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Title: Air Brazing: A New Method of Ceramic-Ceramic and Ceramic-Metal Joining

Abstract

A new method of ceramic-ceramic and ceramic-metal joining has emerged over the past several years. Referred to as air brazing, the technique was originally designed and developed for use in fabricating high-temperature solid-state electrochemical devices such as planar SOFCs and oxygen and hydrogen concentrators. The primary advantage of air brazing is that a predominantly metallic joint can be formed directly in air without need of an inert cover gas or the use of surface reactive fluxes. The resulting bond is hermetic, offers excellent room temperature strength, and is inherently resistant to oxidation at high temperature. The key to developing a successful filler metal composition for air brazing is to identify a metal oxide wetting agent that is mutually soluble in a molten noble metal solvent. One particular oxide-metal combination that appears readily suited for this purpose is CuOx-Ag, a system originally of interest in the development of silver clad cuprate-based superconductors. Studies of the equilibrium phases studies in this system indicate that there are two invariant points in the pseudobinary CuOx-Ag phase diagram around which new braze compositions can be developed: 1) a monotectic reaction at 969±1°C, where CuO and a Ag-rich liquid L1 coexist with a second CuOx-rich liquidmore » phase L2 at a composition of xAg/(xAg + xCu) = 0.10±0.03 Ag and 2) a eutectic reaction at 942±1°C, where CuO and Ag coexist with L1 at a composition of xAg/(xAg + xCu) = 0.99±0.005. Specifically, near-eutectic Ag-CuO filler metal compositions have shown good promise in joining electrochemically active ceramics such as yttria-stabilized zirconia, lanthanum strontium manganite, and barium strontium cobalt ferrite, as well as alumina and magnesia. More recently it has been found that various ternary additions can further improve the wetting characteristics of these filler metals, increase their potential operating temperatures, and/or increase the resulting strength of the joint strength. Here we review the basic concept of air brazing and illustrate filler metal selection and design using the Ag-CuO system as an example.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1080148
Report Number(s):
PNNL-SA-62415
AA6010000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Book
Resource Relation:
Related Information: Ceramic Integration and Joining Technologies: From Micro to Nanoscale, 91-141
Country of Publication:
United States
Language:
English
Subject:
air brazing; ceramic joining; silver-copper oxide filler metal

Citation Formats

Weil, K. Scott, Darsell, Jens T., and Kim, Jin Yong. Air Brazing: A New Method of Ceramic-Ceramic and Ceramic-Metal Joining. United States: N. p., 2011. Web.
Weil, K. Scott, Darsell, Jens T., & Kim, Jin Yong. Air Brazing: A New Method of Ceramic-Ceramic and Ceramic-Metal Joining. United States.
Weil, K. Scott, Darsell, Jens T., and Kim, Jin Yong. Sat . "Air Brazing: A New Method of Ceramic-Ceramic and Ceramic-Metal Joining". United States.
@article{osti_1080148,
title = {Air Brazing: A New Method of Ceramic-Ceramic and Ceramic-Metal Joining},
author = {Weil, K. Scott and Darsell, Jens T. and Kim, Jin Yong},
abstractNote = {A new method of ceramic-ceramic and ceramic-metal joining has emerged over the past several years. Referred to as air brazing, the technique was originally designed and developed for use in fabricating high-temperature solid-state electrochemical devices such as planar SOFCs and oxygen and hydrogen concentrators. The primary advantage of air brazing is that a predominantly metallic joint can be formed directly in air without need of an inert cover gas or the use of surface reactive fluxes. The resulting bond is hermetic, offers excellent room temperature strength, and is inherently resistant to oxidation at high temperature. The key to developing a successful filler metal composition for air brazing is to identify a metal oxide wetting agent that is mutually soluble in a molten noble metal solvent. One particular oxide-metal combination that appears readily suited for this purpose is CuOx-Ag, a system originally of interest in the development of silver clad cuprate-based superconductors. Studies of the equilibrium phases studies in this system indicate that there are two invariant points in the pseudobinary CuOx-Ag phase diagram around which new braze compositions can be developed: 1) a monotectic reaction at 969±1°C, where CuO and a Ag-rich liquid L1 coexist with a second CuOx-rich liquid phase L2 at a composition of xAg/(xAg + xCu) = 0.10±0.03 Ag and 2) a eutectic reaction at 942±1°C, where CuO and Ag coexist with L1 at a composition of xAg/(xAg + xCu) = 0.99±0.005. Specifically, near-eutectic Ag-CuO filler metal compositions have shown good promise in joining electrochemically active ceramics such as yttria-stabilized zirconia, lanthanum strontium manganite, and barium strontium cobalt ferrite, as well as alumina and magnesia. More recently it has been found that various ternary additions can further improve the wetting characteristics of these filler metals, increase their potential operating temperatures, and/or increase the resulting strength of the joint strength. Here we review the basic concept of air brazing and illustrate filler metal selection and design using the Ag-CuO system as an example.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {10}
}

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