| AN Bing,YUE Jianling,ZOU Yangjun,LOU Jiawei,DU Zuojuan,LIU Yu,HUANG Xiaozhong.Growth of Carbon Nanotubes on the Surface of Boron Nitride Coated Silicon Carbide Fibers Based on the CVD Method[J],53(12):218-229, 239 |
| Growth of Carbon Nanotubes on the Surface of Boron Nitride Coated Silicon Carbide Fibers Based on the CVD Method |
| Received:August 08, 2023 Revised:October 17, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.12.018 |
| KeyWord:h-BN CNTs CVD process parameters boron nitride hydroxylation |
| Author | Institution |
| AN Bing |
Powder Metallurgy Research Institute, Central South University, Changsha , China |
| YUE Jianling |
Powder Metallurgy Research Institute, Central South University, Changsha , China |
| ZOU Yangjun |
Powder Metallurgy Research Institute, Central South University, Changsha , China |
| LOU Jiawei |
School of Electrical and Electronic Engineering, Harbin University of Science and Technology, Harbin , China |
| DU Zuojuan |
Powder Metallurgy Research Institute, Central South University, Changsha , China |
| LIU Yu |
Powder Metallurgy Research Institute, Central South University, Changsha , China |
| HUANG Xiaozhong |
Powder Metallurgy Research Institute, Central South University, Changsha , China |
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| Abstract: |
| The optimization of the interfacial layer plays a very critical role in the improvement of the mechanical properties (especially toughness) of silicon carbide fiber/silicon carbide (SiCf/SiC) composites. Hexagonal boron nitride (h-BN) is a common interfacial phase for SiCf/SiC composites, and carbon nanotubes (CNTs) are also popular reinforcing materials for the composites. The work aims to achieve the controlled growth of carbon nanotubes on the surface of boron nitride coated silicon carbide fibers by adjusting the process parameters in chemical vapor deposition (CVD). The effects of chemical vapor deposition conditions, such as impregnation catalyst condition, reaction temperature, reaction time, gas inflow rate, catalyst inflow rate, and BN surface modification, on the morphology, length, and content of CNTs grown on BN-coated silicon carbide fibers were systematically investigated by controlling a single variable and applying characterization means such as scanning electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. By changing the process parameters, the morphology, length, and content of CNTs were adjusted and controlled to obtain CNTs and BN modified silicon carbide fibers (SiC@BN-CNTs). The results showed that the impregnated catalyst could release more Fe catalyst particles in situ on the BN surface, which improved the yield of CNTs, but led to the uneven distribution of Fe particles and aggravated agglomeration phenomenon, making the distribution of CNTs uneven and the diameter coarse and fine. Shortening the distance between the carbon source and the substrate in the tube furnace could increase the length and content of CNTs, which was positive for substrates that were not easy to grow CNTs. The reaction temperature strongly affected the content and length of CNTs. The higher the temperature, the higher the activity of the catalyst particles, the higher the length and content of CNTs, and the more pyrolytic carbon (PyC), leading to the array-like CNTs on the surface. Adjusting the reaction time could control the content and growth density of CNTs. An appropriate increase in the reaction time could make the CNTs grow in the sample more uniformly distributed and improve the phenomenon of uneven force on different fibers. Increasing the catalyst injection rate alone improved the growth of CNTs, but the excessive content had a negative impact on the mechanical properties of the materials. By increasing the inflow rate of gas and catalyst, the content, length, and morphology of CNTs were better and the impurities such as PyC were less. In the process of growing CNTs, the ratio of gas and catalyst was considered. Increasing both in proportion to each other provided more desirable results than adding gas or catalyst alone. The hydroxylation modification of the boron nitride surface improved the carrier-catalyst interaction, promoted the dispersion of catalyst particles, and increased the diameter and yield of CNTs while the morphology changed from array-like to uniformly encapsulated. In the above experiments, the sample SiC@BN-OH obtained by growing CNTs after hydroxylation modification of the boron nitride surface exhibits the maximum CNTs yield of 10.6wt.% with a more uniformly distributed morphology under the parameters of pre-impregnated catalyst, reaction temperature of 700 ℃ and reaction time of 20 min. |
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