Patent Number: 058964320
Section: claims

1. A method of brazeless bonding of dissimilar materials to fabricate a sensor for measuring electrochemical corrosion potential in a nuclear reactor comprising: joining an electrical tip conductor to a sensor tip;  joining an electrical cable to said tip conductor; and  fusing under heat a ceramic powder around said tip conductor to form an integral annular electrically insulating band therearound.  firstly applying a bond coating to said tip conductor; and  secondly plasma spraying said ceramic powder over said bond coating to form a ceramic coating thereon.  positioning a pre-formed ceramic sleeve around said band; and  sealing said sleeve at opposite ends thereof to said tip and said cable.  welding said sleeve to a metal transition piece; and  welding said transition piece to said cable, with said cable having a central conductor spot welded to said tip conductor.  a sensor tip electrically joined to a conductor;  electrical cable electrically joined to said tip conductor; and  an annular electrical insulating ceramic band bonded to said tip and tip conductor without ceramic-to-metal brazes. 2. A method according to claim 1 wherein said band is also bonded to said tip conductor to form a hermetic seal. 3. A method according to claim 2 wherein said band includes an outer exposed surface formed of yttria-stabilized-zirconia or magnesia-stabilized-zirconia. 4. A method according to claim 3 wherein said fusing step comprises plasma spraying said powder over said tip conductor. 5. A method according to claim 4 wherein said fusing step further comprises: 6. A method according to claim 5 further comprising applying successively a plurality of said bond and ceramic coatings atop said tip conductor to effect redundant layers of electrical insulation and sealing. 7. A method according to claim 6 further comprising: 8. A method according to claim 7 further comprising packing a ceramic powder between said sleeve and said band to remove voids therebetween, prior to sealing said sleeve to said cable. 9. A method according to claim 8 wherein both said sleeve and packing powder are yttria-stabilized-zirconia. 10. A method according to claim 9 wherein said sealing step comprises plasma spraying additional amounts of said ceramic powder over said sleeve ends at said tip and said cable. 11. A method according to claim 3 wherein said fusing step comprises molding and sintering said ceramic powder over said tip conductor to form a one-piece insulating band bonded to said sensor tip. 12. A method according to claim 11 further comprising fusing a metal sleeve around one end of said band spaced apart from said sensor tip. 13. A method according to claim 12 wherein said sleeve fusing step comprises hot isostatic pressing of said sleeve to said band. 14. A method according to claim 12 wherein said sleeve fusing step comprises hot pressure bonding of said sleeve to said band. 15. A method according to claim 12 further comprising: 16. A sensor for measuring electrochemical corrosion potential in a nuclear reactor comprising: 17. A sensor according to claim 16 wherein said band comprises a plurality of layers of fused ceramic powder. 18. A sensor according to claim 16 wherein said band comprises a plurality of alternating layers of fused ceramic powder atop corresponding bond coatings. 19. A sensor according to claim 16 further comprising a ceramic sleeve surrounding said band, and sealingly joined to said sensor tip and cable, and said band and sleeve comprise yttriastabilized-zirconia or magnesia-stabilized-zirconia. 20. A sensor according to claim 16 wherein said band comprises fused ceramic powder bonded in one-piece to said tip and conductor.