Materials

Composite Solid Electrolyte Containing Li+- Conducting Fibers

Li+-ion conductivities are greater than those achieved before. Improved composite solid polymer electrolytes (CSPEs) are being developed for use in lithium-ion power cells. The matrix components of these composites, like those of some prior CSPEs, are highmolecular- weight dielectric polymers [generally based on polyethylene oxide (PEO)]. The filler components of these composites are continuous, highly-Li+- conductive, inorganic fibers.

Posted in: Materials, Briefs

Read More >>

Making Activated Carbon by Wet Pressurized Pyrolysis

Thermomechanical instabilities and associated frequency instabilities are reduced. A wet pressurized pyrolysis (wet carbonization) process has been invented as a means of producing activated carbon from a wide variety of inedible biomass consisting principally of plant wastes. The principal intended use of this activated carbon is room-temperature adsorption of pollutant gases from cooled incinerator exhaust streams.

Posted in: Materials, Briefs

Read More >>

Perovskite Superlattices as Tunable Microwave Devices

Interfacial interactions between paraelectric materials induce quasi-ferroelectric behavior. Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters.

Posted in: Materials, Briefs

Read More >>

Reliability and Design Considerations for Long Life Using Mica Capacitors in High-Voltage Apps

Over the last 40 years, a series of misconceptions regarding mica capacitor applications has led novice users to consistently over- derate wound or rolled mica/ epoxy dielectric capacitors. Mica, K2A13(Si04)3, a complex aluminum silicate in dielectric form, has been successfully used for many years as an integral part of high- voltage (2KVDC to 50KVDC) capacitor manufacturing — particularly in the 50pF to 5μF value range. Mica has unrivaled physical and electrical properties in comparison to other capacitor dielectrics, especially ceramic. Mica is extremely stable. Capacitance will change only -2% at -54°C and to +3% at +125°C. Mica is an excellent insulator, and is resistant to high temperature, thermal shock, mechanical shock, and vibration.

Posted in: Materials, Briefs

Read More >>

Low-Power RIE of SiO2 in CHF3 To Obtain Steep Sidewalls

Process parameters are chosen carefully to minimize deleterious effects. A reactive-ion etching (RIE) process has been developed to enable the formation of holes with steep sidewalls in a layer of silicon dioxide that covers a silicon substrate. The holes in question are through the thickness of the SiO2 and are used to define silicon substrate areas to be etched or to be built upon through epitaxial deposition of silicon. The sidewalls of these holes are required to be vertical in order to ensure that the sidewalls of the holes to be etched in the substrate or the sidewalls of the epitaxial deposits, respectively, also turn out to be vertical.

Posted in: Materials, Briefs

Read More >>

Annealing Would Improve β" — Alumina Solid Electrolyte

The objective is to prevent a sudden reduction of ionic conductivity. A pre-operational annealing process is under investigation as a potential means of preventing a sudden reduction of ionic conductivity in a β"—alumina solid electrolyte (BASE) during use. On the basis of tests described below, the sudden reduction of ionic conductivity, followed by a slow recovery, has been found to occur during testing of the solid electrolyte and electrode components of an alkali metal thermal-to-electric converter (AMTEC) cell. This conductivity reduction may be observed quite infrequently; at lower operating temperatures, T<1,073 K, it is not usually observed at all, while at T=1,123–1,173 K, hundreds of hours may pass before conductivity reduction occurs. Only on tests running at higher operating temperatures for thousands of hours is this phenomenon regularly exhibited. The reduction of ionic conductivity would degrade the performance of an AMTEC cell. A pre-operational annealing process would help to sustain performance.

Posted in: Materials, Briefs

Read More >>

Mixed Conducting Electrodes for Better AMTEC Cells

These electrodes conduct both electrons and sodium cations. Electrode materials that exhibit mixed conductivity (that is, both electronic and ionic conductivity) have been investigated in a continuing effort to improve the performance of the alkali metal thermal-to-electric converter (AMTEC). These electrode materials are intended primarily for use on the cathode side of the sodium-ion-conducting solid electrolyte of a sodium-based AMTEC cell. They may also prove useful in sodium-sulfur batteries, which are under study for use in electric vehicles.

Posted in: Materials, Briefs

Read More >>