Fluorination, depth

P. Walter, M. Menu, I.C. Vickridge, Fluorine depth profiles as a relative dating method of chipped flints, Nucl. Instr. Meth. B45 (1990) 119-122. 

A.W. Crawford, W.J. Sampson, H.J. Debruin, Shallow fluorine depth profiles of cementum in periodontal disease - a pilot-study, J. Dent. Res. 62 (1983). ... 

Lindh, U. and Tveit, A.-B. (1980) Proton microprobe determination of fluorine depth distributions and surface multielement characterisation of dental enamel. J. radioanal. Chem., 59, 167-191. 

Bertrandite, 4BeO 2Si02 H20, became of importance ia 1969 when the deposits of Spor Mountain ia the Topa2 district of Utah were commercially Opened. These deposits are befieved to have been derived from fluorine-rich hydrothermal solutions at shaUow depths (2). Whereas economical beneficiation of these ores averagiag < 1% BeO has not been achieved, these deposits are commercially viable because of the large reserves present. 

J. B. Pallix, C. H. Becker, and K. T. Gillen, Appl. Surface Sck 32,1 (1988). An applications oriented discussion of using MPI-SALI for depth profiling, interface analysis in inorganic material systems. Examples of SALI depth profiles are given of a B implant in Si and the fluorine implanted electronic test device which was referenced in this encyclopedia article. 

The mounted samples were placed in the XPS vacuum chamber, and the chamber was evacuated prior to testing. The samples were exposed to the X-rays at 14.0 kV and 300 W. The approximate sampling area for the XPS is 1.0mmx3.5mm with a sampling depth of approximately 35.0 A at a 45° exit angle. Figures 16 and 17 show the survey scans from the epoxy and composite sample, respectively. Both show the presence of fluorine, which indicates the probable presence of a mold-release agent. 

If solid polymer objects are fluorinated or polymer particles much larger than 100 mesh are used, only surface conversion to fluoropolymer results. Penetration of fluorine and conversion of the hydrocarbon to fluoropolymers to depths of at least 0.1 mm is a result routinely obtained and this assures nearly complete conversion of finely powdered polymers. These fluorocarbon coatings appear to... 

Figure 15.3 shows the results of the second SEM analysis designed to give a qualitative determination of the depth of fluorination. A carefully prepared cross section of the O-ring was analyzed using the so-called mapping technique. The light streak across Picture 3.2 shows where the fluorine is concentrated. With the aid of the microscale shown it can be estimated that the fluorination is approximately 5 pm deep. 

It has been well recognized that the hydrolysis of alkoxysilanes and chlorosilanes is effectively catalyzed when fluoride anions are present due to formation of hypercoordinated silicon intermediates.803 More in-depth studies by Bassindale et al. showed that the reaction of PhSi(OEt)3 with stoichiometric amounts of Bu4NF surprisingly yields an encapsulation complex, namely tetrabutylammonium octaphenyloctasilsesquioxane fluoride 830, in which the fluorine atom is situated inside the cubic siloxane cage (Scheme 114). The Si--F distance of average 2.65 A is shorter than the sum of van der Waals radii (3.57 A), which renders the coordination number of the silicon atoms at [4+1]. 

Here we would like to emphasize that treatment with XeFj fluorinates the polymer surfaces, with the depth and degree of fluorination depending upon the reaction conditions. We never observed the formation of a perfluorinated surface layer after treatment with XeF,. Results of XPS analysis of XeFj-treated polyethylene film —(—CHj—CHj—) — showed that the maximum degree of fluorination corresponded to the composition —(—CF2—CH2—) —. After that, visible destruction of the polymer surface, i.e., cleavage of C—C bonds in the polymer macromolecule, would start. These results differ from those of the fluorination of polymer powders it was reported by Lagow and Margrave in the early 1970s that polymer powders were fully converted into perfluorinated polymers under the action of a F /N mixture. ... 

---