| 1. |
- Yu, Jiangfei, et al.
(författare)
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Onset of cellular flame instability in adiabatic CH4/O-2/CO2 and CH4/air laminar premixed flames stabilized on a flat-flame burner
- 2013
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 160:7, s. 1276-1286
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents numerical and experimental studies on the onset and evolution of laminar cellular flames of CH4/O-2/CO2 (oxy-fuel) and CH4/air mixtures under adiabatic conditions, stabilized in the proximity of a flat-flame burner at atmospheric pressure. In the numerical simulations, a two-dimensional domain with periodicity at the transverse far field boundaries is resolved using a high accuracy finite difference method and employing a detailed chemical kinetic mechanism and detailed transport properties. In the experiments a specially designed adiabatic flat-flame burner, a so-called heat flux burner, is employed. A key parameter, the standoff distance between the flame front and the burner exit plate, is identified. A critical standoff distance is found, above which cellular flame instability is observed. It is shown that the critical standoff distance is closely related to the density ratio and the laminar flame thickness for each flame studied. The observed onset of cellular flames is governed by the hydrodynamic instability mechanism, which is generally suppressed by the burner when the flame is very close to the burner plate. Diffusive-thermal effects play an important role in the flame instability when the flame is far from the burner. The critical standoff distance has no clear correlation with the Lewis number, indicating a less significant effect of diffusive-thermal instability on the flames near the burner. (c) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 2. |
- Gong, Haiqing, et al.
(författare)
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Synergies in sustainable phosphorus use and greenhouse gas emissions mitigation in China: : Perspectives from the entire supply chain from fertilizer production to agricultural use
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; , s. 155997-155997
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Tidskriftsartikel (refereegranskat)abstract
- Synergies to achieve high phosphorus (P) use efficiency (PUE) and mitigate greenhouse gas (GHG) emissions are critical for developing strategies aimed toward agricultural green development. However, the potential effects of such synergies in the entire P supply chain through optimizing P management in crop production are poorly understood. In this study, a partial life cycle of a GHG emissions model was developed to quantify the P-related GHG emissions in the entire P supply chain in China. Our results showed that 16.3 kg CO2-equivalent (CO2-eq) was produced from the entire P supply chain per unit of P used for grain agriculture (maize, rice, and wheat). P-related GHG emissions in China increased more than five-fold from 1980 (7.2 Tg CO2-eq) to 2018 (44.9 Tg CO2-eq). GHG emissions were found to be strongly associated with the intensity of grain production in China, and they varied considerably across production regions owing to the differences in the P fertilizer production efficiency. Mineral P fertilizer use in crop production was the primary source of P-related GHG emissions. The results suggest that sustainable P management by matching mineral P fertilizer rates and fertilizer types with crop needs can mitigate GHG emissions by 10.8–27.7 Tg (24.0–65.1%). Moreover, this can improve PUE and reduce mineral P input by 0.7–1.4 Tg (24.0–46.0%). These findings highlight that potential synergies between high PUE and low P-related GHG emissions can be achieved via sustainable P management, thereby enhancing green agricultural development in China and other regions worldwide.
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| 3. |
- Parbey, Joseph, et al.
(författare)
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Progress in the use of electrospun nanofiber electrodes for solid oxide fuel cells : A review
- 2019
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Ingår i: Reviews in Chemical Engineering. - : Walter de Gruyter GmbH. - 2191-0235 .- 0167-8299. ; 36:8, s. 879-931
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Tidskriftsartikel (refereegranskat)abstract
- The application of one-dimensional nanofibers in the fabrication of an electrode greatly improves the performance of solid oxide fuel cells (SOFCs) due to its advantages on electron transfer and mass transport. Various mixed ionic-electronic conducting materials with perovskites and Ruddlesden-Popper-type metal oxide structures are successfully electrospun into nanofibers in recent years mostly in solvent solution and some in melt forms, which are used as anode and cathode electrodes for SOFCs. This paper presents a comprehensive review of the structure, electrochemical performance, and development of anode and cathode nanofiber electrodes including processing, structure, and property characterization. The focuses are first on the precursor, applied voltage, and polymer in the material electrospinning process, the performance of the fiber, potential limitation and drawbacks, and factors affecting fiber morphology, and sintering temperature for impurity-free fibers. Information on relevant methodologies for cell fabrication and stability issues, polarization resistances, area specific resistance, conductivity, and power densities are summarized in the paper, and technology limitations, research challenges, and future trends are also discussed. The concluded information benefits improvement of the material properties and optimization of microstructure of the electrodes for SOFCs.
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| 4. |
- Tian, Yupeng, et al.
(författare)
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Two novel two-photon polymerization initiators with extensive application prospects
- 2004
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 388:4-6, s. 325-329
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Tidskriftsartikel (refereegranskat)abstract
- Two novel two-photon polymerization initiators, 10-ethyl-3-E-(4-(N,N′-di-n-butylamino)styryl)phenothiazine 5 and 10-ethyl-3,7-E,E-bis(4-(N,N′-di-n-butyl amino)styryl)phenothiazine 6, have been efficiently synthesized with room temperature solid phase Wittig reaction. Two initiators were found to exhibit good single-photon fluorescence emission and their quantum yields, lifetimes and solvent effects have been studied in detail. Two-photon fluorescence spectra were investigated under 800 nm fs laser pulse and two-photon absorption (TPA) cross-sections of the initiators have been evaluated by theoretical calculation.Two-photon initiating polymerization microfabrication experiments have been carried out and artificial defects were made and polymerization mechanism was also discussed.
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| 5. |
- Zhang, Xiaoqiang, et al.
(författare)
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Mechanism of chromium poisoning the conventional cathode material for solid oxide fuel cells
- 2018
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 381, s. 26-29
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Tidskriftsartikel (refereegranskat)abstract
- Chromium poisoning the La0.875Sr0.125MnO3 (LSM) cathode for solid oxide fuel cells is a critical issue that can strongly affect the stability. In this study, we evaluate the temperature distribution in a SOFC based on a 3D model and then combine conductivity test and material computation to reveal the effects of chromium in SUS430 stainless steels on LSM conductivities. The starch concentration in LSM pellets and the applied pressure on the contact with interconnect materials show close relationships with the chromium poisoning behavior. The density functional theory (DFT) computing results indicate that chromium atoms preferably adsorb on the MnO2-terminated and La (Sr)-O-terminated (001) surfaces. The resulting conclusions are expected to deeply understand mechanism of chromium deactivating conventional cathodes at some typical operational conditions, and offer crucial information to optimize the structure to avoid the poisoning effect.
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| 6. |
- Zhang, Xiaoqiang, et al.
(författare)
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Thermal stress analysis at the interface of cathode and electrolyte in solid oxide fuel cells
- 2020
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Ingår i: International Communications in Heat and Mass Transfer. - : Elsevier BV. - 0735-1933. ; 118
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Tidskriftsartikel (refereegranskat)abstract
- A benign thermal stress in solid oxide fuel cell is of great importance for its stability and the interfaces between different components suffer from unexpected risks of instability such as electrode delamination and crack due to varying thermal expansion coefficients. Besides, chromium poisoning cathode materials leads to phase changes, which possibly induces thermal stresses at the interface of electrolyte and cathode. A three dimensional model at the microscale level is thus developed to unravel the effect of thermal stress on the interface. The model is constructed by governing equations including heat, species, momentum, ion and electronic transportation. The contact modes between the active cathode and electrolyte are studied to reveal the cell performance and thermal stresses, which are strongly related to the number of contact sites and the contact area. Moreover, chromium poisoning the contact causes the disordered distribution of thermal stresses with the increase of the contact sites, worsening the cell current density and durability. The resulting conclusions are expected to offer a solution to avoid possible fatal mechanical failure due to unfavorable interface design and chromium attack.
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| 7. |
- Zhang, Xiaoqiang, et al.
(författare)
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Thermal stress analysis of solid oxide fuel cells with chromium poisoning cathodes
- 2018
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 165:14, s. 1224-1231
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Tidskriftsartikel (refereegranskat)abstract
- Chromium(Cr) poisoning of the traditional LSM cathode is one of the most critical issues that accounts for instability of solid oxide fuel cells (SOFCs). The poisoning course will introduce alien species in the cathode active regions and it causes phase change and structure deformation, reducing the sites for electrochemical reactions. A 3D model is thus developed by coupling the computational fluid dynamics (CFD) approach with the finite element method to unravel the involved electrochemical processes in chromium poisoning of SOFCs. A function is proposed based on the experimental results to describe the distribution of Cr-related compounds in cathode. The results indicate that chromium poisoning can induce a dramatic decrease in the electric current density, which can also lead to increase of activation polarizations and lower the temperature. Three kinds of thermal stresses are strongly affected by the invasion of chromium into cathodes, which are all significantly reduced with the poisoning extent. The resulting conclusions are beneficial to deeply understand the Cr poisoning of SOFCs and also to material design to prevent cathodes from Cr-based interconnect attack.
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