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Gas aspiration through ladle shroud, during the teeming of a ladle into a tundish, has been investigated via physical and mathematical modeling. To this end, a volume of fluid‐based two‐phase turbulent flow model (in conjunction with the standard k–ε turbulence model) and a full‐scale two‐strand bloom casting tundish have been applied. Both flow and residence time distribution measurements are carried out in the full‐scale tundish system, adopting well‐established measurement techniques. Computational results, supported appropriately with experimentally measured data, indicate that gas aspiration alters flow and turbulence profoundly in the vicinity of the shroud entry zone. Early reversal of jetting flow toward the free surface, due to the buoyancy of the entrained gas, increases the overall intensity of motion in the tundish, creating more mixing flow volumes at the expense of plug flow volume. Most importantly, however, gas aspiration through shroud tends to drastically cut down interactions between the down coming liquid jet metal and the pouring box, making the specific design and shape of a pouring box redundant toward desirable flow modification. Finally, it is shown that strong surface flows and turbulence, generated due to gas aspiration, can be suitably damped by deploying a set of weirs, increasing plug flow volume in tundish. [ABSTRACT FROM AUTHOR]

This study provides the first evidence that a Li ion can form ionic plastic crystals using crown ether with a bis-(trifluoromethanesulphonyl) amide (TFSA) anion. 1H, 7Li, and 13C nuclear-magnetic-resonance (NMR) measurements of the 15-crown-5–Li-TFSA complex revealed that the constituents underwent isotropic reorientation in the plastic crystalline phase. The NMR data of the 12-crown-4–Li-TFSA salt showed that the complex is a rotator crystal (the complexes are denoted as [Li 15C5] and [Li 12C4] in this paper). The X-ray diffraction (XRD) reflection patterns of the [Li 15C5] crystal recorded in the highest-temperature solid phase (plastic phase) could be indexed to a cubic structure. Conversely, [Li 12C4] could be fitted to a trigonal structure. In this study, [M (3n)Cn] (M = Li, Na, K; n = 4–6) complexes were also prepared, and NMR, DSC, XRD, and electrical conductivity measurements were performed. Based on these results, we additionally revealed that the [Na 15C5] and [K (15C5)2] complexes are also new rotator crystals. Single-crystal XRD measurements also revealed that the [Na 15C5] compound has two stable sites in the crystal. Activation energies of molecular motions in the [M (3n)Cn] crystals were estimated using 1H NMR relaxation time (T1 and T2) measurements. The electrical conductivity measurements of [Li 12C4], [Li 15C5], and [Na 15C5] showed high ionic conductivities (∼10−2 S cm−1). [ABSTRACT FROM AUTHOR]

This study provides the first evidence that a Li ion can form ionic plastic crystals using crown ether with a bis-(trifluoromethanesulphonyl) amide (TFSA) anion. 1 H, 7 Li, and 13 C nuclear-magnetic-resonance (NMR) measurements of the 15-crown-5-Li-TFSA complex revealed that the constituents underwent isotropic reorientation in the plastic crystalline phase. The NMR data of the 12-crown-4-Li-TFSA salt showed that the complex is a rotator crystal (the complexes are denoted as [Li 15C5] and [Li 12C4] in this paper). The X-ray diffraction (XRD) reflection patterns of the [Li 15C5] crystal recorded in the highest-temperature solid phase (plastic phase) could be indexed to a cubic structure. Conversely, [Li 12C4] could be fitted to a trigonal structure. In this study, [M (3 n )C n ] (M = Li, Na, K; n = 4-6) complexes were also prepared, and NMR, DSC, XRD, and electrical conductivity measurements were performed. Based on these results, we additionally revealed that the [Na 15C5] and [K (15C5) 2 ] complexes are also new rotator crystals. Single-crystal XRD measurements also revealed that the [Na 15C5] compound has two stable sites in the crystal. Activation energies of molecular motions in the [M (3 n )C n ] crystals were estimated using 1 H NMR relaxation time ( T 1 and T 2 ) measurements. The electrical conductivity measurements of [Li 12C4], [Li 15C5], and [Na 15C5] showed high ionic conductivities (∼10 -2 S cm -1 ).

The non-steroidal anti-inflammatory drugs mefenamic acid (MFA) and tolfenamic acid (TFA) have a close resemblance in their molecular scaffold, whereby a methyl group in MFA is substituted by a chloro group in TFA. The present study demonstrates the isomorphous nature of these compounds in a series of their multicomponent solids. Furthermore, the unique nature of MFA and TFA has been demonstrated while excavating their alternate solid forms in that, by varying the drug (MFA or TFA) to coformer [4-di-methyl-amino-pyridine (DMAP)] stoichiometric ratio, both drugs have produced three different types of multicomponent crystals, viz. salt (1:1; API to coformer ratio), salt hydrate (1:1:1) and cocrystal salt (2:1). Interestingly, as anticipated from the close similarity of TFA and MFA structures, these multicomponent solids have shown an isomorphous relation. A thorough characterization and structural investigation of the new multicomponent forms of MFA and TFA revealed their similarity in terms of space group and structural packing with isomorphic nature among the pairs. Herein, the experimental results are generalized in a broader perspective for predictably identifying any possible new forms of comparable compounds by mapping their crystal structure landscapes. The utility of such an approach is evident from the identification of polymorph VI of TFA from hetero-seeding with isomorphous MFA form I from acetone-methanol (1:1) solution. That aside, a pseudopolymorph of TFA with di-methyl-formamide (DMF) was obtained, which also has some structural similarity to that of the solvate MFA:DMF. These new isostructural pairs are discussed in the context of solid form screening using structural landscape similarity., (© Ranjan et al. 2020.)