Fluorination diamond films

Researchers are now seeking practical ways to fluorinate the surfaces of diamond films, as the resulting surfaces are expected to have very low coefficients of friction (cf. non stick polytetrafluoroethylene or Teflon, Section 12.3) and hence have applications in low-friction tools. Direct flu-orination with elemental fluorine is impractical, but photodecomposition of fluoroalkyl iodides chemically absorbed on the diamond surface looks promising.4... 

E. Wilson, Fluorine adds easily to diamond films. Chem. Eng. News, January 15, 6-7 (1996). 

Mcrowave technology [MICROWAVE TECHNOLGY] (Vol 16) for diamond films pOOLMATERIALS] (Vol 24) residue analysis of (TRACE AND RESIDUE ANALYSIS] (Vol 24) use in NDE [NONDESTRUCTIVE EVALUATION] (Vol 17) useof sulfur hexafluondem [FLUORINE COMPOUNDS, INORGANIC - SULFUR- SULFUR FLUORIDES] (Vol 11)... 

PECVD of fluorinated diamond-like carbon films (hydrogenated amorphous films)... 

Halogenating the surface of a diamond film is of interest for several reasons. Firstly, diamond films covered with, for example, fluorine are expected to show... 

The presence of halogens in reaction systems has been found to lead to an increased activation of the deposition surface, especially at low temperatures. " The rate coefficient of the abstraction reaction of surface H atoms by gaseous F atoms is more than two orders of magmtude greater than that of the abstraction reaction by H at 900°C or lower. " The deposition of diamond films at substrate temperatures as low as 250°C and relatively mild gas activation has been achieved in which fluorine was added to the gas mixture. " In addition, the sp carbon components may be preferentially etched by F atoms. " The use of chlorine-permuted methane as a carbon source also fevors high-purity diamond deposition at low temperatures and high methane concentrations. ... 

P. A. Molian, B. Janvrin, and A. M. Molian, Laser chemical vapor deposition of fluorinated diamond thin films for solid lubrication. Wear, 165(2) 133-140 (1993)... 

Okino, R, Shibata, H., Kawaguchi, Y. et al. (2004) Preparation of boron-doped semiconducting diamond films using BF3 and the electrochemical behavior of the semiconducting diamond electrodes. J. Fluorine Chem, 125, 1715. 

Fluorination [22] and chlorination [21] of diamond powders were carried out by Ando et al. without thermal activation for fluorine and with thermal activation for chlorine. Comparing the work with diamond films with that for powders shows that there are definite differences in reactivity. This is to be expected, because the surfaces of nanoparticles (or even microparticles) present a variety of crystallographic planes, as well as edges and corners. 

Okino P, Shibata H, Kawasaki S, Touhara H, Momota K, Nishitani-Gamo M, Sakaguchi I, Ando T (1999) Electrochemical fluorination of 1, 4-difluorobenzene using boron-doped diamond thin-film electrodes. Electochem Solid-State Lett 2 382-384... 

To conclude with the primary electrode characteristics, we describe briefly the DLC electrodes. The data are scarce and partly contradictory, probably due to the differences in film preparation methods. According to Howe [60], even films as thin as 50 nm are quite stable against corrosion. However, in later works [61, 62] such thin films turned permeable for electrolytes. The penetration of the electrolyte to a substrate metal resulted in its corrosion and, ultimately, in film peeling. Thicker films (0.1 to 1 pm) were less subjected to damage. The current-potential curves in supporting electrolytes resemble those for crystalline diamond electrodes (see Figs. 7, 8) the potential window is narrower, however [63], Fluorination of a-C H enhances corrosion resistance of the films significantly [64],... 

PTFE is a crystalline polymer consisting of twisted zigzag spirals with at least 13 repeating units per turn. This nonpolar polymer has a solubility parameter of 6.2 H, a high (327 C), and a heat deflection temperature of 121 C PTFE is a tough, flexible polymer which retains its ductility at extremely low temperatures (-269 0. The coefficient of friction of ptfe is the lowest of any known solid material (see Table 13.4). Films of ptfe can be bonded by adhesives to other surfaces if the polymer surface is treated with sodium. It also bonds to diamonds and graphite whose surfaces have been fluorinated. Liquid sodium removes fluoride ions from the surface and leaves free radicals on the polymer surface, ptfe is resistant to almost all corrosives and solvents, but it can be dissolved in hot perfluorinated kerosene, ptfe is difficult to mold or extrude. 

To solve the problem, we considered that a boron-doped diamond, BDD, is the most ideal anode for electrochemical fluorination and so we focused on a BDD electrode. The BDD film is prepared on a carbon substrate by hot-filament chemical vapor deposition with doping boron into the diamond lattice, adding trimethylboran gas to a mixed gas of methane and hydrogen. Since a BDD film has a high electric conductivity and stability of structure such as diamond, it is expected that a BDD electrode can be used as a new anode material in this... 

Ahmed, S.F., Baneijee, D., Chattopadhyay, K.K., 2010. The influence of fluorine doping on the optical properties of diamond-like carhon thin films. Vacuum 84 (6), 837—842. 

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