Optimizing diamond-like carbon coatings - From experimental era to artificial intelligence

Diamond-like carbon (DLC) coatings are widely used for numerous engineering applications due to their superior multi-functional properties. Deposition of good quality DLC is governed by energy per unit carbon atom or ion and plasma kinetics, which are independent parameters. Translating independent parameters to dependent parameters to produce a best DLC is subjected to deposition method, technology, and system configurations which may involve above 50 combinations of bias voltage, chamber pressure, deposition temperature, gas flow rate, etc. Hence DLC coatings are optimized to identify the best parameters which yield superior properties. This article covers DLC introduction, the role of independent parameters, translation of independent parameters to dependent parameters, and discussion of four generations of DLC optimization. The first-generation of DLC optimization experimentally optimizes the parameter-to-property relationship, and the second-generation describes multi-parameter optimization with a hybrid of experimental and statistical-based analytical methods. The third generation covers the optimization of DLC deposition parameters with a hybrid of statistical methods and artificial intelligence (AI) tools. The ongoing fourth generation not only performs multi-parameter and multi-property optimization but also use AI tools to predict DLC properties and performance with higher accuracy. It is expected that AI-driven DLC optimizations and progress in virtual synthesis of DLC will not only assist in resolving DLC challenges specific to emerging markets and complex environments, but will also become a pathway for DLC to enter a digital-twin era

A grey-fuzzy Taguchi approach for optimizing multi-objective properties of zirconium-containing diamond-like carbon coatings

[[abstract]]Metallic, diamond-like carbon (Me-DLC) coatings are widely used in the mold industry due to their excellent wear resistance. In this paper, zirconium-containing DLC (Zr-DLC) coatings are prepared using an unbalanced magnetron sputtering process. Factors that affect the wear resistance of coatings consist of friction coefficients, hardness and anti-sticking properties. This paper aims to develop a method that optimizes the multi-objective properties of Zr-DLC coatings. For statistical purposes, the experimental parameters for the Zr-DLC coatings were put in place with a L18(35) orthogonal array. In order to optimize these properties, a method combining the grey, fuzzy and Taguchi approaches was established. While using the developed grey-fuzzy Taguchi method (GFTM), the experimental results from four properties can be integrated into a performance index. A comparison of the integrated performance index between the initial and optimal conditions shows that the magnitude increases from 0.46 to 0.81. The gain for each property by the GFTM from the initial condition is reported as 35% positive

Design of High-Performance Surfaces for Controlling Phase Transformation

Controlling phase transformation has been of particular interest for the past several decades. The properties of a phase transformation interface have a direct correlation with the performance of the surface and control of this performance opens up numerous opportunities for applications in: efficient liquid condensers, steam power production, oil separation and distillation, ice resistant aircraft, and microelectronics cooling. Previous research has employed a variety of techniques to control phase transformation from selectively textured surfaces, interfacial free energy modified surfaces, and porous surfaces infused with lubricant. However, while many of these researchers have focused on the capability to induce phase transformation on these surfaces, there has been a lack of focus on the optimization of these processes. Furthermore, many of the prior technologies suffer from poor durability and lifespan longevity in their intended applications. These factors have combined to inhibit the widespread adoption of these technologies due to cost and logistical pitfalls. This dissertation presents a systematic method to design optimized surfaces to control phase transformation on a surface while simultaneously enhancing the durability of the surfaces to resist environmental damage. The first research chapter addresses condensation heat transfer surfaces, optimizing the interfacial heat transfer when condensing a liquid. Using thermodynamic analysis, we design parameters for the optimal surface conditions during condensation, identify surface treatments that have selectively tuned contact angle and hysteresis, and display quantifiable improvements. These novel design parameters go against prior trends in condensation and exhibit efficient condensation on hygrophilic surfaces by minimizing the hysteresis on a surface using amorphous thin films. The second research chapter then addresses boiling heat transfer, maximizing the capability and useability of a smooth surface. No previous study has effectively used smooth surface modifications for boiling due to the fragility of such surface modifiers. This novel surface coating, based on diamond-like carbon, demonstrates high temperature stability and simultaneously enhances the heat transfer rate and maximum capable heat transfer compared to an uncoated surface. In chapter 4, we then transition to examining icing performance and the ability to delay the onset of ice formation on a surface, typically referred to as frosting. There have been a multitude of studies that have developed anti-icing surfaces, though scalability and applicability have been varied with no clear use cases. We demonstrate a simple coating that inhibits ice formation in conditions far harsher than would be experienced in a real-life application. The facile coating can easily be tuned to the specific application and performance properties required for use. We then compare it to prior state of the art and prove a significant improvement under standardized test conditions. Lastly, the final chapter utilizes the learnings of diamond-like carbon in chapter 3 to develop a novel fluorinated diamond-like carbon that maintains a superhydrophobic state and resists high temperature and abrasion. Such a surface coating exhibits as a useful application for nucleate boiling cooling of microelectronics, the fluorinated surface can conduct the same amount of heat as an uncoated surface at about 20C lower temperature. This surface is also the first to demonstrate superhydrophobic capabilities in environments in excess of 500C. The work herein has identified the properties necessary to optimize phase transformation surfaces and developed coatings that conform to the optimized design and display the predicted enhancements.PHDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/168006/1/btobel_1.pd