MnS and MnO inclusions with a small amount of chromium were obtained by heat-treatments of Type 304 stainless steel at 1353, 1573, and 1673 K, and the anodic dissolution behavior of the inclusions was investigated using a microelectrochemical technique. In the case of the sulfide inclusions, those with a high dissolution potential were found to provide high pitting potentials in the macroscopic measurements in 0.1 M NaCl. The initiation sites of metastable and stable pits were at the boundaries of the inclusions and the matrix in 3 M NaCl, 3 M MgCl 2 , and 8 M LiCl. The dissolution current densities on the inclusion surface at the moment of the initiation of a stable pit decreased with increasing chloride-ion concentration. The synergistic effect of chloride ions and sulfur-containing species released from the inclusions was thought to play an important role in the pit-initiation process. The oxide inclusions did not dissolve in the passive region of Type 304 stainless steel. In the solutions with chloride-ion concentrations of up to 6 M, pitting did not occur at the oxide inclusions in microscopic polarization measurements. The oxide inclusions exhibited a comparatively inert characteristic as pit-initiation sites.Sulfide inclusions in stainless steels, particularly manganese sulfide, are well known to act as initiation sites for pitting in chloride environments. 1 It is generally agreed that the most significant phenomenon which precedes pitting at the inclusions is sulfide dissolution, and also that the complete dissolution of the inclusions is not required for pit-initiation sites to be produced. 2,3 Sulfur-containing species are released during MnS dissolution, and various aggressive compounds, such as SO 4 2− , HSO 3 − , S 2 O 3 2− , S, and H 2 S, have been proposed as the reaction products. 2-9 Park et al., Paik et al., and Webb et al. demonstrated that the thiosulfate ions released from sulfide inclusions accelerated the dissolution of the inclusions and resulted in stable pitting when their concentration exceeded a critical value. 7-9 Krawiec et al. and Vignal et al. experimentally revealed that the sulfur species produced during MnS dissolution reacted with the passive film on a metal matrix to increase pitting susceptibility and to enhance cathodic reaction kinetics. 10-12 Park and Böhni detected the local acidification on MnS inclusions during the dissolution and pointed out its relationship to pitting at the inclusions. 13 Many researchers have revealed that the MnS/matrix boundaries mainly dissolved, and metastable pits were generated at the boundaries. 3,14-22 In our previous study, the synergistic effect of sulfur-containing species and chloride ions on pit initiation was suggested from the morphological observation of metastable and stable pits in chloride and chloride-free environments. 21 Suter and Böhni examined the anodic polarization behavior of different zones of a single MnS inclusion and revealed that the dissolution potential of the inclusion/matrix boundary was lower than that of the ...
A fast time response, wide dynamic range neutron flux monitor has been developed toward the LHD deuterium operation by using leading-edge signal processing technologies providing maximum counting rate up to ∼5 × 109 counts/s. Because a maximum total neutron emission rate over 1 × 1016 n/s is predicted in neutral beam-heated LHD plasmas, fast response and wide dynamic range capabilities of the system are essential. Preliminary tests have demonstrated successful performance as a wide dynamic range monitor along the design.
A new thermally expandable microcapsule was developed for use with foaming polypropylene (PP) by injection molding and extrusion processes at operating temperatures above 2008C. The microcapsule consists of a blowing agent as the core and a shell polymer. The rheological properties of the shell polymer were controlled by a crosslinking agent to design the expandability and shrinkage. The effects of rheological properties on the expandability and the surface appearance of foam products were thoroughly investigated. It was found that storage modulus G 0 and tan d significantly affected the expandability and shrinkage and were controllable through crosslinking polymerization. Visual observation of batch foaming, rheological measurement, and experiments of foam injection molding and extrusion elucidated the existence of the optimal degree of crosslinking that could realize more than 30% density reduction while maintaining a smooth surface at PP foam injection molding and extrusion. POLYM. ENG. SCI., 50:835-842,
A wide-range neutron flux measurement instrument is developed herein for monitoring the total neutron emission rate and yield of the Large Helical Device (LHD) during deuterium experiments implemented from March 2017 in the National Institute for Fusion Science (NIFS), Japan. The instrument is designed for and installed on the Neutron Flux Monitoring (NFM) system, which measures the counting rate using a 235 U Fission Chamber. By combining the pulse counting and Campbell methods, the Digital Signal Processing Unit (DSPU) realized a wide dynamic range of over six orders of magnitude from 1 × 10 3 counts/s (cps) to 5 × 10 9 cps. This study explains and discusses how the instrument is developed, including topics from the predevelopment activities to the verification test at the Kyoto University Critical Assembly (KUCA). Experimental results in the LHD using the finished products suggest that the NFM system works well during deuterium experiments.
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