To enhance the mechanical properties and corrosion resistance of magnesium alloys,high-energy shot peening(HESP)was used.According to the results,the in-situ surface nanocrystallization(ISNC)microstructure was fabrica...To enhance the mechanical properties and corrosion resistance of magnesium alloys,high-energy shot peening(HESP)was used.According to the results,the in-situ surface nanocrystallization(ISNC)microstructure was fabricated on the magnesium alloy surface,and its formation mechanism was the coordination among twins,dislocations,subgrain boundary formation and dynamic recrystallization.Under the released surface stress of sample,the residual compressive stress and microhardness rose,thus enhancing compactness of the surface passivation film Mg(OH)2.Besides,the corrosion rate dropped by 29.2% in maximum.In the polarization curve,the maximum positive shift of the corrosion potential of sample was 203 mV, and the corrosion current density decreased by 31.25% in maximum.Moreover,the compression resistance and bending resistance of the bone plate were enhanced,and the maximum improvement rates were 18.2% and 23.1%,respectively.Accordingly,HESP significantly enhanced mechanical properties and corrosion resistance of magnesium alloys.展开更多
The effects of potassium permanganate(KMnO_4)dosing position on the natural organic matter(NOM)removal as well as membrane fouling were investigated in the coagulation/ultrafiltration combined process.KMnO_4 oxidation...The effects of potassium permanganate(KMnO_4)dosing position on the natural organic matter(NOM)removal as well as membrane fouling were investigated in the coagulation/ultrafiltration combined process.KMnO_4 oxidation altered the NOM characteristics in terms of hydrophobicity and molecular weight,and destroyed humic substances originated from terraneous organisms in raw water.The optimal KMnO_4 dosage was 0.5 mg·L^(-1) in the peroxidation enhanced coagulation process with respect to the dissolved organic carbon(DOC)removal.When KMnO_4 was dosed into both upstream and downstream of coagulation,namely in the proposed twoposition dosing mode,coagulation and KMnO_4 oxidation worked individually on the apparent DOC removal.However,compared to the KMnO_4 addition prior to or after coagulation,the two-position dosing mode dramatically alleviated membrane fouling and reduced fouling irreversibility.This was attributed to the change of NOM characteristics as a result of KMnO_4 addition prior to coagulation and the presence of MnO_2 on membrane surface as a result of KMnO_4 addition prior to ultrafiltration.This work may provide useful information for the application of KMnO_4 oxidation in the coagulation/ultrafiltration combined system.展开更多
In this paper, performance of PECVD SiO 2 /Si 3 N 4 double layers electrets with different thicknesses were investigated detailedly in respect of chargeability, storage charge stability in high temperature and reliabi...In this paper, performance of PECVD SiO 2 /Si 3 N 4 double layers electrets with different thicknesses were investigated detailedly in respect of chargeability, storage charge stability in high temperature and reliability in high humidity environment. Samples with different thicknesses of Si 3 N 4 and SiO 2 were prepared on Pyrex 7740 glass substrates and characterized by isothermal and high humidity charge decay. The results of experiment approved that the PECVD SiO 2 /Si 3 N 4 double layers electrets on glass substrate has as good chargeability and charge stability in high temperature and high humidity environment as thermal oxidation or APCVD/LPCVD ones on silicon substrates. The experiment results indicated that a Si 3 N 4 layer no less than 50 nm is necessary for good charge stability in high temperature and a Si 3 N 4 layer thicker than 500 nm decreases the chargeability. Even a 2 nm Si 3 N 4 layer is enough to significantly improve the charge stability in high humidity environment. Thick SiO 2 layer can increase the surface potential of electrets under the same charging condition and its charge stability in high temperature. However, the electrets with high surface potential also exhibit poor uniformity of charge stability in high humidity environment.展开更多
基金Project(51872122) supported by the National Natural Science Foundation of ChinaProjects(2017GGX30140,2016JMRH0218) supported by the Key Research and Development Plan of Shandong Province,ChinaProject(2016-2020) supported by Taishan Scholar Engineering Special Funding of Shandong Province,China
文摘To enhance the mechanical properties and corrosion resistance of magnesium alloys,high-energy shot peening(HESP)was used.According to the results,the in-situ surface nanocrystallization(ISNC)microstructure was fabricated on the magnesium alloy surface,and its formation mechanism was the coordination among twins,dislocations,subgrain boundary formation and dynamic recrystallization.Under the released surface stress of sample,the residual compressive stress and microhardness rose,thus enhancing compactness of the surface passivation film Mg(OH)2.Besides,the corrosion rate dropped by 29.2% in maximum.In the polarization curve,the maximum positive shift of the corrosion potential of sample was 203 mV, and the corrosion current density decreased by 31.25% in maximum.Moreover,the compression resistance and bending resistance of the bone plate were enhanced,and the maximum improvement rates were 18.2% and 23.1%,respectively.Accordingly,HESP significantly enhanced mechanical properties and corrosion resistance of magnesium alloys.
基金Supported by the National Natural Science Foundation of China(51478314,51638011)the National Key Project for Research and Development Program of China(2016YFC0400503)+1 种基金the Natural Science Foundation of Tianjin(14JCQNJC09000)Science and Technology Research Projects of Colleges and Universities of Hebei Province(QN2015122)
文摘The effects of potassium permanganate(KMnO_4)dosing position on the natural organic matter(NOM)removal as well as membrane fouling were investigated in the coagulation/ultrafiltration combined process.KMnO_4 oxidation altered the NOM characteristics in terms of hydrophobicity and molecular weight,and destroyed humic substances originated from terraneous organisms in raw water.The optimal KMnO_4 dosage was 0.5 mg·L^(-1) in the peroxidation enhanced coagulation process with respect to the dissolved organic carbon(DOC)removal.When KMnO_4 was dosed into both upstream and downstream of coagulation,namely in the proposed twoposition dosing mode,coagulation and KMnO_4 oxidation worked individually on the apparent DOC removal.However,compared to the KMnO_4 addition prior to or after coagulation,the two-position dosing mode dramatically alleviated membrane fouling and reduced fouling irreversibility.This was attributed to the change of NOM characteristics as a result of KMnO_4 addition prior to coagulation and the presence of MnO_2 on membrane surface as a result of KMnO_4 addition prior to ultrafiltration.This work may provide useful information for the application of KMnO_4 oxidation in the coagulation/ultrafiltration combined system.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2009CB320300)
文摘In this paper, performance of PECVD SiO 2 /Si 3 N 4 double layers electrets with different thicknesses were investigated detailedly in respect of chargeability, storage charge stability in high temperature and reliability in high humidity environment. Samples with different thicknesses of Si 3 N 4 and SiO 2 were prepared on Pyrex 7740 glass substrates and characterized by isothermal and high humidity charge decay. The results of experiment approved that the PECVD SiO 2 /Si 3 N 4 double layers electrets on glass substrate has as good chargeability and charge stability in high temperature and high humidity environment as thermal oxidation or APCVD/LPCVD ones on silicon substrates. The experiment results indicated that a Si 3 N 4 layer no less than 50 nm is necessary for good charge stability in high temperature and a Si 3 N 4 layer thicker than 500 nm decreases the chargeability. Even a 2 nm Si 3 N 4 layer is enough to significantly improve the charge stability in high humidity environment. Thick SiO 2 layer can increase the surface potential of electrets under the same charging condition and its charge stability in high temperature. However, the electrets with high surface potential also exhibit poor uniformity of charge stability in high humidity environment.
