Modelling the Springback of Sheet Metals at Large Deformations

Sheet metal forming simulations are increasingly replacing traditional build-and-break prototyping because they provide a less expensive and more rapid way to speed up product design time while improving quality and performance. Sheet metal is subjected to stretching, bending and unbending during forming, and an accurate prediction of the formability and springback of the sheet necessitates the use of an appropriate constitutive model. Use of isotropic hardening alone has been identified as a source of inaccurate springback prediction. In order to be able to describe the cyclic hardening behaviour and the Bauschinger effect, a large-deformation elasto-plastic material model with non-linear kinematic hardening is discussed in the present work. The model is derived from a thermodynamical framework and is based on the multiplicative split of the deformation gradient. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hexakaliumhexaselenodistannat(III) K6Sn2Se6 – Synthese,Struktur und Eigenschaften einer neuen salzartigen SnIII-Verbindung

Hexapotassium Hexaselenodistannate(III) K₆Sn₂Se₆ – Synthesis, Structure, and Properties of a New Salt-like Sn^III Compound Reaction of stoichiometric amounts of potassium, tin, and selenium in sealed silica tubes yield at 900 °C K₆Sn₂Se₆ ( 1 ) as red-orange solid of which small particles are very suitable for X-ray structural analysis. Space group P2₁/c, lattice dimensions at 203 K: a = 905.6(2), b = 1277.4(3), c = 888.7(2) pm, β = 115.86(3)°, R₁ = 0.0332. Besides Cs₆Sn₂Se₆, 1 represents the second hexaselenostannate(III) to be known and structurally characterized. Thus, it contributes to the completion of the hexachalcogenostannate(III) family. Additionally, 1 is isostructural and in some cases even isotypic to homologue compounds of the elements silicon and germanium.     

Computational and Experimental Study of Turbo-Organomagnesium Amide Reagents: Cubane Aggregates as Reactive Intermediates in Pummerer Coupling

The dynamic equilibria of organomagnesium reagents are known to be very complex, and the relative reactivity of their components is poorly understood. Herein, a combination of DFT calculations and kinetic experiments is employed to investigate the detailed reaction mechanism of the Pummerer coupling between sulfoxides and turbo-organomagnesium amides. Among the various aggregates studied, unprecedented heterometallic open cubane structures are demonstrated to yield favorable barriers through a concerted anion-anion coupling/ S−O cleavage step. Beyond a structural curiosity, these results introduce open cubane organometallics as key reactive intermediates in turbo-organomagnesium amide mixtures.     

Block copolymer‐directed synthesis of porous anatase for lithium‐ion battery electrodes

A templating method is developed to produce porous nanocrystalline anatase materials for negative electrodes in lithium‐ion batteries (LIBs). Amphiphilic diblock copolymers are used to generate template films with phase‐separated internal structure. Subsequent swelling with acidified titanium(IV) bis(ammonium lactato) dihydroxide (TALH) solution yielded structured hybrid films. Upon heating, the formation of TiO₂ nanocrystals is induced, resulting in a three‐dimensional mesoporous structure directed by the bulk morphology of the polymer template. In comparison to commercial nanosized anatase, the structured anatase shows significant performance improvements in lithium‐ion coin cell batteries in terms of capacity, stability, and rate capability. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1890–1896     

GRGD‐decorated three‐dimensional nanoworm hydrogels for culturing human embryonic stem cells

Human embryonic stem cells (hESCs) offer great hope in the development of regenerative medicine. This article demonstrates a method to prepare temperature induced three‐dimensional (3D) hydrogels consisting of soft and flexible polymer nanoworms with a radius of 10 nm and lengths on the micrometer scale. We decorated the surface of the nanoworms with the integrin‐binding peptide (RGD) using our novel physical adsorption process, and show that the resulting gels are able to immobilize and maintain the survival of hESCs. We conclude that the unique PNIPAM nanoworm hydrogels allow binding of undifferentiated hESC through small integrin‐binding peptides. Their temperature sensitivity, biocompatibility, ability to present combinations of multiple ligands and moldability into any desired 3D shape should make this nanoworm system a versatile platform for organoid engineering and regenerative medicine in the future. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1956–1963     

[Am(C5Me4H)3]: An Organometallic Americium Complex

We report the small‐scale synthesis, isolated yield, single‐crystal X‐ray structure, ¹H NMR solution spectroscopy /solid‐state UV/Vis‐nIR spectroscopy, and density functional theory (DFT)/ab initio wave function theory calculations on an Am³⁺ organometallic complex, [Am(C₅Me₄H)₃] ( 1 ). This constitutes the first quantitative data on Am?C bonding in a molecular species.