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1.
Bauxite residue is a highly alkaline waste containing soluble alkaline anions, which can cause environmental concerns. The optimal leaching conditions, distribution of alkaline anions, types of pivotal alkaline anions and their dissolution behaviors were investigated based on the combination of single factors-orthogonal experiments and leaching stage experiment. Using a two-stage leaching, 86% of the soluble alkaline anions (CO32?,HCO3?,Al(OH)4?,OH?) were leached with a L/S ratio of 2 mL/g, at 30 °C, over 23 h. During the first stage of leaching, approximately 88% of alkaline anions were leached from the dissolution of free alkali (NaOH, carbonate, bicarbonate, NaAl(OH)4) with the rest originating from the dissolution of alkaline minerals (calcite, cancrinite and hydrogarnet). Supernatant alkalinity was 69.78 mmol/L with CO32? accounting for 75%. Furthermore, carbonate leaching was controlled by solid film diffusion using the Stumm Model with an apparent activation energy of 10.24 kJ/mol.  相似文献   

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This study focused on leaching behavior of alkaline anion and sodium in bauxite residue through ammonium chloride treatment. The results showed that the pH of bauxite residue decreased from 10.49 to 8.93, total alkaline anion ( HCO3?,CO32?, OH?, A1O2?) concentration reduced from 38.89 to 25.50 mmol/L, leaching rate of soluble sodium was 80.86% with ammonium chloride addition of 0.75%, liquid/solid (L/S) ratio of 3 (mL/g), temperature of 30 °C and reaction time of 18 h; L/S ratio was the main factor affecting the removal of alkaline anion and the leaching of sodium. Furthermore, ammonium chloride promoted the dissolution of diaspore and changed the micro/morphological characteristics with the increase of massive structure. The findings of this work will contribute to achieve soil-formation of bauxite residue.  相似文献   

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The edge-to-edge matching (E2EM) crystallographic model was used to predict the orientation relationships (ORs) between LaB6 and Al. Three different possible ORs can be predicted between LaB6 and Al, which are (100)Al6(100)LaB6, [001]Al6[001]LaB6; (110)Al6(110)LaB6, [001]Al6[001]LaB6; and (111)Al6(111)LaB6, [011¯]Al6[011¯]LaB6. The prediction results are perfectly confirmed through TEM analysis and prove the nucleation potency of LaB6. The refining efficacy of Al-2La-1B refiner and its influence on the tensile properties were investigated in the as-cast Al-7Si-0.3Mg alloy. According to the results, LaB6 has higher nucleation potency than TiB2, leading to better grain refining efficacy of Al-2La-1B refiner in the as-cast Al-7Si-0.3Mg alloy. Regarding the mechanical performances, tensile properties of the as-cast Al-7Si-0.3Mg casting alloy are prominently improved after addition of Al-2La-1B refiner, due to the refined microstructures.  相似文献   

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In the first part, an extensive overview is given over the thermodynamic information for the nickel–phosphorus system which is available in the literature. In the second part, phosphorus vapor pressure measurements over nickel–phosphorus alloys are described for which an isopiestic method was employed. Data points were obtained between 33.82 and 44.40 at% P in the temperature interval from 977 to 1325 K. Based on these measurements partial thermodynamic properties and integral Gibbs energy values were determined. The standard molar Gibbs energy of formation of Ni5P4 for the temperature range 977–1042 K was obtained as:ΔfGmo(Ni5P4)(s)±9.8/(kJmol?1)=?632.1+0.2136T/K  相似文献   

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《Acta Materialia》2007,55(6):2173-2182
Three-dimensional simulations of grain growth in thin films containing finely dispersed second-phase particles were performed using a phase field model. The simulations show that although the growth behavior of the columnar grain structures in thin films is essentially two-dimensional, the interaction between the particles and the grain boundaries is three-dimensional. Grain boundaries can therefore more easily break free from the particles than in purely two-dimensional systems, resulting in fewer grain boundary–particle intersections and a larger final grain size. For a given volume fraction fV and size of the particles r, the final grain size R¯lim increases with film thickness. Moreover, it was found that particles located in the middle of the film are most efficient in pinning grain boundaries. A classical Zener type relation R¯lim/r=K(1/fVb) cannot describe these effects.  相似文献   

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