A cvi process method for preparing carbon/carbon crucible based on flow field optimization

Abstract

The invention discloses a CVI process method for preparing a carbon / carbon crucible based on flow field optimization, which includes two stages. In the first stage, a crucible prefabricated body containing an inner liner is placed in a high-temperature vapor deposition furnace for deposition, and the crucible prefabricated body has sufficient After the strength, the surface of the crucible preform is machined; in the second stage, an external mold is installed on the outside of the machined crucible preform, and an internal mold is close to the inner surface of the machined crucible preform, and vapor deposition is performed for the second time, and the external mold There are oblique holes on the upper surface, so that the airflow generates spiral rotation and enters the gap between the external mold and the crucible prefabricated body. The invention can reduce the number of times of starting the furnace as far as possible, and greatly saves the cost.

Description

technical field [0001] The invention relates to a CVI process method for preparing a carbon / carbon crucible based on flow field optimization. Background technique [0002] The high demand for clean energy promotes the rapid development of the photovoltaic industry, making the demand for polysilicon and monocrystalline silicon increasingly strong. Efficient production of high-purity monocrystalline silicon has become a key link for the sustainable development of the photovoltaic industry. In the preparation of solar cells, high-purity polysilicon is used to draw monocrystalline silicon rods. The drawing process involves the use of quartz crucibles and graphite crucibles. The quartz crucible will become soft under the action of up to 1400°C-1600°C, and its supporting role It must be provided by the graphite crucible outside. There will be impact during the pulling process. At this time, the shortcomings of graphite crucible, such as low strength and poor thermal shock perform...

AI Technical Summary

Problems solved by technology

The carbon / carbon composite material crucible has a heating and cooling process in use, and the thermal expansion coefficients of different textures are also different, resulting in internal thermal stress concentration, coupled with the thermal vibration generated during the pulling process of single crystal silicon, resulting in the inside of the crucible Crack

[0006] Patent (CN 103193498 A) through the synergistic effect of narrow slit airflow and inductive coupling, although the surface crusting phenomenon can be effectively suppressed, because there are interlaced burrs on the surface of the preform, which have a blocking effect on the airflow, it is easy to form tiny eddy currents in the space of interlaced burrs. zone, so that the residence time of the gas flowing through the slit is prolonged, and the precursor near the surface of the preform becomes inhomogeneous

In addition, the patent (CN 103193498 A) adopts lower air intake, and the macromolecular substances generated by the pyrolysis of hydrocarbon gas in the narrow space are carried by the strong gas flow to the surface of the crucible prefabricated body and enter the pores to further crack into carbon. Molecular substances can easily block the internal pores, making it difficult for subsequent gases to enter. It is difficult to continue to increase when the crucible is deposited to a certain density, and multiple machining and multiple depositions are required to achieve the desired density.

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