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Title: Surface preparation for high purity alumina ceramics enabling direct brazing in hydrogen atmospheres

Abstract

The present invention relates to a method for preparing the surface of a high purity alumina ceramic or sapphire specimen that enables direct brazing in a hydrogen atmosphere using an active braze alloy. The present invention also relates to a method for directly brazing a high purity alumina ceramic or sapphire specimen to a ceramic or metal member using this method of surface preparation, and to articles produced by this brazing method. The presence of silicon, in the form of a SiO.sub.2 -containing surface layer, can more than double the tensile bond strength in alumina ceramic joints brazed in a hydrogen atmosphere using an active Au-16Ni-0.75 Mo-1.75V filler metal. A thin silicon coating applied by PVD processing can, after air firing, produce a semi-continuous coverage of the alumina surface with a SiO.sub.2 film. Room temperature tensile strength was found to be proportional to the fraction of air fired surface covered by silicon-containing films. Similarly, the ratio of substrate fracture versus interface separation was also related to the amount of surface silicon present prior to brazing. This process can replace the need to perform a "moly-manganese" metallization step.

Inventors:
 [1];  [2];  [3]
  1. Danville, CA
  2. Lafayette, CA
  3. Albuquerque, NM
Publication Date:
Research Org.:
SANDIA CORP
OSTI Identifier:
874111
Patent Number(s):
US 6315188
Assignee:
Sandia Corporation (Albuquerque, NM)
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
surface; preparation; purity; alumina; ceramics; enabling; direct; brazing; hydrogen; atmospheres; relates; method; preparing; ceramic; sapphire; specimen; enables; atmosphere; active; braze; alloy; directly; metal; articles; produced; presence; silicon; form; siosub2; -containing; layer; double; tensile; bond; strength; joints; brazed; au-16ni-075; mo-175v; filler; coating; applied; pvd; processing; air; firing; produce; semi-continuous; coverage; film; temperature; found; proportional; fraction; fired; covered; silicon-containing; films; similarly; ratio; substrate; fracture; versus; interface; separation; related; amount; prior; process; replace; perform; moly-manganese; metallization; step; surface layer; hydrogen atmosphere; alumina ceramic; /228/

Citation Formats

Cadden, Charles H, Yang, Nancy Yuan Chi, and Hosking, Floyd M. Surface preparation for high purity alumina ceramics enabling direct brazing in hydrogen atmospheres. United States: N. p., 2001. Web.
Cadden, Charles H, Yang, Nancy Yuan Chi, & Hosking, Floyd M. Surface preparation for high purity alumina ceramics enabling direct brazing in hydrogen atmospheres. United States.
Cadden, Charles H, Yang, Nancy Yuan Chi, and Hosking, Floyd M. Mon . "Surface preparation for high purity alumina ceramics enabling direct brazing in hydrogen atmospheres". United States. https://www.osti.gov/servlets/purl/874111.
@article{osti_874111,
title = {Surface preparation for high purity alumina ceramics enabling direct brazing in hydrogen atmospheres},
author = {Cadden, Charles H and Yang, Nancy Yuan Chi and Hosking, Floyd M},
abstractNote = {The present invention relates to a method for preparing the surface of a high purity alumina ceramic or sapphire specimen that enables direct brazing in a hydrogen atmosphere using an active braze alloy. The present invention also relates to a method for directly brazing a high purity alumina ceramic or sapphire specimen to a ceramic or metal member using this method of surface preparation, and to articles produced by this brazing method. The presence of silicon, in the form of a SiO.sub.2 -containing surface layer, can more than double the tensile bond strength in alumina ceramic joints brazed in a hydrogen atmosphere using an active Au-16Ni-0.75 Mo-1.75V filler metal. A thin silicon coating applied by PVD processing can, after air firing, produce a semi-continuous coverage of the alumina surface with a SiO.sub.2 film. Room temperature tensile strength was found to be proportional to the fraction of air fired surface covered by silicon-containing films. Similarly, the ratio of substrate fracture versus interface separation was also related to the amount of surface silicon present prior to brazing. This process can replace the need to perform a "moly-manganese" metallization step.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2001},
month = {1}
}

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