 59.95 MPa, friction time – 4 s, upset pressure – 68.5 MPa, forging time – 3 s and rotational speed – 1399 min–1). The AISI 430 steel joint’s qualities are improved by 2.25, 12.74 and 7.89 % in terms of the maximum ultimate tensile strength, axial shortening and impact toughness, respectively.

Healable, degradable polyurethane elastomers with excellent mechanical properties based on multiple hydrogen bonds

AbstractDue to its comprehensive properties, polyurethane elastomer (PU) plays a vital role in ships, construction, transportation facilities, and other fields. However, it is challenging to design polyurethane elastomer materials with good mechanical properties, self‐healing ability, and degradable ability. Herein, a kind of polyurethane elastomer based on multiple hydrogen bond crosslinking was successfully synthesized by using polycaprolactone with substantial crystallization as a soft chain segment and introducing adipic dihydrazide (ADH) and U2‐diol (a ureido‐pyrimidinone with two hydroxyl groups at the end) to achieve ordered hydrogen bond assembly design and control. The elastomer has good tensile strength, healability, degradability, and solubility. The maximum tensile strength and toughness of the prepared polyurethane elastomer (PUAD) were 46.34 MPa and 687.66 MJ/m3, respectively. With the increase of U2‐diol content, the self‐repair efficiency was greatly enhanced. After seven repair cycles, the self‐repair efficiency can still reach 66.88%. In addition, the bacterial degradation test using Pseudomonas aeruginosa as a strain showed that PUAD film had excellent degradability. The dissolution test with N,N‐dimethylformamide (DMF) as solvent showed that the tensile strength was almost unchanged after three dissolutions.

Interface-dominated deformation mechanisms in Cr/CrN/Cr-DLC multilayer triggered by nanoindentation

The diamond-like carbon (DLC) film traditionally possesses low toughness owing to high intrinsic compressive stress. The incorporation of other elements into the DLC film provides an effective approach to improving toughness, but it is still limited and produces some detrimental effects. In this study, a new strategy of designing the Cr/CrN multilayers to serve as a functional transition layer and doping Cr into DLC film is attempted to simultaneously improve the strength and ductility of DLC film. Herein, a profound understanding of the deformation mechanisms of Cr/CrN/Cr-DLC multilayers with different bilayer periods (BPs) during the indentation process is investigated. The maximum strength and toughness values are achieved by the Cr/CrN/Cr-DLC multilayer with BP of 10 nm (P10). The cooperation of multiple strengthening mechanisms involving the diminishment of dislocation motion within individual layers and the formation of coherent twin boundaries (CTBs) and Lomer-Cottrell locks (L-C locks) contributed significantly to the high hardness of P10. The predominant toughening mechanism of P10 is the formation of a substantial number of high-density stacking faults (SFs) in CrN sublayers, which is attributed to that the pre-existed CTBs with numerous kinks in CrN can reduce the stacking fault energies (SFEs) for P10. Few deformation twins facilitated the deformation of P10. In contrast, a versatile deformation mechanism appears in Cr/CrN/Cr-DLC with BP of 100 nm (P100) involving dislocation motion, SFs, deformation twins, and, of particular note, amorphization. However, the released energy related to deformation in P100 is limited, leading to cracks in the Cr-DLC top layer. This multilayer structure can provide additional strengthening and toughening mechanisms to endow the DLC film with profound mechanical properties in harsh service conditions.

A novel damage evaluation method for ultra‐high‐performance fiber reinforced concrete under multiple impact loads

AbstractIn this study, repeated compression tests were conducted for ultra‐high‐performance fiber reinforced concrete (UHPFRC) under three different impact pressures. Results showed that as the impact number increased, the strain rate approximately showed a proportional increase, and the plateau region of the dynamic stress–strain curve became more prominent. Besides, when the repeated impacts increased, the maximum strain and dynamic toughness both exhibited upward trends, while the peak stress decreased. The average toughness was positively correlated with the strain rate. Additionally, under high repeated impact loads, a single crack propagated rapidly within the UHPFRC specimen after single impact. Conversely, cracks propagated from the center to the periphery on the surface of the specimen when repeated loads were low. Furthermore, a quantitative evaluation method for the damage of UHPFRC under repeated impact loads was proposed based on the characteristic parameters of the gray‐level co‐occurrence matrix (GLCM).

Effect of drying-wetting cycles on the durability of calcareous sand reinforced by MICP and recycled shredded coconut coir (RSC)

Microbial-induced carbonate precipitation (MICP) technique has been adopted in geotechnical engineering widely. In this study, the effect of drying-wetting cycles on MICP-recycled shredded coconut coir (RSC) reinforced calcareous sand was studied, and the deterioration mechanism under drying-wetting cycles was revealed. Test results indicated that drying-wetting cycles exert an important influence on the durability of MICP-RSC reinforced specimens. With the increase of drying-wetting cycles N, the specimens demonstrated significant increase in mass loss rate and critical void ratio, decrease in maximum shear modulus, peak strength and toughness. Furthermore, an increase in the initial relative density reduced the deterioration of MICP-RSC reinforced specimens exposed to drying-wetting cycles. Higher initial relative density of the specimen correlates with an increased maximum shear modulus, peak stress and toughness, a decreased in permeability and critical void ratio. Microanalysis revealed that the generated calcium carbonate adhering to sand particles and RSC gradually dropped off with the increase of N, weakened cementation, and led to the deterioration of MICP-RSC reinforced specimens, which is consistent with the deterioration characteristics under drying-wetting cycles.

A Comprehensive Study on the Effect of Highly Thermally Conductive Fillers on Improving the Properties of SBR/BR-Filled Nano-Silicon Nitride.

The effect of silicon nitride (Si3N4) as a thermally conductive material on the mechanical, microstructural, and physical properties as well as kinetics of the curing reaction of styrene-butadiene rubber/butadiene rubber (SBR/BR) was investigated in this work. The results showed an improvement in tensile, hardness, and compression features of the composite due to the presence of Si3N4. The properties were enhanced with the filler loading content; somehow, the composite including Si3N4 = 6 parts per hundred (phr) had the most significant performance, an increase of ∼15 and 20% in the maximum strain and toughness of the composite, respectively, an increase of almost 7% in the hardness, and an ∼13% reduction in the compression set. Also, the filler led to an increase in the crosslink density (calculated via the Flory-Rehner equation using swelling test) by 7.12 × 10-5 mol/g, proving the increment of the covalent bonds between the polymer chains during the curing reaction. The kinetic consideration revealed a reduction in the scorch and optimum curing times by ∼40 and ∼25%, respectively. In order to describe the kinetics of curing reaction of SBR/BR-Si3N4, an autocatalytic model based on the Kamal-Sourour model was applied on the rheometry results. The calculated kinetic parameters indicated that the thermally conductive Si3N4 accelerated the curing reaction by ∼40%, particularly at Si3N4 = 6 phr. After 6 phr of Si3N4, agglomeration of the filler particles decreased its performance.

Facile preparation and properties of porous poly(vinyl alcohol)/trehalose/nano-clay hydrogels with high mechanical strength for potential application in bone tissue engineering

Among various biomaterials, hydrogels are considered as the most attractive tissue engineering material due to their resemblances to extracellular matrix. However, due to the poor mechanical properties, poly(vinyl alcohol) hydrogels are restricted to be applied in load-bearing tissue repair and regeneration. In this work, we designed a series of porous biocompatible composite hydrogels with tough mechanical properties for bone tissue engineering, consisting of poly(vinyl alcohol), trehalose and nano-clay. These novelty hydrogels were prepared by a facile one-pot method. Compositions, microscopic structures, and mechanical properties of hydrogels were investigated in detail. The maximum compressive strength, compressive modulus, tensile strength, elastic modulus, and toughness of hydrogels attained about 2.71 MPa, 0.163 MPa, 0.741 MPa, 0.084 MPa, and 0.94 MJ/m3, respectively. These as-prepared hydrogels exhibited the excellent mechanical properties, which were ascribed to the hydrogen bond interactions between molecules and nano-enhancement effect of the nano-clay. Meanwhile, as-prepared hydrogels also exhibited a three-dimensional and interconnected porous microstructure, which facilitated the transport of nutrients to promote cells growth. In addition, the mechanical properties and microscopic structures of hydrogels could be controlled by adjusting the concentrations of trehalose and nano-clay. In vitro cell experiments demonstrated that the hydrogels had good biocompatibility. And hydrogels possessed the excellent ability to induce MC3T3-E1 cells osteogenesis to accelerate bone defects repair. Above illustrated results demonstrated that the potential applications of the hydrogels used as bone tissue engineering materials. Therefore, we anticipated this kind of poly(vinyl alcohol)-based composite hydrogel could develop a new strategy for bone tissue repair.

Inorganic-Organic Double Network Ionogels Based on Silica Nanoparticles for High-Temperature Flexible Supercapacitors.

Herein, we demonstrate an inorganic-organic double network gel electrolyte consisting of a silica particle network and a poly-2-hydroxyethyl methacrylate network in which 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquids are confined. The as-synthesized double network ionogel electrolytes exhibited high ion conductivity of 3.8 to 12.8 mS cm-1 over a wide temperature range of 30 to 150 °C and mechanical integrity with a maximum toughness of 1.8 MJ m-3 at 30 °C. These remarkable properties of the ionogel were associated with the formation of an optimal physical network of the silica nanoparticles in the colloidal dispersion. Accordingly, a flexible supercapacitor using ionogel electrolytes and reduced graphene oxide electrodes delivered energy and power densities of 48 Wh kg-1 and 4 kW kg-1, respectively, even at a high temperature of 120 °C, demonstrating excellent long-term stability that retains 93% of the initial capacitance even over 10,000 charge/discharge cycles at 120 °C.

Preparation and properties of Schiff base fluorescent hydrogels with high strength and toughness based on multiple hydrogen bonding and hydrophobic association

AbstractThe preparation of hydrogels with excellent mechanical properties by the synergistic interaction of various non‐covalent bonds is one of the research focuses. However, the emerging applications put forward requirements on the function, in addition to the mechanical properties. Therefore, we prepared a physically cross‐linked Schiff base fluorescent hydrogel Poly(methacrylic acid‐co‐poly(ethylene glycol) methyl ether acrylate‐co‐(Z)‐N‐(4‐(2‐((1H‐indol‐3‐yl)methylene)hydrazino‐1‐carbonyl)phenyl)methacrylamide) (P(MAA‐PEGA‐IHPMA)) by solvent exchange method, which greatly improved the mechanical properties of the hydrogel, and realized the versatility of the hydrogel. The hydrogel improved the binding energy and crosslinking density through the synergistic effects of non‐covalent bonds such as hydrophobic association, hydrogen bonding and metal complexation. Therefore, the hydrogel had excellent mechanical properties (the maximum tensile fracture stress and strain are 1.45 MPa and 401%, respectively, and the maximum toughness was 3.41 MJ/m3), and could be regulated by changing the content of IHPMA. Moreover, its fluorescence properties could be controlled by the concentration of Zn2+. In addition, P(MAA‐PEGA‐IHPMA) hydrogel also showed temperature response, solvent‐responsive fluorescence, antibacterial properties and shape memory function. The fluorescent hydrogel with high strength and toughness had potential applications in temperature control materials, anti‐fatigue materials and flexible sensors.

Selection of Electrode Material for Inconel 617/P92 Steel SMAW Dissimilar Welds

Abstract The present work aimed to investigate the microstructure and mechanical properties of the dissimilar shielded metal arc welded (SMAW) joint of Alloy 617 and P92 steel for advanced ultrasupercritical boilers. The SMAW joint was produced using three different types of electrodes, namely, ENiCrFe-3, ENiCrMo-3, and ENiCrCoMo-1. During microstructural observation of the welded joints, no possible cracking was detected in the weldments. The dissimilar metal welds (DMWs) obtained using the ENiCrCoMo-1 electrode showed the maximum tensile strength, while the minimum was obtained for the ENiCrFe-3 electrode. Among all the electrodes, the ENiCrFe-3 electrode exhibited the maximum impact toughness, while the minimum was obtained for ENiCrCoMo-1 electrodes. Based on microstructure and mechanical characterization, the ENiCrFe-3 electrode was selected as the best one among all to produce the DMW of Alloy 617 and P92 steel.