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Title: Wetting and Reaction Characteristics of Al2O3/SiC Composite Refractories

Abstract

The reactive wetting behavior of three types of alumina-silicon carbide composite refractory materials was investigated in contact with molten aluminum (Al) and Al alloy using an optimized sessile drop method at 900oC in a purified Ar-4% H2 atmosphere. The time dependent behavior of contact angle and droplet geometry was monitored and the wetting kinetics was identified. The initial contact angle between the liquid Al/Al alloy and two of the refractory substrates was found to be an obtuse angle, which gradually changed to a 90o angle and then eventually to an acute angle with time. However, the wetting angle for the third refractory substrate was found to stay at an obtuse angle for the entire two-hour duration of the experiment. The difference in wetting properties among three types of refractories is attributed to be due to their microstructural and compositional variations. The significant effect of the alloying magnesium added to the molten Al alloy droplets in regard to the wetting kinetics and the influence on the reaction with the refractory substrates is discussed. The results obtained provide important understanding on the wetting and corrosion mechanisms of alumina and silicon carbide materials in contact with molten aluminum.

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
931048
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Applied Ceramic Technology; Journal Volume: 4; Journal Issue: 6
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; ALUMINIUM; CARBIDES; CORROSION; GEOMETRY; KINETICS; MAGNESIUM; REFRACTORIES; SILICON CARBIDES; SUBSTRATES; COMPOSITE MATERIALS

Citation Formats

Xu, Jing, Hemrick, James Gordon, Peters, Klaus-Markus, Liu, Xingbo, and Barbero, Ever J. Wetting and Reaction Characteristics of Al2O3/SiC Composite Refractories. United States: N. p., 2007. Web. doi:10.1111/j.1744-7402.2007.02177.x.
Xu, Jing, Hemrick, James Gordon, Peters, Klaus-Markus, Liu, Xingbo, & Barbero, Ever J. Wetting and Reaction Characteristics of Al2O3/SiC Composite Refractories. United States. doi:10.1111/j.1744-7402.2007.02177.x.
Xu, Jing, Hemrick, James Gordon, Peters, Klaus-Markus, Liu, Xingbo, and Barbero, Ever J. Mon . "Wetting and Reaction Characteristics of Al2O3/SiC Composite Refractories". United States. doi:10.1111/j.1744-7402.2007.02177.x.
@article{osti_931048,
title = {Wetting and Reaction Characteristics of Al2O3/SiC Composite Refractories},
author = {Xu, Jing and Hemrick, James Gordon and Peters, Klaus-Markus and Liu, Xingbo and Barbero, Ever J},
abstractNote = {The reactive wetting behavior of three types of alumina-silicon carbide composite refractory materials was investigated in contact with molten aluminum (Al) and Al alloy using an optimized sessile drop method at 900oC in a purified Ar-4% H2 atmosphere. The time dependent behavior of contact angle and droplet geometry was monitored and the wetting kinetics was identified. The initial contact angle between the liquid Al/Al alloy and two of the refractory substrates was found to be an obtuse angle, which gradually changed to a 90o angle and then eventually to an acute angle with time. However, the wetting angle for the third refractory substrate was found to stay at an obtuse angle for the entire two-hour duration of the experiment. The difference in wetting properties among three types of refractories is attributed to be due to their microstructural and compositional variations. The significant effect of the alloying magnesium added to the molten Al alloy droplets in regard to the wetting kinetics and the influence on the reaction with the refractory substrates is discussed. The results obtained provide important understanding on the wetting and corrosion mechanisms of alumina and silicon carbide materials in contact with molten aluminum.},
doi = {10.1111/j.1744-7402.2007.02177.x},
journal = {International Journal of Applied Ceramic Technology},
number = 6,
volume = 4,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The reactive wetting behavior in molten aluminum (Al) and Al alloy was investigated for alumina-silicon carbide composite refractory materials using an optimized sessile drop method at 900oC in a purified Ar-4% H2 atmosphere. The time dependent behavior of the contact angle and drop geometry was monitored and the wetting kinetics were determined. The initial contact angle between the liquid Al/Al alloy and the refractory substrates was found to be greater than 90 and to gradually decrease with time. For two of the materials, it was found that the contact angles decreased to and angle less than 90 by the endmore » of the two-hour test. For the third material, the contact angle was still greater than 90 at the conclusion of the two-hour test. The difference in wetting properties among the three types of refractories is attributed to their microstructural and compositional variations. The effect of magnesium in the molten Al alloy drops on the wetting kinetics and the reaction with the refractory substrates are also discussed. The results obtained provide important understanding of the wetting and corrosion mechanisms of alumina and silicon carbide materials in contact with molten aluminum.« less
  • The interface physical and chemical characteristics between matrix and reinforcement are vital to the metal matrix composites (MMCs) properties. Interfacial studies usually include identification of the interfacial structure and/or reaction products and determination of crystallographic relationships. The aim of this paper is to study the interface of SiCp/AZ80 composite and determine the phase that formed at the interface. The mechanism of these phases formation is also discussed.
  • Solid state displacement reactions are being evaluated as a technique to produce intermetallic/ceramic matrix composites in situ. Solid state displacement reactions are diffusional phase transformations whereby two or more elements or compounds react to form new product compounds that are more thermodynamically stable than the starting reactants. Interwoven or dispersed microstructures, important for composite strength and toughness, can be achieved using displacement reactions to produce microstructures unattainable by other means. This amounts to growing the reinforcement phases in situ, which is becoming an increasingly important concept in composite synthesis. Control of the morphology of the product phases is a criticalmore » aspect of these methods. Issues of microstructural control and cleanliness can be addressed using displacement reactions in ways that cannot be treated with other techniques. In this paper, the authors pursued a phenomenological approach. Reactant materials were combined by means of diffusion couples in order to efficiently screen a number of promising reactions. Materials were selected based on their potential to produce useful composites and on thermodynamic considerations. There is a high level of interest in composites based on MoSi{sub 2} and thermodynamic calculations have shown MoSi{sub 2}/SiC to be a thermodynamically stable pair. It was a logical step to react Mo{sub 2}C and Si to form MoSi{sub 2} and SiC.« less
  • Fiber/matrix interfacial debonding and frictional sliding stresses were evaluated by single-fiber pushout tests on unidirectional continuous silicon-carbide-fiber-reinforced, reaction-bonded silicon nitride matrix composites. The debonding and maximum pushout loads required to overcome interfacial friction were obtained from load-displacement plots of pushout tests. Interfacial debonding and frictional sliding stresses were evaluated for composites with various fiber contents and fiber surface conditions (coated and uncoated), and after matrix densification by hot isostatic pressing (HIPing). For as-fabricated composites, both debonding and frictional sliding stresses decreased with increasing fiber content. The HIPed composites, however, exhibited higher interfacial debonding and frictional sliding stresses than those ofmore » the as-fabricated composites. These results were related to variations in axial and transverse residual stresses on fibers in the composites. A shear-lag model developed for a partially debonded composite, including full residual stress field, was employed to analyze the nonlinear dependence of maximum pushout load on embedded fiber length for as-fabricated and HIPed composites. Interfacial friction coefficients of 0.1--0.16 fitted the experimental data well. The extremely high debonding stress observed in uncoated fibers is believed to be due to strong chemical bonding between fiber and matrix.« less
  • Because fiber/matrix interfacial mechanical properties are critical to the overall strength and toughness of fiber-reinforced composites, several test methods have been developed to evaluate fiber debonding and sliding behavior. Most interface testing of metal or ceramic matrix composites has been performed in room (laboratory) air at room temperature without considering the effects of moisture or testing environment on the test results. Even though chemical reactivity at the fiber/matrix interface may be insignificant at room temperature for these composites, it is well known that friction and wear between sliding surfaces can be strongly dependent on environment, even at room temperature. Therefore,more » awareness of the environmental sensitivity of interface testing is necessary for the reliable interpretation and comparison of interfacial mechanical property tests. In addition, such awareness is needed to prevent the potentially inaccurate prediction of the performance of composites intended for service in high altitude or space environments based on interface tests completed in laboratory ambient. This paper will demonstrate the effect of environment on fiber debonding and sliding as evaluated by fiber push-out testing at room temperature of an SCS-6 SiC fiber reinforced reaction-bonded Si{sub 4}N{sub 4} matrix composite (SCS-76/RBSN). SCS-6/RBSN is a promising candidate material for component applications in advanced heat engines, and its low fiber/matrix interfacial shear strength is a key determinant in its demonstrated toughness (as evidenced by graceful failure beyond matrix cracking).« less