Papers by Author: Jin Hong Li

Abstract: Mullite nanocomposites powders have been successfully synthesized from pretreated coal gangue via hydrothermal crystallization process. The mullite nanocomposites powders are investigated and charactered by laser particle size analysis, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) analysis, selected area electron diffraction (SAED) analysis and energy-dispersive X-ray (EDX) analysis. Moreover, the reaction mechanism of this process is speculated according to MAS-NMR results. It is indicated that mullite nanocomposites powders can be prepared at 80-90 °C for 3 h with NaOH concentration of 2-4 mol/L and L/S ratio (liquid/solid ratio in mass) of 10 mL/g by using calcined coal gangue as precursor. The agglomerate powder size of D50 is about 3.83-4.71 mm. Furthermore, some imperfective puncheon-shaped crystals exist among a large number of whole puncheon-shaped crystals which are about 30-70 nm in length and about 10-20 nm in diameter. MAS-NMR analysis indicates that the nano-size mullite grow around the central atom-Al, Si of [AlSi]O4 tetrahedral and the growth unit Al[OH]4- exist in this process definitely.

Abstract: Using coal fly ash from one thermal power plant in Ningxia, China as the raw material, aluminum hydroxide powder was successfully extracted by pre-desilication , calcination, dissolution and carbonation precipitation processes. The research results indicated that the mullite, Quartz and glass phase in the coal fly ash could be changed into NaSiO3, NaAlO2 and Na2CaSiO4 after the coal fly ash was treated by desilication and calcination. The SiO2and Al2O3 components in the coal fly ash were mainly separated by dissolving the calcined sample using water. The dissolution rate of Al2O3 from the calcined sample is 91%. The aluminum hydroxide powder extracted from the coal fly ash is bayerite with the particle size of more than 50m. The extraction rate of the aluminum hydroxide from the coal fly ash can be up to 83%.

Abstract: The hydration heat of aluminate cement containing magnesium aluminate spinel (MA-spinel) and Commercial Lafarge cement are studied. The results show that five stages exist in the hydration processes of both cements, e.g. pre-induction, induction, acceleration, deceleration and stabilization stage. The N values of the two cements are both lower than 1 in acceleration stage, on the contary higher than 1 in stabilization stage. As a result, the hydration is mainly controlled by nucleation reaction and diffusion process in acceleration stage and stabilization stage respectively. The hydration heat of aluminate cement containing MA-spinel is lower than Lafarge cement. Accordingly, the hydration rate of aluminate cement containing MA-spinel is slower than that of Lafarge cement.

Abstract: NaY zeolite molecular sieves have been synthesized using diatomite as a main starting material via a hydrothermal method. In this approach, the mixture of diatomite and Na₂CO₃ in mass ratio of 1.0/1.46 was first calcined at temperature of 830 °C for about 1.5 h. The calcined materials were then dissolved in water to obtain a solution and the composition is 15.1 Na₂O : 1 Al₂O₃ : 11.5 SiO₂ : 832 H₂O. The solution was used to synthesize NaY zeolite by the crystals seeds (27.76Na₂O·1.00Al₂O₃·25.07SiO₂·305.66H₂O) via hydrothermal treatment. The hydrothermal temperature is 100 °C and the percentage of added crystal seeds is 10% (volume) relative to calcined materials. The obtained zeolite was identified by X-ray diffraction (XRD), and was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and nitrogen sorption analysis, which showed that a high yield of NaY type with a high crystalinity was obtained.