A Fundamental Study on the Chemical Stability of La1−xSrxCo0.2Fe0.8O3−δ Cathodes for Intermediate Temperature Solid Oxide Fuel Cells

2017 ◽  
Vol 14 (3) ◽  
Author(s):  
Yufeng Qiu ◽  
Jian Pu ◽  
Jian Li ◽  
Yihui Liu ◽  
Bin Hua
Keyword(s):  
Electron Microscopy ◽  
Chemical Stability ◽  
Photoelectron Spectroscopy ◽  
Surface Segregation ◽  
Treatment Time ◽  
Driving Forces ◽  
Secondary Phase ◽  
Fundamental Study ◽  
Transmission Electron ◽  
Before And After

The chemical stability of La1−xSrxCo0.2Fe0.8O3−δ (x = 0, 0.4, 0.6, and 1) oxides before and after annealing at 750 °C in air is investigated by field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and environmental transmission electron microscopy (TEM). Results indicate that Sr surface segregation has initially occurred at the sintering stage, and then, the secondary-phase particles are formed with increasing the heat-treatment time at 750 °C in air. Increasing Sr content accelerates Sr segregation on the surface, because of two driving forces including interaction forces in the crystal lattice and thermal activation. AES and XPS results reveal that Sr and Co segregations toward the surface have great contributions to the chemical instability of La1−xSrxCo1−yFeyO3−δ (LSCF) during annealing.

Surface Alteration of Nd-Bearing Zirconolite Following Hydrothermal Treatment

2000 ◽  
Vol 663 ◽  
Author(s):  
Zhaoming Zhang ◽  
Eric R. Vance ◽  
Mark G. Blackford
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Treatment ◽  
Photoelectron Spectroscopy ◽  
Deionized Water ◽  
X Ray ◽  
Transmission Electron ◽  
Dissolution Tests ◽  
Before And After ◽  
Surface Alteration ◽  
Durability Testing

ABSTRACTStatic dissolution tests on Nd-bearing zirconolite were conducted in deionized water at 150°C for up to 6 months. Surfaces, both before and after aqueous dissolutions, were examined using X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). Individual submicron-sized crystals wereobserved only on some zirconolite grains after hydrothermal treatment for one week, and were identified as brookite (possibly plus anatase) by Transmission Electron Microscopy (TEM). The number of secondary crystals present on the zirconolite surface was, however, reduced significantly after 6 months of durability testing. The results of electron microscopy studies are consistent with those obtained from XPS in that the average Ca and Ti concentrations of the top surface layer (< 5 nm) decreased slightly with respect to Zr, while the average Al concentration increased after durability testing.

scholarly journals Synthesis of Chromium Carbide Nanopowders by Microwave Heating and Their Composition and Microstructure Change under Gamma Ray Irradiation

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 16 ◽  
Author(s):  
Kai Jin ◽  
Yuanbo Jia ◽  
Zhiwei Zhao ◽  
Weiqiang Song ◽  
Shun Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Microwave Heating ◽  
Chromium Carbide ◽  
Photoelectron Spectroscopy ◽  
Gamma Ray ◽  
X Ray ◽  
Transmission Electron ◽  
Before And After ◽  
Gamma Ray Irradiation

Chromium carbide nanopowders were synthesized by mechanical alloying-assisted microwave heating. The effect of gamma irradiation on phase composition and microstructure of chromium carbide nanopowders synthesized by the microwave heating method was analyzed. The samples were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The results showed that well-dispersed chromium carbide nanopowders can be synthesized by maintaining the temperature at 1000 °C for 1 h. Gamma ray irradiation had an important effect on the microstructure of chromium carbide nanopowders. The interplanar spacings of chromium carbide (110) crystal faces before and after gamma ray irradiation were 0.3725 nm and 0.3824 nm, respectively. The crystal structure of chromium carbide was changed by gamma ray irradiation. Gamma ray irradiation can also increase the binding energy of chromium carbide, which is beneficial to improve the thermal stability and mechanical properties of chromium carbide at high temperature.

Low Temperature - High Pressure Oxidation of 3C-SiC

1994 ◽  
Vol 357 ◽  
Author(s):  
Christine Caragianis-Broadbridge ◽  
Barbara L. Walden ◽  
Juliana Blaser ◽  
Cleva Ow Yang ◽  
David C. Paine
Keyword(s):  
Electron Microscopy ◽  
Low Temperature ◽  
Single Crystal ◽  
Photoelectron Spectroscopy ◽  
Pressure Oxidation ◽  
Planar Defects ◽  
Transmission Electron ◽  
Before And After ◽  
Crystal Films ◽  
Film Microstructure

AbstractSingle crystal films of n-type 3C-SiC were hydrothermally processed at pressures ranging from 10 to 70 MPa at 550°C. To study the effects of initial thin film microstructure on hydrothermal processing, two different samples of CVD-grown SiC were studied: one, 200 nm thick, contained low angle boundaries and a high density of planar defects; the other, 3500 nm thick, was planar and contained relatively few defects. Raman Spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to study the chemistry and microstructure of the SiC material both before and after hydrothermal treatment. This study reveals that low temperature (T=550°C) oxidation of single crystal epitaxial SiC is possible but that the resulting oxide film microstructure is strongly dependent on the initial film microstructure and oxidation is greatly enhanced along low angle grain boundaries and on planar defects.

Characterization of BN Rich Layer on Ammonia Treated Nextel™312 Fibers

1994 ◽  
Vol 365 ◽  
Author(s):  
N.R. Khasgiwale ◽  
E.P. Butler ◽  
L. Tsakalakos ◽  
D.A. Hensley ◽  
W.R. Cannon ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Layer Thickness ◽  
Photoelectron Spectroscopy ◽  
Fiber Surface ◽  
Ammonia Treatment ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Before And After ◽  
High Resolution Tem

ABSTRACTA BN rich layer grown on Nextel™312 fibers by appropriate ammonia treatments was evaluated using various complimentary techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM)/ Parallel Electron Energy Loss Spectroscopy (PEELS in TEM). Three different ammonia treatments were studied. Ammonia treatment resulted in crystallization of the Nextel™312 fiber. The BN rich surface layer formed due to ammonia treatment was clearly detected in XPS and PEELS both before and after oxidation. The layer thickness was estimated to be between 5–10 nm. The layer was stable after oxidation treatment at 600°C for 100 hours. High resolution TEM observations of the fiber surface revealed a variable BN rich layer thickness. Patches of turbostratic BN were observed under certain conditions, however mostly the layer appeared to be amorphous.

Observation of solid-state reaction between a thin yttria film and a (0001) α-alumina substrate

1994 ◽  
Vol 52 ◽  
pp. 644-645
Author(s):  
J. R. Heffelfinger ◽  
C. B. Carter
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Solid State Reaction ◽  
Yttrium Aluminum Garnet ◽  
Secondary Phase ◽  
Ceramic Composites ◽  
Alumina Substrate ◽  
Transmission Electron ◽  
Alumina Fibers ◽  
Optical Applications

Transmission-electron microscopy (TEM), scanning-electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) were used to investigate the solid-state reaction between a thin yttria film and a (0001) α-alumina substrate. Systems containing Y2O3 (yttria) and Al2O3 (alumina) are seen in many technologically relevant applications. For example, yttria is being explored as a coating material for alumina fibers for metal-ceramic composites. The coating serves as a diffusion barrier and protects the alumina fiber from reacting with the metal matrix. With sufficient time and temperature, yttria in contact with alumina will react to form one or a combination of phases shown by the phase diagram in Figure l. Of the reaction phases, yttrium aluminum garnet (YAG) is used as a material for lasers and other optical applications. In a different application, YAG is formed as a secondary phase in the sintering of AIN. Yttria is added to AIN as a sintering aid and acts as an oxygen getter by reacting with the alumina in AIN to form YAG.

Investigation of Polyoxometalate-(Poly)pyrrole Heterogeneous Nanostructures as Cathodes for Rechargeable Magnesium-Ion Batteries

2018 ◽  
Author(s):  
Hakeem K. Henry ◽  
Sang Bok Lee
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Active Material ◽  
Conductive Polymer ◽  
Current Collector ◽  
Constant Current ◽  
Anodized Aluminum ◽  
Transmission Electron ◽  
Pyrrole Monomer

The PMo<sub>12</sub>-PPy heterogeneous cathode was synthesized electrochemically. In doing so, the PMo<sub>12</sub> redox-active material was impregnated throughout the conductive polymer matrix of the poly(pyrrole) nanowires. All chemicals and reagents used were purchased from Sigma-Aldrich. Anodized aluminum oxide (AAO) purchased from Whatman served as the porous hard template for nanowire deposition. A thin layer of gold of approximately 200nm was sputtered onto the disordered side of the AAO membrane to serve as the current collector. Copper tape was connected to the sputtered gold for contact and the device was sealed in parafilm with heat with an exposed area of 0.32 cm<sup>2</sup> to serve as the electroactive area for deposition. All electrochemical synthesis and experiments were conducted using a Bio-Logic MPG2 potentiostat. The deposition was carried out using a 3-electrode beaker cell setup with a solution of acetonitrile containing 5mM and 14mM of the phosphomolybdic acid and pyrrole monomer, respectively. The synthesis was achieved using chronoamperometry to apply a constant voltage of 0.8V vs. Ag/AgCl (BASi) to oxidatively polymerize the pyrrole monomer to poly(pyrrole). To prevent the POM from chemically polymerizing the pyrrole, an injection method was used in which the pyrrole monomer was added to the POM solution only after the deposition voltage had already been applied. The deposition was well controlled by limiting the amount of charge transferred to 300mC. Following deposition, the AAO template was removed by soaking in 3M sodium hydroxide (NaOH) for 20 minutes and rinsed several times with water. After synthesis, all cathodes underwent electrochemical testing to determine their performance using cyclic voltammetry and constant current charge-discharge cycling in 0.1 M Mg(ClO<sub>4</sub>)<sub>2</sub>/PC electrolyte. The cathodes were further characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and x-ray photoelectron spectroscopy (XPS).

An Overview of Cu Wire Intermetallic Compound Formation and a Corrosion Failure Mechanism

2012 ◽  
Author(s):  
Dongmei Meng ◽  
Laura Buck ◽  
James Cargo
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Corrosion Mechanism ◽  
Fundamental Study ◽  
Corrosion Failure ◽  
Transmission Electron ◽  
Intermetallic Compound Formation ◽  
Scanning Transmission ◽  
Low K

Abstract Cu needs a higher level of ultrasound combined with bonding force to be bonded to the Al pad properly, not just because Cu is harder than Au, but it is also harder to initiate intermetallic compounds (IMC) formation during bonding. This increases the chances of damaging the metal/low k stack under the bondpad. This paper presents a fundamental study of IMC as well as one example of a failure mode of Cu/Al bonded devices, all based on detailed analysis using scanning electron microscopy, scanning transmission electron microscopy, energy dispersive spectrometers, and transmission electron microscopy. It presents a case study showing a corrosion mechanism of Cu/Al ballbond after 168hr UHAST stress. It is observed that all Cu9Al4 was consumed, while very little copper aluminide remained after 168 hours of UHAST stressing.

scholarly journals Synthesis of Ce1−xPdxO2−δ Solid Solution in Molten Nitrate

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 640
Author(s):  
Hideaki Sasaki ◽  
Keisuke Sakamoto ◽  
Masami Mori ◽  
Tatsuaki Sakamoto
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Solid Solutions ◽  
Photoelectron Spectroscopy ◽  
Synthesis Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Ionic States

CeO2-based solid solutions in which Pd partially substitutes for Ce attract considerable attention, owing to their high catalytic performances. In this study, the solid solution (Ce1−xPdxO2−δ) with a high Pd content (x ~ 0.2) was synthesized through co-precipitation under oxidative conditions using molten nitrate, and its structure and thermal decomposition were examined. The characteristics of the solid solution, such as the change in a lattice constant, inhibition of sintering, and ionic states, were examined using X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM−EDS), transmission electron microscopy (TEM)−EDS, and X-ray photoelectron spectroscopy (XPS). The synthesis method proposed in this study appears suitable for the easy preparation of CeO2 solid solutions with a high Pd content.

Characterization of columns grown during KrF laser micromachining of Al2O3–TiC ceramics

2003 ◽  
Vol 18 (5) ◽  
pp. 1123-1130 ◽  
Author(s):  
V. Oliveira ◽  
R. Vilar
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Laser Pulses ◽  
Formation Mechanisms ◽  
X Ray ◽  
Reducing Conditions ◽  
Transmission Electron ◽  
Column Formation ◽  
Krf Laser

This paper aims to contribute to the understanding of column formation mechanisms in Al2O3–TiC ceramics micromachined using excimer lasers. Chemical and structural characterization of columns grown in Al2O3–TiC composite processed with 200 KrF laser pulses at 10 J/cm2 was carried out by scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction analysis. Fully developed columns consist of a core of unprocessed material surrounded by an outer layer of Al2TiO5, formed in oxidizing conditions, and an inner layer, formed in reducing conditions, composed of TiC and Al3Ti or an AlTi solid solution. Possible mechanisms of column formation are discussed.

scholarly journals Green Synthesis of Feather-Shaped MoS2/CdS Photocatalyst for Effective Hydrogen Production

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Yang Liu ◽  
Hongtao Yu ◽  
Xie Quan ◽  
Shuo Chen
Keyword(s):  
Electron Microscopy ◽  
Hydrogen Production ◽  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance ◽  
Sulfur Source ◽  
X Ray ◽  
Transmission Electron ◽  
Microscopy Images ◽  
Effective Hydrogen ◽  
Better Than

MoS2/CdS photocatalyst was fabricated by a hydrothermal method for H2production under visible light. This method used low toxic thiourea as a sulfur source and was carried out at 200°C. Thus, it was better than the traditional methods, which are based on an annealing process at relatively high temperature (above 400°C) using toxic H2S as reducing agent. Scanning electron microscopy and transmission electron microscopy images showed that the morphologies of MoS2/CdS samples were feather shaped and MoS2layer was on the surface of CdS. The X-ray photoelectron spectroscopy testified that the sample was composed of stoichiometric MoS2and CdS. The UV-vis diffuse reflectance spectra displayed that the loading of MoS2can enhance the optical absorption of MoS2/CdS. The photocatalytic activity of MoS2/CdS was evaluated by producing hydrogen. The hydrogen production rate on MoS2/CdS reached 192 μmol·h−1. This performance was stable during three repeated photocatalytic processes.

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