Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2002-04-22
2004-03-09
Fuqua, Shawntina (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S405000, C219S411000, C392S416000, C392S418000, C118S224000, C118S225000, C118S501000
Reexamination Certificate
active
06703589
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an apparatus for heat-treating at least one material being processed in a heat-treatment space of a heat-treatment container under a specific process-gas atmosphere of at least one process gas. An apparatus of this type is known for example from EP 0 662 247 B1. In addition to the apparatus, a method for heat-treating a material being processed is presented.
The material being processed known from EP 0 662 247 B1 is a multilayered element which is produced by applying a functional layer to a supporting layer (substrate). In order that the functional layer and/or the supporting layer have a desired physical (electrical, mechanical, etc.) and/or chemical property, processing of the material being processed or the layer and/or the supporting layer will be carried out. The processing comprises heat-treating the material being processed in the presence of a gas (process gas).
For the heat treatment, the material being processed is arranged in a closed heat-treatment container made of graphite. During the heat treatment, the material being processed is exposed to a process gas with gaseous selenium. During the heat treatment, the material being processed takes up an amount of energy, with a partial amount of the amount of energy being supplied to each layer. The heat treatment takes place, for example, at a heating-up rate of 10° C./s. A halogen lamp is used as the energy source of the amount of energy. With the halogen lamp, the heat-treatment container made of graphite is irradiated with an electromagnetic radiation, and consequently the heat-treatment container is heated up. Graphite has a high absorptivity for the electromagnetic radiation in the spectral range of the halogen lamp. The amount of energy absorbed by the graphite is supplied to the material being processed by heat radiation and/or heat conduction. The heat-treatment container consequently acts as a secondary energy source or as an energy transmitter.
Graphite has a high emissivity and a high thermal conductivity. When the material being processed lies on a base of the heat-treatment container, on an underside of the material being processed the amount of energy is supplied substantially by heat conduction. An upper side of the material being processed is supplied with an amount of energy by heat radiation, heat conduction and convection.
The larger the material being processed (the larger the surface area thereof), the more varied the materials used in the material being processed (for example greatly differing coefficient of thermal expansion, different absorptivity for the amount of energy etc.) and the higher a heat-treatment rate (heating-up rate, cooling-down rate), the more difficult it is to control a temperature homogeneity or temperature inhomogeneity in the material being processed. The temperature inhomogeneity may lead to mechanical stress in the material being processed, and consequently to destruction of the material being processed.
SUMMARY AND DESCRIPTION OF THE INVENTION
A problem which arises from the cited prior art is use of, or occurrence of, toxic and/or corrosive gases in heat treatment (for example H
2
Se).
The object of the invention is to demonstrate how safe and reliable heat treatment can be carried out even in the presence of toxic and/or corrosive gases.
To achieve the object, an apparatus is specified for heat-treating at least one material being processed under a specific process-gas atmosphere of at least one process gas with the aid of a heat-treatment unit. The heat-treatment unit has at least one energy source for making the material being processed take up an amount of energy, a heat-treatment container with a heat-treatment space for keeping the material being processed under the process-gas atmosphere during the heat treatment, a heat-treatment chamber, in which the heat-treatment container is arranged at a distance from the heat-treatment chamber, so that there is an intermediate space between the heat-treatment container and the heat-treatment chamber, and a means for producing in the intermediate space a further gas atmosphere of a further gas, different from the process-gas atmosphere. The further gas atmosphere in this case has a pressure gradient.
The further gas atmosphere (which can be set) is distinguished, for example, by a defined partial pressure of a gas or gas mixture (for example air). It is also conceivable for the gas atmosphere to be a vacuum. The intermediate space helps to avoid process gas from being discharged into the surrounding area (atmosphere). For this purpose, in a special configuration, the intermediate space encloses the heat-treatment space.
The means for producing the further gas atmosphere is, for example, a gas cylinder, which is in connection with the intermediate space via one or more openings. A vacuum pump is also conceivable. With both means, a pressure gradient can be established in the intermediate space.
In a special configuration, the heat-treatment space and the intermediate space are connected to each other in such a way that a pressure gradient can be set between the heat-treatment space and the intermediate space.
In a further configuration of the invention, there is at least one heat-treatment unit, with an energy source for making the material being processed take up an amount of energy. The energy source is, for example, a flat bank of heaters, which is formed by a heater array. The heater array comprises, for example, bar-shaped halogen lamps or heating bars arranged parallel to one another. Each halogen lamp may in this case be arranged in a shroud for protection from exposure to the (corrosive) process gas or for easy assembly and disassembly. An energy source of this type sends electromagnetic radiation, in particular in the form of infrared radiation (thermal radiation, intensity maximum at a wavelength between 1 &mgr;m and 2 &mgr;m). An energy source in the form of a resistance heating element, which emits thermal radiation, is also conceivable. An element of this type has, for example, graphite, silicon carbide and/or a metal alloy such as nickel chromium. Additionally conceivable is any electromagnetic radiation (microwaves, UV light) which can lead to a heating-up of the material being processed. In addition, heat conduction and convection are also conceivable for the heat treatment. In a further configuration of the invention, the heat-treatment unit has at least one means for cooling the material being processed. This is accompanied by the advantage that a process sequence comprising various method stages, with at least one heating-up phase and cooling-down phase, can be carried out with the aid of the same apparatus. The means for cooling is, in particular, a cooling gas and/or a cooling liquid. The cooling takes place with the aid of the cooling gas by convection, with, for example, a cooling gas that is cooler in comparison with the material being processed being directed past the material being processed. The cooling may also take place by heat conduction, with the material being processed being in contact with a cooling element with a corresponding coefficient of thermal conductivity. It is conceivable for the cooling element to be an enclosure of the heat-treatment unit with a hollow space through which the cooling gas or the cooling liquid can be directed. In a further configuration, at least one of the energy sources is arranged in a shroud which is at least partially transparent to the electromagnetic radiation of the energy source. For example, the shroud consists of quartz glass. The shroud is preferably vacuum-tight. With the aid of the shroud, the energy source can be protected from contact with a process gas. Moreover, the shroud can be flowed through by a coolant, to accelerate cooling down of the energy source and consequently of the material being processed. A further advantage of this configuration is that the energy source can be easily exchanged.
In a special configuration, the shroud of the energy source has an optical filter for the electrom
Fuqua Shawntina
Shell Solar GmbH
Young & Thompson
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