On the Interfacial Phase Growth and Vacancy Evolution during Accelerated Electromigration in Cu/Sn/Cu Microjoints

In this work, we integrate different computational tools based on multi-phase-field simulations to account for the evolution of morphologies and crystallographic defects of Cu/Sn/Cu sandwich interconnect structures that are widely used in three dimensional integrated circuits (3DICs). Specifically, this work accounts for diffusion-driven formation and disappearance of multiple intermetallic phases during accelerated electromigration and takes into account the non-equilibrium formation of vacancies due to electromigration. The work compares nucleation, growth, and coalescence of intermetallic layers during transient liquid phase bonding and virtual joint structure evolution subjected to accelerated electromigration conditions at different temperatures. The changes in the rate of dissolution of Cu from intermetallics and the differences in the evolution of intermetallic layers depending on whether they act as cathodes or anodes are accounted for and are compared favorably with experiments. The model considers non-equilibrium evolution of vacancies that form due to differences in couplings between diffusing atoms and electron flows. This work is significant as the point defect evolution in 3DIC solder joints during electromigration has deep implications to the formation and coalescence of voids that ultimately compromise the structural and functional integrity of the joints.NSF Grant No.CMMI-146225

Phase-Field Model of Silicon Carbide Growth During Isothermal Condition

Silicon carbide (SiC) emerges as a promising ceramic material for high-temperature structural applications, especially within the aerospace sector. The utilization of SiC-based ceramic matrix composites (CMCs) instead of superalloys in components like engine shrouds, combustors, and nozzles offers notable advantages, including a 25% improvement in fuel efficiency, over 10% enhanced thrust, and the capability to withstand up to 500$^{\circ}$C higher operating temperatures. Employing a CALPHAD-reinforced multi-phase-field model, our study delves into the evolution of the SiC layer under isothermal solidification conditions. By modeling the growth of SiC between liquid Si and solid C at 1450$^{\circ}$C, we compared results with experimental microstructures and quantitatively examined the evolution of SiC thickness over time. Efficient sampling across the entire model space mitigated uncertainty in high-temperature kinetic parameters, allowing us to predict a range of growth rates and morphologies for the SiC layer. The model accounts for parameter uncertainty stemming from limited experimental knowledge and successfully predicts relevant morphologies for the system. Experimental results validated the kinetic parameters of the simulations, offering valuable insights and potential constraints on the reaction kinetics. We further explored the significance of multi-phase-field model parameters on two key outputs, and found that the diffusion coefficient of liquid Si emerges as the most crucial parameter significantly impacting the SiC average layer thickness and grain count over time. This study provides valuable insights into the microstructure evolution of the Si-C binary system, offering pertinent information for the engineering of CMCs in industrial applications

New mechanistic insights into hepatoprotective activity of milk thistle and chicory quantified extract: The role of hepatic Farnesoid-X activated receptors

Objective: Farnesoid-X-activated receptors (FXR) are key modulators of liver regeneration. Milk thistle and Chicory are known as potent protective remedies in several liver disorders. The objective of this work was to examine the role of FXR in the hepato-healing properties of milk thistle (MTE) and chicory extracts (CE) in a rat model of acetaminophen-induced hepatotoxicity. Materials and Methods: Male Wistar rats were randomly divided into seven groups including control, vehicle, acetaminophen (500 mg/kg/day, oral), acetaminophen plus oral MTE 200 and 400 mg/kg/day, and acetaminophen plus oral CE 500 and 1000 /kg/day for 28 days. Liver function and histology as well as the pattern of hepatic FXR expression were assessed after 4 weeks. Results: Administration of acetaminophen was associated with a significant elevation of liver transaminase along with the architectural injuries. In contrast, chronic concomitant administration of both MTE and CE significantly restored the liver function and structural abnormality. The main molecular findings of the study revealed that the lower doses of both MTE and CE led to a marked upregulation of hepatic FXR expression. Conclusion: Discovery of the involvement of the nuclear modulating pathways in hepatoprotective activity of the extracts, providesa new mechanistic insight which needs further investigations