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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.

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.

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.

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.

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.

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.

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.

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.

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.

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., AuthorCount:9

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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., AuthorCount:6

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., AuthorCount:11

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., AuthorCount:6;Funding agencies:National Natural Science Foundation of China; State Basic Research Project of China 2011CB808703; Swedish Research Council (VR); Swedish Governmental Agency for Innovation Systems (VINNOVA) through the Berzelii Center EXSELENT; NSERC Canada; CIHR; NRC; University of Saskatchewan

A stereochemical divergent approach for the highly enantioselective synthesis of distinct bicyclic products with multiple stereocenters from a racemate using a single chiral catalyst is disclosed. It is based on switches of the overall reaction pathways in the chiral amine-catalyzed cascade reactions between racemic ?-nitro ketones and a,beta-unsaturated aldehydes using different achiral co-catalysts. The utility of the method is exemplified by the highly diasteroselective switch and stereoconvergent deracemization process by combination of chiral amine and achiral hydrogen-bond-donating catalysts., AuthorCount:7

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., AuthorCount:5

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)., 7