Increasing Fluorine Content Research Articles

Surface and mechanical properties of waterborne polyurethane films reinforced by hydroxyl-terminated poly(fluoroalkyl methacrylates)

Novel waterborne fluorinated polyurethane (WFPU) based on hydroxyl-terminated poly(fluoroalkyl methacrylates) (HTPFMA) was prepared successfully. The microstructures and micro-phase separation of WFPU were evaluated through infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dynamic mechanical analysis (DMA), and scanning electron microscope (SEM). FT-IR revealed that the H-bonded carbonyl in hard domains increased with the increasing of fluorine content, resulting in enhancing the extent of micro-phase separation between hard and soft segments. XRD results indicated that the crystallinity of hard segment was enhanced with the increasing of fluorine content. The direct visual microstructures by SEM showed that the micro-phase separation was more significant when the fluorine content increased. DMA also revealed strengthened micro-phase separation with increasing fluorine content. The studies of mechanical properties confirmed that WFPU based on HTPFMA had outstanding mechanical properties. The effects of fluorine content on the static contact angles, surface free energy, and surface composition were also studied. The static contact angles of the WFPU films against water and methylene iodide reached around 108° and 84°, respectively. X-ray photoelectron spectroscopy (XPS) confirmed that the fluorine surface enrichment factor in the outermost 10 nm depth was about 10–18 fold higher than its bulk level.

Synthesis of core-shell fluorinated acrylate copolymers and its application as finishing agent for textile

Core-shell fluorinated acrylate copolymers emulsion was thus synthesized via the core-shell emulsion polymerization with the fluorinated monomers and acrylic monomers as the main raw materials and its properties were studied. PFMA, the fluorinated acrylate monomers, was synthesized by the esterification of perfluorooctanoyl chloride (PFOC) and hydroxypropyl methacrylate (HPMA). Then the core-shell fluorinated acrylate copolymers emulsion with a poly(MMA/BA/St) core and a poly(PFMA/MMA/BA) shell was synthesized via a starved semi-continuous core-shell emulsion polymerization method by using KPS and sodium bicarbonate as the initiator/buffer system and SDS/Twain 80 as the commixture emulsifier. Lastly, the synthesized copolymers was applied as textile finishing agent for cotton textile. The results of FT-IR and NMR indicated that PFMA had been synthesized as expected and effectively combined in the emulsion copolymerization. The GPC, zeta potential, TEM and DSC showed that the particles had uniform spherical core-shell structure with a diameter of 65-150 nm, and the distribution and emulsion stability was satisfactory. As XPS, FESEM and AFM shown, a hydrophobic structure which was similar to the structure of the lotus leaf were formed and the surface hydrophobicity of the films can be improved. Based on the analysis of DSC, thermal stabilities of the films were enhanced with the increase of fluorine content. Besides, FESEM of textiles showed that the surface of treated textiles were smooth and the edges were clear and visible, indicating significant improvement of the performance on water and oil repellent.

Fluorine follows water: Effect on electrical conductivity of silicate minerals by experimental constraints from phlogopite

Fluorine and hydroxyl groups are minor constituents of silicate minerals, and share a lot of similarities concerning their physical and chemical properties. Hydroxyl groups significantly enhance the electrical conductivity of many silicate minerals, and it is expected that fluorine would have a comparable effect. This, however, has never been documented quantitatively. Here we present experimental approaches on this issue, by investigating the electrical conductivity of phlogopite with a wide range of fluorine content (but with broadly similar contents for other major elements). Electrical conductivities of gem-quality single crystal phlogopites, with samples prepared along the same orientation (normal to the (001) plane), were determined at 1GPa and 200–650°C using an end-loaded piston cylinder apparatus and a Solartron-1260 Impedance/Gain Phase Analyzer over the frequency range of 106 to 0.1Hz. The complex spectra usually show an arc in the high frequency range and a short tail in the low frequency range, which are caused by lattice conduction and electrode effects, respectively. The electrical conductivity increases with increasing fluorine content, and the main charge carriers are fluorine. The activation enthalpies are ∼180 to 200kJ/mol, nearly independent of fluorine content. The conductivity is linearly proportional to the content of fluorine, with an exponent factor of ∼1. The results demonstrate that conduction by fluorine leads to very high electrical conductivity at high temperatures. The influence of fluorine on electrical conductivity may be compared to that of hydrogen in nominally anhydrous minerals. This, along with the close association of fluorine and hydroxyl groups in silicate minerals and their similar crystal-chemical behaviors, suggests a more general role of fluorine in enhancing the electrical conductivity of many silicate minerals. Fluorine-rich assemblages, e.g., phlogopite and amphibole, could be locally enriched in the upper mantle, and if they form connected networks as observed for some natural samples, regionally high electrical conductivities could be produced. It has been recently proposed that the transition zone is probably a major reservoir for fluorine in the mantle, due to the significant dissolution of fluorine in wadsleyite and ringwoodite and the coupled incorporation with hydroxyl groups. As such, geophysically-resolved high electrical conductivities in the transition zone may be accounted for by fluorine in the dominant minerals, rather than by hydroxyl groups. The results of this work would stimulate a wide scope of future studies on the deep fluorine cycle, the deep water cycle and the geodynamical properties of the mantle.

Synthesis and characterization of novel fluorinated thermoplastic polyurethane with high transmittance and superior physical properties

ABSTRACTThree novel series of transparent fluorinated thermoplastic polyurethane (FTPU) elastomers based on 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), polytetramethylene glycol (PTMG), polycaprolactone (PCL) and 4,4′-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene] bisphenol (BPAF) were synthesized by two-step solution polymerization. The FTPU were characterized by Fourier transform infrared spectrometry (FTIR), UV-Visible spectrometry (UV-Vis), wide angle X-ray diffraction (WAXD), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and mechanical tests. The FTIR results indicate that the micro-phase separation and hydrogen bonding strength increase with increasing fluorine content, which are proved by the results of AFM and WAXD. The UV-Vis tests show high transmittance of FTPU films which is affected by crystallization easily. The TGA and mechanical tests indicate that thermal stability and mechanical properties of FTPU are improved significantly with the introduction of BPAF.

Influence of fluorine doping on the microstructure, optical and electrical properties of SnO2 nanoparticles

Tin dioxide (SnO2) is one of the most promising functional semiconductor materials; it has stimulated considerable research interest for its wide applications such as optoelectronic devices and solar cells technology. Undoped and fluorine doped tin oxide aerogel nanoparticles have been successfully synthesized by sol–gel route and dryed under supercritical conditions of ethanol. The effect of fluorine concentration on SnO2 nanoparticles properties was systematically investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, UV–Vis–IR spectroscopy and impedance spectroscopy. Characterization data showed that both pure SnO2 and FTO aerogels have a polycrystalline tetragonal rutile structure with a highly (110) plane preferred orientation. The grain sizes in the range of 11–25 nm were obtained depending on the elaboration conditions. Raman spectra show the fundamental peaks at 477, 632, and 782 cm−1, corresponding to the Eg, A1g, and B2g vibration modes, respectively, in good agreement with those for the rutile bulk SnO2. The optical band gap value of tin oxide decreases from 3.88 to 3.44 eV with the increase of fluorine content. Impedance spectroscopy results indicate that the electrical properties are strongly dependent on temperature and doping rate. These results show the strong correlation between the structural, morphological, optical and electrical properties of the samples depending on doping content which was well reflected on the quality of the nanoparticles.

Fluoride promoted crystallization and mechanical properties of Sr-fluorphlogopite glass

Crystallization, microstructure and mechanical behavior of strontium fluorphlogopite glass-ceramics, SrO·4MgO·Al2O3·6SiO2·2MgF2, was studied by varying the fluorine content. A number of glass-ceramics of each glass batch with excess MgF2 [SR0 (0% MgF2), SR5 (5% MgF2) and SR10 (10% MgF2)] were prepared by heating at its respective nucleation temperature followed by at different crystallization temperatures (780–1150°C). Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Micro Hardness Indenter were used to study the crystallization, microstructure and mechanical behavior of resulting three glass batches. DTA analysis revealed that the peak crystallization (Tp) and glass transition (Tg) temperatures decreased with increasing fluorine content that also lowers down the activation energy (E) as evident from crystallization kinetics. Hardness and fracture toughness values are higher for less fluorine containing glass-ceramics when they are treated isothermally. However, more fluorine based glass-ceramics is found to be more machinable than the less fluorine one.

Fluorinated Cu/Zn/Al/Zr hydrotalcites derived nanocatalysts for CO2 hydrogenation to methanol

A series of fluorinated Cu/Zn/Al/Zr hydrotalcite-like compounds are synthesized by incorporation of different amount of (AlF6)3− into hydrotalcite-like sheets. The fluorine-modified Cu/ZnO/Al2O3/ZrO2 catalysts are then obtained by calcination and reduction of fluorinated precursors. With increasing of F/Al atomic ratios, the Cu particle size increases continuously and the Cu surface area and dispersion decrease gradually, as well as the amount of moderately and strongly basic sites first increases significantly and then decreases. The catalytic performance for the methanol synthesis from CO2 hydrogenation is examined. The change of CO2 conversion is small when F/Al≤0.8, while the CO2 conversion decreases remarkably with further increase of fluorine content. It is also found that the CH3OH selectivity is closely related to the distribution of basic sites and the selectivity of CH3OH takes a volcanic trend with increased fluorine content. The introduction of suitable amount of (AlF6)3− into the hydrotalcite-like structure can enhance the methanol yield markedly and the fluorine-modified catalysts with F/Al=0.83 affords the substantial stability and the best catalytic performance.

Synthesis and surface properties of a new fluorinated acrylic diblock copolymer via AGET ATRP

A series of fluorinated diblock copolymers poly(2,2,3,4,4,4-hexafluorobutyl methacrylate)-b-poly(glycidyl methacrylate) PHFMA-b-PGMA with different fluorine content were synthesized by activator generated by electron transfer atom transfer radical polymerization (AGET ATRP). FTIR, 1H NMR and GPC data verified feasibility and controllability of the synthesis. In order to evaluate the effect of chain structure on the surface properties, corresponding homopolymer poly(2,2,3,4,4,4-hexafluorobutyl methacrylate) and random copolymer copoly(2,2,3,4,4,4-hexafluorobutyl methacrylate-r-glycidyl methacrylate) were also comparatively studied. Contact angle measurements indicated that the water and ethyleneglycol contact angles of block- and random copolymers increased with increase of fluorine content, but in different manner. This difference comes from different surface energy at the same fluorine content on film surface. The surface stability of block-copolymer was obviously better than that of random copolymer; the same results were observed in heat resistance tests.

Fluoride-assisted synthesis of anatase TiO2 nanocrystals with tunable shape and band gap via a solvothermal approach

A simple solvothermal approach employing oleic acid has been developed to prepare anatase TiO2 nanocrystals with different shapes, which were tuned from nanorods to nano-ellipsoids by increasing the amount of NaF from 0 to 0.5mmol, and the optical band gap decreased from 3.47eV to 3.29eV accordingly. However, when the fluoride was changed to NH4F, the resultant TiO2 nanocrystals possessed an anatase phase but were made up of smaller-sized nanocrystals and nanorods, and the band gap was increased to 3.53eV. The X-ray photoelectron spectroscopy (XPS) results illustrated an increase of fluorine content with an increasing amount of NaF could account for the variation of the shape and optical band gap of TiO2 nanocrystals. Moreover, the absence of fluorine content brought about less change of shape and increase of optical band gap of the product synthesized in the presence of NH4F. This result may offer another way to alter the shape and band gap of metal oxide nanocrystals with the assistance of fluoride.

Variations in structure and electrochemistry of iron- and titanium-doped lithium nickel manganese oxyfluoride spinels

Doping of cathode materials can considerably improve electrochemical performance and stability. Here, the high-voltage LiNi0.5Mn1.5O4 spinel is used as a candidate material. It is high-voltage cycling at a potential of approximately 4.7 V and the ability to host 2 eq. Li, thus leading to a theoretical capacity of 294 mAh g−1, that makes this material interesting. In order to improve stability and electronic conductivity, the spinel is doped with titanium and iron.Cycling in a voltage range of 2.0–5.0 V leads to a cooperative Jahn-Teller distortion accompanied by a phase transformation from cubic to tetragonal symmetry. This causes a severe capacity fade. To improve capacity retention, the as-prepared spinel is post-doped with fluorine. Influence of different fluorine amounts in LiNi0.5Mn1.4Fe0.1Ti0.027O4−xFx (x = 0–0.3) on the capacity and stability is analyzed. The initial capacities decrease with increasing fluorine content but the low voltage capacity is stabilized. Best electrochemical results are obtained with a fluorine content of x = 0.15. Furthermore, an additional redox couple is found. The intensity of this depends on the fluorine content. It is assumed that manganese, either in the tetrahedral sites or in octahedral sites, bound to fluorine lead to a higher voltage.

高硬質ナノ粒子添加ワックス素材の滑走特性評価

In Ski Jumping and Nordic Skiing, good gliding properties are required for success. Among many parameters, the tribological system is affected by the material properties of the ski running surface and various wax combinations that are applied on the top of the ski sole to minimize kinetic friction. The major research of this study has focused on the material changes due to the waxing process, in addition to the evaluation of the content of fluorine in waxes. Moreover, special attention has been paid to the additives like BN and SiC particles in nanometer size, mixed with high fluorine content waxes as powder. Characterization on the ski base materials, both with and without waxes, were evaluated by X-ray-fluorescence (XRF) analysis, Vickers hardness test, surface roughness analysis, contact angle measurement of water droplets, and tribometry to measure the coefficient of friction (C.O.F). It was found that the fluorine content in waxes on the top surface was not directly affected by the hardness, the surface roughness and the contact angle. The COF on ice was slightly lowered with the increase of fluorine content in waxes. The hardness was significantly improved by the addition of BN and SiC nanoparticles in high fluorine content waxes, especially twice as high as that for the case of BN nanoparticle, without any degradation in the surface roughness and the contact angle.

Simulations reveal the role of composition into the atomic-level flexibility of bioactive glass cements.

Bioactive glass ionomer cements (GICs), the reaction product of a fluoro-alumino-silicate glass and polyacrylic acid, have been in effective use in dentistry for over 40 years and more recently in orthopaedics and medical implantation. Their desirable properties have affirmed GIC's place in the medical materials community, yet are limited to non-load bearing applications due to the brittle nature of the hardened composite cement, thought to arise from the glass component and the interfaces it forms. Towards helping resolve the fundamental bases of the mechanical shortcomings of GICs, we report the 1st ever computational models of a GIC-relevant component. Ab initio molecular dynamics simulations were employed to generate and characterise three fluoro-alumino-silicate glasses of differing compositions with focus on resolving the atomic scale structural and dynamic contributions of aluminium, phosphorous and fluorine. Analyses of the glasses revealed rising F-content leading to the expansion of the glass network, compression of Al-F bonding, angular constraint at Al-pivots, localisation of alumino-phosphates and increased fluorine diffusion. Together, these changes to the structure, speciation and dynamics with raised fluorine content impart an overall rigidifying effect on the glass network, and suggest a predisposition to atomic-level inflexibility, which could manifest in the ionomer cements they form.

Absence of a stable atomic structure in fluorinated graphene.

Based on the results of first-principles calculations we demonstrate that significant distortion of graphene sheets caused by adsorption of fluorine atoms leads to the formation of metastable patterns for which the next step of fluorination is considerably less energetically favorable. Existence of these stable patterns oriented along the armchair direction makes possible the synthesis of various CFx structures. The combination of strong distortion of the nonfluorinated graphene sheet with the doping caused by the polar nature of C-F bonds reduces the energy cost of migration and the energy of migration barriers, making possible the migration of fluorine atoms on the graphene surface as well as transformation of the shapes of fluorinated areas. The decreasing energy cost of migration with increasing fluorine content also leads to increasing numbers of single fluorine adatoms, which could be the source of magnetic moments.

Increasing fluorine concentration to control the microstructure from fullerene-like to amorphous in carbon films

a-C:H:F films with different fluorine contents are deposited, leading to different microstructures being formed; including fullerene-like fragments, interlocking pores, and disordered structures.

Modes of Occurrence of Fluorine by Extraction and SEM Method in a Coal-Fired Power Plant from Inner Mongolia, China

In this study, an extraction method and environmental scanning electron microscopy (SEM) are employed to reveal the changes in the occurrence mode of fluorine in a coal-fired power plant in Inner Mongolia, China. The different occurrence states of fluorine during coal combustion and emission show that fluorine in coal mainly assumes insoluble inorganic mineral forms. The results illustrate that the three typical occurrence modes in coal are CaF2, MgF2 and AlF3. The fluorine in fly ash can be captured by an electrostatic precipitator (EPS) or a bag filter. In contrast, the gaseous fluorine content in flue gas is only in the range of several parts per million; thus, it cannot be used in this study. The occurrence mode of fluorine in bottom ash and slag is inorganic villiaumite (e.g., soluble NaF, KF and insoluble CaF2) which is difficult to break down even at high temperatures. The occurrence mode of fluorine with the highest content in fly ash is physically adsorbed fluorine along the direction of the flue gas flow. The insoluble inorganic mineral fluoride content in fly ash is also high, but the gradually increasing fluorine content in fly ash is mainly caused by physical adsorption. Fluorine in the coal-fired power plant discharges mostly as solid products; however, very little fluorine emitted into the environment as gas products (HF, SiF4) cannot be captured. The parameters used in this study may provide useful references in developing a monitoring and control system for fluorine in coal-fired power plants.

Preparation of fluoroalkylsilyl polymethacrylates and their waterproof application on cotton fabrics

Three novel fluoroalkylsilyl polymethacrylates, namely mono(fluoroalkyl)silyl polymethacrylate (PMFSA), bis(fluoroalkyl)silyl polymethacrylate (PBFSA) and tris(fluoroalkyl)silyl polymethacrylate (PTFSA), were synthesized via emulsion polymerization in this study. Subsequently, those fluoroalkylsilyl polymethacrylates were applied onto the surface of cotton fabric to make the fabric water-repellent. Particle size, zeta potential and transmission electron microscopy (TEM) were employed to analyze the emulsion stability and particle morphology. The surface properties of the coated cotton fabrics were confirmed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Thermal properties of fluoroalkylsilyl polymethacrylates and coated cotton fabrics were evaluated by thermal gravity analysis (TGA). Contact angle measurement (CA) demonstrated that the incorporation of more fluorinated segments into the fluoroalkylsilyl methacrylate comonomer molecule and increasing fluorine content can improve the water repellency of treated cotton fabrics. In addition, the fabric’s washing durability was found to be prominent. Even after 15 household machine washes, the water contact angles could be maintained as 132.7 °, 133.9 ° and 128.9 °, respectively.

Properties of fluorine-doped SnO2 thin films by a green sol–gel method

Fluorine doped tin oxide (FTO) films were fabricated on a glass substrate by a green sol–gel dip-coating process. Non-toxic SnF2 was used as fluorine source to replace toxic HF or NH4F. Effect of SnF2 content, 0–10mol%, on structure, electrical resistivity, and optical transmittance of the films were investigated using X-ray diffraction, Hall effect measurements, and UV–vis spectra. Structural analysis revealed that the films are polycrystalline with a tetragonal crystal structure. Grain size varies from 43 to 21nm with increasing fluorine concentration, which in fact critically impacts resultant electrical and optical properties. The 500°C-annealed FTO film containing 6mol% SnF2 shows the lowest electrical resistivity 7.0×10−4Ωcm, carrier concentration 1.1×1021cm−3, Hall mobility 8.1cm2V−1s−1, optical transmittance 90.1% and optical band-gap 3.91eV. The 6mol% SnF2 added film has the highest figure of merit 2.43×10−2Ω−1 which is four times higher than that of un-doped FTO films. Because of the promising electrical and optical properties, F-doped thin films prepared by this green process are well-suited for use in all aspects of transparent conducting oxide.

Highly fluorinated poly(1,3,4-oxadiazole-ether)s. structural, optical and dielectric characteristics

New fluorinated poly(1,3,4-oxadiazole-ether)s were prepared by nucleophilic aromatic substitution technique of an activated aromatic difluorinated compound with a bisphenol containing three trifluoromethyl groups, namely 1,1-bis(4′-hydroxyphenyl)-1-(3′,5′-ditrifluoromethylphenyl)-2,2,2-trifluoroethane, 1, or with a mixture of 1 and 9,9-bis(4-hydroxyphenyl)fluorene. FTIR and NMR spectroscopy were used to confirm the structure of the polymers. The polymers were easily soluble in organic solvents and could be processed in flexible thin films. The film surfaces exhibited hydrophobic characteristics, as it was determined by contact angle measurements. The polymers had high thermal stability, up to 440 °C, and glass transition temperature in the range of 202–237 °C. They showed fluorescence in the blue region, both in solution and in solid state. The change in electronic absorption and emission spectra of one of the polymer in neat and binary solvent mixtures has been studied. Broadband dielectric spectroscopy was used to investigate the relaxation processes in polymers. The dielectric constant of the polymers was in the range of 2.84–2.96, at 100 °C and 10 kHz, and decreased with the increase of fluorine content.

Adsorption Property of Silicone Rubber Sticking Chuck for OLED Glass Substrate

Manufacturing process of OLED contains adsorption-desorption process of glass substrate. There are several adsorption methods of glass substrate such as atmospheric pressure, vacuum and electrostatic adsorption. However, these methods are very complex to connect system. Therefore, the adsorption method using silicone rubber based sticking chuck was proposed in this study. Three types of silicone rubbers having 0, 19.3 and 32.2 wt% of fluorine were used and their mechanical properties, surface energies and adsorption properties were examined. According to the results σ300 and hardness increased with increasing fluorine contents, but elongation was decreased. Also, fluorosilicone rubber containing 32.2 wt% of fluorine showed the lowest surface tension, among three types of rubber and resulted in the highest initial tack with glass substrate. After the adsorption-desorption test of 300,000 cycles was performed, the adsorption force of S-1 (silicone rubber) decreased largely from 2.34 to 0.73 MPa. However, the S-3 (fluorosilicone rubber having 32.2 wt%. of fluorine) decreased only from 3.15 to 2.24 MPa. From this study, we obtained the valuable equations related to long term durability of silicone based sticking chuck. Finally the transfer of silicone rubber to glass substrate with the adsorption-desorption process was not occurred and this phenomenon was examined by UV-Visible spectroscopy.

Measurements of fluorine in contemporary urban Canadians: a comparison of the levels found in human bone using in vivo and ex vivo neutron activation analysis

Non-invasive in vivo neutron activation analysis (NAA) was used to measure the fluorine concentration in 35 people in Hamilton, Ontario, Canada. Measurement and precision data of this second generation NAA system were determined in 2013, and the results were compared with the performance of a first generation system used in a pilot study of 33 participants from the Hamilton area in 2008. Improvements in precision in line with those predicted by phantom studies were observed, but the use of fewer technicians during measurement seemed adversely to affect performance. We compared the levels of fluorine observed in people between the two studies and found them to be comparable. The average fluorine concentration in bone was found to be 3 ± 0.3 mg and 3.5 ± 0.4 mg F/g Ca for 2013 and 2008 measurements respectively.Ten people were measured in both studies; the observed average change in bone fluorine in this subgroup was consistent with that predicted by the observation of the relationship between bone fluorine and age in the wider group. In addition, we observed differences in the relationship between bone fluorine level and age between men and women, which may be attributable either to sex or gender differences. The rate of increase in fluorine content for men was found to be 0.096 ± 0.022 mg F/g Ca per year while the rate of increase for women was found to be slightly less than half that of men, 0.041 ± 0.017 mg F/g Ca per year. A discontinuity in the rate of increase in fluorine content with age was observed in women at around age 50. Bone fluorine content was significantly lower () in women age 50 to 59 than in women age 40 to 49, which we suggest may be attributable to bone metabolism changes associated with menopause. We also observed increased fluorine levels in tea drinkers as compared to non-tea drinkers, suggesting tea may be a significant source of exposure in Canada. The rate of increase in fluorine content of the tea drinkers and the non-tea drinkers were found to be 0.127 (± 0.029) and 0.050 (± 0.009) mg F/g Ca per year respectively. Finally, we also obtained twelve bone samples from cadavers’ skulls. Neutron activation analysis was used to determine the fluorine levels in these ex vivo samples. The rate of increase of fluorine content versus age for in vivo and ex vivo measurements were found to be 0.078 ± 0.014 and 0.078 ± 0.050 mg F/g Ca per year respectively. Excellent agreement was found between the fluorine levels determined in vivo and ex vivo using the two separate systems, providing confidence in the fluorine concentration data being measured in vivo.