Phase relations and crystal structure of τ6-Ti2(Ti(0.16)Ni(0.43)Al(0.41))3

Ti(2)(Ti(0.16)Ni(0.43)Al(0.41))(3) is a novel compound (labeled as τ(6)) in the Ti-rich region of the Ti-Ni-Al system in a limited temperature range 870 < T < 980 °C. The structure of τ(6)-Ti(2)(Ti,Ni,Al)(3) was solved from a combined analysis of X-ray single crystal and neutron powder diffracton data (space group C2/m, a = 1.85383(7) nm, b = 0.49970(2) nm, c = 0.81511(3) nm, and β = 99.597(3)°). τ(6)-Ti(2)(Ti,Ni,Al)(3) as a variant of the V(2)(Co(0.57)Si(0.43))(3)-type is a combination of slabs of the MgZn(2)-Laves type and slabs of the Zr(4)Al(3)-type forming a tetrahedrally close-packed Frank-Kasper structure with pentagon-triangle main layers. Titanium atoms occupy the vanadium sites, but Ti/Ni/Al atoms randomly share the (Co/Si) sites of V(2)(Co(0.57)Si(0.43))(3). Although τ(6) shows a random replacement on 6 of the 11 atom sites, it has no significant homogeneity range (~1 at. %). The composition of τ(6) changes slightly with temperature. DSC/DTA runs (1 K/min) were not sufficient to define proper reaction temperatures due to slow reaction kinetics. Therefore, phase equilibria related to τ(6) were derived from X-ray powder diffraction in combination with EPMA on alloys, which were annealed at carefully set temperatures and quenched. τ(6) forms from a peritectoid reaction η-(Ti,Al)(2)Ni + τ(3) + α(2) ? τ(6) at 980 °C and decomposes in a eutectoid reaction τ(6) ? η + τ(4) + α(2) at 870 °C. Both reactions involve the η-(Ti,Al)(2)Ni phase, for which the atom distribution was derived from X-ray single crystal intensity data, revealing Ti/Al randomly sharing the 48f- and 16c-positions in space group Fd3?m (Ti(2)Ni-type, a = 1.12543(3) nm). There was no residual electron density at the octahedral centers of the crystal structure ruling out impurity stabilization. Phase equilibria involving the τ(6) phase have been established for various temperatures (T = 865, 900, 925, 950, 975 °C, and subsolidus). The reaction isotherms concerning the τ(6) phase have been established and are summarized in a Schultz-Scheil diagram.     

Inhomogeneous 2D linear intergrowth structures among novel Y–Cu–Mg ternary compounds with yttrium/copper equiatomic ratio

Single crystals of the Y₅Cu₅Mg₈, Y₅Cu₅Mg₁₃, Y₅Cu₅Mg₁₆ and YCuMg₄ compounds were synthesized by heating in a resistance furnace evacuated quartz vials containing Ta-crucibles with element pieces. SEM-EDXS analyses were performed to check phases composition. The structures were refined from X-ray single crystal diffraction data. Y₅Cu₅Mg₈, Y₅Cu₅Mg₁₃ and Y₅Cu₅Mg₁₆ represent new structure types: Y₅Cu₅Mg₈ – orthorhombic, Pmma, oP36, a = 2.63723(15), b = 0.40066(2), c = 0.74115(6) nm, Z = 2, wR₂ = 0.0597, 939 F² values, 60 variables; Y₅Cu₅Mg₁₃ – orthorhombic, Cmcm, oS92, a = 0.40973(2), b = 1.92794(8), c = 2.57907(11) nm, Z = 4, wR₂ = 0.1134, 1208 F² values, 75 variables; Y₅Cu₅Mg₁₆ – orthorhombic, Cmcm, oS104, a = 0.41360(8), b = 1.9239(4), c = 2.9086(6) nm, Z = 4, wR₂ = 0.0760, 1383 F² values, 84 variables. YCuMg₄ crystallizes in the TbCuMg₄ structure type (Cmmm, oS48, a = 1.35754(4), b = 2.03153(6), c = 0.39060(1) nm, Z = 8, wR₂ = 0.0401, 661 F² values, 45 variables). The crystal chemistry of these two-layer structures is comparatively discussed. Majority of novel compounds were characterized as members of inhomogeneous 2D intergrowth structure series of R₅M₅X₅, X₄ (Mg₄) and empty Mg octahedra building blocks of general formula R_5kM_5kX_{5k + 4l + m}. The common pentagonal prism derivative structural fragments around the most electropositive yttrium atoms were outlined in all these intermetallics.     

Thermal behavior for a nanoscale two ferromagnetic phase system based on random anisotropy model

Advances in theory that explain the magnetic behavior as function of temperature for two phase nanocrystalline soft magnetic materials are presented. The theory developed is based on the well known random anisotropy model, which includes the crystalline exchange stiffness and anisotropy energies in both amorphous and crystalline phases. The phenomenological behavior of the coercivity was obtained in the temperature range between the amorphous phase Curie temperature and the crystalline phase one.     

Preface – XXII Italian Congress on Calorimetry,Thermal Analysis and Chemical Thermodynamics

Journal of Thermal Analysis and Calorimetry -     

Phase equilibria in systems Ce-M-Sb (M=Si, Ge, Sn) and superstructure Ce12Ge9−xSb23+x (x=3.8±0.1)

Phase relations in the ternary systems Ce-M-Sb (M=Si, Ge, Sn) in composition regions CeSb₂-Sb-M were studied by optical and electron microscopy, X-ray diffraction, and electron probe microanalysis on arc-melted alloys and specimens annealed in the temperature region from 850 to 200 °C. The results, in combination with an assessment of all literature data available, were used to construct solidus surfaces and a series of isothermal sections. No ternary compounds were found to form in the Ce-Si-Sb system whilst Ce₁₂Ge_9−xSb_23+x (3.3<x<4.2) and CeSn_xSb₂ (0.1<x<0.8) participate in phase equilibria in the composition region investigated. Crystallographic parameters for the ternary compound Ce₁₂Ge_9−xSb_23+x (x=3.8±0.1) were determined from X-ray single crystal and powder diffraction. For the binary system Ge-Sb a eutectic was defined L⇔(Ge)+(Sb) at 591.6 °C and 22.5 at%. Ge EPMA revealed a maximal solubility of 6.3 at% Ge in (Sb) at the eutectic temperature.     

Alkylated Aromatic Thioethers with Aggregation‐Induced Emission Properties—Assembly and Photophysics

In this contribution, we present the synthesis and self‐assembly of alkylated thioethers with interesting photophysical properties. To this end, the emission, absorption and excitation spectra in organic solvents and as aggregates in water were measured as well as the corresponding photoluminescence quantum yields and lifetimes. The aggregates in aqueous media were visualized and measured using transmission electron microscopy. Besides that, crystal structures of selected compounds allowed a detailed discussion of the structure–property relationship. Furthermore, the mesomorphic behavior was investigated using polarized optical microscopy (POM) as well as differential scanning calorimetry (DSC).     

Synthesis and Pharmacological Screening of Pyridopyrimidines as Effective Anti-Diarrheal Agents through the Suppression of Cyclic Nucleotide Accumulation

The increased levels of cyclic nucleotides (cGMP and cAMP) in enterocytes trigger intracellular mechanisms of ion and fluid secretion into the lumen, causing secretory diarrhea. Twelve novel pyridopyrimidines derived from 5-(3,5-bistrifluoromethylphenyl)-1,3-dimethyl-5,11-dihydro-1H-indeno[2,1 : 5,6]pyrido[2,3-d]pyrimidine-2,4,6-trione (FPIPP) were synthesized and evaluated on intracellular cyclic nucleotide accumulation. All compounds had no effect on either cyclic nucleotide basal levels or on pre-contracted aortic rings. The metabolic activity and viability in T84 cells, assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) and the LDH (lactate dehydrogenase) assays, respectively, were not affected by incubation with the compounds (50 μM). Compound VI almost abolished cGMP accumulation (94 % inhibition) induced by STa toxin in T834 cells and significantly reduced (69 %) forskolin-induced cAMP accumulation in Jurkat cells. Compound VI was active in an in vivo model for diarrhea in rabbits. These results prompted us to perform a microscopic histopathological analysis of intestinal tissues, showing that only compound VI preserves the intestine without significant pathological changes and with a decreased inflammatory pattern in comparison to FPIPP. In vitro stability test revealed that compound VI is resistant to oxidation promoted by atmospheric oxygen.     

Phase equilibria of the Dy–Al–Si system at 500 °C

The isothermal section at 500 °C of the Dy–Al–Si system was studied in the whole concentration range. The alloys were characterized by X-ray powder diffraction, scanning electron microscopy and electron micro-probe analysis. A few samples were analysed by differential thermal analysis. The following intermetallic compounds, some of them showing variable composition, were found: DyAl₂Si₂ (τ₁), hP5-CaAl₂O₂ structure type, Dy₂Al₃Si₂ (τ₂) mS14-Y₂Al₃Si₂ structure type, Dy₂Al_1+x Si_2−x (τ₃), 0 ≤ x ≤ 0.25, oI10-W₂CoB₂ structure type and Dy₆Al₃Si (τ₄), tI80-Tb₆Al₃Si structure type. A number of binary phases dissolve the third element forming ternary solid solutions: Dy(Al_1−x Si _x )₃, 0 ≤ x ≤ 0.5, hP16-Ni₃Ti structure type, Dy(Al _x Si_1−x )₂, 0 ≤ x ≤ 0.1, oI12-GdSi₂ structure type, Dy(Al _x Si_1−x )_1.67, 0 ≤ x ≤ 0.2, oI12-GdSi₂ structure type, DyAl _x Si_1−x , 0 ≤ x ≤ 0.2, oC8-CrB, and Dy₅(Al _x Si_1−x )₃, 0 ≤ x ≤0.3, hP16-Mn₅Si₃ structure type. The melting point of Dy₆Al₃Si was determined.     

Crystal Structure Investigation of RE–Ni–Zn Ternary Compounds (RE = La,Ce, Tb)

The RENiZn (RE = La, Tb), RE₂Ni₂Zn (RE = La, Ce, Tb) and La₃Ni₃Zn ternary compounds were synthesized by two methods: by heating in a resistance furnace evacuated quartz ampoules containing Al₂O₃‐crucibles with element pieces and by induction melting in sealed Ta crucibles with subsequent annealing at 400 °C. Scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy (EDXS) was used for examining microstructure and phase composition of some of the alloys. The crystal structures for all the investigated phases were solved or confirmed on single crystal data by applying the direct methods refined by a standard least square procedure: LaNiZn – str. type ZrNiAl, hexagonal, , hP9, a = 0.7285(1), c = 0.3938(1) nm, wR₂ = 0.0534, 257 F² values, 14 variables; a = 0.7044(1), c = 0.3782(1) nm, wR₂ = 0.0447, 236 F² values, 14 variables for TbNiZn; La₂Ni₂Zn – str. type Pr₂Ni₂Al, orthorhombic, Immm, oI10, a = 0.4381(1), b = 0.5459(1) c = 0.8605(2) nm, wR₂ = 0.0824, 223 F² values, 13 variables; a = 0.4365(1), b = 0.5430(1) c = 0.8279(2) nm, wR₂ = 0.0635, 209 F² values, 13 variables for Ce₂Ni₂Zn; a = 0.4209(1), b = 0.5366(1) c = 0.8165 (1) nm, wR₂ = 0.0757, 200 F² values, 13 variables for Tb₂Ni₂Zn; La₃Ni₃Zn – str. type Y₃Co₃Ga, orthorhombic, Cmcm, oS28, a = 0.4276(1), b = 1.0310(2) c = 1.3636(3) nm, wR₂ = 0.0859, 579 F² values, 26 variables. The structural peculiarities of these compounds and their relations are discussed.