The formation and evolution of corrosion product scales on 13Cr stainless steel at 200 °C and various CO2 partial pressures were investigated. Scanning electron microscope was used to show the physical nature of the scales formed at 0.27 MPa CO2. The thin non-uniform layer was identified as FeCr2O4 by Raman Spectroscopy with a thick Cr(OH)3 layer being determined at 2.85 MPa CO2. These results provide a guide to understanding the mechanisms of CO2 corrosion for 13Cr stainless steel exposed to high temperature and pressure and demonstrate the influence of thermodynamics and kinetics on the formation and evolution of the corrosion products.
Effect of tempering temperature on the composition of the passive film of a martensitic tool alloy was studied by synchrotron-based hard/soft X-ray photoelectron spectroscopy and electrochemical analyses. The contents of Cr and Mo in the passive film are affected by precipitation of tempering carbides. Increase of tempering temperature from 200 to 525°C leads to enhanced formation of Cr/Mo-rich tempering carbides and Cr depletion. Tempering at 525°C results in a Cr content < 11 at.% in the underlying metallic layer and formation of a Cr-deficient defective passive film, and thus loss of passivity for the tool alloy in corrosive conditions.
The formation and evolution of the corrosion scales on the super 13Cr stainless steel (SS) surface after exposure in a formate completion fluid with the presence of various aggressive substances was investigated. The results indicate that the formation of Fe 3 O 4 covered the surface of super 13Cr SS as the inner layer accompanied with outer scattered FeS. The corrosion rate was below 0.07 mm/year after 120 h of exposure in the formate fluid at 180°C under N 2 environments; the presence of aggressive substances such as sulfide and CO 2 in the formate fluid promoted the proceeding of anodic dissolution in the early period, and the ingress of CO 2 progressively increased the general corrosion rate to 1.7 mm/year. For CO 2 -containing conditions, the formation of FeCr 2 O 4 and Cr(OH) 3 was detected in the inner corrosion product layers, and the precipitation of “sheet”-shaped iron carbonate (FeCO 3 ) was detected as the outer layer. The accumulation rate of corrosion products increases by two orders of magnitude with the ingress of CO 2 , corresponding to thicker corrosion products, but the dissolution rate is still three orders of magnitude higher than when CO 2 was absent.
Mesoporous carbon with a high specific surface area (1,342.8m 2 /g) and a high mesopore volume (1.396 cm 3 /g) was prepared from Novalac phenol-formaldehyde resin as a carbon source, with F127 and nanosized silica as templates, followed by carbonization at high temperature.For comparison, other mesoporous carbon materials were prepared with only one template.The application of these mesoporous carbon materials and a commercial activated carbon for ciprofloxacin (CIP) removal from aqueous solution was investigated.At a low CIP concentration, the maximum adsorption of CIP on the mesoporous carbon was as high as 243.91 mg/g, which was the largest among these carbon materials and higher than that in literature.The adsorption capacities of these carbon adsorbents increased with an increase in mesopore volume.The equilibrium adsorption data were well described by the Langmuir isotherm.The adsorption kinetics followed a pseudo-second-order kinetic model.The effect of pH on the CIP adsorption was studied to investigate the adsorption mechanism.
Abstract Corrosion results in large costs and environmental impact but can be controlled by thin oxide films that passivate the metal surfaces and hinder further oxidation or dissolution in an aqueous environment. The structure, chemistry, and thickness of these oxide films play a significant role in determining their anti-corrosion properties and the early-stage oxidation dynamics affect the properties of the developed oxide. Here, we use in situ X-ray Photoelectron Spectroscopy (XPS) to study the early-stage oxidation of a Ni-Cr-Mo alloy at room temperature and up to 400 °C. Cr and Mo begin to oxidize immediately after exposure to O 2 , and Cr 3+ , Mo 4+ , and Mo 6+ oxides are formed. In contrast, Ni does not contribute significantly to the oxide film. A self-limiting oxide thickness, which did not depend on temperature below 400 °C, is observed. This is attributed to the consumption of available Cr and Mo near the surface, which results in an enrichment of metallic Ni under the oxide. The self-limited oxide thickness is 6–8 Å, which corresponds to 3–4 atomic layers of cations in the oxide. At 400 °C, sublimation of Mo 6+ oxide is observed, resulting in the formation of an almost pure layer of Cr 2 O 3 on the alloy surface. Lastly, a mechanism is presented that explains the formation of the bi-layer oxide structure observed for Ni-Cr-Mo alloys, which involves the enhanced migration of hexavalent Mo ions in the electric field, which drives mass transport during oxidation according to both the Cabrera Mott model and the Point Defect Model.
Carotenoid cleavage oxygenases (CCOs) include the carotenoid cleavage dioxygenase (CCD) and 9-cis-epoxycarotenoid (NCED), which can catalize carotenoid to form various apocarotenoids and their derivatives, has been found that play important role in the plant world. But little information of CCO gene family has been reported in litchi (Litchi chinensis Sonn.) till date. In this study, a total of 15 LcCCO genes in litchi were identified based on genome wide lever. Phylogeny analysis showed that LcCCO genes could be classified into six subfamilies (CCD1, CCD4, CCD7, CCD8, CCD-like, and NCED), which gene structure, domain and motifs exhibited similar distribution patterns in the same subfamilies. MiRNA target site prediction found that there were 32 miRNA target sites in 13 (86.7%) LcCCO genes. Cis-elements analysis showed that the largest groups of elements were light response related, following was plant hormones, stress and plant development related. Expression pattern analysis revealed that LcCCD4, LcNCED1, and LcNCED2 might be involving with peel coloration, LcCCDlike-b might be an important factor deciding fruit flavor, LcNCED2 and LcNCED3 might be related to flower control, LcNCED1 and LcNCED2 might function in fruitlet abscission, LcCCD4a1, LcCCD4a2, LcCCD1, LcCCD4, LcNCED1, and LcNCED2 might participate in postharvest storage of litchi. Herein, Genome-wide analysis of the LcCCO genes was conducted in litchi to investigate their structure features and potential functions. These valuable and expectable information of LcCCO genes supplying in this study will offer further more possibility to promote quality improvement and breeding of litchi and further function investigation of this gene family in plant.
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