Radiation Absorption Mechanism in Nonvolatile MNOS Structure

The γ-ray radiation will speed up the discharge of the storedcharge in nonvolatile MNOS structure. The radiation absorptionmechanism to enhance the discharge is discussed. A direct radiationemission model from the interface traps distributing both in energylevel and in space is given. The theoretical results based on thismodel are in good agreement with experimental measurements.

Microwave-hydrothermal preparation of a graphene/hierarchy structure MnO_2 composite for a supercapacitor

Graphene/hierarchy structure manganese dioxide （GN/MnO2） composites were synthesized using a simple microwave-hydrothermal method. The properties of the prepared composites were analyzed using field emission scanning electron microscopy （FE-SEM）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and X-ray photoelectron spectroscopy （XPS） measurements. The electrochemical performances of the composites were analyzed using cyclic voltammetry, electrochemical impedance spectrometry （EIS）, and chronopotentiometry. The results showed that GN/MnO2 （10 wt% graphene） displayed a specific capacitance of 244 F/g at a current density of 100 mA/g. An excellent cyclic stability was obtained with a capacity retention of approximately 94.3% after 500 cycles in a 1 mol/L Li2SO4 solution. The improved electrochemical performance is attributed to the hierarchy structure of the manganese dioxide, which can enlarge the interface between the active materials and the electrolyte. The prepa- ration route provides a new approach for hierarchy structure graphene composites; this work could be readily extended to the preparation of other graphene-based composites with different structures for use in energy storage devices.

Urchin-like FeOOH hollow microspheres decorated with MnO_2 for enhanced supercapacitor performance

Ultrathin MnO_2 decorated hierarchical urchinlike FeOOH hollow micro-nanospheres have been designed and synthesized through a facile hydrothermal route.The microspheres are made of FeOOH nanofibers with a diameter of 10 nm.Due to the synergetic effect between the unique FeOOH hollow micro/nanostructures and ultrathin MnO_2 layer,the as-fabricated FeOOH@MnO_2 hybrid electrode exhibits a high specific capacitance of 1192 F g^（-1）at a current density of 1 A g^（-1）.It also reveals high rate capabilities and superior stability.Moreover,the asymmetric supercapacitor（ASC）assembled from the FeOOH@MnO_2 and the active carbon（AC）delivers a high energy density of 40.2 W h kg^（-1）at a power density of 0.78 kW kg^（-1）,and the energy density could remain 10.4 W h kg^（-1）under a condition of high power density of 11.7 kW kg^（-1）.

Preparation of MnO2-Al2O3 adsorbent with large specific surface area for fluoride removal

MnO2-Al2O3 （MOAO） binary nanocomposite with a 1：3 MnO2 to Al2O3 molar ratio was synthesized by impregnation technique using mesoporous alumina （MA） precursor. The MOAO product consisted of MA and amorphous MnO2. The manganese valence in MOAO was ＋4, indicative of MnO2 being coated on the surface of MA during the impregnation process. MOAO had a large specific surface area （385.266 m^2/g） and wormhole-like mesoporous structure. The average pore size, which could be precisely controlled over the range of 3.4-4.1 nm. The optimum removal of fluoride was obtained when the initial pH was in the range of 4-10. The defluorination efficiency of MOAO was far superior to that of MA when the initial fluoride concentration exceeded 40 mg/L. The large surface area and bimodal porous structure of MOAO after coating MnO2 may be responsible for the high removal efficiency in the defluorination process.

Flexible asymmetric supercapacitor based on MnO_2 honeycomb structure

A flexible asymmetric supercapacitor with high energy density was constructed by using a flexible substrate of carbonized silk-fabrics decorated with carbon nanotube, electroplating MnO2 nanosheets and dip-coating activated carbon powders as the positive and the negative electrodes, respectively. By controlling the electroplating time, the MnO2 nanosheets can be self-assembled to honeycomb structure and showed excellent electrochemical performance in 1 mol/L Na2SO4 electrolyte with SC950-EP30 performing the best. It exhibited a high specific capacitance（1110.85 F/g at a current density of 1 A/g based on the mass of MnO2） and superior rate capability（77.44% capacity retention from 1 A/g to 10 A/g）.Thus, the optimal asymmetric device assembled with this material as positive electrode can deliver a maximum energy density of 43.84 Wh/kg and a maximum power density of 6.62 kW/kg.