scholarly journals Thermal Analysis of High Entropy Rare Earth Oxides

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3141 ◽  
Author(s):  
Sergey V. Ushakov ◽  
Shmuel Hayun ◽  
Weiping Gong ◽  
Alexandra Navrotsky
Keyword(s):  
Thermal Analysis ◽  
Rare Earth ◽  
Single Phase ◽  
Liquidus Surface ◽  
Combustion Method ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
X Ray ◽  
High Entropy ◽  
Rare Earth Sesquioxides

Phase transformations in multicomponent rare earth sesquioxides were studied by splat quenching from the melt, high temperature differential thermal analysis and synchrotron X-ray diffraction on laser-heated samples. Three compositions were prepared by the solution combustion method: (La,Sm,Dy,Er,RE)2O3, where all oxides are in equimolar ratios and RE is Nd or Gd or Y. After annealing at 800 °C, all powders contained mainly a phase of C-type bixbyite structure. After laser melting, all samples were quenched in a single-phase monoclinic B-type structure. Thermal analysis indicated three reversible phase transitions in the range 1900–2400 °C, assigned as transformations into A, H, and X rare earth sesquioxides structure types. Unit cell volumes and volume changes on C-B, B-A, and H-X transformations were measured by X-ray diffraction and consistent with the trend in pure rare earth sesquioxides. The formation of single-phase solid solutions was predicted by Calphad calculations. The melting point was determined for the (La,Sm,Dy,Er,Nd)2O3 sample as 2456 ± 12 °C, which is higher than for any of constituent oxides. An increase in melting temperature is probably related to nonideal mixing in the solid and/or the melt and prompts future investigation of the liquidus surface in Sm2O3-Dy2O3, Sm2O3-Er2O3, and Dy2O3-Er2O3 systems.

Preparation and Characteristics of Nanocrystalline Yttria by Microwave-Induced Solution Combustion Method

2016 ◽  
Vol 697 ◽  
pp. 18-22
Author(s):  
Yan Shuang Zhang ◽  
Yu Jun Zhang ◽  
Teng Li ◽  
Qi Song Li
Keyword(s):  
Single Phase ◽  
Combustion Method ◽  
Yttrium Nitrate ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
Solution Combustion Method ◽  
Powder Morphology ◽  
X Ray ◽  
Calcination Temperatures ◽  
Yttrium Acetate

Nanocrystalline yttria powders were successfully synthesized by microwave-induced solution combustion method using a binary yttrium salt system with yttrium nitrate as oxidant and yttrium acetate as reductant. The process involved the redox reaction between the two yttrium salt under the heat generated by absorbing microwaves. The prepared powders were characterized by X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) to study the structure and powder morphology. The prepared powders were indicated to exhibit single-phase cubic crystalline yttria structure. The oxidant/reductant ratios and the calcination temperatures had an effect upon the particle size and powder morphology. The size of the crystallites varied in the range of 16 nm~27 nm with different reductant proportion. The powders were observed to show loosely agglomerated fractals.

LiNi0.5Mn1.5O4 Prepared by a Solution Combustion Synthesis at Different Temperatures

2011 ◽  
Vol 186 ◽  
pp. 3-6
Author(s):  
Gui Yang Liu ◽  
Jun Ming Guo ◽  
Bao Sen Wang
Keyword(s):  
Electrochemical Performance ◽  
Single Phase ◽  
Solution Combustion Synthesis ◽  
Combustion Method ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
Solution Combustion Method ◽  
X Ray ◽  
Different Temperatures ◽  
Micro Morphology

LiNi0.5Mn1.5O4 powders have been prepared by a solution combustion method at 300-800oC. X-ray diffraction (XRD) and scanning electric microscope (SEM) were used to determine the phase composition and micro morphology of the products. The results indicate that the products with single phase LiNi0.5Mn1.5O4 can be obtained at 400-600oC. The electrochemical performance was tested by a coin-type battery. The product prepared at 600oC has the best electrochemical performance. The maximum capacity of the product prepared at 600oC is 135mAh/g at the current density of 30mA/g, and after 30 cycles, the capacity fades little.

scholarly journals Preparation of high-entropy carbides by different sintering techniques

2021 ◽  
Vol 56 (19) ◽  
pp. 11237-11247 ◽  
Author(s):  
Johannes Pötschke ◽  
Manisha Dahal ◽  
Mathias Herrmann ◽  
Anne Vornberger ◽  
Björn Matthey ◽  
...  
Keyword(s):  
Grain Size ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Vacuum Sintering ◽  
X Ray ◽  
High Entropy ◽  
Mean Grain Size ◽  
The Mean ◽  
Gas Pressure Sintering ◽  
Hardness Values

AbstractDense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples.

scholarly journals Mn-Induced Thermal Stability of L10 Phase in Fept Magnetic Nanoscale Ribbons

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1278
Author(s):  
Alina Daniela Crisan ◽  
Aurel Leca ◽  
Dan Pantelica ◽  
Ioan Dan ◽  
Ovidiu Crisan
Keyword(s):  
Rare Earth ◽  
Single Phase ◽  
Permanent Magnets ◽  
Magnetic Hysteresis ◽  
Ternary Alloys ◽  
Large Temperature ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Operation Conditions

Magnetic nanoscale materials exhibiting the L10 tetragonal phase such as FePt or ternary alloys derived from FePt show most promising magnetic properties as a novel class of rare earth free permanent magnets with high operating temperature. A granular alloy derived from binary FePt with low Pt content and the addition of Mn with the nominal composition Fe57Mn8Pt35 has been synthesized in the shape of melt-spun ribbons and subsequently annealed at 600 °C and 700 °C for promoting the formation of single phase, L10 tetragonal, hard magnetic phase. Proton-induced X-ray emission spectroscopy PIXE has been utilized for checking the compositional effect of Mn addition. Structural properties were analyzed using X-ray diffraction and diffractograms were analyzed using full profile Rietveld-type analysis with MAUD (Materials Analysis Using Diffraction) software. By using temperature-dependent synchrotron X-ray diffraction, the disorder–order phase transformation and the stability of the hard magnetic L10 phase were monitored over a large temperature range (50–800 °C). A large interval of structural stability of the L10 phase was observed and this stability was interpreted in terms of higher ordering of the L10 phase promoted by the Mn addition. It was moreover found that both crystal growth and unit cell expansion are inhibited, up to the highest temperature investigated (800 °C), proving thus that the Mn addition stabilizes the formed L10 structure further. Magnetic hysteresis loops confirmed structural data, revealing a strong coercive field for a sample wherein single phase, hard, magnetic tetragonal L10 exists. These findings open good perspectives for use as nanocomposite, rare earth free magnets, working in extreme operation conditions.

scholarly journals Improvement of the Photocatalytic Activity of ZnO/Burkeite Heterostructure Prepared by Combustion Method

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 817 ◽  
Author(s):  
A. Luna-Flores ◽  
M.A. Morales ◽  
R. Agustín-Serrano ◽  
R. Portillo ◽  
J.A. Luna-López ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Combustion Method ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
Solution Combustion Method ◽  
X Ray ◽  
Sem Image ◽  
Particle Aggregates ◽  
One Step ◽  
Ph Dependent

In this work, a novel route is discussed to produce in one step ZnO/Burkeite powders by the modified solution combustion method. The ZnO particles enhance the photocatalytic activity in the degradation of Rhodamine B, in which Burkeite mineral acts as a support due to the pH-dependent morphology of the particle aggregates of the as-synthesized powders. The X-ray diffraction (XRD) characterization shows the presence of a heterostructure: ZnO/Burkeite. The Scanning Electron Microscopy (SEM) image shows a morphological dependence with the pH of the solution used for the synthesis. The results show that the system with the highest degradation (92.4%) corresponds to the case in which ZnO/Burkeite heterostructure was synthesized with a pH 11.

Mullite formation from nonstoichiometric slow hydrolyzed single phase gels

1995 ◽  
Vol 10 (4) ◽  
pp. 912-917 ◽  
Author(s):  
Yong Wang ◽  
William J. Thomson
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Crystalline Phase ◽  
Single Phase ◽  
Formation Temperature ◽  
Mullite Formation ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spinel Formation

A comparative dynamic x-ray diffraction (DXRD) and differential thermal analysis (DTA) study was performed in the investigation of mullite and spinel formation from slowly hydrolyzed single phase gels with Al/Si ratios ranging from 1/1 to 14/1. Both metastable tetragonal mullite and spinel were observed to form at temperatures <1000 °C in the gels with Al/Si ratios <8/1 and mullite transformed to the orthorhombic structure at ∼1250 °C. However, at higher Al/Si ratios, spinel was the only crystalline phase detected at <1000 °C and orthorhombic mullite formed directly at temperatures >1250 °C. As the Al/Si ratio increases, both the tetragonal mullite and spinel formation temperatures decrease while the orthorhombic mullite formation temperature increases. Based on the Al/Si composition where the formation extents of tetragonal mullite and spinel were maximum, their compositions are estimated to be 2Al2O3 · SiO2 and 6A12O3 · SiO2, respectively.

Crystal Structure of BiFeO3 Synthesized Using the Hydrothermal Processing

2014 ◽  
Vol 602-603 ◽  
pp. 947-950
Author(s):  
Zhen Wang ◽  
Hai Yan Chen ◽  
Lin Qiang Gao ◽  
Xin Zou
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Thermal Analysis ◽  
Scanning Electron Microscopy ◽  
Single Phase ◽  
Hydrothermal Processing ◽  
Optimal Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

BiFeO3 nanoparticles were successfully synthesized by a hydrothermal method by a mineralizer (KNO3). Structural characterization was performed by thermal analysis, powder X-ray diffraction (XRD) and scanning electron microscopy (TEM).The results showed that the products were perovskite structure BiFeO3 powders. Optimal conditions for the synthesis of single-phase BiFeO3 ceramics were obtained.

EFFECT OF STRONTIUM DOPING ON NANOSTRUCTURE AND CHROMATICITY OF Y2O3:Eu COMPOUNDS

2011 ◽  
Vol 25 (22) ◽  
pp. 2949-2956 ◽  
Author(s):  
ALI MOHAMMADI ◽  
YADOLAH GANJKHANLOU ◽  
MAHMOOD KAZEMZAD ◽  
ABDOLMAJID BAYANDORI MOGHADDAM ◽  
FEREIDOUN ALIKHANI HESSARI ◽  
...  
Keyword(s):  
Emission Spectra ◽  
Photo Luminescence ◽  
Combustion Method ◽  
Urea Solution ◽  
Photoluminescence Intensity ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
Solution Combustion Method ◽  
X Ray ◽  
Transmission Electron

In this work, various nano-sized samples of Y 2 O 3, Y 2 O 3 :Eu and Y 2 O 3 :Eu , Sr were prepared by urea solution combustion method. Then the resultant nanopowders were investigated by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and photo-luminescence emission spectra. Furthermore, the CIE color coordinate of samples were calculated from photoluminescence emission spectra. Results showed that by doping of strontium, the photoluminescence intensity and chromaticity of Y 2 O 3: Eu phosphor was enhanced while crystallite size was decreased.

scholarly journals SÍNTESIS DE YAIO3 (YAP) POLICRISTALINO POR EL MÉTODO DE COMBUSTIÓN EN SOLUCIÓN

2018 ◽  
Vol 27 (1) ◽  
pp. 61
Author(s):  
A. Lazo ◽  
C. Paucarchuco ◽  
H. Loro
Keyword(s):  
Combustion Process ◽  
Orthorhombic Phase ◽  
Combustion Method ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
X Ray ◽  
Structure And Morphology ◽  
Palabras Clave ◽  
Diffraction Peaks ◽  
Ray Patterns

Se presenta el método de combustión en solución y su aplicación para la síntesis de YAlO3 (YAP), fueron usados como combustibles para la reacción de combustión y síntesis la urea y glicina, del YAP. Usando las técnicas de difracción de rayos X (XRD) por el método del polvo y microscopia electrónica de barrido (MEB) fueron analizadas la parte estructural y morfológica de las muestras obtenidas. Los difractogramas de Rayos X muestran una excelente correspondencia con lo reportado en la literatura para este material. Se suministran también los resultados de las muestras de material YAlxCrx‐1O3, dopado con Cr3+ con x = 0.001, 0.01, que exhiben picos de difracción dominantes debidos a la fase ortorrómbica de YAlO3 Palabras clave.- YAP, YAlO3, Combustion method. ABSTRACT The solution‐combustion process is presented, as well as its application to the synthesis of YAlO3 (YAP). Urea and glycine were used as fuel for the combustion reaction and synthesis of the YAP. The structure and morphology of the obtained sample were analyzed using the X‐ray diffraction (XRD) powder method and scanning electron microscopy (SEM). The X‐ray patterns showed an excellent agreement with data reported in the literature for this material. Results are also given for samples of YAlxCrx‐1O3 doped with Cr3+, with x = 0.001, 0.01, which showed dominant diffraction peaks due to the orthorhombic phase of YAlO3. Keywords.- YAP, YAlO3, combustion method.

Phase Assembly of Ti2SnC Powders

2011 ◽  
Vol 412 ◽  
pp. 187-190 ◽  
Author(s):  
Chun Long Guan ◽  
Guo Qin Liu ◽  
Ying Chun Shan
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Intermetallic Compounds ◽  
Single Phase ◽  
Reaction Path ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intermediate Phases ◽  
Reaction Equations ◽  
Phase Relationships

Ti2SnC powders (Ti: Sn: C =2: 1.2: 1, mol.%) were synthesized by pressureless sintering in argon in the temperature range of 600 to 1050°C using Ti, Sn and graphite powders as the initial materials. The phase relationships during reaction in the ternary system Ti-Sn-C have been investigated. The products for identification and analysis were characterized by X-ray diffraction (XRD) and differential thermal analysis (DTA). The reaction path for the formation of Ti2SnC can be described in the following steps. Sn melted at 230°C, which provided a favorable liquid circumstance for the reactions between Ti and Sn to form Ti-Sn intermetallic compounds. Results showed that Ti6Sn5 and Ti5Sn3 intermediate phases were formed in turn with increase of temperature. Up to 1050°C, with consumption of Ti5Sn3 phases completely, the amount of Ti2SnC increased significantly. Single phase Ti2SnC with small amount of TiC was produced. Combined with the results of differential thermal analysis (DTA) and X-ray diffraction (XRD), it is revealed that Ti2SnC phase is formed by the reaction of Ti–Sn intermetallic compounds, Ti and graphite. In addition, the reaction equations of the process from 230 to 1050°C were given.

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