Characterization of Nanostructured Mn-Zn Ferrites Synthesized by Coprecipitation Method Using CTAB

2020 ◽  
Vol 1012 ◽  
pp. 207-211
Author(s):  
Willian C.A. Maranhão ◽  
Rodrigo U. Ichikawa ◽  
X. Turrillas ◽  
Walter Kenji Yoshito ◽  
Margarida Juri Saeki ◽  
...  
Keyword(s):  
Hydrothermal Treatment ◽  
Rietveld Analysis ◽  
Coprecipitation Method ◽  
X Ray Diffraction ◽  
Ctab Concentration ◽  
Crystallite Sizes ◽  
Two Phases ◽  
Synthesized Materials ◽  
Ac Susceptometry

In this work it was investigated the influence of CTAB surfactant concentration on the synthesis of the compound Mn0.75Zn0.25Fe2O4 by the coprecipitation method. It was also compared the influence of hydrothermal treatment on the synthesized materials. The magnetic properties were characterized by AC susceptometry for the determination of the magnetic susceptibility and magnetic density energy. The phases, crystal structure and morphology of the nanoferrites were determined by Rietveld analysis of X-ray diffraction data. It was found the presence of two phases: Franklinite and Akaganeite and it was shown that the samples synthesized only by coprecipitation presented the tendency to increasing the crystallite sizes of the akaganeite phase and decreasing of crystallite sizes of the Franklinite phase as a function of CTAB concentration. The samples submitted to subsequent hydrothermal treatment presented a tendency to decreasing the crystallite sizes of both phases and increasing in Franklinite phase fraction, compared to the samples synthesized only by coprecipitation, suggesting that the hydrothermal treatment was effective in obtaining nanostructured materials of smaller particles.

Effect of cryogenic milling on Al7075 prepared by spark plasma sintering method

2017 ◽  
Vol 32 (S1) ◽  
pp. S221-S224 ◽  
Author(s):  
Frantisek Lukac ◽  
Tomas Chraska ◽  
Orsolya Molnarova ◽  
Premysl Malek ◽  
Jakub Cinert
Keyword(s):  
Spark Plasma Sintering ◽  
Rietveld Analysis ◽  
Deformation Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cryogenic Milling ◽  
Plasma Sintering ◽  
Crystallite Sizes ◽  
Spark Plasma ◽  
Sintering Method

Precipitation of secondary intermetallic phases in aluminium alloy Al7075 sintered by spark plasma sintering method from powders milled at room and cryogenic temperature was studied by X-ray powder diffraction. Deformation energy stored during cryogenic milling influences the precipitation in Al7075 alloy. High temperature X-ray diffraction experiment revealed the potential for further precipitation strengthening of samples prepared by spark plasma sintering of milled powders. It was established that the correction of absorption edge of metal Kβ-line filter used for laboratory sources greatly enhances the precision of quantitative Rietveld analysis as well as the determination of precipitates’ crystallite sizes.

scholarly journals Finite Element Simulation and Experimental Determination of Residual Stresses after Extrusion Process in Metal Matrix Composites

2005 ◽  
Vol 14 (4) ◽  
pp. 096369350501400
Author(s):  
G. Albertini ◽  
E. Girardin ◽  
A. Giuliani ◽  
D.E. Ilie ◽  
B.P. O'Donnell ◽  
...  
Keyword(s):  
Finite Element ◽  
Metal Matrix ◽  
Extrusion Process ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Element Analysis ◽  
Element Simulation ◽  
The Difference ◽  
Two Phases

The introduction of reinforcement in a Metal Matrix causes micro-stresses which may prove to be very detrimental for the life of the component. Submitting the components to annealing thermal treatments introduces thermal mismatch stresses. They are generated during cooling due to the difference between the thermal expansion coefficient of the two phases. Finite Element Analysis has been performed to study this effect and the results have been experimentally validated by X-ray diffraction, SEM investigation and EDAX on an AA2009 + 25% SiCp extruded shaft for helicopters, simplified as a thin extruded tube.

Microstructural Characterization of Silicon-Alloyed Pyrolytic Carbon for Mechanical Heart Valves

2011 ◽  
Vol 230-232 ◽  
pp. 420-423
Author(s):  
Jian Hui Zhang ◽  
Hai Bo Sun ◽  
Gen Ming Wang ◽  
Peng Hai Guo
Keyword(s):  
Heart Valves ◽  
Microstructural Characterization ◽  
Pyrolytic Carbon ◽  
Spherical Particles ◽  
X Ray Diffraction ◽  
Carbon Coatings ◽  
X Ray ◽  
Crystallite Sizes ◽  
Two Phases

Microstructural information obtained for silicon-alloyed pyrolytic carbon coatings used for heart valves using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy is described. The coatings consist of two phases, pyrolytic carbon and β silicon carbide, whose crystallite sizes are small. The coatings are principally composed of spherical particles that are from 300 to 1000 nm in diameter. These spherical particles, between which there are occasionally pores, are welded by laminar carbons. The silicon, content of which is moderate, disperses uniformly in the coatings.

A structural study of size-dependent lattice variation: In situ X-ray diffraction of the growth of goethite nanoparticles from 2-line ferrihydrite

2020 ◽  
Vol 105 (5) ◽  
pp. 652-663
Author(s):  
Peter J. Heaney ◽  
Matthew J. Oxman ◽  
Si Athena Chen
Keyword(s):  
Metal Oxides ◽  
Crystallite Size ◽  
Coefficient Of Thermal Expansion ◽  
Particle Growth ◽  
Rietveld Analysis ◽  
Order Kinetic ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Crystallite Sizes

Abstract Unlike most native metals, the unit cells of metal oxides tend to expand when crystallite sizes approach the nanoscale. Here we review different models that account for this behavior, and we present structural analyses for goethite (α-FeOOH) crystallites from ~10 to ~30 nm. The goethite was investigated during continuous particle growth via the hydrothermal transformation of 2-line ferrihydrite at pH 13.6 at 80, 90, and 100 °C using time-resolved, angle-dispersive synchrotron X-ray diffraction. Ferrihydrite gels were injected into polyimide capillaries with low background scattering, increasing the sensitivity for detecting diffraction from goethite nanocrystals that nucleated upon heating. Rietveld analysis enabled high-resolution extraction of crystallographic and kinetic data. Crystallite sizes for goethite increased with time at similar rates for all temperatures. With increasing crystallite size, goethite unit-cell volumes decreased, primarily as a result of contraction along the c-axis, the direction of closest-packing (space group Pnma). We introduce the coefficient of nanoscale contraction (CNC) as an analog to the coefficient of thermal expansion (CTE) to compare the dependence of lattice strain on crystallite size for goethite and other metal oxides, and we argue that nanoscale-induced crystallographic expansion is quantitatively similar to that produced when goethite is heated. In addition, our first-order kinetic model based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation yielded an activation energy for the transformation of ferrihydrite to goethite of 72.74 ± 0.2 kJ/mol, below reported values for hematite nucleation and growth.

A Practical Method for the Determination of the Instrumental Full Width at Half Maximum

1988 ◽  
Vol 3 (2) ◽  
pp. 84-85 ◽  
Author(s):  
D.M.A. Guérin ◽  
R.D. Bonetto ◽  
A.G. Alvarez
Keyword(s):  
Practical Method ◽  
Systematic Errors ◽  
Measuring Apparatus ◽  
Full Width ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutron Spectra ◽  
Morphologic Characteristics ◽  
Crystallite Sizes

X-ray diffraction and neutron spectra present a peak assembly whose maxima are centered at angles corresponding to Bragg's law.Analysis of diffracted intensity profiles in each peak can be used to estimate such morphologic characteristics of the samples as preferred orientation (Brindley and Kurtosy, 1961; Martin, 1966); crystallite sizes (Scherrer, 1919; Warren and Averbach, 1950; Wilson, 1962; and Guérin et al., 1986); and crystal shapes (Wilson, 1949). Such analysis can also be used to estimate the determination of residual stress and lattice defects (Warren and Averbach, 1950; Wilson, 1963). In such studies, a detailed analysis of the diffraction distribution is required and consequently adjustment of intensity values must be carried out, as they are affected by systematic errors in the measuring apparatus (for detailed description, see Klug and Alexander, 1974 and Wilson 1967).

scholarly journals Determination of hyperfine fields and atomic ordering in NiMnFeGe exhibiting martensitic transformation

Nukleonika ◽  
2015 ◽  
Vol 60 (1) ◽  
pp. 127-131 ◽  
Author(s):  
Dariusz Satuła ◽  
Krzysztof Szymański ◽  
Katarzyna Rećko ◽  
Wojciech Olszewski ◽  
Beata Kalska-Szostko
Keyword(s):  
Martensitic Transformation ◽  
Room Temperature ◽  
Paramagnetic State ◽  
Type Structure ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
Hyperfine Fields ◽  
X Ray ◽  
Two Phases

Abstract The hyperfine fields and atomic ordering in Ni1−xFexMnGe (x = 0.1, 0.2, 0.3) alloys were investigated using X-ray diffraction and Mössbauer spectroscopy at room temperature. The X-ray diffraction measurements show that the samples with x = 0.2, 0.3 crystallized in the hexagonal Ni2In-type of structure, whereas in the sample with x = 0.1, the coexistence of two phases, Ni2In- and orthorhombic TiNiSi-type of structures, were found. The Mössbauer spectra measured with x = 0.2, 0.3 show three doublets with different values of isomer shift (IS) and quadrupole splitting (QS) related to three different local surroundings of Fe atoms in the hexagonal Ni2In-type structure. It was shown that Fe atoms in the hexagonal Ni2In-type structure of as-cast Ni1−xFexMnGe alloys are preferentially located in Ni sites and small amount of Fe is located in Mn and probably in Ge sites. The spectrum for x = 0.1 shows the doublets in the central part of spectrum and a broad sextet. The doublets originate from the Fe atoms in the paramagnetic state of hexagonal Ni2In-type structure, whereas the sextet results from the Fe atoms in orthorhombic TiNiSi-type structure.

Nanoscale Topography of GC/Pt-C and GC/Pt-Ru-C Electrodes Studied by Means of STM, AFM and XRD Methods

2006 ◽  
Vol 518 ◽  
pp. 271-276 ◽  
Author(s):  
A. Kowal ◽  
P. Olszewski ◽  
D.V. Tripković ◽  
R. Stevanović
Keyword(s):  
Crystallite Size ◽  
Surface Area ◽  
Rietveld Method ◽  
High Surface ◽  
High Surface Area ◽  
Average Crystallite Size ◽  
X Ray Diffraction ◽  
Crystallite Sizes ◽  
Nanoscale Topography ◽  
Two Phases

Electrodes, assigned as GC/Pt-C and GC/Pt-Ru-C, were formed by deposition of Ptbased catalysts (47.5 wt % Pt + high surface area carbon) and (54 wt. % Pt-Ru alloy + high surface area carbon) on glassy carbon (GC) discs. X-ray diffraction measurements were used for the determination of the average crystallite size and phase composition of both catalysts. Crystallite size for Pt-C catalyst was 2.9 nm for Pt-fcc. In the diffraction pattern of the Pt-Ru-C catalyst two phases, e.g. Pt-Ru-fcc and Ru-hcp were refined using the Rietveld method. Crystallite sizes were 3.9 nm for Pt-Ru-fcc and 2.8 nm for Ru-hcp. STM observations of the surface of GC/Pt-C and GC/Pt-Ru-C electrodes revealed the presence of metal particles of the size in the range 2-6 nm and Pt-C or Pt- Ru-C agglomerates in the range of several tenth of nm. The thickness of the Nafion covering layer determined by AFM is ca. 100 nm. A simplified scheme of the investigated electrodes was created.

Determination of Atomic Positions in SiC 4H Using Quantitative Convergent Beam Refinements

1997 ◽  
Vol 3 (S2) ◽  
pp. 1051-1052
Author(s):  
R. Holmestad ◽  
J.-P. Morniroli ◽  
J.M. Zuo ◽  
J.C.H. Spence
Keyword(s):  
Electron Diffraction ◽  
Crystal Form ◽  
Hexagonal Structure ◽  
Double Layers ◽  
Stacking Sequence ◽  
X Ray Diffraction ◽  
Small Probe ◽  
Convergent Beam ◽  
Synthesized Materials

Silicon carbide (SiC) is a widely used ceramic material, with many structural and electronic applications. It exists in many polytypes, differing from one another only by the stacking sequence of close packed double layers of Si and C atoms. The polytype called 4H has the hexagonal structure shown in figure 1. The double layers here have a stacking sequence of ABACABAC.. The distance z between the Si and the C layers (shown in figure 1) is an adjustable parameter, which is not exactly known. The aim of this work is to determine the atomic positions in the c-direction by quantitative convergent beam electron diffraction (QCBED). The goal is to develop a general refinement approach for structure determination by electron diffraction. Many newly synthesized materials are available in only very small quantities in the single crystal form and/or mixed with other phases, making X-ray diffraction methods difficult. SiC is often full of stacking faults. For these types of materials, the CBED method is ideal because of the small probe that can be used; areas of less than 100 Å can be studied.

Determination of Crystal Structure of Cd3(BO3)2 by Powder X-Ray Diffraction

1991 ◽  
Vol 6 (1) ◽  
pp. 28-30 ◽  
Author(s):  
Y. Laureiro ◽  
M.L. Veiga ◽  
M.L. López ◽  
S. García-Martín ◽  
A. Jerez ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Low Temperatures ◽  
Rietveld Analysis ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Orthorhombic System ◽  
X Ray ◽  
Cell Parameters

AbstractCd3(BO3)2 was prepared by a solid state reaction between B(OH)3 and Cd(OH)2 at low temperatures ranging between 523° and 623° and at a pressure of 10−4 – 10−5 Hg mm. The crystal structure has been refined by Rietveld analysis of X-ray powder diffraction data. The compound crystallizes in the orthorhombic system, space group Pnnm, Z = 2, with cell parameters of a = 5.967(5) Å, b = 4.78 (0) Å and c = 9.009(5) Å.

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