Carbon fibre types

Note The tensile modulus (Young s modulus) varies ca. 275-350 GPa, but the disposition of the boundaries is somewhat arbitrary. The relatively high tensile strength required is achievable by a significant reduction of the single filament diameter down to about 5 pm. Such small filament diameters are typical of CARBON FIBRES TYPE IM. 

A unidirectional fibre composite consists of 60% by volume of continuous type-1 carbon fibres in a matrix of epoxy. Find the maximum tensile strength of the composite. You may assume that the matrix yields in tension at a stress of 40 MPa. 

We must therefore hope that CFRP can give us the required anisotropy. The modulus of type-1 carbon fibres is 390 GPa along the fibre axis (although it is only 12 GPa at right angles to this). So... 

ICl Development polymide Resin QX-13 and Morganite Modmor Type I (treated) carbon fibre. Unidirectional laminate (S2% v/v fibre content)]. vSource of data ICl Trade Lilerature... 

High heat distortion temperatures (over a range 170-350°C) for unfilled materials with some further increase with some types when filled with glass or carbon fibre. 

The product from acrylonitrile will withstand a bunsen flame in the open air and is the basis of one type of carbon fibre. None of the polymers produced by this route have a high degree of perfection in their ladder structure. 

Among the several known types of carbon fibres the discussion in this chapter is limited to the electric arc grown multi-walled carbon nanotubes (MWCNTs) as well as single-walled ones (SWCNTs). For MWCNT we restrict the discussion to the idealised coaxial cylinder model. For other models and other shapes we refer to the literature [1-6],... 

In conclusion, wc have shown the interesting information which one can get from electrical resistivity measurements on SWCNT and MWCNT and the exciting applications which can be derived. MWCNTs behave as an ultimate carbon fibre revealing specific 2D quantum transport features at low temperatures weak localisation and universal conductance fluctuations. SWCNTs behave as pure quantum wires which, if limited in length, reduce to quantum dots. Thus, each type of CNT has its own features which are strongly dependent on the dimensionality of the electronic gas. We have also briefly discussed the very recent experimental results obtained on the thermopower of SWCNT bundles and the effect of intercalation on the electrical resistivity of these systems. 

Most researchers were not apparently aware of earlier CNT preparations in the context of ultra-thin vapour-grown carbon fibres (VGCF). This type of CNT is termed pyrolytic (PCNT) and its preparation shows promise of large-scale synthesis. Needless to say, it is of practical importance to provide sufficient CNTs at reasonable cost. This chapter highlights the preparation methods, structural characteristics and current commercial status of PCNTs and includes a description of the devices used hitherto to obtain aligned PCNTs. By way of... 

In all cases, carbon fibres lead to the highest mechanical performances compared to glass and aramid fibres. Nevertheless, their impact behaviour and price restrict their consumption. Glass fibres yield the cheapest composites but performances are more limited. Table 6.10 compares the properties of the main fibre types and shows some examples of properties for a nylon matrix reinforced with short fibres of the three types. 

Figure 7.5 shows, for the same period, the relative number of recent patents per fibre type. Nanotubes and nanocomposites, particularly carbon nanotubes, are generating intense research activity whereas research is definitely weaker for nanofibres. Figure 7.6 shows, for the same period, the recent patents for the different nano-reinforcements. 

Examples of 1,2 migration of silyl group from silicon to other atoms are also well documented. Reaction (6.21) that involves a transfer from silicon to carbon has been observed in the gas phase at elevated temperatures [35], From the measured Arrhenius parameters, i.e. logA/s = 12.3 and = 90kJ/mol, it is clear that the reaction is unimportant around room temperature. However, this type of reaction is probably the essential step in the formation of silicon-carbon fibres by pyrolysis of methylpolysilanes. 

Jones, P.L. and Sidell, B.D. (1982). Metabolic responses of striped bass to temperature acclimation. II. Alterations in metabolic carbon sources and distributions of fibre types in locomotory muscle. Journal of Experimental Zoology 219,163-171. 

Activated charcoal was originally regarded as a relatively inexpensive adsorbent with an assortment of pores of ill-defined size and shape. However, in recent years considerable progress has been made in the development of tailor-made porous carbons such as molecular sieves, activated carbon fibres and carbon composites (Marsh et al., 1997). Superactive carbons are now made on a commercial scale with BET areas of around 3000 m2g-1. Activated carbons can be manufactured as fine particles or granules or in the form of a cloth, felt or consolidated membrane. The properties of some of these special types of activated carbon are discussed in Chapter 12. 

The recent contribution by Kaneko et al. (1995) has revealed that it is possible to produce highly hydrophobic fluorinated microporous carbon fibres. Two fluorinated carbons were reported to have apparent surface areas of 420 and 340 m2g and micropore volumes of, respectively, 0.19 and 0.14cm3g 1. These materials gave Type I nitrogen and methanol isotherms, but the adsorption of water vapour was too small to measure at pjp° < 0.8 and the uptake was very low even at p/p° 1. 

Fig. 9.8. High-resolution TEM micrograph of fishbone type carbon fibre. Note the graphite lattice planes with distances in between of 0.34 nm [Courtesy J.W. Geus].

The formation of filamentous carbon deposits on transition metal catalysts (Fe, Co, Ni) and their alloys have been investigated in some detail over the past two decades.21,38-40 Among them, nickel is the most promising candidate since it forms carbon deposits at temperatures as low as 723-823 K using CH4, C2H6 or CO + H2 feeds. Carbon fibres are usually produced during these reactions. Typical forms of the carbon produced from CH4 decomposition on silica-supported Ni catalysts are shown in Fig. 7.1. The pyrolysis of methane at temperatures somewhat lower than 873 K produces fish-bone type nanofibres.41 The Ni metal particles are present at the tip of each carbon fibre, and catalyse methane decomposition as well as growth... 

The most straightforward type of tactile sensor. used consists of a contact switch which provides binary high-low information. Other types of mechanism such as strain gauges and carbon fibre materials change their electric resistance under stress, whereas piezoelectric materials generate an electric charge when subjected to mechanical strain. 

Moving up from nano-scale to micro-scale, carbons exhibit veiy different structures. Some of these microstructures are arranged in preferential directions, like synthetic graphite or graphitized carbon fibres, while disordered microstructures are characteristic of chars or activated carbons. Such a wide variety of possible structures gives rise to a large amount of different types of carbons. Fig. 1 shows a schematic representation of some of these carbon structures. 

This section deals with the most relevant aspects of the different types of activated carbon including shapes other than PAC and GAC such as activated carbon fibres and other special forms of carbon (see Fig. 21). 

Integral-type monolithic structures are produced by extrusion. The extrusion mixture generally includes the following components a type of carbon or carbon precursor such as activated carbon particles, graphite, carbon fibres, etc., a blinder such as phenol resin, hydroxylcellidose, coal tar pitch etc. and extrusion aids/plasticizers such as water or polymers. Typical preparation steps are mixing, extrusion, diying/solidification and carbonization. 

The hydrogen capacity of a large variety of microporous activated carbons and activated carbon fibres has been measured in a wide pressure range at room temperature [117]. The hydrogen adsorption isotherms of the samples at 293 K and up to 70 MPa have similar shapes and are of type I according to foe lUPAC classification. Fig. 27 shows the amount of hydrogen adsorbed (in wt%) in the studied samples at 10 MPa and 70 MPa vs foe Dubinin Radushkevich (DR) micropore volume measured by nitrogen or CO2 adsorption. 

The Wheeler-Jonas equation has been used extensively in the case of pure physisorption on granular carbons. But recently, it has been demonstrated it can be equally well applied in a number of very divergent cases. The first extension is on the type of adsorbent, especially new types. The validly of the Wheeler-Jonas equation has been demonstrated [117,118] for both activated carbon fibres (ACF) and activated carbon monoliths (ACM). The equation itself and the calculation of the capacity IFe remain unchanged. As for the estimation of the overall mass transfer coefficient, the normal equation stays valid, providing a correct interpretation of the equivalent diameter of the particles . For ACFs, dp has been calculated fiom the total external surface. Given their small diameter, dp is essentially related to the length of the fibres [ 119]. For ACMs, dp seems to be related to the internal diameter of the channels. 

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