Preparation And Characterization Of Poly Aluminum Bromide At 75℃ And Crystal Structure Of Poly Aluminum Nitrate

The main purpose of aluminum morphology is to figure out the various poly aluminum forms and the transition process of them when Al3+ hydrolyzed in water. But among all kinds of analysis methods, poly aluminum crystal structure analysis is the most important and trustable method to get the exact structure and make sure the real existence of poly aluminum forms. Therefore, trying to get more structure of Al hydroxide species has vital significance. In this thesis, poly aluminum bromide and poly aluminum nitrite system were chosen in order to obtain much more new poly aluminum species even the single crystal or pure product of them, and then we can easily analyze their structures with the method of crystallographic analysis.In this thesis, the solid-liquid equilibrium diagram of AlBr3—Al2O3—H2O at 75℃was drawn by means of wet dregs. And under the guidance of the phase diagram, three poly aluminum bromide products were prepared. They were Al5Br3(OH)12·6H2O, AlBr(OH)2·2H2O and Al4(OH)6(H2O)12Br6·2Al(H2O)8Br3 with the purity of 80.92%,99.68% and 99.99% respectively. And the first two poly aluminum species were characterized by Chemical analysis, Powder XRD phase analysis, Infrared spectroscopy and Thermal analysis.Crystal structure of AlBr(OH)2·2H2O had been analyzed with the Rietveld method. The result shows that AlO6 octahedras connect with each other by sharing edges and finally form a zigzag chain extending infinitely. This kind of one-dimensional linear structure helps to reveal the formation and transition mechanism of poly aluminum species.Single crystal of poly aluminum nitrate has been synthesized and its structure was analyzed. The poly cation's structure is similar to that of poly aluminum chloride and iodide, that is,7 octahedra formed a plank by sharing edges and surrounded by 6 octahedra. Although they all formed the "turtle-style" structure, the flip angle of the P-Al13 nitrite was significantly larger than P-Al13 hydrochloride (21°) and iodide (23.6°). The structure of poly aluminum nitrate, proved that the "plank-suspending "structure exists commonly.In addition, in this paper, the resonance peaks of P-Al13 solution's 27Al NMR spectra were clearly assigned and we put forward the transformation rule from P-Al13 to K-Al13 when the concentration increases and the certain pH range in which the transformation can proceed.