A kind of preparation method of low boron content sic fiber
A boron content and fiber technology is applied in the field of low boron content SiC fiber and its preparation, which can solve the problems that it cannot be used in the field of nuclear reactor materials, and SiC fiber cannot have both temperature resistance and flexibility, so as to overcome the lack of temperature resistance. , The effect of short preparation cycle, excellent high temperature resistance and flexibility
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[0029] The present invention also proposes a method for preparing SiC fibers with low boron content, see figure 1 , including the following steps:
[0030] 1) The polycarbosilane fiber is heated from room temperature to 600-1000°C at a heating rate of 0.5-5°C / min in a hydrogen atmosphere. If the temperature is too low, the decarburization is incomplete; Silicon, which affects the temperature resistance;
[0031] Preferably, in the step 1), the polycarbosilane fiber has a diameter of less than 40 μm, an oxygen content of less than 1 wt%, a gel content greater than 90 wt%, preferably 18-25 μm, an oxygen content of 0.5-0.9 wt%, and a gel content of The glue content is 97-99wt%. The diameter of the polycarbosilane fiber is too thick, the composition of the finally prepared SiC fiber is not uniform in the radial direction, the core is rich in carbon, and does not have a near-stoichiometric composition. The oxygen content of the non-melting fiber is higher than 1wt%, and the oxyg...
Embodiment 1
[0046] This embodiment provides a method for preparing SiC fibers with low boron content, comprising the following steps:
[0047] Put the oxygen-free non-melting polycarbosilane fiber (diameter about 19.6 μm, oxygen content about 0.84wt%, gel content about 97.6wt%) in the firing furnace, and replace it with hydrogen gas after vacuuming. The heating rate was raised from room temperature to 750°C at a heating rate of 5°C / min, and then from 750°C to 1600°C at a heating rate of 5°C / min under nitrogen, and kept for 1 hour to obtain intermediate fibers.
[0048] The intermediate fiber is continuously fired at 1700°C in a continuous firing furnace at a speed of 1m / min. The atmosphere in the firing furnace is a mixed atmosphere of boron oxide and nitrogen, and the concentration of boron oxide is 4g / L. SiC fibers with low boron content are produced.
[0049] The boron content of the SiC fiber prepared in this example is <0.1wt% (the boron content is less than 0.1wt%, the chemical ana...
Embodiment 2
[0054] This embodiment provides a method for preparing SiC fibers with low boron content, comprising the following steps:
[0055] An oxygen-free non-melting polycarbosilane fiber (diameter about 19.6 μm, oxygen content about 0.84wt%, gel content about 97.6wt%) was placed in a firing furnace, and replaced by a mixed gas of hydrogen and nitrogen after vacuuming, wherein , the concentration of hydrogen is 80vol%, and the temperature is raised from room temperature to 800°C at a heating rate of 1°C / min under a mixed atmosphere, and then the temperature is raised from 800°C to 1500°C at a heating rate of 2°C / min under nitrogen, and kept for 1h , to obtain intermediate fibers.
[0056] The intermediate fiber is continuously fired at 1600°C in a continuous firing furnace at a speed of 3m / min. The atmosphere in the firing furnace is a mixed atmosphere of boron oxide and nitrogen, and the concentration of boron oxide is 5g / L. SiC fibers with low boron content are produced.
[0057] ...
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