Effect of microstructure and passive film on corrosion resistance of 2507 super duplex stainless steel prepared by different cooling methods in simulated marine environment

The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel(SDSS)in simulated marine environment was investigated by electrochemical measurements,periodic wet–dry cyclic corrosion test,scanning Kelvin probe force microscopy,atomic force microscopy,and X-ray photoelectron spectrometry.The results show that the occupation ratio ofγphase increases with the decrease in cooling rate,whereas the content ofαphase reduces gradually.In addition,theσprecipitated phase only emerges in the annealed steel.The pitting sensitivity and corrosion rate of 2507 SDSS reduce first and then increase as the cooling rate decreases.Theσprecipitated phase drastically reduces the protective ability of the passive film and facilitates micro-galvanic corrosion of the annealed steel.For various microstructures,the pits are preferentially distributed within theσandγphases.The corrosion resistance of 2507 SDSS prepared by different cooling methods is closely related to the microstructure and structure(stability and homogeneity)of the passive film.Normalized steel shows an optimal corrosion resistance,followed by the quenched and annealed steels.

Comparison of the performance of MS enteroscope series and Japanese double-and single-balloon enteroscopes

BACKGROUND Small intestine disease endangers human health and is not easy to locate and diagnose.AIM To observe the effect of the MS series of small intestine endoscopes on the gastrointestinal tract,the changes in serum gastrin levels and intestinal tissue,and the time required for the examination.METHODS In vivo experiments in 20 Living pigs were conducted,Bowel preparation was routinely performed,Intravenous anesthesia with propofol and ketamine was applied,the condition of the small intestine was observed and the detection time of the MS series of small intestine endoscopes were recorded,The changes in intestinal tissue using the MS series of small intestine endoscopes observed and compared before and after the examination,Venous blood(3-5 mL)from pigs was collected before and after the experiment;changes in intestinal tissue after use of the MS series of small intestine endoscopes observed after examination.After completion of each type of small intestine endoscope experiment,the pigs were allowed to rest and the next type of small intestine endoscope experiment was performed after 15 days of normal feeding.The detection time data of the single-balloon small intestine endoscope and doubleballoon small intestine endoscope were collected from four hospitals.RESULTS One case of Ascarislumbricoides,one of suspected Crohn’s disease,one small intestinal diverticulum and one anesthesia accident were observed in pigs.The small intestine showed no differences in the MS series of small intestine endoscopes and there were no differences in serum gastrin between the groups(P>0.05).The time required for inspection was recorded,and the overall detection time for the Japanese small intestine endoscopes was approximately 1.68±0.16 h.CONCLUSION Intestinal ascariasis is a common disease in pigs.Some pigs have abnormal intestinal variation.After continuous upgrade and improvement,the MS-3 and MS-4 small intestine endoscope appear superior in terms of detection time.

CO Catalytic Oxidation of Pt-Loaded Perovskite BaTiO_3 Near Ferroelectric-Phase Transition Temperature

Perovskite BaTiO3 （BTO） nanocrystals with a size of 150-200 nm have successfully been synthesized via a facile hydrothermal method by employing titanate nanowires as synthetic precursor. Tetragonality and spontaneous ferroelectric polarization of BTO nanocrystals have been determined by X-ray diffraction and transmission electron microscopy investigations. BTO nanocrystals loaded with Pt nanoparticles in a size of 2-5 nm have been explored as a catalyst towards CO oxidation to CO2. It is interesting to find that CO catalytic conversion rate over Pt-BTO nanocrystals gradually decreased and further increased near 100 ℃ when the catalytic temperature keeps increasing, whereas the conversion behavior in oxides is expected to be enhanced upon the catalytic temperature grows. Using differential scanning calorimetry and first-principle calculations, the observed catalytic behavior has been discussed on the basis of the ferroelectric polarization effect and the ferroelectric-paraelectric transition of BTO nanocrystals with a Curie temperature of 110 ℃. Below Curie temperature, CO catalytic oxidation could be significantly tailored by ferroelectric polarization of BTO nanocrystals via a promoted dissociation of O2 molecules. The findings suggest that a ferroelectric polarization in perovskite oxides could be an alternative way to modify the CO catalytic oxidation.