We report a novel way of synthesizing graphene-carbon nanotube hybrid nanostructure as an anode for lithium (Li) ion batteries. For this, graphene was prepared by the solar exfoliation of graphite oxide, while multiwalled carbon nanotubes (MWNTs) were prepared by the chemical vapor deposition method. The graphene-MWNT hybrid nanostructure was synthesized by first modifying graphene surface using a cationic polyelectrolyte and MWNT surface with acid functionalization. The hybrid structure was obtained by homogeneous mixing of chemically modified graphene and MWNT constituents. This hybrid nanostructure exhibits higher specific capacity and cyclic stability. The strengthened electrostatic interaction between the positively charged surface of graphene sheets and the negatively charged surface of MWNTs prevents the restacking of graphene sheets that provides a highly accessible area and short diffusion path length for Li-ions. The higher electrical conductivity of MWNTs promotes an easier movement of the electrons within the electrode. The present synthesis scheme recommends a new pathway for large-scale production of novel hybrid carbon nanomaterials for energy storage applications and underlines the importance of preparation routes followed for synthesizing nanomaterials.

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This paper investigates the effect of high-intensity ultrasound on the breakage characteristics of particles suspended in water. A continuous sonicated flow experimental apparatus is used involving a 24 kHz horn type transducer and continuous in-line particle chord length measurement. The effects of sonication power (150-350 W) and temperature (10-50 degrees C) on the breakage characteristics are investigated. Higher breakage is favored at higher sonication power. An optimum temperature in the range tested is observed to exist between 25 degrees C and 37 degrees C. The acoustic cavitation field is influenced by temperature through a complex interplay of vapor pressure, surface tension and viscosity leading to the optimum observed in particle breakage. The efficiency of ultrasound energy conversion to particle breakage is calculated using calorimetry and found along with the net breakage efficiency to initially increase with temperature followed by a decrease after the optimum. It is found to be independent of input ultrasonic power. The effects of contact time is also investigated.

A new method to achieve long-range orientational order in symmetric diblock copolymer nanodomains through the alignment and chaining of superparamagnetic nanoparticles in a magnetic field is investigated computationally and theoretically. The effects of nanoparticle size, volume fraction, and magnetization strength are explored using the hybrid particle field (HPF) technique for particles that selectively segregate into one domain of a symmetric diblock copolymer assembly. A critical selectivity of the particles for one nanodomain is observed, above which strong alignment results and below which comparatively disordered structures are formed. The 2D simulations reveal that, for a given nanoparticle volume fraction, only a nanoparticle size commensurate with the block copolymer domain spacing yields well-aligned nanostructures. Nanoparticles significantly larger than the domain spacing break the symmetry of the lamellar phase and result in poor alignment, while high defect densities are observed for smaller particles owing to colloidal jamming within the preferred domains. Small field strengths produce a high degree of alignment in simulations, but as corroborated by scaling calculations, high magnetization strengths are required to lower the equilibrium defect density for such nematic–isotropic phase transitions in lamellar thin films. Simulations also elucidate a window of optimal nanoparticle volume fractions over which alignment is achieved. For low nanoparticle volume fractions, only local alignment is observed, while high volume fractions lead to an order–order phase transition from lamellae to a hexagonal phase.

High-intensity ultrasound, is sought as a means to break particles. A horn-type ultrasonic transducer is used to apply HIU into a suspension of alumina particles causing breakage to occur. The rate of particle breakage is monitored continuously via in-line laser-based particle chord length measurement. Kapur function analysis is used to arrive at the grinding kinetics under variations of ultrasonic power, particle loading, temperature of the suspension and particle size. The first Kapur function increases monotonically with increase in input ultrasonic power. Increasing temperature also increases the first Kapur function but an optimum in the range investigated (10-50 C) is observed near 25 C. An exponential relation is found for the variation of first Kapur function with particle size, this being unique to ultrasound-mediated particle breakage. The breakage mechanism is attributed mainly to particle abrasion. Different breakage mechanisms are observed at different temperatures.

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