The presence of salt has a profound effect on the size,shape and structure of sodium dodecyl sulfate(SDS)micelles.There have been a great number of experiments on SDS micelles in the presence and absence of salt to st...The presence of salt has a profound effect on the size,shape and structure of sodium dodecyl sulfate(SDS)micelles.There have been a great number of experiments on SDS micelles in the presence and absence of salt to study this complex problem.Unfortunately,it is not clear yet how electrolyte ions influence the structure of micelles.By describing the compromise between dominant mechanisms,a simplified atomic model of SDS in presence of salt has been developed and the molecular dynamics(MD)simulations of two series of systems with different concentrations of salt and charges of ion have been performed.Polydispersity of micelle size is founded at relatively high concentration of SDS and low charge of cation.Although the counter-ion pairs with head groups are formed,the transition of micelle shape is not observed because the charge of cation is not enough to neutralize the polar of micelle surface.展开更多
Cyclic metallurgical process for separation and recovery of Cr from vanadium precipitated solution by precipitation with PbCO_(3)and leaching with Na_(2)CO_(3)was investigated.The concentration of Cr residue in the so...Cyclic metallurgical process for separation and recovery of Cr from vanadium precipitated solution by precipitation with PbCO_(3)and leaching with Na_(2)CO_(3)was investigated.The concentration of Cr residue in the solution decreases from 2.360 to 0.001 g/L by adding PbCO_(3)into vanadium precipitated solution according to Pb/Cr molar ratio of 2.5,adjusting the pH to 3.0 and stirring for 180 min at 30℃.Then,the precipitates were leached with hot Na_(2)CO_(3)solution to obtain leaching solution containing Na_(2)CrO_(4)and leaching residue containing PbCO_(3).The leaching efficiency of Cr reaches 96.43%by adding the precipitates into 0.5 mol/L Na_(2)CO_(3)solution with the mass ratio of liquid to solid(L/S)of 10:1 mL/g and stirring for 60 min under pH 9.5 at 70℃.After filtration,leaching residue is reused in Cr precipitation and leaching solution is used to circularly leach the Cr precipitates until Na_(2)CrO_(4)approaches the saturation.Finally,the product of Na_(2)CrO_(4)·4H_(2)O is obtained by evaporation and crystallization of leaching solution.展开更多
The separation and recovery of V from chromium-containing vanadate solution were investigated by a cyclic metallurgical process including selective precipitation of vanadium,vanadium leaching and preparation of vanadi...The separation and recovery of V from chromium-containing vanadate solution were investigated by a cyclic metallurgical process including selective precipitation of vanadium,vanadium leaching and preparation of vanadium pentoxide.By adding Ca(OH)_(2) and ball milling,not only the V in the solution can be selectively precipitated,but also the leaching kinetics of the precipitate is significantly improved.The precipitation efficiency of V is 99.59%by adding Ca(OH)_(2) according to Ca/V molar ratio of 1.75:1 into chromium-containing vanadate solution and ball milling for 60 min at room temperature,while the content of Cr in the precipitate is 0.04%.The leaching rate of V reaches 99.35%by adding NaHCO_(3) into water according to NaHCO_(3)/V molar ratio of 2.74:1 to leach V from the precipitate with L/S ratio of 4:1 mL/g and stirring for 60 min at room temperature.The crystals of NH_(4)VO_(3) are obtained by adjusting the leaching solution pH to be 8.0 with CO2 and then adding NH_(4)HCO_(3) according to NH_(4)HCO_(3)/NaVO_(3) molar ratio of 1:1 and stirring for 8 h at room temperature.After filtration,the crystallized solution containing ammonia is reused to leach the precipitate of calcium vanadates,and the leaching efficiency of V is>99%after stirring for 1 h at room temperature.Finally,the product of V_(2)O_(5) with purity of 99.6%is obtained by calcining the crystals at 560℃ for 2 h.展开更多
特殊螺纹接头是高温高压井油套管柱连接的重要部件,管内流体压力、流速的变化诱发管柱振动,引起特殊螺纹接头密封面发生微滑,表现为力与位移的刚度软化与滞回等非线性特征,进而导致接头密封性能下降。为查明密封面的微滑机制,基于离散I...特殊螺纹接头是高温高压井油套管柱连接的重要部件,管内流体压力、流速的变化诱发管柱振动,引起特殊螺纹接头密封面发生微滑,表现为力与位移的刚度软化与滞回等非线性特征,进而导致接头密封性能下降。为查明密封面的微滑机制,基于离散Iwan模型本构关系,建立某锥面-锥面Φ88.9 mm×6.45 mm P110特殊螺纹接头有限元分析模型,得到不同循环位移载荷下密封面处的力-位移滞回曲线,通过滞回曲线离散化分析,识别出离散Iwan模型的4组参数;构建该特殊螺纹接头等效Iwan模型,分析密封面间的微滑状态;对比分析两种模型滞回曲线的相似度,验证等效Iwan模型的准确性。结果表明:构建的特殊螺纹接头等效Iwan模型与有限元分析模型的综合相似度较高,滞回曲线面积重合度大于92%,位置误差小于2%;利用特殊螺纹接头等效Iwan模型得到的滞回曲线,能够准确描述密封面间黏着、滑移、宏观滑移之间的转化过程,从而为特殊螺纹接头滞回曲线分析提供一种新方法。展开更多
基金Supported by the Outstanding Overseas Research Team Project of the Chinese Academy of Sciences, the National Natural Science Foundation of China （20221603）, and the Research Fund of Key Lab for Nanomaterials, Ministry of Education, China （2006-1）.
文摘The presence of salt has a profound effect on the size,shape and structure of sodium dodecyl sulfate(SDS)micelles.There have been a great number of experiments on SDS micelles in the presence and absence of salt to study this complex problem.Unfortunately,it is not clear yet how electrolyte ions influence the structure of micelles.By describing the compromise between dominant mechanisms,a simplified atomic model of SDS in presence of salt has been developed and the molecular dynamics(MD)simulations of two series of systems with different concentrations of salt and charges of ion have been performed.Polydispersity of micelle size is founded at relatively high concentration of SDS and low charge of cation.Although the counter-ion pairs with head groups are formed,the transition of micelle shape is not observed because the charge of cation is not enough to neutralize the polar of micelle surface.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(No.51974369)NSFC-STINT(No.52111530192)+1 种基金Postgraduate Research Innovation Project of Central South University,China(No.2019zzts244)the Open Sharing Fund for the Large-scale Instruments and Equipments of Central South University,China(No.CSUZC202029).
文摘Cyclic metallurgical process for separation and recovery of Cr from vanadium precipitated solution by precipitation with PbCO_(3)and leaching with Na_(2)CO_(3)was investigated.The concentration of Cr residue in the solution decreases from 2.360 to 0.001 g/L by adding PbCO_(3)into vanadium precipitated solution according to Pb/Cr molar ratio of 2.5,adjusting the pH to 3.0 and stirring for 180 min at 30℃.Then,the precipitates were leached with hot Na_(2)CO_(3)solution to obtain leaching solution containing Na_(2)CrO_(4)and leaching residue containing PbCO_(3).The leaching efficiency of Cr reaches 96.43%by adding the precipitates into 0.5 mol/L Na_(2)CO_(3)solution with the mass ratio of liquid to solid(L/S)of 10:1 mL/g and stirring for 60 min under pH 9.5 at 70℃.After filtration,leaching residue is reused in Cr precipitation and leaching solution is used to circularly leach the Cr precipitates until Na_(2)CrO_(4)approaches the saturation.Finally,the product of Na_(2)CrO_(4)·4H_(2)O is obtained by evaporation and crystallization of leaching solution.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(51974369)the Postgraduate Research Innovation Project of Central South University,China(2019zzts244).
文摘The separation and recovery of V from chromium-containing vanadate solution were investigated by a cyclic metallurgical process including selective precipitation of vanadium,vanadium leaching and preparation of vanadium pentoxide.By adding Ca(OH)_(2) and ball milling,not only the V in the solution can be selectively precipitated,but also the leaching kinetics of the precipitate is significantly improved.The precipitation efficiency of V is 99.59%by adding Ca(OH)_(2) according to Ca/V molar ratio of 1.75:1 into chromium-containing vanadate solution and ball milling for 60 min at room temperature,while the content of Cr in the precipitate is 0.04%.The leaching rate of V reaches 99.35%by adding NaHCO_(3) into water according to NaHCO_(3)/V molar ratio of 2.74:1 to leach V from the precipitate with L/S ratio of 4:1 mL/g and stirring for 60 min at room temperature.The crystals of NH_(4)VO_(3) are obtained by adjusting the leaching solution pH to be 8.0 with CO2 and then adding NH_(4)HCO_(3) according to NH_(4)HCO_(3)/NaVO_(3) molar ratio of 1:1 and stirring for 8 h at room temperature.After filtration,the crystallized solution containing ammonia is reused to leach the precipitate of calcium vanadates,and the leaching efficiency of V is>99%after stirring for 1 h at room temperature.Finally,the product of V_(2)O_(5) with purity of 99.6%is obtained by calcining the crystals at 560℃ for 2 h.
文摘特殊螺纹接头是高温高压井油套管柱连接的重要部件,管内流体压力、流速的变化诱发管柱振动,引起特殊螺纹接头密封面发生微滑,表现为力与位移的刚度软化与滞回等非线性特征,进而导致接头密封性能下降。为查明密封面的微滑机制,基于离散Iwan模型本构关系,建立某锥面-锥面Φ88.9 mm×6.45 mm P110特殊螺纹接头有限元分析模型,得到不同循环位移载荷下密封面处的力-位移滞回曲线,通过滞回曲线离散化分析,识别出离散Iwan模型的4组参数;构建该特殊螺纹接头等效Iwan模型,分析密封面间的微滑状态;对比分析两种模型滞回曲线的相似度,验证等效Iwan模型的准确性。结果表明:构建的特殊螺纹接头等效Iwan模型与有限元分析模型的综合相似度较高,滞回曲线面积重合度大于92%,位置误差小于2%;利用特殊螺纹接头等效Iwan模型得到的滞回曲线,能够准确描述密封面间黏着、滑移、宏观滑移之间的转化过程,从而为特殊螺纹接头滞回曲线分析提供一种新方法。
