High Temperatur Resistant Materials for Potential Aerospace Applications

Abstract

Carbon nanotubes (CNT) have enormous application in various fields such as sensors, aerospace, super capacitors and photovoltaic devices, etc. These are also extensively exploited for number of other energy and environmental applications now-a-days. As, the rapid development and evolution in the field of aerospace industry, the existing developed technologies do not have adequate potential to overpower the requirements and demands of the new era. Nanocomposites based on CNT have procured significant attention in recent years for their applications in aircrafts, military crafts, missile and spacecraft due to advanced properties such as thermal stability, chemical stability, huge surface area etc. This thesis is mainly focused on the use of CNT based polymer nanocomposites as thermally stable materials for aerospace applications. The CNT are first modified by the attachment of copper (Cu) and silver (Ag) nanoparticles (NPs) to enhance the conductivity of the nanocomposites. The polymers which are in-situ polymerized in the surface of modified CNT are polypyrrole (PPy), polythiophene (PTh) and polyaniline (PANi), further more the amino acids were incorporated in the nonocomposites to study the change on the thermal conductivity of the final material. The CNT hybrids are incorporated in bisphenol A diglycidyl ether (DGEBA) by using ethyl cellulose as hardener. The final product was obtained in the form of films. The structural and morphological properties of prepared nanocomposites were exploited by X-Ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy Dispersive Spectroscope (FESEM-EDX), Thermal Analysis (TGA/DSC), X-ray photoelectron spectroscopy (XPS), two prob electrical conductivity measurements with change in temperature and Fourier Transform Infra Red Spectroscopy (FTIR). The synergetic effect of metal NPs and polymer attachment on CNT tailored the morphological and bulk superficial properties of the samples. CuNPs and AgNPs induced ii structural changes, enhancement of the conductivity of the materials. However, CNT with both AgNPs and CuNPs demonstrated efficient thermal conductivity. The maximum decomposition temeperature when polymers are incorporated in the nanocomposites was observed for the PANi. Whereas after the incorporation of the amino acids, the maximum decompositions temperature was observed for the sample containing cysteine (Cys) with AgNPs and CuNPs. The parameters that affect the thermal conductivity of the prepared nanocomposites are the attachment of NPs on the surface of CNT, CNT defects, thickness of the in-situ polymerized polymer on the surface of CNT, the type of physical interaction between CNT, NPs, Polymers and amino acids. The electrical conductivity within the temperature range of 110- 250° was calculated. The best thermal conductivity with change in temperature was obtained for the sample containing Cys, PANi, AgNPs. The reason is the best physical interactions between the constituents of the nanocompoisites. Hence, the thermal resistance of the prepared nanocomposites with in the range of 110-250°C which is much higher than the neat epoxy i.e. 110°C after which DGEBA can’t be used for any application as the structure starts to decompose, suggested that these materials as good candidates for use in aerospace industry for various applications and can resolve many problems among which cost and weight are very important.