ХАРАКТЕР ХИМИЧЕСКОЕ ВЗАИМОДЕЙСТВИЕ И СТЕКЛООБРАЗОВАНИЕ В СИСТЕМЕ AS2SE3-IN2TE3

Mетодами дифференциально-термического (ДТА), рентгенофазового (РФА), микроструктурного (МСА) анализа, а также измерения микротвердости и плотности, исследована система As2Se3-In2Te3 и построена Т - х фазовая диаграмма. Система As2Sе3-In2Te3 является квазибинарным сечением тройной взаимной системы As,In//Sе,Te. Cоединение In2As2Se3Te3 кристаллизуется в тетрагональной сингонии с параметрами решетки: а =9,40; с =6,36 Å, плотность ρпикн.=5,36 г/см3, ρрент.=5,85 г/см3. В системе образуется одно инконгруэнтное соединение In2As2Sе3Te3,плавящееся при 620оС. Выявлено, что в системе твердые растворы на основе In2Te3 доходят до 3 мол. %, а на основе As2Sе3 практически не обнаружены. В системе при медленном охлаждении область стеклообразования на основе As2Sе3 доходит до 7 мол. % In2Te3, а в режиме закалки в ледяной воде около 12 мол. % In2Te3. By the methods of differential thermal (DTA), X-ray phase (XRD), microstructural (MSA) analysis, as well as measurements of microhardness and density, the As2Se3-In2Te3 system was investigated and the T-x phase diagram was constructed. The As2Sе3-In2Te3 system is a quasi-binary section of the ternary reciprocal system As, In // Se, Te. One incongruent compound In2As2Sе3Te3 is formed in the system, melting at 620оС. Compound In2As2Sе3Te3 crystallizes in the tetragonal system with lattice parameters: a = 9.40; с = 6.36 Å, density ρpycn. = 5.36 g/cm3, ρX-rey. = 5.85 g/cm3. It was found that in the system, solid solutions based on In2Te3 reach 3 mol. %, and practically not found on the basis of As2Sе3. In the system, upon slow cooling, the glass formation region based on As2Se3 reaches 7 mol. % In2Te3, and in the mode of quenching in ice water about 12 mol. % In2Te3.

Cancellation of Auxetic Properties in F.C.C. Hard Sphere Crystals by Hybrid Layer-Channel Nanoinclusions Filled by Hard Spheres of Another Diameter

The elastic properties of f.c.c. hard sphere crystals with periodic arrays of nanoinclusions filled by hard spheres of another diameter are the subject of this paper. It has been shown that a simple modification of the model structure is sufficient to cause very significant changes in its elastic properties. The use of inclusions in the form of joined (mutually orthogonal) layers and channels showed that the resulting tetragonal system exhibited a complete lack of auxetic properties when the inclusion spheres reached sufficiently large diameter. Moreover, it was very surprising that this hybrid inclusion, which can completely eliminate auxeticity, was composed of components that, alone, in these conditions, enhanced the auxeticity either slightly (layer) or strongly (channel). The study was performed with computer simulations using the Monte Carlo method in the isothermal-isobaric (NpT) ensemble with a variable box shape.

Unique octahedral rotation pattern in the oxygen-deficient Ruddlesden–Popper compound Gd3Ba2Fe4O12

A novel Ruddlesden–Popper-related compound, Gd3Ba2Fe4O12, was discovered and its crystal structure was determined via single-crystal X-ray diffraction. The structure has an ordered structure of octahedra and pyramids along the c axis. Gd3Ba2Fe4O12 belongs to the tetragonal system P42/ncm, with a = 5.59040 (10) Å and c = 35.1899 (10) Å. The A-site ions in the Ruddlesden–Popper structure, i.e. Gd3+ and Ba2+, exhibit an ordering along the c axis. The perfect oxygen deficiency is accommodated at the GdO layers in the proper Ruddlesden–Popper structure. Using the bond-valence-sum method, the Fe ions in the FeO6 octahedra and FeO5 pyramids represent valence states of +3 and +2.5, respectively, demonstrating a two-dimensional charge disproportionation. The corner-sharing FeO6 octahedra and FeO5 pyramids are tilted in opposite directions, with the neighbours around one axis of the simple perovskite configuration, which, using Glazer's notation, can be represented as a − b 0 c 0/b 0 a − c 0. In the perovskite blocks, the facing FeO5 pyramids across the Gd layer rotate in the same sense, which is a unique rotation feature related to oxygen deficiency.

ХИМИЧЕСКОЕ ВЗАИМОДЕЙСТВИЕ И СТЕКЛООБРАЗОВАНИЕ В СИСТЕМЕ AS2SE3-NDSE

The nature of the interaction in the As2Se3-NdSe system was investigated by the methods of physicochemical (DTA, XRD, MSA, as well as by measuring the microhardness and determining the density), and the T-x phase diagram was constructed. In the As2Se3-NdSe system, one new ternary compound of the composition NdAs2Se4 is formed. It was found that this compound crystallizes in the tetragonal system with lattice parameters: a = 12.62; c = 7.42 Ǻ, Z = 7, ρpuc/. = 5.75.103 kg/cm3; ρrent = 5.99.103 kg/cm3. In the As2Se3-NdSe system based on the basis of As2Se3, solid solutions reach 1.5 mol % NdSe, and on the basis of NdSe - 2 mol % As2Se3. In the As2Se3-NdSe system based on As2Se3, glass-forming regions are found.

ФИЗИКО-ХИМИЧЕСКОЕ ИССЛЕДОВАНИЕ СИСТЕМЫ Bi2Te3-Ho2Тe3

The chemical interactions in the Bi2Te3-Ho2Te3 system are investigated by methods of physicochemical analysis (DTA, XRD, MSA, microhardness measurements and density determination), a state diagram is constructed. As a result, it was revealed that the system state diagram is a quasi-binary eutectic type. In the Bi2Te3Ho2Te3 system, in a 1: 1 ratio of components, one ternary compound of the HoBiTe3 composition, incongruently melting at 610°C, is formed. According to the results of X-ray phase analysis, it was found that the HoBiTe3 compound crystallizes in the tetragonal system with lattice parameters: a = 19.99; c = 13.82 Å, Z = 3, density ρpikn. = 7.30 g/cm3 ρrent. = 7.35 g/cm3.On the basis of the initial components, regions of solid solutions were found, which on the basis of Bi2Te3 reach 5 mol % Ho2Te3, and on the basis of Ho2Te3 -3 mol % Bi2Te3. Compounds Bi2Te3 and Ho2Te3 form a eutectic with a composition of 20 mol % Ho2Te3 and a temperature of 465°C.

The Effect of Fractional Replacement of Calcium with Lanthanum on the Characteristics of HgBa2Ca2-xLaxCu3O8+δ Compound

The current work involves the study of the substitution effect of calcium instead of lanthanum on the structural and electric characteristics at room of the HgBa2Ca2-1LaxCu3O8+ δ compound with (x = 0, 0.2, 0.4, 0.6 and 0.8). The specimens were manufactured via solid status reaction process. The results of X - radiation deviation showed for all samples a tetragonal system, containing the highest proportion of the pure (Hg - 1223) stage with low percentages for the minor phases (Hg - 1212, 1201) and appearance of some impurities, and the highest phase rate for the specimen at (x = 0.4) which is equal to (84.69%) and characterized by absence of impurities. The results of the measurement of the lattice constants, (c. 1 / a) and the density of mass shows that a sample with (x = 0.2) has the highest value (c / a = 4.602) and highest value of crystal size (D = 84.7 nm). The four - sensor procedure was achieved to detection the transition temperature Tc and the results confirmed the metal behavior of all samples. There was a change in the critical temperature, which increased from (111 to 119) Kelvin when the concentration of lanthanum increased from zero to 0. 2 and became 114 K at x = 0. 4 and then decreased to (105 and 98) Kelvin at x = 0.6 and 0.8.

CRYSTAL STRUCTURE ANALYSIS OF K3VF6 COMPOUND

The object of research is the crystal structure of the a phase of K3VF6 compound. From the analysis of the literature it follows that there are three modifications of this compound – the a phase, the b phase and the g phase. There are also several methods for preparing this compound. One of the problem areas is the existence of a large number of diffraction spectra obtained with the Bragg-Bertrand survey geometry in the PDF-2 database for 2004. There is also no complete data on the crystal structure of this compound. A structural model is proposed for the diffraction spectrum of the compound under the number 00-037-0738. The study used the PDF-2 database for 2004. As well as the HighScorePlus program, which allows to refine the microstructural parameters of the structural model by the Rietveld method. As a result, it is found that this diffraction spectrum of the compound under study can correspond to the following structural model: tetragonal system with lattice periods a=12.3524(4) A0; b=12.3524(4) A0; c=16.7447(7)A0. A possible spatial symmetry group is I41/a (88). Analyzing the obtained results, it can be assumed that the studied structure of the a phase of the compound crystallizes in its own structural type

Synthesis and properties of pyrazine-based oligomeric phthalonitrile resins

The pyrazine-based oligomeric phthalonitrile (PN) monomer, 2,6-bis[3-(3,4-dicyanophenoxy)phenoxy]pyrazine (BCPP), was synthesized from the reaction of an excess amount of resorcinol with 2,6-dichloropyrazine in the presence of potassium carbonate, followed by end-capping with 4-nitrophthalonitrile in a two-step, one-pot reaction. 4-(Aminophenoxy)phthalonitrile was applied to promote the curing reaction. The curing behavior was investigated by differential scanning calorimetry and rheological behavior, showing a wide processing window of 94°C, a complex viscosity of less than 1.5 Pa·s and a lower reaction activation energy of 32.57 kJ mol−1. The structure of the BCPP monomer was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The unit cell was determined to be tetragonal system by wide-angle X-ray diffraction. The monomer was cured to yield cross-linked polymers, which exhibited a high initial storage modulus, excellent glass transition temperature, outstanding thermal stability, and low water uptake.

Structure and magnetism of the solid solution GexFe4−xNy (0 ≤ x ≤ 1): from a ferromagnet to a spin glass

The experimental and theoretical study of the solid solution GexFe4−xNy (0 ≤ x ≤ 1) reveals a structural transition from the cubic to the tetragonal system as well as a magnetic transition from a ferromagnet to a spin glass accompanying the increasing germanium concentration.