Ultra-Pure Ferritic Stainless Steels-Grade,Refining Operation,and Application

The grades of ultra-pure ferritic stainless steels, especially the grades used in automobile exhaust system, were reviewed. The dependence of properties on alloying elements, the refining facilities, and the mechanism of the reactions in steel melts were described in detail. Vacuum, strong stirring, and powder injection proved to be effective technologies in the melting of ultra-pure ferritic stainless steels. The application of the ferritic grades was also briefly introduced.

Influence of Al_2O_3/CeZrAl composition on the catalytic behavior of Pd/Rh catalyst

Al2O3 and Ce-Zr mixed oxides are important components of the automobile three-way catalyst.Various contents modifying A12O3(GAL) was physically introduced into Ce-Zr-Al mixed oxides(CZA) to form series of GAL/CZA composition.The Pd/Rh catalyst samples were prepared by different GAL/CZA support loading Pd/Rh,then aged at 950 oC for 6 h.The catalytic behavior of different Pd/Rh catalyst samples was studied.Surface area,oxygen storage capacity(OSC) and H2 adsorption capacity(TPR) of fresh and aged samples were...

Modified Natural Zeolites as Catalysts for Catalytic Reduction of NO with COmMain Components of Exhaust Gases

The study of oxidized-reduced properties of modified natural zeolites from deposits of Georgia--clinoptilolite and mordenite in reaction of reduction NO with H2, NH3, CH4 and especially CO was carried out for the purpose to obtain effective catalyst for afterburning of toxic components of automobile exhaust. The activity of zeolites essentially depends on nature of cation and temperature of reaction and slightly depends on structure of zeolite and ratio of reactants. The introduction of copper and iron ions in preliminary decationated clinoptilolite and mordenite causes growth of conversion degree of nitrogen and carbon monoxides almost on a degree, especially in low temperature interval. The reaction between NO and CO molecules proceeds in coordinative sphere of TM cations through formation ofnitrosyl and carbonyl complexes.

Effective removal of automobile exhausts over flower-like Ce_(1-x)Cu_xO_2 nanocatalysts exposed active {100} plane

This work elucidates the synthesis and characterization of copper ions incorporated ceria(Ce1-xCuxO2)nanocatalysts with 3 D flower-like and nanocrystalline morphology for the purification of automobile exhausts. XRD and Raman results confirm the presence of copper ions in ceria. The 3 D flower-like and nanocrystalline morphology exhibited by these catalysts were seen by FESEM images. HRTEM and SAED results confirm that(100) plane is dominantly presented in 3 D flower-like Ce1-xCuxO2catalysts when compared to nanocrystalline morphology. The textural properties of synthesized catalysts was done with the help of N2 sorption study, which confirms that flower-like Ce1-xCuxO2catalysts show high surface area and pore volume. The existence of Ce3+, Ce4+, Cu+and Cu2+ions in the catalyst were examined by XPS and DR UV-Vis techniques. Oxygen storage capacity(OSC) of the catalysts was studied by H2-TPR analysis. These characterization results elucidate the presence of dominant active sites(Ce3+, Ce4+, Cu+and Cu2+) and {100} plane in the flower-like morphology compared to nanocrystalline. The catalytic activity of synthesized Ce1-xCuxO2catalysts was tested for removal of CO, HCxand NO gases from automobile emission with respect to the copper content and morphology. The obtained results indicate that the presence of optimum amount of copper in ceria with flower-like morphology is essential for the removal of CO, HCxand NO at low temperature via redox process, which is due to the presence of active sites on the dominant {100} plane.

Thermal fatigue behavior of 441 ferritic stainless steel in air and synthetic automotive exhaust gas

The thermal fatigue behavior of 441 ferritic stainless steel was investigated in air and synthetic automotive exhaust gas by the cyclic tests under 100℃-800℃ and 900℃ conditions.After the fracture failure,the microstructure,oxide film,and precipitated phases were analyzed using optical microscopy,X-ray diffraction,scanning electron microscopy,and transmission electron microscopy.In both atmospheres,increasing the maximum temperature from 800℃ to 900℃ results in lower strength and fatigue life and higher elongation and grain size.At the same maximum temperature,the thermal fatigue life of the specimen is lower in the synthetic exhaust gas than in the air.Both the higher maximum temperature and the synthetic exhaust gas facilitate fatigue failure.The failure mechanism is discussed according to the grain size,thermal stress,high-temperature oxidation rate,and the precipitation of secondary phases.Some precipitated carbides play an important role in the rapid fatigue failure of specimens in the synthetic exhaust gas.