Fluorination Conditions Research Articles

Flexible fluorinated graphite foils with high contents of the (C2F)n phase for slow neutron reflectors.

In order to prepare self-standing and flexible slow neutron reflectors made of graphite fluoride (GF) with high contents of (C2F)n structural phase, graphite foils of different thicknesses were used as starting materials for gas (F2)/solid fluorination. The maximal interlayer distance of GF was obtained with this phase thanks to the stacking sequence FCCF/FCCF; this is mandatory for the efficient reflection of slow neutrons. 71 and 77% of the (C2F)n phase were achieved for graphite foils with thicknesses of 1.0 and 0.1 mm, respectively. The interlayer distances were 8.6 Å as expected. The fluorination conditions (static mode, a long duration of 24 h, annealing in pure F2 gas for 24 h, and temperatures in the 390-460 °C range) were adapted to large pieces of graphite foils (7 × 7 cm2) in order to both avoid exfoliation and achieve a homogeneous dispersion of fluorine atoms. This process was also efficient for thinner (0.01 mm thick) graphitized graphene oxide foil. 56% of the (C2F)n phase and an interlayer of 8.6 Å were achieved for this foil when fluorination was performed at 430 °C. Whatever the nature and the thickness of the foil, their flexibilities are maintained.

High Energy Density Primary Lithium Battery with Fluorinated S-Doped Graphene

Sulphur-doped graphene was fluorinated using molecular fluorine (F2). First, the fluorination conditions were adapted in order to be mild enough to maintain S in the carbon lattice and form S-F bonds. An unusually weakened C-F bonding for an F/C ratio of 0.71 was then achieved, which allowed enhanced performances when used as a cathode in primary lithium batteries. The material prepared at a moderate fluorination temperature of 70 °C for a period of 60 min exhibits a high mid-discharge reduction potential of 3.11 V at 10 mA/g and a power density of 3605 W/kg at a discharge rate of 2C. These electrochemical properties make the fluorine/sulfur co-doped graphene a promising material.

2‐Nitroimidazole Based PET Tracers: Development of a General Synthetic Approach and Fluorination Methodology

Abstract2‐Nitroimidazole based PET tracers are widely used for non‐invasive hypoxic tumor diagnosis. In this context, we report here a general method based on a central Mitsunobu reaction to easily access 2‐nitroimidazole precursors. Optimization of fluorination conditions is described and successfully applied to the radiofluorination of the 2‐nitroimidazole precursors. Moreover, the radiosynthesis of a new potential hypoxia PET tracer is also described. Finally, this article presents a SFC analytical method allowing both an easy monitoring of the fluorination reactions and the measurement of partition coefficients (logP).

Fluorination and its Effects on Electrocatalysts for Low‐Temperature Fuel Cells

AbstractThe benefits of covalent grafting of fluorine atoms onto carbonaceous materials are described for the design of new electrocatalysts for low‐temperature fuel cells. In order to obtain the best results, the fluorination conditions must be carefully chosen according to the physicochemical properties of the starting materials (specific surface area, pore size distribution, crystallinity, and doping). By describing the main fluorination routes, the article aims to help in the choice of efficient treatment conditions. The effects of fluorination on the performance of the platinum group metal (PGM)‐based catalyst and the non‐PGM‐based electrocatalyst are discussed. Finally, future research prospects and technical challenges of fluorination for fuel cells are proposed.

CF4 plasma-based atomic layer etching of Al2O3 and surface smoothing effect

Plasma-based Al2O3 atomic layer etching (pALE) has a reaction mechanism similar to thermal Al2O3 ALE (tALE). The main difference between the two methods is that pALE uses plasma instead of HF in tALE to fluorinate Al2O3 to AlF3. In this study, the CF4 plasma source commonly used for dry etching is combined with a self-developed low-ion-bombardment remote Al2O3 plasma-based ALE system to obtain Al2O3 plasma fluorination conditions, and then the AlCl(CH3)2 (dimethylaluminum chloride) precursor is used to develop the pALE Al2O3 process. In addition to using x-ray photoelectron spectroscopy to investigate ideal fluorination conditions of CF4 plasma for Al2O3 films and establishing the linear etching rate curves of pALE at different process temperatures (250–400 °C), we used atomic force microscopy to analyze the surface morphology of the Al2O3 films after dry etching and pALE. We showed that pALE can smooth Al2O3 films with a root mean square surface roughness of 1.396–0.655 nm and used anodic aluminum oxide substrates with nanotrench structures to demonstrate that pALE can improve the surface roughness of nonplanar structures.

Hydrophobic-Hydrophilic Properties and Characterization of PIM-1 Films Treated by Elemental Fluorine in Liquid Perfluorodecalin.

A direct fluorination technique was applied for the surface treatment of PIM-1 films in a liquid phase (perfluorodecalin). The fluorinated samples were analyzed by various instrumental techniques. ATR-IR spectroscopy showed that the fluorination predominantly takes place in methylene- and methyl-groups. Cyano-groups, aromatic hydrogens and the aromatic structure of the PIM-1 repeat unit were shown to be relatively stable at the fluorination conditions. XPS confirmed that the concentration of fluorine, as well as oxygen, in the near surface layer (~1 nm) increases with fluorination time. C1s and O1s surface spectra of the fluorinated PIM-1 samples indicated an appearance of newly-formed C-F and C-O functional groups. Scanning electron microscopy and X-ray energy-dispersive spectroscopy of the fluorinated PIM-1 samples showed an increase of the fluorine concentration at the surface (~0.1-1 μm) with the treatment duration. Analysis of the slices of the PIM-1 films demonstrated a decline of the fluorine content within several microns of the film depth. The decline increased with the fluorination time. A model of fluorine concentration dependence on the film depth and treatment duration was suggested. A change in the specific free surface energy as a result of PIM-1 fluorination was revealed. The fluorination time was shown to affect the surface energy (γSV), providing its shift from a low value (25 mJ∙m-2), corresponding to tetrafluoroethylene, up to a relatively high value, corresponding to a hydrophilic surface.

Fluorination of silyl prosthetic groups by fluorine mediated silyl ether linker cleavage: a concept study with conditions applicable in radiofluorination

BackgroundPositron emission tomography (PET) is a powerful tool in medical imaging, especially in combination with the PET radionuclide fluorine-18 that possesses optimal characteristics. For labelling of biomolecules and low-molecular weight tracers, fluorine-18 can be covalently bound to silicon by either nucleophilic replacements of leaving groups (like ethers) or by isotope exchange of fluorine-19. While nucleophilic substitutions require additional purification steps for the removal of contaminants, isotope exchange with fluorine-18 results in low molar activity. Both challenges can be addressed with a detagging-fluorination of an immobilized silyl ether motif.ResultsBy overcoming the susceptibility towards hydrolysis, optimized detagging conditions (improved reaction time, fluorination reagent, linker, and resin) could afford the highly sterically hindered silyl fluoride motifs, that are commonly applied in radiochemistry in small and semipreparative scales. The described reaction conditions with fluorine-19 are transferrable to conditions with [18F]fluoride and silyl fluorides were obtained after approx. 10 min reaction time and in high-purity after mechanical filtration.ConclusionsWe present a proof-of-concept study for a detagging-fluorination of two silyl ethers that are bound to an optimized amino alcohol resin. We show with our model substrate that our solid-phase linker combination is capable of yielding the desired silicon fluoride in amounts sufficient for biological studies in animals or humans under standard fluorination conditions that may also be transferred to a radiolabelling setting. In conclusion, our presented approach could optimize the molar activity and simplify the preparation of radiofluorinated silyl fluorides.

Oxidative Fluorination of Heteroatoms Enabled by Trichloroisocyanuric Acid and Potassium Fluoride.

In synthetic method development, the most rewarding path is seldom a straight line. While our initial entry into pentafluorosulfanyl (SF5) chemistry did not go according to plan (due to inaccessibility of reagents such as SF5Cl at the time), a “detour” led us to establish mild and inexpensive oxidative fluorination conditions that made aryl‐SF5 compound synthesis more accessible. The method involved the use of potassium fluoride and trichloroisocyanuric acid (TCICA)—a common swimming pool disinfectant—as opposed to previously employed reagents such as F2, XeF2, HF, and Cl2. Thereafter, curiosity led us to explore applications of TCICA/KF as a more general approach to the synthesis of fluorinated Group 15, 16, and 17 heteroatoms in organic scaffolds; this, in turn, prompted SC‐XRD, VT‐NMR, computational, and physical organic studies. Ultimately, it was discovered that TCICA/KF can be used to synthesize SF5Cl, enabling SF5 chemistry in an unexpected way.

Oxidative Fluorination of Heteroatoms Enabled by Trichloroisocyanuric Acid and Potassium Fluoride

AbstractIn synthetic method development, the most rewarding path is seldom a straight line. While our initial entry into pentafluorosulfanyl (SF5) chemistry did not go according to plan (due to inaccessibility of reagents such as SF5Cl at the time), a “detour” led us to establish mild and inexpensive oxidative fluorination conditions that made aryl‐SF5compound synthesis more accessible. The method involved the use of potassium fluoride and trichloroisocyanuric acid (TCICA)—a common swimming pool disinfectant—as opposed to previously employed reagents such as F2, XeF2, HF, and Cl2. Thereafter, curiosity led us to explore applications of TCICA/KF as a more general approach to the synthesis of fluorinated Group 15, 16, and 17 heteroatoms in organic scaffolds; this, in turn, prompted SC‐XRD, VT‐NMR, computational, and physical organic studies. Ultimately, it was discovered that TCICA/KF can be used to synthesize SF5Cl, enabling SF5chemistry in an unexpected way.

DC Flashover Performance of GIS Spacers Fluorinated at Different Temperatures

In order to verify the effectiveness of direct fluorination in improving the dc flashover performance of gas insulated switchgear (GIS) actual spacers and explore the effect of fluorination conditions, 126-kV disk spacers were surface fluorinated in the laboratory at the different temperatures of 35 °C, 55 °C, or 80 °C. The evaluation of surface physicochemical characteristics and basic electrical properties of the fluorinated disk spacers are realized by using the epoxy samples of the same material and simultaneously fluorinated with the disk spacers. Flashover tests indicate that direct fluorination significantly increases the dc flashover voltage of the actual spacer in SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> gas and reduces the dispersion of flashover voltage, fluorination temperature has a significant effect on the enhancement of the flashover voltage, and the fluorination at higher temperatures can produce a larger improvement in the flashover performance. In addition, these fluorinated spacers can withstand heat treatment at 120 °C, with unchanged flashover performance. Infrared analysis and scanning electron microscopy observation show that the fluorination at different temperatures changes surface chemistry of the disk spacer substantially, forming the fluorinated layers with different thicknesses, compositions, and structures. Measurements of surface conductivity and surface potential decay consistently show that direct fluorination increases surface conduction of the spacer, and the fluorination at higher temperatures leads to a more significant increase in surface conduction. The improvement in dc flashover performance, caused by direct fluorination, is mainly attributed to the suppression of surface charge accumulation by the increase in surface conduction of the spacer.

Enhanced microwave absorption property of ferroferric Oxide: The role of magnetoelectric resonance

• Direct fluorination was applied to decorate Fe 3 O 4 . • Core–shell fluorinated Fe 3 O 4 was fabricated by controlling the fluorination conditions. • The microwave absorption property of Fe 3 O 4 was enhanced after fluorination. • Electromagnetic wave dissipation model of magnetoelectric resonance was proposed. • The in-depth mechanism of magnetoelectric resonance was elucidated. The modification of ferrites can effectively improve their microwave absorption (MA) properties. However, attempts to improve their high-frequency performance were still limited and considerably cumbersome for practical application. Herein, we present a facile method that effectively improves the MA behavior of Fe 3 O 4 through direct fluorination using F 2 /N 2 gas. Specifically, we fabricated core–shell structured fluorinated Fe 3 O 4 (F-Fe 3 O 4 ) with a fluorine-doped shell and an unmodified Fe 3 O 4 core by carefully controlling the F 2 concentration and fluorination temperature. We found a unique ‘magnetoelectric collaborative resonance’ (MDR) effect in F-Fe 3 O 4 , manifested by the co-occurrence of double dielectric and magnetic resonance peaks at 14.8 and 16.6 GHz. Band gap measurements and molecular simulations results indicated that the smaller energy gap derived from fluorine doping facilitates both electron hopping between the mixed-valence Fe 2+ /Fe 3+ states and electron accumulation at the core–shell interface, which induce simultaneous magnetic exchange interactions and the Maxwell–Wagner effect (interface polarization). As a result, the incident electromagnetic wave can be dissipated via magnetic exchange resonance coupled with dielectric resonance, thereby improving the MA properties at the same frequency of MDR. Compared with those of pristine Fe 3 O 4 , the minimum reflection loss of F-Fe 3 O 4 was four times higher, reaching −64.9 dB, and the effective absorption bandwidth was 5.03 GHz, which is almost 1.6 times higher. We believe this facile and effective modification method and the unique loss mechanism of MDR will advance the structural design of high-performance MA materials.

Optical absorption and photoluminescence of partially fluorinated graphite crystallites

Fluorinated graphene-like materials are currently attracting much attention due to the tuning of their properties by changing the fluorine content and pattern on the graphene lattice. In this work, we report the redshift of absorption bands and the suppression (increase) of green (yellow-orange) photoluminescence (PL) in the spectra of transparent CFx crystallites as x decreases from ∼0.44 to ∼0.33. Time-dependent density functional theory (TDDFT) calculations reveal that the aromatic regions and polyene chains in the CFx layers are mainly responsible for the optical absorption of the samples in the ultraviolet and visible regions, respectively. The electron-hole recombination within branched aromatic rings or long carbon chains produces orange-red emission, while green-yellow PL is due to transitions of excited polyene electrons to half-occupied levels of aromatic carbon. Our results show that the optical properties of partially fluorinated graphite layers are determined by the size and shape of the remaining sp2 carbon regions, which can be varied by changing the fluorination conditions.

Improved cardiovascular risk stratification with PET: [18F]meta-fluorobenzylguanidine as a potential cardiac radiotracer

Background and Hypothesis: &#x0D; Cardiovascular disease is the leading cause of death in the United States each year, exceeding 600,000 deaths and costing over $200B. Sympathetic dysfunction in cardiac tissue has been shown to occur in patients with recent cardiac injury or longstanding disease. The SPECT radiotracer, meta-[123I]iodobenzylguanidine (MIBG), has been used to image neuroendocrine tumors as well as global cardiac sympathetic tone through the human norepinephrine transporter-1. We will determine the utility and improved imaging the PET radiotracer meta-[18F]fluorobenzylguanidine (MFBG) can afford in cardiac care. MFBG has shown several improvements over MIBG in neuroendocrine tumors but has proven difficult to reliably synthesize. &#x0D; Project Methods: &#x0D; A novel synthetic pathway of MFBG utilizing copper accelerated Sandmeyer fluorination conditions is being developed to streamline its radiosynthesis from seven manipulations and an unstable precursor to four with more stable intermediates. &#x0D; We also explored where MFBG may be useful in cardiology by performing a literature review through the PubMed MeSH database published after 2010. &#x0D; Results: &#x0D; We have developed a new MFBG precursor in one step from commercially available compounds and a one-pot automated radiosynthesis is currently in development. This improves upon current methods and may provide increased clinical availability of MFBG for future studies. &#x0D; MIBG has shown prognostic value for the incidence of severe cardiac events but cannot provide any local innervation data. The PET radiotracer, [11C]hydroxyephedrine, can display local denervation within the myocardium. However, its 20.3 minute half-life prevents its widespread use beyond hospitals with direct access to a radiochemistry laboratory. To our knowledge, no cardiac imaging has been investigated using MFBG. &#x0D; Conclusion and Potential Impact: &#x0D; We believe MFBG could provide similar improvements to cardiac imaging as in neuroendocrine tumors. With a novel synthetic method being developed, we hope to begin pre-clinical imaging studies and provide future cardiologists with a new prognostic imaging modality which can direct personalized care to patients with cardiovascular disease.

PET Imaging for Dynamically Monitoring Neuroinflammation in APP/PS1 Mouse Model Using [18F]DPA714.

Background: In the pathogenesis of Alzheimer's disease (AD), microglia play an increasingly important role. Molecular imaging of neuroinflammatory targeting microglia activation and the high expression of 18-kDa translocator protein (TSPO) has become a hot topic of research in recent years. Dynamic monitoring neuroinflammation is crucial for discovering the best time point of anti-inflammatory therapy. Motivated by this, Positron emission tomography (PET) imaging in an APP/PS1 mouse model of AD, using 18F-labeled DPA-714 to monitor microglia activation and neuroinflammation, were performed in this paper.Methods: We prepared [18F]DPA714 and tested the biological characteristics of the molecular probe in normal mice. To obtain a higher radiochemical yield, we improved the [18F]-fluorination conditions in the precursor dosage, reaction temperature, and synthesis time. We performed [18F]DPA714 PET scanning on APP/PS1 mice at 6–7, 9–10, 12–13, and 15–16 months of age, respectively. The same experiments were conducted in Wild-type (Wt) mice as a control. Referring to the [18F]DPA714 concentrated situation in the brain, we performed blocking experiments with PK11195 (1 mg/kg) in 12–13-months-old APP/PS1 mice to confirm the specificity of [18F]DPA714 for TSPO in the APP/PS1 mice. Reconstructed brain PET images, fused with the Magnetic Resonance Imaging (MRI) template atlas, and the volumes of interests (VOIs) of the hippocampus and cortex were determined. The distribution of [18F]DPA714 in the brain tissues of 15–16-months-old APP/PS1 and Wt mice were studied by immunofluorescence staining.Results: Through the reaction of 18F, with 2 mg precursor dissolved in 300 ul acetonitrile at 105°C for 10 min, we obtained the optimal radiochemical yield of 42.3 ± 5.1% (non-decay correction). Quantitative analysis of brain PET images showed that the [18F]DPA714 uptake in the cortex and hippocampus of 12–13-months-old APP/PS1 mice was higher than that of the control mice of the same age (cortex/muscle: 2.77 ± 0.13 vs. 1.93 ± 0.32, p = 0.0014; hippocampus/muscle: 3.33 ± 0.10 vs. 2.10 ± 0.35, p = 0.0008). The same significant difference was found between 15- and 16-months-old APP/PS1 mice (cortex/muscle: 2.64 ± 0.14 vs. 1.86 ± 0.52, p=0.0159; hippocampus/muscle: 2.89 ± 0.53 vs. 1.77 ± 0.48, p = 0.0050). Immunofluorescence staining showed that the activation of microglia and the level of TSPO expression in the cortex and hippocampus of APP/PS1 mice were significantly higher than Wt mice.Conclusion: [18F]DPA714, a molecular probe for targeting TSPO, showed great potential in monitoring microglia activation and neuroinflammation, which can be helpful in discovering the best time point for anti-inflammatory therapy in AD.

Direct fluorination of acetyl and ethyl celluloses in perfluorinated liquid medium

Direct fluorination of acetyl- and ethylcelluloses was performed in a bubble reactor with liquid perfluorinated medium (perfluorodecalin). Concentrated fluorination mixtures (F2 + N2) and long reaction times (up to 3 h) were used for better control of the degree of fluorination than it was made previously in direct gaseous fluorination of polymers. The fluorine consumption in the runs with both polymers only slightly increased with increasing temperature and fluorine concentration in the gas mixture. Fluorine content in the fluorinated polymers did not depend strongly on the fluorination conditions. X-ray analysis, differential scanning calorimetry of the fluorinated samples showed no significant changes in respect of the initial polymers. However, emergence of novel and splitting of initial absorption bands, the change of polarization of C–O bonds in IR spectra for the fluorinated samples were observed. It can directly and indirectly justify the appearance of the C–F bonds in the side groups and glycopyranosyl ring of the fluorinated substituted celluloses.19F, 13C solid NMR spectroscopy of the fluorinated samples confirm hydrogen-substituted fluorination of methyl groups.

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations

AbstractWhile halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional‐group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive‐free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations.

While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional‐group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive‐free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.

Synthesis and Characterization of SrFexMn1-x(O,F)3-δ Oxide (δ = 0 and 0.5) and Oxyfluoride Perovskite Films.

We report the synthesis and characterization of as-grown SrFexMn1-xO2.5 epitaxial films, which were also subjected to postgrowth oxidation and topotactic fluorination to obtain SrFexMn1-xO3 and SrFexMn1-xO2.5-δFγ films. We show how both the B-site cation and anion composition influence the structural, electronic, and optical properties of this family of perovskite materials. The Fe substitution of Mn in SrMnO2.5 gradually expands the c-axis parameter, as indicated by X-ray diffraction. With increasing x, the F content incorporated under identical fluorination conditions increases, reaching its maximum in SrFeO2.5-δFγ. In the compounds with mixed B-site occupation, the Fe 2p photoemission peaks are shifted upon fluorination, while the Mn 2p peaks are not, suggesting inductive effects lead to asymmetric responses in how F alters the Mn and Fe bonds. Electronic transport measurements reveal all compounds are insulators, with the exception of SrFeO3, and demonstrate that fluorination increases resistivity for all values of x. Optical absorption spectra in the SrFexMn1-xO2.5 and SrFexMn1-xO3 films evolve systematically as a function of x, consistent with a physical scenario in which optical changes with Fe substitution arise from a linear combination of Mn and Fe 3d bands within the electronic structure. In contrast, the F incorporation induces nonlinear changes to the optical response, suggesting a more complex impact on the electronic structure in materials with concurrent B-site and anion site substitution.

Nucleophilic (Radio)Fluorination of Redox-Active Esters via Radical-Polar Crossover Enabled by Photoredox Catalysis.

We report a redox-neutral method for nucleophilic fluorination of N-hydroxyphthalimide esters using an Ir photocatalyst under visible light irradiation. The method provides access to a broad range of aliphatic fluorides, including primary, secondary, and tertiary benzylic fluorides as well as unactivated tertiary fluorides, that are typically inaccessible by nucleophilic fluorination due to competing elimination. In addition, we show that the decarboxylative fluorination conditions are readily adapted to radiofluorination with [18F]KF. We propose that the reactions proceed by two electron transfers between the Ir catalyst and redox-active ester substrate to afford a carbocation intermediate that undergoes subsequent trapping by fluoride. Examples of trapping with O- and C-centered nucleophiles and deoxyfluorination via N-hydroxyphthalimidoyl oxalates are also presented, suggesting that this approach may offer a general blueprint for affecting redox-neutral SN1 substitutions under mild conditions.

Comparative study on direct fluorination and surface properties of alumina-filled and unfilled epoxy insulators

In view of the significant performance improvement of unfilled epoxy insulators by direct fluorination, and the fact that all spacers in SF 6 gas insulated systems are alumina-filled epoxy composites, to promote the application of the method for improving the performance of epoxy spacers, in this paper, alumina-filled epoxy (composite) and unfilled epoxy (pure) samples were prepared with the same formulation and process as those for epoxy spacers. The pure and composite epoxy samples were fluorinated under the same conditions, and comparative studies were performed on their surface physicochemical characteristics and properties. IR analysis and SEM imaging show no obvious influence of alumina particles on the fluorination of the epoxy matrix under the used fluorination conditions, while many nanoparticles and agglomerates appear on the surface and large microsized particles in the SEM imaging depth become less visible after the composite epoxy sample was fluorinated. Contact angle and electrical property measurements indicate that like the pure epoxy sample, surface hydrophilicity and surface conduction of the composite epoxy sample are also increased by the fluorination, while the increase in surface hydrophilicity or surface conduction is more significant or less significant, compared to the pure epoxy sample. All these are associated with the fluorination of the alumina particles and the interface change or reconstruction between the particles and the matrix.