SYNTHESIS AND MORPHOLOGICAL CONTROL OF MONODISPERSED MICROSIZED CERIA PARTICLES

2010 ◽  
Vol 17 (02) ◽  
pp. 147-152 ◽  
Author(s):  
S. YIN ◽  
Y. MINAMIDATE ◽  
T. SATO
Keyword(s):  
Particle Size ◽  
Cerium Oxide ◽  
Room Temperature ◽  
Aging Treatment ◽  
Precipitation Process ◽  
Homogeneous Precipitation ◽  
Morphological Control ◽  
Oxide Particles ◽  
Cerium Carbonate ◽  
Carbonate Precursor

The morphological control of crystalline cerium oxide particles was realized by homogeneous precipitation process followed by calcination in air at 400°C. The effects of room temperature pre-aging time on the morphologies of final products were investigated. Monodispersed rod-like cerium carbonate precursor was produced at 70°C for 2 h using the solution without pre-aging treatment. In contrast, monodispersed spherical precursor and plate-like precursor were obtained under the same conditions after pre-aging the solution at 25°C for 72 and 144 h, respectively. Ceria particles with similar morphologies and particle size to those of carbonate precursor could be obtained after calcination in air at 400°C. The monodispersed spherical, rod-like, and plate-like cerium oxide particles were successfully synthesized.

scholarly journals Modelling of Precipitation Hardening in Casting Aluminium Alloys

2009 ◽  
Vol 618-619 ◽  
pp. 203-206 ◽  
Author(s):  
Linda Wu ◽  
W. George Ferguson
Keyword(s):  
Particle Size ◽  
Aluminium Alloys ◽  
Room Temperature ◽  
Precipitation Hardening ◽  
Numerical Approach ◽  
Precipitation Process ◽  
Dislocation Theory ◽  
Strength Model ◽  
Aging Hardening ◽  
Nucleation Growth

Precipitation hardening, or aging hardening, is one of the most widely adopted techniques for strengthening of aluminium alloys. During the precipitation process, three major mechanisms are involved: i.e. nucleation, growth and coarsening. Kampmann and Wagner have developed a powerful and flexible numerical approach (KWN model) for dealing with concomitant nucleation, growth and coarsening and thus capable of predicting the full evolution of the particle size distribution. KWN model has been successfully applied to a number of aluminium alloy systems, such as 2xxx, 6xxx and 7xxx. However, most of these modelling works were focused on the wrought aluminium alloys, few had applied to the casting aluminium alloys. In the present modelling work, the microstructure evolution is modeled based on the KWN model and then a strength model based on the well established dislocation theory is used to evaluate the resulting change in hardness or yield strength at room temperature. Then the modelling is applied to casting aluminium alloys A356 and A357. And the modelling results are validated by comparing with own experimental results and the results obtained from the open literature.

Synthesis of Monodispersed Plate-Like CeO2 Particles by Precipitation Process in Sodium Hydrogen Carbonate Solution

2010 ◽  
Vol 63 ◽  
pp. 30-35 ◽  
Author(s):  
Shu Yin ◽  
Yoshihiro Minamidate ◽  
Tsugio Sato
Keyword(s):  
Particle Size ◽  
Sodium Hydrogen Carbonate ◽  
Solution Process ◽  
Precipitation Process ◽  
High Concentration ◽  
Catalytic Activities ◽  
Sodium Hydrogen ◽  
Hydrogen Carbonate ◽  
Shielding Properties ◽  
Cerium Carbonate

Monodispersed plate-like CeO2 particles were successfully synthesized by a mild solution process followed by calcination in air at 400oC. During the solution processing, monodispersed orthorhombic single-crystal of plate-like Ce2(CO3)3.8H2O was obtained by using Ce(NO3)3.6H2O as cerium source, and NaHCO3 aqueous solution as precipitation reagent and carbon source. The concentration of NaHCO3 solution affects the morphologies and particle size of the cerium carbonate compounds. High concentration of NaHCO3 led to a decrease in the particle size of Ce2(CO3)3.8H2O effectively. The CeO2 particles synthesized by the decomposition of carbonate precursors possessed similar morphologies and slightly smaller particle size. The plate-like ceria particles possessed good UV-shielding properties and low oxidation catalytic activities, indicating the potential application as cosmetics materials

Desulfurization Performance with ZnO Nanocrystalline to Eliminate H2S at Room Temperature

2007 ◽  
Vol 121-123 ◽  
pp. 1325-1328
Author(s):  
Chun Hong Shao ◽  
A.X. Jiang ◽  
F. Li ◽  
B. Yan ◽  
X.K. Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Precipitation Process ◽  
Homogeneous Precipitation ◽  
Activity Time ◽  
X Ray ◽  
Transmission Electron ◽  
Zno Powders

Nanocrystalline ZnO powders, whose crystalline sizes were 14.3, 21.2, 24.1, and 35.3 nm, respectively, were prepared by homogeneous precipitation process. Nanocrystalline ZnO powders were characterized with powder X-ray diffractometer (XRD), transmission electron microscopy (TEM) and X ray photoelectron spectroscopy (XPS). The performance of desulfurization of H2S at room temperature was investigated. Results demonstrated that the smaller the size of nanocrystalline ZnO, the darker the color of desulfurization products would be, which was more similar to the characteristics of multi-sulfide results, indicating that the mechanism of desulfurization of nanocrystalline ZnO was not the same as that of the analytical pure ZnO. Nanocrystalline ZnO improved the performance of desulfurization of H2S at room temperature, and the activity time of nanocrystalline ZnO (14.3 nm) for the desulfurization was 34 times that of analytical pure ZnO at absence of oxygen. When the oxygen was present in reaction, the accuracy of desulfurization was improved, in which H2S was prone to be oxidized into element S, and SO2 was not detected at outlet of the reactor.

Luminescence Properties of Europium-Doped Yttrium Oxides Derived from Their Dodecylsulfate-Templated Mesostructure and Nanotube Forms

2003 ◽  
Vol 775 ◽  
Author(s):  
Tsuyoshi Kijima ◽  
Kenichi Iwanaga ◽  
Tomomi Hamasuna ◽  
Shinji Mohri ◽  
Mitsunori Yada ◽  
...  
Keyword(s):  
Room Temperature ◽  
Broad Band ◽  
Concentration Quenching ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Bulk Materials ◽  
Main Band ◽  
Homogeneous Precipitation Method ◽  
Order Of Magnitude ◽  
Weak Luminescence

AbstractEuropium-doped hexagonal-mesostructured and nanotubular yttrium oxides templated by dodecylsulfate species as well as surfactant free bulk oxides were synthesized by the homogeneous precipitation method. All the as grown nanostructured or bulk materials with amorphous or poorly crystalline frameworks showed weak luminescence bands at room temperature. On calcination at 1000°C these materials were converted into highly crystalline yttrium oxides, resulting in a total increase in intensity of all the bands by one order of magnitude. In the hexagonal-mesostructured system, the main band due to the 5D0-7F2 transition for the calcined phases showed a sharp but asymmetrical multiplet splitting indicating multiple Eu sites. Concentration quenching was found at a Eu content of 3 mol% or above for these phases. In contrast, the main emission for the calcined solids in the nanotubular system occurred as poorly resolved broad band and the intensity of the main band at higher Eu content was significantly enhanced compared with those for the other two systems.

Study of the microstructure and particles of vanadium (III) oxide, vanadium (V) oxide and lithium aluminate powders

2020 ◽  
Vol 86 (1) ◽  
pp. 32-37
Author(s):  
Valeria A. Brodskaya ◽  
Oksana A. Molkova ◽  
Kira B. Zhogova ◽  
Inga V. Astakhova
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Vanadium Oxide ◽  
Size Distribution ◽  
Microstructural Analysis ◽  
Coherent Scattering ◽  
Powder Materials ◽  
Lithium Aluminate ◽  
Range Limit ◽  
Oxide Particles

Powder materials are widely used in the manufacture of electrochemical elements of thermal chemical sources of current. Electrochemical behavior of the powders depends on the shape and size of their particles. The results of the study of the microstructure and particles of the powders of vanadium (III), (V) oxides and lithium aluminate obtained by transmission electron and atomic force microscopy, X-ray diffraction and gas adsorption analyses are presented. It is found that the sizes of vanadium (III) and vanadium (V) oxide particles range within 70 – 600 and 40 – 350 nm, respectively. The size of the coherent-scattering regions of the vanadium oxide particles lies in the lower range limit which can be attributed to small size of the structural elements (crystallites). An average volumetric-surface diameter calculated on the basis of the surface specific area is close to the upper range limit which can be explained by the partial agglomeration of the powder particles. Unlike the vanadium oxide particles, the range of the particle size distribution of the lithium aluminate powder is narrower — 50 – 110 nm. The values of crystallite sizes are close to the maximum of the particle size distribution. Microstructural analysis showed that the particles in the samples of vanadium oxides have a rounded (V2O3) or elongated (V2O5) shape; whereas the particles of lithium aluminate powder exhibit lamellar structure. At the same time, for different batches of the same material, the particle size distribution is similar, which indicates the reproducibility of the technologies for their manufacture. The data obtained can be used to control the constancy of the particle size distribution of powder materials.

Martensite decomposition during post-heat treatments and the aging response of near-α Ti–6Al–2Sn–4Zr–2Mo (Ti-6242) titanium alloy processed by selective laser melting (SLM)

2021 ◽  
pp. 2050018
Author(s):  
Haiyang Fan ◽  
Yahui Liu ◽  
Shoufeng Yang
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Selective Laser Melting ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Aging Treatment ◽  
Water Quenching ◽  
Laser Melting ◽  
Aging Response

Ti–6Al–2Sn–4Zr–2Mo (Ti-6242), a near-[Formula: see text] titanium alloy explicitly designed for high-temperature applications, consists of a martensitic structure after selective laser melting (SLM). However, martensite is thermally unstable and thus adverse to the long-term service at high temperatures. Hence, understanding martensite decomposition is a high priority for seeking post-heat treatment for SLMed Ti-6242. Besides, compared to the room-temperature titanium alloys like Ti–6Al–4V, aging treatment is indispensable to high-temperature near-[Formula: see text] titanium alloys so that their microstructures and mechanical properties are pre-stabilized before working at elevated temperatures. Therefore, the aging response of the material is another concern of this study. To elaborate the two concerns, SLMed Ti-6242 was first isothermally annealed at 650[Formula: see text]C and then water-quenched to room temperature, followed by standard aging at 595[Formula: see text]C. The microstructure analysis revealed a temperature-dependent martensite decomposition, which proceeded sluggishly at [Formula: see text]C despite a long duration but rapidly transformed into lamellar [Formula: see text] above the martensite transition zone (770[Formula: see text]C). As heating to [Formula: see text]C), it produced a coarse microstructure containing new martensites formed in water quenching. The subsequent mechanical testing indicated that SLM-built Ti-6242 is excellent in terms of both room- and high-temperature tensile properties, with around 1400 MPa (UTS)[Formula: see text]5% elongation and 1150 MPa (UTS)[Formula: see text]10% elongation, respectively. However, the combination of water quenching and aging embrittled the as-built material severely.

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