GLASS MELTING COMPONENT

Abstract

A glass melting component for use in a melt includes at least one guide structure for the conveying and/or nucleation of gas bubbles from the melt. The guide structure is present at least on a surface of the glass melting component which faces the melt during use of the glass melting component.

Claims

1-16. (canceled)

17. A glass melting component for use in a melt, the glass melting component comprising: a surface of the glass melting component facing the melt during use of the glass melting component; and at least one guide structure disposed on said surface facing the melt for at least one of conveying or nucleation of gas bubbles from the melt.

18. The glass melting component according to claim 17, wherein said at least one guide structure is a raised region on said surface facing the melt.

19. The glass melting component according to claim 17, wherein said at least one guide structure is a depression on said surface facing the melt.

20. The glass melting component according to claim 17, wherein said at least one guide structure includes guide structures configured as depressions and guide structures configured as raised regions.

21. The glass melting component according to claim 17, wherein said at least one guide structure has a substantially rectangular cross section.

22. The glass melting component according to claim 17, wherein said at least one guide structure has a cross section having substantially a shape of a segment of a circle.

23. The glass melting component according to claim 17, wherein said at least one guide structure has a depth or a height in a range of from 10 m to 1000 m.

24. The glass melting component according to claim 17, wherein said at least one guide structure has a width in a range of from 10 m to 1000 m.

25. The glass melting component according to claim 17, wherein said at least one guide structure has an inclination of from 5 to 85 relative to the horizontal in a position of the glass melting component intended for use.

26. The glass melting component according to claim 17, wherein said at least one guide structure has an inclination of from 40 to 80 relative to the horizontal in a position of the glass melting component intended for use.

27. The glass melting component according to claim 17, wherein said at least one guide structure has an inclination of from 50 to 70 relative to the horizontal in a position of the glass melting component intended for use.

28. The glass melting component according to claim 17, wherein said at least one guide structure includes a plurality of substantially parallel guide structures disposed on the glass melting component.

29. The glass melting component according to claim 17, wherein said at least one guide structure is mechanically worked into said surface facing the melt.

30. The glass melting component according to claim 17, wherein said at least one guide structure is at least one of thermally or chemically formed into said surface facing the melt.

31. The glass melting component according to claim 17, wherein the glass melting component is composed of refractory metal or of a refractory metal alloy.

32. The glass melting component according to claim 17, wherein the glass melting component is a metal sheet of a die pack for growing sapphire single crystals.

33. The glass melting component according to claim 17, wherein the glass melting component is a glass melting electrode.

34. The glass melting component according to claim 17, wherein the glass melting component is a crucible or a melting tank.

Description

[0057] The invention is illustrated below by means of figures. The figures show:

[0058] FIG. 1a-c glass melting components in various working examples

[0059] FIG. 2a-f details (schematic) of guide structures

[0060] FIG. 3a schematically a plant for producing sapphire single crystals by the EFG process

[0061] FIG. 3b a glass melting component according to the prior art

[0062] FIG. 3c a working example of a glass melting component having a guide structure

[0063] FIG. 4a-4c variants of guide structures on sheet-like glass melting components

[0064] FIG. 5a-5c variants of guide structures on cylindrical glass melting components

[0065] FIG. 6 schematic depiction of introduction of a guide structure

[0066] FIGS. 7a and 7b scanning electron micrographs of a surface having a guide structure

[0067] FIG. 1a shows a glass melting component 1 having a surface 2 which faces a melt during use of the glass melting component 1, in plan view. On the surface 2 facing the melt there are guide structures 3 for the guiding and/or nucleation of gas bubbles from the melt. The glass melting component 1 in the present case has a plate-like shape. It can be, for example, a metal sheet of a die pack as described above. The orientation of the glass melting component 1 during use is denoted by a vertical V and a horizontal H.

[0068] The guide structures 3 are arranged in a herringbone fashion in the present working example. They run at an angle relative to the horizontal H from a middle region of the glass melting component 1 upward to the outside. The indications of directions are based on an installed position of the glass melting component 1 during use.

[0069] The guide structures 3 are configured as depression (as concave or negative structure) on the surface 2 facing the melt. As an alternative, the guide structure 3 can be configured as raised region (as convex or positive structure).

[0070] Heterogeneous nucleation results in formation of gas bubbles on the guide structure 3 and these largely remain adhering to the guide structure 3. The orientation of the guide structures 3 at an angle relative to the horizontal H results in gas bubbles B on the guide structures 3 being conveyed upward by buoyancy (indicated by the black block arrow) to the edges of the glass melting component 1. The angle is preferably about 60.

[0071] In FIG. 1b, the glass melting component 1 is configured as glass melting electrode. The guide structures 3 in this case run in a screw-like manner at an angle relative to the horizontal H to the surface 2 of the glass melting component 1. Gas bubbles form and collect at the guide structure 3. As a result of collection of the gas bubbles at the guide structure 3, the gas bubbles combine to form larger bubbles and become detached more quickly from the glass melting component 1, here the glass melting electrode, due to the higher buoyancy.

[0072] FIG. 1c shows glass melting component 1 as crucible or melting tank. Here too, guide structures 3 can be present on the surface 2 of the glass melting component 1 which faces the melt. The effect of the guide structures here is primarily nucleation of gas bubbles. Thus, outgassing of a melt in the glass melting component 1 is thus accelerated.

[0073] FIGS. 2a to 2f schematically show glass melting components 1 having various configurations of guide structures 3 in cross section.

[0074] FIG. 2a shows a guide structure 3 as depression having an essentially rectangular cross section on the surface 2 of the glass melting component 1 which faces the melt.

[0075] FIG. 2b shows a guide structure 3 as raised region having an essentially rectangular cross section on the surface 2 of the glass melting component 1 which faces the melt.

[0076] FIG. 2c shows a guide structure 3 as depression having an essentially triangular cross section on the surface 2 of the glass melting component 1 which faces the melt.

[0077] FIG. 2d shows a guide structure 3 as raised region having an essentially triangular cross section on the surface 2 of the glass melting component 1 which faces the melt.

[0078] FIG. 2e shows a guide structure 3 as depression having a cross section having the shape of essentially a segment of a circle on the surface 2 of the glass melting component 1 which faces the melt.

[0079] FIG. 2f shows a guide structure 3 as raised region having a cross section having the shape of essentially a segment of a circle on the surface 2 of the glass melting component 1 which faces the melt.

[0080] The negative forms of the guide structures 3 in FIGS. 2a, 2c and 2e have a depth t which is preferably in the range from 10 m to 1000 m, as shown by way of example in FIG. 2a.

[0081] The positive forms of the guide structures in FIGS. 2b, 2d and 2f have a height h which is in the range from 10 m to 1000 m, as shown by way of example in FIG. 2b. The depth or height is more preferably in the range from 20 m to 500 m, particularly preferably from 20 m to 300 m.

[0082] A width b of the guide structures 3 is indicated by way of example in FIGS. 2a and 2b and is preferably in the range from 10 m to 1000 m. The width b is more preferably in the range from 20 m to 300 m.

[0083] The dimensions in respect of the depth t, the width b and the height h are shown by way of example in FIGS. 2a and 2b and apply analogously to the FIGS. 2c to 2f.

[0084] Unlike grooves as can be present on a surface after conventional machining, for example milling or grinding, the guide structures preferably cover significantly less than 10% of the surface. Machining structures from conventional machining, on the other hand, are present over the entire surface.

[0085] A further difference of machining structures, for example grooves, from conventional machining is that grooves are essentially uniformly distributed over the entire surface and are frequently oriented along one direction. In addition, the depth or height of the guide structures is significantly greater than roughness values originating from conventional machining. Thus, maximum roughness values Ra of a turned surface are, for example, 1.0 m while the guide structure preferably has a depth t or height h in the range from 10 m to 1000 m. The guide structures are thus at least an order of magnitude larger than tracks of conventional machining.

[0086] FIG. 3a schematically shows a plant for producing sapphire single crystals by the EFG process. Here, metal sheets, which generally consist of molybdenum, are dipped at a close spacing into a melt S of Al.sub.2O.sub.3. The arrangement is referred to as die pack. Melt S rises through the capillary gap between the metal sheets and can be drawn off as sapphire single crystal, as indicated by the directional arrows. Gas bubbles B occur in the melt S. The glass melting components 1 in this use example are the individual metal sheets of the die pack arrangement.

[0087] FIG. 3b shows a glass melting component 1 in the form of a metal sheet of a die pack arrangement and a single crystal EK according to the prior art obtained with the aid of this component. Gas bubbles B are randomly distributed on the glass melting component 1 at the surface 2 facing the melt, and these are again present randomly distributed over a cross section of the single crystal EK (shown above the glass melting component 1). A single crystal EK having gas bubbles cannot be used.

[0088] FIG. 3c, on the other hand, shows a glass melting component 1 in a working example of the invention. Here, guide structures 3 have been produced on the surface 2 of the glass melting component 1, here configured as metal sheet of a die pack arrangement, which faces the melt.

[0089] Gas bubbles B collect at the guide structures 3 and are, as indicated above, conveyed upward and outward. The arrangement and number of the guide structures 3 is purely schematic.

[0090] Absolutely no gas bubbles B are present in the single crystal EK (shown above the glass melting component 1) obtained using the glass melting component 1 of this working example, or gas bubbles B are restricted to a peripheral region R. This peripheral region R can be trimmed off, so that the yield of single crystal EK is significantly increased compared to the prior art when using a glass melting component 1 according to the invention.

[0091] FIGS. 4a to 4c show different variants of the arrangements of guide structures 3 on the surface 2 of sheet-like glass melting components 1 for the example of a metal sheet of a die pack.

[0092] FIG. 4a shows two guide structures 3 which are inclined at an angle to the horizontal H and run upward and outward.

[0093] The variant of FIG. 4b shows two sets of guide structures 3 which are inclined at an angle to the horizontal H and run upward and outward. The angle here is greater than in the example of FIG. 4a.

[0094] In the example of FIG. 4c, guide structures 3 are offset and overlap in a projection along the vertical H. Due to the overlapping, gas bubbles are collected with a particularly high probability by the guide structures 3.

[0095] FIGS. 5a to 5c show different variants of the arrangements of guide structures 3 on the surface 2 of an essentially cylindrical glass melting component 1 for the example of a glass melting electrode.

[0096] In the example of FIG. 5a, the guide structures 3 run in a screw-like manner at an angle to the horizontal along the surface 2 of the glass melting electrode.

[0097] In the example shown in FIG. 5b, a riser channel is provided in addition to a screw-like guide structure 3. The riser channel can be configured as groove or furrow essentially parallel to the vertical V along the surface 2. Gas bubbles which are guided by the guide structure 3 to the riser channel become detached from the guide structure 3 there and escape via the riser channel. In this way, the gas bubbles are removed particularly quickly from the glass melting component 1, here glass melting electrode. The guide structures 3 themselves can run in a screw-like manner along a single screw curve or, as shown in the variant in FIG. 5c, along various partial screw tracks which can have an opposite handedness. Other courses along essentially continuous curves, preferably continuously ascending curves, are also possible.

[0098] The number of guide structures 3 shown in all the figures is purely illustrative. The actual number depends on the dimensions of the glass melting component 1. To name an example, from one to ten guide structures 3 could be present on a metal sheet having typical dimensions of about 100100 mm for a die pack. A balanced ratio of the number of guide structures and their spacing is advantageous. Both can be determined by experiment. An excessively close arrangement brings no additional benefits while in the case of spacings which are too large, gas bubbles may no longer be able to be collected.

[0099] In the case of the example of the glass melting electrode in which the guide structure 3 can run continuously along a screw curve, the individual tracks of the guide structures can, for example, be 1-2 cm apart.

[0100] The spacing of the guide structures is thus significantly greater than the structure size of the guide structure itself. Here, the term structure size means the width and also height or depth of the guide structures.

[0101] FIG. 6 shows a process for producing a guide structure 3 in the surface 2 of a glass melting component 1. Here, the introduction is effected by means of scoring with a scoring needle.

[0102] FIGS. 7a and 7b show scanning electron micrographs of a surface 2 having a guide structure 3, with the images differing in respect of the enlargement selected. In the present example, the guide structure 3 was introduced into a molybdenum sheet by needle scoring. It can be seen that the width b of the guide structure 3 is about 30 m.

[0103] The depth of the guide structure is about 15 m.