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Nowadays the bone conditions have been a meaning clinical challenge and solutions are limited, sometimes ineffective. Hydroxyapatite investigation (main bone component) has gained significant importance. In this research, was analyzed the calcium precursor effect on structural and microstructural properties of hydroxyapatite comparing results of hydroxyapatite obtained from a natural source. Through the solution combustion synthesis were synthesized hydroxyapatite powders using calcium carbonate extracted from eggshell and commercial calcium carbonate and calcium nitrate. As well the natural source of hydroxyapatite was bovine bone which was washed, fractured and heat treatment. The functional groups were obtained by infrared spectroscopy and the crystalline phases by X-ray diffraction. Transmission electron microscopy allowed to determine the particle spherical morphology produced from calcium carbonate (eggshell) with the smallest size (~20-50 nm) while those obtained by commercial precursors presented nonhomogeneous morphology. The results showed that the respective process followed was efficient to get hydroxyapatite nanoparticles obtained from calcium carbonate at temperature of 1100ºC. Calcium carbonate from eggshells allowed getting HAp whose morphology was homogeneous with nanometric size. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of CuCo2InS4 and CuNi2InS4 alloys were prepared by the melt and anneal method. The products were characterized by X-Ray Diffraction (XRD) and Superconducting Quantum Interference Device (SQUID) techniques. From XRD it was found that both alloys, CuCo2InS4 and CuNi2InS4, are composed by two orthorhombic phases. In the case of CuCo2InS4, the crystal structure of the main phase has been refining (Rietveld method) as Pmn21 (N 31) with lattice parameters a=8.100(1) Å, b=7.116(8) Å and c=6.391(6) Å; for CuNi2InS4, the lattice parameters of the two phases were indexed (DICVOL 06). With respect to the magnetic behavior, CuCo2InS4 is a superconductor with Tc=3.2 K whereas CuNi2InS4 is a high temperature (Tc ~ 380 K) weak ferromagnetic with abnormal temperature dependence of the coercitive field. [ABSTRACT FROM AUTHOR]

Copyright of La Revista Latinoamericana de Metalurgia y Materiales, RLMM is the property of Universidad Simon Bolivar, Departmento de Ciencia de los Materiales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research describes the synthesis and characterization of the Pr3-XEuXBa5Cu8O18-δ system with modification levels (x = 0, 0.5, 1, 1.5, 2 and 2.5). The synthesis process was achieved by solid state reaction (SSR). Precursor oxides of Pr6O11, Eu2O3, BaO and CuO were used with purities up to 99.999%. Calcination temperatures were handled at 850 ° C, sintering at 900 ° C and oxygenation at 910 ° C. The structural characterization was determined by X-ray diffraction (XRD). A structural analysis was carried out with Rietveld refinement, where the coexistence of two phases TR358 and TR123 was evidenced. The net parameters were obtained and a perovskite-orthorhombic crystal structure with spatial group Pmmm (47) was achieved. It was concluded that the increase of the X modification level with Eu in the Pr3- XEuXBa5Cu8O18-d system has a large impact on the percentage composition of the phases and structural parameters. The increase or decrease of the value of the net parameters in structure 358 and 123 is affected by the mixture of oxidation states of Pr with those of Eu, causing the cell size to change. [ABSTRACT FROM AUTHOR]

Copyright of Ciencia en Desarrollo is the property of Universidad Pedagogica y Tecnologica de Colombia, Centro de Investigaciones y Extension and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The ternary semiconductor compound Cu2GeSe4 has been characterized by means of X-ray powder diffraction and refined by the Rietveld method. This compound crystallizes in the cubic system, space group F ... 3m (Nº 216), Z = 1, with unit cell parameters a = 5.5815(3) Å and V = 173.88 (3) ų. The refinement of 10 instrumental and structural parameters converged to the figures of merit Rp= 4.4%, Rwp= 6.8%, Rexp= 5.5%, RB= 6.0% and S= 1.2 for 4001 step intensities and 28 independent reflections. The Cu2GeSe4 structure can be described as derivative of the zincblende where Zn atoms are replaced by Cu and Ge atoms, and cationic vacancies. [ABSTRACT FROM AUTHOR]

In this work the relationship between the chemical composition and atomic volume in the Ag - x % Zn (x ⩽ 20) system was studied. For this purpose, 10 solid solutions were obtained by means of casting and mechanical alloying. The microstructural characterization was carried out by means of X ray diffraction. The lattice parameter was obtained using the Rietveld's method, while the chemical composition was determined by dispersive energy X-ray spectroscopy. Based on the results obtained, it can be concluded that there is an inverse lineal relationship between the atomic volume of the solid solution and its Zn concentration, which shows a negative deviation from Vegard's law (-2.96%). Additionally, it was proposed an equation which relates the Zn concentration with the atomic volume of the solid solution, which showed a prediction error less than 12%. [ABSTRACT FROM AUTHOR]

Copyright of Revista de la Sociedad Química del Perú is the property of Sociedad Quimica del Peru and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Powders of perovskite SrCo0.8Fe0.2O3-δ were synthesized using oxalate co-precipitation method. According to the thermal gravimetry and differential thermal analysis (TG/DTA), total mass loss was 40 % corresponding to three different steps and the precipitant agent as well the starting chemical elements have no influence on the process. Perovskite phase was identified by x-ray diffraction and the average crystallite size was 77.22 nm using iron nitrate (III) as starting material while 42.23 nm were obtained using iron oxalate (III). Ammonium oxalate and equimolar mixtures of ammonium oxalate and oxalic acid were used as precipitant agents and the results shown that these reactants have no influence on the average crystallite size (42.95 nm and 42.23 nm). The material presents isotherms of type II, with especific surface of approximately 4,41m2g-1. [ABSTRACT FROM AUTHOR]

Copyright of Revista de la Sociedad Química del Perú is the property of Sociedad Quimica del Peru and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de la Sociedad Química del Perú is the property of Sociedad Quimica del Peru and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main objective of this work is to analyze data of x-ray diffraction, by means of the application of Rietveld method. Quantitative analysis permitted the determination the weight percentage of the present phases in the YBa2Cu3O7/Sr2FeMnO6 composite. We have made a refinement of the crystalline structure for the two present phases, by using the GSAS software. These studies allow us to confirm that both materials (YBa2Cu3O7/Sr2FeMnO6) they are chemically stable even after remaining in contact during several hours to 900 C. [ABSTRACT FROM AUTHOR]

In this work is reported the synthesis of the perovskite oxides SmFeO3, SmMnO3 and Sm2FeMnO6 under same preparation conditions, by solid state reaction recipe, by optimization of thermal parameters. The structure characterization was performed by the Rietveld method. We find that all compounds have orthorhombic structure. Nevertheless, there are changes in the lattice parameters due to differences on the ionic radii of the Fe and Mn cations. [ABSTRACT FROM AUTHOR]

Yttrium and rare earth manganites crystallize in two principal phases: hexagonal and orthorhombic. For ions with small atomic radii Y, Yb and Ho the typical crystallization is hexagonal and for Sm, which has a smaller atomic radii, the crystallization is in orthorhombic phase. The preparation of the compounds R1-xSmxMnO3 was performed by the standard solid state reaction technique. Determination of crystal structure, lattice parameters and bond angle reported for these manganates were developed in the Rietveld method's context. The pure perovskites RMnO3 cristallized in the space group P63cm, the lattice parameters a and c achieve 6 Å and 11 Å, respectively, while SmMnO3 structure crystallizes at the special group Pnma. Rietveld refinement revealed the effects of Sm into the pure hexagonal structures, evidencing crystallographic changes with ortorrombic trends for strong concentrations of Sm. [ABSTRACT FROM AUTHOR]

We report a comparative study of graphite crystallographic parameters obtain by the method of Rietveld analysis and the predictions using Density Functional Theory (DFT). In order to obtain the lattice parameters from ab initio calculation we obtain the cohesion energy as a function of volume for the graphite. These data were fit by the Murnaghan state equation to evaluate the graphite crystallographic parameters. Results of the Rietveld method supply the values a=2.47 Å and c =6.73 Å. These values have a matching of 1% with that obtained from applied DFT method and experimental results. [ABSTRACT FROM AUTHOR]

In this paper fcc cells (face centered cubic ) type are described for the TiAlN compound, simulated in the Gaussian 98 software and presented in GaussianView 2.1, the lattice parameter was obtained from the diffraction patterns by means of the Rietveld method. For a total percentage of aluminum of 11,11%, of titanium of 37,04% and nitrogen 51,85%, the aluminum Atoms substitute atoms of Titanium in the cell, located in a randomized way, with two different distributions. It was evaluated the charge distributions, the electrons total density and the alpha and beta electrons density. It is observed that the cell possesses a coherent distribution of charges with the electronegatity of the present elements, the electrons total density is distributed continusly through the cell, the alpha and beta electrons density presents anomalous points due to the edge effect. [ABSTRACT FROM AUTHOR]

Nanostructured Hematite (α-Fe2vO3) powders were prepared by high-energy ball milling. The milling process spans grinding times from 30 minutes to 24 hours. The as-milled samples were cha-racterized by means of 57Fe Mössbauer spectrometry, Rietveld analysis of the X-ray diffraction data, and particle size analysis. The results obtained evidence the presence of disordered hematite characterized by a hyperfine field distribution with a well-behaved dependence with the mean crystallite size for which the mean hyperfine field decreases asymptotically as grain size decreases. A new relationship is proposed to describe such behavior. Finally, the presence of superparamagnetic grains, the occurrence of a partial topotactic phase transformation into a spinel phase, and the occurrence of tool-induced contamination is also presented and discussed. [ABSTRACT FROM AUTHOR]

The main objective of this work is to analyze data of x-ray diffraction, by means of the application of Rietveld method. Quantitative analysis permited to determine the weight percentage of the present phases in the YBa2Cu3O7/NdBa2SbO6 composite. We was made a refinement of the crystalline structure for the two present phases, by using the GSAS software. These studies allow us to confirm that both materials (YBa2Cu3O7/NdBa2SbO6) they are chemically stable even after remaining in contact during several hours to 900° C. [ABSTRACT FROM AUTHOR]

In this research we present the synthesis and characterization study of powder and bulk samples of La0.67Ca0.33MnO3-α (LCMO) manganites, prepared by solid state reactions. The analysis of the reaction was done by Thermogravimetry (TGA) and Differential Thermal Analysis (DTA) measurements, in air atmosphere with temperature increase of 10°C/min from 23°C to 900°C. In the TGA and DTA curves we observed different lost weight regions between 336°C and 705.32°C, due to decomposition of the precursor. Above this latter temperature, the reaction as stable. The final product was 85.17% of the starting mixture. Powder XRD measurements were fitted using Rietveld method. The observed crystalline structure was orthorhombic. The chemical composition by EDX measurements showed the phase of compound. The manganese ions (Mn3+ y Mn4+) content was determined by iodometric titration method. Finally, in the magnetometry measurements using SQUID with external applied field of 400 gauss and cooling without field from 300K to 20K, Curie temperature in the sample was measured (TC-251K). [ABSTRACT FROM AUTHOR]