Renewable, cost-effective and eco-friendly electrode materials have attracted much attention in the energy conversion and storage fields. Bagasse, the waste product from sugarcane that mainly ...contains cellulose derivatives, can be a promising candidate to manufacture supercapacitor electrode materials. This study demonstrates the fabrication and characterization of highly porous carbon aerogels by using bagasse as a raw material. Macro and mesoporous carbon was first prepared by carbonizing the freeze-dried bagasse aerogel; consequently, microporous structure was created on the walls of the mesoporous carbon by chemical activation. Interestingly, it was observed that the specific surface area, the pore size and distribution of the hierarchical porous carbon were affected by the activation temperature. In order to evaluate the ability of the hierarchical porous carbon towards the supercapacitor electrode performance, solid state symmetric supercapacitors were assembled, and a comparable high specific capacitance of 142.1 F g(-1) at a discharge current density of 0.5 A g(-1) was demonstrated. The fabricated solid state supercapacitor displayed excellent capacitance retention of 93.9% over 5000 cycles. The high energy storage ability of the hierarchical porous carbon was attributed to the specially designed pore structures, i.e., co-existence of the micropores and mesopores. This research has demonstrated that utilization of sustainable biopolymers as the raw materials for high performance supercapacitor electrode materials is an effective way to fabricate low-cost energy storage devices.
CeO2/TiO2 nanobelt heterostructures are synthesized via a cost‐effective hydrothermal method. The as‐prepared nanocomposites consist of CeO2 nanoparticles assembled on the rough surface of TiO2 ...nanobelts. In comparison with P25 TiO2 colloids, surface‐coarsened TiO2 nanobelts, and CeO2 nanoparticles, the CeO2/TiO2 nanobelt heterostructures exhibit a markedly enhanced photocatalytic activity in the degradation of organic pollutants such as methyl orange (MO) under either UV or visible light irradiation. The enhanced photocatalytic performance is attributed to a novel capture–photodegradation–release mechanism. During the photocatalytic process, MO molecules are captured by CeO2 nanoparticles, degraded by photogenerated free radicals, and then released to the solution. With its high degradation efficiency, broad active light wavelength, and good stability, the CeO2/TiO2 nanobelt heterostructures represent a new effective photocatalyst that is low‐cost, recyclable, and will have wide application in photodegradation of various organic pollutants. The new capture–photodegradation–release mechanism for improved photocatalysis properties is of importance in the rational design and synthesis of new photocatalysts.
The enhanced photocatalytic performance of CeO2/TiO2 heterostructured nanobelts is attributed to a novel capture–photodegradation–release degradation mechanism. During the photocatalytic process, MO molecules are captured by CeO2 nanoparticles on the surface of the heterostructure, then quickly photodegraded under UV or visible light irradiation, and ultimately the degradation products are released to external environment.
A large sized and high quality Nd:Sr3La2(BO3)4 laser crystal has been successfully grown by the Czochralski method. The room temperature (298.15K) and low temperature (77.2K) fluorescence spectra ...were studied, and inhomogeneous broadening phenomemon was found. Additionally, such a large bandwidth shows that Nd:Sr3La2(BO3)4 may possibly be used in laser systems to produce femtosecond pulses. Display omitted
•Nd:Sr3La2(BO3)4 crystal was grown by the CZ method.•The complete set of anisotropic thermal properties was systematically studied.•Polarized absorption and fluorescence spectral were measured.•CW laser operations at 1.06μm of Nd:Sr3La2(BO3)4 were demonstrated for the first time.
A novel disordered laser crystal Nd:Sr3La2(BO3)4 is characterized including its crystal growth, structure, thermal properties, inhomogeneously broadened spectra, and laser performance, which result that this crystal should be a promising gain material for the high-power ultrashort pulsed neodymium laser. The complete set of anisotropic thermal properties were systematically studied for the first time. It has been found that all the thermal conductivities along the three crystallographic directions increase with temperature, indicating a glass-like behavior. Polarized absorption and fluorescence spectra of Nd:Sr3La2(BO3)4 crystal were measured at 298.15K and 77.2K, respectively. The results show that both the absorption and the emission spectra of Nd3+ have been inhomogeneously broadened, and thus it is very promising to be used in laser systems to produce femtosecond pulses. CW laser operations at 1.06μm along the b-cut and c-cut directions have been demonstrated for the first time. A maximum power of 533mW with an optical conversion efficiency of 5.5% and slope efficiency of 6.4% was achieved in the c-cut sample.
FOX-7 self-assembled to form nanocrystals in FDU-15. Display omitted
► High explosive 1,1-diamino-2,2-dinitroethylene (FOX-7) self-assembled to form nanocrystals in mesoporous carbon FDU-15. ► ...Confinement effects of FDU-15 on 1,1-diamino-2,2-dinitroethylene nanocrystals were investigated. ► The FOX-7/FDU-15 composites showed low phase transition temperature and fast thermal decomposition rate. ► The FOX-7/FDU-15 composites showed extreme insensitivity to accidental stimuli.
Insensitive energetic materials are considerably desirable for insensitive munitions or low vulnerability ammunition compositions because of the reduced risks involved with their use. The ability to control compositions and properties for such materials is also of interest since it can lead to optimal performance, controlled energy release, and low sensitivity. With these goals in mind, we focus our work on a high energy density material, 1,1-diamino-2,2-dinitroethylene (FOX-7). FOX-7 nanocrystals under confined conditions are synthesized in mesoporous carbon FDU-15 through self-assembly. Complete impregnation can be achieved in N-methyl-2-pyrrolidone at 100–110°C, and the maximum amount of FOX-7 in the FOX-7/FDU-15 composites is around 43.8wt.% (C-43.8). Host–guest interactions are investigated by wide-angle XRD, 13C solid-state NMR, and FT-IR. C-43.8 shows low phase transition temperature and fast thermal decomposition rate compared with bulk FOX-7 crystals and the physical mixture. The host–guest structure of the composites demonstrates a novel and efficient space-insensitivity concept. C-43.8 shows no sensitivity toward both friction and impact, and insensitive to electrostatic spark (V50>37kV; E50>20J). The extreme insensitivity is closely related to the high thermal and mechanical stability of FDU-15.
Mesostructured surfactant/silicas were treated by AP–HNO3 oxidation to form template-free SBA-15 (a) or composites (b), and template-free SBA-15 showed high selectivity and adsorption capacity to the ...high explosive HMX Display omitted .
► “Pure” mesoporous silicas were prepared by ammonium perchlorate oxidation. ► Template-free mesoporous silicas of space group Fm3m, Im3m, and Ia3d were prepared. ► Mesoporous silicas products showed almost no obvious framework shrinkage. ► Mesoporous silicas products had a high concentration of surface silanol groups. ► The AP–HNO3 treated SBA-15 showed high selectivity and adsorption capacity to high explosive HMX.
The ammonium perchlorate (AP) oxidation strategy is used to treat as-made mesoporous silicas, resulting “pure” mesoporous silicas without obvious framework shrinkage or composites (polymer/silica or carbon/silica). The study is focused on the effect of assistant acids. This method can be applied to prepare template-free mesoporous silicas, such as those with space groups of p6mm (SBA-15), Fm3m, Im3m, and Ia3d. Structural characterizations are systematically provided by X-ray diffraction, transmission electron microscopy, N2 adsorption, element analysis, and Fourier transform infrared spectroscopy. The AP–HNO3 treated SBA-15 (N-SBA-15) shows high selectivity and adsorption capacity to HMX (4.7μmol/g), and can be used as a preconcentrating material for its separation and detection.
Graphene-based materials are promising electrodes for supercapacitors, owing to their unique two-dimensional structure, high specific surface area, and good electrical conductivity. In this paper, ...α-MnO2/Graphene composite materials with a unique 1D/2D hierarchical structure have been successfully prepared via a facile hydrothermal route. The morphology and structure of as-obtained products are systematically studied by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and N2 adsorption/desorption measurement. The electrochemical properties are investigated by cyclic voltammetry and galvanostatic charge–discharge. Finally, it is shown that the introduction of 1D α-MnO2 nanofibers could keep the space between the neighboring graphene sheets and prevent the aggregation and/or restacking of graphene, thus enhancing the effective surface area and electrochemical properties of the hybrid materials.
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•α-MnO2/Graphene composites materials were synthesized by a facile hydrothermal route.•The as-obtained nanocomposites have a novel 1D/2D hierarchically hybrid structure.•This novel hybrid structure of the composites is benefit for the electrochemical properties of the hybrid materials.
To promote the performance of nanoparticle electrocatalysts, a facile hydrothermal method is developed to generate core–shell nanocomposites with a metal catalyst core and a carbon shell. In this ...method, glucose serves as the reducing agent and carbon precursor while cetyltrimethylammonium surfactants serve as both pore structure-directing agents and nanoparticle capping agent. The accessibility of the metal catalyst core was examined by gas-phase ethylene hydrogenation and the electrocatalytic activity was tested by formic acid oxidation (FOR). The selection of halide counter ions used during the synthesis was found to be critical. The optimized sample of Pd-carbon nanocomposite exhibits a FOR current density of 2.55 mA/cm
2
, which is higher than that of un-coated Pd nanoparticles with no support (0.89 mA/cm
2
) and with carbon nanotube support (1.08 mA/cm
2
).
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