| 1. |
- Li, Yunxiang, et al.
(författare)
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Nanocrystalline TON-type zeolites synthesized under static conditions
- 2018
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 256, s. 84-90
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Tidskriftsartikel (refereegranskat)abstract
- Pure-phase zeolites of the TON-type were synthesized under static hydrothermal conditions, which previously have, typically, required stirring during synthesis. Heterocyclic structure directing agents (SDAs) were observed to play important roles in both the selection of the polymorphs as well as in affecting the morphology of the particles formed. When an imidazole-based SDA was used snowflake shaped particles formed, which indicated a dendritic growth pattern of the zeolite. These zeolite particles possessed intercrystalline mesopores. To the best of our knowledge, it is for the first time that snowflake-shaped particles have been observed for TON-type zeolites. Other synthesis parameters were optimized to obtain crystals with short c-axes. The c-axis shortened with an increased solid concentration used during synthesis. This shortening was attributed to both the degree of supersaturation, and a change of the crystal growth mechanism. Short c-axes could increase the concentration of pore mouths in TON-type zeolites. Altogether, synthesis of nanocrystalline zeolites of the TON type under static condition could, potentially, be advantageous to large-scale production.
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| 2. |
- Xu, Chao, et al.
(författare)
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High-Performance Activated Carbons Synthesized from Nanocellulose for CO2 Capture and Extremely Selective Removal of Volatile Organic Compounds
- 2018
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Ingår i: Advanced Sustainable Systems. - : Wiley. - 2366-7486. ; 2:2
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Tidskriftsartikel (refereegranskat)abstract
- A series of sustainable activated carbons (ACs) with large surface areas and tunable pore sizes is synthesized from Cladophora cellulose and its chemically modified derivatives in a one-step physical carbonization/activation process. The molecular structure of the cellulose precursors and the carbonization/activation atmosphere (N-2 or CO2) significantly influence the pore structure of the ACs. When using oxidized cellulose and its further cross-linkages as the precursor, the ACs have a large volume of ultramicropores (pore diameter < 0.8 nm). Activation in CO2 results in ACs with surface areas up to 1241 m(2) g(-1). These ACs have a high CO2 uptake capacity (2.29 mmol g(-1) at 0.15 bar, 5.52 mmol g(-1) at 1 bar; 273 K) and a high CO2-over-N-2 selectivity (42 at 273 K). In addition, the capacity of the ACs to adsorb vapors of volatile organic compounds (VOCs) is remarkable, with values up to 0.97 mmol g(-1) at very low VOC concentrations (200 ppmv). The ACs have ultrahigh VOCs-over-N-2 selectivity up to 9.35 x 10(3) at 293 K for 0.02 vol%/99.8 vol% of benzene/N-2 mixture. It is anticipated that these ACs will be useful as sorbents for the postcombustion capture of CO2 and for indoor removal and direct air capture of various VOCs.
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| 3. |
- Zhang, Zhiqiang, et al.
(författare)
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Numerical Simulation of a Round Determinate Panel Test of Combined Concrete Panel and Welded Wire Mesh
- 2018
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Ingår i: Paper presented at the ISRM International Symposium - 10th Asian Rock Mechanics Symposium, Singapore, October 2018. - : International Society for Rock Mechanics and Rock Engineering / Society for Rock Mechanics and Engineering Geology.
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Konferensbidrag (refereegranskat)abstract
- The sprayed concrete layer, together with external welded wire mesh, has been widely used as an important surface support in underground excavation in civil and mining engineering. Recently, the load carrying capability of combined concrete layer and welded wire mesh was evaluated by a round determinate panel (RDP) test. However, performance assessment by using RDP specimens is hindered by the testing boundary condition and the failure pattern and mechanism of combined concrete layer and welded wire mesh remains unclear. In this paper, the numerical model of the RDP test was set up by means of a FEM code, ABAQUS, and a series of numerical tests were carried out to investigate the failure mechanism and the influence of boundary condition on the performance of the RDP tests. To ensure the constitutive model of concrete embedded in ABAQUS and the material parameters were correctly used, the numerical models were first calibrated by the laboratory results with different concrete panel thickness without using welded wire mesh. After that, the performance of the combined concrete layer and welded wire mesh was examined by using the calibrated concrete model and mesh model and the failure mechanism of the combined specimens was obtained. The results show that the failure pattern matches the laboratory observation rather well and the peak load carrying capacity of the combined concrete layer and welded wire mesh panel is a little higher than that of the concrete only panel but the residual load carrying capacity has been improved. The boundary condition has large effect on the load-displacement curve, which is discussed in detail in the paper. The objective was to develop a numerical methodology which could be used to evaluate the load carrying capacity of combined concrete layer and welded wire mesh and thereby improve the assessment of the performance of shotcrete and welded wire mesh on site.
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