Impact of structure and flow-path on in situ synthesis of AlN: Dynamic microstructural evolution of Al-AlN-Si materials

Abstract

The Al-AlN-Si composites were prepared in the gas-in-liquid in situ synthesized flow-reaction-system, which was implemented by a powder metallurgy and reaction sintering route. The experimental results showed that Al-AlN50Si B material (prepared by ball-milling powders) and AlAlN-50Si M material (prepared by mixing powders) exhibited the semi-continuous Si structures and the isolated Si islands, respectively. Subsequently, the Al-AlN-50Si materials were selected as the model materials by phase identification and microstructure analysis. The dynamic microstructural evolution of Al-AlN-50Si materials was investigated using the computational fluid dynamics (CFD) method. Mathematical models and simulation results showed that the in situ synthesis of AlN was strongly influenced by the structure and the flowpath ((c g,N 2 /l g,N 2 )+(c s,AlN /l s,AlN )). The flow paths of Al-AlN-50Si B material were restricted by the semi-continuous Si. These Si structures can promote the formation of the strong turbulence with gradually weakened fluctuation, so that the in situ synthesis of AlN was interconnected and surrounded by an interpenetrating Si network. In contrast, the flow paths of AlAlN-50Si M material can easily pass through the isolated Si due to its mild turbulence with linear relationship. As a result, AlN was separated by the isolated Si and agglomerated in the matrix. Overall, the present work provides new insights into dynamic microstructural evolution in in situ reaction sintering systems.

Research on Static and Dynamic Characteristics of Gas-lubricated Microbearings for Microfluidic Devices

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“…Due to the continuous development of rotating machinery for high precision, miniaturization, low energy consumption and long life span. Aerodynamic microbearings are widely used owing to their advantages of simple structure, low friction resistance, no contamination and minimal temperature limitation in comparison with the oil-lubricated bearings and electromagnetic bearings [4][5][6][7]. In these microfluidic applications, the lubricating films between the journals and bearing pads usually become very small and are found to be even smaller than the molecular mean free path [8,9], and the continuum flow of Reynolds equation is no longer valid for describing the rarefied gas flow characteristics.…”

How Environmental Protection Motivation Influences on Residents’ Recycled Water Reuse Behaviors: A Case Study in Xi’an City

“…In the process of questionnaire design, researchers spent much time and energy finding existing questionnaires in this field or in related fields to improve the validity and reliability of the questionnaire [45][46][47][48]. Afterward, researchers referred to those questionnaires and then designed the questionnaire that was used in this study.…”

Thermo-Elasto-Hydrodynamic Characteristics Analysis of Journal Microbearing Lubricated with Rarefied Gas

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