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Li–S batteries have been considered as one of advanced next-generation energy storage systems owing to their remarkable theoretical capacity (1672 mAh g–1) and high energy density (2600 Wh kg–1). However, critical issues, mainly pertaining to lithium polysulfide shuttle and slow sulfur reaction kinetics, have posed a fatal threat to the electrochemical performances of Li–S batteries. The situation is even worse for high sulfur-loaded and flexible cathodes, which are the essential components for practical Li–S batteries. In response, the use of metal compounds as electrocatalysts in Li–S systems have been confirmed as an effective strategy to date. Particularly, recent years have witnessed many progresses in phosphides-optimized Li–S chemistry. This has been motivated by the superior electron conductivity and high electrocatalytic activity of phosphides. In this tutorial review, we offer a systematic summary of active metal phosphides as promoters for Li–S chemistry, aiming at helping to understanding the working mechanism of phosphide electrocatalysts and guiding the construction of advanced Li–S batteries.

Achieving ultra-high thermal conductivity while maintaining the electrical insulation of polymers is highly desirable for many applications such as thermal management and packaging. In this work, polyethylene/boron nitride nanoplatelets (PE/BNNP) nanocomposite film was produced through melt processing followed by uniaxial stretching. Microstructural analysis reveals that the stretched composite film features a co-continuous network structure which consists of oriented lamellae bridged by both stretched polymer chains and aligned BNNPs along the stretching direction. The resulting film exhibit a metal-like thermal conductivity as high as 106 W m−1 K−1 and it is believed that the unique network structure has enabled efficient phonon transfer across the film, resulting in superior thermal transporting performance. This work shines a light on the design and scalable manufacturing of high performance functional polymer-based composites for future thermal management applications.

The internal dispersion structure of silica fillers in polymer matrix is significant for design and fabricating high-performance polymer composite. In order to explore the relationship between fillers spatial dispersion states and mechanical properties, we use superficial fluorescent labeling to achieve fillers visualization in polymer matrix with laser scanning confocal microscopy. Through the effect of fluorescent silane coupling agent, the uniform red fluorescence characteristics were shown on the silica surface. The 2D-planar and 3D-spatial dispersion states of silica fillers in rubber matrix can be accurately observed with fluorescence imaging technology. The results by Avizo software statistics show that high-content silica fillers in composite tend to undergo dissociation of aggregates. These dissociated small volume aggregates which facilitate the interaction between particles and rubber matrix to dissipate mechanical energy effectively and rapidly improve rubber toughness. This successful visualization method opens a new avenue in spatial dispersion description of fillers aggregates in organic–inorganic composite.

We have successfully constructed a novel type of recyclable crosslinked protonated-polybenzotriazole ether sulfone (PBTSH+), which possessed outstanding thermal stability and mechanical properties. More importantly, the tensile strength of the resulting crosslinked films could be visually detected by taking advantage of the transparency decreasing effect of synergistic hydrogen bonds between protonated benzotriazole units.

The mechanical properties and the hierarchical filler structures were characterized on a series silica-filled silicone rubber with a filler fraction (ΦSi) varied from 0.05 phr to 80 phr (parts per hundred rubber). Uniaxial elongation measurement suggests that there is a percolation threshold between 10 and 30 phr. Moreover, an optimum ΦSi range from 40 phr to 50 phr is found, in which the best mechanical performances of reinforcement are shown. The microscopic structures were crosschecked by small-angle neutron scattering (SANS) and scanning electron microscopy (SEM). The effects of the ΦSi and the fabrication process on the morphology of samples are unveiled. The correlation length among aggregates extracted from SANS data monotonically decrease from 237.0 nm to 136.5 nm with increasing the ΦSi from 30 phr to 80 phr. The average radius of gyration of aggregates 〈Rg,agg〉 fitted with the Beaucage model monotonically decrease from 49.2 nm to 37.5 nm with increasing ΦSi from 10 phr to 80 phr. Providing a 10 nm thickness bound rubber as bridge, samples with optimum ΦSi yield a morphology that the radii of aggregates and the gap filled with polymer matrix in between are equivalent as both around 60 nm.

Two-dimensional nanosheets obtained by exfoliation can assemble into new functional nanomaterial. One of the critical challenges is developing an efficient method to make the layered composite complete exfoliation, and another is regulating and controlling nanosheets assembly to obtain the nanocomposite with specific structure. In this article, the platelets of layered double hydroxides (LDH) and montmorillonite (MMT) are exfoliated completely and efficiently in polylactic acid (PLA) by melting blend for 10 min, and the monolayers of MMT or LDH can store stably in PLA for a long time. A new well-organized layered nanocomposite containing the nanosheets of LDH and MMT was gained by being exfoliated and assembling. The structure of MMT/LDH nanocomposite not only holds a periodically alternating structure, but also possesses a train structure, and the formation mechanism of train structure is proposed at the first time; furthermore, the structure of MMT/LDH could be regulated and controlled. Fortunately, even being exfoliated and assembled, MMT nanosheet or LDH nanosheet was not destroyed. The MMT/LDH nanocomposite with expectant structure can be obtained by this efficient and environmentally friendly method, and this method may easily be extended to other layered materials.

Adding silica nanofiller in silicone rubber can toughen the matrix 3 orders in terms of fracture energy, which is far larger than most other nanofiller–rubber systems. To unveil the astonishing toughening mechanism, we employ in situ synchrotron radiation X-ray nanocomputed tomography (Nano-CT) technique with high spatial resolution (64 nm) to study the structural evolution of silica nanofiller in silicone rubber matrix at different strains. The imaging results show that silica nanofiller forms three-dimensional connected network, which couples with silicone chain network to construct a double-network structure. Stress-induced phase separation between silica nanofiller and silicone polymer chain networks is observed during tensile deformation. Unexpectedly, though the spatial position and morphology of nanofiller network changes greatly at large strains, the connectivity of nanofiller network shows negligible reduction. This indicates that nanofiller network undergoes destruction and reconstruction simult...

The hierarchical structures of silica-filled silicone rubber have been investigated by using contrast variation small-angle neutron scattering (CV-SANS) and transmission electron microscopy (TEM). A series of scattering intensities of swollen samples were measured with varying ratio of hydrogenated toluene/deuterated toluene solvent. By using CV-SANS method, the partial scattering functions, self-terms of silica S SS ( q ) and silicone rubber S RR ( q ), as well as cross-term between silica and silicone rubber S RS ( q ), are successfully extracted. The fine parameterization of morphology is characterized and elucidated by adopting unified Guinier-exponential/power-law equations, the fitted results indicate: (i) the volume fraction of silicone rubber in bound rubber and matrix regions, are respectively 0.80 and 0.31. Such spatial inhomogeneous of swelling ratio suggests that there is existence of the immobilized layer; (ii) the average aggregation size is ca . 143 nm, and there are about 24–97 silica particles in each aggregation; (iii) the thickness of the bound rubber is estimated as in the range of ca . 7.2–8.5 nm. A mimic collection and observation of aggregations and bound rubber with TEM confirm the CV-SANS results. Current work provided a scenario to evaluate the reinforcement effect of the silica on the silicone rubber even before any mechanical testing.

The mechanical response of fluoroelastomer F2314 under uniaxial extension and its relation with strain-induced structural change are investigated by mechanical analysis, in-situ small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS). Yielding of samples followed by strain hardening is found without necking. Meanwhile, the strain range of strain softening is short, which is 0.77 at 25 °C and 0.3 at 60 °C. Microscopically, solution-cast F2314 shows microphase separation and low crystallinity. Results of WAXS and SAXS indicate strain-induced formation of fibrillar crystal during strain hardening. Based on these findings, it is supposed that the fast relay between destruction of microphase separated domains and formation of fibrillar crystal is the origin of the unique mechanical response.

Layered double hydroxides (LDHs), as an effective oxygen evolution reaction (OER) electrocatalyst, face many challenges in practical applications. The main obstacle is that bulk materials limit the exposure of active sites. At the same time, the poor conductivity of LDHs is also an important factor. Exfoliation is one of the most direct and effective strategies to increase the electrocatalytic properties of LDHs, leading to exposure of many active sites. However, developing an efficient exfoliation strategy to exfoliate LDHs into stable monolayer nanosheets is still challenging. Therefore, we report a new and efficient solid-phase exfoliation strategy to exfoliate NiFe LDH and graphene oxide (GO) into monolayer nanosheets and the exfoliating ratios of NiFe LDH and GO can reach up to 10 and 5 wt %, respectively. Based on the solid-phase exfoliation strategy, we accidentally discovered that there is a dynamic evolution process between NiFe-LDH nanosheets (NiFe-LDH-NS) and GO nanosheets (GO-NS) to assemble new NiFe-LDH/GO nanohybrids, i.e., NiFe-LDH-NS could be horizontal bespreading on GO-NS or well-organized standing on GO-NS, or both simultaneously. The electrocatalytic OER property test results show that NiFe-LDH/RGO-3 (NFRG-3) nanohybrids obtained by the reduction treatment of NiFe-LDH/GO-3 (NFGO-3) nanohybrids, in which NiFe-LDH-NS are well-organized standing on GO-NS, have excellent electrocatalytic properties for OER in an alkaline solution (with a small overpotential of 273 mV and a Tafel slope of 49 mV dec

High-efficient nanosheets exfoliation and ordered controlled stacking are in urgent need of work for electrochemistry application. Here, we have developed a high-efficient and environmentally-friendly solid-phase method for the exfoliation of Co-Al layered double hydroxide (Co-Al LDH) and graphene oxide (GO). Meanwhile, we found that there is a dynamic structure evolution in the self-assembly process between Co-Al LDH-NS and GO-NS and new theoretical structure models were proposed. With the reduction treatment, the electrochemical test results show that Co-Al LDH/rGO-3 with ideal tiling structure has better electrochemical performance, which provides a specific capacitance of 1492 F g−1 at 1 A g−1 and remains the capacitance retention at approximately 94.3% after 5000 cycles. Moreover, an energy density of 44.6 Wh kg−1 is obtained at a power density of 799.6 W kg−1. The proposed method and the structure-relationship are practically applicable for other 2D materials in the asymmetric supercapacitors.

The intrinsic properties of the silicone rubber matrix reinforced by filler silica have been investigated with in situ rheo-small-angle neutron scattering (SANS) and deuterated chain labeling. SANS results reveal that: (i) the average diameter of aggregates and the thickness of bound rubbers (BR) are about 81 nm and 5.6 nm, respectively. (ii) The aggregates size distribution of the filler network is statistically stable during deformation. (iii) Strain mainly causes the agglomerate breakdown/reconstruction and the rubber matrix deformation. Interestingly, the evolution of the aggregates covered with BRs has the similar tendency to the nonlinear strain-stress curve (SSC). However, the tendency of the BR evolution diverges from the SSC. Considering the hydrodynamic amplification effect of filler and the filler-rubber interaction, a modified constitutive model is established and utilized to correlate the macroscopic properties with the micro-structure evolution of silicone rubber. The results suggest that the reinforced rubber matrix might play the dominant role in sustaining the external loading with a hardening effect. While filler presents contradiction effects for reinforcing yet suffering from the agglomerate breakdown and the interface weakening.

Porous carbon and metal oxides/sulfides prepared by using metal-organic frameworks (MOFs) as the precursors have been widely applied to the realm of supercapacitors. However, employing MOF-derived metal phosphides as positive and negative electrode materials for supercapacitors has scarcely been reported thus far. Herein, two types of MOFs are used as the precursors to prepare CoP and FeP4 nanocubes through a two-step controllable heat treatment process. Due to the advantages of composition and structure, the specific capacitances of FeP4 and CoP nanocubes reach 345 and 600 F g-1 at the current density of 1 A g-1 , respectively. Moreover, a quasi-solid-state asymmetric supercapacitor is assembled based on charge matching principle by employing CoP and FeP4 nanocubes as the positive and negative electrodes, respectively, which exhibits a high energy density of 46.38 Wh kg-1 at the power density of 695 W kg-1 . Furthermore, a solar-charging power system is assembled by combining the quasi-solid-state asymmetric supercapacitor and monocrystalline silicon plates, substantiating that the device can power the toy electric fan. This work paves a practical way toward the rational design of quasi-solid-state asymmetry supercapacitors systems affording favorable energy density and long lifespan.

With large quantities of waste carbon fiber reinforced polymer (CFRP) composites generated, the development of recycling routes for CFRP composites have been driven by both environmental and economic factors. Vitrimer materials provide exciting opportunities to recycle thermosets and CFRP composites, since they can be thermally reprocessed without losing their permanently cross-linked networks. However, the poor mechanical properties, additional catalyst and time-consuming recycling process still limit their applications. Herein, the authors proposed an epoxy vitrimer with high contents of exchangeable aromatic disulfide crosslinks to overcome these limitations. This epoxy vitrimer exhibited outstanding properties with the glass transition temperature (Tg) of 147 °C and the tensile strength of 63.1 MPa. Upon heating, it released the stress from deformation more rapidly without any catalyst, resulting from the high contents of disulfide crosslinks in the network. Meanwhile, the networks exhibited excellent reprocessability and were more readily degraded by thiols. Moreover, this epoxy was applied as matrix to prepare recyclable CFRP composites. By dissolving the epoxy matrix efficiently, the carbon fibers embedded were recycled rapidly and they still exhibited outstanding mechanical properties when being reused to form CFRP composites. Results from this study may promote the wide development of cost-efficient recyclable composites in automotive, wind power and aeronautical industries.

The detrimental shuttle effect and retarded sulfur reaction kinetics in lithium–sulfur (Li–S) chemistry mainly lead to inferior electrochemical performances, posing a fatal threat to the practical application of Li–S batteries. Herein, porous N-doped Ti3C2 MXene (P-NTC) has been realized by a scalable sacrificial templating route, resulting in the rational design of active electrocatalyst for Li–S chemistry. Benefiting from the superb electron conductivity, large surface area and strong interaction with lithium polysulfides (LiPSs), P-NTC can trigger the surface-mediated redox reaction of LiPSs. Moreover, the homogenous nitrogen doping on Ti3C2 gives rise to enhanced interfacial interaction with Li atom and lowered dissociation barrier for Li2S. Therefore, the template-derived P-NTC not only acts as an effective LiPS immobilizer but also serves as a multifunctional electrocatalyst to propel the nucleation and decomposition of Li2S in discharge and charge processes, respectively. As expected, thus-fabricated S/P-NTC cathode maintains a low capacity decay of only 0.033% per cycle at 2.0 C over 1200 cycles. In further contexts, our ability to tune the sulfur mass loadings enables fabricated cathodes to harvest a high areal capacity of 9.0 mAh cm−2, holding great promise in future practical applications.

In this paper, a new strategy was studied to fabricate graphene aerogel (GA)/polyethylene glycol (PEG) shape-stabilized phase change materials (PCMs) using a one-step method, i.e., when GA was set up based on the sheets of graphene oxide (GO), PEG was impregnated into the GA, simultaneously. PEG was restricted by GA owing to its capillary forces. Meanwhile, GA acted as supporting materials and thermal conductivity passageway; the GA/PEG shape-stabilized PCMs presented high heat storage capacity, and the PCMs kept their shapes stable without any leaking owing to GA more than the melting point of PEGs about 40 °C; the thermal conductivity of PEG-4K, PEG-6K, and PEG-10K with 1.30 wt% GA were increased about 28.86%, 27.74%, and 33.26% compared with those of pure PEGs, respectively. Generally, this one-step synthesis of GA/PEG shape-stabilized PCMs can support high loading of PEG, exhibited high thermal reliability and thermal conductivity.

The effects of bound rubber on vulcanization kinetics were studied on poly(methyl vinyl) silicone rubber (VMQ) filled with three different types of silica, which was surrounded by different amount of bound rubber due to their morphological differences. Higher specific surface area (SSA) and content of silica corresponds to the more favorable formation of bound rubber. The results of cure kinetic behavior demonstrate that the loading of silica suppresses the vulcanization rate compared to neat rubber. Under the same filler content, the higher the bound rubber content, the more obvious the inhibitory effect on vulcanization reaction. A structure model of filler network mediated by bound rubber was proposed to account for the influence of the reinforcing particles on vulcanization kinetics and rheological behavior of silicone rubber, which may be adopted to analyze the properties of nanocomposites with different fillers.

For a better understanding of the influence of the immobilized rubber on the non-linear viscoelasticity of filled rubber, spherical silica without intensive filler–filler interactions and with weak silica–rubber interactions was introduced in order to compare the non-linear viscoelasticity of the commercial silica filled rubber. It was observed that the amplitude of Payne effect is related to the interfacial interaction characterized by the content of bound rubber. An interesting phenomenon was produced in the effect of temperature on the Payne effect for spherical silica filled rubber that the amplitude of Payne effect decreases with the temperature below 253 K but the storage modulus increases with the temperature above 253 K which performs the feature of entropic elasticity as pure rubber. The activation energy of the unstable chains can be also divided into two sections in the temperature range which is related to the critical value of immobilized rubber to influence the Payne effect. The results reveal that the number of immobilized rubber reduces with the temperature and it has a critical value to affect the Payne effect which is verified by Maier–Goritz model. The introduction of this kind of spherical silica provides an experimental method to study the non-linear viscoelasticity elaborately.

Polyethylene glycol (PEG) as a phase change material (PCM) is limited in practical applications due to the three major drawbacks of low thermal conductivity, poor thermal stability, and easy leakage. In this study, a new shape-stabilized PPVA/GA/PEG PCM based on Phosphorylated polyvinyl alcohol (PPVA) and graphene aerogels (GA) as a “double-network” support material was obtained using a one-step method, and the three major obstacles of PEG as a PCM were well resolved in this composite material. 15%-PPVA/GA/PEG composite PCMs still exhibit high energy storage capacity while having high thermal stability and high shape-stabilized property. 15%-PPVA/GA/PEG composite PCMs (0.610 W m−1 K−1), with only 1.60 wt% GA, showed an enhanced thermal conductivity than that of PEG (0.493 W m−1 K−1), and it still exhibited an acceptable latent heat of fusion of 119.6 J g−1. Furthermore, the peak heat release rate of 15%-PPVA/GA/PEG composite PCMs decreased by 19.2% compared with PEG. The above experimental results indicate that the prepared PPVA/GA/PEG composite PCMs have application prospects in thermal energy storage field.

In this work thermo sensitivity was investigated with the bound rubber theory and thermoelasticity theory of the polymer-filler interface interaction between Polymethylvinylsiloxane (PMVS) and nanofillers (fumed and precipitated silica with the primary particle size of 10 nanometres). Bound rubber (the transition phase between PMVS and silica) content was measured by sol-gel analysis and swelling experiments. Results showed that the amount of bound rubber increases steadily with the increases of filler content. But the increasing rate suddenly decreased at certain silica content (between 40 and 50 phr of precipitated silica and between 30 and 40 phr of fumed silica, respectively), which was constant with the thermoelaticity experiment results. The temperature coefficients in low strain uniaxial extension are found to present sudden changing at the same silica content. This observation shows that thermo sensitivity is closely connected with the structure of polymer-filler interface.