Synthesis and characterization of carbon-coated cobalt ferrite nanoparticles

Cobalt ferrite nanoparticles（CFNPs） were prepared via a reverse micelle method. The CFNPs were subsequently coated with carbon shells by means of thermal chemical vapor deposition（TCVD）. In this process, acetylene gas（C2H2） was used as a carbon source and the coating was carried out for 1, 2, or 3 h at 750℃. The Ar/C2H2 ratio was 10：1. Heating during the TCVD process resulted in a NP core size that approached 30 nm; the thickness of the shell was less than 10 nm. The composition, structure, and morphology of the fabricated composites were characterized using X-ray diffraction, simultaneous thermal analysis, transmission electron microscopy, high-resolution transmission electron microscopy, and selected-area diffraction. A vibrating sample magnetometer was used to survey the samples＇ magnetic properties. The deposited carbon shell substantially affected the growth and magnetic properties of the CFNPs. Micro-Raman spectroscopy was used to study the carbon coating and revealed that the deposited carbon comprised graphite, multiwalled carbon nanotubes, and diamond-like carbon. With an increase in coating time, the intensity ratio between the amorphous and ordered peaks in the Raman spectra decreased, which indicated an increase in crystallite size.

Investigations on pool boiling critical heat flux, transient characteristics and bonding strength of heater wire with aqua based reduced graphene oxide nanofluids

In the present work, the pool boiling critical heat flux, transient heat transfer characteristics, and bonding strength of thin Ni-Cr wire with aqua based reduced graphene oxide(r GO) nanofluids are experimentally studied. Results indicate:(i) the critical heat flux(CHF) of 0.01, 0.05, 0.1, 0.2, and 0.3 g·L^(-1) concentrations of r GO-water nanofluids varies from 1.42 to 2.40 MW·m^(-2);(ii) the CHF remains same for the tested samples during transient heat transfer studies and(iii) a constant value of CHF upto 10 tests when the nanocoated Ni-Cr wire is tested with DI water and deterioration occurs beyond this which implies a chance of peel off of r GO layer below the critical coating thickness.

Numerical simulation of nanoparticle pattern fabricated by electrostatic spray deposition

Electrospray deposition （ESD） as a patterning method of nanoparticles deposited on a substrate has attracted much attention due to several advantages over other methods. However, obtaining an optimum ESD processing condition for nanoparticle pattern relies much on trial experiments because of the lack of reliable numerical simulation. In this study, the deposition characteristics of nanoparticle generated by electrospray were investigated by using a three-dimensional Lagrangian model. Three important process parameters, including solution dielectric constant, applied voltage and surface charge density on mask were considered by fixing the geometrical parameters of the ESD device. Simulation result showed that under the condition of without a mask, the spray diameter increases with increasing solvent dielectric constant, and higher applied voltage makes the spray area wider. Controllability of focusing by changing surface charge density on the mask was confirmed： higher surface charge density on the mask results in more focused deposition. Validity of the numerical simulation developed in this study was verified by comnarison with exoerimental data.

Morphological control of cadmium sulfide nanostructures by electrophoretic deposition

Thin films and one-dimensional CdS nanostructures were formed by electrophoretic deposition of nanoparticles with morphological control, Particles less than 1Ohm in diameter were prepared by a microwave assisted synthesis using trisodium citrate as capping agent. The particles were character- ized by UV-Vis spectrophotometry, dynamic light scattering, and X-ray diffraction. Nanoparticles in the resulting aqueous dispersion were electrodeposited without any further treatment on aluminum plates. The nanostructures consisted of thin films with surface roughness being tuned with the applied voltage. One-dimensional nanostructures were formed by varying the applied voltage and by changing the molar ratio of the precursors in the nanocrystal synthesis. These results illustrate two different mechanisms of electrophoretic deposition that lead to the formation of different nanostructures,

Advances in scalable gas-phase manufacturing and processing of nanostructured solids： A review

Although the gas-phase production of nanostructured solids has already been carried out in industry for decades, only in recentyears has research interest in this topic begun to increase. Nevertheless, despite the remarkable scientific progress made recently, many long-established processes are still used in industry. Scientific advancements can potentially lead to the improvement of existing industrial processes, but also to the development of completely new routes. This paper aims to review state-of-the-art synthesis and processing technologies, as well as the recent developments in academic research. Flame reactors that produce inorganic nanoparticles on industrial- and lab-scales are described, alongside a detailed overview of the different systems used for the production of carbon nanotubes and graphene. We discuss the problems of agglomeration and mixing of nanoparticles, which are strongly related to synthesis and processing. Finally, we focus on two promising processing techniques, namely nanoparticle fluidization and atomic layer deposition.

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.