|
2009年, 第29卷, 第4期 刊出日期:2009-08-20
|
上一期
下一期 |
|
|
|
High Temperature Oxidation as a Production Route for Electronic Materials
W. GAO Z. W. LI
中国腐蚀与防护学报. 2009, 29 (4): 248-252.
Oxidation of metallic components often results in degradation and structural failure, prevention is therefore an important topic. On the other hand, oxidation process creates new products such as metal oxides, can be used as a production route. A well-known process in semiconductor industry is that oxidation in dry or wet atmosphere is a popular way for growth of multi-functional SiO2 films on Si wafers. Recently, oxidation processes under controlled conditions (atmosphere, temperature, and time) are used to prepare various oxides, carbides, or nitrides with micro-/nano-structures, well-defined composition, dimension, shape and properties. The use of oxidation now includes thin film and nano-/micro-sized devices, and porous oxides for sensing and catalysis purposes. This paper introduces the research activities in the authors' group on applications of oxidation as a tool for synthesis of functional materials.
References |
Related Articles |
Metrics
|
|
Complete Maps for the Internal Oxidation of Ideal Ternary Alloys Forming Insoluble Oxides under High Oxidant Pressures
F. GESMUNDO S. WANG Y. NIU
中国腐蚀与防护学报. 2009, 29 (4): 253-261.
This paper presents an analysis of the conditions of stability of the different forms of internal oxidation of ideal ternary A-B-C alloys, where A is the most noble and C the most reactive component, forming insoluble oxide and exposed to high pressures of a single oxidant. The treatment, based on an extension to ternary alloys of Wagner’s criterion for the transition from internal to external oxidation in binary alloys, allows to predict the existence of three different forms of internal oxidation. In fact, in addition to the most common kinds of internal attack, involving the coupled internal oxidation of B+C beneath external AO scales and the internal oxidation of C beneath external BO scales, a third mode, involving the internal oxidation of C beneath external scales composed of mixtures of AO+BO, becomes also possible under special conditions. A combination of the boundary conditions for the existence of these different types of internal oxidation allows to predict three different kinds of complete maps for the internal oxidation in these systems, one of which involves only two modes, while the other two involve all the three possible modes of internal oxidation.
References |
Related Articles |
Metrics
|
|
Metal Dusting-Mechanisms and Preventions
J. Q. ZHANG D. J. YOUNG
中国腐蚀与防护学报. 2009, 29 (4): 262-276.
Metaldusting attacks iron, low and high alloy steels and nickel-or cobalt-base alloys by disintegrating bulk metals and alloys into metal particles in a coke deposit. It occurs in strongly carburising gas atmospheres (carbon activity aC>1) at elevated temperatures (400 ℃~1000 ℃). This phenomenon has been studied for decades, but the detailed mechanism is still not well understood. Current methods of protection against metal dusting are either directed to the process conditions-temperature and gas composition-or to the development of a dense adherent oxide layer on the surface of the alloy by selective oxidation. However, metal dusting still occurs by carbon dissolving in the base metal via defects in the oxide scale. The research work at UNSW is aimed at determining the detailed mechanism of metal dusting of both ferritic and austenitic alloys, in particular the microprocesses of graphite deposition, nanoparticle formation and underlying metal destruction. This work was carried out using surface observation, cross-section analysis by focused ion beam and electron microscopic examination of coke deposits at different stages of the reaction. It was found that surface orientation affected carbon deposition and metal dusting at the initial stage of the reaction. Metal dusting occurred only when graphite grew into the metal interior where the volume expansion is responsible for metal disintegration and dusting. It was also found that the metal dusting process could be significantly changed by alterations in alloy chemistry. Germanium was found to affect the iron dusting process by destabilising Fe3C but increasing the rate of carbon deposition and dusting, which questions the role of cementite in ferritic alloy dusting. Whilst adding copper to iron did not change the carburisation kinetics, cementite formation and coke morphology, copper alloying reduced nickel and nickel-base alloy dusting rates significantly. Application of these fundamental results to the dusting behaviour of engineering alloys is discussed.
References |
Related Articles |
Metrics
|
|