When alumina is produced by the Bayer process with high-sulfur bauxite, the sulfur would strongly corrode the 12Cr1MoV steel made heat exchanger. This study investigated the initial corrosion behavior of the 12Cr1MoV steel exposed to a thiosulfate-containing sodium aluminate (TCSA) solution under the evaporation conditions of alumina production. The obtained corrosion rate equation is V = 6.306·t·exp(−0.71). As corrosion progressed, with the corrosion product film growing, the corrosion current density declines slowly, and the corrosion resistance of the steel is increased. At 1–3 days, the corrosion product film consisted of FeO, Fe2O3, and FeOOH. S2O32− lead to corrosion in local areas of the steel and pits appeared. AlO2− is transformed into Al(OH)3 and filled in the corrosion pits. At 4 and 5 days, Fe3O4 is generated in the outermost layer, and Al(OH)3 is shed from the corrosion pits. The corrosion mechanism of 12Cr1MoV steel in a TCSA solution is proposed based on the experimental results.
During Bayer alumina production with high-sulfur bauxite, the sulfide ions in the sodium aluminate solution caused serious corrosion to Q235 steel, which is the material of the tank equipment. This study investigates the effect of corrosion time on Q235 steel synergistic corrosion in sodium aluminate solution using the weight-loss method and electrochemical measurements. The results indicate that the corrosion rate decreases sharply, the rate equation satisfies the mathematical model of power function at the initial stage of corrosion, and the transformation of unstable iron sulfide to stable iron oxide at the later stage results in the decrease in sulfur content in the corrosion products and surface pseudo-passivation. There are two main types of corrosion products, as follows: one is the octahedral crystal particle, which is composed of Fe2O3, Fe3O4, Al2O3 and NaFeO2, and the other is the interlayer corrosion between the surface layer and the matrix, which is composed of FeS, FeS2 and MnS2. At day 3, the dynamics of the Q235 steel electrode is controlled by charge transfer and ion diffusion. However, at other times the dynamics are mainly controlled by charge transfer.
Well-defined hollow spherical TiO2 with mesoporous structure have been synthesized via a facile combination of sol-gel and solvothermal processes. The solvothermally treated mesoporous TiO2 hollow mi- crospheres were found to have a high crystallinity with a nanocrystalline anatase structure, whereas untreated materials were found to have an amorphous phase. XRD, SEM, TEM and N2 adsorption were used to charac- terize the morphology and crystalline phase of the mesoporous TiO2 hollow microspheres. Structural charac- terization indicates that these mesoporous TiO2 hollow microspheres have an obvious mesoporous structure with an average diameter of about 1m. The average pore sizes and BET surface areas of the mesoporous TiO2 hollow microspheres are 16.5nm and 90.1m 2 /g, respectively.
Morphological tuning or additional cation doping is one of the potential and simple methods to enhance the photocatalytic properties of ceria, in which rare-earth element doped ceria nanorods (CeO2-RE NRs) are expected to be a promising photocatalyst with high activity. But the optimal doping conditions, including the variety and concentration of RE elements are ambiguous, and the contribution of doped RE ions to the enhancement of photocatalytic activity needs to be further studied. In this work, we doped La, Y and Sm with a wide range of 0%-30% into CeO2 NRs, and investigated the phase, morphology, band gap, oxygen vacancy concentration, PL spectra and photocatalytic activity variation under different doping conditions. All synthesized CeO2-RE NRs possessed a good nanorod morphology except the 15 and 30% Y-doped samples. The energy band gaps of the synthesized samples changed slightly; the 10% CeO2-RE NRs with the narrowest band gaps possessed the higher photocatalytic performance. The most outstanding photocatalyst was found to be the 10% Y-doped CeO2 NRs with a methylene blue photodegradation ratio of 85.59% and rate constant of 0.0134 min-1, which is particularly associated with a significant higher oxygen vacancy concentration and obviously lower recombination rate of photogenerated e-/h+ pairs. The doped RE ions and the promotion of oxygen vacancy generation impede the recombination of photogenerated carriers, which is proposed as the main reason to enhance the photocatalytic property of CeO2.
Abstract Here, we elucidate the interaction between IAA and melatonin (MT) in response to chilling in cucumber. The results showed that chilling stress induced the increase of endogenous MT and IAA, and the application of MT promoted the synthesis of IAA, while IAA could not affect endogenous MT content under chilling stress. Moreover, MT and IAA application both remarkably increased the chilling tolerance of cucumber seedlings in terms of lower contents of MDA and ROS, higher mRNA abundance of cold response genes, net photosynthetic rate ( P n ), maximum regeneration rate of ribulose‐1,5‐diphosphate (J max ), Rubisco maximum carboxylation efficiency (V cmax ), the activities and gene expression of RCA and Rubisco, as well as the content of active P700 (I/I 0 ) and photosynthetic electron transport, compared with the plants in H 2 O treatment. Further analysis revealed that the inhibition of IAA transportation significantly reduced the chilling tolerance induced by MT, whereas the inhibition of endogenous MT did not affect the chilling tolerance induced by IAA. Meanwhile, we found that overexpression of the MT biosynthesis gene CsASMT increased the chilling tolerance, which was blocked by inhibition of endogenous IAA, and the silence of IAA biosynthesis gene CsYUCCA10 decreased the chilling tolerance of cucumber, which could not be alleviated by MT. These data implied IAA acted as a downstream signal to participate in the MT‐induced chilling tolerance of cucumber seedlings. The study has implications for the production of greenhouse cucumber in winter seasons.
Abstract The nonstoichiometric metal oxide Ni 0.3 Co 2.7 O 4 served as a support for small‐sized Pt nanoparticles. The whole synthesis of the hybrid material can be kinetically controlled and no further surface‐modification treatment was required. More importantly, the as‐obtained strongly coupled PtNi 0.3 Co 2.7 O 4 hybrid nanoflowers exhibit remarkably enhanced catalytic activities compared with PtNiO and PtCo 3 O 4 hybrid samples. This result indicates that it is possible to optimize the catalytic performance of noble metals by using a nonstoichiometric metal oxides as a support instead of a stoichiometric metal oxide.
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