The Woodruff School

SUMMARY

A distinctive field in the coatings industry is the coating of porous media, with broad applications in paper, apparel, textile, electronics, bioengineering, filtration and energy sector. A primary industrial scale process that can be used to coat porous media in a fast and flexible manner is slot die extrusion. A major concern when coating porous media with a wetting fluid is fluid penetration into the substrate. Although some level of penetration is desirable to obtain specific material properties, inadequate or excessive fluid penetration can negatively affect the strength, functionality or performance of the resulting material. In spite of its apparent industrial importance, limited modeling and experimental work has been conducted to study fluid penetration into porous media during fabrication. The effects of processing parameters on the penetration depth, the effects of penetration on material quality, and the method to predict and control the penetration depth are not well understood. This dissertation is composed of two parts. Part I is an applied study for coating onto porous media. This part focuses on the first objective of this dissertation which is to elucidate clearly the feasibility, advantages and disadvantages of the direct coating method as a potential fabrication route for MEA. Specifically, a new MEA fabrication process based on directly coating membrane solution onto porous catalyzed GDL is first presented. Then, the quality and performance of the MEA samples are examined. Three important quality issues are studied, membrane uniformity, membrane penetration and annealing condition. All factors if not properly controlled can impact the performance of the fuel cell. The objective of Part II is to fundamentally understand the fluid penetration process and predict the penetration depth when directly coating porous media, using a comprehensive approach. Specifically, computational and analytical models for predicting the penetration depth will be developed and experiments will be conducted to validate the models. Based on these models, the relationship between processing parameters and final penetration depth will be analyzed, for both Newtonian and non-Newtonian fluids.

SUBJECT:	Ph.D. Dissertation Defense

BY:	Xiaoyu Ding

TIME:	Thursday, February 20, 2014, 9:00 a.m.

PLACE:	MARC Building, 431

TITLE:	Applied Study and Modeling of Penetration Depth for Slot Die Coating onto Porous Substrates

COMMITTEE:	Dr. Tequila Harris, Co-Chair (ME) Dr. Thomas Fuller, Co-Chair (CHBE) Dr. Marc Smith (ME) Dr. Victor Breedveld (CHBE) Dr. Yan Wang (ME)

SUMMARY A distinctive field in the coatings industry is the coating of porous media, with broad applications in paper, apparel, textile, electronics, bioengineering, filtration and energy sector. A primary industrial scale process that can be used to coat porous media in a fast and flexible manner is slot die extrusion. A major concern when coating porous media with a wetting fluid is fluid penetration into the substrate. Although some level of penetration is desirable to obtain specific material properties, inadequate or excessive fluid penetration can negatively affect the strength, functionality or performance of the resulting material. In spite of its apparent industrial importance, limited modeling and experimental work has been conducted to study fluid penetration into porous media during fabrication. The effects of processing parameters on the penetration depth, the effects of penetration on material quality, and the method to predict and control the penetration depth are not well understood. This dissertation is composed of two parts. Part I is an applied study for coating onto porous media. This part focuses on the first objective of this dissertation which is to elucidate clearly the feasibility, advantages and disadvantages of the direct coating method as a potential fabrication route for MEA. Specifically, a new MEA fabrication process based on directly coating membrane solution onto porous catalyzed GDL is first presented. Then, the quality and performance of the MEA samples are examined. Three important quality issues are studied, membrane uniformity, membrane penetration and annealing condition. All factors if not properly controlled can impact the performance of the fuel cell. The objective of Part II is to fundamentally understand the fluid penetration process and predict the penetration depth when directly coating porous media, using a comprehensive approach. Specifically, computational and analytical models for predicting the penetration depth will be developed and experiments will be conducted to validate the models. Based on these models, the relationship between processing parameters and final penetration depth will be analyzed, for both Newtonian and non-Newtonian fluids.