| X-ray diffraction is an important common structural characterization equipment ofmaterials analysis, it is widely used in aerospace, materials, energy, chemicals andautomotive fields. Now, with the rapid development of materials science and relatedfields of science and technology, we are in an urgent demand for fine-structure underhigh temperature, low temperature, reaction atmosphere and other environments.Therefore, the development of the corresponding X-ray attachment has a broad marketprospect. X-ray window is one of the most important parts of the X-ray diffraction,under the vacuum condition, the design principle of the X-ray window is to minimizethe thickness of the window and use low atomic number materials to achieve a highX-ray transmittance. Given the toxicity of beryllium (Be) window and the limitedapplication of the diamond window, it is hard to widespread use in new applicationareas of the X-ray. Therefore, we are in an urgent need for a new material to replace thetraditional beryllium window when the X-ray structure has been widely used to studymaterials.In this thesis, carbon nanotube reinforced polyimide composite the new X-raywindow was prepared by in situ polymerization. Carbon nanotubes were dispersed bysonication technique, the curing process of the polyamic acid film was analysised bythermogravimetric analyzer(TGA) and differential scanning calorimetry(DSC), themicrostructures of the composite films were studied by X-ray diffraction (XRD),fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy(SEM), the tensile properties, thermal stability and X-ray transmittance of the compositefilms were analysised.The result of the curing process shown that polyamic acid film were divided intothree phases, including solvent evaporation, imidization and structural improvement, theaggregation structure of the polyamic acid was amorphous, after that there appeardsome ordered crystal structure during the curing process, but the polyimide was stillamorphous after imidization.The investigation on the microstructure shown that carbon nanotubes weredispersed homogeneously in the polyimide matrix when the content of the carbonnanotubes was appropriate. The X-ray diffraction peaks of carbon nanotubes andpolyimide were unchanged in composite films and FT-IR spectra of composite filmswere almost same as that of pure polyimide, this shown that carbon nanotubes did notaffect the thermal imidization of polyamic acid.The investigation on the tensile properties shown that the Tensile strength andYoung’s modulus of the composite films were improved with the incorporation ofamount of carbon nanotubes，the maximum value for the Tensile strength and the Young’s modulus of the composites at3wt%carbon nanotubes loading were increasedby36%and28%at room temperature tensile test and29%and43%at250℃tensile testover the neat polyimide film, respectively. All this indicate the strong interfacialinteraction between the carbon nanotubes and the polyimide matrix. This was becausethat the carbon nanotubes were well dispersed in the polyimide matrix and the stronginterfacial interaction between the carbon nanotubes and the polyimide matrix. It isbeneficial to improve the bearing capacity in a high vacuum of the X-ray window, sothat we can improve the X-ray transmittance by reducing the thickness of the window.The investigation on the thermal stability shown that the thermal stability of thecomposite films increased with the incorporation of the carbon nanotubes. The initialthermal decomposition temperature of the composite films were more than500℃andthe glass transition temperature were greater than330℃. It could meet the heatresistance of the X-ray window accessories.The investigation on the X-ray transmittance shown that the line absorptioncoefficient of the composite films was7.97cm-1when the content of carbon nanotubeswas3wt%, which could be comparable to Be X-ray window. It was still more than80%that the X-ray transmittance of the polyimide films with a thickness of250μm. It isbeneficial to enhance the strength of the received signal and noise ratio of the detectorwith high X-ray transmittance. |
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