Nanoscale Exploratory Research: Dispersion of Nanopowders in Solidifying Molten Metals and Formation of High-Strength Nano-Composite Solders

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This Nanoscale Exploratory Research (NER) project is an exploratory study aimed at understanding the key physical mechanisms governing the dispersion of nano-particles in molten metals and the concomitant solidification of the nano-particle-reinforced molten metals resulting in the formation of nano-particle reinforced composite solders having attractive combinations of strength, durability and reliability. Carefully orchestrated and planned experiments will be performed to produce nano-particle reinforced composite solders based on commercial tin-lead and lead-free solder mixtures blended well with nanopowders. In the first phase of this research nanopowders of copper, iron, molybdenum and nickel will be chosen and in the follow phase nanopowders of titanium dioxide and aluminum oxide will be the candidates. Innovative techniques will be developed after several trial and error experimentation to establish an efficient means for blending the nano-powders with the micron-size powders of the solder resulting in a molten solder mixture having a near uniform dispersion of nanoparticles. Quantitative measurements will be conducted to characterize the dynamics of solidification of the composite molten solder mixture. Metallurgical observations using both optical microscopy and scanning electron microscopy will be made to characterize the nature, morphology and distribution of intrinsic microstructural features and the presence and distribution of artifacts such as micro and macro porosity, voids and microscopic cracks. Mechanical tests, to include microhardness, tensile deformation and cyclic fatigue, will be conducted to demonstrate the overall superiority combination of mechanical properties of the nano-particle reinforced composite solders. It is anticipated that the findings of this research study will provide a viable solution to engineering high strength materials by adding trace amounts of nanopowders into a solidifying molten metal to form nano-particle reinforced composite. The engineered composite solders will have attractive combinations of strength; damage tolerance and durability coupled with improved reliability thereby enhancing the probability of its use on in a spectrum of microelectronic and opto-electronic devices and assemblies. Results of this research exercise will also have far reaching consequences beyond soldering materials. It is expected that the study would also shed light on several fundamental issues related to the formation of nanoparticle-reinforced metallic and even non-metallic composites. A study of the influence of nano-particles on crystalline nucleation kinetics and microstructural development will contribute to enhancing our understanding of modern solidification theory.