Characterizing the oxygen-oxygen interaction in the dinitramide anion

Atomic interactions between oxygen atoms have been analyzed in terms of the Theory of Atoms in Molecules for the biguanidium dinitramide and biguanidium bis-dinitramide crystals. The electron density has been derived from X-ray diffraction data obtained at 90 K, and the potential energy density has been calculated using the density functional approach. Bond critical points have been found on the O(1)...O(4) interatomic line in both the electron density and potential energy density gradient fields. The bond path and its associated virial path have been obtained. The interaction has been identified as a bonding closed-shell type interaction.     

Structure Determination of a Twinned Rb(H2NC10H6SO3) · H2O Crystal and Comparison to Related Alkali Metal Aminonaphthalenesulfonates

Rb(H₂NC₁₀H₆SO₃) · H₂O crystallizes in space group P2₁ with two formula units in the asymmetric unit, the crystal being twinned by a 180° rotation about [1 0 0]. The structure was determined from X‐ray diffraction data, and refined, based on two twin components, to yield a final R value of 0.0557 for 2754 reflections. The structure consists of alternating layers of aminonaphthalenesulfonate and rubidium ions. There are two distinct rubidium environments, the metal ions linked by the sulfonate groups and bridging water molecules into an infinite sheet. The sulfonate groups are bidentate, monodentate and bridging, all oxygen atoms being bound to at least one metal. The amino groups do not participate in coordination to the metal. Aromatic moieties from neighboring hydrophilic metallo‐layers interleave to form the hydrophobic layers. There is some similarity to the analogous sodium and potassium structures, however the rubidium compound is distinguished by an infinite cationic layer, rather than columns observed for the other two structures.     

catena‐Poly­[[di­aqua­di­chloro­iron(II)]‐μ‐1,4‐dioxane‐κ2O:O′]

The crystal structure of the title compound, [FeCl₂(C₄H₈O₂)(H₂O)₂]_n, contains six‐coordinate Fe^II atoms in approximately octahedral environments. The Fe^II atoms have symmetry, i.e. all pairs of identical ligands are trans. The structure consists of polymeric chains made up of dioxane mol­ecules, in the chair conformation with symmetry, linking the Fe^II centers. The chains are crosslinked by O—H?Cl hydrogen bonds.     

Combining wire and coaxial powder feeding in laser direct metal deposition for rapid prototyping

Powder and wire deposition have been used separately in many laser-cladding, rapid prototyping and other additive manufacturing applications. In this paper, a new approach is investigated by simultaneously feeding powder from a coaxial nozzle and wire from an off-axis nozzle into the deposition melt pool. Multilayer parts are built from 316L steel using a 1.5 kW diode laser and different configurations of the powder and wire nozzles are compared in terms of surface roughness, deposition rate, porosity and microstructure. The parts are analysed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical microscopy techniques. Results show that deposition efficiency increased and surface roughness decreased with the combined process; some porosity was present in samples produced by this method, but it was 20-30% less than in samples produced by powder alone. Wire injection angles into the melt pool in both horizontal and vertical planes were found to be significant for attaining high deposition efficiency and good surface quality. Reasons for the final sample characteristics and differences between the combined process and the separate powder and wire feeding techniques are discussed.     

Hydrogen release from mixtures of lithium borohydride and lithium amide: a phase diagram study

We recently reported the synthesis of a new quaternary hydride in the lithium-boron-nitrogen-hydrogen quaternary phase diagram with the approximate composition LiB0.33N0.67H2.67 having a theoretical hydrogen content of 11.9 wt %. This new compound forms by the reaction of appropriate amounts of lithium amide (LiNH2) and lithium borohydride (LiBH4) and releases greater than 10 wt % hydrogen when heated. A small amount of ammonia, 2-3 mol % of the generated gas, is also released. We now report a study of hydrogen and ammonia release from the series of reactant mixtures (LiNH2)x(LiBH4)1-x, where x=0.667 corresponds to the composition LiB0.33N0.67H2.67. We measured hydrogen and ammonia release amounts as a function of composition and found that maximum hydrogen and minimum ammonia release do occur for x=0.667. We also present evidence for an additional new quaternary phase and for two possibly metastable phases in this system.     

Intermolecular [2+2] photocyclization of ethyl 5-oxo-1a,2,5,5a,6,6a-hexahydro-2,6-methano-2aH-indeno-[5,6-b]oxirene-2a-carboxylate

The photodimer, 7, of ethyl 5-oxo-1a,2,5,5a,6,6a-hexahydro-2,6-methano-2aH-indeno-[5,6-b]oxirene-2a-carboxylate has been isolated and structuraally characterized. Triclinic,P ^?1,a=9.7783(6),b=11.2782(7),c=11.3445(7) Å, α=105.461(9), β=113.3759(10), γ=92.9155(11)^o,V=1089.36(12) ų,R=0.049 for 3557 unique observed reflections. Two independent molecules lying on inversion centers occupy the unit cell. The influence of the orientation of the ester group on the polycyclic skeleton is discussed.     

Photo-stabilisation of polyethylene by graft co-polymerisation

The effectiveness of graft co-polymerising a polymerisable ultraviolet absorber, 2-hydroxy-4-(3-methacryloxy-2-hydroxypropoxy) benzophenone, to low density polyethylene has been compared with stabilisation by the addition of a low molecular weight absorber, 2-hydroxy-4-n-octoxybenzophenone. The grafting reaction was performed using a mutual gamma radiation technique in the presence of cupric chloride to inhibit homopolymerisation. Although, in this instance, the additive proved more effective, the possible advantages of ultraviolet stabilisation by graft co-polymerisation are discussed.