This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphol...This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphology,rust compositions,and corrosion kinetics of the bolt specimen were studied by visual observation,optical microscopy(OM),scanning electron microscopy(SEM),X-Ray diffractometry(XRD),micro-Raman,electron probe micro-analyser(EPMA),and potentiodynamic polarization techniques.Re-sults obtained showed a variation in corrosion kinetics,morphology,and composition of the rust layer which were driven by differential aeration and concentration effects.Due to the availability of sufficient dissolved oxygen,the oxyhydroxide compound,lepidocrocite(γ-FeOOH)was detected in the outer rust layer in the exposed region,whereas the inner rust layer was composed of magnetite(Fe_(3)O_(4)).How-ever,the oxygen-deficient contact surface revealed the presence of akaganeite(β-FeOOH)and magnetite(Fe_(3)O_(4))as dominant oxide phases.The most stable phase,goethite(α-FeOOH)was also detected in the rust formed in both regions,though in significantly low amounts.Furthermore,owing to variation in environmental conditions,the amount and density of the rust layer varied in the different regions.The estimated corrosion stability values for the different regions revealed that the corrosion products formed on the steel surfaces were non-protective,suggesting the need for specific surface treatment as a protec-tive measure.展开更多
Lutetium β-tricalcium phosphate Ca9Lu（PO4）7 was synthesized by solid-state reaction at 1200 ℃, and investigated by means of a combination of scanning electron microscopy （SEM） equipped with energy dispersive X-r...Lutetium β-tricalcium phosphate Ca9Lu（PO4）7 was synthesized by solid-state reaction at 1200 ℃, and investigated by means of a combination of scanning electron microscopy （SEM） equipped with energy dispersive X-ray spectroscopy （EDS）, X-ray diffraction （XRD）, Fourier transform infrared （FTIR） and Raman spectroscopies. SEM morphological analysis reveals the presence of sub spherical and prismatic micro crystalline aggregates, while EDS semi-quantitative analysis confirms the nominal Lu/Ca compo- sition. The unit cell and the space group were determined by X-ray powder diffraction data showing that the compound crystallizes in the rhombohedral R3c wfiitlockite-type structure, with unit cell constants a - b 1.04164（1） nm, c 3.7302（1） nm and cell volume V 3.5051（1） nm^3. The investigation was completed with the structural refinement by the Rietveld method, and discussion of the distribution of Lu within cationic sites according to the results of the Rietveld refinement. The FIIR and Raman spectra, correlated to isostructural rare earth phosphates from literature, show slight band shifts of the phosphate modes correlated to the evolving size of the rare earth elements.展开更多
基金This work was financially supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019193,KGFZD-135-19-02)the National Natural Science Foundation of China(No.51801219).Special appreciation to the CAS-TWAS Presidential Fellowship for sponsorship.
文摘This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphology,rust compositions,and corrosion kinetics of the bolt specimen were studied by visual observation,optical microscopy(OM),scanning electron microscopy(SEM),X-Ray diffractometry(XRD),micro-Raman,electron probe micro-analyser(EPMA),and potentiodynamic polarization techniques.Re-sults obtained showed a variation in corrosion kinetics,morphology,and composition of the rust layer which were driven by differential aeration and concentration effects.Due to the availability of sufficient dissolved oxygen,the oxyhydroxide compound,lepidocrocite(γ-FeOOH)was detected in the outer rust layer in the exposed region,whereas the inner rust layer was composed of magnetite(Fe_(3)O_(4)).How-ever,the oxygen-deficient contact surface revealed the presence of akaganeite(β-FeOOH)and magnetite(Fe_(3)O_(4))as dominant oxide phases.The most stable phase,goethite(α-FeOOH)was also detected in the rust formed in both regions,though in significantly low amounts.Furthermore,owing to variation in environmental conditions,the amount and density of the rust layer varied in the different regions.The estimated corrosion stability values for the different regions revealed that the corrosion products formed on the steel surfaces were non-protective,suggesting the need for specific surface treatment as a protec-tive measure.
基金Project partially supported by CNR(Italy)-CNRST(Morocco) Bilateral Project "Novel Ca_9RE(PO_4)_7 biomaterials:synthesis and multi-methodological characterization via X-ray techniques" reference CNR 1588/16
文摘Lutetium β-tricalcium phosphate Ca9Lu（PO4）7 was synthesized by solid-state reaction at 1200 ℃, and investigated by means of a combination of scanning electron microscopy （SEM） equipped with energy dispersive X-ray spectroscopy （EDS）, X-ray diffraction （XRD）, Fourier transform infrared （FTIR） and Raman spectroscopies. SEM morphological analysis reveals the presence of sub spherical and prismatic micro crystalline aggregates, while EDS semi-quantitative analysis confirms the nominal Lu/Ca compo- sition. The unit cell and the space group were determined by X-ray powder diffraction data showing that the compound crystallizes in the rhombohedral R3c wfiitlockite-type structure, with unit cell constants a - b 1.04164（1） nm, c 3.7302（1） nm and cell volume V 3.5051（1） nm^3. The investigation was completed with the structural refinement by the Rietveld method, and discussion of the distribution of Lu within cationic sites according to the results of the Rietveld refinement. The FIIR and Raman spectra, correlated to isostructural rare earth phosphates from literature, show slight band shifts of the phosphate modes correlated to the evolving size of the rare earth elements.
