A microscopic marker experiment study on high temperature oxidation of Ni-Al alloy

1986 ◽  
Vol 44 ◽  
pp. 514-515
Author(s):  
Shou-kong Fan
Keyword(s):  
Transport Mechanism ◽  
High Temperature Oxidation ◽  
Transverse Section ◽  
Al Alloy ◽  
Metal Interface ◽  
Electron Microscopic ◽  
Temperature Oxidation ◽  
Analytical Electron ◽  
Microscopic Studies ◽  
First Time

Transmission and analytical electron microscopic studies of scale microstructures and microscopic marker experiments have been carried out in order to determine the transport mechanism in the oxidation of Ni-Al alloy. According to the classical theory, the oxidation of nickel takes place by transport of Ni cations across the scale forming new oxide at the scale/gas interface. Any markers deposited on the Ni surface are expected to remain at the scale/metal interface after oxidation. This investigation using TEM transverse section techniques and deposited microscopic markers shows a different result,which indicates that a considerable amount of oxygen was transported inward. This is the first time that such fine-scale markers have been coupled with high resolution characterization instruments such as TEM/STEM to provide detailed information about evolution of oxide scale microstructure.

scholarly journals High-Temperature Oxidation Properties and Microstructural Evolution of Nanostructure Fe-Cr-Al ODS Alloys

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 526
Author(s):  
Zhengyuan Li ◽  
Lijia Chen ◽  
Haoyu Zhang ◽  
Siyu Liu
Keyword(s):  
High Temperature ◽  
Oxide Layer ◽  
Microstructural Evolution ◽  
High Temperature Oxidation ◽  
Oxide Dispersion Strengthened ◽  
Al Alloy ◽  
Temperature Oxidation ◽  
X Ray ◽  
Plasma Sintering ◽  
Ods Alloys

The oxidation behavior and microstructural evolution of the nanostructure of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys prepared by spark plasma sintering were investigated by high-temperature oxidation experiments in air at 1200 °C for 100 h. The formation of Al2O3 scale was observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) line scans. The oxidation rate of Fe-Cr-Al ODS alloys is lower than that of conventional Fe-Cr-Al alloys, and the oxide layer formed on the Fe-Cr-Al alloy appeared loose and cracked, whereas the oxide layer formed on the Fe-Cr-Al ODS alloys was adherent and flat. This is due to the high density of dispersed nano-oxides hindering the diffusion of Al element and the formation of vacancies caused by them. In addition, the nano-oxides could also adhere to the oxide layer. Besides, the microstructure of the Fe-Cr-Al ODS alloy had excellent stability during high-temperature oxidation.

High-resolution and Analytical Electron Microscopic Studies of New Crystals Induced by a Bioactive Ceramic (Diopside)

1995 ◽  
Vol 74 (11) ◽  
pp. 1756-1763 ◽  
Author(s):  
Y. Miake ◽  
T. Yanagisawa ◽  
Y. Yajima ◽  
H. Noma ◽  
N. Yasui ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Microscopic ◽  
Analytical Electron ◽  
Microscopic Studies ◽  
Bioactive Ceramic

ChemInform Abstract: MOESSBAUER AND ANALYTICAL ELECTRON MICROSCOPIC STUDIES OF AN UNUSUAL ORTHOSILICATE- CHLORITOID

1978 ◽  
Vol 9 (8) ◽  
Author(s):  
M. J. TRICKER ◽  
D. A. JEFFERSON ◽  
J. M. THOMAS ◽  
P. G. MANNING ◽  
C. J. ELLIOTT
Keyword(s):  
Electron Microscopic ◽  
Analytical Electron ◽  
Microscopic Studies

Optical Properties and New Functionality of Nanocrystalline CuCl and Ge

1992 ◽  
Vol 283 ◽  
Author(s):  
Yasuaki Masumoto
Keyword(s):  
Optical Transition ◽  
Optical Gain ◽  
Glassy Matrix ◽  
Bulk Crystals ◽  
Electron Microscopic ◽  
Visible Photoluminescence ◽  
Resolution Electron ◽  
Microscopic Studies ◽  
Direct Optical Transition ◽  
First Time

ABSTRACTLasing of nanocrystalline CuCl embedded in a NaCl single crystal wasobserved for the first time. Lasing takes place at 77 K in nanocrystalline CuCl sandwiched between dielectric mirrors under the pulsed ultraviolet laser excitation. The lasing transition is that from bi-exciton to exciton. The lasing is observed up to 108 K. The optical gain of nanocrystalline CuCl is almost the same as that of bulk crystals in spite of the low concentration of CuCl in the NaCl matrix.The origin of visible photoluminescence of nanocrystalline Ge in SiO2 glassy matrix has been studied. Spectroscopic analyses of nanocrystalline Ge indicate that the room-temperature photoluminescence comes from nanocrystalline Ge of diameter of 4 nm or less. High-resolution electron microscopic studies imply that the structure of nanocrystalline Ge of diameter ≤ 4 nm differs from the diamond structure. These data suggest that new nanostructure crystalline Ge having a character of direct optical transition exhibits the visible photoluminescence.

Characterising scale-breakdown mechanisms during high-temperature oxidation using EM

1990 ◽  
Vol 48 (4) ◽  
pp. 878-879
Author(s):  
P .N. Rowley ◽  
R. Brydson ◽  
J. A. Little ◽  
S. R. J. Saunders
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Rapid Development ◽  
Major Effect ◽  
Oxidation Behaviour ◽  
Metal Interface ◽  
Temperature Oxidation ◽  
High Temperature Steam ◽  
Fissure Formation ◽  
Insight Into

The microstructure and chemical composition of oxide films formed during the initial stages of high temperature oxidation have long been recognised as having a major effect on subsequent scaling behaviour. For example, the development of thick (>lμm) duplex scales on Fe-Cr alloys is assumed to occur via a mechanism of pore and fissure formation in the initial oxide (Atkinson, Tomlinson and Cory.) However, this process has rarely been observed using electron microscopy.The investigation of the oxidation behaviour of Fe-9Cr alloys in high temperature steam gives an insight into these scale breakdown processes. Within 3 minutes of the onset of oxidation, significant breakdown of the initially formed thin film occurs due to the development of readily visible fissures and pores at oxide grain boundaries (figure 1). This leads to the ready ingress of oxidant and the rapid development of a thick duplex Fe3O4/(Fe,Cr)3O4 oxide with a thin outer layer of α-Fe2O3 (figure 2). The extremely porous nature of this scale allows further inward diffusion of molecular oxidant, thereby instituting the continued growth of (Fe,Cr)3O4 at the scale/metal interface.

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