Reinvestigation and superstructure of La3.67[Fe(C2)3]

The lanthanum iron carbide La_3.67[Fe(C₂)₃] was prepared from the elements by argon arc-melting followed by annealing. The crystal structure of the ternary phase was reported previously (space group P6₃/m with a=878.7(2) pm, and c=535.1(1) pm) [A.M. Witte, W. Jeitschko, Z. Naturforsch. 51b (1996) 249-255]. In the present work the compound was reinvestigated by X-ray powder and single crystal diffraction, and was further characterized by metallographic methods and chemical analyses. Our diffraction data clearly reveal a superstructure with weak superstructure reflections in the space group P6₃/m with a=879.26(8) pm and c=1604.59(15) pm, thus tripling the previously reported subcell. The crystal structure (refinement to R1=0.044 and wR2=0.075 for 1387 unique reflections and 60 variables) contains Fe(C₂)₃ trigonal planar groups with the C₂ ligands bonded end-on to the Fe atoms. The C-C distance is typical for a double bond. La atoms as the least electronegative component surround the complex anions and form a framework of face-sharing tricapped trigonal prisms. The resulting hexagonal channels at 0, 0, z of the partial structure with chemical composition La₃FeC₆ are occupied by four additional La atoms per unit cell. These La atoms are fully ordered within a linear chain and display a Peierls-like distortion pattern. However, no long-range order in the a−b plane has been observed due to the random orientation of the chains. Because of the two different orientations which are possible for each chain the situation is similar to an Ising model on a triangular lattice.     

Effect of montmorillonite on structure and properties of nanocomposite with PA6/PS/elastomer matrix

Polyamide nanocomposites with fair balance of mechanical properties were recently obtained by addition of finely dispersed clay-compatibilized rubber or rigid PS phase. This work deals with combination of both components, which recently led also to enhanced mechanical behaviour in an analogous reactively compatibilized ternary system.Application of clay to PA6/PS/EPR matrix leads to a decrease in particle size analogously to corresponding binary blends, but the effect of clay on toughness is predominantly contradictory, i.e., a decrease with increasing clay content was found. Also the toughening effect of formed core-shell (elastomer/clay) particles is lower in comparison with binary PA6/EPR. At the same time, in contrast to the PA/PS system, the presence of core-shell particles formed by PS/C15 preblending leads to fair mechanical behaviour including enhanced toughness. This documents a complex affecting of the system behaviour by clay and the expected synergistic cooperation of numerous clay-induced changes in both component parameters and structure. The obtained results indicate that a proper combination of rigid and elastomeric inclusions can lead to nanocomposites with balanced and enhanced mechanical behaviour.     

Activity coefficients of NaCl in the NaCl + NaBF4 + H2O ternary system at 298.15 K

The activity coefficients of sodium chloride in the NaCl + NaBF₄ + H₂O ternary system were experimentally determined at 298.15 K, at ionic strengths of 0.3. 0.5, 1, 2 and 3 mol kg⁻¹ from emf from the bi-ISE cell without liquid junction:

ISE-Na|NaCl(m_A), NaBF₄(m_B)|ISE-Cl

Prediction of critical transitions of ternary mixtures containing ammonia and n-alkanes

The analysis of the critical transitions that occur in ternary mixtures is important to describe their physical behavior. It also enables the phase behavior of multi-component mixtures at high temperatures to be inferred. The objective of this work was to identify the critical transitions that occur in ternary mixtures containing ammonia and n  -alkane. The mixture’s critical loci were obtained and tested for stability using thermodynamic criteria expressed in terms of the Helmholtz free energy. Two equations of state were used to represent the Helmholtz free energy: the Carnahan–Starling–Redlich–Kwong (CSRK) and the Simplified Perturbed Hard Chain Theory (SPHCT). In order to identify the existing critical transitions, profiles of the critical loci were calculated along constant compositional ratios χ=x₁/x₂$\chi =x_1/x_2$. Some of the curves depict higher order critical transitions between liquid–liquid and gas–liquid critical point regions, or two different liquid–liquid critical regions. One of the critical transitions found could be considered as a new sub-class within existing classifications for ternary mixtures proposed by Sadus [R.J. Sadus, J. Phys. Chem. 96 (1992) 5197–5202].     

Antibiotics Separation with MXene Membranes Based on Regularly Stacked High‐Aspect‐Ratio Nanosheets

The uncontrolled release of antibiotics and pharmaceuticals into the environment is a worldwide increasing problem. Thus, highly efficient treatment technologies for wastewater are urgently needed. In this work, seven kinds of typical antibiotics (including water and alcohol soluble ones) are successfully separated from the corresponding aqueous and ethanolic solutions using highly regular laminated membranes. Our membranes are assembled with 2–4 μm titanium carbide nanosheets. The solvent permeance through such titanium carbide membrane is one order of magnitude higher than that through most polymeric nanofiltration membranes with similar antibiotics rejection. This high flux is due to the regular two‐dimensional (2D) structure resulting from the large aspect ratio of titanium carbide nanosheets. Moreover, the electrostatic interaction between the surface terminations and the antibiotics also affects the rejection and enhances the antifouling property. Such 2D titanium carbide membranes further broaden the application scope of laminated materials for separation and purification of high value added drugs in academia and industry.     

Chemical bonding analysis and properties of La7Os4C9—A new structure type containing C- and C2-units as Os-coordinating ligands

The new ternary carbide La₇Os₄C₉ was prepared by argon arc-melting of the elements followed by subsequent heat treatment at 900 °C for 250 h. The compound crystallizes monoclinic, in the space group C2/m (a=1198.5(2) pm, b=542.0(1) pm, c=1196.2(2) pm, β=111.04(1)°, V=725.2(2)×10⁶ pm³, Z=2). The structure was determined from single crystal X-ray diffraction data and refined to a residual of R₁=0.02 (wR₂=0.03) for 4812 unique reflections and 64 variable parameters. Electrical resistivity and magnetic susceptibility measurements characterize the compound as a Pauli-paramagnetic metal. The crystal structure contains bridging C- and terminal C₂-units as Os-coordinating ligands, thereby forming polyanions running along the [101] direction. The polyanions are composed of alternating Os(C₂)C₂ and OsC₃ units with the transition metal in distorted trigonal planar coordination. Charge compensation is ensured by La cations which are situated in-between the polyanions. The carbon-carbon bond (131 pm) within the C₂ pairs is slightly shorter than the value of a common C-C double bond, and is discussed on the basis of COHP curves on the one side, and with ELI-D and electron density distributions on the other side. The method of partial ELI-D decomposition is shown to be well suited for the characterization of separated DOS structures in terms of chemical bonding signatures provided by ELI-D. The Os-La interactions are shown to be of a polar multicenter-bonding type with Os playing the role of the electron donor. Compared to an acetylide the C₂ species were found to possess a significantly reduced bond order and an enhanced number of electrons in lone pair type spatial regions. This type of species cannot be simply classified in terms of model pictures such as C₂²⁻ and C₂⁴⁻, respectively.     

Dimensional reductions from 2-D Nb4P2S21 to 1-D ANb2PS10 (A=Na, K, Rb, Cs, Tl) and to 0-D Tl5[Nb2S4Cl8]Cl using halide molten salts

We found new synthetic routes to obtain 1-D quaternary thiophosphate compounds and a 0-D molecular complex containing a Nb₂S₄ core from a 2-D ternary thiophosphate, Nb₄P₂S₂₁. When Nb₄P₂S₂₁ was reacted with alkali metal halides (ACl; A=Na, K, Rb, Cs) or TlCl at 500-700 °C, the -S-S-S- bridges in 2-D Nb₂PS₁₀-S-S₁₀PNb₂ were excised to form a 1-D chain, and cations were inserted between the chains to form ANb₂PS₁₀ (A=Na, K, Rb, Cs, Tl). We also found that thallium chloride (TlCl) is an excellent reagent for further excision, and it substitutes chloride ligands for the sulfur ligands of 2-D Nb₄P₂S₂₁ to form the molecular complex Tl₅[Nb₂S₄Cl₈]Cl. Crystal data for TlNb₂PS₁₀: monoclinic, Pn, a=6.9452(11) Å, b=7.3761(12) Å, 12.873(2) Å, β=104.472(3)°, and Z=2. Crystal data for Tl₅[Nb₂S₄Cl₈]Cl: orthorhombic, Immm, a=7.001(5) Å, b=9.509(7) Å, c=15.546(11) Å, and Z=2.     

A refined physico-chemical model of solute retention in reversed-phase high-performance liquid chromatography with ternary mobile phases

Summary In our previous publication we have introduced a new model of solute retention in RP-HPLC systems with ternary mobile phases of the B+AB₁+AB₂ type (B: acetonitrile or tetrahydrofuran; AB₁: methanol; AB₂: water). That model proposed no stoichiometric differentiation between acetonitrile and tetrahydrofuran, alternatively present in the solvent system; moreover, it made some very rough assumptions only as to the intermolecular interactions among the mobile phase constituents.This paper introduces a significant refinement to the already established retention model, which is based on the simple quantitative relationships between acetonitrile and tetrahydrofuran, and the remaining components of the ternary liquid system. The refined model is tested with same experimental data.     

三元混配络合物形成的极谱研究——Cd-Bipy-Gly体系的稳定常数测定

用般谱法研究了Cd(Ⅱ)-2,2′-联吡啶(bipy)、Cd(Ⅱ)-甘氨酸(Gly)二元体系及cd(Ⅱ)-bipy-Gly三元体系的配合物的形成条件,用极谱法测定了不同浓庹配体的E_1/2(a)、E_1/2(c)、ΔE_1/2、(i_d)_s和(i_d)_c值,利用Lrden函数作图,外推求得各级稳定常数。