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111.
Electrochemical behavior of gold and its associated minerals in alkaline thiourea solutions 下载免费PDF全文
Electrochemical measurements were conducted to study the electrochemical behavior of gold (Au) and its commonly associated minerals in alkaline thiourea solutions. The results indicated that without addition of any stabilizer, selective dissolution of Au from stibnite and pyrite was only possible at relatively low thiourea concentrations. As Na2SiO3 was added, pyrite started to become active and an oxidation peak appeared; the oxidation peaks of arsenopyrite and chalcocite appeared earlier than that of Au. The chalcocite peak shifted in the positive direction and the peak current increased. Stibnite did not show an oxidation peak and its current was nearly zero. Adding Na2SiO3 favored the selective dissolution of Au when its minerals were associated with chalcocite and stibnite. At pH 12, the Au anode dissolution peak current increased with stabilizer concentration. At 0.38 and 0.42 V and for Na2SiO3 concentration below 0.09 M, the current density continuously increased with Na2SiO3 concentration. The Na2SiO3 concentration had to be adequate to stabilize thiourea. When the potential was higher than 0.42 V, the surface of the Au electrode started to passivate. With an additional increase in potential, the presence of Na2SiO3 could not stop the inevitable decomposition of thiourea. 相似文献
112.
The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray (5wt% NaCl solution). A formation model of γ-FeOOH and a transformation model describing the conversion of γ-FeOOH to α-FeOOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-FeOOH into α-FeOOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products. 相似文献
113.
Improvement of microstructure and corrosion properties of friction stir welded AA5754 by adding Zn interlayer 下载免费PDF全文
This study investigated the effect of Zn foil layers on the microstructure and corrosion characteristics of friction stir welded aluminum alloy 5754. Samples of various joints were prepared by applying different rotational and welding speeds, and their microstructures were evaluated via a metallographic technique and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy elemental analysis. The anticorrosion behavior of joints in the absence and presence of a Zn interlayer was studied by cyclic potentiodynamic polarization test in 3.5wt% NaCl aqueous solution, and sound welds were obtained in the presence of the Zn interlayer foil. The results revealed that the joint made at a rotational speed of 800 r/min and traveling speed of 15 mm/min achieved a chemical composition identical to that of aluminum alloy 7xxx series, and as such, it showed the best resistance to corrosion. 相似文献
114.
Alkaline digestion behavior and alumina extraction from sodium aluminosilicate generated in pyrometallurgical process 下载免费PDF全文
Bo-na Deng Guang-hui Li Jun Luo Jing-hua Zeng Ming-jun Rao Zhi-wei Peng Tao Jiang 《矿物冶金与材料学报》2018,25(12):1380-1388
In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na2O constituents, which alters the leaching behaviors of Al2O3 and SiO2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100-120℃, liquid-to-solid ratio (L/S) of 10:2 mL/g, caustic ratio of 4, and Na2O concentration of 240 g/L, the actual and relative digestion ratio of Al2O3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al2O3-rich material derived from reductive roasting of bauxite and comprising Na1.75Al1.75Si0.25O4 was conducted; the relative digestion ratio of Al2O3 attained 90% at 200℃. 相似文献
115.
Process mineralogy characteristics of acid leaching residue produced in low-temperature roasting-acid leaching pretreatment process of refractory gold concentrates 下载免费PDF全文
Shuang-hua Zhang Ya-jie Zheng Pan Cao Chao-hui Li Shen-zhi Lai Xing-jun Wang 《矿物冶金与材料学报》2018,25(10):1132-1139
To provide a theoretical basis for a suitable process to extract gold from refractory gold concentrates, process mineralogy on the acid leaching residue of gold calcine was studied by chemical composition, X-ray diffraction, scanning electron microscopy-energy spectrum, and mineral dissociation analysis. The results showed that the acid leaching residue contained Au 68.22 g/t, Ag 92.71 g/t, Fe 0.44%, As 0.10%, and S 0.55%. Gold and silver minerals existed as native gold, argentite, and proustite. Quartz, the main gangue mineral, accounted for 78.33wt/%. The dissociation degree analysis showed that the proportions of monomer and exposed gold in acid leaching residue were 96.66wt%. The cyanidation results showed that the cyanide gold leaching rate of acid leaching residues was close to 100wt%. However, the maximum cyanide gold leaching rate of gold calcine was only 85.31wt%. This suggests that acid leaching can increase the gold dissolution rate in the cyanide process. 相似文献
116.
Effect of Ce addition on microstructures and mechanical properties of A380 aluminum alloy prepared by squeeze-casting 下载免费PDF全文
The effect of cerium (Ce) addition on the eutectic Si, β-Al5FeSi phase, and the tensile properties of A380 alloy specimens prepared by squeeze-casting were studied by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The experimental results showed that Ce more effectively modified the eutectic Si and refined the β-Al5FeSi. The refinement effect significantly increased under a specific pressure of 100 MPa with the addition of Ce from 0.1wt% to 0.9wt%. In contrast, the average length and the aspect ratio of the eutectic Si and β-Al5FeSi exhibited their optimal values when the content of the added Ce was greater than 0.5wt%. Needle-like Al8Cu4Ce was precipitated with the addition of excessive Ce; hence, the mechanical properties of A380 gradually decreased with increasing Ce content in the range from 0.3wt% to 0.9wt%. 相似文献
117.
New testing methodology for the quantification of rock crushability: Compressive crushing value (CCV) 下载免费PDF全文
Crushing is a size reduction process that plays a key role in both mineral processing and crushing-screening plant design. Investigations on rock crushability have become an important issue in mining operations and the manufacture of industrial crusher equipment. The main objective of this research is to quantify the crushability of hard rocks based on their mineralogical and mechanical properties. For this purpose, the mineralogical, physical, and mechanical properties of various hard rocks were determined. A new compressive crushing value (CCV) testing methodology was proposed. The results obtained from CCV tests were compared with those from mineralogical inspections, rock strength as well as mechanical aggregate tests. Strong correlations were found between CCV and several rock and aggregate properties such as uniaxial compressive strength (UCS), the brittleness index (S20), and aggregate impact value (AIV). Furthermore, the relationship between the mineralogical properties of the rocks and their CCVs were established. It is concluded that the proposed testing methodology is simple and highly repeatable and could be utilized as a pre-design tool in the design stage of the crushing process for rock quarries. 相似文献
118.
Complementation in the composition of steel slag and red mud for preparation of novel ceramics 下载免费PDF全文
Yan-bing Zong Wen-hui Chen Yong Fan Tai-lin Yang Zhao-bo Liu Da-qiang Cang 《矿物冶金与材料学报》2018,25(9):1010-1017
A method for preparing novel ceramics was developed in this study. Different ratios red muds were added to steel slags to optimize the preparation of novel ceramics by a traditional ceramic preparation process. The sintering mechanism, microstructure, and performance were studied by X-ray diffraction techniques, scanning electron microscopy, and combined experiments of linear shrinkage, water absorption, and flexural strength. The results confirmed that red mud can reduce the volumetric instabilities through the complementarity of red mud and ferroalloy slag. The crystal phases in the ceramics are all pyroxene group minerals, including diopside ferrian, augite, and diopside. The flexural strength of the ceramic that contains 40wt% red mud and was prepared at the optimal sintering temperature (1140℃) is greater than 93 MPa; its corresponding water absorption is less than 0.05%. 相似文献
119.
Leaching behavior of V,Pb, Cd,Cr, and As from stone coal waste rock with different particle sizes 下载免费PDF全文
This paper investigates the leaching behavior of heavy metals (V, Pb, Cd, Cr, and As) from stone coal waste rocks with various particle sizes using dynamic leaching experiments. The results show that the dissolved concentrations of V and As initially increased and then slightly decreased as time progressed and that the dissolved concentrations of Pb, Cd, and Cr were high in the early stage before decreasing. The particle size of the stone coal waste rocks strongly influenced the heavy metal concentration in the leaching solutions. The effects of the particle size of the stone coal waste rocks on the dissolved concentrations of V, Pb, and As decreased in the order fine fraction > medium fraction > coarse fraction, and the effects of particle size on the dissolved concentrations of Cr and Cd decreased in the order medium fraction > coarse fraction > fine fraction and coarse fraction > medium fraction > fine fraction, respectively. The quantities of heavy metals dissolved from the stone coal waste rock with fine particle sizes were observed to decrease in the order V (17104.36 μg/kg) > As (609.41 μg/kg) > Pb (469.24 μg/kg) > Cr (56.35 μg/kg) > Cd (27.52 μg/kg), and the dissolution rates decreased in the order As (2.96%) > Pb (0.93%) > V (0.35%) > Cd (0.25%) > Cr (0.01%). The specific surface area, pore size of the stone coal waste rocks, and chemical forms of heavy metals also influenced the release of heavy metals from the stone coal waste rocks. Kinetic analysis showed that the dissolution of heavy metals fundamentally agreed with the rate equation controlled by the shrinking core model. The results of this study are expected to serve as a reference for the evaluation of heavy metals contamination from stone coal waste rocks. 相似文献
120.
Microstructural characterization and oxidation resistance of multicomponent equiatomic CoCrCuFeNi-TiO high-entropy alloy 下载免费PDF全文
CoCrCuFeNi-TiO was prepared by arc melting of the pure elements and Ti2CO powder under an Ar atmosphere. Both CoCrCuFeNi and CoCrCuFeNi-TiO alloys are composed of a face-centered cubic (fcc) solid solution, whereas the alloys of CoCrCuFeNi-TiO are basically composed of an fcc solid solution and TiO crystals. The microstructures of CoCrCuFeNi-TiO are identified as dendrite and interdendrite structures such as CoCrCuFeNi. The morphology of TiO is identified as an equiaxed crystal with a small amount of added Ti2CO. By increasing the amount of Ti2CO added, the TiO content was dramatically increased and part of the equiaxed crystals changed to a dendrite structure. A test of the oxidation resistance demonstrates that the oxidation resistance of CoCrCuFeNi-TiO is better than that of CoCrCuFeNi. However, as the TiO content increases further, a corresponding decrease is observed in the oxidation resistance. 相似文献