The Ba(Ti,Zr)O3-based multilayer ceramic capacitors (MLCCs) with Ni electrodes, which meet the Electronic Industry Association Y5V standard (from −30° to 85°C, at a temperature capacitance coefficient between −82% and 22%), have been studied in view of the electrode-ceramic inter-diffusion by several microstructual techniques (scanning electron microscopy/transmission electron microscopy/high-resolution transmission electron microscopy (HRTEM)) with an energy-dispersive X-ray spectrometer (EDS). The EDS analysis shows that the elements' inter-diffusion took place along the metal–dielectric interface and the migration of Ni toward the dielectric layers dominated this process. The incorporation of Ni did not transform the crystal structure but introduced lattice distortions, which were characterized by HRTEM, X-ray diffraction, and EDS. The degree of Ni diffusion in the sample with the thinner dielectric layer was more severe. It was concluded from the results that the Ni diffusion is related to the formation of oxygen vacancies after the annealing process, which should be a noticeable factor in the degradation behavior and reliability of base metal electrode MLCCs. The factors influencing the inter-diffusion are also discussed. 相似文献
Catalytic cracking of butene to propene and ethene was investigated over HMCM-22 zeolite. The performance of HMCM-22 zeolite was markedly influenced by time-on-stream (TOS) and reaction conditions. A rapid deactivation during the first 1 h reaction, followed by a quasi-plateau in activity, was observed in the process along with significant changes in product distributions, which can be attributed to the fast coking process occurring in the large supercages of MCM-22.
Properly selected reaction conditions can suppress the secondary reactions and enhance the production of propene and ethene. According to the product distribution under different butene conversion, we propose a simple reaction pathway for forming the propene, ethene and by-products from butene cracking.
HMCM-22 exhibited similar product distribution with the mostly used high silica ZSM-5 zeolite under the same conversion levels. High selectivities of propene and ethene were obtained, indicating that the 10-member ring of MCM-22 zeolite played the dominant role after 1 h of TOS. However, MCM-22 exhibited lower activity and stability than that on high silica ZSM-5 zeolite with longer time-on-stream. 相似文献
Carbon black has recently been reported to act as an effective catalyst for methane decomposition and to exhibit stable catalytic behavior despite carbon deposition, and thus it can be used for CO2-free production of hydrogen from natural gas. In this work, various carbon blacks with different primary particle size were investigated with respect to methane decomposition under atmospheric pressure from 1123 to 1223 K. Catalytic characteristics, such as activity, activation energy and reaction order, were investigated and compared. It was observed that with decreasing primary particle size (or increasing specific surface area), the specific activity increased and the activation energy decreased. The reaction orders for various pelletized, rubber-reinforcing carbon blacks were 0.6–0.7, about the same regardless of the primary particle size, while they were near 1 for fluffy carbon blacks. Fluffy carbon black showed higher activity and activation energy than the pelletized carbon black of the same primary particle size. Changes of the surface morphology during carbon deposition were observed by TEM. Variations of the number of active sites were discussed in regard of the primary particle size, carbon deposition and binder. The presence of different types of active sites was also suggested. 相似文献