X-ray Powder Diffraction Methods Research Articles

Phase behaviour of the ternary systems Rb2SO4(1)-RbBr(2)-H2O(3)/Cs2SO4(1)-CsBr(2)-H2O(3) at T = 288.15, 298.15, 308.15 K

The phase equilibrium and physic-chemical properties of Rb2SO4(1)-RbBr(2)-H2O(3)/Cs2SO4(1)-CsBr(2)-H2O(3) systems at T = (288.15, 298.15 and 308.15) K were determined by the isothermal solution saturation method. At the three temperatures, the two systems both contain one invariant point, two univariant curves, and three crystallization regions. The Schreinemaker’s wet residue method and X-ray powder diffraction method were used to verify the solid phase. The phase diagrams of Rb2SO4(1)-RbBr(2)-H2O(3) and Cs2SO4(1)-CsBr(2)-H2O(3) at the three temperatures show that higher temperature reduces the area of the crystallization region of the salts (RbBr and CsBr). The comparison of the two systems at 298.15 K suggests that the crystallization region area of the salts is strongly affected by the solubility and hydration ability of the salts. The refractive index of these systems reached the maximum at the invariant point. At different temperatures, the refractive index increases with increasing temperatures. The results in this paper may provide useful information for the separation of the salts from aqueous solution.

Preparation and characterization of wheat straw biochar loaded with aluminium/lanthanum hydroxides: a novel adsorbent for removing fluoride from drinking water

ABSTRACT In this work, a novel adsorbent of aluminium/lanthanum loaded wheat straw biochar (Al-La-WSB), was prepared by using a facile approach and used for fluoride removal. The Al-La-WSB and its pristine wheat straw biochar (WSB) were characterized by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray powder diffraction (XRD) methods. Batch adsorption experiments were carried out to investigate adsorbent performance, the highest removal rate was observed at pH 9, contact time of 7 h and Al-La-WSB dose of 1 g L−1. Lagergren pseudo-second-order kinetics and Langmuir isotherm model fitted the experimental data well. The maximum fluoride adsorption capacity of Al-La-WSB at different experiment temperature of 298, 308 and 318 K, was 51.28 mg g–1, 46.73 mg g–1 and 50.25 mg g–1, respectively, which was better than most reported adsorbents. The Al-La-WSB performed well over a considerable wide pH range of 3–10 and carried positive charge at pH < 4.8. The presence co-existing ions of SO4 2−, HCO3 −, Cl− and NO3 − had a minor impact on fluoride adsorption besides PO4 3−. Regeneration experiment results showed that the Al-La-WSB had an excellent reusability. According to the adsorbent characterization and batch adsorption experiment, the adsorption of fluoride on the Al-La-WSB was primarily a chemisorption, involving electrostatic interactions and ion exchange, which nitrate ion and hydroxyl played a major role. The results suggested that the Al-La-WSB could be a great adsorbent for removing fluoride from drinking water.

Ni–Fe, Co–Fe, and Co–Ni nanocomposites based on carbon nanotubes in the reaction of CO2 methanation

For effective carbon dioxide (CO2) methanation, bimetallic Co80Ni20/CNTs, Ni80Fe20/CNTs, and Co93Fe07/CNTs nanocomposite catalysts, where subscript numbers indicate the metal content (wt.%), have been prepared with wet impregnation method, further thermal decomposition, and chemical reduction stages using carbon nanotubes (CNTs) as a carrier. The catalysts were characterized using TG, SEM-EDX, argon physisorption, and X-ray powder diffraction methods. The pristine nanotubes demonstrated a slight activity in CO2 conversion due to the presence of small quantity of Ni. Among the tested nanocomposites the bimetallic Ni80Fe20/CNTs catalyst showed improved catalytic activity compared to Co80Ni20/CNTs and Co93Fe07/CNTs. The SEM-EDX analysis showed not uniform distribution of bimetallic aggregates on carbon nanotubes matrix for Ni80Fe20/CNTs and Co93Fe07/CNTs. However, this fact did not affect to catalytic properties of mentioned nanocomposites. Ni80Fe20/CNTs exhibited high activity in the CO2 methanation with 88% of CH4 yield at 350 °С unlike Co93Fe07/CNTs with 64% of CH4 yield.

Exploring the Slow Magnetic Relaxation of a Family of Photoluminescent 3D Lanthanide–Organic Frameworks Based on Dicarboxylate Ligands

A family of metal–organic frameworks with general formula {[Nd2(ant)2((NH2)2-bdc)(DMF)4]·2DMF}n (1) and {[Ln2(ant)2((NH2)2-bdc)(DMF)4]·2DMF·2H2O}n (Ln = Tb (2), Ho (3), and Er (4)) has been obtained from reactions between 9,10-anthracenedicarboxylic (H2ant) and 2,5-diaminoterephthalic ((NH2)2-H2bdc) acids, and lanthanide ions in dimethylformamide (DMF). These lanthanide–organic frameworks (LnOFs) have been characterized, and their crystal structures have been elucidated by single crystal and powder X-ray diffraction methods (on the basis of a comparative refinement with similar structures), respectively for 1 and 2–4. All LnOFs present three-dimensional structures composed of dinuclear [Ln2(µ-CO2)4] entities linked through both carboxylate ligands that yield open frameworks in which DMF and water molecules are located in the channels. Magnetic studies of these LnOFs have revealed slow relaxation of the magnetization for the Nd-based counterpart. The compounds also acknowledge relevant photoluminescence (PL) emissions in the visible (for the Tb-based homologue) and near-infrared (for the Nd- and Er-based compounds) regions. The strong green emission yielded by compound 2 at room temperature allows its study for photoluminescence (PL) sensing of various solvent molecules, finding a particular discrimination for acetone.

Development of a method for qualitative detection of lead chromate adulteration in turmeric powder using X-ray powder diffraction

This study aimed to develop and validate a powder X-ray diffraction method for the direct detection of PbCrO4 adulteration in turmeric powder. Different X-ray tube voltage (25–45 kV), tube current (25–45 mA), and scanning parameters (step size, 2θ° and time per step, s) were used and optimized on the angle of 15°–50° at 25°C with CuKα radiation (λ = 1.5418 Å). The PbCrO4 phase was identified based on the peak values of 2θ and miller indicate (hkl) and was confirmed using ICCD crystallography database. Based on the observation, X-ray tube voltage of 45kV, current of 45 mA, step size of 0.006 Å, and time per step of 150.450s were found to be the optimal diffraction conditions for detection of PbCrO4. This analysis confirms the applicability of powder XRD for the screening of PbCrO4 at various spiking levels in turmeric powder, with a limit of detection of 0.5%. The approach can be conveniently extended to other spice types.

Electrochemical hydrogenation, lithiation and sodiation of the GdFe2–xMx and GdMn2–xMx intermetallics

Electrochemical hydrogenation, lithiation and sodiation of the phases GdFe2–xMx and GdMn2–xMx (M=Mn, Co, Ni, Zn, and Mg) and the influence of doping components on electrochemical characteristics of electrode materials on their basis were studied using X-ray powder diffraction method, scanning electron microscopy, energy dispersive X-ray analysis, X-ray fluorescent spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Phase analysis showed a simple correspondence between unit cell parameters of the phases and atomic radii of doping elements. Electrode materials based on GdFe2 and GdMn2 doped with 2 at.% of Co, Ni and Mg demonstrated better hydrogen sorption properties than those doped with Mn and Zn. Corrosion resistance of the doped electrodes was also better than of the binary analogues (e.g. corrosion potential of the GdFe2-based electrode was –0.162 V whereas that of GdFe1.96Ni0.04 was –0.695 V). The capacity parameters were increased in the following ranges: Zn&lt;Mn&lt;Mg&lt;Co&lt;Ni and Zn&lt;Fe&lt;Mg&lt;Co&lt;Ni for GdFe2–xMx and GdMn2–xMx, respectively. After fifty cycles of charge/discharge, we observed the changes in surface morphology and composition of the electrode samples. In the structure of studied Laves type phases with MgCu2-type structure, the most suitable sites for hydrogen atoms are tetrahedral voids 8a. During lithiation and sodiation of the phases, the atoms of the M-component of the structure are replaced by the atoms of lithium, and the atoms of gadolinium are replaced by the atoms of sodium. This difference in interaction is due to the difference in atomic sizes of the atoms. No insertion of lithium or sodium into the structural voids of the phases was observed.

A SUPRAMOLECULAR STRUCTURE OF PHOSPHORYLATED N-PHENYL-1,2,4-TRIAZOLE- 3-THIONE AND ITS CRYSTAL SOLVATE

A comparative analysis of the molecular and crystal structures is performed for 5-[(diphenylphosphoryl) methyl]-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (1) in individual crystal (1a) and a crystal solvate with dimethylformamide (DMF) in the 1:1 ratio (1b). The crystals of both modifications have the identical geometries of the molecule of the key compound, and the crystals (despite their different crystal systems and unit cells parameters) are characterized by the formation of an identical one-dimensional supramolecular motif in them due to classical N–H...O hydrogen bonds and weaker noncovalent – C-H ... S interactions in crystal 1a and CH ... N in crystal 1b. A tetragonal packing of one-dimensional motifs oriented along the smallest unit cell parameter are observed in both cases. Solvate molecules are localized in zero-dimensional cavities in crystal 1b. Despite a denser molecular packing in crystal 1b, the solid-state phase transformation is observed for its polycrystalline sample, and the powder X-ray diffraction method shows that it partially transforms into form 1a with time. The latter form is characterized by a less dense molecular packing in the crystal.

Transformation of copper oxide and copper oxide nanoparticles in the soil and their accumulation by Hordeum sativum.

In recent years, the study of the influence of nanoparticles (NPs) on the environment has attracted much interest as nanotechnology is becoming the key technology of the future generation. The comparative studies on the effects of macro- and nanosized copper oxide (CuO) on plants rarely cover the state and behaviour of CuO in the soil-plant system. This work considers the transformation of CuO in Haplic Chernozem depending on the degree of dispersion and its toxic effects on spring barley (Hordeum sativum) growth. To investigate the transformation of the studied particles of metal oxide in the soil and plant, both chemical method of analysis and synchrotron radiation X-ray powder diffraction, X-ray absorption near-edge structure spectroscopy (XANES) and X-ray absorption fine-structure spectroscopy (EXAFS) were used. It was shown that CuO NPs underwent a stronger transformation due to the high reactivity of smaller particles. The Cu mobility was observed to increase within the soil profile as confirmed by the model pollution experiment. This is mainly due to the formation of complex forms of metal with organic matter. A dose of 300mg/kg of macro- and nanosized CuO did not significantly affect the development and productivity of spring barley. The effect of high doses of macro- and nanosized CuO (2000 and 10,000mg/kg) had a negative impact on the growth of spring barley. The application of nanosized CuO had a greater toxic effect than the macrosized CuO on the plants. The XANES and EXAFS data revealed that CuO NPs accumulated in the soil and plants. The linear combination fit shown that Cu atoms, incorporated into the plants, have environment typical of CuO. This indicates a high environmental risk when soil is contaminated with CuO NPs compared with its arrival as CuO.

Synthesis of heterovalently substituted slab perovskites Sr 2–xLnxBIV1–xBxIIIO4(BIV = Sn, Ti, BIII = Sc, In)

The possibility of the heterovalent substitution of A- and B-positions atoms in a single-layer slab perovskitelike structure of strontium titanate and stannate Sr2BIVO4 (BIV = Ti, Sn) by type Sr2–xLnxBIV1–xBxIIIO4 (Ln = La – Tb, BIV = Ti, Sn, BIII = Sc, In) has been established by X-ray powder diffraction methods. The boundaries of the heterovalent substitution of A- and B-positions atoms and the crystallographic parameters of the synthesized Sr2–xLnxBIV1–xBxIIIO4 phases with a single-layer structure are determined. The continuous phase area formation with a single-layer structure has been observed in 10 systems: Sr2–xLnxTi1–xScxO4 (Ln = La, Pr, Nd, Sm, Eu), Sr2–xLnxTi1–xInxO4 (Ln = La, Pr), Sr2–xLaxSn1–xScxO4, Sr2–xLnxSn1–xInxO4 (Ln = La, Pr). Increasing the degree of heterovalent substitution of atoms in these systems leads to a reduction of the sym metry of the crystal lattice of phases from the tetragonal (space group I4/mmm) to the interconnected rhombic one. In the rest of the studied Sr2–xLnxBIV1–xBxIIIO4 systems, the existence of a narrow (x value significantly less than 1) phase region with a single-layer structure based on Sr3BIVO7 is observed. The character of the phase relations in the Sr2–xLnxBIV1–xBxIIIO4 systems (Ln = La – Tb, BIII = Sc, In) (BIV = Sn, Ti) and the linear type of concentration dependences of the parameters of the reduced tetragonal unit cells of Sr2–xLnxBIV1–xBxIIIO4 phases with a single-layer structure indicate that, by their nature, these phases are series of solid solutions in the pseudobinary systems Sr2BIVO4 – SrLnBIIIO4 (BIV = Ti, Sn, BIII = Sc, In). The obtained data can be used to regulate the functional properties of titanates and stannates Sr2BIVO4 and materials based on them, as well as to solve the problem of a purposeful search for new compounds of the type An+1BnO3n+1 with a slab perovskite-like structure.

Significance of Cobalt Ferrite Nanoparticles on Superconducting Properties of Tl-1212 High Temperature Superconductor

Thallium-based high temperature superconductor (HTS) with nominal starting composition (Tl0.85Cr0.15)Sr2CaCu2O7-δ (Tl-1212) was prepared using high purity oxide powders via solid state reaction method. Small amounts (0.0 – 0.15 wt. %) of cobalt ferrite nanoparticles (CoFe2O4) were added into Tl-1212 superconductors. The effect of CoFe2O4 nanoparticles addition on the critical temperature (Tc), phase formation and microstructure properties including elemental compositional analysis were studied. The samples were investigated by the characterization of electrical resistance measurement, powder X-ray diffraction method (XRD), scanning electron microscopy and energy dispersive X-ray analysis (EDX). Zero-resistance temperature (Tc-zero) was found to reduce from 97 K to 89 K with increasing of CoFe2O4 nanoparticles concentration. Most of the samples indicated a dominant Tl-1212 phase of a tetragonal structure with a minor phase of Tl-1201. SEM micrographs with EDX mapping showed that CoFe2O4 nanoparticles were well distributed in all the samples.

Mucoadhesive gastroretentive microparticulate system for programmed delivery of famotidine and clarithromycin

Aim The present research was aimed to develop thiolated polyacrylic acid (TPA) based microspheres (MSPs) containing famotidine (FX) and clarithromycin (CLX). Methods TPA was synthesised from polyacrylic acid and l-cysteine in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC). The prepared TPA was characterised using FT-IR (Fourier transform-infra red), 1H-NMR (proton nuclear magnetic resonance) spectroscopy, P-XRD (powder X ray diffraction) method, and zeta potential. The analytical tools have supported the formation of TPA. The thiolated microspheres were prepared by emulsion solvent evaporation method using 0.75% w/v polymer concentration and stirring at 400 rpm for 8 hr. Results The average particle size and zeta potential of optimised formulation was found to be 25.2 ± 1.87 μm and –26.68 mV, respectively. The entrapment efficiency of the optimised formulation was obtained 67.20% for FX and 70.20% for CLX. The developed microspheres were swelled only in 4 h from 0.5 to 0.9. The in vitro mucoadhesive study and in vitro drug release studies demonstrated that microspheres showed mucoadhesive property. In in vitro drug release studies, the release of FX and CLX were observed to be 58.68% and 60.48%, respectively from microspheres in 8 h. The thiolated microspheres showed higher adhesion time (7.0 ± 0.8 h) in comparison to the plain microspheres (2.6 ± 0.4 h). Conclusion The prepared TPA based mucoadhesive microspheres can be utilised as carriers for the treatment of peptic ulcer caused by Helicobacter pylori which will offer enhanced residence time for the rational drug combination in the gastric region.

A Powder X-Ray Diffraction Method for Qualitative Detection of Potassium Bromate in Bakery Ingredients and Products

Potassium bromate is used in the baking industry as a bread improver and is known to improve dough kneading characteristics and bread volume. However, over the years, its carcinogenic nature has been established and KBrO3 is considered a hazardous adulterant in food systems. This study aimed to develop and validate a novel powder x-ray diffraction (PXRD) method for the detection of KBrO3 adulteration in bakery ingredients and products. Different combinations of x-ray tube voltage (25–45 kV), tube current (25–45 mA), step size (0.006°–0.13°), and time per step (50–150 s) were experimented on an angle of 15°–90° at 25 °C with CuKα radiation (λ = 1.5418 A). The KBrO3 phase was identified based on the peak values of 2θ and Miller indicate (hkl) and was confirmed using ICCD and COD crystallography databases. Based on the observation, x-ray tube voltage (45 kV), current (45 mA), step size (0.006 A), and net time per step (150.450 s) were found to be the optimal diffraction conditions for the detection of KBrO3. This study demonstrates the potential of XRD as a non-destructive, rapid, and reliable method for the detection of KBrO3 in bakery products.

Composition, Thermal Expansion and Phase Transitions in Framework Silicates: Revisitation and Review of Natural and Synthetic Analogues of Nepheline-, Feldspar- and Leucite-Mineral Groups

Framework silicates form about 70% of the Earth’s crust, mainly feldspars ~50–60% and quartz ~10–15%. Less-abundant feldspathoids include nepheline-, leucite-, and sodalite-group minerals, rich in structurally challenging properties. This review paper deals with anhydrous feldspar-, nepheline-, and leucite/pollucite groups, emphasising the importance of parallel studies on natural and synthetic samples. Four topics are covered. For decades, petrologists have analysed nephelines and recalculated their compositions as endmember molecules but, by not following rules of stuffed-tridymite crystal chemistry, have not estimated reliably the excess SiO2 present in solid solution. Some materials scientists make similar mistakes, and a new approach is described here. Synthesis studies of analogue feldspars, nephelines, and leucite/pollucites led to collaborative studies, mainly using laboratory and synchrotron X-ray powder diffraction methods at room and elevated temperatures, to study thermal expansion and displacive phase transitions. Such work was recently expanded to address the spontaneous strain relations. Topics covered here include work on nepheline/kalsilite analogues in the system SrAl2O4—BaAl2O4; thermal expansion of (K,Na)Al-, RbAl-, RbGa-, and SrAl-feldspars; and thermal expansion and phase transitions in analogue leucites KGaSi2O6 (tetragonal to cubic) and K2MgSi5O12 (monoclinic to orthorhombic). Results are reviewed in the context of research published in mineralogical and more-widely in physical sciences journals.

Structure analysis of electromagnetic waves absorbing material a lanthanum manganite system of (La0.8Ba0.2)(Mn(1-x)/2ZnxFe(1-x)/2)O3

Solid compound of lanthanum manganite system of (La0.8Ba0.2)(Mn(1-x)/2ZnxFe(1-x)/2)O3 has been synthesized via conventional solid state reaction route using lanthanum oxide (La2O3), barium carbonate (BaCO3), zinc oxide (ZnO), ferric oxide (Fe2O3) and manganese carbonate (MnCO3) powders as it raw materials. High energy ball milling was used to mix the material for 5 hours. It is then sintered at 1000°C for 5 hours. X-ray powder diffraction method (XRD) and scanning electron microscopy (SEM) was used to analyze the change of structure of the solid compound. The refinement pattern result of the XRD shown that a single phase was occurred in the form of (La0.8Ba0.2)(Mn0.4Zn0.2Fe0.4)O3. It has trigonal lattice crystal structure of (r-3c) point group with lattice parameter of a = b = 5.515 Å and c = 13.551 Å, α = β = 90° and γ = 120°, a volume unit cell of V = 356.904 Å3 and a density of ρ = 6.745 g.cm−3. The SEM result shown that the surface morphology of (La0.8Ba0.2)(Mn0.4Zn0.2Fe0.4)O3 has a homogeneous sphere structure. The XRD and SEM structure analysis result of the lanthanum manganite system of (La0.8Ba0.2)(Mn0.4Zn0.2Fe0.4)O3 shown that the compound is feasible for further studied.

Phase equilibrium in the system Y-Ni-In at 870 K

Interaction of the components in Y ‑ Ni ‑ In system was investigated by X-ray powder methods and isothermal section of phase diagram was constructed at 870 K in full concentration range. The samples were synthesized in an arc-furnace on a water-cooled Cu-plate under an argon atmosphere and annealed in silica tubes at 870 K for one month. The phase analysis was performed by X-ray powder diffraction method. Twelve ternary compounds, namely YNi 9 In 2 (YNi 9 In 2 -type structure), Y 1-1 . 40 Ni 4 In 1-0 . 60 (MgCu 4 Sn-type structure), YNiIn 2 (MgCuAl 2 -type structure), Y 4 Ni 11 In 20 (U 4 Ni 11 Ga 20 -type structure), YNi 1 . 00-0 . 50 In 1 . 00-1 . 50 (ZrNiAl-type structure), Y 2 Ni 2 In (Mn 2 AlB 2 -type structure), Y 2 Ni 1 . 78 In (Mo 2 FeB 2 -type structure), Y 5 Ni 2 In 4 (Lu 5 Ni 2 In 4 -type structure), Y 11 Ni 4 In 9 (Nd 11 Pd 4 In 9 -type structure), Y 12 Ni 6 In (Sm 12 Ni 6 In-type structure), Y 13.84 Ni 3.19 In 2.97 (Lu 14 Co 3 In 3 -type structure), ~Y 3 Ni 0.05 In 0.95 (AuCu 3 -type structure) exist in the Y ‑ Ni ‑ In system at the temperature of annealing. Compound Y 3 Ni 2.26 In 3.74 exists at higher temperature. The substitution of Ni for In was observed for YNi 1.00-0.50 In 1.00-1.50 and In for Y in the case of Y 1-1,40 Ni 4 In 1-0,60 compound. Besides, yttrium can enter the structure of NiIn (CoSn-type) leading to formation of including-subtraction type solid solution, which is stable for 0 ‑ 8 at. % Y. The composition of this solid solution can be described by the formula Y 0-0 . 16 NiIn 1-0 . 93 . The inclusion of yttrium and indium atoms in position (2 e ) with the simultaneous exclusion of a small amount of indium atoms from position (1 a ) takes place in the homogeneity range of this solid solution. The character of component interaction in the ternary Y ‑ Ni ‑ In system is similar to other related ternary system R ‑ T ‑ In ( R – rare earth of the yttrium subgroup). The common feature of all these systems is the existence of large number isotypical ternary compounds, the formation of homogeneity range for compounds with ZrNiAl and including-subtraction type solid solutions based on the binary compound NiIn. Keywords: yttrium, indium, nickel, phase equilibria, ternary compound, crystal structure.

Visible light driven enhancement in photodegradation of organic dyes using FexTi1-xO2 thin films

Fe doped TiO2 thin films (Fe, 0.02, 0.03, 0.04 and 0.05 mol %) were prepared using dip coating method. Dip coating method provides thin films of self-assembly with sol gel technique. The prepared thin films were subjected to different characterization studies. The structural properties of samples were analyzed with powder X-Ray diffraction method. It is observed that Fe ion incorporation has modified the crystallite size of TiO2 particle significantly which can have effect on the wavelength of the light source required for the photocatalytic process. The surface morphological properties were investigated via FESEM and AFM techniques. The higher concentration of Fe doped TiO2 thin films exhibit the larger surface area and roughness which leads to better enhancement for catalytic properties. The optical absorption studies showed the absorption edge of doped TiO2 samples has shifted towards longer wavelength region. The catalytic efficiency of prepared samples was investigated by the degradation of organic pollutants methylene blue and Congo red dyes and the results showed enhanced chemical reaction ensued between the methylene blue and Fe TiO2 samples. Further the treated water was used to grow plant like green gram (Vigna radiata) and the growth of plant was studied. The anatase phase, narrowing band gap, acidic surface sites and large surface area of Fe doped TiO2 thin film infer the sample as an efficient photocatalyst for environmental purification.

Experimental Investigation of Phase Equilibria in the Bi-Cu-Ge System

Abstract Phase diagram of the Bi-Ce-Ge ternary system has been investigated experimentally and thermodynamically extrapolated by using Pandat software. Experimental results were obtained using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and X-ray powder diffraction (XRD) methods. Examined ternary samples belong to two isothermal sections at 400 and 600 °C as well as three vertical sections Bi-CuGe, Cu-BiGe, and Ge-BiCu. No ternary compound has been detected in the equilibrated samples from the selected isothermal sections. Based on the presented experimental data and available literature data, description of the ternary system has been developed. A reasonable agreement between the experimental data and the calculated phase equilibria was obtained. As an example, ternary Cu80Bi10Ge10 alloy was selected for solidification simulations according to Scheil and Lever Rule assumptions as well as for simulation of the total fraction of each solid at different temperatures, latent heat, and total heat.

Исследование пигментов и связующих красочных слоев росписей храма X–XIII вв. на плато Эски-Кермен

In 2018–2019, the excavations of an aisleless church dated from the tenth to thirteenth centuries and located in quarter II on the territory of a provincial Byzantine town atop of the plateau of Eski-Kermen discovered fragments of wall-plaster with polychrome painting. There are several shades of green, two shades of red, white (beige), yellow (ochre), and grey-brown colours. This paper presents the results of studies of the colour layer, determines pigments and cohesive colour components, and uncovers the features of the painting technique applied to the walls of the church. Four groups of samples were selected for the study featuring: 1 – white, 2 – yellow, 3 – red, and 4 – green colours. The elemental composition of the colour layer was studied by scanning electron microscopy combined with energy-dispersive X-ray microanalysis (SEM/EDX). The phase constitution of the samples was investigated by X-ray powder diffraction (XRD) method with the use of diffractometers operated in a transmission mode at the Kurchatov synchrotron radiation source. The chemical composition of colour layers was studied by infrared spectroscopy, and the study of cohesive colour materials was carried out by gas chromatography with mass spectrometry (GC/MS). The elemental composition and phase constitution of the white colour indicated the use of lime whitewash. Yellow ochre (goethite) was used as yellow colour. Red colour features the presence of hematite typical for the group of pigments united under the name of red soils. However, the discovery of 1% goethite typical for yellow ochres in the phase constitution of one sample allows the possibility that burnt yellow ochre was used as a red pigment. The green colour was green soil (glauconite and celadonite). It should be noted that none of the examined samples of red pigment contained traces of vermilion, which occurred in ancient paintings in the Crimea and was typical for Byzantine wall-paintings. In all the samples of pigments contained a significant degree of calcite (36-98%), possibly due to the presence of particles of undercolour in the measured samples of wall paintings, or diluting the pigment with lime water for the making of wall-painting featuring fresco technique. The use of the latter technique is also indicated by the presence of white lime colour. The traces of cohesive component in the form of fish glue and protein products from chicken eggs found in the red and green paint samples also suggests the use of the dry painting technique. Therefore, there are reasons to suppose that the painting of the quarter church of Eski-Kermen used two techniques, fresco and dry plaster paintings.

Dobijanje kokristala paliperidona sa poboljšanom rastvorljivošću i brzinom rastvaranja

In the present study, co-crystals (CCs) of Paliperidone (PPD) with coformers like benzoic acid (BA) and P-amino benzoic acid (PABA) were synthesized and characterized to improve the physicochemical properties and dissolution rate. CCs were prepared by the solvent evaporation (SE) technique and were compared with the products formed by neat grinding (NG) and liquid assisted grinding (LAG) in their enhancement of solubility. The formation of CCs was confirmed by the IR spectroscopy, powder X-ray diffraction and thermal analysis methods. The saturation solubility studies indicate that the aqueous solubility of PPD-BA and PPD-PABA CCs was significantly improved to 1.343±0.162mg/ml and 1.964±0.452mg/ml, respectively, in comparison with the PPD solubility of 0.473mg/ml. This increase in solubility is 2.83-and 3.09-fold, respectively. PPD exhibited a poor dissolution of 37.8% in 60min, while the dissolution of the CCs improved tremendously to 96.07% and 89.65% in 60min. CCs of PPD with BA and PABA present a novel approach to overcome the solubility challenges of poorly water-soluble drug PPD.

Poly(L-glutamic acid) via catalytical hydrogenation for the fabrication of carbon nanotube nanocomposites

Abstract The synthesis of poly(L-glutamic acid) (PG) was investigated. Reduction of poly(benzyl-L-glutamate) by the palladium/charcoal catalyst proved to be an effective method for obtaining polyglutamic acid pure and particularly exhibiting in the α-helix secondary structure. The structure of this synthetic polypeptide was assessed by infrared spectroscopy, gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, temperature-modulated differential scanning calorimetry and wide-angle powder X-ray diffraction methods. The α-helical PG was, for the first time, combined with multi-walled carbon nanotubes (MWCNTs). The obtained PG was demonstrated to be a promising matrix to disperse MWCNTs, forming MWCNT/PG biocomposites.