Graphene Oxide Inhibits Calcium Carbonate Nucleation.

Formation of minerals such as calcium carbonate often causes energy consumption and even safety risk increase due to the hindrance on heat/mass transfer. However, the current antiscalants are not efficient enough because of the poor understanding of the scale inhibition mechanisms. Here, we report an ultrahigh-performance antiscalant, graphene oxide (GO), which exhibits an outstanding nucleation inhibition effect far better than the current state-of-the-art antiscalants even on a subppm dosage. Our experiments reveal that the superior nucleation inhibition effect of GO is attributed to its limiting effect on the nucleation kinetics of ions and its ability to increase the nucleation barrier of calcium carbonate by altering the normal pathway of calcium carbonate polymorph formation. Further analysis indicates that the ion-limiting effect and the polymorph control ability of GO may stem from its oxygen functional group-rich surface chemistry and two-dimensional (2D) planar features, which endow GO with a Ca2+ binding ability and additional steric hindrance for CO32- diffusion, respectively.

Effect of Nb on the Damping Property and Pseudoelasticity of a Porous Ni-Ti Shape Memory Alloy.

In order to develop novel high damping materials with excellent pseudoelasticity (PE) properties to meet the application requirements in aerospace, medical, military and other fields, porous Ni50.8Ti49.2 shape memory alloy (SMA) was prepared by the powder metallurgy method. Different contents of Nb element were added to regulate the microstructures. It was found that after adding the Nb element, the number of precipitates significantly decreased, and the Nb element was mainly distributed in the Ni-Ti matrix in the form of ß-Nb blocks surrounded by Nb-rich layers. Property tests showed that with the increase in Nb content, the damping and PE increased first and then decreased. When the Nb content reached 9.0 at.%, the highest damping and the best PE could be achieved. Compared with the porous Ni-Ti SMA without Nb addition, the damping and PE increased by 60% and 35%, respectively. Correlated mechanisms were discussed.

Microstructural Evolution and Mechanical Properties of Pure Aluminum upon Multi-Pass Caliber Rolling.

The paper presents the microstructure and mechanical property of pure aluminum (Al) fabricated by multi-pass caliber rolling at room temperature. The finite element modeling (FEM) simulation was performed to explore the changes in rolling force, effective stress and strain, and temperature under various rolling passes. As the number of rolling passes increased, the overall temperature, effective stress, and strain gradually increased, while the maximum rolling force decreased. In addition, due to the dynamic recrystallization (DRX), the average grain size reduced from 1 mm to 14 µm with the increase in rolling passes. The dislocation density increased and it gradually evolved into the high-angle grain boundaries (HAGBs). Moreover, the initial cubic texture rotated to the brass component and finally changed to a mixture of Cube and Brass types. The highest tensile yield strength (TYS), ultimate tensile strength (UTS) and elongation (El.) of caliber rolled pure Al (116 MPa, 135 MPa, and 17%, respectively) can be achieved after 13 rolling passes, which mainly attributed to grain refinement.

End Group Modification for Black Phosphorus: Simultaneous Improvement of Chemical Stability and Gas Sensing Performance.

Black phosphorus (BP) nanosheets have been receiving attention for gas sensing showing superior sensitivity and selectivity among various two-dimensional materials. However, the instability of BP nanosheets due to chemical degradation, especially in humid environments, has severely limited their potential applications. Here, we propose to control the chemical stability of BP nanosheets through modifying their end groups via silanization treatment. Compared with other chemical passivation methods, the end group modification strategy proposed here can be well-controlled and results in little variation in the electronic structure of the puckered phosphorus plane. The results show that modification with fluoroalkylsilane leads the hydrophilic BP to become hydrophobic and exhibits extended chemical stability in oxidizing, humid environments. The sensitivity of fluoroalkylsilane-modified BP (F-BP) to NO2 improved by 3.9-fold in comparison with that of pristine BP nanosheets. More importantly, the NO2 sensing response could remain stable under changing relative humidity ranging from 5% to 95%. Such excellent sensing performance is ascribed to the strong interaction between NO2 and BP decorated with fluoroalkylsilane, as confirmed by density functional theory calculations. This work offers an effective means for preventing degradation of BP in ambient environments and provides a promising solution to solve the issue regarding humidity dependence in gas sensors.

MXene-Derived TiO2 Nanoparticles Intercalating between RGO Nanosheets: An Assembly for Highly Sensitive Gas Detection.

Tight stacking between two-dimensional (2D) sheet-like materials, such as graphene, in the solid state is a major challenge hindering their applications, especially in the gas sensing field. Here, we report on a TiO2 nanoparticle-spaced reduced graphene oxide (RGO) assembly for the design of highly sensitive gas sensors. The TiO2 nanospacers are derived from a 2D MXene that is intercalated between RGO sheets. The produced TiO2-spaced RGO assembly exhibits a uniform nanoparticle distribution and highly wrinkled RGO sheets that interconnect in micrometer-scale pores. The space limitation between adjacent RGO sheets can restrict the particle growth and lead to the formation of TiO2 nanoparticles with uniform diameters of ca. 6.2 nm. The sensitivity of the TiO2-spaced RGO sensor to NO2 improved by over 400% in comparison with pure RGO due to the more available surface area and active adsorption sites. Furthermore, fast response and recovery, excellent selectivity and flexibility, and reliable workability in a humid environment (with the relative humidity ranging from 5 to 95%) were also simultaneously achieved, demonstrating great potential for next-generation wearable sensors.

Nanoporous Co and N-Codoped Carbon Composite Derived from ZIF-67 for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have nice prospects because of their excellent energy density and theoretical specific capacity. However, the dissolution of lithium polysulfides and shuttle effects lead to a low coulombic efficiency and cycle performance of Li-S batteries. Therefore, designing electrode materials that can suppress the shuttle effect and adsorb polysulfides is of great significance. In this work, a Co and N-codoped carbon composite via heating a type of Co-etched zeolitic imidazolate framework-67 (ZIF-67), nanocube precursor, in inert gas is reported as a cathode sulfur carrier material for Li-S batteries. The experimental results show that high-temperature carbonization results in mesoporous structures inside the material which not only provide ion channels for the reaction but also improve the adsorption capacity of polysulfides. Furthermore, the exposed metal Co sites and N atoms can also inhibit the shuttle effect. When the annealing temperature is 600 °C, the sulfur composite exhibits a good cycling stability and rate performance. The cathode showed an improved initial specific capability of 1042 and still maintained 477 mAh g-1 at the rate of 1 C (1 C = 1672 mA g-1). Furthermore, at 5 C, a stable specific discharge capacity of 608 mAh g-1 was obtained.

Three-Dimensional Ordered Mesoporous Carbon Spheres Modified with Ultrafine Zinc Oxide Nanoparticles for Enhanced Microwave Absorption Properties.

Currently, electromagnetic radiation and interference have a significant effect on the operation of electronic devices and human health systems. Thus, developing excellent microwave absorbers have a huge significance in the material research field. Herein, a kind of ultrafine zinc oxide (ZnO) nanoparticles (NPs) supported on three-dimensional (3D) ordered mesoporous carbon spheres (ZnO/OMCS) is prepared from silica inverse opal by using phenolic resol precursor as carbon source. The prepared lightweight ZnO/OMCS nanocomposites exhibit 3D ordered carbon sphere array and highly dispersed ultrafine ZnO NPs on the mesoporous cell walls of carbon spheres. ZnO/OMCS-30 shows microwave absorbing ability with a strong absorption (- 39.3 dB at 10.4 GHz with a small thickness of 2 mm) and a broad effective absorption bandwidth (9.1 GHz). The outstanding microwave absorbing ability benefits to the well-dispersed ultrafine ZnO NPs and the 3D ordered mesoporous carbon spheres structure. This work opened up a unique way for developing lightweight and high-efficient carbon-based microwave absorbing materials.

The Effect of Ni Interlayer on the Hot-Rolled and Quenched Stainless Steel Clad Plate.

The vacuum hot-rolled SUS314/Q235 stainless steel clad plate has many drawbacks including serious interface alloy element diffusion, stainless steel cladding's sensitization, and carbon steel substrate's low strength. In this study, the comprehensive properties were systematically adjusted by changing the thickness of the Ni interlayer (0, 100, 200 µm) and the quenching temperature (1000~1150 °C). The results showed that the Ni interlayer can obviously hinder the diffusion of carbon element, so as to achieve the purpose of eliminating the decarburized layer and reducing the carbon content of the carburized layer. Meanwhile, the perfect metallurgical bonding between the substrate and cladding can be obtained, effectively improving the stainless steel clad plate's tensile shear strength and comprehensive mechanical properties, and significantly reduce the brittleness of the carburized layer. As the quenching temperature increases, the grains coarsening of carbon steel and stainless steel became more and more serious, and the sensitization phenomenon and the thickness of the carburized layer are gradually decreased. The stainless steel clad plate (Ni layer thickness of 100 µm) quenched at 1050 °C had the best comprehensive mechanical properties. Herein, the interface shear strength, tensile strength and the fracture elongation reached 360.5 MPa, 867 MPa and 16.10%, respectively, achieving strengthening and toughening aim. This is attributed to the disappearance of the sensitization phenomenon, the grain refinement and the lower interface residual stress.

2D Sandwiched Nano Heterostructures Endow MoSe2 /TiO2- x /Graphene with High Rate and Durability for Sodium Ion Capacitor and Its Solid Electrolyte Interphase Dependent Sodiation/Desodiation Mechanism.

Nano heterostructures relying on their versatile construction and the breadth of combined functionality have shown great potential in energy storage fields. Herein, 2D sandwiched MoSe2 /TiO2- x /graphene nano heterostructures are designed by integrating structural and functional effects of each component, aiming to address the rate capability and cyclic stability of MoSe2 for sodium ion capacitors (SICs). These 2D nano heterostructures based on graphene platform can facilitate the interfacial electron transport, giving rise to fast reaction kinetics. Meanwhile, the 2D open structure induces a large extent of surface capacitive contribution, eventually leading to a high rate capability (415.2 mAh g-1 @ 5 A g-1 ). An ultrathin oxygen deficient TiO2- x layer sandwiched in these nano heterostructures provides a strong chemical-anchoring regarding the products generated during the sodiation/desodiation process, securing the entire cyclic stability. The associated sodiation/desodiation mechanism is revealed by operando and ex situ characterizations, which exhibits a strong solid electrolyte interphase (SEI) dependence. The simulations verify the dependent sodiation products and enhanced heterostructural chemical-anchoring. Assembled SICs based on these nano heterostructures anode exhibit high initial Coulombic efficiency, energy/power densities, and long cycle life, shedding new light on the design of nano heterostructure electrodes for high performance energy storage application.

Three-Dimensional Topotactic Host Structure-Secured Ultrastable VP-CNO Composite Anodes for Long Lifespan Lithium- and Sodium-Ion Capacitors.

Performance degradation of lithium/sodium-ion capacitors (LICs/SICs) mainly originates from anode pulverization, particularly the alloying and conversion types, and has spurred research for alternatives with an insertion mechanism. Three-dimensional (3D) topotactic host materials remain much unexplored compared to two-dimensional (2D) ones (graphite, etc.). Herein, vanadium monophosphide (VP) is designed as a 3D topotactic host anode. Ex situ electrochemical characterizations reveal that there are no phase changes during (de)intercalation, which follows the topotactic intercalation mechanism. Computational simulations also confirm the metallic feature and topotactic structure of VP with a spacious interstitial position for the accommodation of guest species. To boost the electrochemical performance, carbon nano-onions (CNOs) are coupled with 3D VP. Superior specific capacity and rate capability of VP-CNOs vs lithium/sodium can be delivered due to the fast ion diffusion nature. An exceptional capacity retention of above 86% is maintained after 20 000 cycles, benefitting from the topotactic intercalation process. The optimized LICs/SICs exhibit high energy/power densities and an ultrastable lifespan of 20 000 cycles, which outperform most of the state-of-the-art LICs and SICs, demonstrating the potential of VP-CNOs as insertion anodes. This exploration would draw attention with regard to insertion anodes with 3D topotactic host topology and provide new insights into anode selection for LICs/SICs.

Periodic Three-Dimensional Nitrogen-Doped Mesoporous Carbon Spheres Embedded with Co/Co3O4 Nanoparticles toward Microwave Absorption.

Although various bio-inspired materials with outstanding mechanical, acoustic, and optic properties have been developed, bio-inspired materials for microwave absorption applications are rarely reported. Herein, under the inspiration of the opal structure, for the first time, a kind of Co@Co3O4/nitrogen-doped (N-doped) mesoporous carbon sphere (Co@Co3O4/NMCS) with a periodic three-dimensional structure toward microwave absorption application was designed and synthesized. The microwave absorption performance was optimized with respect to the content of Co@Co3O4 nanoparticles. Co@Co3O4/NMCS with ∼20 wt % Co@Co3O4 achieves a reflection loss of -53.8 dB at 5.7 GHz. The simulated radar cross section demonstrated that the Co@Co3O4/NMCS can efficiently suppress the strong electromagnetic scattering from a metal groove structure, which further reveals its excellent absorbing performance. These periodic porous structures of N-doped mesoporous carbon spheres combined with the magnetic Co@Co3O4 nanoparticles contribute to the excellent microwave-absorbing performance.

Triazine-Based Two-Dimensional Organic Polymer for Selective NO2 Sensing with Excellent Performance.

Gas sensors with high sensitivity, fast response/recovery, good selectivity, and room-temperature operation are highly desirable for practical use. However, most of the existing gas sensing materials, either conventional metal oxide semiconductors or advanced inorganic two-dimensional (2D) polymers, can hardly satisfy the above requirements. Herein, we demonstrate an organic 2D polymer derived from a covalent triazine framework (CTF), which possesses nanoscale thickness, intrinsic and periodic pore structures, and abundant functional groups with excellent gas sensing performance. The as-prepared triazine-based 2D polymer (T-2DP) exhibits selective recognition to NO2 with an ultrahigh sensitivity of 452.6 ppm-1, which outperforms most other 2D nanomaterials and its CTF matrix. The sensing effect is superfast (35-47 s) and fully reversible operated at room temperature. The superior comprehensive gas sensing performance of T-2DP and the underlying mechanism was experimentally studied and further discussed by comparison with that of CTF and widely investigated inorganic 2D polymers including graphene and MXene. As a proof of concept, a flexible NO2 chemiresistor based on T-2DP was fabricated to demonstrate its potential for integration into wearable electronics. The scientific findings in this work may propose a new route for the design of high-performance gas sensing materials on the basis of organic 2D polymers in next-generation wearable electronic devices.

A highly flexible and multifunctional strain sensor based on a network-structured MXene/polyurethane mat with ultra-high sensitivity and a broad sensing range.

Flexible and multifunctional strain sensors with superior properties including high sensitivity, low detection limits, and a wide sensing range are always in high demand for wearable electronics. However, it remains a big challenge to fully satisfy the aforementioned requirements. In particular, there is always a trade-off between high sensitivity and wide sensing range. Here, we developed a multifunctional strain sensor based on a network-structured MXene/polyurethane mat (network-M/P mat) and well balanced the relationship between the sensitivity and sensing range by rationally designing the morphology and microstructures of the sensing device. The network-structured polyurethane mat (network-P mat) was fabricated through a facile and scalable electrospinning technique. The highly conductive MXene sheets were decorated onto the network-P mat through hydrogen bonding or electrostatic interactions. The obtained highly flexible and stretchable network-M/P mat exhibited a superior comprehensive sensing performance that was characterized by high sensitivity (gauge factor up to 228), a low limit of detection (0.1%), a large and tunable sensing range (up to 150%), excellent stability (over 3200 cycles), and multiple functions (lateral strain, vertical pressure, bending and subtle vibration). Based on its superior performance, the network-M/P mat-based strain sensor can detect a full range of body actions and subtle physiological signals (e.g. respirations and pulse waves), demonstrating great potential for applications in artificial electronic skin and wearable health detectors.

Bioinspired Pretextured Reduced Graphene Oxide Patterns with Multiscale Topographies for High-Performance Mechanosensors.

Highly sensitive mechanical sensing is vital for the emerging field of skin mimicry and wearable healthcare systems. To date, it remains a big challenge to fabricate mechanosensors with both high sensitivity and a wide sensing range. In nature, slit sensilla are crack-shaped sensory organs of arachnids, which are highly sensitive to tiny external mechanical stimuli. Here, inspired by the geometry of slit sensilla, a concept is developed that pretextures reduced graphene oxide (RGO) nanocoating into multiscale topographies with agminated crumples and interlaced cracks (crumpled & cracked RGO) through an efficient and scalable mechanically driven process. Both the sensitivity and the workable range can be facilely tuned by adjusting the crack density. The resulting mechanosensor exhibits a comprehensive superior performance including high sensitivity (a gauge factor of 205 to 3256), a wide and tunable sensing range (from 0-40 to 0-180%), long-term stability (over 5000 cycles), and multiple sensing functions. Based on its excellent performances, the mechanosensor can be used as a wearable electronic to in situ monitor subtle physiological signals and vigorous body actions. The rationally designed crumpled & cracked RGO provides a promising platform for artificial electronic skin and portable healthcare systems.

Polypyrrole Nanowires with Ordered Large Mesopores: Synthesis, Characterization and Applications in Supercapacitor and Lithium/Sulfur Batteries.

In this work, we report the preparation of polypyrrole nanowires with ordered large mesopores (OMPW) by a simple chemical polymerization method from dual templates synthesized by self-assembling silica nanospheres in porous anodic aluminum oxide (AAO) membrane channels. The obtained OMPW showed a large surface area (231.5 m² g-1), high aspect ratio, and interconnected large mesopores (~23 nm). The OMPW was tested as a supercapacitor electrode and showed a specific capacitance of 453 F g-1 at 0.25 A g-1. A sulfur/OMPW (S/OMPW) cathode was fabricated via a simple solution method and a heat-treatment process for lithium/sulfur batteries (LSBs). The S/OMPW composite delivered a large discharge capacity reaching 1601 mAh g-1 at the initial cycle, retaining 1014 mAh g-1 at the 100th cycle at 0.1 C. The great electrochemical performances of the OMPW capacitor electrode and S/OMPW composite were attributed to the large specific surface areas and interconnected mesopores that could supply more active sites for the electrochemical reaction and facilitate mass transfer.

A porous 3D-RGO@MWCNT hybrid material as Li-S battery cathode.

In this work, a unique three-dimensional (3D) structured carbon-based composite was synthesized. In the composite, multiwalled carbon nanotubes (MWCNT) form a lattice matrix in which porous spherical reduced graphene oxide (RGO) completes the 3D structure. When used in Li-S batteries, the 3D porous lattice matrix not only accommodates a high content of sulfur, but also induces a confinement effect towards polysulfide, and thereby reduces the "shuttle effect". The as-prepared S-3D-RGO@MWCNT composite delivers an initial specific capacity of 1102 mAh·g-1. After 200 charging/discharge cycles, a capacity of 805 mAh·g-1 and a coulombic efficiency of 98% were maintained, implying the shuttle effect was greatly suppressed by the composite matrix. In addition, the S-3D-RGO@MWCNT composite also exhibits an excellent rate capability.

Highly Sensitive, Selective, and Flexible NO2 Chemiresistors Based on Multilevel Structured Three-Dimensional Reduced Graphene Oxide Fiber Scaffold Modified with Aminoanthroquinone Moieties and Ag Nanoparticles.

Highly sensitive, selective, and room-temperature-performing gas sensors have always been the pursuit in the sensing field for practical applications. However, the existing gas sensors can seldom satisfy the aforementioned requirements. Here, we integrate zero-dimensional Ag nanoparticles (AgNPs), one-dimensional polymer fibers, and two-dimensional aminoanthroquinone-functionalized reduced graphene oxide (AQRGO) sheets into a three-dimensional sensing scaffold (AgNP-3D-AQRGO) for high-performance NO2 sensing. The AQ moieties and AgNPs are decorated onto the RGO sheets through a wet chemical route. Electrospinning and self-assembly techniques are employed to assemble the polymer fibers and the functional RGO sheets into a three-dimensional scaffold. The resulting AgNP-3D-AQRGO-based gas sensor can perform at room temperature and exhibits excellent sensing performance for NO2, including an ultrahigh sensitivity (10.3 ppm-1), an ultralow limit of detection (0.6 ppb), and an extremely remarkable selectivity to solely NO2 molecules. Furthermore, the sensor is also highly flexible, demonstrating great potential for portable and real-time monitoring of toxic gas in personal mobile electronics.

A PPy/ZnO functional interlayer to enhance electrochemical performance of lithium/sulfur batteries.

To enhance the electrochemical performance of the lithium/sulfur batteries, a novel interlayer was prepared by coating the slurry of PPy/ZnO composite onto the surface of a separator. Owing to a three-dimensional hierarchical network structure, PPy/ZnO composite serves as a polysulfide diffusion absorbent that can intercept the migrating soluble polysulfides to enhance the electrochemical performance of the Li/S batteries. The specific capacity of the cell with PPy/ZnO interlayer remained at 579 mAh g-1 after 100 cycles at 0.2 C. This interlayer can provide novel avenues for the commercial applications of Li/S batteries.

High-Performance and Multifunctional Skinlike Strain Sensors Based on Graphene/Springlike Mesh Network.

The development of skinlike strain sensors that are integrated with multiple sensing functions has attracted tremendous attention in recent years. To mimic human skin, strain sensors should have the abilities to detect various deformations such as pressing, stretching, bending, and even subtle vibrations. Here, we developed a facile, cost-effective, and scalable method for fabrication of high-performance strain sensors based on a graphene-coated springlike mesh network. This composite-based sensor exhibits an incorporation of low detection limit (LOD) for minute deformation (LOD of 1.38 Pa for pressure, 0.1% for tensile strain, and 10 µm for vibration), multiple sensing functions, long-term stability, and wide maximal sensing range (up to 80 kPa for pressure and 110% for tensile strain). On the basis of its superior performance, it can be applied for in situ monitoring of human motions ranging from subtle physiological signals (e.g., pulse, respiration, and phonation) to substantial movements (e.g., finger bending).

Realization of a half-metallic state on bilayer WSe2 using doping transition metals (Cr, Mn, Fe, Co, Ni) in its interlayer.

The structural, electronic and magnetic properties of Cr, Mn, Fe, Co and Ni-doped bilayer WSe2 are predicted by using first principles calculations. The doped transition-metal (TM) atoms show a covalent-binding with the nearest Se atoms. The calculated electronic structures reveal that the TM Cr, Mn, Fe and Co-doped bilayer WSe2 exhibits a half-metallic character with a 100% spin polarization at the Fermi level, and the reason is ascribed to the strong hybridization peak between the transition metals and the parent W and Se atoms. The Ni-doped bilayer WSe2 is still a semiconductor with nonmagnetism. The Fe-doped system has a robust stability of half-metallicity because there are three connected states peak spanning the Fermi level. The doping of Cr, Mn, Fe and Co atoms leads to a prominent total magnetism (0.93-3.65 [Formula: see text] moment per unit cell), and an induced ∼0.3 [Formula: see text] moment in parent W atoms is found in addition to the main contribution of TM atomic magnetism (0.71-3.33 [Formula: see text] moment per atom). The predicted Cr, Mn, Fe and Co-doped bilayer WSe2 should be the candidate materials for spintronic devices due to their magnetic and half-metallic nature.