Capacitors, molecular electronic materials

Sulfur hexafluoride [2551-62-4] 6 molecular weight 146.07, is a colorless, odorless, tasteless gas. It is not flammable and not particularly reactive. Its high chemical stabiUty and excellent electrical characteristics have led to widespread use in various kinds of electrical and electronic equipment such as circuit breakers, capacitors, transformers, microwave components, etc (see Electronic materials). Other properties of the gas have led to limited usage in a variety of unique appHcations ranging from medical appHcations to space research. 

Udo Merker, Ph.D., studied physics at the University of Bonn (Germany) from 1989 to 1994. He received his Ph.D. in 1998 for studies in molecular spectroscopy at the University of Bonn and Princeton University (New Jersey). From 1998 to 1999, Dr. Merker was a postdoctorate at the Chemistry Department of Princeton University. In 1999, he joined the corporate research division of Bayer AG to work on the development of electronic materials. From 2002 until 2008, Dr. Merker was responsible for the development of new materials and processes for electrolyhc capacitors in the central R D division of H.C. Starck GmbH. Since 2009, he has been the head of the application technology group of H.C. Starck Clevios GmbH. 

Polyaniline has been formed in the pores of Cu- or Fe-exchanged MCM-41 by adsorption of aniline vapour and subsequent oxidative polymerization (Figure 7.23), and these molecular wires demonstrate significant electronic conduction, although less than that of bulk polyaniline. Pyrolysis of polyacrylonitrile in the pores produces a graphitelike carbon chain, which exhibits microwave conductivity ten times that of bulk carbonized polyacrylonitrile. Such materials have potential for use in information processing as storage capacitors. 

The capacitance is expressed in nanofarads (10 ) or picofarads (10 ). Often the dielectric constant is measured in an alternating field. The reason more electrons can be stored on one plate of the capacitor at a given voltage with a solid dielectric is that electron fields in the material are distorted and counteract the impressed stress. Even a nonpolar polymer such as polyethylene can have valence electrons displaced to give an electronic displacement with a corresponding component of dielectric constant of about 2.0-2.5. A polar polymer such as poly(vinyl chloride) also can respond to an imposed field by actual orientation of molecular segments, provided it is above 7. ... 

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