Carbon-reinforced graphite

Electrodes consisting of carbon-reinforced graphite or carbon fibers were investigated with the redox reactions of soluble vanadium ions. The former material showed evidence for the intercalation of H2SO4 at concentrations >5 mol how-... 

Carbon-Carbon Composites. Carbon—carbon composites are simply described as a carbon fiber reinforcement in one or many directions using a carbon or graphite matrix material (see Composite materials). 

Carbon—carbon composites for rocket nozzles or exit cones are usually made by weaving a 3D preform composed of radial, axial, and circumferential carbon or graphite fibers to near net shape, followed by densification to high densities. Because of the high relative volume cost of the process, looms have been designed for semiautomatic fabrication of parts, taking advantage of selective reinforcement placement for optimum thermal performance. 

High performance composites may be laminates wherein veils of carbon fiber ate treated with an epoxy resin, stacked up to the desired final product thickness, and then laminated together under heat and pressure (see Composite materials Carbon and graphite fibers). Simply mixing together carbon or glass fibers and polymeric resins to form a reinforced plastic leads to a composite material, but this is not a laminate if not constmcted from discrete phes. 

Carbon Composites. Cermet friction materials tend to be heavy, thus making the brake system less energy-efficient. Compared with cermets, carbon (or graphite) is a thermally stable material of low density and reasonably high specific heat. A combination of these properties makes carbon attractive as a brake material and several companies are manufacturing carbon fiber—reinforced carbon-matrix composites, which ate used primarily for aircraft brakes and race cats (16). Carbon composites usually consist of three types of carbon carbon in the fibrous form (see Carbon fibers), carbon resulting from the controlled pyrolysis of the resin (usually phenoHc-based), and carbon from chemical vapor deposition (CVD) filling the pores (16). 

A polymer blend is a physical or mechanical blend (alloy) of two or more homopolymers or copolymers. Although a polymer blend is not a copolymer according to the above definition, it is mentioned here because of its commercial importance and the frequency with which blends are compared with chemically bonded copolymers. Another technologically significant material relative to the copolymer is the composite, a physical or mechanical combination of a polymer with some unlike material, eg, reinforcing materials such as carbon black, graphite fiber, and glass (see Composite materials). 

One typical example of carbon/carbon composite plates is that made by Oak Ridge National Laboratory (ORNL) in the United States [12]. The composite preform was fabricafed by a slurry-molding process from fhe mixed slurry befween short carbon fibers (graphite fibers were also added in some sample plates) and fhe phenolic resin. The mass rafio between fiber reinforcement and phenolic matrix is 4 3. The phenolic matrix improves the mechanical properties and dimensional stability of the plate. A subsequent vacuum molding process was utilized to fabricate composite plates and fluid fields with relatively high resolution (Figure 5.3, [11]). 

Asbestos fibers are found worldwide in many products as reinforcement in cement water pipes and the inert and durable mesh material used in filtration processes of chemicals and petroleum, for example. However, asbestos is not the only inorganic fiber in use today. Synthetic inorganic fibers abound. Glass fibers have replaced copper wire in some intercontinental telephone cables. Fiberglas (a trade name) has become the insulation material of choice in construction. Carbon and graphite fiber composites are favored materials for tennis racket frames and golf clubs. Fibrous inorganic materials have become commonplace in our everyday lives. 

Recall from Section 1.4.5.1 that there are two primary types of carbon fibers polyacrylonitrile (PAN)-based and pitch-based. There are also different structural forms of these fibers, such as amorphous carbon and crystalline (graphite) fibers. Typically, PAN-based carbon fibers are 93-95% carbon, whereas graphite fibers are usually 99+%, although the terms carbon and graphite are often used interchangeably. We will not try to burden ourselves with too many distinctions here, since the point is to simply introduce the relative benefits of continuous-fiber composites over other types of composites, and not to investigate the minute differences between the various types of carbon-fiber-based composites. The interested reader is referred to the abundance of literature on carbon-fiber-reinforced composites to discern these differences. 

Graphite fibers [CARBON AND GRAPHITE FIBERS] (Vol 5) [COMPOSITEMATERIALS - SURVEY] (Vol 7) as ceramic composite reinforcements [COMPOSITE MATERIALS - CERAMIC MATRIX] (Vol 7) useofbrominein [BROMINE] (Vol4)... 

Interest in microelectrodes, in vivo analysis, and carbon-reinforced structural materials has stimulated research on the electrochemical behavior of carbon fibers. Such fibers have diameters ranging from a few micrometers to about 60 pm, with the majority in the range of 5-15 pm. Although carbon fibers have a wide variety of structures and properties and are often less well characterized than GC or graphite, they have been used successfully in several important electroanalytical experiments. 

Carbon and graphite fibers are made by the pyrolysis of certain naturally occurring and man-made fibers, such as regenerated cellulose (rayon) fibers. A wide range of physical, mechanical and chemical properties may be obtained dependent on amount of dehydration. This product is one of the most structurally efficient reinforcements. Unlike any other reinforcement, it retains its 2,800 MPa (400,000 psi) tensile strength when tested up to a temperature of 2700 C (4800F). 

Polymer composites consisting of polymers reinforced with various additives such as carbon fibers, graphite fibers, glass fibers, or Kevlar fibers and carbon black are increasingly being used in... 

Smaller utensils can easily be prepared in the laboratory from pieces of pure synthetic carbon or graphite. Tubes, plates, valves and other shapes made of pure graphite, as well as of graphite reinforced with synthetics, are commercially available. 

The generally low-specific gravity and high strength of reinforcement fibers such as glass, aramid, carbon, and graphite can provide other benefits. For example, the toughness of these fibers allows them to be molded into very thin constructions. Each have special characteristics,... 

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