Etudes microstructurales et propriétés thermodynamiques de quelques Kaolins locaux et d’un nanocomposites.

Abstract

"In this work, we have studied two kaolins taken from distend places. The first one denoted DD1 consists of two main phases (kaolinite and halloysite) and the other KT2 whose main constituents are kaolinite, quartz and mica. We have studied, by differential scanning calorimetry, four samples based on fluoroplastic containing different concentrations of thermally expanded graphite (GTD) for various dispersions. Our choice was set on the component Kaolinite which is present in both materials. Lorentz-Polarization correction was carried out prior to the diffraction data, which has been achieved using LWL program. The true profile was extracted using this program. The methods used for the microstructural analysis of the constituents in the two kaolins are the Warren-Averbach and the Williamson-Hall methods. Scherrer's relationship has been applied in cases where the compound is devoid of strains. The study revealed that the Kaolinite of DD1 is devoid of micro constraints, while Kaolinite of KT2 incorporates the strains. This was confirmed by the Williamson-Hall method as well as Fourier analysis. The evaluation of strains in the kaolinite of KT2 has been performed by the methods of Warren-Averbach and the Williamson-Hall diagram. The average value of this constraint found by the first method is about 0.22, whereas as the second method gives as a value of 0.28. The average size of crystallites of the Kaolinite in DD1 was found be about 111Å obtained by the method of Warren-Averbach and 118 Å obtained by the method of Williamson-Hall, while, the size of crystallites in KT2 was 92 Å and 127 Å using the two methods respectively. The study of the size distribution showed that the dominant size of kaolinite in DD1 and KT2 is about 40 Å (41%) and 43 Å (42%), respectively. The purpose of this work is the study, by differential scanning calorimetry, four samples based on fluoroplastic containing different concentrations of thermally expanded graphite (GTD) for various dispersions. We noticed that the heating rate present an important role. Increasing the heating rate from 5 to 10 and then to 15 °C/min, affords the behavior of our calorimetry nanocomposite whose the concentration and/or the dispersion. All curves contain a calorimetric anomaly the shape and intensity depend on the concentration and dispersion. The temperature of the calorimetric anomaly varies from a sample to another. We have shown that the nanomaterial containing the smallest concentration of GTD with high dispersion heated with the biggest heating rate will degrade at high temperatures. It is more resistant to thermal shocks. The introduction of GTD in a polymer matrix improved the thermal properties of the nanocomposite and its use becomes possible in a wide range of temperature."