Narrow Results

The kinetics of the Ostwald ripening in a homogeneous supersaturated solution is studied both numerically and analytically. The time evolution of the grain-size distribution function in a new phase is theoretically described, taking into account the finite value of the maximal size of a grain. Two situations are considered: the kinetics of grain growth is controlled either by the grain-monomer reaction process (an early stage) or by the monomer diffusion process (a late stage). A transition to the final distribution is shown to take place through an intermediate-asymptotical mode of the Ostwald ripening kinetics, the crossover of the kinetic indices is demonstrated, and the duration of intermediate stage is evaluated.

The complex interactions of two and three spark-generated bubbles are studied using high speed photography. The corresponding simulations are performed using a 3D Boundary Element Method (BEM) code. The bubbles generated are between 3 to 5 mm in radius, and they are either in-phase or out-of-phase with one another. The possible interaction phenomena between two identically sized bubbles are summarized. Depending on their relative distances and phase differences, they can coalesce, jet towards or away from one another, split into smaller bubbles, or 'catapult' away from one another. The 'catapult' effect can be utilized to generated high speed jet in the absence of a solid boundary or shockwave. Also three bubble interactions are highlighted. Complicated phenomena such as bubble forming an elliptical shape and bubble splitting are observed. The BEM simulations provide insight into the physics of the phenomena by providing details such as detailed bubble shape changes (experimental observations are limited by the temporal and spatial resolution), and jet velocity. It is noted that the well-tested BEM code [1,2] utilized here is computationally very efficient as compared to other full-domain methods since only the bubble surface is meshed.

The droplet coalescence phenomenon extensively exists in the industrial production and application, as well as in nature, which is of great research significance. This paper adopted the molecular dynamics (MDs) simulation method to investigate the behavioral characteristics of water/water, ethanol/ethanol and water/ethanol nanodroplets coalescence. The results suggested that, in water and ethanol nanodroplet coalescence process within the water/ethanol system, ethanol was always wrapped on the outer layer of water droplets. The droplet shrinkage in the water/water system was greater than those in the other two systems; meanwhile, that in the water/ethanol system rapidly increased after the contact of droplets, and subsequently surpassed that in the ethanol/ethanol system.

The coalescence of particles extensively exists in the industrial production and nature, which is of great research significance. This paper examined the alloying process of Cu/Au nanoparticles with different sizes by molecular dynamics (MDs) simulations. The coalescence process presents three stages which can be divided by the contact and fusion. The alloying processes of Cu/Au nanoparticles with different sizes had contacted with each other before the heating at 300 K. The Au atoms diffused through the outer area of the sintering neck before the nanoparticles were fused into one particle. The coalescence had become severe after the systems reached the melting temperature. The different systems showed different sintering rate.

With the popularization of 3D printing technology, micro/nanoparticles sintering technology has drawn lots of attentions all over the world. Here, molecular dynamic simulation is employed to discuss the effects of different interfacial lattice structures, different diameter of nanoparticles, and different heating rates on the coalescence of metallic Cu nanoparticles. The results showed that the diameter of nanoparticles determine the melting point of the system. Besides, the interfacial lattice structure, diameter of nanoparticles, and heating rate have an influence on the initial sintering temperature. This is because the melting point is the inherent property of material which relies on the mass of substance. However, the initial sintering temperature is sensitive to many factors, including the temperature, interfacial, and intermolecular interactions.