Dispersion Behavior Of Nanoparticles Research Articles

Molecular dynamics study on the adsorption synergy of MWCNTs/MoS2 nanofluids and its influence of internal-cooling grinding surface integrity

The combination of nanofluids and internal-cooling grinding was applied in machining super-alloy to solve the problem of insufficient heat transfer and lubrication, thereby improving the surface integrity. In this paper, molecular dynamics method was utilized to calculate the interaction energy and mean square displacement (MSD), and the adsorption or dispersion behavior of nanoparticles (MWCNTs, MoS2) and ionic liquid ([EMIm]BF4) in the base fluid (H2O) was revealing. The centroid distance and the dynamic images indicated that the dispersion distance of 4 wt% [EMIm]BF4-MWCNTs reaches 105.37 Å, which is the optimal ratio. In the adsorption of MWCNTs and MoS2, it was observed that the two kinds of nanoparticles formed a pressure-bearing sandwich structure, which can synergistically enhance heat transfer and lubrication. Raman spectroscopy affirmed the modification effect of ionic liquids. Nanoparticle size and contact angle tests indicated that the optimized nanofluid has excellent dispersion and film-forming properties. In addition, nanofluids were applied to the grinding process through a pressurized internal-cooling grinding wheel. Compared with the conventional coolant, the grinding temperature of the optimized nanofluid is reduced by 9.28% and 12.89%, and the surface roughness on the workpiece is reduced by 21.34% and 23.73%, which effectively lessens the furrow and burrs.

The role of ultrasonic cavitation in refining the microstructure of aluminum based nanocomposites during the solidification process

Recent studies showed that the microstructure and mechanical properties of aluminum based nanocomposites can be significantly improved when ultrasonic cavitation and solidification processing is used. This is because ultrasonic cavitation processing plays an important role not only in degassing and dispersion of the nanoparticles, but also in breaking up the dendritic grains and refining the as-cast microstructure.In the present study, A356 alloy and Al2O3 nanoparticles are used as the matrix alloy and the reinforcement, respectively. Nanoparticles were added into the molten A356 alloy and dispersed via ultrasonic cavitation processing. Ultrasonic cavitation was applied over various temperature ranges during molten alloy cooling and solidification to investigate the grain structure formation and the nanoparticle dispersion behavior. Optical Microscopy and Scanning Electron Microscopy were used to investigate in detail the differences in the microstructure characteristics and the nanoparticle distribution. Experimental results indicated that the ultrasonic cavitation processing and Al2O3 nanoparticles play an important role for microstructure refinement. In addition, it was shown in this study that the Al2O3 nanoparticles modified the eutectic phase.

Crystallization, dispersion behavior and the induced properties through forming a controllable network in the crosslinked polyester‐SiO2 nanocomposites

AbstractThe poly(ethylene terephthalate) (PET) crosslinked copolymers (G‐PET) with glycerol (GC) and their novel nanocomposite samples (GNPET) were reported and investigated. The nanoparticle dispersion behavior was creatively stabilized with the crosslinked network. Several interesting properties and phenomena including the abnormal crystallization behavior of GNPET samples were presented. Results of differential scanning calorimeter proved that the thermal and crystallization behavior of GNPET samples was effectively tuned with GC load. The obviously enhanced crystallization and nanoparticle homogenous dispersion behavior appeared at 2 wt % SiO2 and 0.2 wt % GC load. Polarized optical microscopy (POM) results showed that the spherulite growth rate of the GNPET samples with 0.1 wt % GC load sharply decreased from 0.0562 to 0.0157 μm s−1 with 0.5 wt % GC load. As GC load increased, the spherulite size of GNPET samples decreased greatly so as to be much smaller than that of pure PET nanocomposites. Water absorbing experiments presented that the higher GC load created the lower water diffusion behavior but higher barrier against water, gas, and light. A model was proposed to state the network immobilization effect on the nanoparticle dispersion, and the restraining effect on PET chain mobility and crystal size growth which were related to the above properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Preparation of poly(ethylene glycol)-grafted silica nanoparticles using a facile esterification condensation method

Organic–inorganic hybrid nanoparticles have been prepared by the direct facile esterification condensation under extremely mild conditions as ambient temperature, moisture and atmospheric pressure, and the resulting composite particles are characterized by ESCA, FTIR, TEM, DLS, TGA, DSC, and XRD techniques. Results show that this facile graft method has high graft efficiency and the grafted poly(ethylene glycol) (PEG) accounts for about 55 wt% of the total silica composites. The resulting silica nanoparticles have core-shell structure with PEG on the outside and SiO2 in the core. As a result, the dispersion behavior of nanoparticles and the thermal stability of the grafted PEG are improved by the formation of covalent ester bonds between PEG and the reactive silica nanoparticles. The PEG phase, however, is disturbed by the proximity of the oxide phase of SiO2. Consequently, less crystal or faulty crystal of PEG is resulted when PEG is grafted onto the surfaces of silica nanoparticles.

Ｆｌａｓｈ Ｃｒｅａｔｉｏｎ法により合成した酸化物および複合ナノ粒子の微構造と界面特性

Dispersion behavior of nanoparticles in organic solvent depends on surface molecular structure, even if the material and size of particles are same. In order to discuss the effect of surface conditions of nanoparticles on dispersion behavior in organic solvent and surface modification behavior, single phase SiO2 and TiO2 nanoparticles and SiO2-TiO2 composite particles were prepared by using flash creation method (FC method) with different thermal source, DC plasma or burner. By the observation of TiO2-SiO2 composite particles by TEM-EDS system, the microstructure of composite particles was estimated that SiO2 layer coated on core TiO2 nanoparticles. Surface OH group structure, dispersion behavior in N-methyl-2-pyrrolidone (NMP) of each TiO2 nanoparticles was depended on the thermal source of FC method. When thermal source used was burner, the high OH group density and well dispersion behavior was observed. However, after surface modification by silane coupling agent, the aggregate size of TiO2 nanoparticles prepared by DC plasma in NMP was decreased.

Evaluation and Control of Aggregation and Dispersion Behavior of Nanoparticles and Its Applications

Evaluation and Control of Aggregation and Dispersion Behavior of Nanoparticles and Its Applications