Coating HA/Fe³⁺ On Alumina Fiber Through Layer-by-layer Self-assembly And Carbonization Study After Coating

Various kinds of carbon material like carbon fiber are applied on many fields, and they are the study hot spots in current days. Humic acid(HA) is a excellent carbon resource with rich reserve amount and comparatively large specific surface area. Exploring the developing and applying of HA on carbon material has the practical meaning and bright prospect. We coat HA on alumina fiber using layer-by-layer (LBL) method and then carbonize the film with fiber matrix. Study the effects of solution concentration of Fe3+ and layer number on the film thickness. We analyze the coating products by using FTIR, FESEM, EDX and ICP-EDX. The results demonstrate that the HA we use is quite possibly purified from coal, alumina micro fibers can successfully immobilize HA through surface hydroxyl–OH groups, and the thickness of film differentiate with the solution concentration of Fe3+ and the number of film. In addition, affluent micro pores of HA can be observed from HRTEM, the EDX result shows that Na+, Cl- which don't participate in reaction can be washed away during the cleaning process of LBL, and the loadings of HA and Fe can be obtained by using ICP-EDX testing technology with experiment and calculation. After the coating products are carbonized, the carbonization products are characterized by FESEM, EDX, XRD and Raman techniques. The analysis results indicate that the carbonization products and micro- morphology of products differ greatly with different carbonization temperature; the Fe3+ complexed with HA transform into various iron oxides, simple substance Fe and Fe3C; the degree of graphitization and order of carbon materials become high with the carbonization temperature, but the product obtained at 800℃carbonization temperature is amorphous carbon, and the graphitization and order degree of the carbon material are still low at 1000℃carbonization temperature, in addition, the film get reformed at high temperature, which makes the morphology of the film become neater and more order. All products under different carbonization temperature have rich micro pores, and the diameters of super-micro pores increase with the rise in carbonization temperature. Besides, we obtain by-product of carbon nano hollow sphere. These hollow sphere's graphitization and order degree are higher than those of carbon material with the same carbonization condition, and their diameters are between decades and hundreds nanometers.