Papers by Keyword: X-Ray Powder Diffraction

Abstract: The formation of LiFeO₂ lithium ferrite from unmilled and milled Fe₂O₃-Li₂CO₃ mixture was studied by X-ray powder diffraction (XRD). The ball milling was perform via AGO-2S high-energy planetary ball mill at a rotational speed of 2220 rpm for 60 min. Solid-phase synthesis was carried out by conventional laboratory furnace at 600 °C. Using PowderCell 2.4 software, the structural parameters of the reagents and ferrite obtained from these were determined. According to the XRD data, the crystallite sizes of the milled reagents decreased, while the strains increased. It was found that the synthesized ferrite is characterized by multiphase composition consisting of unreacted initial reagents, α-LiFeO₂, γ-LiFeO₂ and α-Li_0.5Fe_2.5O₄ phases, the concentration of which depends on the prehistory of the mixture.

Abstract: Ternary compound Ti₄ZrSi₃ was prepared by arc melting using a non-consumable tungsten electrode under argon atmosphere, then annealed at 1023K for 30 days, the X-ray powder diffraction data of Ti₄ZrSi₃ was collected on a Rigaku SmartLab X-ray powder diffractometer. The powder patterns of the compound were indexed and structure refinement by using Rietveld method indicate that the Ti₄ZrSi₃ compound crystallizes in the hexagonal structure, space group P6/mcm (No.193) with Mn₅Si₃ structure type, a=b=7.5759(3) Ǻ, c=5.2162(2) Ǻ, V=259.28Ǻ³, Z=2, ρ_x=4.779g cm^-3, the Smith–Snyder FOM F₃₀=148.7(0.0064, 46) and the intensity ratio RIR=1.37. The Rietveld refinement results were R_p = 0.0836, R_wp= 0.1092.

Abstract: Nanotechnology is receiving widespread attention in many industrial sectors, including construction material industry. One of the nano-scale admixtures, which has the potential to enhance the performance of cement and concrete, is known as Nano-silica (n-SiO₂). In general, fly ash (FA) is currently used in cement and concrete industry for replacing the consumption of Portland cement (OPC) to reduce its production cost as well as to improve some specific required properties, e.g., workability or low internal heat liberation. However, the strength of hardened Portland cement is normally decreased when a higher amount of fly ash is presented. This research article is therefore pointed on the influence of nano-silica dosage on the properties of cement paste incorporating with high calcium fly ash. Seven different proportions of OPC:FA were prepared viz. 100:0, 80:20, 60:40, 50:50, 40:60, 20:80 and 0:100 by weight. The commercial grade nano-silica (in liquid form) was used as an admixture in those mixes by 0.0, 0.5, 1.0 and 1.5 wt% of the mixing water with a water-to-binder (w/b) ratio of 0.30. The results indicated that the addition of n-SiO₂ improved the compressive strength of all mixtures (with and without high calcium FA) as the presence of n-SiO₂ can be a source of silica and easily contribute to an additional formation of CSH in the cementing system, confirmed by the results of XRD analysis. The main findings show a potential approach of using n-SiO₂ as an admixture for cement and concrete construction.

Abstract: The effect of complex high-energy action, including mechanical milling of Li₂CO₃-Fe₂O₃-ZnO initial reagents mixture and its consistent heating by the pulsed electron beam on solid-phase synthesis was studied by X-ray powder diffraction and thermal analyses. The initial mixture Li₂CO₃-Fe₂O₃-ZnO corresponds to the ferrite with stoichiometric formula: Li_0.5(1–x)Zn_xFe_2.5–0.5xО₄, where х = 0.2. The same studies were carried out with thermal heating in a laboratory furnace for detection the effect of radiation on the formation of phase composition lithium-zinc ferrite. Initial mixture was milled in AGO-2S planetary ball mill with a milling speed of 2220 rpm for 60 min. Radiation-thermal synthesis of the milled mixture was carried out by the pulsed electron accelerator (ILU-6) at 600°C and 750°C. The maximum time of the isothermal stage was 60 minutes. According to the X-ray powder diffraction and thermogravimetric analysis, it was found that the complex high-energy action leads to decrease a temperature and time of obtaining lithium-zinc ferrite homogeneous in phase composition. The proposed high-energy regimes allow to synthesized lithium-zinc ferrites at 600 °C for 60 minutes, which is much lower compared to conventional ceramic technology.

Abstract: The crystal structure of the (Cr,Ni)₄Si phase with and without Co was refined from X-ray powder diffraction data. The compound crystallises with an Au₄Al-type structure (Pearson symbol cP20, space group P2₁3): unit-cell parameter a = 0.611959(6) nm for the composition (Cr_0.312Ni_0.688)₄Si, a = 0.612094(6) nm for (Cr_0.375Ni_0.625)₄Si, and a = 0.612316(6) nm for (Cr_0.337Co_0.063Ni_0.600)₄Si. The magnetic susceptibility was measured in external fields up to 7 T at temperatures between 1.8 and 400 K. The three investigated samples exhibited paramagnetic behaviour described by the modified Curie-Weiss law: χ₀ = 146∙10^-6 emu g-at.^-1, μ_eff = 0.21 μ_B/atom, θ_P = -13 K for (Cr_0.312Ni_0.688)₄Si; χ₀ = 158∙10^-6 emu g-at.^-1, μ_eff = 0.20 μ_B/atom, θ_P = -15 K for (Cr_0.375Ni_0.625)₄Si; χ₀ = 169∙10^-6 emu g-at.^-1, μ_eff = 0.18 μ_B/atom, θ_P = -52 K for (Cr_0.337Co_0.063Ni_0.600)₄Si.

Abstract: Nine new quaternary R₃MnAl₃Ge₂ alumogermanides (R = Sm, Gd-Lu) were synthesized by arc melting and their crystal structures were studied by X-ray powder diffraction. All of the compounds crystallize in hexagonal Y₃NiAl₃Ge₂-type structures: Pearson symbol hP9, space group P-62m. The unit-cell parameters of the isotypic compounds decrease with decreasing radius of the rare-earth metal. The hexagonal structure type Y₃NiAl₃Ge₂ (Z = 1) is a quaternary ordering variant of the binary type Fe₂P (Z = 3) and the ternary types β₁-K₂UF₆, Lu₃CoGa₅, Zr₃Cu₄Si₂ (Z = 1), ZrNiAl (Z = 3). It belongs to the family of structures with trigonal prismatic coordination of the small atoms.

Abstract: The crystal structure of the new ternary aluminide Sc_1.33Pd₃Al₈ was refined by the Rietveld method from X-ray powder diffraction data. It crystallizes with a Gd_1.33Pt₃Al₈-type structure: hR51-14.00, R-3m, a = 4.29142(4), c = 38.1638(4) Å, R_B = 0.0344. The main feature of the structure is the statistical distribution of Sc atoms and Al₃ triangles within atomic layers of composition Sc₂Al₃ (Sc_0.67Al within the translation unit here), which is likely to correspond to stacking disorder of ordered layers. During the final cycles of the refinement, the occupancies of the corresponding sites were fixed at occ. = 2/3 for Sc in Wyckoff position 6c and occ. = 1/3 for Al in 18h. The unit cell of Sc_1.33Pd₃Al₈ contains six Sc_0.67Al layers, nine Pd and eighteen Al atom layers along the crystallographic direction [001]. Together with the structure types Tb_0.67PdAl₃, Y₂Co₃Ga₉, Sc_0.67Fe₂Si₅, Er₄Pt₉Al₂₄, Yb_0.67Ni₂Al₆, and ErNi₃Al₉, the structure type Gd_1.33Pt₃Al₈ forms a family of intergrowth structures built up of three kinds of similar monoatomic layer.

Abstract: The crystal structures of the binary compounds ZrAl₃ and HfAl₃ at 600°C belong to the structure type ZrAl₃ (Pearson symbol tI16, space group I4/mmm, a = 4.00930(11), c = 17.2718(7) Å for ZrAl₃ and a = 3.9849(3), c = 17.1443(15) Å for HfAl₃). Substitution of Ge atoms for Al atoms in ZrAl₃ and HfAl₃ led to the formation of the ternary compounds ZrAl_2.52(1)Ge_0.48(1) and HfAl_2.40(1)Ge_0.60(1), respectively, where the latter is probably part of a solid solution extending from the high-temperature modification of HfAl₃. The crystal structures belong to the tetragonal structure type ht-TiAl₃ (tI8, I4/mmm, a = 3.92395(11), c = 9.0476(4) Å for ZrAl_2.52Ge_0.48 and a = 3.9021(2), c = 8.9549(8) Å for HfAl_2.40Ge_0.60). The structure types ZrAl₃ and ht-TiAl₃ are both members of the family of close-packed structures.

Abstract: The crystal structure of the binary compound DyGa₃ at 600°C belongs to the structure type Ta (Rh_0.33Pd_0.67)₃ (Pearson symbol hP40, space group P6₃/mmc: a = 6.1617(3), c = 23.0365(18) Å). Progressive substitution of Ge atoms for Ga atoms in DyGa₃ at 600°C led to the formation of two ternary compounds: DyGa_2.92-2.52Ge_0.08-0.48 (structure type Mg₃In, hR48, R3m, a = 6.1707(3)-6.22374(10), c = 27.7297(15)-28.1185(5) Å) and DyGa_2.32-2.20Ge_0.68-0.80 (PuAl₃, hP24, P6₃/mmc, a = 6.0970(3)-6.1091(6), c = 14.3153(8)-14.3528(14) Å). Both structure types belong to the family of close-packed structures, and the increase of the Ge content in the system DyGa_3-xGe_x is accompanied by a decrease of the hexagonality of the close-packing. Both ternary compounds exhibit metallic type of electrical conductivity.

Abstract: The isothermal section at 800°C of the phase diagram of the ternary system Sc–Cu–Al was constructed in the whole concentration range using X-ray powder diffraction data. The existence of eight ternary compounds was confirmed: ScCu_4.9‑6.0Al_7.1‑6.0 (structure type ThMn₁₂, Pearson symbol tI26, space group I4/mmm), Sc₆Cu_24.1Al_11.9 (own structure type, cI176, Im-3), Sc₂Cu_6.25Al_4.75 (own structure type, oS108, Cmmm), Sc₃Cu_7.5Al_7.5 (Sc₃Ni₁₁Ge₄, hP38, P6₃/mmc), ScCu₂Al (MnCu₂Al, cF16, Fm-3m), ScCu_0.8Al_0.2 (CsCl, cP2, Pm-3m), ScCu_0.6Al_1.4 (MgNi₂, hP24, P6₃/mmc), and ScCuAl (MgZn₂, hP12, P6₃/mmc), and the existence of a continuous solid solution ScCu_1-xAl_x (x = 0-1), based on the binary compounds ScCu and ScAl with CsCl-type structure (cP2, Pm-3m), was established. The investigation of the Ti–Cu–Al system at 800°C confirmed the existence of four ternary compounds: TiCu_0.25Al_2.75 (ZrAl₃, tI16, I4/mmm), TiCu_0.3-0.6Al_2.7-2.4 (Cu₃Au, cP4, Pm-3m), TiCu_2-2.7Al_1-0.3 (MnCu₂Al, cF16, Fm-3m), and TiCu_0.54-1.16Al_l.46-0.84 (MgZn₂, hP12, P6₃/mmc). Electrical resistivity measurements were performed for three compounds in the Sc–Cu–Al system and confirmed metal behavior in the temperature range 5-290 K.