Effect of Chemical Potential and Atomic-Scale Vibration of Nucleant Surface on Liquid Layering and Heterogeneous Nucleation

This study reveals the key role of chemical potential and atomic-scale vibration of the nucleant surface in dictating pre-nucleation liquid-layering and heterogenous nucleation. The effect of potential-well depth Dw and vibration strength $$\overline{\beta }_{{{\text{std}}}}$$ β ¯ std of the nucleant surface on the layering and nucleation was examined. We found that nucleants with larger Dw and smaller $$\overline{\beta }_{{{\text{std}}}}$$ β ¯ std induce more ordered pre-nucleation layers to enhance nucleation, and proposed that Dw and $$\overline{\beta }_{{{\text{std}}}}$$ β ¯ std shall be considered when searching for effective nucleants.

Grain size control for high-performance formamidinium-based perovskite solar cells via suppressing heterogenous nucleation

By introducing ED and TAP into precursor solution, homogeneous nucleation is encouraged to occur and films with large grain size and lower defect density were obtained.

Surface Heterogeneous Nucleation-Mediated Release of Beta-Carotene from Porous Silicon

We demonstrate that the release of a poorly soluble molecule from nanoporous carriers is a complex process that undergoes heterogeneous surface nucleation events even under significantly diluted release conditions, and that those events heavily affect the dynamics of release. Using beta-carotene and porous silicon as loaded molecule and carrier model, respectively, we show that the cargo easily nucleates at the pore surface during the release, forming micro- to macroscopic solid particles at the pores surface. These particles dissolve at a much slower pace, compared to the rate of dissolution of pure beta-carotene in the same solvent, and they negatively affect the reproducibility of the release experiments, possibly because their solubility depends on their size distribution. We propose to exploit this aspect to use release kinetics as a better alternative to the induction time method, and to thereby detect heterogenous nucleation during release experiments. In fact, release dynamics provide much higher sensitivity and reproducibility as they average over the entire sample surface instead of depending on statistical analysis over a small area to find clusters.

Effect of Mg–Ti Treatment on Nucleation Mechanism of TiN Inclusions and Ferrite

Large sizes of columnar crystals and TiN particles have a great influence on the surface quality of ferritic stainless steel. In the present paper, this study proposed to obtain fine-grained equiaxed structures by Mg–Ti treatment. Through the experiment happened in resistance furnace with argon protection, the refining effect of Mg–Ti addition on the microstructure and TiN particles were investigated, and the refinement mechanism was discussed from interface coherence theory. It was found that due to adding Mg and Ti into molten ferritic stainless steel, the equiaxed crystal ratio increased from 37% to 50%, and the size of TiN particles reduced at the same time. The lattice matching characteristics of MgAl2O4/TiN and TiN/δ-Fe were investigated by FIB-HRTEM. According to Bramfitt’s equation, the lattice misfit for (400)MgAl2O4∥(200)TiN and (200)TiN∥(110)δ-Fe was 5.02% and 4.41%, respectively, which were all belong to the effective nucleation range. It could be considered that MgO and MgAl2O4 formed in the molten steel promoted TiN nucleation easier to precipitate out with large quantities in the liquid phase. The TiN particles with more uniform distribution significantly enhanced the heterogenous nucleation of ferritic phase during initial solidification process base on the good lattice fitting condition. Finally the equiaxed crystal ratio of δ-Fe phase increased dramatically.

Biophysical and physiological processes causing oxygen loss from coral reefs

The microbialization of coral reefs predicts that microbial oxygen consumption will cause reef deoxygenation. Here we tested this hypothesis by analyzing reef microbial and primary producer oxygen metabolisms. Metagenomic data and in vitro incubations of bacteria with primary producer exudates showed that fleshy algae stimulate incomplete carbon oxidation metabolisms in heterotrophic bacteria. These metabolisms lead to increased cell sizes and abundances, resulting in bacteria consuming 10 times more oxygen than in coral incubations. Experiments probing the dissolved and gaseous oxygen with primary producers and bacteria together indicated the loss of oxygen through ebullition caused by heterogenous nucleation on algae surfaces. A model incorporating experimental production and loss rates predicted that microbes and ebullition can cause the loss of up to 67% of gross benthic oxygen production. This study indicates that microbial respiration and ebullition are increasingly relevant to reef deoxygenation as reefs become dominated by fleshy algae.

Optimization of Microstructure of the Low Alloy Structural Steel Using Rare Earth Metal (REM) Addition

A general trend in steelmaking industry is to increase strength, resistance to brittle fracture and fatigue properties of steel products at favorable price. Achieving fine-grained microstructure during austenite to ferrite transformation is a basic prerequisite to improve the mechanical properties. The desired transformation can be achieved in several ways one of which is the use of small non-metallic inclusions as heterogenous nucleation sites during solidification of steel. A great attention is focused on this concept in recent years. Rare earth metals are suitable for the formation of small inclusions similarly as in the case of conventional microalloying elements such as niobium, titanium, vanadium and other. Rare earth metals have a high affinity to oxygen and sulfur. The paper deals with the optimization of microstructure of 42CrMo4 low alloy structural steel used for machine parts exposed to higher stresses. The steel was alloyed with cerium in the form of mischmetal to achive fine-grained microstructure. Operational experiment was proposed and realized in accordance with results of laboratory experiment.