X-ray microstructure characterization of ball-milled nanocrystalline microwave dielectric CaZrO3by Rietveld method

2005 ◽  
Vol 38 (2) ◽  
pp. 291-298 ◽  
Author(s):  
S. K. Manik ◽  
S. K. Pradhan
Keyword(s):  
Rietveld Method ◽  
Early Stage ◽  
Structure Refinement ◽  
Milled Powder ◽  
Weight Fraction ◽  
High Energy ◽  
Mechanochemical Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Dielectric

The microwave dielectric CaZrO3has been prepared in nanocrystalline form by high-energy ball milling an equimolar powder mixture of CaO and monoclinic (m) ZrO2. The formation of CaZrO3is noticed in the X-ray diffraction pattern of 2 h ball-milled powder. At the early stage of milling, up to 4 h, the weight fraction of CaZrO3increases rapidly and then slowly reaches almost the saturation value of ∼73 wt% within 18 h of milling. It is observed that in the course of milling, the weight fraction ofc-ZrO2increases continuously from its starting value, ∼2.5 wt%, to ∼43 wt% within 2 h of milling, and then reduces slowly to its starting value. It seems that thec-ZrO2phase has been stabilized by CaO and takes part in the formation of CaZrO3by mechanochemical reaction of nanocrystalline CaO andc-ZrO2crystallites. However, post-annealing of 2, 6 and 18 h ball-milled samples results in the formation of ∼95 wt% CaZrO3phase. The formation mechanism, phase transition kinetics, structure and microstructure changes in terms of lattice imperfections and relative phase abundances of individual phases have been estimated from the analysis of X-ray powder diffraction data of unmilled, ball-milled and post-annealed samples by Rietveld powder structure refinement.

scholarly journals X-Ray Powder Diffraction Studies of Mechanically Milled Cobalt

2012 ◽  
Vol 626 ◽  
pp. 913-917
Author(s):  
W.S. Yeo ◽  
Z. Nur Amirah ◽  
H.S.C. Metselaar ◽  
T.H. Ong
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Surface Energy ◽  
Phase Formation ◽  
Rietveld Method ◽  
High Energy ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Structure Defects ◽  
X Ray

The allotropic phase transformation of cobalt powder prepared by high-energy ball milling was investigated as a function of milling time. Measurement of crystallite size and micro-strain in the powder systems milled for different times were conducted by X-ray diffractometry. The X-ray diffraction (XRD) peaks were analyzed using the Pearson VII profile function in conjunction with Rietveld method. X-ray diffraction line broadening revealed that allotropic transformation between face-centred-cubic phase (fcc) and hexagonal close-packed phase (hcp) in cobalt is grain size dependent and also on the accumulation of structure defects. The results showed that the phase formation of cobalt depends on the mill intensity that influences of both the grain size and the accumulation of structure defects. However, this theory alone is not adequate to explain the effects in this work. It was found that the total surface energy (Ω) theory satisfactorily explains the phase transformation behavior of cobalt. The smaller value of surface energy (Ω) of the fcc crystal than the hcp phase when size decreases may alter the qualitative aspects of the phase formation.

The In Situ Study on the Micro-Structural Characters of IF Steel at Early Stage of Recrystallization Using High-Energy X-Ray

2008 ◽  
Vol 575-578 ◽  
pp. 972-977
Author(s):  
He Tong ◽  
Yan Dong Liu ◽  
Q.W. Jiang ◽  
Y. Ren ◽  
G. Wang ◽  
...  
Keyword(s):  
Annealing Temperature ◽  
Early Stage ◽  
High Energy ◽  
Fiber Texture ◽  
Interstitial Free ◽  
If Steel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cold Rolled

High-energy synchrotron diffraction offers great potential for experimental study of recrystallization kinetics. A fine experimental design to study the recrystallization mechanism of Interstitial Free (IF) steel was implemented in this work. In-situ annealing process of cold-rolled IF steel with 80% reduction was observed using high-energy X-ray diffraction. Results show that, the diffraction intensity of {001}<110> and {112}<110> belong to α-fiber texture component decreased with the annealing temperature increased while {111}<110> did nearly not change and {111}<112> increased; the FMTH decreasing and d-space changing with annealing temperature increasing indicated that the residual stress relaxed completely during recovery.

Rietveld refinement of LaB6: data from µXRD

2005 ◽  
Vol 38 (5) ◽  
pp. 757-759 ◽  
Author(s):  
Guangrong Ning ◽  
Roberta L. Flemming
Keyword(s):  
Rietveld Refinement ◽  
Diffraction Data ◽  
Structural Information ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Quality Data ◽  
X Ray Diffraction ◽  
Diffraction Profile ◽  
Standard Material ◽  
X Ray

The Rietveld method of crystal structure refinement was an important breakthrough, allowing crystal structural information to be obtained from powder diffraction data. One remaining challenge is to collect Rietveld-quality data for polycrystalline mineralsin situ, using laboratory-based micro X-ray diffraction (µXRD) techniques. Here a new data collection method is presented, called `multiframes', which produces high-quality data, suitable for Rietveld refinement, using the Bruker D8 DISCOVER micro X-ray diffractometer. 91 frames of two-dimensional X-ray diffraction data were collected for powdered NIST SRM 660 LaB6standard material, using a general area-detector diffraction system (GADDS), at intervals of 0.8° 2θ. For each frame, only the central 1° 2θ was integrated and merged to produce a diffraction profile from 17 to 90° 2θ. Rietveld refinement of this data usingTOPAS2gave a unit-cell parameter (ao) and atomic position of boron (x) for LaB6of 4.1549 (1) Å and 0.1991 (9), respectively (Rwp= 4.26,RBragg= 3.21). The corresponding La—B bond length was calculated to be 3.0522 Å. These parameters are in good agreement with the literature values for LaB6. These encouraging results suggest that Rietveld-quality micro X-ray diffraction data can be collected from the Bruker D8 DISCOVER diffractometer, provided that the GADDS detector is stepped in small increments, for each frame only the central 1° 2θ is integrated at constant arc length, and counting time is sufficient to yield adequate intensity (∼10 000 counts).

Phase Analysis of Natural Silica-Sand-Based Composites as Potential Fuel-Cell Seal Material

2015 ◽  
Vol 1112 ◽  
pp. 294-298 ◽  
Author(s):  
Gabriela Amanda Gita Aristia ◽  
Istiqomah ◽  
Nurul Hidayat ◽  
Triwikantoro ◽  
Malik A. Baqiya ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Rietveld Method ◽  
Weight Fraction ◽  
Point Of View ◽  
Silica Sand ◽  
Adjacent Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Term Operation ◽  
Cell Components

Seal is one of the most important components in fuel cells which is required to bond the cell stacks and prevent mixing of gases in electrodes. Some of the requirements for such components are able to seal several adjacent cell components, which means compatible in thermal expansion coefficient values, and need to be chemically stable in a long-term operation. In this study, the potential use of natural silica sands from Bancar and Sowan in Tuban, East Java, Indonesia was explored, particularly from phase composition point of view. Six batches of samples were collected from both sites. X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) data from all samples were complementarily used in this study. XRF and XRD data for each sample showed that quartz (SiO2) was the most dominant phase, with estimated Rietveld method-based weight fraction content ranged between 70.1 and 98.7%. The second dominating phase is calcite (CaCO3). According to the results obtained, we found that there is a slightly difference in the value of phases weight fraction due to RIR and Rietveld methods. In this research, PB-01 sands mixed with 17 wt.% magnesia and were calcined at various temperatures. Natural silica-sand-based composite may give promising excellent candidate for seal fuel cell material, because it forms forsterite and enstatite which suit the CTE value of sealant of fuel cell.

Synthesis of Nanocrystalline Fe25Al57.5Ni17.5 by Mechanical Alloying

2012 ◽  
Vol 476-478 ◽  
pp. 1318-1321
Author(s):  
Qi Zhi Cao ◽  
Jing Zhang
Keyword(s):  
Thermal Analysis ◽  
Solid Solution ◽  
Differential Thermal Analysis ◽  
Mechanical Alloying ◽  
Ball Mill ◽  
Structural Changes ◽  
Early Stage ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray

Nanostructured Fe25Al57.5Ni17.5intermetallics was prepared directly by mechanical alloying (MA) in a high-energy planetary ball-mill. The phase transformations and structural changes occurring in the studied material during mechanical alloying were investigated by X-ray diffraction (XRD). Thermal behavior of the milled powders was examined by differential thermal analysis (DTA). Disordered Al(Fe,Ni) solid solution was formed at the early stage. After 50 h of milling, Al(Fe,Ni) solid solution transformed into Al3Ni2，AlFe3，AlFe0.23Ni0.77 phase. The power annealed at temperature 500 results in forming of intermetallics AlFe3 and FeNi3 after 5h milling. The nanocrystalline intermetallic compound was obtained after 500h milling.

The structural transformation of anatase TiO2 by high-energy vibrational ball milling

1999 ◽  
Vol 14 (3) ◽  
pp. 841-848 ◽  
Author(s):  
Suchitra Sen ◽  
M. L. Ram ◽  
S. Roy ◽  
B. K. Sarkar
Keyword(s):  
Electron Microscopy ◽  
Ball Milling ◽  
Structural Transformation ◽  
Milled Powder ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
First Time ◽  
Pressure Phase

The structural transformation of anatase TiO2 by high-energy vibrational ball milling was studied in detail by different analytical methods of x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This structural transformation involves both phase transition and nanoparticle formation, and no amorphization was observed. The crystallite size was found to decrease with milling time down to nanometer size ∼13 nm and approaching saturation, accompanied by phase transformation to metastable phases, i.e., TiO2(II), which is a high-pressure phase and TiO2(B), which was identified in ball-milled powder reported for the first time in this paper. These phases eventually started transforming to rutile by further milling.

Low Temperature Phase Transformation Study in the Al2O3-Y2O3-Nb2O5 System

2014 ◽  
Vol 798-799 ◽  
pp. 90-94
Author(s):  
Eduardo de Sousa Lima ◽  
A.P.O. Santos ◽  
R.F. Cabral ◽  
J.I.N. Fortini ◽  
Jose B. de Campos
Keyword(s):  
Yttrium Aluminum Garnet ◽  
Rietveld Method ◽  
High Energy ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Yttrium Aluminum ◽  
Energy Ball ◽  
Transformation Study ◽  
Low Temperature Phase

The mechanical properties and creep resistance of the Al2O3 have been improved with the use of other oxide ceramics, among these the Y3Al5O12 (YAG - "yttrium aluminum garnet"), to obtain the Al2O3-YAG composite. The aim of this work is to study the effect of addition of Nb2O5 at low sintering temperatures of the composite, starting from the eutectic composition Al2O3-Y2O3. In this work, the compositions were produced by powder mixtures of Al2O3-Y2O3 and Al2O3-Y2O3-Nb2O5 using high energy ball milling. The green bodies were pressed at 70 MPa and sintered at 1000, 1100, 1200 and 1300°C for 2 h. The materials were characterized by shrinkage and X-Ray Diffraction (XRD) using the Rietveld method. The presence of Nb2O5 does not show any improve neither for the YAG phase formation nor for the shrinkage of the sintered samples in the temperature range studied.

Study of the Sintering of Mixtures Al2O3-Nb2O5 and Y2O3-Nb2O5

2012 ◽  
Vol 727-728 ◽  
pp. 799-803 ◽  
Author(s):  
Ricardo F. Cabral ◽  
Marcelo Henrique Prado da Silva ◽  
Jose B. de Campos ◽  
Eduardo Sousa Lima
Keyword(s):  
Weight Loss ◽  
Mass Loss ◽  
Mole Fraction ◽  
Ball Mill ◽  
Rietveld Method ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Energy Milling

Al2O3-Nb2O5 has been widely explored as one of the most used material for sintering mixing in the literature, due to its excellent hardness properties, used in armor. In this study, Al2O3-Nb2O5 and Y2O3-Nb2O5 powders were prepared, with 50% in mole fraction of each oxide. The mixtures were subjected to high energy milling in an eccentric ball mill for 3 h, dried and sieved in a sieve vibrator. The green bodies were compacted at 70 MPa and sintered from 1250 to 1650 °C for 3 h, at 100 °C steps. The materials were characterized by quantitative X-Ray diffraction (XRD) using Rietveld method and by mass loss. The Al2O3-Nb2O5 mixtures experienced a weight loss of 84% at sintering temperatures of 1550 and 1650 °C.

Microstructure and Microhardness of Ball Milled/Hot Pressed Aluminium with Mg3n2 Addition

2013 ◽  
Vol 58 (2) ◽  
pp. 433-436
Author(s):  
M. Gajewska ◽  
J. Dutkiewicz ◽  
J. Morgiel
Keyword(s):  
Electron Microscopy ◽  
Structure Refinement ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Aluminium Powder ◽  
Transmission Electron ◽  
Magnesium Nitride ◽  
Significant Structure

The microstructure and microhardness of a ball milled and hot pressed aluminium powder with 10 vol.% of magnesium nitride (Mg3N2) were investigated. It was expected that the addition of a Mg3N2 as an nitrogen-bearing substrate would allow to obtain an in situ reaction leading to a formation of an aluminium nitride (AlN) strenghtening phase. The powders were milled in a high energy planetary ball mill for up to 40 h and then compacted in vacuum at 400ºC/600 MPa. The material was investigated by means of X-ray diffraction measurements (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and microhardness tests. The performed investigations showed that the composite preparation method provided a significant structure refinement of the material - the average matrix grain size of composite compact was about ˜140 nm. Energy Dispersive Spectrometry (EDS) analysis of Al/Mg3N2 compact combined with X-ray diffraction (XRD) technique indicated a presence of Mg3N2 as well as Mg-Al-O phase, which were probably formed during hot pressing. Microhardness tests showed nearly 40% increase in the hardness of Al/Mg3N2 composite over the non-reinforced aluminium compact.

Crystal structure refinement of the ferroelectric ceramic compound Sm2Bi2Ti3O12

1998 ◽  
Vol 13 (2) ◽  
pp. 113-115 ◽  
Author(s):  
M. E. Villafuerte-Castrejón ◽  
O. Alvarez-Fregoso ◽  
L. E. Sansores ◽  
A. Sànchez-Arjona ◽  
J. Duque ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Ferroelectric Ceramic ◽  
Crystal Structure Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
R Value ◽  
Ceramic Compound

Sm2Bi2Ti3O12 was synthesized by solid state reaction from Sm2O3, Bi2O3, and TiO2 in molar relation 1:1:3. Title compound is isostructural with Bi4Ti3O12. Products of the reaction were analyzed by X-ray diffraction methods. The crystal structure was refinement by the Rietveld Method. Cell parameters are: a=5.368(2), b=5.369(2), and c=32.71(2) Å, space group Fmmm. The final R value was 9.96% (Rw=13.43%).© 1998 International Center for Diffraction Data.

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