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Verfahren und Vorrichtung zur Bestimmung der Schmelzhöhe und zur Regulation der Erstarrung und Schmelzung in einem Tiegel

In-situ determination of current melt level during directional solidification of partially molten material, comprises e.g. determining first melt height of melted material and producing shadow on molten surface of melted material
 
: Friedrich, Jochen; Reimann, Christian; Wunderwald, Ulrike

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Frontpage ()

DE 102013002471 A1: 20130213
Deutsch
Patent, Elektronische Publikation
Fraunhofer IISB ()

Abstract
In-situ determination of the current melt level during directional solidification of partially molten material, comprises (a) determining first melt height (z0) of melted material at a first time point (t0), (b) producing a shadow on the molten surface of melted material at first time point (t0), (c) determining the first position (x0) of a point on the edge of the shadow, (d) carrying out directional solidification or melting of melted material to a second time point (t1), (e) determining the lateral position change from at least one point, and (f) calculating the second melt height.

In-situ determination of the current melt level during directional solidification or melting of at least partially molten material with volume leap during phase transition from solid to liquid in a crucible (4), comprises (a) determining first melt height (z0) of at least partially melted material at a first time point (t0), in which the melt height results from the distance from the bottom of the crucible to the molten surface of at least partially melted material, (b) producing a shadow or a bright spot on the molten surface of at least partially melted material at first time point (t0) by irradiation of at least one light beam from a light source (5), irradiating the light beam at an angle (alpha ) of greater than 0[deg] to less than 90[deg] to the surface of the melt (7), (c) determining the first position (x0); of at least one point on the edge of the shadow or bright spot with an optical detector (6), (d) carrying out directional solidification or melting of at least partially melted material to a second time point (t1), (e) determining the lateral position change (x0-x1 is equal to delta x) from at least one point with the optical detector, and (f) calculating the second melt height (z1) at second time (t1) by an equation comprising (z1 is equal to z0 + delta xx tan (alpha ). The position change in the direction of the light source is greater than 0, and the position change away from the light source is less than 0. At least one point laterally to the surface of melt at second time point (t1) has a second position (x1), which is moved to the first position (x0) in the direction of the light source or laterally away from the light source to the molten surface. The shadow or bright spot has an edge with multiple points. Independent claims are also included for: (1) in-situ controlled solidification or melting of at least one partially molten material with volume leap during the phase transition from solid to liquid in the crucible, comprising at least partially regulating the heating and/or cooling of the crucible by determining the change in melt height per time, preferably by the growth rate v(t) of the solid in the liquid melt, preferably by an equation comprising (v(t) is equal to delta z/delta t, where delta t is time interval for the change in melt height (delta z); (2) a device for determining the current melt level during directional solidification or melting of at least partially melted material with volume leap during phase transition from solid to liquid in the crucible comprising (a) at least one crucibles with the melt of at least partially melted material having volume leap during phase transition from solid to liquid, (b) at least one light source for irradiation of at least one light beam in at least one angle(alpha ) to the surface of the melt, (c) at least one optical detector for determining the lateral position change of point on the surface of the melt, and the converting lateral position change in a signal, (d) at least one unit, which converts the signal of the optical detector into the signal of the current melting height; and (3) a device for controlled solidification or melting of at least one partially molten material with volume leap during the phase transition from solid to liquid in the crucible, comprising at least one heating element and/or cooling element, which is regulated by the signal from the optical detector.

USE: The method is useful for in-situ determination of the current melt level during directional solidification or melting of at least partially molten material with volume leap during phase transition from solid to liquid in a crucible.

ADVANTAGE: The method is carried out in an easy, precise, robust, time- and space-resolved manner.

The figure shows a schematic representation of the device. 4 : Crucible 5 : Light source 6 : Optical detector 7 : Melt 8 : Mask

INSTRUMENTATION AND TESTING: Preferred Method: The material present in the crucible material is melted as long as a melt height is reached, where a seed plate and a seed made of a solid material, which lies at the bottom of the crucible, is not melted. The shade or the bright spot is produced by applying at least one mask (8) fixedly above the melt. The mask at least partially passes through and at least partially blocked by at least one light beam. The lateral position change (x1 - x0) of at least one other point is determined on the edge of the shadow or bright spot at second time point (t1), and the second melt height (z1) results as the arithmetic average of the calculations. At least one second light beam is irradiated from a second light source, which produces a shade or a bright spot on the surface of the melt. The second light beam is irradiated at an angle (beta ) to the surface of the melt. Preferred Components: The angle (beta ) is less than 0 to less than 90[deg] C, and angle (beta ) is different from angle (alpha ). The angle (alpha ) is greater than 0 to 60[deg] , preferably greater than 0 to 20[deg] C. The mask is a cover plate for a crucible. The optical detector is arranged horizontally or vertically to the surface of the melt, preferably attached at the outer end of a perpendicular or slating surface of the arranged tube. The tube is a tube for manipulating solidification processes. The optical detector is digital optical sensors, preferably a charge-coupled devices (CCD) camera. The light source is light emitting diode, organic light emitting diode, laser and light-emitting heating elements (preferred). At least one light source is at least partially attached to a cover of the crucible, preferably on the side of the cover, which is directed to the melt. The material with volume leap during the phase transition of solid to liquid comprises silicon, germanium, III-V semiconductors, II-VI semiconductor, fluorides, oxides or metals. The device for determining the current melt level and the device for controlled solidification is used for controlling and regulating heating elements and/or cooling elements in the seed process.

: http://publica.fraunhofer.de/dokumente/N-311186.html