Morphology and Pore Structure of Rare Earth Oxides

1991 ◽  
Vol 44 (5) ◽  
pp. 645 ◽  
Author(s):  
LA Bruce ◽  
M Hoang ◽  
S Hardin ◽  
TW Turney
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Rare Earth ◽  
Pore Structure ◽  
Rare Earth Oxides ◽  
Thin Sheets ◽  
Adsorption Characteristics ◽  
Transmission Electron ◽  
Adsorption Hysteresis

The morphology observed by transmission electron microscopy of rare earth oxides, prepared by two different routes, has been related to adsorption characteristics for nitrogen at 77 K. The most common morphology was that of thin sheets, then small equiaxed particles, and, more rarely, rod-like particles. The presence of small equiaxed particles was found to be a prerequisite for adsorption hysteresis. Evaluation of linear 't' plots indicated freedom from micropores in all samples, but positive deviations in the presence of sheet morphology at high relative pressures left open the possibility of wedge-like pores in these samples.

Calculation and Analysis of Multifractal Spectrum of Sinter Surface

2013 ◽  
Vol 750-752 ◽  
pp. 2267-2270
Author(s):  
Zhi Min Cui ◽  
Rong Li Sang ◽  
Yuan Liang Li ◽  
Qing Jun Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Pore Structure ◽  
Multifractal Spectrum ◽  
Transmission Electron Microscopy Image ◽  
Structure Change ◽  
Electron Microscopy Image ◽  
Transmission Electron ◽  
Microscopy Image ◽  
Fractal Spectrum

Multifractal spectrums of sinter with different alkalinity were analyzed by multifractal software. The results show that sinter pore structure change from uniform to non-uniform with the improvement of alkalinity, Δα increases from 0.53 to 0.55. The structure of sinter pore is mainly microscopic by competition between macropores and micropores, Δf changes from 0.14 to-0.44. The distribution of sinter pores is quantitatively characterized by multi-fractal spectrum, which is consistent with transmission electron microscopy image.

Study of Au-CeO2 Nano-particles using analytical Transmission Electron Microscopy

2007 ◽  
Vol 1 (1) ◽  
Author(s):  
P. Gu ◽  
G. Yang ◽  
R.F. Klie
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Particle Size ◽  
Rare Earth ◽  
Lattice Parameter ◽  
Nano Particles ◽  
Rare Earth Doping ◽  
Analytical Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Shift Reaction

Cerium oxide doped with various rare earth metals is often used as a support for nano-sized gold particles, and demonstrates to be a promising catalyst for the water gas shift reaction at low temperatures. Many factors are hypothesized to affect the activity of this heterogeneous catalyst, including its loading with gold, the rare-earth dopant, the support and Au particle size, and leaching of the sample. In this study, we examined several Au/CeO2-based catalyst samples, including 2.4% Au/(Ce,Gd)O2, 1.8% Au/(Ce,La)O2 leached, 0.5% Au/(Ce,Gd)O2 leached, and 0.75% Au/CeO2 utilizing analytical transmission electron microscopy. The effects of Au and rare-earth doping on the ceria lattice parameter were investigated, and it was determined that there are no significant variations in the particle's structure or lattice-spacing. Furthermore, the particle sizes of each of the four samples were investigated concluding that although the 1.8% Au/(Ce,La)O2 leached sample has a slightly larger particle size, and the 2.4% Au/(Ce,Gd)O2 sample has a slightly smaller particle size, the differentiation is not adequate to be accountable for the radical distinction in catalytic activity.

Nonepitaxial heterogeneous nucleation of α-sialon in the Ca-doped system

2001 ◽  
Vol 16 (2) ◽  
pp. 578-582 ◽  
Author(s):  
Ya-Wen Li ◽  
Pei-Ling Wang ◽  
Wei-Wu Chen ◽  
Jing-Wei Feng ◽  
Yi-Bing Cheng ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Rare Earth ◽  
Orientation Relationship ◽  
Heterogeneous Nucleation ◽  
Crystallographic Orientation ◽  
Probable Mechanism ◽  
Transmission Electron ◽  
Low X ◽  
Rare Earth Doped

Ca-α-sialon compacts pressureless-sintered to intermediate temperatures, which consisted of both α-sialon and unreacted α–Si3N4 grains, were investigated with transmission electron microscopy for an overall composition Ca1.8Si6.6Al5.4O1.8N14.2. Special attention was paid to identification of the possible crystallographic orientation between a-sialon and the α–Si3N4 particles. In contrast to the frequently occurring heteroepitaxial nucleation of α-sialon in rare-earth-doped samples with low x values, this study showed that most of the newly formed α-sialon grains had no epitaxial orientation relationship with the α–Si3N4 particles, suggesting nonepitaxial heterogeneous nucleation to be a more probable mechanism for the Ca–α-sialon phase with high Ca concentrations.

Fine structure of Classopollis exines

1986 ◽  
Vol 64 (12) ◽  
pp. 3059-3074 ◽  
Author(s):  
John R. Rowley ◽  
Satish K. Srivastava
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Upper Jurassic ◽  
Thin Sheets ◽  
Serial Sections ◽  
Thin Sections ◽  
Band Area ◽  
Transmission Electron ◽  
Oxidative Etching

Serial sections for light microscopy or transmission electron microscopy of two Classopollis pollen tetrads show that the exine structure, except for the nexine, has radially arranged rodlike units interwoven with transverse subunits. The nexine consists of strands or thin sheets except in the equatorial infratectal striate band area, where it is up to ca. 1 μm thick. Nexine is absent in the areas of the distal cryptopore and the subequatorial circumpolar infratectal canal. It is very thin or absent in the tetrad scar. Native contrast and reactivity to stain disappeared on immersion of thin sections in 1 M NaOH or HCl or in water. Reactivity to stains was regained after oxidizing the sections in KMnO4. Reactivity to stains appears to be dependent upon non-sporopollenin molecules embedded within exines. The above immersions remove stain reactive sites. Oxidative etching of sporopollenin exposes new sites. The specimens of Classopollis classoides Pflug studied and illustrated were picked from an Upper Jurassic sample (CRC 31519-2) collected at Osmington Mills locality, Dorset, England.

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