scholarly journals Entropy-Stabilized Oxides owning Fluorite Structure obtained by Hydrothermal Treatment

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 558 ◽  
Author(s):  
Luca Spiridigliozzi ◽  
Claudio Ferone ◽  
Raffaele Cioffi ◽  
Grazia Accardo ◽  
Domenico Frattini ◽  
...  
Keyword(s):  
Single Phase ◽  
Configurational Entropy ◽  
Ceramic Materials ◽  
Fluorite Structure ◽  
X Ray Diffraction ◽  
State Transformation ◽  
Solid State Transformation ◽  
X Ray ◽  
Phase Stabilization ◽  
Single Phase State

Entropy-Stabilized Oxides (ESO) is a modern class of multicomponent advanced ceramic materials with attractive functional properties. Through a five-component oxide formulation, the configurational entropy is used to drive the phase stabilization over a reversible solid-state transformation from a multiphase to a single-phase state. In this paper, a new transition metal/rare earth entropy-stabilized oxide, with composition Ce0.2Zr0.2Y0.2Gd0.2La0.2O2−δ, was found after several investigations on alternative candidate systems. X-Ray Diffraction (XRD) analyses of calcined powders pointed out different behavior as a function of the composition and a single-phase fluorite structure was obtained after a specific thermal treatment at 1500 °C. Powders presented the absence of agglomeration, so that the sintered specimen exhibited sufficient densification with a small porosity, uniformly distributed in the sample.

The Effects of Cooling Rate Upon Xdt m TiAl Weld Microstructure

1990 ◽  
Vol 194 ◽  
Author(s):  
Erica Robertson ◽  
Mary Ann Hill ◽  
Ricardo B. Schwarz
Keyword(s):  
Solid State ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Mechanical Test ◽  
Test System ◽  
X Ray Diffraction ◽  
State Transformation ◽  
Solid State Transformation ◽  
X Ray ◽  
Weld Microstructure

AbstractFusion zone microstructures of an electron beam (EB) welded XDt m Ti–48at%Al + 6.5 vol% TiB2 alloy revealed plate-like precipitates which were absent in the base metal. The volume fraction of this phase increased with increasing cooling rate and correlated with increased weld cracking frequency. To determine whether this phase was a product of solidification from the melt or a product of a solid-state transformation, the microstructures of the welds were compared to those of samples cycled in a Gleeble 1500/20 Thermal-Mechanical Test System which was programmed to simulate the solid-state portion of the weld cooling rates (as predicted by a Rosenthal analysis). The microstructures were characterized by X-ray diffraction, optical and by scanning electron microscopy. The plate-like phase found in the weld microstructures was identified as TiB2 occurring upon rapid solidification of the melted weld metal.

In Situ High-Energy X-Ray Diffraction Studies of Melting, Solidification and Solid-State Transformation of Ni3Sn

MRS Advances ◽  
2020 ◽  
Vol 5 (29-30) ◽  
pp. 1529-1535 ◽  
Author(s):  
Rijie Zhao ◽  
Jianrong Gao ◽  
Yang Ren
Keyword(s):  
Solid State ◽  
Elevated Temperatures ◽  
High Energy ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
State Transformation ◽  
Solid State Transformation ◽  
X Ray ◽  
Melting And Solidification

AbstractMelting, solidification and solid-state transformation of the intermetallic Ni3Sn compound were investigated in situ using synchrotron high-energy X-ray diffraction. It was observed that the compound undergoes a hexagonal to cubic transition before melting. In solidification, a disordered cubic phase crystallizes from the liquid at a large undercooling but it is reordered prior to bulk solidification. In melting and solidification, forced or natural flows are active bringing about significant changes of crystal orientations. These in situ observations provided insights into phase transformations of Ni3Sn at elevated temperatures and their roles in formation of metastable microstructure consisting of coarse grains and subgrains.

scholarly journals Rapid processing of ferrite ceramics with promising magneto-dielectric characteristics

2017 ◽  
Vol 07 (06) ◽  
pp. 1750040 ◽  
Author(s):  
Zhuohao Xiao ◽  
Chuanhu Wang ◽  
Lie Liu ◽  
Zhihong Yang ◽  
Ling Bing Kong
Keyword(s):  
Single Phase ◽  
Ceramic Materials ◽  
X Ray Diffraction ◽  
Time Duration ◽  
Dielectric Characteristics ◽  
Sintering Aid ◽  
X Ray ◽  
Sintering Time ◽  
One Step ◽  
Rapid Processing

Ferrite ceramics, Ni[Formula: see text]Zn[Formula: see text]Co[Formula: see text]Fe[Formula: see text]O4, with the addition of 4[Formula: see text]wt.% Bi2O3 as sintering aid, were fabricated by using a simple one-step processing without involving the step of calcination. X-ray diffraction (XRD) results indicated that single phase ferrite ceramics can be achieved after sintering at 1000[Formula: see text]C for 2[Formula: see text]h. The samples demonstrated relative densities in the range of 97–99%. Desired magneto-dielectric properties have been approached by adjusting the sintering temperature and sintering time duration. This technique is believed to be applicable to other ceramic materials.

scholarly journals Structural Analysis of Nanoceria Powder Precipitated in Different pH

2016 ◽  
Vol 3 (02) ◽  
pp. 158
Author(s):  
Iis Nurhasanah ◽  
Nurul Wahyu Puspaningrum ◽  
Ida Nursati
Keyword(s):  
Crystallite Size ◽  
Single Phase ◽  
Inorganic Material ◽  
Mixed Solvent ◽  
Fluorite Structure ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sem Image ◽  
Sunscreen Product

<span>Nanoceria has been proposed as inorganic material for sunscreen product because of its <span>excellent UV absorpsition ability. Fine particle nanoceria and non-aglomeration determines <span>comport and covering capability on human skin. Particle size and aglomeration could be <span>controlled by parameters and medium synthesis. In the present work, nanoceria powders were <span>synthesized using precipitation method in different pH of 7 and 10. Precipitation was caried<br /><span>out in water/isopropanol mixed solvent. Cerium nitrate and amonium hydroxide was used as <span>source of cerium and precipitation agent, respectively. Crystal structure of nanoceria was <span>examined using x-ray diffraction (XRD). Scanning electron microscope (SEM) was used to <span>observe morphology of nanoceria. Diffraction pattern analysis shows that the precipitates <span>were single phase of nanoceria with cubic fluorite structure and lattice contants of 0.5429 nm<br /><span>and 0.5419 nm. Crystallite size and lattice strain were obtained from Williamson-Hall method. <span>Precipitation in pH of 7 resulted in smaller crystallite size which correlated to the larger lattice <span>strain and lattice constant. SEM image shows spherical morphology with less agglomeration <span>occuring for nanoceria precipitated in pH 10.</span></span></span></span></span></span></span></span></span></span></span></span></span><br /></span>

X-ray diffraction from one-dimensionally disordered 2H crystals undergoing solid state transformation to the 6H structure. III. Comparison with experimental observations on SiC

1980 ◽  
Vol 369 (1739) ◽  
pp. 463-477 ◽  
Keyword(s):  
Solid State ◽  
Deformation Mechanism ◽  
X Ray Diffraction ◽  
Fault Probability ◽  
State Transformation ◽  
Solid State Transformation ◽  
Simple Estimate ◽  
X Ray ◽  
Displacement Mechanism ◽  
Diffraction Effects

The diffraction effects predicted theoretically in the preceding two papers for 2H crystals undergoing solid state transformation to the 6H structure by the layer displacement mechanism and the deformation mechanism are compared with those experimentally observed on SiC. It is shown that the observed diffraction characteristics can be explained in terms of the layer displacement mechanism and not the deformation mechanism. A simple estimate of the layer displacement fault probability in two transformed 6H SiC crystals has been made by analysing the halfwidth of the experimentally obtained intensity profiles of the 10. L reflexions. It is also shown that the presence of a small concentration of growth faults in the as-grown 2H SiC crystal does not alter the basic diffraction characteristics predicted in part I of this series of papers.

Structure and Ionic Conductivity of Ln2Zr2O7-Type Rare Earth Zirconates

2007 ◽  
Vol 336-338 ◽  
pp. 420-423 ◽  
Author(s):  
Rui Zhang ◽  
Qiang Xu ◽  
Wei Pan ◽  
Chun Lei Wan ◽  
Long Hao Qi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Solid State ◽  
Ionic Conductivity ◽  
Single Phase ◽  
Complex Impedance ◽  
Pyrochlore Structure ◽  
Fluorite Structure ◽  
X Ray Diffraction ◽  
X Ray

Three rare earth zirconates (Sm2Zr2O7, Gd2Zr2O7 and Er2Zr2O7) were prepared by solid state reaction. The crystal structure and ionic conductivity of these zirconates were characterized by X-ray diffraction (XRD) and complex impedance spectroscopy. The results show that Sm2Zr2O7 exhibits single-phase pyrochlore structure and Er2Zr2O7 exhibits single-phase fluorite structure, while Gd2Zr2O7 has pyrochlore and fluorite structure. Among three zirconates, the ionic conductivity of Sm2Zr2O7 is highest, while that of Er2Zr2O7 is lowest.

X-ray diffraction from one-dimensionally disordered 2H crystals undergoing solid state transformation to the 6H structure II. The deformation mechanism

1980 ◽  
Vol 369 (1739) ◽  
pp. 451-461 ◽  
Keyword(s):  
Solid State ◽  
Deformation Mechanism ◽  
Random Distribution ◽  
Exact Expression ◽  
X Ray Diffraction ◽  
State Transformation ◽  
Solid State Transformation ◽  
X Ray ◽  
Diffraction Effects ◽  
Close Packed Layer

The 2H or AB Structure may be transformed to 6H or ABCACB structure if deformation faults occur preferentially after every third close-packed layer. The theory of X-ray diffraction from one-dimensionally disordered crystals undergoing the 2H → 6H structural transformation by such a deformation mechanism is developed. For this, it is necessary to consider that the faults are not distributed entirely at random but tend to occur in such a manner as to statistically create a 6H structure. An exact expression for the diffracted intensity for crystals undergoing the 2H → 6H transformation by the deformation mechanism has been obtained and the different observable diffraction effects have been predicted. These results are very different from those obtained of 2H crystals containing an entirely random distribution of deformation faults, especially for large fault probabilities.

X-ray diffraction from one-dimensionally disordered 2H crystals undergoing solid state transformation to the 6H structure. I. The layer displacement mechanism

1980 ◽  
Vol 369 (1739) ◽  
pp. 435-449 ◽  
Keyword(s):  
Diffraction Theory ◽  
Peak Shift ◽  
Exact Expression ◽  
X Ray Diffraction ◽  
State Transformation ◽  
Solid State Transformation ◽  
X Ray ◽  
Displacement Mechanism ◽  
Close Packed Structure ◽  
Integrated Intensity

The 2H or AB. . . close-packed structure may be transformed to 6H or ABCACB. . . structure if layer displacement faults occur preferentially on every third close-packed layer. The theory of X-ray diffraction from one-dimensionally disordered crystals undergoing the 2H → 6H structural transformation by such a layer displacement mechanism is developed. It is shown that it is necessary to consider that the faults do not occur entirely at random but prefer to occur at three-layer separations from each other in order to statistically create a 6H structure. The diffraction theory, as developed by earlier workers for 2H crystals containing a completely random distribution of stacking faults, cannot therefore be applied to the present case. An exact expression for the diffracted intensity from crystals undergoing the 2H → 6H transformation has been obtained and the different observable diffraction effects (like change in integrated intensity, peak shift, integral breadth, peak asymmetry) have been predicted.

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