Impact of preparation methods on dielectric and mechanical properties of graphene-epoxy nanocomposites
Notice bibliographique
Résumé
Proper dispersion of graphene in epoxy is essential for enhancing nanocomposite properties and requires control of processing methods. Here, epoxy/graphene composites (E/G, 1% wt) were prepared via solution mixing. To evaluate the effect of additional dispersion treatments, the graphene/acetone suspensions before mixing with epoxy, or uncured E/G samples, were further mixed using an ultrasonic bath (UB) or ultrasonic probe (UP). The rheological properties of the uncured materials were analyzed performing small amplitude oscillatory shear (SAOS). The morphology of the cured samples was observed by optical microscopy and their electrical and mechanical properties by broadband dielectric spectroscopy, and dynamic mechanical analysis (DMA) respectively.The modulus of the composites varied depending on the treatment applied. Untreated E/G exhibited a lower storage modulus (G') at low frequencies compared to the neat epoxy. This is attributed to the slippage of aggregates within the composite, a phenomenon known as ""lubrication effect."" UB treatment of the E/G composite did not significantly impact G'. Conversely, applying UB (1 h) to the graphene/acetone suspension increased G’, indicating an improved graphene distribution, favored by processing at lower viscosity that may facilitates the ultrasonic wave propagation. Microscopy images confirmed reduced agglomerates, though average particle size remained unchanged.UP treatment was more effective, leading to a higher G' after 10 minutes at 25% amplitude. However, excessive UP treatment (75% amplitude for 30 minutes) reduced G'. The lower G' is associated with graphene sheet fragmentation, as observed in microscopy images showing reduced sheet size, potentially compromising reinforcement. Direct UP application to the E/G composite led to polymer degradation.The dielectric properties of neat epoxy and E/G composites were analyzed using a combination of Havriliak-Negami function and a conductivity term to take into account charge fluctuations. The relaxation time of the dipolar processes was further modeled with the Vogel-Fulcher-Tammann equation, providing the activation energy of the ?-relaxation mechanisms, reflecting molecular mobility restrictions. While untreated E/G showed activation energy similar to that of neat epoxy, UB treatment increased activation energy, suggesting improved graphene dispersion and greater restriction of molecular motion of the epoxy chains. This was confirmed by DMA, which showed increased storage modulus, loss modulus, and glass transition temperature, indicating a more rigid polymer with enhanced filler-matrix interactions.In conclusion, this study highlights the importance of optimizing processing parameters. The UP(25%-10min) applied to the graphene suspension improved the dispersion without fragmenting the sheets, resulting in higher activation energy and improved dynamic mechanical properties.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».