氧化矾作为非制冷微测辐射热计的热敏材料,电阻率ρ和电阻温度系数TCR(Temperature Co-efficient of Resistance)是表征其性能的重要参数。通过对用离子束溅射得到的氧化矾薄膜在相同时间不同温度下的N2+H2退火实验,我们发现氧化矾薄膜...氧化矾作为非制冷微测辐射热计的热敏材料,电阻率ρ和电阻温度系数TCR(Temperature Co-efficient of Resistance)是表征其性能的重要参数。通过对用离子束溅射得到的氧化矾薄膜在相同时间不同温度下的N2+H2退火实验,我们发现氧化矾薄膜的电阻率ρ和电阻温度系数TCR之间存在着密切的正相关关系,AES结果表明它们的变化对应着氧化矾热敏材料的O/V比例(或氧空位浓度)的变化。这三个参量随着退火温度的改变而变化,在350～500 ℃的退火温度范围内,我们发现电阻率ρ,电阻温度系数TCR以及O/V比例随着温度的变化均出现一个峰值。通过对氧化矾的电阻温度特性的分析,我们讨论了氧化矾薄膜的导电机制。我们认为,用本方法制备的氧化矾薄膜在室温下导电的载流子主要来自于相对较深能级杂质的电离。展开更多
Magnetite concentrate was recovered from ferrous sulphate by co-precipitation and magnetic separation. In co-precipitation process, the effects of reaction conditions on iron recovery were studied, and the optimal rea...Magnetite concentrate was recovered from ferrous sulphate by co-precipitation and magnetic separation. In co-precipitation process, the effects of reaction conditions on iron recovery were studied, and the optimal reaction parameters are proposed as follows： n（CaO）/n（Fe2＋） 1.4：1, reaction temperature 80 ℃, ferrous ion concentration 0.4 mol/L, and the final mole ratio of Fe3＋ to FJ＋ in the reaction solution 1.9-2.1. In magnetic separation process, the effects of milling time and magnetic induction intensity on iron recovery were investigated. Wet milling played an important part in breaking the encapsulated magnetic phases. The results showed that the mixed product was wet-milled for 20 min before magnetic separation, the grade and recovery rate of iron in magnetite concentrate were increased from 51.41% and 84.15% to 62.05% and 85.35%, respectively.展开更多
Due to the environmental policies and economic reasons,the water used in some flotation operations of complex sulfide ores is recirculated,causing the ion concentration of some species to increase over time,affecting ...Due to the environmental policies and economic reasons,the water used in some flotation operations of complex sulfide ores is recirculated,causing the ion concentration of some species to increase over time,affecting the flotation of the minerals of interest.In this work,an experimental and thermodynamic analysis of the synthetic solutions was presented with a high content of calcium and sulfate ions.The study focused on evaluating the use of two aluminum compounds for the precipitation of Ca^(2+)and SO_(4)^(2−)in the form of ettringite.The amorphous aluminum hydroxide was found to be more efficient than the crystalline one,giving rise to 83%calcium and 91%sulfate removal.The XRD analysis of the solids showed the main reaction product of ettringite,accompanied by small amounts of calcite,due to the absorption of atmospheric carbon dioxide.The final solution after the chemical treatment showed residual calcium and sulfate concentrations below 200 mg/L.Finally,the kinetics of calcium removal appeared to correspond to a second order reaction with respect to calcium concentration,with an apparent activation energy of 53.48 kJ/mol,which may suggest that the ettringite precipitation process is governed by the chemical reaction.展开更多
Stress corrosion cracking (SCC) and anticorrosion measures of TU42C weld-joint were studied by constant load experiments and pickling experiments. The results show that in 40%(mass fraction) NaOH solution at 110℃, ca...Stress corrosion cracking (SCC) and anticorrosion measures of TU42C weld-joint were studied by constant load experiments and pickling experiments. The results show that in 40%(mass fraction) NaOH solution at 110℃, caustic SCC occurs in TU42C weld-joints at the applied potential of-1020mV(vs SCE) for 3d while at the potential of-950mV(vs SCE) for 10d. All the cracks are intergranular. In the 10% sulfuric acid, the cracks have the most negative self-corrosion potential-432.5mV(vs SCE) and are active to be further corroded by the acid. Because of the same corrosion behaviour as the lab weldment, preheater’s cracking in alumina factories is attributed to the combining actions of previous caustic SCC in Bayer solutions and continuous acid corrosion by pickling with the addition of RD. The following measures are effective to prevent the corrosion failure of preheater, such as postweld heat treatment at 620℃ to relax the residual weld stress, addition of CC3 and L826 as the corrosion inhibitors to improve the pickling and cleaning by the high pressure water instead of by pickling.展开更多
文摘氧化矾作为非制冷微测辐射热计的热敏材料,电阻率ρ和电阻温度系数TCR(Temperature Co-efficient of Resistance)是表征其性能的重要参数。通过对用离子束溅射得到的氧化矾薄膜在相同时间不同温度下的N2+H2退火实验,我们发现氧化矾薄膜的电阻率ρ和电阻温度系数TCR之间存在着密切的正相关关系,AES结果表明它们的变化对应着氧化矾热敏材料的O/V比例(或氧空位浓度)的变化。这三个参量随着退火温度的改变而变化,在350～500 ℃的退火温度范围内,我们发现电阻率ρ,电阻温度系数TCR以及O/V比例随着温度的变化均出现一个峰值。通过对氧化矾的电阻温度特性的分析,我们讨论了氧化矾薄膜的导电机制。我们认为,用本方法制备的氧化矾薄膜在室温下导电的载流子主要来自于相对较深能级杂质的电离。
基金Project(2013A090100013)supported by the Special Project on the Integration of Industry,Education and Research of Guangdong Province,ChinaProject(201407300993)supported by the High Technology Research and Development Program of Xinjiang Uygur Autonomous Region,China
文摘Magnetite concentrate was recovered from ferrous sulphate by co-precipitation and magnetic separation. In co-precipitation process, the effects of reaction conditions on iron recovery were studied, and the optimal reaction parameters are proposed as follows： n（CaO）/n（Fe2＋） 1.4：1, reaction temperature 80 ℃, ferrous ion concentration 0.4 mol/L, and the final mole ratio of Fe3＋ to FJ＋ in the reaction solution 1.9-2.1. In magnetic separation process, the effects of milling time and magnetic induction intensity on iron recovery were investigated. Wet milling played an important part in breaking the encapsulated magnetic phases. The results showed that the mixed product was wet-milled for 20 min before magnetic separation, the grade and recovery rate of iron in magnetite concentrate were increased from 51.41% and 84.15% to 62.05% and 85.35%, respectively.
文摘Due to the environmental policies and economic reasons,the water used in some flotation operations of complex sulfide ores is recirculated,causing the ion concentration of some species to increase over time,affecting the flotation of the minerals of interest.In this work,an experimental and thermodynamic analysis of the synthetic solutions was presented with a high content of calcium and sulfate ions.The study focused on evaluating the use of two aluminum compounds for the precipitation of Ca^(2+)and SO_(4)^(2−)in the form of ettringite.The amorphous aluminum hydroxide was found to be more efficient than the crystalline one,giving rise to 83%calcium and 91%sulfate removal.The XRD analysis of the solids showed the main reaction product of ettringite,accompanied by small amounts of calcite,due to the absorption of atmospheric carbon dioxide.The final solution after the chemical treatment showed residual calcium and sulfate concentrations below 200 mg/L.Finally,the kinetics of calcium removal appeared to correspond to a second order reaction with respect to calcium concentration,with an apparent activation energy of 53.48 kJ/mol,which may suggest that the ettringite precipitation process is governed by the chemical reaction.
文摘Stress corrosion cracking (SCC) and anticorrosion measures of TU42C weld-joint were studied by constant load experiments and pickling experiments. The results show that in 40%(mass fraction) NaOH solution at 110℃, caustic SCC occurs in TU42C weld-joints at the applied potential of-1020mV(vs SCE) for 3d while at the potential of-950mV(vs SCE) for 10d. All the cracks are intergranular. In the 10% sulfuric acid, the cracks have the most negative self-corrosion potential-432.5mV(vs SCE) and are active to be further corroded by the acid. Because of the same corrosion behaviour as the lab weldment, preheater’s cracking in alumina factories is attributed to the combining actions of previous caustic SCC in Bayer solutions and continuous acid corrosion by pickling with the addition of RD. The following measures are effective to prevent the corrosion failure of preheater, such as postweld heat treatment at 620℃ to relax the residual weld stress, addition of CC3 and L826 as the corrosion inhibitors to improve the pickling and cleaning by the high pressure water instead of by pickling.
