Carbon films

The transformations between one form of earbon and another ean be elassified as follows  

As noted above, amorphous earbon films ean be produeed from earbon-eontaining gas phases (physieal vapour deposition, PVD). They ean also be produced from hydroearbon-eontaining gases (ehemical vapour deposition, CVD). Both PVD and CVD proeesses ean be thermally-aetivated or ean be plasma- and/or eleetrie field-assisted proeesses (e.g., mierowave assisted CVD and ion beam deposition). As a eonsequence a wide range of processes have been developed to form amorphous carbon films and a correspondingly complex nomenclature has evolved [70, 71]. 

Amorphous carbon films may be broadly classified as (i) amorphous carbon films, a-C films, deposited from carbon-containing gases with low or zero hydrogen content [72] and (ii) hydrogenated carbon films, a-C H films, formed from hydrocarbon-containing gases [73,74]. Both types of film contain different amounts of sp and sp bonded carbon. The amount of sp bonded carbon can be estimated from X-ray absorption near edge spectroscopy, 

and in a-C H films the sp sp ratio can be measured directly using nmr spectroscopy [71]. 

The classification of amorphous carbon films according to carbon bond type and hydrogen content can be represented in a triangular diagram, Fig. 6 [e.g., 70]. The comers at the base of the triangle correspond to graphite (100% sp carbon) and diamond (100% sp carbon). The apex represents 100% H, but the upper limit for formation of solid films is defined by the tie line between the compositions of polyethene, -(CH2) -, and polyethyne, -(CH) -. 

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ENHANCED SIGNAL-TO-BACKGROUND RATIO WITH A HIGHLY ORDERED PYROLYTIC CARBON FILM AS AN ELECTROCHEMICAL INTERFACE... 

Figure 3 Bright-field (a) and dark-field (b) STEM images of crushed ceramic particles dispersed on a "holey" carbon film supported on an electron microscope grid (shown at the right).

Figure S ERS and RBS spectra for a 1000-A sputtar-deposKed diamond-like carbon film on Si. Both spectra are required for complete analysis.

There are many applications for diamonds and related materials, e.g., diamondlike carbon films, and there are potential applications for Fullerenes and carbon nanotubes that have not yet been realised. However, the great majority of engineering carbons, including most of those described in this book, have graphitic microstructures or disordered graphitic microstructures. Also, most engineering carbon materials are derived firom organic precursors by heat-treatment in inert atmospheres (carbonisation). A selection of technically-... 

Fig. 2a. Bundles and individual single-layer carbon nanotubes bridge across a gap in a carbon film.

For some non-ferrous metals (copper, lead, nickel) the attack by sulphuric acid is probably direct with the formation of sulphates. Lead sulphate is barely soluble and gives good protection. Nickel and copper sulphates are deliquescent but are gradually converted (if not leached away) into insoluble basic sulphates, e.g. Cu Cu(OH)2)3SO4, and the metals are thus protected after a period of active corrosion. For zinc and cadmium the sulphur acids probably act by dissolution of the protective basic carbonate film. This reforms, consuming metal in the process, redissolves, and so on. Zinc and cadmium sulphates are formed in polluted winter conditions whereas in the purer atmospheres of the summer the corrosion products include considerable amounts of oxide and basic carbonate. ... 

The reaction of lead with concrete differs from that of aluminium and of zinc in that it is not normally rapid during the early wet stage. It is, however, progressive in damp conditions, and this is said to be due to the fact that the concrete prevents the formation of a protective basic lead carbonate film on the surface of the lead. The packing of lead cables in plaster of Paris is reported to be of doubtful value in preventing corrosion from surrounding concrete. 

Secondly, under certain conditions copper may suffer intense localised pitting corrosion, leading sometimes to perforation of the tube, in quite a short time. This form of attack is not common and depends on a combination of unusual circumstances, one of which is the possession by the tube of a fairly, but not entirely, continuous film or scale that is cathodic to the copper pipe in the supply water this can set up corrosion at the small anodes of bare copper exposed at faults or cracks in the film. Carbon films give rise to such corrosion, but since 1950, when the importance of carbon films was... 

Campbell points out that in evaluating condenser tube materials a test apparatus is required that will include all the principal hazards likely to be encountered in service and should thus cater for the following conditions impingement, slow moving water, heat transfer and shielded areas. Furthermore, the internal surfaces should not be abraded, as in the jet impingement test, but should be tested in the as-manufactured condition, particularly in view of the deleterious effect of carbon films produced during manufacture (see Sections 1.6 and 4.2). LaQue has pointed out the importance of specimen area in impingement tests... 

Tsai, H., and Bogy, D. B., Characterization of Diamondlike Carbon Films and Their Application as Overcoat on Thin-Film Media for Magnetic Recording, J. Vac. Sci. Technol. A, 5(6) 3287-3312 (Nov/Dec 1987)... 

Erdemir, A., EryUmaz, O. L., and Fenske, G., Synthesis of Diamond-like Carbon Films with Superlow Friction and Wear Properties,"/. Vac. Sci. Technol. A, Vol. 18, 2000, pp. 1987-1992. 

Erdemir, A., The Role of Hydrogen in Tribological Properties of Diamond-Like Carbon Films," Surf. Coat. Technol., Vol. 146/147,2001, pp. 292-297. 

Rolo, M. C., Andujar, J. L., Robertson, J., and MUne, W. I., Preparation of Tetrahedral Amorphous Carbon Films by Filtered Cathodic Vacuum Arc Deposition," Diamond Relat. Mater., Vol. 9,2000, pp. 668-661. 

Stress-free Amorphous-Tetrahedral Carbon Films with Hardness Near that of Diamond, Appl. Phys. Lett., Vol. 71,1997, pp. 3820-3822. 

Koidl, R, Wild, Ch., Dischler, B., Wagner, J., and Ramsteiner, M., Plasma Deposition, Properties and Structure of Amorphous Hydrogenated Carbon Films, Mater. Sci. Forum, Vol. 

Gangopadhyay, A., Mechanical and Tribological Properties of Amorphous Carbon Films, Tribol. Lett., Vol. 5, 1998, pp. 25-39. 

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