Electrical and electronic properties

Generally, the electronic properties of an isolated defect-free SWCNT are dependent on the helicity (or chirality) of the CNT structure (i.e., the circumferential wavevector discussed above). The helicity is defined as the vector C, along which a graphene sheet is rolled up into a seamless hollow cylinder. The vector C can be expressed in terms of two integers (m, n) corresponding to the 

As the vector C wraps around the circumference of the SWCNT, its two endpoints are superimposed exactly. Hence, the notation (m,n) carries the information of both the helicity and the size of the SWCNT. It is known that a defect-free SWCNT presents semiconducting properties if 

on the other hand, are nearly 100% metallic wires with linear I-V properties [35,36]. PECVD-grown CNFs are of particular interest since they can be grown deterministically on a solid substrate at desired locations with well-controlled vertical alignment [12,35,37]. A temperature-dependent study over a range of 4 to 300 K revealed that the electron transport along the CNF consists of the mixture of graphite a - and c-axis transport mechanisms [36]. At room 

A more defective form of sp carbon fibers, carbon nanotubules (CNTbs), grown by pyrolytic deposition of carbon into anodized aluminum oxide (AAO) nanochannels, are also used as nanoelectrode arrays for electrochemical sensors. Small graphitic crystallites are deposited on the inner surface of the nanochannels. Since the crystallites do not extend very long (less than micrometers) and are structurally discontinued, the resistance is orders of magnitude higher than CNFs 

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Just as materials have a response when placed in an electric field, they can have a response when placed in a magnetic field. We will see in this section that many of the concepts of permanent dipoles and dipole alignment in response to an applied field that were described in the context of electrical fields apply to magnetic fields as well. There are a few differences, however, and we will also see that there are fewer materials with specialized magnetic properties than there were with specialized electrical and electronic properties. The magnetic properties of materials are nonetheless important, and they are applied in a number of technologically important areas. 

It is well known that catalyst support plays an important role in the performance of the catalyst and the catalyst layer. The use of high surface area carbon materials, such as activated carbon, carbon nanofibres, and carbon nanotubes, as new electrode materials has received significant attention from fuel cell researchers. In particular, single-walled carbon nanotubes (SWCNTs) have unique electrical and electronic properties, wide electrochemical stability windows, and high surface areas. Using SWCNTs as support materials is expected to improve catalyst layer conductivity and charge transfer at the electrode surface for fuel cell oxidation and reduction reactions. Furthermore, these carbon nanotubes (CNTs) could also enhance electrocatalytic properties and reduce the necessary amount of precious metal catalysts, such as platinum. 

According to the bond model all alkali metal suboxides are metallic. So knowledge on their electrical and electronic properties is essential to verify the model. Electrical resistivity measurements, investigations of optical reflectivities and the UV-photoelectron spectra of alkali metal suboxides are discussed in terms of the bond model in the following section. 

Polypyrrole is one of a series of heterocyclic polymers which has attracted much attention due to its characteristic electric and electronic properties. However, there are some problems relating to the physical and material properties associated with its structure. The fundamental structural formulae shown in Fig. 16.5 have been generally proposed for the structures of dedoped and doped polypyrroles, where the aromatic form corresponds to the dedoped state and the quinoid form corresponds to the doped state [9-11]. However, the actual structure appears to be more complicated. At present the exact structure is not known because the polymer is amorphous and insoluble. Consequently, various structures have been proposed for polypyrrole [10]. 

PROPERTIES OF SPECIAL INTEREST PPS is a semiciystalline thermoplastic. PPS reinforced with glass fiber or mineral fillers shows excellent mechanical prop>erties, high thermal stability, excellent chemical resistance, excellent flame retardance, good electrical and electronic properties, and good mold precision Recently developed linear type PPS additionally shows improved properties of elongation and toughness and opens the new route for the use of a neat polymer. 

When electrical and electronic properties are also of interest apart from mechanical and thermal properties, carbon nanotubes can be of better advantages. Nanotubes are inert in nature and, therefore, also require surface modification in order to achieve compatibility with the polymer matrices. Thus, the nanoscale dispersion of the nanotubes is as important and challenging as the layered silicates as the properties are dependant on the generated morphology in the composites. In a representative study, Teng et al. 

In comparison to conventional reactor systems, microreactors are easier to scale up by numbering-up (external or internal numbering). Most microreactors are made from silicon wafer or Si bulk using traditional semiconductor microfabrication methods, whilst other materials such as ceramic, glass and stainless steel have also been used in their design. The design of microreactors made from these materials is based on the application type, thermal conductivity, mechanical, electrical and electronic properties of each material. 

Certain classes of plastics, such as silicones, fluoropolymers, and others, have more stable electrical properties than many other plastics and polymer structures. In plastics having less stable electrical and electronic properties, these properties worsen as operating conditions worsen. For instance, dielectric constant and/or dissipation factor increase as temperature or humidity increase, with this increase often being dramatic or even destructive at the glass transition temperature of the plastic. Those property values are also affected by the frequency of the electrical system. (See also dielectric constant dissipation factor.)... 

This chapter is divided into ten sections (1) introduction (2) allotropic forms of carbon (3) processing routes of carbon (4) structure of some novel phases of carbon (5) electrical and electronic properties of conducting carbon (6) electronic structure to explain electrical and optical properties (here we introduce the mechanism of conduction, interaction between carriers, localization, and the role of hydrogen concentration and dopant in the conductivity of carbon films) (7) optical properties (8) spectroscopic study (IR, Raman) (9) defect study in amorphous carbon and (10) applications and conclusions. We wish to give a view of novel forms of carbon and to analyze their special characteristics rather than review the well-known earlier work. The interrelationship among the different sections gives a complete picture of amorphous carbon and its importance at present from various aspects. 

J. I. Kroschwitz, Electrical and Electronic Properties of Polymers A State of the Art Compendium, John Wiley Sons, Inc., New York, 1988. 

In addition to the various experimental techniques used to determine and verify the electrical and electronic properties of conductive acetylene copolymers, a number of theoretical calculations and models have also been adopted for the prediction and explanation of the observed electrical properties. The density of... 

Chen X, Wei S, Yadav A, Patil R, Zhu J, Ximenes R, Sun L, Guo Z (2011) Poly(propylene)/carbon nanofiber nanocomposites ex situ solvent-assisted preparation and analysis of electrical and electronic properties. Macromol Mater Eng 296 434 43... 

The depositing film material may diffuse and react with the substrate to form an interfacial region . The material in the interfacial region has been called the interphase material and its properties are important to the adhesion, electrical, and electronic properties of film-substrate systems. In particular, the development of ohmic contacts to semiconductor materials is very dependent on the interface formation process, The type and extent of the interfacial region can change as the deposition process proceeds or may be modified by post-deposition treatments. Interfacial regions are categorized as ... 

Table 2. Electric and Electronic Properties V-60 Table 7. Solubility/Solution Properties V-62...

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