Synthesis of high performance Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C cathode material by ultrasonic-assisted sol–gel method

A novel ultrasonic-assisted sol–gel method is proposed to prepare Li₃V₂(PO₄)₃/C cathode material. X-ray diffraction analyses show that both Li₃V₂(PO₄)₃/C(A) synthesized by the ultrasonic-assisted sol–gel method and Li₃V₂(PO₄)₃/C(B) synthesized by a traditional sol–gel method have monoclinic structure. Scanning electron microscopy images indicate that the Li₃V₂(PO₄)₃/C(A) composite has a more uniform morphology than that of the Li₃V₂(PO₄)₃/C(B) composite. In the voltage range of 3.0–4.3 V (vs. Li/Li⁺), the initial specific discharge capacities of the Li₃V₂(PO₄)₃/C(A) and Li₃V₂(PO₄)₃/C(B) samples are 129.8 and 125.9 mAh g⁻¹ at 1C rate (1C = 133 mA g⁻¹), respectively. Furthermore, at 2-C charge/10-C discharge rate, the specific discharge capacity of the Li₃V₂(PO₄)₃/C(A) composite retains 113.2 mAh g⁻¹ after 50 cycles, but the Li₃V₂(PO₄)₃/C(B) composite only presents a capacity of 94.8 mAh g⁻¹.     

In Situ Charge Characterization of TiO<Subscript>2</Subscript> and Cu–TiO<Subscript>2</Subscript> Nanoparticles in a Flame Aerosol Reactor

Charge distribution characteristics were investigated for nanoparticles synthesized in a diffusion flame aerosol reactor. The nanoparticles considered were pristine TiO₂ and Cu–TiO₂, with Cu dopant concentrations ranging from 1 to 5 wt% with particle size from 25 to 60 nm. In situ measurements were conducted by integrating a tandem differential mobility analyzer (TDMA) experimental setup with the flame aerosol reactor. A charging model was used to identify the important parameters that govern the two charging mechanisms (diffusion and thermo-ionization) in the flame and their relative importance at different operating parameters. The results indicate that TiO₂ and Cu–TiO₂ nanoparticles carry single as well as double unit charges. The charged fraction depends on particle size as well as on dopant concentration. The charged fraction increased with increasing particle size and decreased with copper dopant concentration. Measured charged fractions were similar for both the polarities at different mobility diameters. Based on the flame operating parameters, the calculations indicate that diffusion charging is dominant in the flame, which is consistent with the experimental results.     

Associated production of a KK-graviton with a Higgs boson via gluon fusion at the LHC

In order to solve the hierarchy problem, several extra-dimensional models have received considerable attention. We have considered a process where a Higgs boson is produced in association with a KK-graviton (G _KK) at the LHC. At the leading order, this process occurs through the gluon fusion mechanism gg→hG _KK via a quark loop. We compute the cross section and examine some features of this process in the ADD model. We find that the quark in the loop does not decouple in the large quark-mass limit just as in the case of gg→h process. We compute the cross section of this process for the case of the RS model also. We examine the feasibility of this process being observed at the LHC.     

A Cosmological Model with Static Extra Dimensions and Varying Cosmological Constant

A five dimensional cosmological model with FLRW type Kaluza-Klien metric has been investigated with static extra dimensions and varying cosmological constant. The field equations with static extra dimension are solved by considering the cosmological constant as a function of time for different cases. The effective pressure is considered as the difference of pressure corresponding to the extra dimension and the usual four dimensions. The conditions for acceleration of the universe are then discussed.     

Growth and equilibrium morphology of metal precipitates formed inside an oxide matrix

Metal precipitation occuring during internal reduction of various mixed oxides, such as magnesia or alumina, doped with more noble transition metal oxides, is investigated for different doping contents, reaction temperature and driving forces. The precipitate morphology developing inside the solid oxide matrix and the corresponding orientation relationships between the metal and the oxide phase are analysed by transmission electron microscopy. The evolution of precipitate shape across the reduction scale is interpreted in terms of ageing of the metal inclusions; the various morphologies identified are ascribed to different stages of nucleation, diffusional growth and final equilibration.Precipitate morphology is analysed in terms of diffusion-controlled growth of small metal particles in their local and long range diffusion field. The influence of interfacial energy and related anisotropy is experimentally demonstrated for selected examples. The general role played by these parameters during growth and final equilibration is also discussed. The implications of the elastic strain fields building up during growth of the metal inside the oxide matrix are analysed in view of our experimental results. Shape changes taking place during the growth process are considered to be controlled by local matter transport properties. The influence of the reaction mechanism at an atomic scale and the relative fit of the crystallographic lattices are briefly summarised.