Lutgard C. DeJonghe

Transport Property Measurements of Polymer Electrolytes

Abstract Straightforward electrochemical methods for determining the transport properties (bulk ionic conductivity, salt diffusion coefficient, and cation transference number) of polymer electrolytes are described herein. The new technique for measuring t 0 + is based on concentrated solution theory, and requires no assumptions to be made concerning ideality of the solution. The experimental methods are described and results on representative polymer electrolyte systems are presented in this paper. Cation transference numbers are found to be salt-concentration dependent and considerably less than unity or even negative over a wide concentration range. This implies that the cationic current is mainly carried by complexed ions. The presence of associated ionic species in the present systems is confirmed by Raman spectroscopic evidence. Finally, the practical effects of a negative t 0 + on cell operation and implications for device design are discussed.

Wear Behavior of Ceramic Sliders in Sliding Contact with Rigid Magnetic Thin-Film Disks

This study identifies factors that affect slider performance and reports the effect of the nature of slider materials on wear behavior. Three factors relating to wear behavior are discussed: slider shape, wear data reproducibility and patterns of wear behavior. First, the performance of various sliders shows a strong correlation to the slider crown shape. Second, wear behavior is more reproducible when unlubricated disks replace lubricated disks. With lubricated thin-film disks, slider failure is reasonably reproducible, but when the failure occurs it is erratic. Although unlubricated disks show more reproducible wear data, the wear life of the disks is roughly an order of magnitude shorter than lubricated disks. It is important to recognize these factors before evaluating material differences in slider performance. Finally, multi-phase slider materials have more variation in failure patterns than single-phase slider materials; the difference is attributed to more flaws present in the multi-phase material...

Cathode Contact Materials for Solid Oxide Fuel Cells

Cathode contact paste materials (CCM) are typically used to bond the SOFC to the interconnect plate, and provide electrical connection between the two. The use of stainless steel interconnects limits the processing of SOFC stacks in air to 1000°C or lower. At this temperature, many typical SOFC cathode compositions display only minimal sintering and bonding, limiting their use as CCM. The goal of this work is to screen a wide variety of candidate CCM materials and bonding aids to identify compositions that provide adequate bonding and electrical conductivity after sintering at 900-1000°C.