Search

Your search keyword '"Xi, Dongyang"' showing total 34 results
Start Over Author "Xi, Dongyang"
34 results on '"Xi, Dongyang"'

2. Evaluation and Prediction of Urban Shrinkage in Liaoning Province Based on Grey Theory

Author

Ding, Benzhe, Xi, Dongyang, Yan, Tingting, Zhao, Qimeng, Wu, Xiangxin, Li, Kan, Editor-in-Chief, Li, Qingyong, Associate Editor, Fournier-Viger, Philippe, Series Editor, Hong, Wei-Chiang, Series Editor, Liang, Xun, Series Editor, Wang, Long, Series Editor, Xu, Xuesong, Series Editor, Yen, Jerome, editor, Abedin, Mohammad Zoynul, editor, and Wan Ngah, Wan Azman Saini Bin, editor

Published
2023
Full Text
View/download PDF

4. Pressure-Induced Structural Phase Transition and Fluorescence Enhancement of Double Perovskite Material Cs 2 NaHoCl 6.

Author

Yan, Tingting, Liu, Linan, Xi, Dongyang, Sun, Lei, Jin, Dinghan, and Li, Han

Subjects
PHASE transitions, CHEMICAL bond lengths, SINGLE crystals, DENSITY functional theory, HYDROTHERMAL synthesis
Abstract

Cs2NaHoCl6, a double perovskite material, has demonstrated extensive application potential in the fields of anti-counterfeiting and optoelectronics. The synthesis of Cs2NaHoCl6 crystals was achieved using a hydrothermal method, followed by the determination of their crystal structures through single crystal X-ray diffraction techniques. The material exhibits bright red fluorescence when exposed to ultraviolet light, confirming its excellent optical properties. An in situ high-pressure fluorescence experiment was conducted on Cs2NaHoCl6 up to 10 GPa at room temperature. The results indicate that the material possibly undergoes a structural phase transition within the pressure range of 6.9–7.9 GPa, which is accompanied by a significant enhancement in fluorescence. Geometric optimization based on density functional theory (DFT) revealed a significant decrease in the bond lengths and crystal volumes of Ho-Cl and Na-Cl across the predicted phase transition range. Furthermore, it was observed that the bond lengths of Na-Cl and Ho-Cl reach an equivalent state within this phase transition interval. The alteration in bond length may modify the local crystal field strength surrounding Ho3+, consequently affecting its electronic transition energy levels. This could be the primary factor contributing to the structural phase transition. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

9. Pressure-Induced Structural Phase Transitions and Photoluminescence Properties of Micro/Nanocrystals HoF3

Author

Yan, Tingting, Zhang, Dandan, Xi, Dongyang, Zhao, Yu, Wang, Chengyu, Jiang, Ran, and Xu, Yifei

Abstract

HoF3crystals of varying sizes and morphologies were synthesized by controlling the amount of water. As the water content gradually decreased, the size of the crystals reduced, transforming from microcrystals to approximately 100 nm nanocrystals with unique morphologies. At room temperature, the pressure-induced phase transitions, and photoluminescence (PL) properties of HoF3micro/nanocrystals are studied using in situ high-pressure PL technique. The PL spectra show that the HoF3micro/nanocrystals exhibit two structural phase transformations at 5 (6 GPa for NCs) and 12 GPa. Nanoparticles have higher fluorescence intensity, which initially increases and then decreases with changes in pressure. Based on first-principles calculations, HoF3transforms from an orthorhombic structure to a hexagonal structure during the phase transition, with the coordination number of holmium atoms increasing from 9 to 11. The high-pressure Raman spectra on lattice modes also confirmed the existence of the two phase transitions. This work not only provides precise structural changes but also facilitates the understanding of two typical structures of rare-earth trifluoride (REF3), which may play an important role in the application of the RE family.

Published
2024
Full Text
View/download PDF

27. High performance nanosheet-like silicoaluminophosphate molecular sieves : synthesis, 3D EDT structural analysis and MTO catalytic studies

Author

Sun, Qiming, Ma, Yanhang, Wang, Ning, Li, Xu, Xi, Dongyang, Xu, Jun, Deng, Feng, Yoon, Kyung Byung, Oleynikov, Peter, Terasaki, Osamu, Yu, Jihong, Sun, Qiming, Ma, Yanhang, Wang, Ning, Li, Xu, Xi, Dongyang, Xu, Jun, Deng, Feng, Yoon, Kyung Byung, Oleynikov, Peter, Terasaki, Osamu, and Yu, Jihong

Abstract

Nanosheet-like silicoaluminophosphate (SAPO) molecular sieves SAPO-34 (CHA-type) and SAPO-18 (AEI-type) with different silicon contents were synthesized under hydrothermal conditions by using tetraethylammonium hydroxide as the template. Three-dimensional electron diffraction tomography (3D EDT) technique was applied for ab initio structure solutions. Electron microscopy observations confirmed the existence of defects, i.e., intergrowth of CHA- and AEI-type frameworks caused by the different stacking manners of double 6-ring layers, but the layers were highly coherent along c direction. Compositions, acidities, chemical environments, and texture properties of all the samples were characterized by ICP, EDS, NH3-TPD, MAS NMR, and N-2 adsorption-desorption measurements. The catalytic performances of methanol-to-olefin (MTO) reactions over nano SAPO catalysts with different silicon contents were systematically studied. All of these catalysts showed excellent catalytic activity, among which SAPO-34 showed superior catalytic performance compared to SAPO-18. DFT calculations were utilized to study the different catalytic performance of CHA and AEI. Significantly to date, SAPO-34 with the lowest silicon content exhibited the longest catalyst lifetime and the lowest coking rate in the MTO reaction than any of the reported catalysts, tested under similar conditions. The straight 8-ring pore channel along the c direction provided the optimum diffusion pathway as well as the shortest diffusion length for reactant and generated olefins, thus significantly reduced the coking rate. This work demonstrates that a 3D EDT approach combined with TEM and EDS analysis from a single nanocrystal can provide a clear crystal structure, crystal orientation and compositional information of nanocrystals, which are useful for the better understanding of the catalytic performance of nanosized crystalline catalysts., AuthorCount:11

Published
2014
Full Text
View/download PDF

34. Experimental Study on the Lubrication and Cooling Effect of Graphene in Base Oil for Si 3 N 4 /Si 3 N 4 Sliding Pairs.

Author

Zhang L, Wei X, Wang J, Wu Y, An D, and Xi D

Abstract

Recently, the engineering structural ceramics as friction and wear components in manufacturing technology and devices have attracted much attention due to their high strength and corrosion resistance. In this study, the tribological properties of Si 3 N 4 /Si 3 N 4 sliding pairs were investigated by adding few-layer graphene to base lubricating oil on the lubrication and cooling under different experimental conditions. Test results showed that lubrication and cooling performance was obviously improved with the addition of graphene at high rotational speeds and low loads. For oil containing 0.1 wt% graphene at a rotational speed of 3000 r·min -1 and 40 N loads, the average friction coefficient was reduced by 76.33%. The cooling effect on Si 3 N 4 /Si 3 N 4 sliding pairs, however, was optimal at low rotational speeds and high loads. For oil containing 0.05 wt% graphene at a lower rotational speed of 500 r·min -1 and a higher load of 140 N, the temperature rise was reduced by 19.76%. In addition, the wear mark depth would decrease when adding appropriate graphene. The mechanism behind the reduction in friction and anti-wear properties was related to the formation of a lubricating protective film., Competing Interests: The authors declare no conflict of interest.

Published
2020
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results