US3598384A

US3598384A - Metal vapor generators

Info

Publication number: US3598384A
Application number: US856529A
Authority: US
Inventors: Mario Zucchinelli
Original assignee: SAES Getters SpA
Current assignee: SAES Getters SpA
Priority date: 1968-09-13
Filing date: 1969-09-10
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10
Also published as: DE1945508A1; DE1945508B2; FR2018043A1; NL6913693A

Abstract

A particle free device for releasing a metal vapor comprising: a container having walls defining a chamber; an opening in at least one of said walls; a particulate, metal vapor releasing substance within the chamber; and a member within the chamber and adjacent to the opening whereby the opening is rendered permeable to metal vapor but impermeable to the particulate substance.

Description

I United States Patent 1 1 3,598,384

[721 lnventor Mario Zucchinelli 2,793,609 5/1957 Shen et al. I 18/49 Mihmlhly 3,014,115 12/1961 Ingersoll 219/275 m Appl. No. 856.529 3,058,842 10/1962 Kahan etal. 118/49 [22] Filed Sept. 10. 1969 3,446,936 5/1969 Hanson et a]... 219/271 [45] Patented Aug. 10, 1971 3,466,424 9/1969 Adams 118/48 [73] Assignee S.A.E.S. Getters S.p.A. 3,014,115 12/1961 lngersoll 219/275 Milan, Italy 3,457,097 7/1969 Yonegaki et al 1 17/107 [32] Priority Sept. 13, [968 OTHER REFERENCES r z Publication: The Review of Scientific Instruments; Vol 35.

No. 6; June, 1964 (Eichenbaum et a1.) Primary Examiner-Gerald A. Dost [S4] METAL VAPOR GENERATORS Anomey navid R Murphy 10 Claims, 5 Drawing Figs.

[52] 11.8. C1 266/39, 118/49. 219/275 [51] lnLCl C221) 61/00 olSearch A particle free device for releasing a metal R, 34 118/4849, 491,495; 219/27, 275; vapor comprising: a container having walls defining a l l7/107, chamber; an opening in at least one of said walls; a particulate, metal vapor releasing substance within the chamber; and a [56] Rem-"mes member within the chamber and adjacent to the opening UNITED STATES PATENTS whereby the opening is rendered permeable to metal vapor but impermeable to the particulate substance.

PATENTEU AUG 1 0 I97:

INVENTOR MARIO ZUCCHINELLI ATTORNEYS METAL VAPOR GENERATORS DISCLOSURE Devices which release metal vapor, such as those of mercury, cesium, potassium, or sodium, in vessels such as electron tubes, are well'known in the art as described, for example, in Italian U.S. Pat. No. 784,903, Italian completive application 2l538A/67 of Nov. 12, 1967, and by Eichenbaum, et al., Cesium Vapor Dispenser, The Review of Scientific Instrumcnts, Vol. 35, No. 6, June 1964, pp. 69l-693. Unfortunately, the above and other prior art generators suffer from a number of disadvantages. For example, they frequently release small particles before and/or after metal vapor release. These small particles are electrically conductive and can cause short circuits, damage photosensitive surfaces and cause other difficulties within the electron tubes. Another disadvantage is the undesirable absorption of water vapor and gasses from the atmosphere by that portion of the metal releasing substance within the device which comes in contact with atmospheric air. Another disadvantage is the nonuniform compression of the particulate metal vapor releasing substance within the device which generally occurs when the container of the generator is closed. The above and other disadvantages lead to poor reproducibility of results from one generator to another, causing numerable difficulties during production and use of the generators.

Accordingly, it is an obj lot of the present invention to provide novel metal vapor generators which are substantially free of one or more of the disadvantages of the prior art. Another object is to provide metal vapor generators which are substan' tially free of loose particles before and/or after release of the metal vapor. A further object is to provide metal vapor generators having a reduced tendency to absorb water vapor and gases from the air. Another object is to provide metal vapor generators with a uniformly compressed particulate metal vapor releasing substance adjacent to the opening of the generator. Additional objects and advantages will be apparent to those skilled in the art by reference to the following detailed description and drawings wherein:

FIG. 1 is a plan view ofa generator of the present invention;

FIG. 2 is an elevation view of the generator of FIG. 1;

FIG. 3 is an enlarge sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG. 2; and

FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG. 1.

According to the present invention, there is provided a particle free device for releasing a metal vapor. This device comprises a container having continuous walls defining a chamber. The extremities of the walls are juxtaposed parallel to one another to form an opening. A particulate metal vapor releasing substance is within the chamber. Also within the chamber and adjacent to the opening is a member placed such that the opening is rendered permeable to metal vapor but impermeable to the particulate substance.

The container can have any convenient shape, but in one preferred embodiment of the present invention is made from a generally rectangular sheet of material, bent around its longer axis such that the longitudinal extremities of the sheet material are juxtaposed parallel to one another, and define an opening through which the metal vapor is released. In another preferred embodiment, the container is made of a material of high electrical resistance permitting activation of the metal vapor releasing substance by imposing an electrical potential across the ends ofthe container to heat the container.

The particulate metal vapor releasing substance within the chamber can be virtually any suitable material but is generally a mixture of a compound of the desired metal and a reducing agent for the compound. Reducible metallic compounds inl cesium chromate, potassium chromate, and sodium chromate. Mercuric oxide can also be employed if mercury is the desired metal. Any suitable reducible agent such as those described in Eichenbaum or the Italian patent supra can be employed, examples of which include, among others, silicon and aluminum. When the desired metal is barium, any of the well known barium aluminum alloys can be employed. The metal vapor releasing substance is particulate in order to provide a large surface area for vaporization of the metal and/or chemical reaction. However if the particles are too small they tend to escape from the device. Generally those which pass through a US. standard screen of I70 mesh/inch and are retained on a screen of 45 mesh/inch, i.e. those exhibiting a particle size of about l0 to 9011., are suitable.

The member within the chamber is located adjacent to the opening whereby the opening is rendered permeable to metal vapor, but impermeable to the particulate substance. According to the broadest aspects of the invention, the member can have any suitable geometric shape but is preferably elongated having its axis parallel to the extremities of the walls or sheet. The cross section can be any regular of irregular polygon and, thus, can be triangular, square, or hexagonal but is preferably round since such a cross section gives the best seal against loose particles. In the most preferred embodiment of the present invention, the member within the chamber is a wire having a diameter greater than the distance between the extremities of the walls.

Referring now to the drawings and in particular FIGS. 1 and 2 thereof, there is shown a device 10 for generating metal vapors. The device 10 comprises a container or tube I I having terminals 12 and I3 in each end thereof. The terminals I2 and I3 seal the ends of the tube II and together with the walls thereof, define a chamber containing the metal vapor releasing substance I4 which preferably fills the chamber. As shown in FIG. 3, the tube II is formed from a continuous sheet of material such that the tube 11 has a lower wall 15 connected to sidewalls I6 and 17 which in turn are connected to

top walls

18 and 19. The edges of the sheet which is comprised of top walls 18 and [9 meet in juxtaposed relationship defining an opening 20 of width d which is generally to 300 microns. Within the chamber containing the substance 14 is a member 21 which is preferably a wire of circular cross section. The wire 21 is held in place by the substance 14. As shown in FIG. 3, the diameter of the wire 21 is greater than the dimension d. As shown in FIG. 5, the axis of the wire 21 is parallel to the longitudinal edge of the top wall 18 and, therefore, also the top wall 19; By this arrangement, metal vapors produced by the substance 14 can pass by the wire 2] and out the opening 20, whereas loose particles in the substance 14 are kept within the chamber. Another advantage of this arrangement is the decreased tendency for the substance 14 to absorb water vapor and other gases from the air since the chamber is almost effectively sealed by the wire 21 minimizing entry of air into the chamber.

A common method of producing the device 10 is to compress the particulate substance 14 and form the walls I5, 16, I7, l8, and I9 into the general form of FIG. 3 but with the walls to and I7 angled outward at a greater angle than shown, thus making 1! much larger. The walls 16 and I7 are then pressed towards one another to reduce d to the desired value. However, in the absence of the wire 21, the compressed material M adjacent to the opening 20 fractures and produces loose particles.

In a nonlimiting example of operation, the device I0 is placed in a vessel such as an image intensifier tube in which it is desired to introduce cesium vapor. The terminals 12 and I3 are connected to a source of potential not shown, and the tube evacuated by any known means. Current is then caused to flow through the nichrome tube II by impressing a potential across the terminals I2 and I3 until the tube 11 is heated to about 1,000 K, whereupon the substance 14, which is a mixture of one part by weight of Cs CrO and two parts by weight of Si, releases cesium vapor. No loose particles are observed in the vessel either before or after cesium vapor release.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described above and as defined in the appended claims.

lclaim:

l. A particle free device for releasing a metal vapor, said device comprising;

A. a container having continuous walls defining a chamber;

B. the extremities of the walls juxtaposed parallel to one another defining an opening;

C. a particulate metal vapor releasing substance within the chamber; and

D. a member within the chamber and adjacent to the opening whereby the opening is rendered permeable to metal vapor but impermeable to the particulate substance wherein the chamber is completely filled with the metal vapor releasing substance which holds the member in place.

2. The device of claim 1 wherein the container is a material of high electrical resistance.

3. The device of claim 1 wherein the metal vapor is that of an alkali metal.

4. The device of claim 1 wherein the metal vapor is that of mercury.

5. The device of claim 1 wherein the metal vapor is that of barium.

6. The device of claim 1 wherein the metal vapor releasing substance is a mixture of an alkali metal chromate and a reducing agent for the chromate,

7. The device of claim 1 wherein the member is a wire having a diameter greater than the transverse dimension of the opening.

8. A particle free device for releasing a metal vapor, said device comprising:

A. a container having continuous walls defining a chamber;

C. a particulate metal vapor releasing substance within the chamber; and

D. a wire within the chamber adjacent to the extremities of the walls, the wire having a diameter greater than the distance between the extremities of the walls wherein the chamber is completely filled with the metal vapor releasing substance which holds the wire in place.

9. A particle free device for releasing an alkali metal vapor,

said device comprising:

A. a container having continuous walls of a rectangular sheet material of high electrical resistance defining a chamber;

B. the longitudinal extremities of the sheet material juxtaposed parallel to one another defining an opening;

C. a metal vapor releasing substance in the chamber, said substance comprising an alkali metal chromate and a reducing agent for the chromate; and

D. a wire within the chamber adjacent to the longitudinal extremities of the sheet material, the axis of the wire being parallel to the longitudinal extremities of the sheet, the diameter of the wire being greater than the distance between the extremities of the sheet wherein the chamber is completely filled with the metal vapor releasing substance which holds the wire in place.

10. A particle free device for releasing a metal vapor, said device comprising; a container having walls defining a chamber; an opening in at least one of said walls; a particulate, metal vapor releasing substance within the chamber; and a member within the chamber and adjacent to the opening whereby the opening is rendered permeable to metal vapor but impermeable to the particulate substance wherein the chamber is completely filled with the metal vapor releasing substance which holds the member in place.

Patent No.

Invent0r(s) Dated Aucz. l0 l9jl Mario Zucchinelli It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

delete delete delete delete delete delete 20 delete "absorption", insert -sorption "absorb", insert sorb- "enlarge", insert -enlarged- "45", insert -450 "of", insert -or "absorb" insert -sorb and sealed this 22nd day of February 1972.

EDWARD M.FLETCHER, JR- Attesting Officer ROBERT GOITSCHALK Commissioner of Patents 9 FORM PC4050 {10-69) USCOMM'DC 60376-P69 e us, GOVERNMENY Pmm'mo OFFICE 1969 O366-334

Claims

1. A particle free device for releasing a metal vapor, said device comprising: A. a container having continuous walls defining a chamber; B. the extremities of the walls juxtaposed parallel to one another defining an opening; C. a particulate metal vapor releasing substance within the chamber; and D. a member within the chamber and adjacent to the opening whereby the opening is rendered permeable to metal vapor but impermeable to the particulate substance wherein the chamber is completely filled with the metal vapor releasing substance which holds the member in place.

3. The device of claim 1 wherein the metal vapor is that of an alkali metal.

4. The device of claim 1 wherein the metal vapor is that of mercury.

5. The device of claim 1 wherein the metal vapor is that of barium.

6. The device of claim 1 wherein the metal vapor releasing substance is a mixture of an alkali metal chromate and a reducing agent for the chromate.

8. A particle free device for releasing a metal vapor, said device comprising: A. a container having continuous walls defining a chamber; B. the extremities of the walls juxtaposed parallel to one another defining an opening; C. a particulate metal vapor releasing substance within the chamber; and D. a wire within the chamber adjacent to the extremities of the walls, the wire having a diameter greater than the distance between the extremities of the walls wherein the chamber is completely filled with the metal vapor releasing substance which holds the wire in place.

9. A particle free device for releasing an alkali metal vapor, said device comprising: A. a container having continuous walls of a rectangular sheet material of high electrical resistance defining a chamber; B. thE longitudinal extremities of the sheet material juxtaposed parallel to one another defining an opening; C. a metal vapor releasing substance in the chamber, said substance comprising an alkali metal chromate and a reducing agent for the chromate; and D. a wire within the chamber adjacent to the longitudinal extremities of the sheet material, the axis of the wire being parallel to the longitudinal extremities of the sheet, the diameter of the wire being greater than the distance between the extremities of the sheet wherein the chamber is completely filled with the metal vapor releasing substance which holds the wire in place.