Crystallization kinetics of yttrium aluminum garnet (Y3Al5O12)

2001 ◽  
Vol 16 (6) ◽  
pp. 1795-1805 ◽  
Author(s):  
Bradley R. Johnson ◽  
Waltraud M. Kriven
Keyword(s):  
Yttrium Aluminum Garnet ◽  
Three Dimensional ◽  
Constant Number ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Yttrium Aluminum ◽  
Temperature Transformation ◽  
Kinetics Of ◽  
Dimensional Crystal

The kinetics and pathways for crystallization of solid, amorphous, yttrium aluminum garnet (YAG) were studied using isothermal differential thermal analysis, x-ray diffraction, and transmission electron microscopy. The activation energy for crystallization was 437 KJ/mol and the measured Avrami exponent was 2.74, which corresponded to three-dimensional crystal growth with a constant number of nuclei. Time–temperature–transformation (T–T–T) curves were developed from the data to predict crystallization rates as a function of temperature. The crystallization pathway for YAG in this system is compared to others reported in the literature.

Influence of Sulfate Ion on Phase and Dispersion of Y3Al5O12 Nanopowders with the Co-Crystallization Method

2018 ◽  
Vol 281 ◽  
pp. 3-8
Author(s):  
Meng Meng Hao ◽  
Zi Qing Zeng ◽  
Gui Fen Fan ◽  
Xiao Hong Wang ◽  
Wen Zhong Lu ◽  
...  
Keyword(s):  
Yttrium Aluminum Garnet ◽  
Decomposition Temperature ◽  
X Ray Diffraction ◽  
Sulfate Ion ◽  
Xrd Pattern ◽  
X Ray ◽  
Crystallization Method ◽  
Transmission Electron ◽  
Pure Phase ◽  
Yttrium Aluminum

Yttrium aluminum garnet Y3Al5O12 (YAG) nanopowders were synthesized from co-crystallized precursors of Y2(SO4)3, Al(NO3)3-Al2(SO4)3 and Y(NO3)3 with a three-layer core-shell structure. X-ray diffraction (XRD) pattern indicated that too much was detrimental to the synthesis of pure phase YAG because of the serious separation between Y2(SO4)3 and Al(NO3)3-Al2(SO4)3. Transmission electron microscopy (TEM) revealed that was beneficial for the dispersion of the powders owing to the high decomposition temperature of . The powders with the n()/n(Y3+) mole ratio of 1.5/3 calcined at 1050°C showed good sintering activity.

Phase selection in precursor-derived yttrium aluminum garnet and related Al2O3–Y2O3 compositions

2005 ◽  
Vol 20 (4) ◽  
pp. 1017-1025 ◽  
Author(s):  
Ashutosh S. Gandhi ◽  
Carlos G. Levi
Keyword(s):  
Heat Treatment ◽  
Yttrium Aluminum Garnet ◽  
Lattice Parameter ◽  
Defect Structures ◽  
X Ray Diffraction ◽  
Phase Selection ◽  
X Ray ◽  
Yttrium Aluminum ◽  
Rich Side ◽  
Nitrate Solutions

Al2O3–Y2O3 powders were synthesized in the range of 25–55% Y2O3 by reverse coprecipitation of nitrate solutions. All starting powders were amorphous and formed primary yttrium aluminum garnet (YAG) upon crystallization. X-ray diffraction detected only garnet in compositions of 30–40% Y2O3 after heat treatment at 1250 °C. Compositions of 45–55% Y2O3 established a metastable YAG + Y4Al2O9 microstructure. The YAG phase field was metastably extended away from its stoichiometry, as indicated by a systematic increase in lattice parameter with Y2O3 content. Although some Al2O3 enrichment was achieved, YAG appears to tolerate greater off-stoichiometry on the Y2O3-rich side. Possible defect structures accommodating the solubility extension were examined. Phase selection results indicate that compositional inhomogeneity is not the only reason behind the appearance of hexagonal YAlO3, which is frequently reported during YAG synthesis.

scholarly journals Synthesis of Three-Dimensional Fe3O4/Graphene Aerogels for the Removal of Arsenic Ions from Water

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Yan Ye ◽  
Da Yin ◽  
Bin Wang ◽  
Qingwen Zhang
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
3D Structure ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Graphene Aerogels ◽  
Transmission Electron ◽  
Potential Applications ◽  
Removal Of Arsenic

We report the synthesis of three-dimensional Fe3O4/graphene aerogels (GAs) and their application for the removal of arsenic (As) ions from water. The morphology and properties of Fe3O4/GAs have been characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and superconducting quantum inference device. The 3D nanostructure shows that iron oxide nanoparticles are decorated on graphene with an interconnected network structure. It is found that Fe3O4/GAs own a capacity of As(V) ions adsorption up to 40.048 mg/g due to their remarkable 3D structure and existence of magnetic Fe3O4nanoparticles for separation. The adsorption isotherm matches well with the Langmuir model and kinetic analysis suggests that the adsorption process is pseudo-second-ordered. In addition to the excellent adsorption capability, Fe3O4/GAs can be easily and effectively separated from water, indicating potential applications in water treatment.

scholarly journals Low-Zpolymer sample supports for fixed-target serial femtosecond X-ray crystallography

2015 ◽  
Vol 48 (4) ◽  
pp. 1072-1079 ◽  
Author(s):  
Geoffrey K. Feld ◽  
Michael Heymann ◽  
W. Henry Benner ◽  
Tommaso Pardini ◽  
Ching-Ju Tsai ◽  
...  
Keyword(s):  
Protective Antigen ◽  
Three Dimensional ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Fixed Target ◽  
X Ray ◽  
X Ray Crystallography ◽  
Transmission Electron ◽  
Linac Coherent Light Source ◽  
Efficient Alternative

X-ray free-electron lasers (XFELs) offer a new avenue to the structural probing of complex materials, including biomolecules. Delivery of precious sample to the XFEL beam is a key consideration, as the sample of interest must be serially replaced after each destructive pulse. The fixed-target approach to sample delivery involves depositing samples on a thin-film support and subsequent serial introductionviaa translating stage. Some classes of biological materials, including two-dimensional protein crystals, must be introduced on fixed-target supports, as they require a flat surface to prevent sample wrinkling. A series of wafer and transmission electron microscopy (TEM)-style grid supports constructed of low-Zplastic have been custom-designed and produced. Aluminium TEM grid holders were engineered, capable of delivering up to 20 different conventional or plastic TEM grids using fixed-target stages available at the Linac Coherent Light Source (LCLS). As proof-of-principle, X-ray diffraction has been demonstrated from two-dimensional crystals of bacteriorhodopsin and three-dimensional crystals of anthrax toxin protective antigen mounted on these supports at the LCLS. The benefits and limitations of these low-Zfixed-target supports are discussed; it is the authors' belief that they represent a viable and efficient alternative to previously reported fixed-target supports for conducting diffraction studies with XFELs.

Contribution of the hybrid component to the structure and properties of ceramics based on metastable phases Al2O3

2021 ◽  
pp. 127-136
Author(s):  
A. V. Maletsky ◽  
T. E. Konstantinova ◽  
D. R. Belichko ◽  
G. K. Volkova ◽  
V. V. Burkhovetsky
Keyword(s):  
Mechanical Properties ◽  
Yttrium Aluminum Garnet ◽  
Metastable Phase ◽  
Physical And Mechanical Properties ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Mutual Inhibition ◽  
X Ray ◽  
Tetragonal Lattice ◽  
Yttrium Aluminum

The paper presents results of the study of the effect of doping with yttrium oxide on ceramics of the composition (γ + θ) Al2O3 + nY2O3 (n = 0, 1, 2, 3 wt%), sintered at 1550°C for 2 h, from powders of the specified composition annealed at temperatures of 500 , 800, 1000°С. X-ray diffraction analysis established the formation in ceramics of yttrium aluminum garnet Y3Al5O12 (YAG) and a metastable phase of the same composition with a tetragonal lattice type in powders at temperatures above 1200°C. The effect of YAG on the physical and mechanical properties was established: high properties were demonstrated by ceramics of the composition α-Al2O3 + 2wt% Y2O3, obtained from a powder annealed at 1000°C. In addition, high physical and mechanical properties were observed in ceramics of the composition α-Al2O3 + 0wt% Y2O3, obtained from a powder annealed at 800°C. The effect of the so-called “mutual protection against crystallization” was discovered, which consists in the mutual inhibition of crystallization processes in powders of the Al2O3 – Y2O3 system.

Three-dimensional morphology of anatase nanocrystals obtained from supercritical flow synthesis with industrial grade TiOSO4 precursor

2019 ◽  
Vol 75 (6) ◽  
pp. 1086-1095 ◽  
Author(s):  
Jinlong Yu ◽  
Frederik Søndergaard-Pedersen ◽  
Aref Mamakhel ◽  
Paolo Lamagni ◽  
Bo Brummerstedt Iversen
Keyword(s):  
Three Dimensional ◽  
High Specific Surface Area ◽  
X Ray Diffraction ◽  
Titanyl Sulfate ◽  
Supercritical Flow ◽  
Price Expectation ◽  
X Ray ◽  
Industrial Grade ◽  
Transmission Electron ◽  
Dimensional Reconstruction

Anatase TiO2 (a-TiO2) nanocrystals are vital in catalytic applications both as catalysts (e.g. photodegradation) and as a carrier material (e.g. NOx removal from exhaust). The synthesis of a-TiO2 nanocrystals and their properties have been heavily scrutinized, but there exists a clear gap between the scientific literature, and the scale and price expectation of industrial application. Here it is demonstrated that the industrially most attractive Ti precursor, titanyl sulfate (TiOSO4), can be combined with the green, scalable and fast supercritical flow method to produce phase pure and highly crystalline a-TiO2 nanoparticles with high specific surface area. Control of the nanocrystal morphology is important since it is known that certain facets substantially promote catalytic activity. It is, however, in itself challenging to determine nanocrystal morphology to provide a rational basis for the synthesis control. Here we advocate the use of advanced Rietveld refinement of powder X-ray diffraction data including anisotropic size broadening models in aiding to establish the sample three-dimensional morphology. This relatively quick and robust method assists in overcoming the often encountered ambiguity inherent in two-dimensional to three-dimensional reconstruction of selected particle morphologies with transmission electron microscopy and tomography techniques.

Transformation kinetics for mullite in kaolin–Al2O3 ceramics

2003 ◽  
Vol 18 (6) ◽  
pp. 1355-1362 ◽  
Author(s):  
Yung-Feng Chen ◽  
Moo-Chin Wang ◽  
Min-Hsiung Hon
Keyword(s):  
Glassy Phase ◽  
Avrami Equation ◽  
Mullite Formation ◽  
Transformation Kinetics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Energy Dispersion Spectrometry ◽  
Two Stages ◽  
Kinetics Of

Transformation kinetics of mullite formation in kaolin–Al2O3 ceramics was studied by x-ray diffraction, transmission electron microscopy, and energy dispersion spectrometry. The mullitization process of kaolin–Al2O3 ceramics is described by two stages; one is the primary mullite transformation at 1273 to 1573 K, and the other is the secondary mullite formation at 1573 to 1873 K. The activation energy of 1164.6 kJ mol-1 obtained for the secondary mullite formation is lower than 1356.9 kJ mol-1 for the primary mullite transformation by the general form of the Johnson–Mehl–Avrami equation. The lower value of growth morphology parameter strongly supports that in the secondary mullite formation the added alumina is dissolved into glassy phase and the mullite is then precipitated.

Characterization of Nanocrystalline γ–Fe2O3Prepared by Wet Chemical Method

1999 ◽  
Vol 14 (4) ◽  
pp. 1570-1575 ◽  
Author(s):  
G. Ennas ◽  
G. Marongiu ◽  
A. Musinu ◽  
A. Falqui ◽  
P. Ballirano ◽  
...  
Keyword(s):  
Isothermal Treatment ◽  
X Ray Diffraction ◽  
Ferrous Chloride ◽  
Scanning Calorimetry ◽  
Direct Transformation ◽  
X Ray ◽  
Transmission Electron ◽  
Xrd Techniques ◽  
Kinetics Of

Homogeneous maghemite (γ–Fe2O3) nanoparticles with an average crystal size around 5 nm were synthesized by successive hydrolysis, oxidation, and dehydration of tetrapyridino-ferrous chloride. Morphological, thermal, and structural properties were investigated by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and x-ray diffraction (XRD) techniques. Rietveld refinement indicated a cubic cell. The superstructure reflections, related to the ordering of cation lattice vacancies, were not detected in the diffraction pattern. Kinetics of the solid-state phase transition of nanocrystalline maghemite to hematite (α–Fe2O3), investigated by energy dispersive x-ray diffraction (EDXRD), indicates that direct transformation from nanocrystalline maghemite to microcrystalline hematite takes place during isothermal treatment at 385 °C. This temperature is lower than that observed both for microcrystalline maghemite and for nanocrystalline maghemite supported on silica.

Microstructures of Ultrathin Films of Sputtered PbTiO3

1994 ◽  
Vol 361 ◽  
Author(s):  
Kiyotaka Wasa ◽  
T. Satoh ◽  
K. Tab Ata ◽  
H. Adachi ◽  
Y. Ichikawa ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Ultrathin Films ◽  
Crystal Orientation ◽  
Smooth Surface ◽  
Three Dimensional ◽  
Rf Magnetron Sputtering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dimensional Crystal

ABSTRACTUltrathin films of perovskite PbTiO3, 10–100nm thick, were epitaxially grown on miscut (001)SrTiO3 substrate by rf-magnetron sputtering at 600°C. The electron microscope and high resolution x-ray diffraction analysis suggested the evidence of epitaxial growth of (001)PbTiO3/(001)SrTiO3 with three dimensional crystal orientation. The stoichiometric film shows extremely smooth surface with the surface roughness less than 3nm. Deposition on a miscut substrate under stoichiometric conditions is essential to make continuous thin films of single crystal perovskite PbTiO3.

scholarly journals Synthesis of NiW Supported on an Al-Modified Cubic Ia3d Mesoporous KIT-5 Catalyst and Its Hydrodenitrogenation Performance of Quinoline

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1183
Author(s):  
Xing Liu ◽  
Shaoqing Guo ◽  
Xin Li ◽  
Lijing Yuan ◽  
Hongyu Dong ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Fourier Transform ◽  
Three Dimensional ◽  
Fourier Transform Infrared ◽  
Photoelectron Spectra ◽  
Sulfide Catalysts ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Large Pore Size

Pure KIT-5 and a series of Al-KT-X materials modified by different amounts of aluminum were synthesized by a direct hydrothermal method and acted as supports for the catalysts of a quinoline hydrodenitrification reaction with the NiW active phases supported. The results of X-ray diffraction (XRD), N2 isotherm absorption-desorption, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) for the supports indicated that Al species were embedded into the framework of the KIT-5 materials with a large pore size, pore volume, and specific surface area. The Pyridine-Fourier transform infrared spectroscopy (Py-IR) result of the catalysts demonstrated that the addition of aluminum atoms enhanced the acidity of the catalysts. The results of the high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectra (XPS) characterizations for the sulfide catalysts indicated that the embedded Al species could facilitate the dispersion of active metals and the formation of the active phases. Among all the catalysts, NiW/Al-KT-40 showed the maximal hydrodenitrogenation conversion (HDNC) due to its open three-dimensional pore structure, appropriate acidity, and good dispersion of active metals.

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