Colloquium - Samir Aouadi | Department of Physics

Colloquium - Samir Aouadi

Event Information
Event Date: 
Tuesday, January 28, 2014 - 3:30pm
Event Location: 
PHYS 104

Adaptive High Temperature Solid Lubricants: Review of Recent Progress

S.M.Aouadi

PHYS 104

Refreshments at 3:15 P.M.

Department of Materials Science and Engineering and Department of Physics, University of North Texas, Denton, TX 76207, USA

Abstract

Progress in design and explorations of hard coatings with high temperature adaptive behavior in tribological contacts is reviewed. When coupled with surface engineering strategies for high temperature contact thermal management, this progress opens a huge opportunity for adaptive coating applications on machine parts, where oils and coolants are being traditionally used. The discussed adaptive mechanisms include metal lubricant diffusion, environment assisted tribo-oxidation with a low melting point and easy to shear oxide formations, temperature and mechanically induced phase transitions in hexagonal solids. All of these can be combined in surface synergistic self-adaptive evolutions to cover operating temperature from room to 1000 ⁰C and in some cases reversibly self-adjust during temperature cycling. The review also highlights emerging surface adaptive mechanisms, where the advances with ab initio modeling of intrinsically layered solids points to new compositions for temperatures stable and easy to shear ceramic coatings. Also, load and temperature adaptive surfaces with arrays of compliant carbon and boron nitride nanotube materials infiltrated with solid lubricants. Many challenges are identified for the adaptive coating practical use expansions, including reversibility in the temperature cycling operations and contact thermal management. Approaches for adaptive regulation of coating thermal conductivity, heat flow, and thermal spike mitigations are discussed when using surface structure evolutions and phase transitions. The future progress is linked to the development of in situ exploration techniques, capable to identify surface adaptive chemistry and structure evolutions at different temperature regimes. When combined with the predictive modeling, such approaches can considerably accelerate adaptive coating developments. This is shown on examples of in situ Raman spectroscopy applied to transition metal nitride adaptive coatings. Conclusions are made for opportunities, strategies, and challenges to help future designs and practical realizations of high temperature adaptive hard coatings.

Informative talk for Physics Grad Students

3:30 P.M.

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