Potentially high-performance
lithium metal cells in extreme high-temperature
electrochemical environments is a challenging but attractive battery
concept that requires stable and robust electrolytes to avoid severely
limiting lifetimes of the cells. Here, the properties of tailored
polyester and polycarbonate diols as the soft segments in polyurethanes
are investigated and electrochemically evaluated for use as solid
polymer electrolytes in lithium metal batteries. The polyurethanes
demonstrate high mechanical stability against deformation at low flow
rates and moreover at temperatures up above 100 °C, enabled by
the hard urethane segments. The results further indicate transferrable
ion transport properties of the pure polymers when incorporated as
the soft segments in the polyurethanes, offering designing opportunities
of the polyurethane by tuning the soft segment ratio and composition.
Long-term electrochemical cycling of polyurethane-containing cells
in lithium metal batteries at 80 °C proves the stability at elevated
temperatures as well as the compatibility with lithium metal with
stable cycling maintained after 2000 cycles.
A series of soluble, fully aromatic polyetherimides were prepared as candidate materials for optical coating applications. Most of the new polymer coatings possessed high transparency in the optical and near-infrared spectral regions at thicknesses ranging from 1 to 10 microns. The refractive indices obtained ranged from 1.60 to 1.80 at visible wavelengths, with the highest values generally being obtained near 400 nm followed by a gentle decline as wavelength increased to 700 nm and beyond. The refractive index values could be controlled by varying the dianhydride and diamine composition. All of the polyimides showed good thermal stability to 400°C and displayed glass transition temperatures above 220°C, making them excellent candidates for device applications where increased refractive index and high optical clarity are desired. The paper will discuss the preparation and physical and optical properties of the polymers and compare them to other high index coating systems.
Microelectromechanical systems (MEMS) device manufacturers today are faced with the challenge of protecting electronic circuitry and other sensitive device structures during deep silicon wet-etch processes. Etch processes of this nature require prolonged exposure of the device to harsh corrosive mixtures of aqueous acids and bases at higher than ambient temperatures. A need exists for a spin-applied polymeric coating to prevent the exposure of such circuitry against the corrosive etchants. The challenge exists in developing protective coatings that will not decompose or dissolve in the etchants during the etch process. Such coatings require superior adhesion to the substrate without destroying the sensitive features below. Brewer Science, Inc., has developed a multilayer coating system for basic etchants which is compatible with a variety of semiconductor materials and offers protection against concentrated potassium hydroxide (KOH) etchants at prolonged exposure times of more than 8 hours. In addition, a second multilayer coating system is being developed for use with strong hydrofluoric and other various mixed acid etchants (MAEs) for exposures of 30 minutes or longer. These materials are specifically designed to protect circuitry subjected to concentrated MAEs during the wafer thinning processes used by MEMS device manufacturers.
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