The Influence Of Surface Nano-structure On The Optical Properties Of Composite Powder

It is well known that micro/nano core/shell composite has higher hiding ability andwhiteness than single nano or micro material, but few study has focused on themechanism of the enhancement of these properties in the core/shell composite structure.In this dissertation, the micro/nano CaCO3(NCC/GCC) and GCC/nano TiO2core/shellstructures were prepared by spin coating, and the relationships between coatingthickness and optical performance in these two structures were investigated accordingly.The NCC was prepared by chemical deposition through the Ca(OH)2-H2O-CO2reactionsystem at10oC, and the nano TiO2was obtained by the hydrolyzation of TiOSO4at85oC. The NCC and nano TiO2were spin coated to the calcite substrate separately, and thecoating thickness was controlled by the spin coating speed. The results of investigationsof optical properties indicate that the coating thickness of NCC and nano TiO2shouldbe controlled in the range of0.3and0.1μm, respectively. It is found that the sampleshave better optical performance with the <001> calcite substrate. The test resultsdemonstrate that the core/shell composite structure is helpful to enhance the hidingability and whiteness. The relationship between the coating thickness and thereflectance was simulated and investigated by the CST MICROWAVE STUDIO, andthe results verified the effect of core/shell composite structure. The mechanism ofenhancement of hiding ability and whiteness in the core/shell composite structure werealso investigated by analysis of the simulation results. It is found that the core/shellcomposite structure elevate the refractive index of the system, and prevent theagglomeration of nano particles, which eventually lead to the hiding ability andwhiteness improvement compared with single nano or micro material.In addition, the nano TiO2/graphite fiber (GF)3D structure was prepared throughsol-gel process, and its photocatalytic and photoelectrochemical properties wereinvestigated. The composite structure was optimized by reaction time control, and thisstructure were characterized by Raman, XPS, UV-VIS and PL. The UV-VIS testsindicated that the nano TiO2/GF structure were better than nano TiO2in ultravioletabsorption. The degradation tests were performed with TO2/GF and nano TiO2. It isfound that the composite structure achieves the highest degradation efficiency. Thedegradation rate are0.023C0,0.018C0,0.022C0, and0.016C0m-2for degrading of MO,RhB, MB and PL, which is100~130%and200~300%higher than P25and TiO2. The repeating of degradation tests indicated that the composite structure has goodphotocatalytic stability. The photoelectrochemical tests show that the current densitiesare141Acm-2and37Acm-2with an illumination area of1cm-2, and the photoelectricconversion efficiency are1.48%and0.37%for TiO2/GF and single TiO2.