Method for preparing heaters by chemical vapor infiltration and resin impregnation, carbonization and densification

Abstract

The invention discloses a method for preparing heaters by chemical vapor infiltration and resin impregnation, carbonization and densification, comprising the following steps: adopting carbon cloth andshort carbon fiber mesh tires to be laminated alternately to form plane fibers and introducing reinforcing fibres in the vertical direction to prepare three-dimensional heater preforms, carrying outthe followings on the three-dimensional heater preforms in sequence: chemical vapor infiltration and densification processes, resin pressure impregnation, carbonization and densification treatment, high-temperature treatment in high vacuum and mechanical processing, carrying out chemical vapor deposition coating treatment on the surfaces of the heater preforms undergoing mechanical processing, thus obtaining carbon / carbon heaters with high resistivity and higher purity. The method of the invention ensures good densification effect, can evidently prolong the service lives of the carbon / carbon heaters, can improve the product purity under the premise of not reducing the resistance of the carbon / carbon heaters, can greatly improve the heat shock resistance and structural stability of the products and can effectively enhance the erosion resistibility and corrosion resistance under the atmospheres of SiCl4 and HCl of the heaters.

Description

Technical field [0001] The invention belongs to the technical field of heating elements for polysilicon hydrogenation furnaces and other high-temperature furnaces, and specifically relates to a method for preparing a heating element by chemical vapor infiltration and resin impregnation carbonization. Background technique [0002] At present, the main method of producing polysilicon is the improved Siemens method, and the polysilicon produced by the improved Siemens method accounts for more than 80% of the total global polysilicon production. When improving the Siemens method to produce polysilicon products, the hydrogenation furnace is a step in the recycling system, that is, the reaction product recovery, which is about to generate SiCl, a by-product produced by the reaction of polysilicon products. 4 With H 2 Reaction to produce SiHCl 3 Raw materials are reused. In the hydrogenation furnace, at 1250℃, SiCl 4 With H 2 The mixed gas enters the furnace at a speed of 30m / s to react...

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Problems solved by technology

The continuous operation time of the hydrogenation furnace is more than 2000 hours, so the service life of the heating element will seriously affect the continuous operation time of the hydrogenation furnace

[0003] Chinese patent ZL200610043185X, titled "Preparation method of carbon / carbon heater for monocrystalline silicon drawing furnace and polycrystalline silicon smelting furnace", discloses the use of needle-punched carbon cloth and non-weft cloth to make full carbon fiber three-way structure heating The prefabricated body of the heater, the matrix adopts the binary carbon matrix of pitch carbon and resin carbon, and is purified under the condition of 2000-2500 ℃ with chlorine gas and freon. Composed of carbon fibers, the matrix carbon has a pitch carbon component with good electrical conductivity, and the temperature exceeds 2000 ° C. The resistance value of the carbon / carbon heating element is only 0.016~0.020Ω, which is one less than the required value. order of magnitude; (2) when furfurone resin or phenolic resin is impregnated, no vacuum pressure impregnation technology scheme is adopted, and the impregnation efficiency is 30% lower

[0004] The carbon / carbon heating element for polycrystalline silicon hydrogenation furnace made in Russia adopts carbon cloth laminated prefabricated body, which is densified by soaking method chemical vapor infiltration process. The disadvantages are: (1) The carbon cloth laminated prefabricated body is easy to There are delamination defects in the thickness direction, and the yield is low; (2) The ash content is high, usually 2000-4000ppm, which is not suitable for applications requiring high purity

Its shortcomings: (1) The strength of graphite bolts is low, and the bolts are used to fasten the connection, resulting in a large contact resistance at the connection part, which causes uneven local temperature of the heating element during the working process, resulting in uneven thermal field in the hydrogenation furnace; (2) The heating element is composed of three parts, which is inconvenient to install and easy to damage

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