| 1. |
- Liu, Leifeng, et al.
(författare)
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Self-supported yttria-stabilized zirconia mesocrystals with tunable mesopores prepared by a chemi-thermal process
- 2019
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Ingår i: Journal of Materiomics. - : Elsevier BV. - 2352-8478 .- 2352-8486. ; 5:3, s. 350-356
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Tidskriftsartikel (refereegranskat)abstract
- Mesoporous mesocrystals are highly desired in catalysis, energy storage, medical and many other applications, but most of synthesis strategies involve the usage of costly chemicals and complicated synthesis routes, which impede the commercialization of such materials. During the sintering of dense ceramics, coarsening is an undesirable phenomenon which causes the growth of the grains as well as the pores hence hinders the densification, however, coarsening is desired in the sintering of porous ceramics to expand the pore sizes while retaining the total pore volume. Here we report a chemi-thermal process, during which nanocrystallite aggregates were synthesized by hydrothermal process and then converted to the product by sintering. Through this strategy, we synthesized mesoporous self-supported mesocrystals of yttria-stabilized zirconia with tunable pore size and the process was then scaled-up to industrial production. The thermal conductivity measurement shows that the mesoporous powder is a good thermal isolator. The monolith pellets can be obtained by SPS sintering under high pressure and the mesoporosity is retained in the monolith pellets. This work features facile and scalable process as well as low cost raw chemicals making it highly desirable in industrial applications.
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| 2. |
- Li, Duan, et al.
(författare)
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Dense and strong ZrO2 ceramics fully densified in <15 min
- 2019
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Ingår i: Advances in Applied Ceramics. - : Informa UK Limited. - 1743-6753 .- 1743-6761. ; 118:1-2, s. 23-29
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Tidskriftsartikel (refereegranskat)abstract
- Crack-free zirconia ceramics were consolidated via sintering by intense thermal radiation (SITR) approach at 1600–1700°C for 3–5 min. The resulted ceramic bulks can achieve a relative density up to 99.6% with a grain size of 300–1200 nm. Their bending strength, Vickers hardness and indentation toughness values are up to 1244 ± 139 MPa, 13.3 ± 0.3 GPa and 5.5 ± 0.1 MPa m1/2, respectively. Quantitative Raman and XRD analysis show the presence of minor m phase on the natural surface (<7%), fracture surface (<10%) and indentation areas (<15%). It reveals that the SITR method is efficient for rapidly manufacturing zirconia ceramics with desired density, fine grained microstructure and good mechanical properties that are strongly demanded in dental applications.
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| 3. |
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| 4. |
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| 5. |
- Liu, Yihong, et al.
(författare)
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Self-glazed zirconia reducing the wear to tooth enamel
- 2016
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 36:12, s. 2889-2894
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Tidskriftsartikel (refereegranskat)abstract
- The wear behaviors of a newly developed grade of self-glazed zirconia against the enamel of freshly extracted teeth were investigated under simulated oral stresses and chemical environment. It was revealed that an inherently formed enamel-like surface on self-glazed zirconia that is very smooth on micrometer scale yet with nanoscale roughness has almost the same frictional coefficient against tooth enamel as the well-polished zirconia surface. The wear scars observed on the worn surface of enamel against self-glazed zirconia and well-polished zirconia surface revealed that in both cases fatigue wear is the dominating wear mechanism. It was concluded that the friction and wear performances of both the well-polished and self-glazed zirconia ceramics against natural enamel were very similar, which bears a very strong implication for the clinical safe use of the full contour zirconia restorations, yet the self-glazed zirconia provides sufficiently improved aesthetic appearance that ensures its potential for direct clinical uses.
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| 6. |
- Olsén, Jon, 1983-, et al.
(författare)
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Tailoring hierarchical structures in selective laser melted materials
- 2017
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Ingår i: IOP Conference Series. - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- With selective laser melting the potential to manufacture a wide variety of geometries from different materials has presented itself. Interest in this technology keeps growing every year, and with that growth a deeper understanding of the process and resulting materials is urgently needed. In this paper we present a short overview of the structural elements that appear during selective laser melting, and explain how to tailor them to achieve specific structures and material properties. Melt-pools, texture and grains, subgrain cells, and inclusions are the elements discussed herein, and tailoring of these elements can have effects on density, and corrosion resistance, as well as mechanical properties in general.
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| 7. |
- Shen, Zhijian, et al.
(författare)
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Fractography of self-glazed zirconia with improved reliability
- 2017
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 37:14, s. 4339-4345
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Tidskriftsartikel (refereegranskat)abstract
- The fractography of a new grade of zirconia ceramics, known as self-glazed zirconia, was investigated. The as-sintered intact top surface was made with superior smoothness that mimicked the optical appearances of the natural teeth enamel. The beneath surface opposite to this was made hierarchically rough with microscopic pits of the size up to 60. μm together with grain-level roughness of about 2. μm. The three-point bending test of the samples made with the hierarchically rough surface being tensile one demonstrated an average bending strength of 1120. ±. 70. MPa and a Weibull modulus of as high as 18 ascribed to the improved structural homogeneity. Surface topography was found the main origins of crack initiation leading to fracture. The observed unusually predominant transgranular fracture mode of submicron-sized grains disclosed a possible toughening mechanism of disassembling of mesocrystalline grains that differs significantly from the commonly quoted phase transformation toughening of this category of ceramics.
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| 8. |
- Yuan, Bo, et al.
(författare)
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Fabrication and microstructure of porous SiC ceramics with Al2O3 and CeO2 as sintering additives
- 2016
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 42:11, s. 12613-12616
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, porous silicon carbide ceramics were prepared via spark plasma sintering at relatively low temperatures using Al2O3 and CeO2 as sintering additives. Sacrificial template was selected as the pore forming mechanism, and gelcasting was used to fix the slurry in a short time. The evolution process of the microstructures during different steps was observed by SEM. The influence of the sintering temperature and sintering additives on the shrinkage and porosity of the samples was studied. The microstructures of different samples were characterized, and the mechanical properties were also evaluated.
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| 9. |
- Afewerki, Samson, et al.
(författare)
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Highly Enantioselective Control of Dynamic Cascade Transformations by Dual Catalysis : Asymmetric Synthesis of Polysubstituted Spirocyclic Oxindoles
- 2015
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 5:2, s. 1266-1272
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Tidskriftsartikel (refereegranskat)abstract
- The highly enantioselective (up to >99.5:0.5 er) synthesis of polysubstituted spirocyclic oxindoles with four new contiguous stereocenters, including the spiro all-carbon quaternary center, is disclosed. It is accomplished by the highly stereoselective control of a dynamic conjugate/intramolecular allylic alkylation relay sequence based on the synergistic cooperation of metal and chiral amine catalysts in which the careful selection of organic Nand, metal complex, and chiral amine is essential. The intermolecular C-C bond-forming step occurred only when both the metal and chiral amine catalysts were present.
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| 10. |
- Chen, Xiaozong, et al.
(författare)
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Preparation of nano-sized Bi2Te3 thermoelectric material powders by cryogenic grinding
- 2012
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Ingår i: Progress in Natural Science. - : Elsevier BV. - 1002-0071 .- 1745-5391. ; 22:3, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- A novel method for rapid preparation of Bi2Te3 nano-sized powders with an average particle size of about 7nm was developed. A starting powder mixture consisting of Bi2Te3 coarse particles of similar to 5mm was ground using cryogenic grinding in the liquid nitrogen. For comparison, the conventional high-energy ball milling was used to prepare the Bi2Te3 nano-sized powders. Sintering properties of as-prepared powders was investigated by spark plasma sintering (SPS). The effects of the preparation procedure on the crystallinity, morphology and structure were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that Bi2Te3 was not transformed into a non-equilibrium amorphous phase or decomposed during the cryogenic grinding process, and as-prepared nano-powders possessed excellent sinterability. This technique might also be applicable to other thermoelectric materials.
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| 11. |
- Fang, Liang, et al.
(författare)
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SU-77: An Open-Framework Germanate Containing 12 × 10 × 10-Ring Channels Solved by Combining Rotation Electron Diffraction and Powder X-ray Diffraction
- 2014
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 14:10, s. 5072-5078
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Tidskriftsartikel (refereegranskat)abstract
- A novel open-framework germanate, denoted as SU-77, was prepared by hydrothermal synthesis using ethylenediamine as the structure directing agent. The as-synthesized SU-77 is monoclinic with space group P21/a and a = 13.52427(5) Å, b = 12.64862(5) Å, c = 9.60578(3) Å, β = 92.8599(4)°. The structure of SU-77 is built from a novel Ge6O17(C2H8N2)F (Ge6) cluster building unit. The Ge6 clusters are connected to form chains along the c-axis. These chains are further connected in the [110] and [1–10] directions to form a three-dimensional framework with 12 × 10 × 10-ring channels. The as-synthesized monoclinic SU-77 became orthorhombic while being observed in a transmission electron microscope (TEM) or when heated to 200 °C in air. The orthorhombic structure of SU-77 was solved from micrometer-sized crystals by rotation electron diffraction (RED). The monoclinic structure was built from the orthorhombic structure and subsequently refined against synchrotron powder X-ray diffraction data. SU-77 is the first example of an open-framework germanate with mixed coordination polyhedra solved by electron diffraction.
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| 12. |
- Guo, Peng, et al.
(författare)
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A zeolite family with expanding structural complexity and embedded isoreticular structures
- 2015
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 524, s. 74-78
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Tidskriftsartikel (refereegranskat)abstract
- The prediction and synthesis of new crystal structures enable the targeted preparation of materials with desired properties. Among porous solids, this has been achieved for metal-organic frameworks(1-3), but not for the more widely applicable zeolites(4,5), where new materials are usually discovered using exploratory synthesis. Although millions of hypothetical zeolite structures have been proposed(6,7), not enough is known about their synthesis mechanism to allow any given structure to be prepared. Here we present an approach that combines structure solution with structure prediction, and inspires the targeted synthesis of new super-complex zeolites. We used electron diffraction to identify a family of related structures and to discover the structural 'coding' within them. This allowed us to determine the complex, and previously unknown, structure of zeolite ZSM-25 (ref. 8), which has the largest unit-cell volume of all known zeolites (91,554 cubic angstroms) and demonstrates selective CO2 adsorption. By extending our method, we were able to predict other members of a family of increasingly complex, but structurally related, zeolites and to synthesize two more-complex zeolites in the family, PST-20 and PST-25, with much larger cell volumes (166,988 and 275,178 cubic angstroms, respectively) and similar selective adsorption properties. Members of this family have the same symmetry, but an expanding unit cell, and are related by hitherto unrecognized structural principles; we call these family members embedded isoreticular zeolite structures.
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| 13. |
- Guo, Peng, et al.
(författare)
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Ab initio structure determination of interlayer expanded zeolites by single crystal rotation electron diffraction
- 2014
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 43:27, s. 10593-10601
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Tidskriftsartikel (refereegranskat)abstract
- Layered solids often form thin plate-like crystals that are too small to be studied by single-crystal X-ray diffraction. Although powder X-ray diffraction (PXRD) is the conventional method for studying such solids, it has limitations because of peak broadening and peak overlapping. We have recently developed a software-based rotation electron diffraction (RED) method for automated collection and processing of 3D electron diffraction data. Here we demonstrate the ab initio structure determination of two interlayer expanded zeolites, the microporous silicates COE-3 and COE-4 (COE-n stands for International Network of Centers of Excellence-n), from submicron-sized crystals by the RED method. COE-3 and COE-4 are built of ferrierite-type layers pillared by (-O-Si(CH3)(2)-O-) and (-O-Si(OH)(2)-O-) linker groups, respectively. The structures contain 2D intersecting 10-ring channels running parallel to the ferrierite layers. Because both COE-3 and COE-4 are electron-beam sensitive, a combination of RED datasets from 2 to 3 different crystals was needed for the structure solution and subsequent structure refinement. The structures were further refined by Rietveld refinement against the PXRD data. The structure models obtained from RED and PXRD were compared.
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| 14. |
- Jiang, Yan, et al.
(författare)
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Highly Diastereo- and Enantioselective Cascade Synthesis of Bicyclic Lactams in One-Pot
- 2018
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :9, s. 1158-1164
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Tidskriftsartikel (refereegranskat)abstract
- A versatile and highly stereoselective synthetic route to functionalized bi- and tricyclic lactams (up to > 20:1 dr and 99% ee) in one pot from simple starting materials (allylic alcohols, enals, diamines and amino alcohols) using cascade transformations promoted by chiral amine/BrOnsted or metal/chiral amine/BrOnsted relay catalysis is disclosed. Here molecular oxygen is employed as the terminal oxidant for the latter relay catalysis approach.
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| 15. |
- 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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| 16. |
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| 17. |
- Lin, Junzhong, et al.
(författare)
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Synthesis of hierarchical MCM-22 zeolite via a swelling and pillaring approach
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Zeolites are type of microporous crystalline material which have been widely used in various aspects of industry, such as separation, adsorption, and catalysis. However, great diffusion limitation can be provoked due to small pore size of mircoporus framework in catalytic reactions. Hierarchical zeolites have been proved to be a successful alternative to solve the diffusion problem. Particularly, the synthesis of hierarchical porous zeolite by swelling and pillaring lamellar MWW zeolitic precursor has been proved as an efficient approach to solve the diffusion limitations in the catalytic reactions. In this work, hierarchical MWW zeolite has been synthesized by swelling and pillaring of lamellar MWW zeolitic precursor (MCM-22) using D4R building units. The synthesis procedure has been carefully studied by various characterization methods, such as PXRD, TEM, N2 adsorption-desorption and etc.
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| 18. |
- Lin, Junzhong, et al.
(författare)
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Titanium incorporated hierarchical porous silicate synthesized using D4R as building blocks
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Hierarchical porous materials as catalyst have provoked great attention recent years considering that it can offer enhanced molecular diffusion and mass transfer during the reaction. Titanium containing hierarchical porous silicate material has been successfully synthesized in present work. Double-four-ring units were used as the basic building blocks to construct the desired material. Both micropores and mesopores were found in the as synthesized material. The local structure of incorporated titanium species was carefully studied using various characterization techniques, such as XPS, UV-vis, XANES and EXAFS. Tetrahedral coordinated titanium can be mostly found in the as synthesized material in this work, the distorted the local structure was further revealed by using EXAFS.
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| 19. |
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| 20. |
- Liu, Leifeng, et al.
(författare)
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Dislocation network in additive manufactured steel breaks strength-ductility trade-off
- 2018
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Ingår i: Materials Today. - : Elsevier BV. - 1369-7021 .- 1873-4103. ; 21:4, s. 354-361
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Tidskriftsartikel (refereegranskat)abstract
- Most mechanisms used for strengthening crystalline materials, e.g. introducing crystalline interfaces, lead to the reduction of ductility. An additive manufacturing process - selective laser melting breaks this trade-off by introducing dislocation network, which produces a stainless steel with both significantly enhanced strength and ductility. Systematic electron microscopy characterization reveals that the pre-existing dislocation network, which maintains its configuration during the entire plastic deformation, is an ideal modulator that is able to slow down but not entirely block the dislocation motion. It also promotes the formation of a high density of nano-twins during plastic deformation. This finding paves the way for developing high performance metals by tailoring the microstructure through additive manufacturing processes.
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| 21. |
- Liu, Leifeng, et al.
(författare)
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Disorder in Extra-Large Pore Zeolite ITQ-33 Revealed by Single Crystal XRD
- 2013
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 13:10, s. 4168-4171
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Tidskriftsartikel (refereegranskat)abstract
- The single crystal of the extra-large pore zeolite, ITQ-33, was obtained and used to explore its crystal structure details. The ITQ-33 structure was found to be disordered with the columnar periodic building unit, explaining the morphology changes upon the different Si/Ge ratio, and the formation of the hierarchical structure from assembling of ITQ-33 nanofibers.
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| 22. |
- Liu, Leifeng, 1986-
(författare)
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Inorganic and Metal-Organic Framework Materials : Synthesis and structure characterization
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inorganic and metal-organic framework materials possessing accessible and permanent pores are receiving tremendous attention. Among them, zeolites are the most famous class due to their wide applications on petrochemistry and gas separation. Besides zeolites, the other oxide framework materials are also intensively investigated because of their diverse structures and compositions. Metal-organic frameworks are built from metal clusters and organic linkers. By rational designing the reagent, the network with desired topology and functionality can be synthesized.For all of the framework materials mentioned above, to explore novel framework structures is important for improving properties and discovering new applications. This thesis includes the synthesis of zeolites and structure characterization for various types of inorganic framework materials. The zeolite synthesis conditions was exploited. With the optimized condition, the zeolite ITQ-33 was synthesized as single crystals. From the single crystal X-ray diffraction data, the disorder in the structure is discovered and explained. Following the topic of disorder and twinning, we proposed a novel method of solving structure of pseudo-merohedric twinning crystal by using an example of a metal-organic complex crystal. Then we also showed methods for solving structures of high complexity and nano-crystal by using mainly powder X-ray diffraction and transmission electron microscopy. Four examples were shown in chapter 4 including open-framework germanates and metal-organic frameworks.
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| 23. |
- Liu, Leifeng, et al.
(författare)
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Structure determination of [3Fe2S] complex with complicated pseudo-merohedric twinning
- 2012
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Ingår i: Zeitschrift fur Kristallographie. - : Walter de Gruyter GmbH. - 0044-2968. ; 227:4, s. 221-226
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Tidskriftsartikel (refereegranskat)abstract
- A route of solving crystal structures from complicated pseudo-merohedric twinning crystals was described. The structure of a [3Fe2S] complex was solved and refined in the space group of P42/n to R1 factor of 0.1789. Consequently, by deleting one of the two disordered groups in the structure, a space group of Aea2 for the absolute structure was found. The new absolute structure with four twinning components was refined to R1 about 0.1171. At the final stage, the disorder was again added to the structure. The structure in space group Aea2 with both twinning and disorder was refined to R1 of 0.0722, which implies the special structure feature.
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| 24. |
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| 25. |
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| 26. |
- Olsén, Jon, et al.
(författare)
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Micro- and macro-structural heterogeneities in 316L stainless steel prepared by electron-beam melting
- 2018
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Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 141, s. 1-7
-
Tidskriftsartikel (refereegranskat)abstract
- This is a study of the micro- and macrostructural variations in samples of stainless steel with the overall composition of the grade 316L, produced using electron beam melting. Electron beam melting is one of the processing methods under consideration for manufacturing some of the International Thermo- Nuclear Experimental Reactor In-Vessel components. Therefore further studies of the homogeneity of the material were conducted. Electron beam melting results in a complicated thermal history of the manufactured part giving a significant impact on the microstructure. A cellular structure that is often observed in samples prepared by selective laser melting was found in the top layers of the specimens. Further down, the structure changed until the cellular structure was almost non-existing, and the grain boundaries had become more pronounced. This revelation of a heterogeneous structure throughout the entire part is crucial for large-scale industrial applications like the Thermo- Nuclear Experimental Reactor to make sure that it is understood that the properties of the material might not be the same at every point, as well as to assure that the correct post-treatment is done. It is also exposed that a significant part of this change is due to molybdenum redistribution inside the sample when it diffuses from the cell boundaries into the cells, and into bigger agglomerates in the grain boundaries. This diffusion seems not to affect the microhardness of the samples.
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| 27. |
- Su, Jie, et al.
(författare)
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Structure analysis of zeolites by rotation electron diffraction (RED)
- 2014
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 189, s. 115-125
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Tidskriftsartikel (refereegranskat)abstract
- Single crystal X-ray diffraction and powder X-ray diffraction (PXRD) are powerful methods for determination of unknown crystal structures including zeolites. However, these techniques have some limitations. For instance, single crystal X-ray diffraction requires large enough crystals which are often difficult to synthesize. For powder X-ray diffraction, peak indexing and intensity extraction become difficult if there exist peak broadening caused by small crystal sizes and peak overlap due to large unit cell and high symmetry. This becomes even more complicated for samples that contain more than one phase. We developed a new rotation electron diffraction (RED) method that can overcome these limitations. Almost complete three-dimensional electron diffraction datasets can be collected from micron- or nano-sized single crystals in a transmission electron microscope by combining electron beam tilt and goniometer tilt. Here, we demonstrate the power and limitations of the RED method for ab initio structure determination of four sub-micron sized zeolites, including a calcined silicalite-1, an EUO-type germanosilicate, an FER-type aluminogermanosilicate and an AST-type aluminogermanosilicate. The latter three zeolites were found in multiphasic samples. We show how the tilt range, tilt step and resolution affect the unit cell determination, structure solution and structure refinement. The EUO-, FER- and AST-type zeolites were found in two multiphasic samples in the Al-Ge-Si system, which were also characterized by PXRD and N-2 sorption.
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| 28. |
- Xu, Yan, et al.
(författare)
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Germanate with Three-Dimensional 12 x 12 x 11-Ring Channels Solved by X-ray Powder Diffraction with Charge-Flipping Algorithm
- 2013
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 52:18, s. 10238-10244
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Tidskriftsartikel (refereegranskat)abstract
- A new open-framework germanate, denoted as GeO-JU90, was prepared by the hydrothermal synthesis method using 1,5-bis(methylpyrrolidinium)pentane dihydroxide as the organic structure-directing agent (SDA). The structure of GeO-JU90 was determined from synchrotron X-ray powder diffraction (XRPD) data using the charge-flipping algorithm. It revealed a complicated framework structure containing 11 Ge atoms in the asymmetric unit. The framework is built of 7-connected Ge-7 clusters and additional tetrahedral GeO3(OH) units forming a new three-dimensional interrupted framework with interesting 12 X 12 X 11-ring intersecting channels. The Ge K-edge extended X-ray absorption fine structure (EXAFS) analysis was performed to provide the local structural information around Ge atoms, giving rise to a first-shell contribution from about 4.2(2) O atoms at the average distance of 1.750(8) angstrom. The guest species subsequently determined by the simulated annealing method from XRPD data combining with other characterization techniques, e.g., C-13 NMR spectroscopy, infrared spectroscopy (FTIR), compositional analyses, and thermogravimetric analysis (TGA). Crystallographic data vertical bar(C15N2H32)(NH4)vertical bar[Ge11O21.5(OH)(4)], orthorhombic Ama2 (No. 40), a = 37.82959 angstrom, b = 15.24373 angstrom, c = 12.83659 angstrom, and Z = 8.
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| 29. |
- Yang, Sihai, et al.
(författare)
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Irreversible Network Transformation in a Dynamic Porous Host Catalyzed by Sulfur Dioxide
- 2013
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 135:13, s. 4954-4957
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Tidskriftsartikel (refereegranskat)abstract
- Porous NOTT-202a shows exceptionally high uptake of SO2, 13.6 mmol g(-1) (87.0 wt %) at 268 K and 1.0 bar, representing the highest value reported to date for a framework material. NOTT-202a undergoes a distinct irreversible framework phase transition upon SO2 uptake at 268-283 K to give NOTT-202b which has enhanced stability due to the formation of strong pi...pi interactions between interpenetrated networks.
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| 30. |
- Yao, Qingxia, et al.
(författare)
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Highly porous isoreticular lanthanide metal-organic frameworks
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- As an emerging type of porous materials, metal–organic frameworks (MOFs) have the advantages over conventional inorganic porous materials in that their structures and functions are systematically and predictably designable. Isoreticular expansion is an efficient way for systematic design and control of pore size and shape for MOFs. By using our proposed strategy, a series of highly porous isoreticular lanthanide-based metal-organic frameworks with systematic pore apertures has been obtained, which afford an isoreticular series of MIL-103 structures (termed SUMOF-7I to IV) with pore apertures ranging from 7.2 Å to 23 Å. These materials demonstrated exhibit robust architectures with permanent porosity, and exceptional thermal stability and chemical stability in various solvents. The combination of luminescence property and significant porosity of these MOFs enable them as a potential platform for multifunctional purpose.
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| 31. |
- Yao, Qingxia, et al.
(författare)
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Series of Highly Stable Isoreticular Lanthanide Metal-Organic Frameworks with Expanding Pore Size and Tunable Luminescent Properties
- 2015
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 27:15, s. 5332-5339
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Tidskriftsartikel (refereegranskat)abstract
- A series of highly porous isoreticular lanthanide-based metal organic frameworks (LnMOFs) denoted as SUMOE-7I to SUMOE-7IV (SU = Stockholm University; Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) have been synthesized using tritopic carboxylates as the organic linkers. The SUMOF-7 materials display one-dimensional pseudohexagonal channels with the pore diameter gradually enlarged from 8.4 to 23.9 angstrom, as a result of increasing sizes of the organic linkers. The structures have been solved by single crystal X-ray diffraction or rotation electron diffraction (RED) combined with powder X-ray diffraction (PXRD). The SUMOF-7 materials exhibit robust architectures with permanent porosity. More importantly, they exhibit exceptionally high thermal and chemical stability. We show that, by inclusion of organic dye molecules, the luminescence properties of the MOFs can be elaborated and modulated, leading to promising applications in sensing and optics.
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| 32. |
- Zhao, Jiao, et al.
(författare)
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Metal-Oxide Nanoparticles with Desired Morphology Inherited from Coordination-Polymer Precursors
- 2012
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 18:11, s. 3163-3168
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Tidskriftsartikel (refereegranskat)abstract
- The “escape-by-crafty-scheme” strategy is an efficient approach to prepare metal-oxide nanomaterials with desirable morphology and crystal planes inherited from coordination-polymer nanoparticle precursors, which can be designed and finely tuned by soft chemical assembly of metal ions and organic ligands at the molecular level (see scheme; ptcda=perylene-3,4,9,10-tetracarboxylic dianhydride).
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| 33. |
- Zheng, Haoquan, et al.
(författare)
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One-pot Synthesis of Metal Organic Frameworks with Encapsulated Target Molecules and Their Applications for Controlled Drug Delivery
- 2016
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 138:3, s. 962-968
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Tidskriftsartikel (refereegranskat)abstract
- Many medical and chemical applications require target molecules to be delivered in a controlled manner at precise locations. Metal-organic frameworks (MOFs) have high porosity, large surface area, and tunable functionality and are promising carriers for such purposes. Current approaches for incorporating target molecules are based on multistep postfunctionalization. Here, we report a novel approach that combines MOF synthesis and molecule encapsulation in a one-pot process. We demonstrate that large drug and dye molecules can be encapsulated in zeolitic imidazolate framework (ZIF) crystals. The molecules are homogeneously distributed within the crystals, and their loadings can be tuned. We show that ZIF-8 crystals loaded with the anticancer drug doxorubicin (DOX) are efficient drug delivery vehicles in cancer therapy using pH-responsive release. Their efficacy on breast cancer cell lines is higher than that of free DOX. Our one-pot process opens new possibilities to construct multifunctional delivery systems for a wide range of applications.
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| 34. |
- Zhong, Yuan, 1988-, et al.
(författare)
-
Additive manufacturing of 316L stainless steel by electron beam melting for nuclear fusion applications
- 2017
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 486, s. 234-245
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Tidskriftsartikel (refereegranskat)abstract
- A feasibility study was performed to fabricate ITER In-Vessel components by one of the metal additivemanufacturing methods, Electron Beam Melting®(EBM®). Solid specimens of SS316L with 99.8% relativedensity were prepared from gas atomized precursor powder granules. After the EBM®process the phaseremains as austenite and the composition has practically not been changed. The RCC-MR code used fornuclear pressure vessels provides guidelines for this study and tensile tests and Charpy-V tests werecarried out at 22C (RT) and 250C (ET). This work provides thefirst set of mechanical and micro-structure data of EBM®SS316L for nuclear fusion applications. The mechanical testing shows that theyield strength, ductility and toughness are well above the acceptance criteria and only the ultimatetensile strength of EBM®SS316L is below the RCC-MR code. Microstructure characterizations reveal thepresence of hierarchical structures consisting of solidified melt pools, columnar grains and irregularshaped sub-grains. Lots of precipitates enriched in Cr and Mo are observed at columnar grain boundarieswhile no sign of element segregation is shown at the sub-grain boundaries. Such a unique microstructureforms during a non-equilibrium process, comprising rapid solidification and a gradient‘annealing’process due to anisotropic thermalflow of accumulated heat inside the powder granule matrix. Relationsbetween process parameters, specimen geometry (total building time) and sub-grain structure are dis-cussed. Defects are formed mainly due to the large layer thickness (100mmÞwhich generates insufficientbonding between a few of the adjacently formed melt pools during the process. Further studies shouldfocus on adjusting layer thickness to improve the strength of EBM®SS316L and optimizing total buildingtime.
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| 35. |
- Zhong, Yuan, et al.
(författare)
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Additive manufacturing of ITER first wall panel parts by two approaches : Selective laser melting and electron beam melting
- 2017
-
Ingår i: Fusion engineering and design. - : Elsevier BV. - 0920-3796 .- 1873-7196. ; 116, s. 24-33
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Tidskriftsartikel (refereegranskat)abstract
- Fabrication of ITER First Wall (FW) Panel parts by two additive manufacturing (AM) technologies, selective laser melting (SEM) and electron beam melting (EBM), was supported by Fusion for Energy (F4E). For the first time, AM is applied to manufacture ITER In-Vessel parts with complex design. Fully dense SS316L was prepared by both SLM and EBM after developing optimized laser/electron beam parameters. Characterizations on the density, magnetic permeability, microstructure, defects and inclusions were carried out. Tensile properties, Charpy-impact properties and fatigue properties of SLM and EBM SS316L were also compared. ITER FW Panel parts were successfully fabricated by both SLM and EBM in a onestep building process. The SLM part has smoother surface, better size accuracy while the EBM part takes much less time to build. Issues with removing support structures might be solved by slightly changing the design of the internal cooling system. Further investigation of the influence of neutron irradiation on materials properties between the two AM technologies is needed.
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| 36. |
- Zhong, Yuan, et al.
(författare)
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Intragranular cellular segregation network structure strengthening 316L stainless steel prepared by selective laser melting
- 2016
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 470, s. 170-178
-
Tidskriftsartikel (refereegranskat)abstract
- A feasibility study was performed to fabricate ITER In-Vessel components by Selective Laser Melting (SLM) supported by Fusion for Energy (F4E). Almost fully dense 316L stainless steel (SS316L) components were prepared from gas-atomized powder and with optimized SLM processing parameters. Tensile tests and Charpy-V tests were carried out at 22 degrees C and 250 degrees C and the results showed that SLM SS316L fulfill the RCC-MR code. Microstructure characterization reveals the presence of hierarchical macro-, micro- and nano-structures in as-built samples that were very different from SS316L microstructures prepared by other established methods. The formation of a characteristic intragranular cellular segregation network microstructure appears to contribute to the increase of yield strength without losing ductility. Silicon oxide nano-inclusions were formed during the SLM process that generated a micro-hardness fluctuation in the building direction. The combined influence of a cellular microstructure and the nano-inclusions constraints the size of ductile dimples to nano-scale. The crack propagation is hindered by a pinning effect that improves the defect-tolerance of the SLM SS316L. This work proves that it was possible to manufacture SS316L with properties suitable for ITER First Wall panels. Further studies on irradiation properties of SLM SS316L and manufacturing of larger real-size components are needed.
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| 37. |
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| 38. |
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| 39. |
- Zhong, Yuan, et al.
(författare)
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Oxide dispersion strengthened stainless steel 316L with superior strength and ductility by selective laser melting
- 2020
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Ingår i: Journal of Materials Science & Technology. - : Elsevier BV. - 1005-0302. ; 42, s. 97-105
-
Tidskriftsartikel (refereegranskat)abstract
- Dense oxide dispersion strengthened (ODS) 316 L steels with different amount of Y2O3 additions were successfully fabricated by selective laser melting (SLM) even though part of the added Y2O3 got lost during the process. The microstructure was characterized in details and the mechanical properties were tested at room temperature, 250 degrees C and 400 degrees C, respectively. The effect of the scanning speed on agglomeration of nanoparticles during SLM process was discussed. Superior properties, e.g., yield strength of 574 MPa and elongation of 91%, were achieved at room temperature in SLM ODS 316 L with additional 1% of Y2O3. At elevated temperatures, the strength kept high but the elongations dropped dramatically. It was observed that nano-voids nucleated throughout the whole gauge section at the sites where nanoinclusions located. The growth and coalescence of these voids were suppressed by the formation of an element segregation network before necking, which relieved local stress concentration and thus delayed necking. This unusual necking behavior was studied and compared to the previous theory. It appeared that the strong convection presented in the melt pool can evenly redistribute the short-time milled coarse Y2O3 precursor powder during SLM process. These findings can not only solve the problems encountered during the fabrication of ODS components but also replenish the strengthening mechanism of SLM 316 L thus pave a way for further improving of mechanical properties.
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| 40. |
- Zou, Ji, et al.
(författare)
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Tougher zirconia nanoceramics with less yttria
- 2019
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Ingår i: Advances in Applied Ceramics. - : Informa UK Limited. - 1743-6753 .- 1743-6761. ; 118:1-2, s. 9-15
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Tidskriftsartikel (refereegranskat)abstract
- Reducing the grain size in zirconia ceramics has shown to decrease its toughness by size-dependent stabilisation of the tetragonal phase that, in turn, hinders the stress-induced phase transformation from tetragonal to monoclinic. The stability of the tetragonal phase increases with the decrease of grain size but decreases with the reduction of the amount of yttria added, implying the need for adjustment of the yttria content when a nano-grained structure is of concern. In this study, low-yttria compositions were investigated. The ceramics were prepared with two sintering methods namely spark plasma sintering (SPS) and pressureless sintering. A clear tendency was noted for the indentation toughness increase with the reduction of yttria content, and a higher toughness achieved in as-SPSed samples in comparison with the annealed samples. The origins of the increased toughness were discussed in terms of yttria content, carbon contamination and increased oxygen vacancies after sintering at reducing atmosphere in SPS.
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| 41. |
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