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

Patent · Mon Jan 01 04:00:00 EST 2001

OSTI ID:874111

Cadden, Charles H ^[1]; Yang, Nancy Yuan Chi ^[2]; Hosking, Floyd M ^[3]

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1. Danville, CA
2. Lafayette, CA
3. Albuquerque, NM

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.

• Research Organization: SANDIA CORP
• DOE Contract Number: AC04-94AL85000
• Assignee: Sandia Corporation (Albuquerque, NM)
• Patent Number(s): US 6315188
• OSTI ID: 874111
• Country of Publication: United States
• Language: English

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