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Nanostructured silicon carbide (SiC) materials are expected to have bright prospect in application as high-performance electrode materials with excellent charge–discharge cycling stability. However, the exploration of SiC-based micro-supercapacitors (MSCs) still remains a grand challenge seriously hampered by low areal capacities and complicated multistep production process. Herein, we report that rationally designed SiC/C nanocomposite with hierarchical porous structure and improved electrical conductivity has been realized by a facile and rapid carbothermic reduction using silica sol and sucrose as silicon and carbon source. The amorphous carbon between SiC nanoparticles (NPs) contributes to enlarged surface areas and excellent conductivity, not only ensuring intimate contact between the electrolyte and the electrode but also providing an effective ion highway for electrolyte ions. As a result, MSCs based on SiC/C nanocomposite (Si/C mass ratio of 1:1.5) demonstrate an optimal specific areal capacitance of 11.8 mF cm−2 at 2 mV s−1, outstanding flexibility (104.5% retention of initial capacitance at 180° bending), and superior integration. Most notably, the capacitance remains at 97.3% of the initial value after 50000 charging/discharging cycles, superior to that of most advanced SiC-based MSCs ever reported. This work demonstrates an effective design for hierarchical porous SiC/C nanocomposite for energy storage, which gives significant inspirations on the exploration of high-performance SiC-based MSCs.

A series of excellent works have demonstrated that high-nitrogen-content metal pentazolate (cyclo-N5–) compounds could be stabilized by high pressure. However, under ambient conditions, low stability precludes their synthesis and application in the field of high-energy-density material. In this work, by using a constrained structure search method, we predicted two new structures as P212121-CuN5 and P21/c-CuN5 containing cyclo-N5– with strong N–N and Cu–N bonds. In both structures, cyclo-N5– form four coordination with the Cu+ ligand, which increases the structural stability by lowering the disturbance to the aromaticity of cyclo-N5–. The calculated results show that the P212121-CuN5 and P21/c-CuN5 structures exhibit high dynamic and thermal stability up to 400 K, indicating that they can be stabilized under ambient conditions. The decomposing energy of P212121-CuN5 and P21/c-CuN5 can reach up to 2.40 and 2.42 kJ/g, respectively. Strikingly, the detonation velocity and the pressure of P212121-CuN5 is predicted to be up to 10.42 km/s and 617.46 kbar, respectively, indicating that they are promising high-energy candidates in the field of explosive combustion.

Polycrystalline diamond with high mechanical properties and excellent thermal stability plays an important role in industry and materials science. However, the increased inherent brittle strength with the increase of hardness has severely limited its further widespread application. In this work, we produced well-sintered nano-polycrystalline (np) diamond by directly sintering fine diamond powders with the boron carbide (B4C) additive at high pressure and high temperatures. The highest hardness value of up to ∼90 GPa was observed in the np-diamond (consisting of fine grains with a size of 16 nm) by adding 5 wt% B4C at 18 GPa and 2237 K. Moreover, our results reveal that the produced samples have shown noticeably enhanced strength and toughness (18.37 MPa m0.5) with the assistance of the soft phase at the grain boundaries, higher than that of the hardest known nano-twined diamond by ∼24% and a little greater than that of the toughest CVD diamond (18 MPa m0.5). This study offers a novel functional approach in improving and controlling the hardness and stiffness of polycrystalline diamond.

Recent discoveries in high pressure science have revealed entirely unexpected chemical behavior of two-dimensional (2D) materials. However, there is still a lack of unambiguous insight on the pressure-driven behavior of in-plane bonds in the 2D layered structures. Layered germanium phosphide (GeP5) is a metal with honeycomb-like sheets structurally similar to semiconducting black phosphorous, but with electrical conductivity ten times higher than that of graphite. Here, we report a remarkable pressure-dependent structural transformation that includes lengthening of the main in-plane bonds under pressure, although practically high pressure usually leads to shorter stiffer bonds. In situ Raman measurements show that there is significant phonon mode softening through the 2D–3D structural reconstruction, correlating with the in-plane bond extensions in GeP5 upon compression. This is accompanied by unusually superconducting behavior, on both sides of the transformation. This superconductivity with a maximum transition value of 10.5 K at 13.5 GPa shows a robust character without obvious reduction up to 60 GPa and is accompanied by pressure-induced amorphization in GeP5. Our experimental results, together with those from first principles calculations, not only provide the detailed high-pressure phase diagram of GeP5 but also connect the pressure-dependent bond extension with enhanced superconductivity.

Recently, it has been reported that high-pressure synthesized lithium pentazolates could be quenched down to ambient conditions. However, the crystalline structures of LiN5 under ambient conditions are still ambiguous. In this work, the structures of LiN5 compound were directly explored at atmospheric pressure by using a new constrain structure search method. By using this method, three new allotropes were confirmed, and they show lower energy than the previous reported LiN5 phases. Both their thermodynamic and dynamic stability were confirmed through formation enthalpies, phonon spectrum, and ab initio molecular dynamics simulations under ambient conditions. Moreover, these three allotropes show similar formation enthalpies and properties, which suggests that it is hard to obtain a single LiN5 phase, which is well consistent with the experimental phenomenon. Furthermore, because of their low formation energy, all of them possess low energy density when they directly decompose to Li3N and nitrogen (0.52 kJ/g). Instead, the decomposed energy could be further improved to 3.78 kJ/g when they decompose under an oxygen-rich environment.

The ω-zirconium (ω-Zr) is generally considered as the favorable strengthening phase in the application of Zr and its alloys. However, the intrinsic mechanism is still unclear. In this study, the elastic constants and anisotropic ideal shear strengths of ω-Zr and the common α-Zr phase are systematically studied by the first-principle calculations. Results reveal that the shear modulus of ω-Zr is 1.37 times that of α-Zr. The lowest shear strength of ω-Zr is 3.25 GPa along ( 1 0 1 ¯ 0 ) [ 0 0 0 1 ] , which is about 1.6 times the weakest shear strength (2.01 GPa) of α-Zr along ( 1 0 1 ¯ 0 ) [ 1 ¯ 2 1 ¯ 0 ] . In addition to the high strength, the critical strain of ω-Zr is 0.173, much larger than that (0.072) of α-Zr. The electron localization function (ELF) result shows that there are more electrons highly localized in ω-Zr than in α-Zr along their weakest shear directions, indicating the stronger metallic bonds of ω-Zr as the origin of the high shear strength and strain. In addition, based on the von Mises criteria, the dominating deformation mode for the polycrystalline material of ω-Zr is proposed along the { 1 0 1 ¯ 0 } 〈 0 0 0 1 〉 / { 1 0 1 ¯ 1 ¯ } 〈 1 ¯ 2 1 ¯ 0 〉 or { 1 1 2 ¯ 0 } 〈 0 0 0 1 〉 / { 1 0 1 ¯ 1 ¯ } 〈 1 ¯ 2 1 ¯ 0 slips, which is helpful to the understanding of deformation behavior in polycrystalline ω-Zr.

Polytetrafluoroethylene/poly(methyl methacrylate) (PTFE/PMMA) composites were prepared by a self-curing method. The influence of heat treatment processes on the friction and wear behaviors of PTFE/PMMA composites against bearing steel balls were studied by a ball-on-disk tribometer. The thermal performance of PTFE/PMMA composites with heat treatment was analyzed by Thermogravimetric Analysis (TGA). The surface morphologies and element distribution of PTFE/PMMA composites in a PMMA matrix were detected by Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive Spectroscopy (EDS). The results indicated that the wear rates of PTFE/PMMA composites with different heat treatments significantly declined compared with the unheated treatment composite. The wear rate of the PTFE/PMMA composite decreased firstly and then increased with molding temperature and time increasing, and reduced with the molding pressure increasing. The main wear mechanisms of PTFE/PMMA composites with different heat treatments were fatigue wear and abrasive wear.

Zirconium-immobilized bentonite was prepared by hydrothermal reaction, and characterized by scanning electronic microscope (SEM) and X-ray diffraction (XRD) techniques. Removal of methyl orange (MO) from aqueous solutions with zirconium-immobilized bentonite was investigated by a batch method. These factors including adsorbent dosage, pH value of MO solution, and contact time were evaluated. Adsorption equilibrium was achieved at 60 min or so. The experimental isotherm data were described by the Langmuir isotherm model. The maximum adsorption capacity obtained from the Langmuir isotherm model was 44.13 mg/g at 298 K and natural pH value. An increase in temperature reduced the adsorption of MO while the increasing amount of zirconium enhanced the adsorption of MO onto Zr-immobilized bentonite. 1 M HCl was identified as the best eluent.

Recently, there have increasingly been debates on whether there exists a surface resonance state (SRS) in black phosphorus (BP), as suggested by recent angle-resolved photoemission spectroscopy results. To resolve this issue, we have performed temperature- and angle-dependent magnetoconductivity measurements on exfoliated, high-quality BP single crystals. A pronounced weak-antilocalization (WAL) effect was observed within a narrow temperature range of 8-16 K, with the electrical current flowing parallel to the cleaved ac-plane (along the a- or c-axis) and the magnetic field along the b-axis. The angle-dependent magnetoconductivity and the Hikami-Larkin-Nagaoka model-fitted results have revealed that the observed WAL effect shows surface-bulk coherent features, which supports the existence of SRS in BP.

A multifunction adsorbent, activated carbon (AC)/chitosan composite, was synthesized by incorporating AC into chitosan based on the ratio of AC to chitosan being 1/1. The simultaneous adsorption of aniline and Cu2+ from aqueous solution onto AC/chitosan composite was investigated by a batch procedure. These results showed that an adsorbent dosage of 0.3 g was appropriate, and a contact time of 210 min was convenient for reaching adsorption equilibriums for aniline and Cu2+. The simultaneous adsorption of aniline and Cu2+ was realized in a wide pH range. The adsorption process obeyed the pseudo-second-order kinetic model. The adsorption behaviors of aniline and Cu2+ followed Freundlich and Langmuir, respectively. No obvious competitive adsorption existed between Cu2+ and aniline.

Layered germanium phosphide, which combines the advantages of both germanium and phosphorus, is believed to be a potential anode for sodium ion battery. Here, the sodium storage mechanism and electrochemical performance of layered germanium phosphide have been deeply investigated by advanced in-situ transmission electron microscopy technique combining half-cell testing. Dynamic reaction process reveals that individual layered germanium phosphide nanoflake undergoes total area expansion of 248% without any detectable fracture or cracking in sodiation. In contrast, germanium phosphide experiences multi-step reactions, i.e. intercalation and alloying, accompanied by sequentially forming NaxGeP (0

In the present study, chitosan has been chemically modified by crosslinking and protonation. Protonated crosslinked chitosan (PCC) was employed as an adsorbent to remove amido black 10B from aqueous solution. Adsorption experiments were performed by varying initial dye concentration, pH value of the solution, contact time, and temperature. The adsorption of amido black 10B onto PCC obeyed Langmuir isotherm. The adsorption capacity was 9.43 mg g−1 at 293 K. Thermodynamic studies revealed that the nature of amido black 10B adsorption was spontaneous and endothermic. Sorption kinetics was mainly controlled by pseudo-second-order model. About 0.1 M NaOH was identified as the best eluent.

An adsorbent was prepared from bentonite modified by hexadecyltrimethylammonium bromide (HDTMAB) and N-2-hydroxypropyl trimethyl ammonium chloride chitosan (HTCC). This adsorbent was named as HDTMAB–HTCC bentonite. It would be used for the simultaneous adsorption of phenol and Cr(VI) from aqueous solution. By the method of single-factor experiment, the optimum preparation conditions of HDTMAB–HTCC bentonite were obtained. For bentonite (5 g), 1.0 g HDTMAB and 0.5 g HTCC were adopted as the modifying reagents. The reaction was carried out for 2 h at 80°C. The removals towards phenol and Cr(VI) enhanced with the increase in the amount of adsorbent dosage. The relatively high removals towards phenol and Cr(VI) occurred at a pH value of 1.5 or so. During the simultaneous adsorption process of phenol and Cr(VI), phenol was adsorbed by the partition from the organic phase formed by HDTMAB, while Cr(VI) was mostly adsorbed by the electrostatic interactions between HTCC and Cr(VI). No direct competition w...

This study provided information on the preparation and the Cr (VI) adsorption potential of N-2-hydroxypropyl trimethyl ammonium chloride chitosan (HTCC)–bentonite nanocomposite as an absorbent. HTCC–bentonite was characterized by small angle x-ray diffraction, Fourier transforming infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Batch adsorption experiment of chromium was performed to investigate the effects of pH, initial concentration, adsorbent dosage, contact time, etc. The maximum adsorption was observed at a pH value of 1. Adsorption of chromium on HTCC–bentonite was favored at lower temperature and established equilibrium in 30 min. The Cr (VI) adsorption followed Langmuir isotherm models, and the maximum adsorption capacity was obtained at 22.17 mg g−1.

A novel type of adsorbent was prepared by modifying bentonite with N-2-hydroxypropyl trimethyl ammonium chloride chitosan (HACC) with cetyl trimethylammonium bromide (CTAB). The adsorbent was named CTAB-HACC bentonite. Its characteristics were investigated using thermogravimetric, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction. The adsorption of phenol onto CTAB-HACC bentonite was evaluated by changing various parameters, such as contact time, adsorbent dosage, initial pH of the solution, and temperature. The maximum adsorption was observed at pH 12. Adsorption of phenol on CTAB-HACC bentonite favored at lower temperature and established the equilibrium in 30 min. The adsorption efficiency reached 82.1%, and the adsorption capacity was 7.12 mg/g from the phenol solution with a concentration of 500 mg/L at pH 12.0 and 20 °C.

Black Phosphorus (BP) is presently attracting immense research interest on the global level due to its high mobility and suitable band gap for potential application in optoelectronics and flexible devices. It was theoretically predicted that BP has a large direction-dependent electrical and magnetotransport anisotropy. Investigations on magnetotransport of BP may therefore provide a new platform for studying the nature of electron transport in layered materials. However, to the best of our knowledge, magnetotransport studies, especially the anisotropic magnetoresistance (MR) effect in layered BP, are rarely reported. Here, we report a large linear MR up to 510% at a magnetic field of 7 Tesla in single crystals of BP. Analysis of the temperature and angle dependence of MR revealed that the large linear MR in our sample originates from mobility fluctuations. Furthermore, we reveal that the large linear MR of layered BP in fact follows a three-dimensional behavior rather than a two-dimensional one. Our results have implications to both the fundamental understanding and magnetoresistive device applications of BP.

A kind of biocomposite was prepared by the intercalation of chitosan in bentonite and the cross-linking reaction of chitosan with glutaraldehyde, which was referred to as cross-linked chitosan/bentonite (CCS/BT) composite. Adsorptive removal of methyl orange (MO) from aqueous solutions was investigated by batch method. The adsorption of MO onto CCS/BT composite was affected by the ratio of chitosan to BT and contact time. pH value had only a minor impact on MO adsorption in a wide pH range. Adsorption kinetics was mainly controlled by the pseudo-second-order kinetic model. The adsorption of MO onto CCS/BT composite followed the Langmuir isotherm model, and the maximum adsorption capacity of CCS/BT composite calculated by the Langmuir model was 224.8 mg/g. Experimental results indicated that this adsorbent had a potential for the removal of MO from aqueous solutions.

In this work, enhanced chitosan/bentonite composite was prepared by treating chitosan/bentonite composite with concentrated hydrochloric acid (HCl). The adsorption of fluoride ions from aqueous solution onto the enhanced chitosan/bentonite composite was investigated. Adsorption studies were performed in a batch system, and the effects of various parameters, such as the pH value of the solution, adsorbent dosage and initial fluoride concentration, were evaluated. The optimum operating conditions for fluoride removal by the enhanced chitosan/bentonite composite were pH = 7 or so, and adsorbent dosage =1.2 g. Increasing initial fluoride concentration reduced the adsorption of fluoride onto the enhanced chitosan/bentonite composite. Furthermore, the presence of other co-anions weakened the adsorption of fluoride onto this adsorbent. The equilibrium adsorption isotherms were well described by both the Freundlich and Langmuir models. The maximum monolayer adsorption capacity was 2.95 mg/g at 293 K.