US2728840A

US2728840A - Specimen heating means

Info

Publication number: US2728840A
Application number: US277997A
Authority: US
Inventors: Maynard J Columbe
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1952-03-22
Filing date: 1952-03-22
Publication date: 1955-12-27
Anticipated expiration: 1972-12-27
Also published as: GB724309A

Description

Dec. 27, 1955 M. J. COLUMBE SPECIMEN HEATING MEANS Filed March 22, 1952 Inventor": MagnaT-d J. Columbe,

His Attornc-gg.

United States Patent SPECIMEN HEATING MEANS Maynard J. Columbe, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application March 22, 1952, Serial No. 277,997

Claims. (Cl. 219-19) This invention relates to means for heating a specimen of material to an elevated temperature and, more particularly, to an attachment for heating a specimen within apparatus wherein the specimen is examined by means of a beam of radiant energy. As employed herein, the term radiant energy includes electromagnetic radiations, e. g., X-rays, gamma rays, etc.; and particles, e. g., electrons, protons, etc.

It is frequently desirable, for example in microscopy and diffraction studies, to examine a specimen while it is maintained at an elevated temperature or conducted through a predetermined temperature cycle. Thus, in electron optical instruments, such as diffraction instruments, crystalline phase changes of materials caused by variations in the temperature of a specimen may be examined to provide information useful for many purposes in connection with investigatory work on materials. Any apparatus employed for heating the specimen must, however, be capable of supporting the specimen in proper position in the path of the beam, and it must not affect the trajectory of the beam to any substantial extent; otherwise truly representative diffraction patterns of high resolution cannot be obtained. Furthermore, the specimen heating means should have low heat loss through radiation and conduction to permit the attainment of desired high temperatures. Also, the specimen heating means should be capable of quick disassembly for cleaning and have a structure which facilitates the insertion or removal of both reflection and transmission samples without complete disassembly.

It is an object of the present invention to provide a new and improved specimen heating means which is adapted as an attachment for apparatus wherein a specimen is examined by means of a beam of radiant energy.

It is another object of the present invention to provide a new and improved specimen heating means which is capable of heating a specimen to a desired elevated temperature without disturbing a beam of radiant energy with which the specimen is being examined. It is a further object of my invention to provide a new and improved specimen heating means which may be quickly disassembled and cleaned.

It is a still further object of the invention to provide a specimen heating means in which reflection and transmission specimens may be inserted without complete disassembly of the heating means.

Briefly stated, the present invention comprises a body of refractory material having a passageway extending therethrough. Within this passageway an electrical heating element is disposed, and mounting means for a specimen is removably located adjacent the heating element so that the temperature of a specimen may be maintained at a desired level. A thin metallic sleeve may be positioned within the passageway surrounding the specimen mounting means to prevent disturbance of the trajectory of a beam of radiant energy passing through the passageway.

For a better understanding of the present invention,

reference may be had to the following description, taken in connection with the accompanying drawing, in which Fig. 1 is a side elevation view of electron diffraction apparatus suitably embodying the invention; Figs. 2 and 3 are exploded perspective and cross-sectional views respectively of the specimen heating means employed as an attachment in the apparatus of Fig. 1; and Fig. 4 is a perspective view of alternative specimen mounting means adapted for insertion into the specimen heating means of Figs. 2 and 3.

Referring now to Fig. 1, there is shown a portion of an electron diffraction instrument which comprises a control panel 1, behind which is located an electron gun (not shown) for projecting a beam of electrons through an evacuated tube 2. The electron beam is focused by means of a focussing yoke 3, which may be of the magnetic type, and falls upon a specimen to be examined and supported by a suitable manipulator 4. The electron beam may either be reflected from the specimen or may be allowed to pass through the specimen, if it is a very thin one, to form a diffraction pattern upon a fluorescent screen 5. Alternatively, the pattern may be formed upon a photographic plate or film located within an evacuated film holder 6. A hinged door or entrance 7 in a specimen chamber 8 is provided for the purpose of assuring easy access to the specimen supported by manipulator 4. Manipulator 4 is preferably of the type described in United States Patent 2,440,067, issued to Igor B. Bensen on April 20, 1948, and assigned to the assignee of the present invention. The manipulator includes a rod 9 upon which a specimen may be supported and suitably positioned within the specimen chamber 8. Since, as has been pointed out above, it is very often desirable to maintain a specimen at an elevated temperature while it is being examined, a specimen heating means 10 is attached to manipulator 4 within specimen chamber 8.

Referring now to Figs. 2 and 3, specimen heating means 10 is illustrated as comprising a cylindrical body 11 of refractory material, such as ceramic, glass or quartz, having a passageway 12 extending therethrough. Extending along passageway 12 and over a portion of the periphery thereof is a thin metallic liner 13, across the top of which is attached by any convenient means such as spot Welding, a Wire mesh 14. Liner 13 is provided with a flange 15 which determines its position within passageway 12 and facilitates its removal therefrom for cleaning. In order to minimize heat loss from radiation and conduc tion, a pair of coaxially aligned metallic radiation shields 16 and 17 are positioned about refractory body 11. Radiation shields 16 and 17 preferably consist of a high melting point metal, such as tantalum or molybdenum, and are maintained in spaced apart coaxial alignment by means of a plurality of metallic spacer members 18. Refractory body 11 is supported within inner radiation shield 16 by means of screws 19 which'extend through a tongued end plate 20. The tongues of end plate 20 may be secured to the inner surface of radiation shield 16 by any convenient means such as spot welding. End plate 20 is provided with a passageway 21 which is aligned with the aperture 12 in refractory body 11.

For the purpose of supporting a specimen within the specimen heating means, there is provided a specimen mounting means 22 which is adapted for use with reflection samples. Mounting means 22 comprises a flanged tray 23 and a leaf spring member 24 which bears against the lower surface of a specimen 25 when the mounting means is inserted into aperture'12. As is apparent from the drawing, the upper surface of specimen 25 bears against shoulders 26 of liner 13, whereby the specimen is maintained securely in place within the heating means. Since the specimen is carried by tray 23, insertion and removal from the heating means are easily accomplished.

7 Heat is supplied to sample 25 by means of a bifilar filamerit assembly 27, the filament section of which is positioned Within the portion 28 of aperture 12. Filament assembly 27 comprises :a l ifilar filament .219 supp upon a ,postfill-of refractory mate-rial which extends longi tudinally along portion 28 of aperture 12. =Post may be attached to or may be integral with .a plate .31 of'refractory material which is affixed to cylindrical body 11 by means of screws 32. A tongued :metallic plate ,33 having an aperture 34 :is positioned against the exterior surface of refractory plate 31 for the purpose of assuring proper positioning of the filament assembly within radiation shield 16 and for the further purpose of dissipating any electrical charges which may be collected upon the surface of plate 31. ,Filarnent 29 may be energized through conductive leads .35 which are connected to a suitable source-of electric current, not shown but preferably direct current. In order to determine the tctrr perature of sample 25 ,11 thermocouple .36 is supported adjacent thereto by refractory plate 31. Thermocouple 36 may be connected to a suitably calibrated millivoltmeter (not shown) through leads '37. In order to further minimize heat loss from the heating means, apertured

caps

38, 39, 49 and 41 are placed as shown about the ends of radiation shields 1.6;and .17.

As will now be readily understood, the heating means of the invention provides a simple, easily assembled and disassembled apparatus for maintaining a specimen at a desired elevated temperature. The heating means is supported within specimen chamber 8 (Fig. 1') by attaching it :to manipulator 4 through .a block 42 of refractory material. Thus, by proper adjustment of manipulator 4, the heating means may be aligned such that the electron beam is directed through the various apertures to strike sample 25 and emerge to form a diffraction pattern. Leads 35 and 37 may be brought through the wall of specimen chamber .8 by means of a hermetically sealed socket (not shown), thereby permitting the .easy removal of the heating means without affecting the remaining components .of the diffraction apparatus. If it is desired to change samples, all that is required is the opening of hinged door 7 and the removal of caps 41 and 40. Thereupon, tray 23 is readily accessible and it may be quickly removed along with leaf spring member 24 and the sample 25. Since the sample is surrounded by the electrostatic shield formed by liner 13 and wire mesh 14, the electron beam is essentially unaffected by electric charges which tend :to collect upon the various members of refractory material. Wire mesh 14 also-permits good heat transfer from filament 29 to sample 25. Furthermore, plates 33 and 20 prevent the electron beam from seeing any exposed, charged surfaces of refractory material as it enters and leaves the heating-means. And since filament 29 is bifilar in form, it is essentially non-inductive; hence the electron beam is not deflected by the magnetic fields associated with the passage of current through the filament.

In Fig. v4, there is illustrated alternative specimen mounting means which may be employed with transmission specimens. As shown, the transmission specimen mounting means comprises a base member 42, leaf spring members 43 and 44 adapted to bear against shoulders 26 of liner 13, and a flanged hollow cylindrical member 45. Cylindrical member 45 is attached to base member 4-:2 by means of a strap 46 to which it is affixed by any convenient means such as spot welding. Transmission specimens may be supported upon wire mesh 48 in a manner well known to :those skilled in the art. Wire mesh 48 may be retained against the flange 49 of member 45 by means of a split collar (not shown), which its snugly within the bore of member 45. Thus, if it is desired to examine transmission specimens instead of reflection specimens, tray 23,.leaf spring 24, and specimen 25 are removedfrom the heating means and replaced by the transmission specimen mounting means shown in Fig. 4. Accordingly, it is apparent that the present inventionprovides specimen heating means which is adaptable to both reflection and transmission specimens.

What I' claim as new and desire to secure by Letters Patent of the United States is:

1. In apparatus for examining specimens of a selected material, means for heating a specimen to a desired temperature comprising a body of refractory material having a passageway extending therethrough, a thin metallic liner extending along said passageway and about at least a portion of its periphery, an electrical heating element disposed within said passageway, and means for retaining a specimen within said passageway adjacent said heating element and in heat transferring relationship therewith.

2. In apparatus for examining specimens of a selected material, means for heating a specimen to a desired temperature comprising a body of refractory material having a passageway extending therethrough, a thin metallic sleeve positioned within said passageway and defining a portion of the cross-sectional area of said passageway, an electrical heating element disposed within said passageway outside said thin metallic sleeve, and means for supporting a specimen within said thin metallic sleeve 'in heat transferring relationship with said heating element.

3. In apparatus for examining specimens of a selected material, means for heating a specimen to a desired temperature comprising a body of refractory material having a passageway extending therethrough, a thin metallic liner extending along said passageway and over a portion of its periphery, a metallic mesh extending along said passageway and transversely thereof whereby said passageway is subdivided by said mesh, an electrical heating element disposed in one of the subdivisions of said pasageway, and means for supporting a specimen within the other of the subdivisions of said passageway in heat transferring relationship with said heating element.

4. An attachment for apparatus wherein a beam of radiant energy is employed to examine a specimen of material comprising means for heating a specimen to an elevated temperature and adapted for maintaining the specimen in the path of the beam including a body of refractory material having a passageway extending therethrough, a thin metallic'liner extending along said passageway and about at least a portion of its periphery, an electrical heating element disposed within said passageway, and means for positioning a specimen within said passageway and in heat xchange relationship with said heating element.

5. An attachment for apparatus wherein a beam of radiant energy is employed to examine a specimen of material comprising means for heating a specimen to a desired temperature and adpated for maintaining the specimen in the path of the beam including a body of refractory material having a passageway extending therethrough to permit the passage of the beam, a thin metallic liner extending along said passageway and over a portion of its periphery, a metallic mesh extending along said passageway and transversely thereof whereby said passageway is subdivided by said mesh, an electrical heating element disposed in one of the subdivisions of said passageway adjacent the path of the beam, and means for positioning a specimen within the other of the subdivisions of said passageway in heat transferring relationship with said heating element.

6. An attachment for apparatus wherein a beam of charged particles is employed to examine a specimen of material comprising means for heating a specimen to a desired temperature and adapted for maintaining the specimen in the path of the beam including a body of re fractory material having a passageway extending therethrough to permit the passage or" the beam, a thin metallic liner extending along said passageway and over a portion. of its periphery, a metallic mesh extending along said passageway and transversely thereof whereby said aperture is subdivided by said mesh, said liner and said mesh together forming an electrostatic shield for preventing electrical charges collected upon said refractory material from influencing the beam, an electrical heating element disposed within said passageway but outside said electrostatc shield, and means for positioning a specimen within said passageway and said electrostatic shield.

7. An attachment as in claim 6 wherein said heating element is non-inductively wound.

8. An attachment for apparatus wherein a beam of charged particles is employed to examine a specimen of material comprising means for heating a specimen to a desired temperature and adapted for maintaining the specimen in the path of the beam including a cylindrical body of refractory material having a longitudinal passageway therethrough, a thin metallic liner extending along said passageway and over a portion of its periphery, a metallic mesh extending along said passageway and transversely thereof, said mesh being connected at its longitudinally extending edges to said metallic liner and forming with said liner an electrostatic shield for preventing electrical charges collected upon said refractory material from influencing the beam, a bifilar heating element disposed within said passageway but outside said electrostatic shield and adjacent said mesh, means for positioning a specimen within said passageway and said electrostatic shield, and at least one apertured cylindrical metallic radiation shield essentially coaxially disposed about said cylindrical body of refractory material, the apertures in said at least one radiation shield being aligned with said passageway in said body of refractory material.

9. An attachment for apparatus wherein a beam of radiant energy is employed to examine a specimen of material comprising means for heating a specimen to a desired temperature and adapted for maintaining the specimen in the path of the beam including a body of refractory material having a passageway extending therethrough for the passage of said beam of radiant energy, an eicctrical heating element disposed Within said sageway, means for retain ng a specimen within said passageway adjacent said heating element and in heat transferring relationship therewith, and a pair oi coaxial heat retaining shields positioned about said body of refractory material.

10. In apparatus for examining specimens of a selected material, means for heating a specimen to a desired temperature comprising a body of refractory material having a passageway extending longitudinally therethrough, a thin metallic liner extending along said passageway and over a portion of its periphery, a metallic mesh extending along said passageway and transversely thereof whereby said passageway is longitudinally subdivided by said mesh, an electrical heating element disposed in one of the subdivisions of said passageway, means for supporting a specimen within the other of the subdivisions of said passageway in heat transferring relationship with said heating element, and a pair of coaxial heat retaining metallic shields positioned about said body of refractory material and having metallic end pieces with apertures therein aligned with the passageway in said refractory material.

References Cited in the file of this patent UNITED STATES PATENTS 1,144,942 Lidberg June 30, 1915 1,686,051 Weber Oct. 2, 1928 2,234,578 Riepert Mar. 11, 1941 2,417,213 Picard Mar. 11, 1947 2,440,472 Horner et al. Apr. 27, 1948 2,514,382 Friedman et al. July 11, 1950 2,554,902 Godley May 29, 1951 2,651,236 Kahler Sept. 8, 1953