| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 105 === With the concern of the environment and status of energy, renewable energy, energy conservation and other topics have been more and more attracted by many researchers. Solar energy is one of the most promising renewable energy. How to effective utilization of solar energy has become a significant problem. In conventional solar thermal collectors, plates or tubes coated with a layer of absorbing material were used to absorb solar energy, and then this energy was carried away in the form of heat by working fluids. Carbon black is a kind of material that has very good absorption in the whole sunlight wavelength range. The materials added to the working fluid could effectively improve solar energy utilization. However, the carbon black particles surface have strong van der waals forces and makes it easy to aggregate to limit its application. The method of surface modification could improve the dispersion property of carbon black. Among that surface oxidation modification in liquid phase is the major attention because of simple process and good dispersion effect.
In this study, we used hydrogen peroxide as an oxidant to oxidize carbon black. Four kinds of carbon black powder, which trade mark are M900, M1000, M1100, and Mogul L, were studied in this work. And then we used ultrasonic bath to disperse as-modified carbon black in water without dispersant. In the experiment, we characterized as-modified carbon black surface property by thermal gravimetric analysis (TGA), X-ray photoelectron spectroscope (XPS) and Fourier transform infrared spectroscopy (FTIR) ; and analyzed carbon black suspension dispersion stability and morphology of particles by ultraviolet-visible absorption spectroscopy (UV-Vis), dynamic light scattering (DLS), transmission electron microscopy (TEM). As shown in the results, we summarized the following remarks:
(1)As measured from the TGA and XPS, the oxygen content of as-modified carbon black M1000, Mogul L, M1100 and M900 increased by 14%, 2%, 9%, 10%, respectively, which are dependent on the different molecular structure and properties of carbon black.
(2)As observed from the XPS C1s spectra and FTIR analysis, we confirmed that after the H2O2 treatment on carbon black, the carbon black surface contained C-O, C=O and O-H functional groups. These functional groups were used to confirm the success of hydrogen peroxide modification for carbon black.
(3)According to the observation from TEM, the oxidation modification of hydrogen peroxide improves the dispersion and stability of carbon black in water due to the polarity on carbon black surface. The secondary mean particle size of carbon black (M1000, Mogul L, M1100, M900) was decreased from 376, 251, 369, 194 nm to 156, 154, 103, 114 nm, respectively.
(4)As measured by UV-Vis, when the concentration of as-modified carbon black Mogul L 0.001, 0.005, 0.010, 0.025 g dm-3, the UV-Vis light absorption value of dispersion were 0.07, 0.26, 0.60, 1.43, respectively, which result from that the dispersed carbon black particles increased in the solution.
(5)According to Beer’s law, the extinction coefficients of as-modified carbon black (M1000, Mogul L, M1100, M900) dispersion in water were increased from 102.4, 37.6, 22.8, 6.8 g-1 dm2 to 433.6、544.8、264.4、180 g-1 dm2, respectively, compared to as-present carbon blacks, where extinction coefficient of carbon black Mogul L was remarkable increased due to stronger hydrophilic property and good stability in water.
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