Fluorine/carbon elemental ratios

Dalton s atomic theory explains this by stating that atoms of different elements combine to form compounds. 5. The calcium atoms and some of the oxygen atoms are in the calcium oxide the carbon atoms and some of the oxygen atoms are in the carbon dioxide. 7. The Law of Multiple Proportions in this case states that the same mass of sulfur combines with masses of fluorine in the ratio of simple whole numbers, 4 to 6. 9. See Table 5.1. 

Loss of fluorine destabilizes PTFE s structure. As the fluorine-to-earhon ratio deereases, the color of PTFE changes from white to brown and then to black. The hlaek layer is normally comprised of carbon, some oxygen, and small amounts of other elements. 

The fragile element fluorine can be produced inside the He-intershell of AGB stars. Jorissen, Smith Lambert [130] discovered that the [F/O] abundance correlates with the C/O ratio in AGB stars, and that some N-type carbon stars show surface enrichments a factor of 30 above the solar ratio. The increase in the C/O ratio is clearly a result of the third dredge-up and thermal pulses, hence it was concluded that the carbon and fluorine are produced in the same region in the star and mixed together to the surface. Jorissen et al. [130] examined the many pathways that fluorine, or more precisely the isotope 19F, could be produced and concluded that the most likely chain is... 

Fig 10.34) indicate that the PTFE surface is comprised of only carbon and fluorine. The energy shift can be curve-fitted by trial and error to determine the functional groups on the surface. The most simplified report that ESCA generates is the atomic composition of the surface elements with the exception of hydrogen. A helpful tool for investigating surface changes of a polymer is the ratio of other elements to carbon. Table 10.9 shows the effect of sodium etching on the surface composition of a few different fluo-ropolymers. 

The chemical composition of most specimens has been checked where possible, using an analytical scanning electron microscope with energy-dispersive x-ray spectrometry facility. Elements with atomic number below that of fluorine are not detectable by this technique, e.g. boron, carbon and oxygen. Fluorine is only detectable when present in major amounts. Ratios quoted are semi-quantitative atomic ratios. Other elements are also listed where present at detectable levels. 

The chemical composition of such treated surfaces, shown by XPS, does not present any oxygen atoms the Ois peak is not detected anymore. Therefore, a fluo-rinated layer whose elemental composition corresponds to a Teflon-like structure covers the entire LDPE surface (Table 2). Since the ratio between fluorine and carbon atomic concentrations does not increase with the plasma parameters, i.e. a plateau value is rapidly obtained, so the observed increase of contact angle is mostly induced by the increase of the surface roughness. 

The striking feature of the isotopic ratios that you should note in this spectrum is the low [M + l ]/[M ] ratio and similar ion-abundance ratios (m/z 72 is not tabulated, since its intensity is <0.2). Because of these ratios the elements carbon, oxygen, silicon, sulfur, and chlorine are all eliminated from consideration. Note that there are intense peaks at [M — 19] and (M — 2 X 19) as well as m/z 19 indicating the presence of fluorine. [Nitrogen trifluoride]... 

The presence of the A -1- 2 element chlorine should be obvious from both the m/z 104/106 and 85/87 intensity ratios. The m/z 69/70 intensity ratio indicates the presence of one carbon atom, which is consistent with both m/z 85/86 and 50/51. The remaining mass of each of these ions must be provided by an A element, and only fluorine appears to be appropriate an intense one-carbon m/z 69 peak is typical of the CF3 group. [Chlorotrifluoromethane]... 

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