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The stannic oxide (SnO2) anode expands in volume during cycling causing a decrease in reversible capacity. In this work, we generated a spherical SnO2/Sn heterojunction with core–shell structure composites encapsulated by graphene (SnO2/Sn/G) in situ using a simple one-step hydrothermal and subsequent annealing process. SnO2/Sn heterojunction nanospheres dispersed in a porous graphene framework accelerate the diffusion kinetics of electrons and ions. In addition, the structure plays a key role in mitigating large volume changes and nanostructure agglomeration. As a result, SnO2/Sn/G exhibits excellent performance as an anode material for lithium-ion batteries (LIBs), maintaining a reversible specific capacity of 720.6 mA h g−1 even after 600 cycles at a current density of 0.5 A g−1. [ABSTRACT FROM AUTHOR]

Engineering heterojunction composite structures consisting of multiple nano active components formed from single element is broadly acknowledged as a robust method to boost the electrochemical performance of lithium-ion batteries (LIBs). Herein, a multidimensional composite structure consisting of SnO/SnO2 heterojunction nanoparticles and reduced graphene oxide nanosheets (SnO/SnO2@G) is proposed. The extensive empirical characterization and density functional theory (DFT) calculations validate the plentiful heterogeneous interfaces and resilient lithium storage mechanism exhibited by the SnO/SnO2 heterostructures. These attributes are closely associated with the rapid diffusion kinetics of Li+ within the space charge region and the presence of multiple-ion channels. On the other hand, the Sn–O–C bond is anchored on graphene sheets, enhancing SnO/SnO2 heterostructure stability and preventing unavoidable aggregation and slow charge transfer. As anticipated, the better specific capacity, rate performance, and cycling stability (498.69 mAh g–1 at 1.0 A g–1 after 400 cycles) are acquired in the LIBs composed of a SnO/SnO2@G anode. This work provides a feasible approach for improving the performance of LIBs by constructing single-element heterostructures. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been widely investigated as an anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity. However, the huge volume expansion and low electrical conductivity limit its practical application to some extent. Here, we prepared silicon/reduced graphene oxide/amorphous carbon (Si/G/C) anode materials for lithium-ion batteries using a facile synergistic cladding layer. The protective effect of different carbon layers was explored and it was found that ternary composites have excellent electrochemical properties. In this work, the surface of Si was first modified using ammonia, and the positively charged Si was tightly anchored to the graphene sheet layer. In contrast, amorphous carbon was used as a reinforcing coating for further coating to synergistically build up the cladding layer of Si NPs with graphene oxide. The ternary composite (Si/G/C) material greatly ensures the structural integrity of the composites and shows excellent cycling as well as rate performance compared to Si/reduced graphene oxide and Si/carbon composites. For the Si/G/C composite, at a current density of 1 A g−1, it can be stably cycled over 267 times with 70% capacity retention (only 0.0711% capacity reduction per cycle). [ABSTRACT FROM AUTHOR]

Using silicon/reduced graphene oxide (Si/rGO) composites as lithium-ion battery (LIB) anodes can effectively buffer the volumetric expansion and shrinkage of Si. Herein, we designed and prepared Si/rGO-b with a sandwiched structure, formed by a duple combination of ammonia-modified silicon (m-Si) nanoparticles (NP) with graphene oxide (GO). In the first composite process of m-Si and GO, a core–shell structure of primal Si/rGO-b (p-Si/rGO-b) was formed. The amino groups on the m-Si surface can not only hybridize with the GO surface to fix the Si particles, but also form covalent chemical bonds with the remaining carboxyl groups of rGO to enhance the stability of the composite. During the electrochemical reaction, the oxygen on the m-Si surface reacts with lithium ions (Li+) to form Li2O, which is a component of the solid–electrolyte interphase (SEI) and is beneficial to buffering the volume expansion of Si. Then, the p-Si/rGO-b recombines with GO again to finally form a sandwiched structure of Si/rGO-b. Covalent chemical bonds are formed between the rGO layers to tightly fix the p-Si/rGO-b, and the conductive network formed by the reintroduced rGO improves the conductivity of the Si/rGO-b composite. When used as an electrode, the Si/rGO-b composite exhibits excellent cycling performance (operated stably for more than 800 cycles at a high-capacity retention rate of 82.4%) and a superior rate capability (300 mA h/g at 5 A/g). After cycling, tiny cracks formed in some areas of the electrode surface, with an expansion rate of only 27.4%. The duple combination of rGO and the unique sandwiched structure presented here demonstrate great effectiveness in improving the electrochemical performance of alloy-type anodes. [ABSTRACT FROM AUTHOR]

Recently, it has become imperative to develop high energy density as well as high safety lithium‐ion batteries (LIBS) to meet the growing energy demand. Among the anode materials used in LIBs, the currently used commercial graphite has low capacity and is a safety hazard due to the formation of lithium dendrites during the reaction. Among the transition metal oxide (TMO) anode materials, TMO based on the intercalation reaction mechanism has a more stable structure and is less prone to volume expansion than TMO based on the conversion reaction mechanism, especially the niobium‐based oxide in it has attracted much attention. Niobium‐based oxides have a high operating potential to inhibit the formation of lithium dendrites and lithium deposits to ensure safety, and have stable and fast lithium ion transport channels with excellent multiplicative performance. This review summarizes the recent developments of niobium‐based oxides as anode materials for lithium‐ion batteries, discusses the special structure and electrochemical reaction mechanism of the materials, the synthesis methods and morphology of nanostructures, deficiencies and improvement strategies, and looks into the future developments and challenges of niobium‐based oxide anode materials. [ABSTRACT FROM AUTHOR]

Nanostructured silicon anodes have shown extraordinary lithium storage properties for lithium-ion batteries (LIBs) but are usually achieved at low areal loadings (< 1.5 mg·cm−2) with low areal capacity. Sustaining sound electrochemical performance at high loading requires proportionally higher ion/electron currents and robust structural stability in the thicker electrode. Herein, we report a three-dimensional (3D) printed silicon-graphene-carbon nanotube (3D-Si/G/C) electrode for simultaneously achieving ultrahigh areal/gravimetric capacities at high mass loading. The periodically arranged vertical channels and hierarchically porous filaments facilitate sufficient electrolyte infiltration and rapid ion diffusion, and the carbonaceous network provides excellent electron transport properties and mechanical integrity, thus endowing the printed 3D-Si/G/C electrode with fast electrochemical reaction kinetics and reversibility at high mass loading. Consequently, the 3D-Si/G/C with high areal mass loading of 12.9 mg·cm−2 exhibits excellent areal capacity of 12.8 mAh·cm−2 and specific capacity of 1007 mAh·g−1, respectively. In-situ optical microscope and ex-situ scanning electron microscope (SEM) confirm that the hierarchically porous filaments with interconnected carbon skeletons effectively suppress the volume change of silicon and maintain stable micro-lattice architecture. A 3D printed 3D-Si/G/C-1∥3D-LiFePO4/G full cell holds excellent cyclic stability (capacity retention rate of 78% after 50 cycles) with an initial Coulombic efficiency (ICE) of 96%. This work validates the feasibility of 3D printing on constructing high mass loading silicon anode for practical high energy-density LIBs. [ABSTRACT FROM AUTHOR]

Currently, it remains a challenge to make comprehensive improvements to overcome the disadvantages of volume expansion, Li2O irreversibility and low conductivity of SnO2. Heterostructure construction has been investigated as an effective strategy to promote electron transfer and surface reaction kinetics, leading to high electrochemical performance. Herein, NiO/SnO2 heterojunction modified nitrogen doped graphene (NiO/SnO2@NG) anode materials were prepared using hydrothermal and carbonization techniques. Based on the excellent structural advantages, sufficiently small NiO/SnO2 heterojunction nanoparticles increase the interfacial density to promote Li2O decomposition, and the built-in electric field accelerates the charge transport rate to improve the conductivity. The three-dimensional porous graphene framework effectively mitigates volume expansion during cycling and stabilizes the reactive interface of electrode materials. The results show that the NiO/SnO2@NG mixture has high reversible specific capacity (938.8 mA h g−1 after 450 cycles at 0.1 A g−1), superior multiplicity performance (374.5 mA h g−1 at 3.0 A g−1) and long cycle life (685.3 mA h g−1 after 1000 cycles at 0.5 A g−1). Thus, this design of introducing NiO to form heterostructures with SnO2 is directly related to enhancing the electrochemical performance of lithium-ion batteries (LIBs). [ABSTRACT FROM AUTHOR]

With the rapid development of electronic equipment and communication technology, radiation pollution caused by electromagnetic waves has become a serious social nuisance. Based on this, the development of high-performance electromagnetic wave-absorbing materials has become a research hotspot. Among them, Fe3O4, as a traditional ferrite-based wave-absorbing material, has the advantages of abundant natural resources, low environmental pollution, and deep wave-absorbing strength. Therefore, the direct utilization of Fe3O4 as a wave-absorbing material or as a raw material for the preparation of wave-absorbing materials has become a research direction for researchers. This paper first introduces the basic theories and evaluation parameters related to wave absorption and then reviews the research progress of pure Fe3O4 wave-absorbing materials with key structural dimensions below 500 nm and related composite wave-absorbing materials by summarizing the reports of electromagnetic wave-absorbing materials related to Fe3O4 in recent years. Finally, the development prospect of Fe3O4-based wave-absorbing materials is introduced. [ABSTRACT FROM AUTHOR]

The bacterial microenvironment-activated nanocatalytic antibacterial strategy has attracted extensive attention owing to the high specificity to eliminate pathogens, which provides opportunities to solve antibiotic resistance. However, the relatively high pH value and insufficient endogenous H2O2 level in bacterial microenvironment limits the efficiency of Fenton reactions induced by these nanocatalytic agents, leading to unsatisfied antibacterial performance. Herein, bimetallic peroxide was first reported as a high-efficiency antibacterial nanocatalyst with high pH-activated, H2O2 self-supply and synergistic effect-enhanced cascade Fenton chemistry. An isolated spray vial was further developed to achieve in situ gelation at the wound site, adapt to irregular wound surface, and maintain long-term release of nanocatalyst. As a result, wound healing was efficiently promoted corresponding to excellent nanocatalytic antibacterial efficacy. Thus, our in situ sprayed nanocatalytic antibacterial gel provides a promising paradigm for high-efficiency bacterial infection therapy. [ABSTRACT FROM AUTHOR]

Metal-based nanozymes with exceptional physicochemical property and intrinsic enzymatic properties have been widely used in industrial, medical, and diagnostic fields. However, low substrate affinity results in unsatisfying catalytic kinetic and instability in complicated conditions, which significantly decreases their sensitivity and reliability. Herein, an amorphous hollow manganese silicate nanosphere (defined as AHMS) has been successfully synthesized via a facile one-step hydrothermal method and utilized in the archetype for colorimetric detection of biothiols with high sensitivity and high reliability. The experimental data demonstrates that ultrafast affinity of the substrate contributes to enhanced sensitivity with outstanding catalytic kinetic features (Km = 27.1 μM) and low limit of detection (LODGSH = 20 nM). The designed sensor demonstrates a reliable applicability for analysis of biological liquids (fetal calf serum and Staphylococcus aureus) and design of visual logic gates. Therefore, AHMS provides a promising strategy for ultrasensitive and high-reliable biosensing. [ABSTRACT FROM AUTHOR]

Following the growth of infotech and electronic industries, electromagnetic-wave-absorbing materials play an essential role in the traction of the need for high-precision weaponry and intelligent electronic equipment. The exploitation of high-performance electromagnetic-wave-absorbing materials has emerged as a strategic challenge to be solved in the upgrading of military equipment and civil electromagnetic security. The more maturely studied absorbing materials (carbon, ferrite, etc.) have a single loss mechanism and poor resistance matching, which are already not enough to cover the basic needs. To explore absorbing materials that satisfy both impedance matching and attenuation balance, dielectric nanomaterials have come to the fore. They can realize light weight, thin layer, broad band, and multiband, which have great application prospects. In this review, we start with a summary of typical dielectric loss mechanisms (interfacial polarization, dipole polarization, and conduction loss). Next, diverse carbides, oxides, sulfides, and their composites with dielectric or magnetic materials are described, and the nanostructure advantages and wave-absorbing performance advantages are investigated. Then, the applications of wave-absorbing materials are depicted. Lastly, the challenges faced by dielectric-type materials are outlined, and future development trends are foreseen. Overall, this review offers an overview of the advances in the study of dielectric nanoabsorbing materials. [ABSTRACT FROM AUTHOR]

Diboride‐based ultra‐high temperature ceramics (UHTCs) are a special class of ceramics with excellent comprehensive properties, which have extensive potential applications in extreme environments. However, their practical applications are limited, mainly due to the poor fracture toughness and thermal shock resistance. Refractory metals have high melting points, good ductility, and high toughness, which have huge potential to improve the properties of diboride‐based ceramics. As a special class of additives, they have been adopted to promote densification, improve microstructure, and properties. However, diboride‐based ceramics containing refractory metals have not received adequate attention due to relatively weak practical effects on property improvement. The present review highlights the progress and existing problems of transition metal diborides with refractory metal additives, including W, Ta, Mo, Nb, Hf, V, Cr, and Zr, focusing mainly on the microstructure change and property improvements, followed by challenges and possible future development strategies. [ABSTRACT FROM AUTHOR]

Research into electromagnetic radiation enhancement and frequency band broadening is growing in popularity with the advance of 5G connected communication technology. As such, there is an urgent need for wave-absorbing materials that meet both the broadband and strong absorption requirements. Dielectric materials, as a class of lightweight materials with controllable morphology, are one of the many candidates, but their inherent properties make it tough to simultaneously match impedance and strong attenuation, so they cannot meet both broadband and strong absorption requirements. Here, we compensate for the intrinsic properties of dielectric materials by means of shape modulation, which can achieve a win–win situation of impedance and attenuation. When the response time is 8 h, the material studied achieves robust absorption (reflection loss value reaches −45.6 dB) and a wide frequency band (6.08 GHz) at 2.6 mm. Given that the material has a multi-vacancy embroidered spherical structure, it allows multiple reflections of electromagnetic waves and improves the conductive loss. Also, the nanosheet cross-stacking builds multiple interfaces, and the resulting interfacial polarization becomes the most important part of the dielectric loss. Meanwhile, it can be further demonstrated by simulation and radar scattering area solution that the interfacial polarization constructed from the embroidery spherical structure leads to exceptional wave absorption performance. This work suggests a concept for the preparation of practical absorbing materials with strong absorption, a wide frequency band and multiple interfaces. [ABSTRACT FROM AUTHOR]

Monolithic carbon electrodes with robust mechanical integrity and porous architecture are highly desired for capacitive deionization but remain challenging. Owing to the excellent mechanical strength and electroconductivity, commercial carbon fibers cloth demonstrates great potential as high‐performance electrodes for ions storage. Despite this, its direct application on capacitive deionization is rarely reported in terms of limited pore structure and natural hydrophobicity. Herein, a powerful metal‐organic framework‐engaged structural regulation strategy is developed to boost the desalination properties of carbon fibers. The obtained porous carbon fibers features hierarchical porous structure and hydrophilic surface providing abundant ions‐accessible sites, and continuous graphitized carbon core ensuring rapid electrons transport. The catalytic‐etching mechanism involving oxidation of Co and subsequent carbonthermal reduction is proposed and highly relies on annealing temperature and holding time. When directly evaluated as a current collector‐free capacitive deionization electrode, the porous carbon fibers demonstrates much superior desalination capability than pristine carbon fibers, and remarkable cyclic stability up to 20 h with negligible degeneration. Particularly, the PCF‐1000 showcases the highest areal salt adsorption capacity of 0.037 mg cm−2 among carbon microfibers. Moreover, monolithic porous carbon fibers‐carbon nanotubes with increased active sites and good structural integrity by in‐situ growth of carbon nanotubes are further fabricated to enhance the desalination performance (0.051 mg cm−2). This work demonstrates the great potential of carbon fibers in constructing high‐efficient and robust monolithic electrode for capacitive deionization. [ABSTRACT FROM AUTHOR]

Three-dimensional carbon-based materials have attracted much attention for electromagnetic wave absorption because low-dimensional materials have failed to meet the needs of constructing effective networks with ultra-light properties due to their easy agglomeration and in-plane stacking. The 3D element of quadrangular cone carbon was innovatively applied in this work to construct interconnected networks (MFC). This material successfully overcomes the disadvantages of easy agglomeration and in-plane stacking in low-dimensional elements, allowing for more efficient construction of absorbing networks. The prepared MFC exhibits excellent EAB (6.70 GHz) and RL (−50.92 dB), especially at an ultra-low filling ratio (1.04 wt%). Such superior performance can be attributed to the MFC effective network constructed by quadrangular cone carbon facilitating the entrance and diffuse scattering of electromagnetic waves. This study may provide new inspiration for constructing an effective absorbing network of pure carbon with 3D elements (quadrangular cone carbon), realizing ultra-low filling and broadband microwave performance. [ABSTRACT FROM AUTHOR]

Inspired by the pomegranate natural artful structure, pomegranate micro/nano hierarchical plasma configuration of Fe/Fe3C@graphitized carbon (FFC/pCL) was constructed based on the green sol-gel method and in-situ chemical vapor deposition (CVD) synthesis protocol. Pomegranate-like FFC/pCL successfully overcame the agglomeration phenomenon of magnetic nanoparticles with each seed of the pomegranate consisting of Fe/Fe3C as cores and graphitized carbon layers as shells. The high-density arrangement of magnetic nanoparticles and the design of pomegranate-like heterostructures lead to enhanced plasmon resonance. Thus, the pomegranate-like FFC/pCL achieved a great electromagnetic wave (EMW) absorbing performance of 6.12 GHz wide band absorption at a low mass adding of only 16.7 wt.%. Such excellent EMW performance can be attributed to its unique pomegranate hierarchical plasma configuration with separated nanoscale iron cores, surface porous texture, and good carbon conductive network. This investigation provides a new paradigm for the development of magnetic/carbon based EMW absorbing materials by taking advantage of pomegranate hierarchical plasma configuration. [ABSTRACT FROM AUTHOR]

Two-phase heterostructures have received tremendous attention in energy-related fields as high-performance electrode materials. However, heterogeneous interfaces are usually constructed by introducing foreign elements, which disturbs the investigation of the intrinsic effect of the two-phase heterostructure. Herein, unique heterostructures constructed with orthorhombic NiSe2 and cubic NiSe2 phases are developed, which are embedded in in situ formed porous carbon from metal–organic frameworks (MOFs) (O/C-NiSe2@C). Precisely-controlled selenylation of MOFs is crucial for the formation of the O/C-NiSe2 heterostructure. The heterogeneous interfaces with lattice dislocations and charge distribution are conducive to the high-speed transfer of electrons and ions during electrochemical processes, so as to improve the electrochemical reaction kinetics for lithium-ion storage and the hydrogen evolution reaction (HER). When used as the anode of lithium-ion batteries (LIBs), O/C-NiSe2@C shows a superior electrochemical performance to the counterparts with only the cubic phase (C-NiSe2@C), in view of the cycling performance (719.3 mA h g−1 at 0.1 A g−1 for 100 cycles; 456.3 mA h g−1 at 1 A g−1 for 1000 cycles) and rate capabilities (344.8 mA h g−1 at 4 A g−1). Furthermore, O/C-NiSe2@C also exhibits better HER properties than C-NiSe2@C, that is, much lower overpotentials of 154 mV and 205 mV in 0.5 M H2SO4 and 1 M KOH, respectively, at 10 mA cm−2, a smaller Tafel slope as well as stable electrocatalytic activities for 2000 cycles/10 h. Preliminary observations indicate that the unique orthorhombic/cubic two-phase heterostructure could significantly improve the electrochemical performance of NiSe2 without additional modifications such as doping, suggesting the O/C-NiSe2 heterostructure as a promising bifunctional electrode for energy conversion and storage applications. [ABSTRACT FROM AUTHOR]

Wave-transparent lithium aluminosilicate glass-ceramic (LAS) nanofillers are confirmed to be effective in regulating the electromagnetic parameters to satisfy the impedance matching characteristic and enhance the electromagnetic wave loss ability. Herein, a new pitaya slice hierarchical configuration of a 2D LAS/carbon sheet electromagnetic wave absorber was prepared by an effective protocol using an ammonium nitrate-assisted self-polymerization and in situ blown strategy. The obtained 2D pitaya hierarchical configuration exhibited excellent microwave absorption performance with an RL of −55.26 dB and a wide effective absorption bandwidth (≤-10 dB) of 8.21 GHz, covering the whole Ku-band (12–18 GHz) with a low mass adding of only 9.2 wt%. The absorbing mechanism demonstrated that the interfacial polarization, Debye dipolar relaxation, and well-matched characteristic impedance play important roles in improving the microwave absorption properties of the 2D pitaya slice hierarchical configuration. This paper may provide a new route for constructing an effective absorbing network of 2D pitaya slice hierarchical configuration, realizing ultra-low filling and broadband microwave performance. [ABSTRACT FROM AUTHOR]

Based on the dissolution‐precipitation mechanism, this article successfully synthesized binary and ternary transition metal carbide microcuboids with random combinations of Hf, Nb, and Ta by annealing monocarbides/cobalt powders. Accelerated mass transport rate through the flow of molten alloys (Co‐Hf‐Nb‐Ta) instead of slow solid diffusion made the low‐temperature pressureless sintering technique (1500°C) a reality. Furthermore, the equilibrium morphology was driven by the gradient Gibbs potential of carbides induced by the different local curvature of powders and anisotropic interfacial energy. (Hf0.5Ta0.5)C possessed the optimal oxidation resistance among all mentioned carbides, even competed with (Hf1/3Nb1/3Ta1/3)C. During the isothermal oxidation at 800∼1200°C, the doping of Nb and Ta in carbides assisted the monoclinic‐orthorhombic HfO2 transition at ambient pressure, besides, TaC can also restrain the orthorhombic‐monoclinic transition of Nb2O5. Moreover, oxidation kinetics parameters concluded that the addition of HfC and TaC contributed to the decreasing reaction order and the increasing activation energy, respectively. [ABSTRACT FROM AUTHOR]

Cf/C-SiC composites have become the preferred material for high-temperature load-bearing applications because of their low density, high strength, and excellent thermal-physical properties. Due to the composite's poor sintering performance, the sintering temperature and pressure required for the preparation of Cf/C-SiC by traditional methods are also relatively high, which limits its engineering application. Herein, based on the precursor-derived ceramic route and C/C composites material preparation process, a binary binder (coal pitch and polysilylacetylene) is developed, which combines a carbon source, SiC precursor, and semi-ceramic SiC filler organically. Then, the SiC phase was successfully introduced into C/C composites by the slurry impregnation-hot pressing sintering method. The prepared Cf/C-SiC composites showed good mechanical properties, with a density of 1.53 g/cm3 and a bending strength of 339 ± 21 MPa. Moreover, the effects of the binary binder on the microstructure, density, and mechanical properties of Cf/C-SiC composites were investigated. This work provides a novel and effective approach to fabricating Cf/C-SiC composites with low density and high strength. [ABSTRACT FROM AUTHOR]

Dense Sialon fibers/barium aluminosilicate (BAS) matrix self‐reinforced composite was synthesized by one‐step method without applying pressure before or during sintering process. In this work, BAS matrix and internal Sialon fibers were synthesized successfully by directly sintering precursor powders at 1400°C for 4 h. The BAS is not only introduced as a structural matrix material, but also as an effective liquid phase sintering aid to attain full densification bulk sample. The results show that the diameter of fibers is about 100–200 nm, and the quantity of the fibers can be changed with different temperatures. The obtained Sialon fibers/BAS matrix composites exhibit better toughness due to fiber bridging, crack deflection, and pullout. The sample with 3.5 wt% carbon content has maximum value of flexural strength (74.5 ± 3.5 MPa) and fracture toughness (3.2 ± 0.20 MPa·m1/2). The growth of the Sialon fibers follows a vapor‐liquid‐solid (V‐L‐S) mechanism. These findings featured with a green and simple preparation process provide a facile strategy to design and fabricate the bulk ceramic matrix composites in complex shapes and different sizes. [ABSTRACT FROM AUTHOR]

The crystallization phenomenon of fused silica ceramics in use has received much attention. In this paper, XRD, SEM, FT-IR and XPS were used to stud)' the effects of phase structure, surface morphology and chemical bond on the crystallization behavior of SiBON ceramics. The results show that the precipitation of cristobalite can be effectively inhibited by sintering SiBON ceramics at 1 550°Ct under the protection of nitrogen. In contrast, the crystallization inhibition effect of samples sintered at the same temperature in vacuum atmosphere is not significant. The phase composition of SiBON ceramics is amorphous SiBON, Si3N4, and BN. The mechanism of suppressing crystallization of SiBON ceramics is that the doping of B and N elements converts the Si--0--Si bonds in SiO2 into B--0--Si and Si--0--N bonds, and the resulting Si--B--0--N amorphous structure improves the SiO2 crystallization activation energy. [ABSTRACT FROM AUTHOR]

Carbon-based materials are the most widely used electromagnetic wave absorbing (EWA) material in the aerospace field because of their light weight. However, carbon materials suffer from poor impedance matching, which hinders their practical applications. Here, inspired by the dredging strategy from Chinese historical allusion "King Yu Tamed the Flood", a sugar blower synthesis protocol is proposed to guide and transmit electromagnetic wave, and then dissipate them step by step. Porous micro pipeline carbon (PMPC) and sugar blower synthesis protocol are purposely designed and put into practice. The achieved superior EWA performance of PMPC verified the effectiveness of the dredging strategy. Moreover, the key factors of the PMPC are revealed to be the special pore configuration (surface holes and the internal drainage channels). By systematically analyzing, it can be concluded that the sugar blower synthesis protocol can simply and effectively improve the impedance mismatching problem of pure carbon materials, and thus provide a new pathway for the development of ultralight and ultrastrong EWA materials. Moreover, given the unique pore configuration and transport characteristics, PMPC will have wide application prospects in the fields of renewable energy, stealth technique, heat insulation and gas-phase or liquid-phase reactors. Noteworthily, the newly developed sugar blower synthesis protocol for PMPC is simple, efficient, pore structure controllable and industrialized, providing a paradigm shift for some other porous pipeline architectures. [ABSTRACT FROM AUTHOR]

Tricobalt tetroxide (Co3O4) is one of the promising anodes for lithium-ion batteries (LIBs) due to its high theoretical capacity. However, the poor electrical conductivity and the rapid capacity decay hamper its practical application. In this work, we design and fabricate a hierarchical Co3O4 nanorods/N-doped graphene (Co3O4/NG) material by a facile hydrothermal method. The nitrogen-doped graphene layers could buffer the volume change of Co3O4 nanorods during the delithium/lithium process, increase the electrical conductivity, and profit the diffusion of ions. As an anode, the Co3O4/NG material reveals high specific capacities of 1873.8 mA·h·g−1 after 120 cycles at 0.1 A·g−1 as well as 1299.5 mA·h·g−1 after 400 cycles at 0.5 A·g−1. Such superior electrochemical performances indicate that this work may provide an effective method for the design and synthesis of other metal oxide/N-doped graphene electrode materials. [ABSTRACT FROM AUTHOR]

High conductivity two-dimensional (2D) materials have been proved to be potential electrode materials for flexible supercapacitors because of its outstanding chemical and physical properties. However, electrodes based on 2D materials always suffer from limited electrolyte-accessible surface due to the restacking of the 2D sheets, hindering the full utilization of their surface area. In this regard, an electrolyte-mediated method is used to integrate dense structure reduced graphene oxide/MXene (RGM)-electrolyte composite films. In such composite films, reduced graphene oxide (RGO) and MXene sheets are controllable assembly in compact layered structure with electrolyte filled between the layers. The electrolyte layer between RGO and MXene sheets forms continuous ion transport channels in the composite films. Therefore, the RGM-electrolyte composite films can be used directly as self-supporting electrodes for supercapacitors without additional conductive agents and binders. As a result, the composite films demonstrate enhanced volumetric specific capacity, improved volumetric energy density and higher power density compared with both pure RGO electrode and porous composite electrode prepared by traditional methods. Specifically, when the mass ratio of MXene is 30%, the electrode delivers a volumetric specific capacity of 454.9 F·cm−3 with a high energy density of 39.4 Wh·L−1. More importantly, supercapacitors based on the composite films exhibit good flexibility electrochemical performance. The investigation provides a new approach to synthesize dense structure films based on 2D materials for application in high volumetric capacitance flexible supercapacitors. [ABSTRACT FROM AUTHOR]

Carbon fibers reinforced lithium aluminosilicate matrix composites (Cf/LAS) were prepared by slurry infiltration combined with a hot press procedure. The friction, wear behavior, and wear mechanisms of Cf/LAS composites under dry sliding conditions were investigated. The results show that the coefficient of friction (COF) initially increased with the increase in carbon fiber content, and reached the maximum value of 0.20 for the 33%Cf/LAS composite. The COF increased sharply with increasing sample temperature from RT to 300 °C. The COF remained stable in the temperature range of 300–500 °C. The two wear mechanisms of LAS glassceramics are fatigue wear and abrasive wear. The Cf/LAS composites demonstrate slight spalling and shallow scratches. These results show that carbon fibers improve the mechanical properties and wear resistance of Cf/LAS composites. [ABSTRACT FROM AUTHOR]

Novel SiC‐based nanomaterials, namely the nitrogen and aluminum co‐doped SiC@SiO2 core‐shell nanowires and nitrogen‐doped SiO2/Al2O3 nanoparticles, have been fabricated through a facile thermal treatment process based on the chemical vapor deposition and vapor‐liquid reaction. These nanomaterials show remarkable hydrophobicity with a water contact angle (CA) over 140°, which are aroused by the surface zigzag morphology of the nanostructures and the hydrocarbyl groups generated during the preparation process. Moreover the nanocomposites also exhibit relatively prominent microwave absorption (MA) properties in the frequency range of 2.0‐18.0 GHz. The minimum reflection loss (RL) value as low as −23.68 dB can be observed at 14.16 GHz when the absorber thickness is 2.6 mm with a loading rate of 16.7 wt%. And the nanocomposites‐based absorbent can achieve an effective absorption bandwidth (RL < −10 dB) of 4.48 GHz with the absorbent thickness of 2.5 mm. This enhanced microwave attenuation performance can be attributed to multiple polarizations and perfect impedance matching conditions, as well as multiple internal reflections. These marvelous properties make these N and Al co‐doped SiC@SiO2 core‐shell nanowires and N‐doped SiO2/Al2O3 nanoparticles display extensive application potential as MA materials in harsh environment. [ABSTRACT FROM AUTHOR]

3D porous oxygen-enriched graphene hydrogels (POGHs) have been successfully prepared via a one-step hydrothermal approach with graphene oxide and a tiny amount of acidic glutamic acid which serves as carboxyl source, reductant, nitrogen dopant, as well as pore size and density regulator at the same time. Owing to the high content of oxygen-containing functional groups and high density, the repaired graphene sheet structure by nitrogen doping, 3D interconnected porous networks and large specific surface areas, the as-obtained POGHs binder-free electrodes exhibit excellent electrochemical properties in 6 M KOH electrolyte. In particular, the POGH-30-based symmetric supercapacitor displays well-balanced volumetric capacitance (241.1 F cm−3) and gravimetric capacitance (256.5 F g−1) at 0.5 A g−1, and this capacitance can be maintained for 91.8% even at 10 A g−1. Moreover, the POGH-30 electrode also delivers high gravimetric and volumetric specific energy densities of 8.8 Wh kg−1 and 8.3 Wh L−1 at 0.5 A g−1, and excellent cycling stability of 100.7% retention after 10000 cycles at 10 A g−1. These results denote that POGH-30 is expected to be used as electrode material for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

With up to fivefold higher in energy density vs. lithium-ion battery, lithium-sulfur (Li-S) battery is a compelling energy storage system, complemented by a very low cost of sulfur. However, current Li-S cells face the capacity decay caused by the dissolution of lithium polysulfides. In this work, a new material concept, namely the “layer @ adsorbent” is introduced to address the capacity fading problem. This architecture utilizes mesoporous SiO2 holding sulfur and polysulfides and the whole S fused SiO2 was intimately encapsulated by reduced graphene oxide (RGO). Benefiting from the enhanced capillary force from SiO2, as well as the improved conductivity from RGO chamber, this “layer @ adsorbent” architecture could easily spread and adsorb polysulfides. The initial discharge capacity is approaching its theoretical capacity (1567 mAh g−1 at 0.1 C). A stable cycle performance over 500 cycles is demonstrated with the capacity loss of merely about 0.05% per cycle. Additionally, the cathode with higher sulfur content (67%) delivers a stable reversible capacity (400 mAh g−1) over 500 cycles at higher current of 2 C.ᅟ [ABSTRACT FROM AUTHOR]

Abstract: Li1.2Ni0.133Co0.133Mn0.534O2/graphene composites are prepared with Li1.2Ni0.133Co0.133Mn0.534O2 particles and graphene oxide sol by a novel ethanol solution reduction method and an ethanol solvothermal method. The structure and morphology are characterized by X-ray diffraction, Raman spectra, scanning electron microscope, and transmission electron microscopy methods. It is found that the Li1.2Ni0.133Co0.133Mn0.534O2 spherical secondary particles are wrapped with a graphene network. A four-probe powder conductivity measure test shows that the electrical conductivity of the materials with graphene-wrapped is significantly improved, which is further proved by the electrochemical impedance spectroscopy and ohmic polarization. In addition, the graphene network coating structure can reduce the direct contact between electrolyte and electrode active material as a physical protection. Therefore, the electrochemical properties of the two composites obtained by the two methods are all improved. By comparison, the coating effect with ethanol solution reduction method is much better than that of with ethanol solvothermal method. The composite prepared by ethanol solution reduction method can deliver an average discharge capacity of 315.1 mAh g−1 at 0.05C and 281.4 mAh g−1 at 0.1C, which is about 40 mAh g−1 higher than that of the original material. It can deliver a capacity retention of 83.9% after 200 cycles, which is increased ~ 17% compared with that of the original material. Moreover, its discharge voltage platform and rate capability are greatly increased.Graphical abstract: [ABSTRACT FROM AUTHOR]

Partially reduced and nitrogen-doped graphene oxides (PRNGs) were prepared through a one-step hydrothermal method with graphene oxide as raw material and phenylethylamine as reducing-doping agents. Benefiting from nitrogen- and oxygen-containing functional groups, interconnected 3D porous networks and high specific surface area, the as-prepared samples demonstrate good electrochemical performances. Particularly, the PRNG-10 electrodes in the wet state show an enhanced gravimetric and volumetric specific capacitance (264.1 F g−1 and 211.3 F cm−3), good rate capability and excellent cycle stability (101.85% of the initial capacitance after 10000 cycles) in 6 M KOH electrolyte. [ABSTRACT FROM AUTHOR]

Tunable electromagnetic properties and excellent thermo-stability are important criteria while choosing absorbers. Here, carbon-coated Fe3Si nanoparticles in amorphous SiCO ceramics (SiCO/C/Fe3Si) were successfully obtained via polymer-derived ceramics (PDC) from ferric acetylacetonate modified-polysilylacetylene (PSA). By adjusting the magnetic components, the structure of the absorbers could be tuned and their bandwidth varied. The absorbers with a hybrid composition (4.35 wt% Fe) possessed a minimal reflection loss (RL) of −32 dB at 9.2 GHz with a thickness of 3.5 mm and an effective bandwidth (RL ＜ −10 dB) of about 3.6 GHz. The absorbers (12.33 wt% Fe) were enhanced and the minimal RL value was close to −41 dB at 7.9 GHz with a thickness of 3.5 mm. Simultaneously, a broad bandwidth (RL ＜ −5 dB) appeared and covered nearly the whole S-band (2–3.95 GHz) where the RL value reached −10 dB at 2 GHz. After the second thermal treatment under 1000 °C, the minimal RL value of the absorbers (12.33 wt% Fe) remained at −33 dB at 6.6 GHz with a thickness of 4 mm, while the effective bandwidth was 3.4 GHz with a thickness of 3 mm. In addition, the formation mechanism of carbon-coated Fe3Si, which possibly resulted from the mesophase SiCFe alloy was also discussed. The as-prepared SiCO/C/Fe3Si hybrid exhibits outstanding wave absorption ability and present a huge potential for the application at high temperatures. [ABSTRACT FROM AUTHOR]

Carbonaceous materials, one of the most important electrode materials for sea water desalination, have attracted tremendous attention. Herein, we develop a facile and effective two-step strategy to fabricate hierarchical porous carbon nanotubes/graphene/carbon nanofibers (CNTs/G/CNFs) composites for capacitive desalination application. Graphite oxide (GO), Ni2+, and Co2+ are introduced into polyacrylonitrile (PAN) nanofibers by electrospinning method. During the annealing process, the PAN nanofibers are carbonized into CNFs felt, while the CNTs grow in situ on the surface of CNFs and graphite oxide are reduced into graphene simultaneously. Benefiting from the unique hierarchical porous structure, the as-prepared CNTs/G/CNFs composites have a large specific surface area of 223.9 m2 g−1 and excellent electrical conductivity. The maximum salt capacity of the composites can reach to 36.0 mg g−1, and the adsorbing capability maintains a large retention of 96.9% after five cycles. Moreover, the effective deionization time of the CNTs/G/CNFs composites lasts more than 30 min, much better than the commercial carbon fibers (C-CFs) and graphene/carbon nanofibers (G/CNFs) composites. Results suggest that the designed hierarchical porous CNTs/G/CNFs architecture could enhance the capacitive desalination properties of electrode materials. And the possible adsorption mechanism of the novel electrode materials is proposed as well. [ABSTRACT FROM AUTHOR]

Abstract: Transition metal carbonates (TMCs) with complex composition and robust hybrid structure hold great potential as high‐performance electrode materials for lithium‐ion batteries (LIBs). However, poor ionic/electronic conductivities and large volume changes of TMCs during lithiation/delithiation processes have hindered their applications. Herein, single‐phase MnCo mixed carbonate composites encapsulated by reduced graphene oxide (MnxCo1−xCO3/RGO), in which Mn and Co species are distributed randomly in one crystal structure, are successfully synthesized through a facial liquid‐state method. When evaluated as LIB anodes, the MnxCo1−xCO3/RGO composites exhibit enhanced electrochemical performance compared with the reference CoCO3/RGO and MnCO3/RGO. Specifically, the Mn0.7Co0.3CO3/RGO delivers an ultrahigh capacity of 1454 mA h g−1 after 130 cycles at 100 mA g−1 and exhibits an ultralong cycling stability (901 mA h g−1 after 1500 cycles at 2000 mA g−1). This is the best lithium storage performance among carbonate‐based anodes reported up to date. Such superb performance is attributed to the hybrid structure and enhanced electroconductivity due to the integration of Co and Mn into one crystal structure, which is complemented by electrochemical impedance spectroscopy and density functional theory calculations. The facile synthesis, promising electrochemical results, and scientific understanding of the MnxCo1−xCO3/RGO provides a design principle and encourages more research on TMCs‐based electrodes. [ABSTRACT FROM AUTHOR]

Abstract: Transition metal carbonates (TMCs) with complex composition and robust hybrid structure hold great potential as high‐performance electrode materials for lithium‐ion batteries (LIBs). However, poor ionic/electronic conductivities and large volume changes of TMCs during lithiation/delithiation processes have hindered their applications. Herein, single‐phase MnCo mixed carbonate composites encapsulated by reduced graphene oxide (MnxCo1−xCO3/RGO), in which Mn and Co species are distributed randomly in one crystal structure, are successfully synthesized through a facial liquid‐state method. When evaluated as LIB anodes, the MnxCo1−xCO3/RGO composites exhibit enhanced electrochemical performance compared with the reference CoCO3/RGO and MnCO3/RGO. Specifically, the Mn0.7Co0.3CO3/RGO delivers an ultrahigh capacity of 1454 mA h g−1 after 130 cycles at 100 mA g−1 and exhibits an ultralong cycling stability (901 mA h g−1 after 1500 cycles at 2000 mA g−1). This is the best lithium storage performance among carbonate‐based anodes reported up to date. Such superb performance is attributed to the hybrid structure and enhanced electroconductivity due to the integration of Co and Mn into one crystal structure, which is complemented by electrochemical impedance spectroscopy and density functional theory calculations. The facile synthesis, promising electrochemical results, and scientific understanding of the MnxCo1−xCO3/RGO provides a design principle and encourages more research on TMCs‐based electrodes. [ABSTRACT FROM AUTHOR]

Hollow metal oxides and carbon hybrids with hierarchical and robust nanoarchitecture hold great potential as high-performance electrode materials. Herein, a relatively unexplored hollow and hierarchical metal–organic framework (MOF) assembled by parallel stacked triangular sub-MOFs were successfully synthesized via a facile co-precipitation method. The hollow MOFs were then converted to binary metal oxides@carbon composites, exemplified herein as Zn–Mn mixed oxides@carbon (ZnxMnO@C) hybrids. The obtained ZnxMnO@C inherits the unique hollow hexagonal nanodisks (HHNDs) structure of the MOF precursor, and each triangular plate-like subunit consists of a continuous carbon matrix embedded uniformly within the ultrafine ZnxMnO nanoparticles. When evaluated as an anode material for lithium ion batteries, the ZnxMnO@C HHNDs exhibited high specific capacity (1050 mA h g−1 at 0.1 A g−1 after 200 cycles) and remarkable cycling performance up to 1000 cycles. It is believed that besides the protection of the carbon matrix, the unique hierarchically hollow structure with parallel stacked subunits endows the ZnxMnO@C hybrid with additional capability to withstand lithiation/delithiation strain. Moreover, kinetics-analysis based on cyclic voltammograms (CVs) reveals that the high lithium storage capacity is primarily attributed to fast kinetics originating from pseudocapacitive contribution. This also accounts for the good rate capabilities of ZnxMnO@C HHNDs (713 and 330 mA h g−1 at 1 and 10 A g−1, respectively). Furthermore, full cells with Zn0.5MnO@C anodes and LiMn2O4 cathodes are assembled and show good cycling stability over 120 cycles. This study demonstrates a new hollow structure of MOFs and its usefulness in developing robust and hierarchical metal oxide/carbon composites for electrochemical storage applications. [ABSTRACT FROM AUTHOR]

Mn-Based compounds with high reversible capacities and eco-friendliness are one of the most promising anode materials for lithium ion batteries (LIBs), but their practical applications are still hindered by low rate capability, poor cycling stability, and high cost of production. Herein, we synthesize MnCO3/Mn3O4/reduced graphene oxide (MnCO3/Mn3O4/RGO) ternary composites through a green and facile strategy, which can take full advantage of the raw materials, mitigate pollution effectively, simplify the operating procedure, and shorten the preparation time to realize large-scale preparation. When used as anode materials for LIBs, benefitting from the advantage of their structure and effective synergy among MnCO3, Mn3O4 and graphene, the ternary composites exhibit an excellent cycling stability of 988 mA h g−1 after 200 cycles at 100 mA g−1 and 532 mA h g−1 after 800 cycles at 1 A g−1, which is superior to those of binary MnCO3/RGO and Mn3O4/RGO composites. Analyses using cyclic voltammetry, charge/discharge profiles, and electrochemical impedance spectroscopy reveal improved kinetics in the electrochemical reaction of the MnCO3/Mn3O4/RGO ternary composite with cycling. Furthermore, a systematic study of the potential difference of the redox reaction provides a good explanation for the observed electrochemical performance of the ternary composites. [ABSTRACT FROM AUTHOR]

ABSTRACT Flexible freestanding cotton-graphene (CGN) composites were prepared by a simple immersion and freeze-drying method and a thermal annealing process together. The composites had a constant cotton microstructure covered by graphene. The microstructure and morphology of the composites could be easily adjusted through the variation of the thermal annealing temperatures. Electrochemical tests demonstrated that the annealing temperatures had great effects on the electrochemical performances of the obtained composites. The CGN composite annealed at 700 °C exhibited a reversible capacity of 245.2 mAh/g after 100 cycles. Even after it was bent 1000 times, the CGN composite still maintained its superior electrochemical properties. The results suggest that because of its high flexibility and excellent conductive and electrochemical activities, the CGN composites could be used as lithium-ion battery anode materials on a large scale for corresponding applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44727. [ABSTRACT FROM AUTHOR]

Engineering two transition metals into an integrated spinel oxide anode provides great opportunity towards high-performance lithium-ion batteries (LIBs). Spinels with high-valence transition metal oxides (TMOs) however tend to exhibit low initial coulombic efficiency (ICE) due to the irreversible Li2O generated during the first discharge process. Herein, we report a simple and general strategy to synthesize elaborate graphene framework (GF) supported low-valence bicomponent transition metal monoxide anodes (e.g., ZnO–MnO microcubes, ZnO–CoO polyhedra, NiO–CoO nanowires, and (FeO)0.333(MnO)0.667 microspheres, etc.), which can efficiently address the low ICE issue. As a proof of concept demonstration, we show that the ZnO–MnO/GF is indeed more advantageous as an LIB anode over the spinel ZnMn2O4/GF counterpart as well as many other ZnMn2O4-based anodes. Benefiting from the enhanced reversibility of Li+ uptake/extraction and graphene hybridization, the ZnO–MnO/GF electrode exhibits significantly improved ICEs at various current densities, superior rate capability (286 mA h g−1 even at a high current density of 6 A g−1; ∼2.9 min charging/discharging), and extended cycling life (1123 mA h g−1 after 300 cycles) with respect to ZnMn2O4/GF. Such improvements have also been observed for the ZnO–CoO/GF electrode and other analogues. This versatile electrode design could advance our understanding and control of complex TMO-based anodes to gain high ICE and capacity. [ABSTRACT FROM AUTHOR]