Preparation of polypyrrole-coated CuFe_2O_4 and their improved electrochemical performance as lithium-ion anodes

CuFe2O4 network,prepared via the electrostatic spray deposition technique,with high reversible capacity and long cycle lifetime for lithium ion battery anode material has been reported.The reversible capacity can be further enhanced by coating high electronic conductive polypyrrole（PPy）.At the current density of 100mA·g-1.Li/CuFe2O4 electrode delivers a reversible capacity of 842.9 mAh·g-1 while the reversible capacity of Li/PPy-coated CuFe2O4 electrode increases up to 1106.7 mAh-g’.A high capacity of 640.7 mAhg＂1 for the Li/PPy-coated CuFe2O4electrode is maintained in contrast of 398.9 mAh·g-1 for CuFe2O4 electrode after 60 cycles,which demonstrates good electrochemical performance of the composite due to the increase of electronic conductivity.The electrochemical impedance spectroscopy（EIS） further reveals that the Li/PPy-coated CuFe2O4 electrode has a lower charge transfer resistance than the Li/CuFe2C〉4 electrode.

Hydrogen Gas Sensors Based on Electrostatically Spray Deposited Nickel Oxide Thin Film Structures

A simple, low-cost, and home-built electrostatic spray deposition （ESD） system with the stable cone-jet mode was used to deposit nickel oxide （NiO） thin films on glass substrates kept at temperature of 400 ℃ as the primary precursor solution of 0.1 M concentration hydrated nickel chloride was dissolved in isopropyl alcohol. Electrical measurements showed that these films were of n-type conductivity while their resistance response to hydrogen flow in air ambient was varied by 2.81% with the rise and recovery time of 48 s and 40 s, respectively.

Numerical study of particle motion near a charged collector

The behavior of particles impacting the surface of a charged droplet involves adhesion, rebound, and submersion. In the present study, a numerical model for simulating particle impacts on charged droplets is presented that takes into account the various impact modes. With the droplet considered as a solid boundary, the criterion for rebounding is that the particle＇s impact angle is 〈85°. The simulated trajecto- ries of the particles are verified by comparing with experimental data for low-velocity particles to assess the reliability of the model. For impact angles 〉85°, particles undergo three distinct modes depending on normal impact velocities. The critical velocity of adhesion/rebound and rebound/submersion is used to identify the mode that the particles are undergoing. The criteria are also verified by comparing with ana- lytical data. The results show that the impact angle of particles increases with increasing Coulomb number and decreases dramatically with increasing Stokes number, both of which lead to a high probability for particle rebound.

Scalable gas-phase processes to create nanostructured particles

The properties of nanoparticles are often different from those of larger grains of the same solid material because of their very large specific surface area. This enables many novel applications, but properties such as agglomeration can also hinder their potential use. By creating nanostructured particles one can take optimum benefit from the desired properties while minimizing the adverse effects. We aim at developing high-precision routes for scalable production of nanostructured particles. Two gas-phase synthesis routes are explored. The first one - covering nanoparticles with a continuous layer - is carried out using atomic layer deposition in a fluidized bed. Through fluidization, the full surface area of the nanoparticles becomes available. With this process, particles can be coated with an ultra-thin film of constant and well-tunable thickness. For the second route - attaching nanoparticles to larger particles - a novel approach using electrostatic forces is demonstrated. The micron-sized particles are charged with one polarity using tribocharging. Using electrospraying, a spray of charged nanoparticles with opposite polarity is generated. Their charge prevents agglomeration, while it enhances efficient deposition at the surface of the host particle. While the proposed processes offer good potential for scale-up, further work is needed to realize large-scale processes.