Microstructure Formation of Al-Fe-Mn-Si Aluminides by Pressure-Assisted Reactive Sintering of Elemental Powder Mixtures

2009 ◽  
Vol 68 ◽  
pp. 21-33 ◽  
Author(s):  
Alfredo Flores ◽  
J.A. Toscano ◽  
S. Rodríguez ◽  
A. Salinas R. ◽  
Enrique Nava-Vázquez
Keyword(s):  
Microstructural Characterization ◽  
Rietveld Analysis ◽  
Reactive Sintering ◽  
X Ray Diffraction ◽  
Microstructure Formation ◽  
Powder Mixtures ◽  
X Ray ◽  
Intermediate Phases ◽  
Diffraction Patterns ◽  
Metallurgical Reactions

This paper presents the results of an investigation aimed at understanding microstructure formation of Al-Fe-Mn-Si intermetallics during pressure-assisted reactive sintering of elemental powders. The proportion of elements was selected such that the composition of the product was 55 wt % Al, 17 wt % Si, 14 wt % Mn, and 14 wt % Fe. Experiments were conducted at temperatures between 600 and 800°C, using compaction stresses of up to 20 MPa. Rietveld analysis of x-ray diffraction patterns of fully processed samples showed that the powders were transformed into a mixture of Al9FeMnSi and Al9FeMn2Si phases. However, as temperature and pressure were increased, the Al9FeMnSi phase was transformed into the Al9FeMn2Si phase. Differential Thermal Analysis, as well as microstructural characterization by scanning electron microscopy and x-ray diffraction, showed that these intermetallics do not form directly from the powder mixtures. Rather, they are the result of metallurgical reactions between a molten Al-Si solution and various intermediate phases formed during reactive sintering.

Microstructural characterization of ball-milled α-Al2O3: bimodal size distribution and shape anisotropy

2007 ◽  
Vol 40 (1) ◽  
pp. 33-39 ◽  
Author(s):  
Apurba Kanti Deb ◽  
Partha Chatterjee ◽  
Siba Prasad Sen Gupta
Keyword(s):  
Size Distribution ◽  
Goodness Of Fit ◽  
Microstructural Characterization ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
Bimodal Size Distribution ◽  
X Ray ◽  
Diffraction Patterns ◽  
Α Al2o3

α-Al2O3prepared by combustion technique was ball-milled in a planetary ball-mill for several hours. A detail microstructural characterization of the ball-milled samples was performed by X-ray line broadening analysis. X-ray diffraction patterns from the milled materials showed super-Lorentzian peak shapes for the α-Al2O3peak profiles, attributed to a bimodal size distribution of the α-Al2O3crystallites, one type of crystallites having spherical and the other having cylindrical morphology. Rietveld analysis using two different phase fractions of α-Al2O3with different microstructural features yielded a low goodness-of-fit of the X-ray data, indicating the suitability of the assumed model.

scholarly journals Dielectric and electrical properties of a mullite/glass composite from a kaolinite clay/mica-rich kaolin waste mixture

Cerâmica ◽  
2019 ◽  
Vol 65 (373) ◽  
pp. 117-121 ◽  
Author(s):  
J. P. F. Grilo ◽  
H. P. A. Alves ◽  
A. J. M. Araújo ◽  
R. M. Andrade ◽  
R. P. S. Dutra ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Glassy Phase ◽  
Low Cost ◽  
Microstructural Characterization ◽  
Reactive Sintering ◽  
X Ray Diffraction ◽  
Glass Composite ◽  
Kaolinite Clay ◽  
X Ray ◽  
Waste Mixture

Abstract A mullite/glass composite has been prepared by reactive sintering of a kaolinite clay/mica-rich kaolin waste mixture with 25 wt% waste. Phase composition, microstructure, dielectric and electrical properties of the composite fired at 1400 °C were evaluated by X-ray diffraction, scanning electron microscopy and impedance spectroscopy (between 25 and 600 °C in air). The microstructural characterization showed the attainment of dense samples composed of acicular (orthorhombic) mullite (47.6 wt%), glassy phase (50.1 wt%), and residual quartz (2.3 wt%). Electrical conductivity (1.9x10-8 S/cm at 300 °C), dielectric constant (6.7 at 1 MHz, 25 °C) and dielectric loss (0.024 at 1 MHz, 25 °C) results gave evidence that the mullite/glass composite is a promising low-cost material for commercial use in electronics-related applications.

X-ray powder diffraction analysis of the heteropoly-molybdate (MoO2)0.5PMo14O42

2003 ◽  
Vol 18 (3) ◽  
pp. 236-239 ◽  
Author(s):  
L. Marosi ◽  
J. Cifré ◽  
C. Otero Areán
Keyword(s):  
Catalytic Activity ◽  
Diffraction Analysis ◽  
Computer Modeling ◽  
Powder Diffraction ◽  
Rietveld Analysis ◽  
Nitrogen Atmosphere ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns

The new heteropoly blue compound (MoO2)0.5PMo14O42, which is relevant in the context of catalytic activity of heteropoly-molybdates, was prepared by controlled thermolysis of (NH4)3PMo12O40 at 730 K in a nitrogen atmosphere. Powder X-ray diffraction analysis showed that this compound has a cubic unit cell, space group Pn3m (No. 224), with ao=11.795(2) Å, Z=2 and DXR=4.2466 g cm−3. Computer modeling and Rietveld analysis of powder diffraction patterns led to a proposed structure of the corresponding Keggin-cage unit PMo14O42.

Structural Transformations of Boron Nitride Powders Obtained by Mechanical Milling Process

2009 ◽  
Vol 68 ◽  
pp. 101-108
Author(s):  
Rodrigo A. Esparza ◽  
J. Ayala ◽  
C. Ángeles-Chávez ◽  
G. Rosas ◽  
Ramiro Pérez
Keyword(s):  
Boron Nitride ◽  
Microstructural Characterization ◽  
Structural Transformations ◽  
Milling Process ◽  
X Ray Diffraction ◽  
Microstructural Characteristics ◽  
X Ray ◽  
Diffraction Patterns ◽  
Milled Powders

Mechanical milled powders of boron nitride were obtained. The microstructural characterization of these milled powders was carried out using X-ray diffraction technique. Insights on the nature of the crystalline phases obtained in these milled powders were obtained between comparisons of theoretical and experimental X-ray diffraction patterns. Observations on the phase transformations have been carried out using calorimetry and thermogravity experiments. Morphological and microstructural characteristics of nanocrystals are obtained using SEM and HRTEM instruments.

Development and Characterization of the Al2O3-YAG Ceramic Composites

2014 ◽  
Vol 798-799 ◽  
pp. 383-388 ◽  
Author(s):  
Eduardo Sousa Lima ◽  
A.P.O. Santos ◽  
L.M. Itaboray ◽  
C. Santos ◽  
R.F. Cabral
Keyword(s):  
Relative Density ◽  
Microstructural Characterization ◽  
Ceramic Composites ◽  
Oxide Ceramic ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
X Ray ◽  
Resistance To Oxidation ◽  
Oxidation And Corrosion

YAG (Y3Al5O12) and Al2O3 ceramics have high resistance to oxidation and corrosion in harsh environments and high temperatures, which turns into a quite attractive material as compared to other ceramics. Thus, lately oxide ceramic YAG has been extensively used as reinforcement phase to Al2O3 in order to obtain a composite with improved mechanical properties. This research focused on the development of sintered Al2O3-Y2O3 powder mixtures for the production of Al2O3-YAG composite. Powder mixtures composed of 63.65:36.35wt.% and 80.00:20.00wt.% of Al2O3 and Y2O3, respectively, were milled by planetary milling for 2h. The compositions were compacted by cold uniaxial pressing, at 70 MPa, for 30s. The two mixtures were sintered at 1500 and 1600°C for 3h. The samples were evaluated for relative density, shrinkage, weight loss, and X-Ray Diffraction (XRD). Scanning Electron Microscopy (SEM) was used for microstructural characterization. The X-Ray Diffraction showed the presence of Al2O3 and Y3Al5O12 as crystalline phases in both compositions. Samples composed by 80:20wt.% of Al2O3/Y2O3 powder sintered at 16000C-3h presented the higher relative density ranging around 86% of theoretical density.

A microstructural characterization of Co-Zr type permanent-magnet materials

1991 ◽  
Vol 49 ◽  
pp. 782-783
Author(s):  
K. R. Lawless ◽  
G. C. Hadjipanayis
Keyword(s):  
Melt Spinning ◽  
Microstructural Characterization ◽  
X Ray Diffraction ◽  
Ion Milling ◽  
X Ray ◽  
Heat Treated ◽  
Diffraction Patterns ◽  
Rapidly Solidified ◽  
Hard Magnetic Properties

Considerable interest has been shown recently in the hard magnetic properties of Co-Zr, Co-Zr-B, and Co-Hf-B alloys, but as yet no detailed microstructural studies have been published. The Co-Zr phase diagram seems to be reasonably well known, although the crystal structure of the Co11Zr2 phase is only partially determined. This paper will report on some preliminary studies of rapidly solidified Co-Zr-B-Si and Co-Hf-B-Si alloys and binary Co-Zr alloys.All specimens used in this study were prepared by melt spinning. Specific alloys were heat treated at temperatures from 650 to 900°C. TEM specimens were prepared from ribbon material by ion milling.X-ray diffraction studies of these alloys all showed a characteristic broad peak centered around d = 0.205nm. Although it was obvious that this was a complex peak, attempts to deconvolute it were unsuccessful. SAD patterns revealed that major phases in the alloys were very heavily faulted, thus giving rise to the very confusing X-ray diffraction patterns.

Intermetallic Hydrides Based on (Zr-Ti)(Fe-Cr)2 Type of Compounds

2006 ◽  
Vol 514-516 ◽  
pp. 666-671 ◽  
Author(s):  
Sofoklis S. Makridis ◽  
C. Christodoulou ◽  
Mary Konstantakou ◽  
Th.A. Steriotis ◽  
M. Daniil ◽  
...  
Keyword(s):  
Hydrogen Pressure ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Paramagnetic Behaviour ◽  
Diffraction Patterns ◽  
Microstructural Studies ◽  
Dominant Phase

In this work, the (Zr-Ti)(Fe-Cr)2 based compounds have been synthesized while charging-discharging hydrogen ability has been examined. Relatively low hydrogen pressure has been used for the hydrogenation of the samples. After following the discharging procedure, a high desorbed amount of hydrogen ~180 (ml of H2)/(gr of the alloy) has been measured on the first 15 min by using a volumetric device. The crystal structure has been analyzed by means of x-ray diffraction (XRD) while a Rietveld analysis has been performed on the x-ray diffraction patterns and the characteristic MgZn2 type of structure has found to be the dominant phase in both compounds. The scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) have been used for microstructural studies and quantitative analysis, respectively. Magnetic measurements have been performed on the samples and a paramagnetic behaviour has found to be at room temperature.

scholarly journals Microstructure and chemistry of MgO- and CoO-doped nickel-titanate spinels

1994 ◽  
Vol 52 ◽  
pp. 1002-1003
Author(s):  
I. M. Anderson ◽  
C. B. Carter ◽  
J. Bentley
Keyword(s):  
Single Phase ◽  
Spinel Phase ◽  
X Ray Diffraction ◽  
Uniform Size ◽  
Powder Mixtures ◽  
X Ray ◽  
Nickel Titanate ◽  
Diffraction Patterns ◽  
Faceted Particles ◽  
Single Set

When NiO-rich powder mixtures of NiO and TiO2 are equilibrated in air above ∼1425°C and subsequently quenched, X-ray diffraction patterns of the resulting specimens can be indexed with a single set of reflections in the Fd3m space group. Originally this result was cited as evidence of a highly nonstoichiometric single phase. However, subsequent TEM investigations showed that these specimens are composed of periclase- and spinelstructured phases with small domains and coherent phase boundaries. Periclase-structured domains are distributed throughout the spinel with two distinct morphologies: cuboidal particles, faceted on {100}, of uniform size that increases from 30 to 150 run with increasing NiO-mole-fraction; and an isotropic interconnected twophase microstructure, also of uniform size, varying from 2 to 5 ran seemingly independent of composition. The finer-scale features strongly resemble those arising from spinodal decomposition in an isotropic medium and can be ascribed to decomposition of a nonstoichiometric spinel phase during quenching. It has recently been suggested that the faceted particles coexist with the nonstoichiometric spinel at the equilibration temperature.

Rietveld Analysis of Ceramic Nuclear Waste Forms

1993 ◽  
Vol 333 ◽  
Author(s):  
T.J. White ◽  
H. Mitamura
Keyword(s):  
Rietveld Method ◽  
Amorphous Material ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Waste Forms ◽  
Simulated Waste ◽  
Diffraction Patterns ◽  
Nuclear Waste Forms ◽  
Selection Of

ABSTRACTPowder X-ray diffraction patterns were collected from three titanate waste forms - a calcine powder, a prototype ceramic without waste, and a ceramic containing 10 wt% JW-A simulated waste - and interpreted quantitatively using the Rietveld method. The calcine consisted of fluorite, pyrochlore, rutile, and amorphous material. The prototype waste form contained rutile, hollandite, zirconolite and perovskite. The phase constitution of the JW-A ceramic was freudenbergite, loveringite, hollandite, zirconolite, perovskite and baddeleyite. Procedures for the collection of X-ray data are described, as are assumptions inherent in the Rietveld approach. A selection of refined crystal data are presented.

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