Ceramic Discharge Vessel with Expanded Reaction-Bonded Aluminum Oxide Member
A ceramic discharge vessel is provided wherein the discharge vessel has a ceramic body and at least one expanded reaction-bonded aluminum oxide member hermetically sealed to the ceramic body. The method of making the discharge vessel includes (a) forming a ceramic body; (b) forming a reaction-bonded aluminum oxide member in a green state by compacting a mixture of aluminum metal and aluminum oxide powders; (c) assembling the ceramic body and the reaction-bonded aluminum oxide member in the green state to form an assembly; and (d) reaction sintering the assembly to cause the reaction-bonded aluminum oxide member to expand and form a hermetic seal with the ceramic body.
1 . A ceramic discharge vessel comprising a ceramic body and at least one expanded reaction-bonded aluminum oxide member hermetically sealed to the ceramic body.
2 . The ceramic discharge vessel of claim 1 wherein the ceramic body is a tube and the expanded reaction-bonded aluminum oxide member is sealed to the inner surface of the tube.
3 . The ceramic discharge vessel of claim 2 wherein the ceramic body is comprised of polycrystalline alumina or sapphire.
4 . The ceramic discharge vessel of claim 2 wherein the ceramic body is comprised of sapphire.
5 . The ceramic discharge vessel of claim 2 wherein the expanded reaction-bonded aluminum oxide member has an aperture and a capillary tube is inserted in the aperture.
6 . The ceramic discharge vessel of claim 5 wherein the expanded reaction-bonded aluminum oxide member and the capillary tube are formed as a single piece.
7 . The ceramic discharge vessel of claim 5 wherein the capillary tube is composed of polycrystalline alumina.
8 . The ceramic discharge vessel of claim 1 wherein the ceramic body is a tube and the expanded reaction-bonded aluminum oxide member is positioned in a recess in an end of the tube.
9 . The ceramic discharge vessel of claim 2 wherein the expanded reaction-bonded aluminum oxide member has an aperture.
10 . The ceramic discharge vessel of claim 9 wherein the expanded reaction-bonded aluminum oxide member has a flange that seats against an end of the tube.
11 . The ceramic discharge vessel of claim 2 wherein the ceramic body is a tube and the expanded reaction-bonded aluminum oxide member is a capillary tube.
12 . The ceramic discharge vessel of claim 11 wherein the ceramic body is comprised of sapphire.
13 . The ceramic discharge vessel of claim 1 wherein the ceramic body is a tube and the expanded reaction-bonded aluminum oxide member is sealed to the exterior surface of the tube.
14 . A method of forming a hermetic seal in a ceramic discharge vessel comprising:
(a) forming a ceramic body;
(b) forming a reaction-bonded aluminum oxide member in a green state by compacting a mixture of aluminum metal and aluminum oxide powders;
(c) assembling the ceramic body and the reaction-bonded aluminum oxide member in the green state to form an assembly; and
(d) reaction sintering the assembly to cause the reaction-bonded aluminum oxide member to expand and form a hermetic seal with the ceramic body.
15 . The method of claim 14 wherein the aluminum metal powder comprises from 10 to 70 volume percent of the mixture.
16 . The method of claim 14 wherein the aluminum metal powder comprises from 50 to 60 volume percent of the mixture.
17 . The method of claim 14 wherein the reaction-bonded aluminum oxide member in the green state has a green density of 60 to 80 percent.
18 . The method of claim 14 wherein the ceramic body is comprised of polycrystalline alumina that has been at least prefired prior to forming the assembly.
19 . The method of claim 14 wherein the ceramic body has been fully sintered prior to forming the assembly.
20 . The method of claim 14 wherein the ceramic body shrinks during reaction sintering of the assembly.