查看更多>>摘要：The promising candidates for high-performance electrode materials, transition metal species@N-doped mesoporous carbon composites (M/MO/M(OH)_2@NDMCs), were synthesized by carbonization of metal ion-doped polyaniline (PANI) functionalized mesoporous silica SBA-15, followed by etching the mesoporous silica template. The yielded M/MO/M(OH)_2@NDMC can be further converted into sulfide via a simple hy-drothermal sulfidization treatment. The mesoporous structure, large amount of the accessible electro-chemically active nitrogen species, partially graphitic structure, and transition metal compounds of transition metal species@NDMC composites will increase the electronic and ionic conductivity by reducing the internal and ion diffusion resistances resulting in fast diffusion of ions in the electrolyte to the electrode surface. These endowed them good electrochemical performance characteristics for use in supercapacitor electrodes. Correspondingly, NiO/Ni(OH)_2@NDMC, Co/Co(OH)_2@NDMC, and CoS_2@NDMC as the electrodes in 2 M KOH showed specific capacitance of 337, 589, and 1178 F g~(-1) at 2.0 A g~(-1), respectively. Furthermore, the assembled asymmetric supercapacitor device utilizing CoS_2@NDMC as a cathode exhibited a satisfactory energy storage capability (50 Wh kg~(-1) at 750 W kg~(-1)) with an admirable cyclic life (retaining -99% initial capacitance over 6000 repeated cycles). This finding gives these transition metal species@NDMC composites, especially CoS_2@NDMC, prospective applications as high-performance supercapacitor electrode materials, where a fast charge/discharge is required.
查看更多>>摘要：In this study, solvothermal method was adopted to successfully prepare graphene oxide (GO) supported SnO_2 nanocomposites using tin tetrachloride pentahydrate and graphene oxide as raw materials, tetra-methyl ammonium hydroxide (TMAH) as a control agent. The synthetic materials presented the efficient capacity in the photocatalytic degradation and photoelectric conversion. In the photocatalytic degradation of rhodamine B (RB) and methylene blue (MB), sample SnO_2-0.1% GO showed the optimal photocatalytic efficiencies for RB (97.26%) and MB (89.43%) degradation. According to the different degradation performances of RB and MB functional groups, we reasonably explained the electron transfer mechanism at the interface of SnO_2-GO nanomaterials, and verified it in the experiment of photoelectric conversion proceed combined with titanium dioxide nanotube arrays (TiO_2NTs). The enhanced photocurrent density and stability can also be effectively improved due to the effective photoelectron transfer from SnO_2 to GO surface.
查看更多>>摘要：The construction of Fe_2O_3/Fe_2TiO_5 heterostructure has been proven as an effective strategy to improve the photoconversion efficiency of hematite, however its controllable synthesis is still a great challenge. In this study, by performing a comparative investigation on two distinct Ti precursors, a novel, convenient, and low-cost approach for fabricating efficient Fe_2O_3/Fe_2TiO_5 photoanodes is developed. It clearly demonstrates that the adoption of typical TiCl_4 precursor leads to a Fe_2O_3/TiO_2 composite with a lower PEC activity, while a core-shell Fe_2O_3/Fe_2TiO_5 heterostructure is built via using the stable and water-soluble peroxo-titanium complex (PTC) precursor. The as-fabricated photoanode exhibits a comparable photocurrent density of 2.51 mA/cm~2 at 1.23 V vs. RHE to most of Fe_2O_3/Fe_2TiO_5 photoanodes in literatures. Based on various characterizations, the significant enhancement in PEC performance can be attributed to the largely increased donor density and the formation of Fe_2O_3/Fe_2TiO_5 core-shell heterostructure, which effectively facilitate the charge separation and transport in the bulk and surface of photoanode. This work provides a new idea for fabricating high-efficient Fe_2O_3/Fe_2TiO_5 photoanodes.
查看更多>>摘要：Crystal structures, electronic, and magnetic properties of RbCeX_2 (X = S, Se, Te) crystals are investigated using periodic density functional theory (DFT) calculations under hydrostatic pressures up to 10 GPa. The ferromagnetic phase is slightly more stable than the anti-ferromagnetic one for all compounds and pressures. A pressure-induced transition from a magnetic semiconductor (MS) to a spin gapless semiconductor (SGS) is observed only in the case of the X = Te compound. In absence of imposed pressure, the X = Te exhibits a direct a-spin gap of 0.46 eV while its β-gap is 2.30 eV. A pressure of 10 GPa completely suppresses the a-spin gap of RbCeTe_2 and reduces it β-gap to 1.63 eV. This pressure-induced elimination of only one spin gaps is exclusive to the X = Te compound. This property distinguishes the Te compound from its two congeners. The pressure-response characteristics of RbCeTe_2 renders this compound a potential pressure-induced MS → SGS switching material.
查看更多>>摘要：In this study, the nickel oxide (NiO_x) thin films were reactively sputtered at different working pressures in the oxide mode zone for application in flexible all-thin-film electrochromic devices (ATF-ECDs). The working pressure plays an important role on the various properties of the reactively sputtered NiO_x thin film including the deposition rate, grain structure (microstructure), morphology, chemical composition, optical properties and electrochemical properties. The flexible ATF-ECDs with ≥2 Pa NiO_x thin films perform high optical modulation and relatively fast response time during the electrochromic processes. The detailed electrochromic mechanism is discussed.
查看更多>>摘要：To explore the influence of sintering temperature on mechanical properties of Al_2TiO_5 (AT) flexible ceramics, the XRD/Raman, SEM and acoustic emission (AE) technology were used to estimate the phase composition, microstructure evolution and damage behaviors of AT ceramics, respectively. Results show that the diffraction peaks of AT increase before rising sintering temperature from 1300 °C to 1500 °C and then start to decrease at 1600 °C due to the decomposition of AT grains. In specimens with sintering temperature of 1300 °C and 1400 °C, intergranular fractures are more likely to occur, which controls the origination of AE events in the whole stage. And the fracture of big bodies composed by large number of fine AT grains is the main source of AE events with high energy level at initial stage. In addition, Thanks to the more trans-granular fracture in specimens with sintering temperature of 1500 °C and 1600 °C, the number of AE events in these two specimens are more than that of specimens with sintering temperature of 1300 °C and 1400 °C.
查看更多>>摘要：Antiferromagnetic pyrite compound MnTe_2 is a newly discovered high-performance thermoelectric material. However, its electric and thermal transport performance remained unexplored so far. In this work, the first-principle calculations based on the density functional theory were applied to predict the electric and thermal transport performance of MnTe_2. The band structures showed that Te atoms dominate the band energies near the fermi level. The calculated electric transport performance of MnTe_2 from BoltzTraP2 package showed that n-type MnTe_2 possesses a higher power factor than that of p-type in the carrier concentration range from 10~(19) to 10~(21) cm~(-3). The peak power factor with electronic relaxation time of n-type MnTe_2 at 800 K is 3.05 x 10~(15) μW K~2 cm~(-1) s~(-1) at a lower carrier concentration of 0.78 × 10~(21) cm~(-3) while p-type is 2.18 × 10~(15) μW K~(-2) cm~(-1) s~(-1) at a higher carrier concentration of 1.35 × 10~(21) cm~(-3) It suggests that high-performance n-type doped MnTe_2 is easier to be obtained experimentally. Due to the low average phonon velocity of 2064 m-s~(-1), MnTe_2 has a low lattice thermal conductivity of 0.72 W m~(-1) K~(-1) at 800 K. The calculated charged point defect formation energy of several possible n-type doping elements showed that Y or La substituting Mn atom and Cl or Br substituting Te atom are the most possible n-type doping point defects. Combined with the optimal carrier concentration of 0.78 x 10~(21) cm~(-3)at 800 K, stoichiometric A_(0.07)Mn_(0.93)Te_2 (A = Y, La) and MnTe-1.93B0.07 (B = Cl, Br) are expected to possess high thermoelectric properties reaching the theoretical peak power factor with electronic relaxation time of 3.05× 10~(15) μW K~(-2) cm~(-1) s~(-1) and the lattice thermal conductivity of 0.72 W m~(-1) K~(-1).
查看更多>>摘要：By the exploitation of doping in semiconductor photocatalysts, the energy band structure adjustment would induce the improvement of solar absorption and photochemical performance. Here, we investigated the N/F codoped TiO_2 nanotube arrays (TiO_2 NTs) by tuning the preparation operation sequence of sol-vothermal doping and annealing treatment. The optimized Sample 1 prepared by the first solvothermal doping in ethanol and then annealing exhibited the outstanding solar absorption, low electron-hole recombination and photoelectrochemical performances. The excellent photocatalytic performances in pho-tocurrent/H_2 generation and pollutant removal were discussed and analyzed in detail. Furthermore, we explained the mechanism of N/F codoping for improved photocatalytic performances. The work gives a referable template for improved photocatalytic application fields of TiO_2 in environment and energy.
Ismayadi IsmailMuhammad Misbah Muhammad ZulkimiRaba'ah Syahidah Azis
7页
查看更多>>摘要：In the present work, substitution of strontium U-type hexaferrite with the composition of Sr_4Mn_(2-x)Zn_xFe_(36)O_(60) (x= 0.5,0.6,0.8, and 1.0) was prepared via high energy ball milling (HEBM) and sintered at 1100 °C. The phase, microstructure, magnetic, dielectric and electromagnetic wave absorbing properties of U-type strontium hexaferrite composites were measured using XRD, FESEM, and Vector Network Analyzer in the frequency range of 8-18 GHz (X-band and Ku-band). MnZn doping was found to shift the natural resonance of the materials by affecting its magnetocrystalline anisotropy. The reflection loss (RL) indicated that the composite possessed good microwave-absorbing properties with U-type strontium hexaferrite ( Sr_4Mn_(2-x)Zn_xFe_(36)O_(60)) of x = 0.8 resulted in high minimum RL value for all thickness of 1 mm and two peaks at approximately - 32.50 and - 41.50 dB at 14.00 and 15.60 GHz, with bandwidth of 0.60 and 0.80 GHz for losses less than - 10 dB.
查看更多>>摘要：Electron backscatter diffraction (EBSD) was applied to investigate the superplastic behavior of a fine-grain Al-Mg-Li alloy. It was found that microstructural changes were noticeably influenced by the occurrence of continuous dynamic recrystallization. This mechanism involved a transverse subdivision of pre-elongated grains which eventually transformed into chains of nearly-equiaxed grains. A body of experimental observations, including extensive strain hardening, marked grain elongation, the formation of pronounced substructure in interior regions of grains, and the development of crystallographic texture, provided strong evidence of large amounts of intragranular slip operating during superplastic flow.
NSTL
Elsevier