Control over Multi-Scale Self-Organization-Based Processes under the Extreme Tribological Conditions of Cutting through the Application of Complex Adaptive Surface-Engineered Systems

This paper features a comprehensive analysis of various multiscale selforganization processes that occur during cutting. A thorough study of entropy production during friction has uncovered several channels of its reduction that can be achieved by various selforganization processes. These processes are (1) self-organization during physical vapor deposition PVD coating deposition on the cutting tool substrates; (2) tribofilm formation caused by interactions with the environment during operation, which consist of the following compounds: thermal barriers; Magnéli phase tribo-oxides with metallic properties at elevated temperatures, tribo-oxides that transform into a liquid phase at operating temperatures, and mixed action tribo-oxides that serve as thermal barriers/lubricants, and (3) multiscale selforganization processes that occur on the surface of the tool during cutting, which include chip formation, the generation of adhesive layers, and the buildup edge formation. In-depth knowledge of these processes can be used to significantly increase the wear resistance of the coated cutting tools. This can be achieved by the application of the latest generation of complex adaptive surface-engineered systems represented by several state-of-the-art adaptive nano-multilayer PVD coatings, as well as high entropy alloy coatings (HEAC)

Spatio-temporal behaviour of atomic-scale tribo-ceramic films in adaptive surface engineered nano-materials

Atomic-scale, tribo-ceramic films associated with dissipative structures formation are discovered under extreme frictional conditions which trigger self-organization. For the first time, we present an actual image of meta-stable protective tribo-ceramics within thicknesses of a few atomic layers. A mullite and sapphire structure predominates in these phases. They act as thermal barriers with an amazing energy soaking/ dissipating capacity. Less protective tribo-films cannot sustain in these severe conditions and rapidly wear out. Therefore, a functional hierarchy is established. The created tribo-films act in synergy, striving to better adapt themselves to external stimuli. Under a highly complex structure and non-equilibrium state, the upcoming generation of adaptive surface engineered nano-multilayer materials behaves like intelligent systems - capable of generating, with unprecedented efficiency, the necessary tribo-films to endure an increasingly severe environment

Thermal decomposition and fractal properties of sputter deposited platinum oxide thin films

Porous platinum thin films were prepared by thermal decomposition at temperatures from 25 to 675 C of platinum oxide films deposited by a pulsed reactive sputtering technique. The samples chemistry and structure were investigated by x ray diffraction XRD , x ray photoelectron spectroscopy XPS , and x ray absorption near edge structure XANES , showing that the decomposition of the oxide begins as low as 400 C and follows a sigmoidal trend with increasing annealing temperature. In the XRD spectra, only an amorphous like signature was observed for temperatures below 575 C, while Pt 4f XPS showed that the deposited oxide was a mixture of PtO2 and PtO. Pt L3 edge XANES and Pt 4f XPS spectra showed that the Pt concentration and electronic structure are predominant for temperatures equal to or above 575 C. The morphologies of the films were investigated by the area perimeter method from atomic force microscopy and scanning electron microscopy SEM images, indicating that the surfaces exhibit a combination of Euclidian and fractal characteristics. Moreover, the thermal evolution of these characteristics indicates the agglomeration of the grains in the film as observed by SE

Deep oxidation of methane on particles derived from YSZ-supported Pd-Pt-(O) coatings synthesized by pulsed filtered cathodic arc

Methane conversion tests were performed on Pd, PdOy, Pd0.6Pt0.4Oy and Pd0.4Pt0.6Oy thin films deposited on yttria stabilized zirconia (YSZ) substrates. Pt containing films exhibited poor activity and high reducibility. As-deposited Pd and PdOy films showed good activity and transformed, during the cycling process, to particles dispersed on the YSZ substrates. The higher reaction rate of initially PdOy films was explained by a better dispersion of the catalyst. A drop of the reaction rate was observed when the temperature exceeded 735oC and 725oC for initially Pd and PdOy, respectively, which can be associated with the high-temperature reduction of PdO into Pd