Papers by Keyword: X-Ray Powder Diffraction

Abstract: A systematic study of samples of nominal composition A₁₄Cu₂₄O₄₁ (A = alkaline-earth metal) with partial replacement on the alkaline-earth metal sites and on the Cu sites was carried out. Layered cuprates of the (Sr,Ca)₂Cu₂O₃-CuO₂ series with partial substitution by Gd, Dy, and Er for Ca were obtained. X-ray powder diffraction analysis indicated that the solubility of the rare-earth metals in the Sr₈Ca₆Cu₂₄O₄₁ compound is limited to 2 atoms per formula unit. The Cu atoms in the structure of the spin-ladder phase can be replaced by Fe, Co, or Ni atoms up to the composition Sr₈Ca₆Cu₂₃Fe₁O₄₁, Sr₈Ca₆Cu₁₈Co₆O₄₁, or Sr₈Ca₆Cu₂₃Ni₁O₄₁, respectively, whereas attempts to replace part of the Cu atoms by Mn or Zn atoms were not successful.

Abstract: The phase equilibria in the ternary systems {Ce, Gd}–{Ti, Zr}–Sb were investigated by means of X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The isothermal sections of the phase diagrams at 600°C were constructed. The formation of three ternary compounds (Ce₂Ti₇Sb₁₂, Ce₃TiSb₅, and Gd₂Ti₁₁Sb₁₄) was confirmed in the {Ce, Gd}–Ti–Sb systems and no more ternaries were found. The investigation of the {Ce, Gd}–Zr–Sb systems revealed several new ternary compounds and confirmed the known ones. The crystal structure of the new compound Ce_0.08(3)Zr_1.92(3)Sb was determined from X-ray powder diffraction data. The other new compounds in the Ce–Zr–Sb system were found to have compositions close to ~CeZrSb₄ and ~Ce₂Zr₃Sb₅. In the Gd–Zr–Sb system the existence of a large homogeneity range was established for the GdZrSb compound along the isoconcentrate 33.3 at.% Sb: Gd_1-xZr_1+xSb (x = 00.905(18) at 600°C), and a new compound, ~Gd₃Zr₃Sb₁₄, was discovered. The crystal structures at the boundary compositions of the Gd_1-xZr_1+xSb phase were refined from X-ray powder diffraction data.

Abstract: This paper outlines the procedure for determining the sizes, structural parameters and percentage content of various particle types in nanographite powders by full-profile approximation of the X-ray diffractogram of sample with using a set of X-ray diffraction profiles for powders of model nanographites. It was shown that taking into account the model nanographites with the radial dependence of interatomic distances within the layer and the dependence of interlayer distances on average number of atoms in the layer allows to describe the X-ray diffraction profile of nanographite powder in the wide angular range including so-called γ-band in small angles without assumptions on presence of other structures in it.

Abstract: Aerated concrete is lightweight building material with excellent thermos-technical properties compared to its strengths, easy workability and economic efficiency. It is material with long tradition of manufacturing since 1924 but its potential is yet possible to be extended. Since the beginning pure ingredients such as lime and silica sand has been used. Nowadays we are looking for ways to replace these expensive raw materials with cheaper alternatives. One of the most important mechanical properties of each material is its strength. In case of aerated concrete the bearer of strength is mineral tobermorite. It is created by reaction of silicon oxides and lime at hydrothermal conditions. It belongs to the group of calcium hydrosilicates with chemical formula Ca₅Si₆O₁₆(OH)₂·4H₂O. Main goal of this paper is proposal for modification of the raw materials composition and autoclave regime of aerated concrete using aluminium hydroxide in order to improve final mechanical properties and mineralogical composition.

Abstract: Autoclaved aerated concrete is an ecological building material with suitable properties and long-time tradition. The research of secondary raw materials usage and technology optimization is needed in order to increase the efficiency and sustainability of its production. It is important to focus on development of mineralogical composition while studying the influence of input materials and the parameters of hydrothermal synthesis on the properties of final product. This is especially important in case of tobermorite formation as the bearer of strength in the structure. Main focus of this paper is applicability of fly ash (silica component) and admixture of energo-gypsum (sulfate component) in production of lime-ash composite in hydrothermal conditions. The research was focused on autoclaving of samples at temperature of 170°C in three various isothermal sustains. Final samples were analyzed by XRD and SEM in order to proof the influence of input materials. Results show that 5% admixture of energo-gypsum had positive influence on tobermorite formation.

Abstract: One known and nine new quaternary aluminides in the Al-rich region of R–T–Ag–Al (R = Y, Ce, Pr, Nd, Sm, and Gd, T = V, Nb, Ta, Cr, and Mo) systems were synthesized by arc melting and their crystal structures were studied by X-ray powder diffraction. The crystal structures of the compounds R₃T(Ag,Al)₂₀Al₁₂ (R = Ce, Pr, Nd, and Sm, T = V, Nb, Ta, Cr, and Mo) and R₃TAg_x(Ag,Al)₂₀Al₁₂ (R = Y and Gd, T = Ta) belong to new structure types: Ce₃Ta (Ag,Al)₂₀Al₁₂ (Pearson symbol сP36, space group Pm-3m, a = 8.6675(2) Å) and Gd₃TaAg_x(Ag,Al)₂₀Al₁₂ (сP4912.86, Pm-3m, a = 8.6158(5) Å), respectively. Within the rows of isotypic compounds the unit-cell parameter increases with increasing metallic radius of the rare-earth or d-element atom. The structure type Ce₃Ta (Ag,Al)₂₀Al₁₂ (Ce₃TaAg_7.97Al_24.03) is a partly ordered quaternary substitution derivative of the structure type BaHg₁₁, whereas Gd₃TaAg_x(Ag,Al)₂₀Al₁₂ (Gd₃TaAg_8.89Al_23.25) is a distorted fill-in quaternary substitution variant of the same prototype. The latter can also be described as a derivative of the structure type Y₃TaNi_6+xAl₂₆.

Abstract: The crystal structure of a new ternary aluminide of refined composition Sc₆Cu_24.1(2)Al_11.9(2) was solved by direct methods from X-ray powder diffraction data. It belongs to the cubic space group Im-3, Pearson symbol cI176-8, a = 13.5337(5) Å. The structure of Sc₆Cu_24.1Al_11.9 may be described as a packing of 16-vertex coordination polyhedra of the Sc atoms, which form icosahedral clusters around the origin and the center of the body-centered unit cell. The voids at the centers of the clusters are filled by Cu₄ tetrahedra, disordered between two possible orientations. The structure is closely related to the structure types Ru₃Be₁₇ and Ce₆Au_27.6Sn_6.8.

Abstract: Eleven new ternary compounds RTi₆Sn₄ (R = La-Nd, Sm) and RTi₆Pb₄ (R = Y, Gd-Er) were synthesized by arc-melting under purified argon. The crystal structures were refined from Xray powder diffraction data (structure type ZrFe₆Ge₄, Pearson symbol hR33, space group R-3m (#166)). They can be described as a stacking of layers formed by the coordination polyhedra of the Sn (Pb) atoms along the crystallographic direction [001].

Abstract: AFt phases – mainly ettringite and thaumasite, as products of sulfate attack in concrete, can cause serious damage to cement binder. The second mentioned, thaumasite CaSiO₃∙CaCO₃∙CaSO₄∙15H₂O, is connected to lower temperatures. It is less common and less known. For further research of this mineral, it is fundamental to prepare thaumasite in clear form in laboratory conditions. The aim of this work was to try several possibilities of thaumasite preparation - firstly by burning of mixes consisting of stoichiometric proportions of particular components in thaumasite and secondly by method in sugar solution and in MgSO₄ solution.

Abstract: A new Al-Cu-Nd system alloy, the high-purity Al₂Cu₃Nd ternary compound, was developed and prepared with the stoichiometric amounts of elemental constituents by arc melting under argon atmosphere. The X-ray diffraction (XRD) data of Al₂Cu₃Nd was collected by using the Rigaku Smart Lab X-ray powder diffractometer, and all X-ray diffraction peaks of Al₂Cu₃Nd compound were indexed successfully with the hexagonal structure. The Rietveld refinement results of the XRD pattern for the Al₂Cu₃Nd compound showed that the Al₂Cu₃Nd compound is the hexagonal structure, space group P6/mmm (No.191) with a = 5.2397(1) Å, c = 4.1783(1) Å, V = 99.34 ų, Z = 1. The density of the compound was 6.501 g/cm³, and its reference intensity ratio (RIR) w 1.26.