Yiqing Zeng,Yanan Wang,Shule Zhang,Qin Zhong,Weilong Rong,Xiaohai Li
In this work, novel (CeO 2 ) x -(CePO 4 ) 1−x (defined as Ce x P 1−x ) nanorod composites were prepared by a simple co-precipitation method, and the influence of CeO 2 on the catalytic performance of CePO 4 for selective catalytic reduction of NO by NH 3 (NH 3 -SCR of NO) was investigated. The catalytic performance evaluation revealed that the Ce x P 1−x catalysts, especially Ce 0.2 P 0.8 exhibited a much better catalytic activity and H 2 O + SO 2 resistance than CePO 4 . Structure characterizations via high-resolution transmission electron microscope (HRTEM) and Brunauer-Emmett-Teller (BET) revealed that the introduction of CeO 2 had a little effect on the shape of CePO 4 nanorods and it could promote the formation of new mesoporous then significantly enhance the surface area of catalyst. The analysis results of active sites suggested that phosphorus was the main adsorption site for NH 3 and the redox sites were controlled by CeO 2 on Ce x P 1−x catalysts. Finally, reaction process study demonstrated that the NH 3 -SCR over Ce x P 1−x was processed via Langmuir-Hinshelwood (L-H) mechanism. Combining the results of active sites and reaction mechanism analysis, it was drawn that the superior low temperature activity of Ce x P 1−x could be attributed to its excellent redox properties, which promoted the oxidation of NO then facilitated the process of NH 3 -SCR via “fast SCR”.
Chao Yang,Tao Ying,Aihui Huang,Jian Huang,Pinghu Chen,Paul K. Chu,Xiaoqin Zeng
Corrosion of aluminum (Al) alloys during service limits many applications. Micro-arc oxidation (MAO) coatings can enhance corrosion resistance, but porous defects in the films undermine their effectiveness. Here, by mixing a phosphate electrolyte with soluble Zn and Ce salts, zinc phosphate and cerium phosphate co-doped MAO corrosion-resistant coating is prepared on Al alloy LY12. Zinc phosphate and cerium phosphate are incorporated in situ to form an amorphous encapsulated nanocrystalline structure. During long-term corrosion, Zn 2+ is released and deposited as corrosion products Zn(OH) 2 to cover weak corrosion micro-regions in the coating. Simultaneously, Ce 3+ released from MAO coating co-doped with zinc phosphate/cerium phosphate forms Zn(OH) 2 /Ce(OH) 3 due to the small solubility product K sp to further enhance corrosion resistance. Compared to pristine Al alloy, corrosion potential increases from -1.306 to -0.819 V SCE , and corrosion current density decreases by 4 orders of magnitude from 2.6 × 10 −6 to 2.5 × 10 −10 A·cm −2 . Co-doped MAO coating significantly enhances corrosion resistance of Al alloy LY12 and shows great potential for a wide range of applications.
Composite ceramics, which integrate the advantages of multiple crystal structures, are considered promising candidates for nuclear waste forms capable of simultaneously immobilizing various radionuclides. In this study, a series of 0.4Sr 0.5 Zr 2 (PO 4 ) 3 –0.6Ce 1- x Nd x PO 4 composite ceramics were designed to co-immobilize the simulated fission product Sr and actinide surrogates Ce and Nd. These composite ceramics exhibited homogeneous phase distribution and high densification. Among them, the irradiation-induced damage in the representative sample, 0.4Sr 0.5 Zr 2 (PO 4 ) 3 –0.6Ce 0.6 Nd 0.4 PO 4 composite ceramic, was systematically evaluated under both He 2+ and Xe 20+ irradiation. After He 2+ irradiation, the crystallinity of the irradiated layer was retained despite the disruption of Raman-active bonding groups by point defects. Notably, the Ce 0.6 Nd 0.4 PO 4 phase exhibited significantly higher resistance to He 2+ irradiation than the Sr 0.5 Zr 2 (PO 4 ) 3 phase, as confirmed by GIXRD patterns and geometric phase analysis (GPA). Furthermore, fragmentation of Ce 0.6 Nd 0.4 PO 4 grains was observed, which was attributed to defect accumulation, the thermal spike effect, and the thermal expansion mismatch. Following Xe 20+ irradiation, the irradiated layer of the composite ceramic exhibited reduced crystallinity without complete amorphization, while the Raman-active bonding groups remained largely intact. Additionally, pore formation at grain boundaries was likely caused by the segregation and accumulation of irradiation-induced defects.
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