Utilizing Si, Fe and Mn concentrations within the end-member PACMANUS hydrothermal fluid, Si-Fe-Mn-H2O Pourbaix diagrams were constructed at 300℃and 25℃. ThePourbaix diagrams show that the main Si, Fe and Mn oxides ...Utilizing Si, Fe and Mn concentrations within the end-member PACMANUS hydrothermal fluid, Si-Fe-Mn-H2O Pourbaix diagrams were constructed at 300℃and 25℃. ThePourbaix diagrams show that the main Si, Fe and Mn oxides species precipitating from the hydrothermal fluid were SiO2, Fe（OH）3, Fe3（OH）8, Mn3O4, and Mn2O3at 25℃. During mixing of hydrothermal fluid with seawater, SiO2 precipitated earlier than Fe-Mn-oxyhydroxides because of the lower stability boundary. Then Fe（OH）2 precipitated first, followed by Fe3（OH）8 and Fe（OH）3, and last, small amounts of Mn3O4 and Mn2O3 precipitated. Fe（OH）3was readily de-posited in alkaline solution with little influence by Eh. There were many Si-Fe-Mn-concentric particles in the polished sections of the massive precipitates collected from PACMANUS. In the concentric nucleus and ellipsoid, Si oxides precipitated first before the hydrothermal fluid had mixed with seawater. In the concen-tric nucleus, after the precipitation of Si oxides, the increase of pH and Eh promoted the precipitation of Mn oxides around the Si oxides. In the large ellipsoid, the precipitation of Fe was divided into two periods. In the early period, increase of pH value of hydrothermal fluid produced by low-temperature convection and an input of a small volume of seawater promoted a small amount of Fe（OH）3 to precipitate in the Si-rich core. In the late period, after complete mixing with seawater and the resultant fluid was close to neutral or slightly alkaline in pH, Fe（OH）3was easily precipitated from the solution and distributed around the Si-rich core.展开更多
A new viewpoint of computer program poubaix diagram was proposed on traditional φ pH diagrams. All equilibrium principle and activity term method were used to plot φ pH diagrams for M H 2O systems based on the therm...A new viewpoint of computer program poubaix diagram was proposed on traditional φ pH diagrams. All equilibrium principle and activity term method were used to plot φ pH diagrams for M H 2O systems based on the thermochemical database developed. And a new method——arithmetic geometric method is used to solve nonlinear equations group. The calculation procedure is proved to be efficient and convergent. The method seldom depends on artificial intervention and can extend to multi component all equilibrium φ pH diagrams such as M ligand H 2O system. [展开更多
This work investigated the chemical and electrochemical mechanisms of localised corrosion triggered by CaS·xMgO·y Al_(2)O_(3)·TiN complex inclusions in high strength low alloy steel(HSLAS)under a simula...This work investigated the chemical and electrochemical mechanisms of localised corrosion triggered by CaS·xMgO·y Al_(2)O_(3)·TiN complex inclusions in high strength low alloy steel(HSLAS)under a simulated marine environment.Special focus was given to the role of the TiN portion of the inclusion on the initiation and growth of the corrosion pits.The thermodynamic process of pitting initiation was investigated by Gibbs free energy,Pourbaix diagram and first principle calculation.Localised corrosion is mainly induced by inclusions and triggered by dissolution of adjacent distorted matrix.Chemical dissolution of CaS portion in CaS·xMgO·y Al_(2)O_(3)·TiN complex inclusion creates an acidic aggressive environment that accelerates the further dissolution of inclusion and matrix.Galvanic coupling effect between TiN inclusion and matrix is directly verified.TiN covered with a TiOfilm acts as the cathodic phase in galvanic corrosion,although it has a lower Volta potential than the matrix.This is an unusual correlation with the scanning Kelvin probe force microscopy result,which has been explained for this special system.展开更多
基金The National Key Basic Research Program of China under contract Nos 2013CB429700the National Special Fund for the 12th Five Year Plan of COMRA under contract Nos DY125-12-R-02 and DY125-12-R-05+3 种基金the National Natural Science Foundation of China under contract Nos 41325021,40830849,40976027 and 41476044the Shandong Province Natural Science Foundation of China for Distinguished Young Scholars under contract Nos JQ200913the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA11030302the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘Utilizing Si, Fe and Mn concentrations within the end-member PACMANUS hydrothermal fluid, Si-Fe-Mn-H2O Pourbaix diagrams were constructed at 300℃and 25℃. ThePourbaix diagrams show that the main Si, Fe and Mn oxides species precipitating from the hydrothermal fluid were SiO2, Fe（OH）3, Fe3（OH）8, Mn3O4, and Mn2O3at 25℃. During mixing of hydrothermal fluid with seawater, SiO2 precipitated earlier than Fe-Mn-oxyhydroxides because of the lower stability boundary. Then Fe（OH）2 precipitated first, followed by Fe3（OH）8 and Fe（OH）3, and last, small amounts of Mn3O4 and Mn2O3 precipitated. Fe（OH）3was readily de-posited in alkaline solution with little influence by Eh. There were many Si-Fe-Mn-concentric particles in the polished sections of the massive precipitates collected from PACMANUS. In the concentric nucleus and ellipsoid, Si oxides precipitated first before the hydrothermal fluid had mixed with seawater. In the concen-tric nucleus, after the precipitation of Si oxides, the increase of pH and Eh promoted the precipitation of Mn oxides around the Si oxides. In the large ellipsoid, the precipitation of Fe was divided into two periods. In the early period, increase of pH value of hydrothermal fluid produced by low-temperature convection and an input of a small volume of seawater promoted a small amount of Fe（OH）3 to precipitate in the Si-rich core. In the late period, after complete mixing with seawater and the resultant fluid was close to neutral or slightly alkaline in pH, Fe（OH）3was easily precipitated from the solution and distributed around the Si-rich core.
文摘A new viewpoint of computer program poubaix diagram was proposed on traditional φ pH diagrams. All equilibrium principle and activity term method were used to plot φ pH diagrams for M H 2O systems based on the thermochemical database developed. And a new method——arithmetic geometric method is used to solve nonlinear equations group. The calculation procedure is proved to be efficient and convergent. The method seldom depends on artificial intervention and can extend to multi component all equilibrium φ pH diagrams such as M ligand H 2O system. [
基金the National Natural Science Foundation of China(Nos.51871024,51822401 and 52104319)the National Science and Technology Resources Investigation Program of China(No.2019FY101400)。
文摘This work investigated the chemical and electrochemical mechanisms of localised corrosion triggered by CaS·xMgO·y Al_(2)O_(3)·TiN complex inclusions in high strength low alloy steel(HSLAS)under a simulated marine environment.Special focus was given to the role of the TiN portion of the inclusion on the initiation and growth of the corrosion pits.The thermodynamic process of pitting initiation was investigated by Gibbs free energy,Pourbaix diagram and first principle calculation.Localised corrosion is mainly induced by inclusions and triggered by dissolution of adjacent distorted matrix.Chemical dissolution of CaS portion in CaS·xMgO·y Al_(2)O_(3)·TiN complex inclusion creates an acidic aggressive environment that accelerates the further dissolution of inclusion and matrix.Galvanic coupling effect between TiN inclusion and matrix is directly verified.TiN covered with a TiOfilm acts as the cathodic phase in galvanic corrosion,although it has a lower Volta potential than the matrix.This is an unusual correlation with the scanning Kelvin probe force microscopy result,which has been explained for this special system.
