S3E11

Ajay B Harish

Jiawei Yang

Rana Faryad Ali

Abstract of Talk 1

Today, every major city in the world, from New York / Berlin / Delhi / Beijing is struggling to cope with air pollution. Today, pollution has become a global pandemic heading towards a catastrophe and is desperately calling for attention. All automotive emissions can be classified roughly as exhaust and non-exhaust emissions. In simple terms, exhaust emissions are those that are coming out of the tailpipe while everything else is characterized as non-exhaust emissions. Unlike exhaust emissions, these are much more difficult and trickier to measure, estimate, and control. Recent OECD reports show that more than 90% of the contribution to PM10 & PM2.5 particles (in California) are owing to non-exhaust emissions. In this talk, I will present my work on computational nanotribology that is aimed at understanding the particulate content produced by elastomeric tire compounds. I will present a non-traditional approach to modeling two-body abrasive wear due to the contact between elastomeric tire compounds and road surfaces. In this direction, the process of two-body abrasion between rubber and surface is modeled as a multiscale contact-fracture process. At the microscale, cracks are initiated and grow due to contact stresses. These initiated cracks at the microscale lead to macrocracks that grow as fatigue cracks over long periods resulting in substantial wear volume. This work is limited to modeling the phenomena at the microscale with potential for larger multiscale modeling.

Biosketch of Speaker 1

Abstract of Talk 1

Creases are ubiquitous in nature and our daily life. They are very often observed on the surfaces of soft, elastic materials such as rubbers, hydrogels, and biological tissues. Recent studies show that creases can form in these materials when the compression is applied to about 0.35. However, in our common sense, creases can not be observed in metals even when the compression is applied much larger. In this talk, I will present the numerical study and experiments to understand the underlying mechanics of crease formation in metals, where the degree of plasticity is found to play a central role in determining the critical strain of creases. Plasticity retards the formation of creases. This fact is further examined in hydrogels of plasticity.

Biosketch of Speaker 1

Abstract of Talk 3

We advanced the development of solution-phase approaches for the preparation of lithium niobate (LiNbO3) nanoparticles with an average, tunable size from 7 to 100 nm. This solution-phase process results in the formation of crystalline, uniform nanoparticles of LiNbO3 at a reaction temperature of 220 °C with an optimal reaction time of as short as 30 h. Advantages of these methods include the preparation of single-crystalline LiNbO3 nanoparticles without the need for further heat treatment or without the need for using an inert reaction atmosphere. The growth of these nanoparticles began with a controlled agglomeration of nuclei formed during a solvolysis step. The reactions subsequently underwent the processes of condensation, aggregation, and Ostwald ripening, which remained the dominant process during the further growth of the nanoparticles. These processes did produce single-crystalline nanoparticles of LiNbO3, suggesting an oriented attachment process. Average dimensions of the nanoparticles were tuned from 7 to ~100 nm by either increasing the reaction time or changing the concentration of the lithium salts used in the solvothermal process. The nanoparticles were also confirmed to be optically active for the second harmonic generation (SHG). These particles could enable further development of SHG based microscopy techniques.

Biosketch of Speaker 3