The corrosion mechanism of AZ31 magnesium alloy used as automobile components and the influence of the concentration of Cl- ion in simulated acid rain(SAR)were studied by electrochemical tests and SEM.The results show...The corrosion mechanism of AZ31 magnesium alloy used as automobile components and the influence of the concentration of Cl- ion in simulated acid rain(SAR)were studied by electrochemical tests and SEM.The results show that pitting corrosion happens around the AlMn phases locating at the grain boundary.The corrosion of AZ31 magnesium alloy in SAR is controlled by the rate of anodic dissolution and hydrogen evolution,and the corrosion rate of AZ31 increases with increasing concentration of Cl- ion.However,the Cl- ion in SAR is not the main influencing factor inducing the pitting corrosion.展开更多
Low molecule weight carboxylic acids are ubiquitous and important chemical constituents in the troposphere.Seven carboxylic acids in the rainwater of Guiyang and Shangzhong were simultaneously determined by ion chroma...Low molecule weight carboxylic acids are ubiquitous and important chemical constituents in the troposphere.Seven carboxylic acids in the rainwater of Guiyang and Shangzhong were simultaneously determined by ion chromatography from April 2006 to April 2007.Formic, acetic and oxalic acids were found to be the predominant carboxylic acids.Their volume weighted average concentration (VWA) in the rainwater of Guiyang were 14.24 μmol/L, 9.35 μmol/L and 2.79 μmol/L, respectively;as compared to 4.95 μmol/L, 1.35 μmol/L and 2.31 μmol/L in the rainwater of Shangzhong.In Shangzhong it is witnessed that the concentra-tions of these acids were higher in the summer than in the winter and direct emissions from vegetations or soils may account for the main provenance of the acids.This is, however, not the case in Guiyang, where the concentrations of the carboxylic acids were higher during the non-growing season than during the growing season.The relatively weak scavenging affected by scarce and little rainwater as well as the particles accompanied with the rainfall may have some effect on the carboxylic acids during the wintertime in Guiyang.Carboxylic acids in the rainwater of Guiyang were estimated to account for 18.7% to the free acidity, where formic, acetic and oxalic acids accounted for 7.9%, 4.7%, 6.1%, respectively.In Shangzhong, the 3 primary carboxylic acids represented 58.1% to the free acidity where formic, acetic and oxalic acids represented 25.1%, 7.5%, 25.5%, respectively.Carboxylic anions accounted for 6.6% (1.7%–19.2%) to the total anions in the rainwater of Guiyang.Carboxylic anions repre-sented 13.2% (0.5%–92.2%) to the total anions in the rainwater of Shangzhong.These results indicated that carboxylic acids were the important contributors to the rainwater acidity, especially in remote regions.展开更多
The problems of traditional concrete such as brittleness,poor toughness and short service life of concrete engineering under acid rain or marine environment need to be solved urgently.Hydrated calcium silicate(C-S-H)i...The problems of traditional concrete such as brittleness,poor toughness and short service life of concrete engineering under acid rain or marine environment need to be solved urgently.Hydrated calcium silicate(C-S-H)is a key component to improve the mechanical properties and durability of concrete.However,the traditional method of concrete material design based on empirical models or comparative tests has become a bottleneck restricting the sustainable development of concrete.The synthesis method,molecular structure and properties of C-S-H were systematically described in this paper;The interface structure and interaction of graphene oxide/calcium silicate hydrate(C-S-H/GO)were discussed.On this basis,the saturated and unsaturated transport characteristics of ions and water molecules in C-S-H/GO nanochannels under the environment of ocean and acid rain were introduced.The contents of this review provide the basis for improving the multi-scale transmission theory and microstructure design of concrete.It has important guiding significance for analyzing and improving the service life of concrete in complex environment.展开更多
基金Project(50901082)supported by the National Natural Science Foundation of ChinaProject(2007CB613705)supported by the National Basic Research Program of China
文摘The corrosion mechanism of AZ31 magnesium alloy used as automobile components and the influence of the concentration of Cl- ion in simulated acid rain(SAR)were studied by electrochemical tests and SEM.The results show that pitting corrosion happens around the AlMn phases locating at the grain boundary.The corrosion of AZ31 magnesium alloy in SAR is controlled by the rate of anodic dissolution and hydrogen evolution,and the corrosion rate of AZ31 increases with increasing concentration of Cl- ion.However,the Cl- ion in SAR is not the main influencing factor inducing the pitting corrosion.
基金supported by the National Basic Re-search Program of China (2006CB43205)the National Natural Science Foundation of China (4053048)
文摘Low molecule weight carboxylic acids are ubiquitous and important chemical constituents in the troposphere.Seven carboxylic acids in the rainwater of Guiyang and Shangzhong were simultaneously determined by ion chromatography from April 2006 to April 2007.Formic, acetic and oxalic acids were found to be the predominant carboxylic acids.Their volume weighted average concentration (VWA) in the rainwater of Guiyang were 14.24 μmol/L, 9.35 μmol/L and 2.79 μmol/L, respectively;as compared to 4.95 μmol/L, 1.35 μmol/L and 2.31 μmol/L in the rainwater of Shangzhong.In Shangzhong it is witnessed that the concentra-tions of these acids were higher in the summer than in the winter and direct emissions from vegetations or soils may account for the main provenance of the acids.This is, however, not the case in Guiyang, where the concentrations of the carboxylic acids were higher during the non-growing season than during the growing season.The relatively weak scavenging affected by scarce and little rainwater as well as the particles accompanied with the rainfall may have some effect on the carboxylic acids during the wintertime in Guiyang.Carboxylic acids in the rainwater of Guiyang were estimated to account for 18.7% to the free acidity, where formic, acetic and oxalic acids accounted for 7.9%, 4.7%, 6.1%, respectively.In Shangzhong, the 3 primary carboxylic acids represented 58.1% to the free acidity where formic, acetic and oxalic acids represented 25.1%, 7.5%, 25.5%, respectively.Carboxylic anions accounted for 6.6% (1.7%–19.2%) to the total anions in the rainwater of Guiyang.Carboxylic anions repre-sented 13.2% (0.5%–92.2%) to the total anions in the rainwater of Shangzhong.These results indicated that carboxylic acids were the important contributors to the rainwater acidity, especially in remote regions.
基金This work was supported by a Doctoral program of Zhejiang University of science and technology(F701104L08)。
文摘The problems of traditional concrete such as brittleness,poor toughness and short service life of concrete engineering under acid rain or marine environment need to be solved urgently.Hydrated calcium silicate(C-S-H)is a key component to improve the mechanical properties and durability of concrete.However,the traditional method of concrete material design based on empirical models or comparative tests has become a bottleneck restricting the sustainable development of concrete.The synthesis method,molecular structure and properties of C-S-H were systematically described in this paper;The interface structure and interaction of graphene oxide/calcium silicate hydrate(C-S-H/GO)were discussed.On this basis,the saturated and unsaturated transport characteristics of ions and water molecules in C-S-H/GO nanochannels under the environment of ocean and acid rain were introduced.The contents of this review provide the basis for improving the multi-scale transmission theory and microstructure design of concrete.It has important guiding significance for analyzing and improving the service life of concrete in complex environment.
