In this thesis, CNF were extracted by means of (2, 2, 6, 6-tetramethylpiperidin-1-yl) oxidanyl (TEMPO) oxidation and aqueous counter collision (ACC) methods. The CNF extracted by TEMPO method exhibited needle shape and extremely short. CNF extracted by the ACC method have different morphology depending on the pretreatment process. CNF extracted by TEMPO oxidation and ACC combination method exhibited the best results. With 60 minutes of TEMPO oxidation and 30 passes of ACC treatment, the extracted CNF showed the best results. However, size of the extracted CNF suspension is diverse. Therefore, the fractionation of the extracted CNF is necessary.
The centrifugal fractionation was introduced by utilizing an ultracentrifuge machine with three steps: 1) dilute the CNF suspension, 2) centrifuge the diluted CNF suspension under low speed to remove non-fibrillated fibers, 3) centrifuge under high speed to separate very small CNF the suspension. And a uniform CNF suspension was successfully fractionated from the extracted CNF suspension.
In order to well understand the mechanical properties of CNF and its nanocomposites, the mechanical properties of single CNF were tested by using atomic force microscope (AFM) 3-points bending test. Hardwood (HW), softwood (SW), bamboo (BA) and cotton (CO), four kind samples were evaluated. Young’s modulus of the tested CNF was found to be in the range of 88-110 GPa.
Drop casting method and doctor blade casting method were utilized to fabricate the pure CNF film. The results showed that the doctor blade cast pure CNF film exhibited higher mechanical properties than the drop cast one. The ultrathin CNF film was also fabricated by means of microfabrication. The morphology exhibited layered structure with high transparency. Piezoelectric force microscopy (PFM) test was performed to analyze the piezoelectricity of ultrathin CNF film. The CNF were successfully reinforced in the PVA matrix. As increasing the concentration of CNF, the mechanical properties of PVA-CNF nanocomposites increased.
Two different ZnO-CNF nanocomposites were made: Zinc oxide nanoparticles coated CNF nanocomposite (ZNPC) and Zinc oxide nanorods grown CNF nanocomposite (ZNRC). The nanocomposites were characterized by means of UV-visible spectroscopy, SEM, AFM, LCR meter and tensile test machine combined with a picoammeter. The ZNRC was applied for UV detecting sensor in terms of UV photo response behavior. The performance of UV detecting sensor was evaluated with respect to ZnO concentration, UV irradiance intensity, electrode effect and UV irradiance exposure side. The results proved that the ZNRC can be utilized as a good UV detecting sensor.