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1.
《Ceramics International》2022,48(4):4401-4423
Nano-zirconia has been widely applied due to its excellent physical and chemical properties (e.g., high strength, corrosion resistance, oxygen ion conductivity). Existing preparation methods of nano-zirconia tend to require long reaction time, and the sizes of final particles are large with uneven distributions. Sub-/supercritical hydrothermal synthesis of nanoparticles is favored by researchers owing to controllable reaction process, uniform particle size distribution, good reproducibility, short reaction time, high conversion rate and harmlessness to environment. In this paper, the characteristics and mechanisms of dissolution, crystallization and growth of nano-zirconia during sub-/supercritical hydrothermal synthesis are systematically reviewed. The influences of process and material parameters on the size and purity of particles are analyzed. Then, the reaction mechanism and product phase transition mechanism during hydrothermal synthesis of zirconia are summarized to provide a theoretical reference for the oriented preparation. Finally, the improvement and commercialization of sub-/supercritical hydrothermal synthesis technology are evaluated, and the future research topics are proposed. 相似文献
2.
Colleen Varaidzo Manyumwa
zlem Tastan Bishop 《International journal of molecular sciences》2021,22(6)
Carbonic anhydrases (CAs) have been identified as ideal catalysts for CO2 sequestration. Here, we report the sequence and structural analyses as well as the molecular dynamics (MD) simulations of four γ-CAs from thermophilic bacteria. Three of these, Persephonella marina, Persephonella hydrogeniphila, and Thermosulfidibacter takaii originate from hydrothermal vents and one, Thermus thermophilus HB8, from hot springs. Protein sequences were retrieved and aligned with previously characterized γ-CAs, revealing differences in the catalytic pocket residues. Further analysis of the structures following homology modeling revealed a hydrophobic patch in the catalytic pocket, presumed important for CO2 binding. Monitoring of proton shuttling residue His69 (P. marina γ-CA numbering) during MD simulations of P. hydrogeniphila and P. marina’s γ-CAs (γ-PhCA and γ-PmCA), showed a different behavior to that observed in the γ-CA of Escherichia coli, which periodically coordinates Zn2+. This work also involved the search for hotspot residues that contribute to interface stability. Some of these residues were further identified as key in protein communication via betweenness centrality metric of dynamic residue network analysis. T. takaii’s γ-CA showed marginally lower thermostability compared to the other three γ-CA proteins with an increase in conformations visited at high temperatures being observed. Hydrogen bond analysis revealed important interactions, some unique and others common in all γ-CAs, which contribute to interface formation and thermostability. The seemingly thermostable γ-CA from T. thermophilus strangely showed increased unsynchronized residue motions at 423 K. γ-PhCA and γ-PmCA were, however, preliminarily considered suitable as prospective thermostable CO2 sequestration agents. 相似文献
3.
4.
Yumio Yato 《Journal of Nuclear Science and Technology》2019,56(4):311-316
When UF6 is handled in leak tight system, the amount of uranium compound formed on the surface of containers, valves, and others in UF6 handling facilities is not so significant for a short term that special attention has not been given to this problem. The present work was done to throw some more light on this problem based on the recent experiment. We discuss the possibility that the intermolecular transfer of a fluorine atom from UF6 to UF5 may participate in the formation of uranium compound. The discussion includes also the unique features contained in the experimental result, the reaction processes assumed in this problem, and the derivation of a rate equation for expressing the deposition of uranium compound. Furthermore, we propose a new method for determining nonlinear parameters included in a governing differential equation having two variables for expressing the deposition of uranium compound from experimental raw data. 相似文献
5.
Replacement of precious single metal catalysts with cost-effective, highly-dispersed composite catalysts for catalytic hydrothermal conversion of residue holds tremendous promise for the residue upgrading technologies. Organic metals were added to the feed as the oil-soluble precursors, and transformed into the catalytic active phases in this work. Physical properties and structures of the composite catalysts had been investigated by X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope and transmission electron microscopy. The composite catalysts were found to be highly efficient in the catalytic hydrothermal conversion of both model compound and residue. Increased metal dispersion and synergistic effects of two metals played indispensable roles in such catalytic system. Results showed that under the test conditions in the article, the catalyst had the best catalytic performance when the mass ratio of molybdenum to iron was 1.5. 相似文献
6.
豫西熊耳山雷门沟钼矿床位于东秦岭多金属成矿带东段,是已探明的超大型斑岩型钼矿,前人研究程度高、地质成果丰硕,但对矿床开采技术条件方面研究较少。本次通过地质调查工程、水文地质试验等方法,从水文地质角度,对雷门沟钼矿床水文地质条件进行研究,填补了该方面的空白,丰富了研究成果;采用水文地质比拟法预测未来矿坑最大排水量2613 m3/d,经实践检验结果较为可靠;总结的采坑排水量预测方法、含水层特点、矿床充水因素以及防治水措施,以期对该区域水文地质工作具有参考价值。 相似文献
7.
Ying Chen HuiLi Zhang YuNing Liang YanHua Gao Yongchao Li 《Petroleum Science and Technology》2019,37(7):787-795
In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co2+/F-/TiO2 nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co2+/F-/TiO2 revealed improved photocatalytic performance for denitrification of light oil compared to single TiO2 photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co2+ and F? in the photocatalyst. 相似文献
8.
Wax deposit properties are a significant concern in pipeline pigging during waxy crude oil transportation. In the present work, the impacts of flow conditions and oil properties on the wax precipitation characteristics of wax deposits are investigated. A flow loop apparatus was developed to conduct wax deposition experiments using four crude oils collected from different field pipes. The differential scanning calorimetry (DSC) technique was employed to observe the wax precipitation characteristics of crude oil and wax deposit. The results show that the wax content and the wax appearance temperature (WAT) of the deposits increase with shear stress and radial temperature gradient, and decrease with radial wax molecule concentration gradient near the pipe wall. The DSC tests on the wax deposits revealed that the deposit wax content is strongly correlated to the oil wax content. Furthermore, an empirical correlation was developed to predict the wax content and the WAT of the wax deposit. Verification of the empirical correlation using the different oils indicated that the average relative error of the wax content prediction and average absolute error of WAT prediction were 13.2% and 3.6°C, respectively. 相似文献
9.
This paper presents two well-instrumented large-scale field tests of PVD-improved soft soil with vacuum and surcharge preloading, respectively. The two large-scale field tests were conducted adjacent to each other with the same preload. A comparative analysis was performed to investigate the performance of subsoil (i.e., the ground settlement, the layered settlement, the lateral displacement of subsoil and pore water pressure) under vacuum preloading and equivalent surcharge preloading. Some design methods were verified based on the field data. Cone Penetration Tests (CPT) and Vane Shear Tests (VST) were conducted to assess the improvement effects on subsoil after preloading. The results showed that as compared with surcharge preloading, vacuum preloading mitigated the differential settlement of the ground. The vacuum pressure transmitted into the soil with a minor loss through the PVD length. From a practical point of view, the improvement effects by vacuum preloading and surcharge preloading were similar in terms of influence depth and soil strength based on the in-situ tests. 相似文献
10.