Chen Zhiyong 1, Li Miaoling 1, sun Weikang 2, Zhang Dongsheng 2, Xu Yingqiang 3, Liu Jianshou 1, Cheng Guangwei 1, Li Bin 1
(1) School of mechanical engineering, Luoyang Institute of technology, Luoyang 471023, Henan Province;
2. Henan fanrui Composite Material Research Institute Co., Ltd., Zhengzhou 451200;
3. School of mechanical and electrical engineering, Northwestern Polytechnic University, Xi'an 710072)
Abstract: the effects of temperature and mass ratio of components on the viscosity of Polycarbosilane / divinylbenzene and Polycarbosilane / DIVINYLBENZENE / xylene precursor solutions, as well as the effects of mass ratio on the crosslinking rate and ceramic yield of the two precursors were studied. The results show that the solution viscosity of Polycarbosilane / DIVINYLBENZENE precursor decreases with the increase of temperature; the increase of divinylbenzene content can reduce the solution viscosity and improve the fluidity of the precursor, but it can reduce the cross-linking rate and ceramic yield of the precursor. The viscosity of Polycarbosilane / DIVINYLBENZENE / xylene precursor solution decreased with the increase of temperature; the viscosity of the precursor solution decreased significantly and the fluidity increased with the increase of xylene mass ratio; moreover, when the mass ratio of Polycarbosilane / DIVINYLBENZENE / xylene was 10:3:2, the viscosity of the precursor solution was 170-410 MPa · s It has good fluidity, long-term stability, high cross-linking rate and ceramic yield, so it is suitable to be used as the impregnating liquid of carbon fiber preform.
Keywords: temperature; mass ratio; Polycarbosilane / DIVINYLBENZENE; Polycarbosilane / DIVINYLBENZENE / xylene; viscosity; ceramic yield
Chinese Library Classification No.: v254 document code: a Article No.: 0454 – 5648 (2018) 09 – 1297 – 07
Online publishing time: July 2, 2018
Received on: December 21, 2017. Revision date: 2018 – 03 – 19.
Fund Project: National Natural Science Foundation of China (51475222); Natural Science Foundation of Henan Province
(162300410197); key scientific research of colleges and universities in Henan Province (17a535001
17a430024); key R & D and promotion projects of Henan Province (182102310043).
First author: Chen Zhiyong (1984 -), male, master, lecturer.
Correspondence Author: Li Miaoling (1970 -), female, doctor, professor.
Preface
Carbon fiber reinforced silicon carbide (C / C-SiC) ceramic matrix composite not only has the advantages of high strength, high temperature resistance, wear resistance and corrosion resistance of silicon carbide ceramic, but also has the advantages of high specific strength, high specific modulus, excellent high temperature comprehensive mechanical properties and outstanding thermal properties of carbon fiber [1-2]. At present, there are four preparation methods of C / C-SiC Ceramic Matrix Composites: hot pressing method [3], chemical vapor infiltration method (CVI) [4], reactive infiltration method (RMI) [5] and precursor conversion method (PIP) [6]. Among them, C / C-SiC is prepared by precursor conversion method In addition to the characteristics of uniform matrix composition distribution, complex product shape and net size forming, ceramic matrix composite also has the advantages of low cracking temperature and excellent comprehensive performance [7]. C / C-SiC Ceramic Matrix composites have been widely used in aerospace fields, such as thrust chamber, throat lining and nozzle of rocket engine, turbine blade and brake system of aircraft engine and thermal protection parts of hypersonic vehicle [8-9]. At present, Polycarbosilane is usually used as ceramic precursor, and the cyclic process of impregnation crosslinking cracking is used to obtain the C / C-SiC Ceramic Matrix Composite with high density and excellent comprehensive properties. When impregnating carbon fiber preforms, in order to improve the impregnation effect and prepare large-scale and complex parts, the precursor solution must have good fluidity: if the viscosity of the precursor solution is too large, the fluidity is poor, which is not conducive to impregnating carbon fiber preforms; if the viscosity of the solution is too low, it can improve the fluidity, but it will reduce the impregnation efficiency. The results show that the mass ratio of the precursor has a significant effect on the viscosity of the solution, and directly determines the crosslinking rate and ceramic yield of the precursor, thus affecting the densification, comprehensive mechanical properties and high-temperature thermal properties of C / C-SiC Ceramic Matrix Composites. At present, the viscosity of PCS / DVB [10 – 11] and PCS / xylene [12] precursor solutions has been reported. DVB, as a solvent, can form a stable precursor solution with PCs without volatilization. As a crosslinking agent, DVB can improve the crosslinking rate of the precursor. Xylene, as a solvent, can dissolve PCs in large quantity, improve the fluidity of precursor solution, and it is easy to volatilize, resulting in the instability of viscosity of precursor solution. because
Therefore, the comprehensive effects of precursor mass ratio on solution viscosity, cross-linking rate and ceramic yield need further study. In order to prepare c / C-SiC Ceramic Matrix Composites with high density and excellent comprehensive properties, the effects of temperature on the viscosity of PCS / DVB and PCS / DVB / xylene precursor solutions were studied. The relationship between the mass ratio of the precursor and the viscosity of the solution, the crosslinking rate and the ceramic yield was analyzed, so as to explore the optimal mass ratio of the precursor and the impregnation temperature range.
conclusion
1) In the range of 30-80 ℃, the viscosity of PCS / DVB and PCS / DVB / xylene precursor solution decreased with the increase of temperature, and the fluidity increased.
2) Increasing the mass ratio of DVB can reduce the viscosity and improve the fluidity of PCS / DVB precursor solution, but can reduce the cross-linking rate and ceramic yield of the precursor.
3) As a cosolvent, xylene can significantly improve the fluidity of PCS / DVB / xylene precursor solution, but reduce the cross-linking rate and ceramic yield of the precursor.
4) When the mass ratio of precursor is m (PCS): m (DVB): m (xylene) = 10:3:2, the viscosity of PCS / DVB / xylene precursor solution is 170-410 MPa · s in the range of 40-60 ℃, which has low viscosity, good fluidity, long-term stability, high cross-linking rate and ceramic yield, and is suitable for the impregnation of carbon fiber preforms.
Some charts in the paper