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The hydrated salt disodium hydrogen phosphate dodecahydrate (DHPD, Na2HPO4·12H2O) has a suitable phase transition temperature and high latent heat of phase transition. Still there are problems such as supercooling, phase separation, and low thermal conductivity. In this paper, DHPD, sodium carboxymethyl cellulose (CMC), aluminum oxide (Al2O3), and poly(vinylpyrrolidone) (PVP) are used to configure DHPD-CAP to suppress supercooling and phase separation successfully. Multiwalled carbon nanotubes (MWCNTs) are used to stabilize DHPD-CAP phase-change materials and improve the thermal conductivity of pure DHPD. Further studies show only a physical interaction between MWCNTs and DHPD, and no new phases are generated. The addition of MWCNTs can also promote the nucleation of the DHPD-CAP composite, and the corresponding latent heat of phase change shows a trend of increasing and then decreasing with the increase of MWCNT content. Compared with DHPD after one cycle, the latent heat of DHPD-CAP/MWCNT4 increases by 36.19%. With the addition of MWCNTs, the thermal stability of the composites is improved compared to pure DHPD. The DHPD-CAP/MWCNT4 composite has good stability after many cycles.

The challenge for current lithium-ion capacitors (LICs) to obtain high energy density is to improve the energy storage performance at high rates. The key lies in balancing the kinetics mismatch between battery-type anode and capacitor-type cathode as well as ensuring high capacity contribution of electrodes. To this end, graphene aerogel (GA) supported high-capacity silicon (Si) nanoparticles 3D conductive framework is designed as anode for LICs, overcoming the notably volume expansion (300%) of Si and contributing to the high energy density. More importantly, a dominating capacitive mechanism lies in the intercalation process of Si@GA anode, which enables its fast charge–discharge capability. So as to match the high capacity anodes, boron carbonitride nanotubes (BCNNTs) with high-rate pseudocapacitive behavior and desirable capacity are used as cathode to construct a novel LIC with high energy density. Benefiting from high-rate capabilities of both anode and cathode, the rational designed 4.5 V Si@GA//BCNNTs LIC exhibits excellent electrochemical performance, delivering a maximum energy density of 197.3 W h kg−1 at the power density of 225 W kg−1. This strategy may widen the application for materials with volume expansion issues and many other material systems in pseudocapacitive advanced high-rate devices.

In-depth research on energy storage and conversion is urgently needed; thus, water splitting has become a possible method to achieve sustainable energy utilization. However, traditional carbon material with high graphitization degree exhibits a relatively low electrocatalytic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activity as it is electrochemically inert. In this work, according to the Lewis theory of acids and bases and the density functional theory (DFT) results, which show that the enriched heteroatom of B/N in the boron carbonitride (BCN) system may introduce stronger adsorption strength of OH*/H2O, respectively, we have designed and synthesized self-supporting BCN materials with different enrichment degrees of B/N (B-BCN/N-BCN) using carbon paper as substrate. Furthermore, by adjusting the contents of B and N, the optimum electrocatalytic performance of overall water splitting was obtained in which the onset voltage of water splitting on B-BCN//N-BCN was lower than 1.60 V. Our strategy of synthesizing materials with different heteroatom enrichment to improve the electronic environment of materials has opened up new opportunities for developing efficient metal-free electrocatalysts.

Nanowires (NWs) with high aspect ratios (HARs) have great advantages for the fabrication of nanodevices. Herein, a high-efficiency and simple physical vapor transport (PVT) method is utilized to synthesize the uniform HAR aluminum nitride (AlN) NWs on a tungsten substrate without any catalysts. Synergistic effect of high surface energy of (0001), low saturated vapor pressure and large axial temperature gradient leads to the growth of HAR AlN NWs, which provides new insight for the growth of low-dimensional AlN nanostructures. The as-obtained AlN NWs with super HAR have hexagonal wurtzite structure, the diameters are about 100 nm and the lengths are over 200 μm. The AlN NWs have an intensive deep ultraviolet (DUV) absorption peak at 5.94 eV and exhibit a relatively high electrical conductivity (1.29 × 10−3 Ω−1 cm−1), low turn-on field (6.2 V μm−1) and threshold field (8.5 V μm−1). These results indicate that PVT method is efficient to fabricate HAR AlN NWs and the AlN NWs not only play an important role in DUV photoelectric devices but also have tremendous potential as a candidate for field-emission nanodevices.

In-situ construction of edge site-enriched transition metal sulfides coupled graphene hybrids holds an effective strategy for high-performance lithium-ion storage. Here, a hybrid architecture with edge site-enriched VS4 electroactive species anchored on graphene sheet is tailor-made as an ideal host for Li+ via a simple in-situ assembly process. The etching effect is an indispensable factor in the formation of hybrid structure with ultra-rich edge sites, which makes a positive contribution to the surface-structure activity. The integrated hybrids not only guarantee a high utilization of electroactive species and fast reaction kinetics, but also open up synergistic electrochemical properties. Thus, the optimized VS4/Graphene electrodes exhibit uplifting specific capacity (1220 mAh g−1 at 1 A g−1), superb rate (476 mAh g−1 at 20 A g−1), and excellent cycling durability (100% maintains over 1000 cycles at 10 A g−1). In addition, an irreversible amorphous transition and redox reaction mechanism in the first cycle have been revealed. This work is expected to expound a feasible strategy for the progress of energy storage system.

Herein, we propose a practical way for direct preparation of gallium oxide nanosheets/reduced graphene oxide (Ga2O3 NSs/rGO) nanocomposites via oxygenic groups contained hydrophilic graphene oxide (GO) template with subsequent annealing treatment. Benefiting from the two-dimensional (2D) nanoarchitecture of Ga2O3 NSs and rGO, Ga2O3 NSs/rGO nanocomposites exhibit enhanced kinetics and improved cycling stability in Li-ion and Na-ion batteries (LIBs/SIBs). The pseudocapacitance performance is authenticated through kinetic analysis. Ex situ XRD and XPS measurements prove that the reversible Li-ion storage in Ga2O3 NSs/rGO electrodes is a conversion reaction and alloying mechanism. In addition, the full cells fabricated by coupling Ga2O3 NSs/rGO anode and LiFePO4/C or Na3V2(PO4)3/C cathodes exhibit outstanding electrochemical performances. In general, such a new approach, which is not specific to Ga2O3 NSs/rGO nanocomposites, offers great opportunities for 2D oxide nanomaterials or nanocomposites as high-perfo...

Two-dimensional transition metal dichalcogenides (TMDCs) exhibit excellent optoelectronic properties. However, the large band gaps in many semiconducting TMDCs make optical absorption in the near-infrared (NIR) wavelength regime impossible, which prevents applications of these materials in optical communications. In this work, we demonstrate that Ar+ ion irradiation is a powerful post-synthesis technique to tailor the optical properties of the semiconducting tungsten disulfide (WS2) by creating S-vacancies and thus controlling material stoichiometry. First-principles calculations reveal that the S-vacancies give rise to deep states in the band gap, which determine the NIR optical absorption of the WS2 monolayer. As the density of the S-vacancies increases, the enhanced NIR linear and saturable absorption of WS2 is observed, which is explained by the results of first-principles calculations. We further demonstrate that by using the irradiated WS2 as a saturable absorber in a waveguide system, the passively Q-switched laser operations can be optimized, thus opening new avenues for tailoring the optical response of TMDCs by defect-engineering through ion irradiation.

By introducing optimal velocity car-following model by Bando et al., we present an improved car-following model which is based on an optimal velocity model considering traffic jerk and full velocity difference. The nature of the model is researched by using linear and nonlinear analysis method. The analytical method and numerical simulation results show that the proposed model can describe the phase transition and critical phenomenon with the thermodynamic theory. In order to describe the traffic flow near the critical point, the time-dependent Ginzburg–Landau (TDGL) equation and the modified Korteweg–de Vries (mKdV) equation are derived. Additionally, the connection between the TDGL and the mKdV equation is also given. Theoretical analysis is demonstrated by numerical simulation.

Aim at the small-sample events of the torsional fault in marine, a method of shaft torsional vibration fault diagnosis in marine is proposed based on the theories of Shannon entropy of WT (Wavelet Packet) and DAGSVM (Directed Acyclic Graph Support Vector Machine). Firstly, the signals of four torsional vibration fault patterns are extracted relying on experimental platform of shaft torsional vibration in marine; then, extract the Shannon entropy of WPT for the input eigenvectors of SVM; Finally, identify the faults by using the SVM which advanced by the K-CV (K-fold Cross Validation) . The result shows that the method has higher recognition rate, providing a valuable on-line diagnostic method for the shaft torsional vibration fault diagnosis in marine.