BN/SiC复合界面层对SiC纤维和PIP-Mini复合材料力学性能的影响

doi:10.15541/jim20190646

摘要/Abstract

摘要：

采用化学气相渗透(CVI)工艺, 在SiC纤维表面沉积BN和BN/SiC复合界面层, 对沉积界面层前后纤维的力学性能进行了评价。采用聚合物浸渍裂解(PIP)工艺进行致密化, 制得以原纤维、BN界面层和BN/SiC界面层纤维增强的三种Mini-SiC_f/SiC复合材料, 研究其微观结构和拉伸性能。结果表明: 采用CVI工艺制得的界面层厚度均匀、结构致密, 其中BN界面层中存在六方相, 晶体尺寸为1.76 nm; SiC界面层结晶性较好, 晶粒尺寸为18.73 nm; 沉积界面层后SiC纤维的弹性模量基本保持不变, 拉伸强度降低。与SiC_f/SiC相比, PIP工艺制备的SiC_f/BN/SiC和SiC_f/(BN/SiC)/SiC-Mini复合材料所能承受的最大拉伸载荷和断裂应变明显提升, BN界面层起主要作用。由断面形貌分析可以看出, SiC_f/BN/SiC和SiC_f/(BN/SiC)/SiC复合材料的纤维拔出明显, 说明在断裂时消耗的能量增加, 可承受的最大载荷增大。

关键词: BN/SiC复合界面层, Mini-SiC_f/SiC复合材料, 最大拉伸载荷, 断裂应变

Abstract:

BN and BN/SiC interphases were deposited on the surface of SiC fibers by CVI process, and the mechanical properties of the as-received and coated fibers were evaluated. SiC_f/SiC minicomposites were prepared by PIP using the as-received, BN-coated and BN/SiC coated fiber bundles as reinforcements. The effects of interphases on the mechanical properties of the composites were studied. The results show that the interphases prepared by CVI process are uniform and compact. The deposited BN interphase contains hexagonal phases with small crystal size (1.76 nm). The deposited SiC interphase has better crystallinity and larger grain size (18.73 nm) than BN interphase. The elastic modulus of coated SiC fibers shows basically no change, but the tensile strength decreases. The maximum tensile load and fracture strain of SiC_f/ BN/SiC and SiC_f/(BN/SiC)/SiC minicomposites are significantly increased, in comparison to SiC_f/SiC minicomposites. It can be seen from the cross-sections of SiC_f/BN/SiC and SiC_f/(BN/SiC)/SiC mini-composites that the fibers with interphases pull out obviously relative to SiC_f/SiC mini-composites, and the BN interphases played a reinforcing role in the tensile fracture process of the composites. The composites with interphases exhibit obvious fiber pull-out resulting in more energy consumption during the fracture, so that the composite can endure more load.

Key words: BN/SiC multilayered interphase, Mini-SiC_f/SiC composites, maximum tensile load, fracture strain

中图分类号:

TB332

吕晓旭, 姜卓钰, 周怡然, 齐哲, 赵文青, 焦健. BN/SiC复合界面层对SiC纤维和PIP-Mini复合材料力学性能的影响[J]. 无机材料学报, 2020, 35(10): 1099-1104.

LÜ Xiaoxu, JIANG Zhuyu, ZHOU Yiran, QI Zhe, ZHAO Wenqing, JIAO Jian. Effect of BN/SiC Multilayered Interphases on Mechanical Properties of SiC Fibers and Minicomposites by PIP[J]. Journal of Inorganic Materials, 2020, 35(10): 1099-1104.

图/表 9

表1 浸渍不同次数后Mini复合材料的线密度

Table 1 The linear density of Mini-composites after different PIP cycles

Linear density (g·m^-1) Sample	PIP cycle
Linear density (g·m^-1) Sample	0	1	2	3	4	5
SiC_f/SiC	(0.303±0.028)	(1.26±0.11)	(1.30±0.14)	(1.32±0.17)	(1.33±0.12)	(1.33±0.13)
SiC_f/BN/SiC	(0.330±0.023)	(1.31±0.10)	(1.34±0.11)	(1.35±0.15)	(1.36±0.10)	(1.36±0.13)
SiC_f/(BN/SiC)/SiC	(0.346±0.035)	(1.25±0.08)	(1.28±0.11)	(1.30±0.15)	(1.30±0.14)	(1.31±0.10)

图1 不同种类界面层纤维的SEM照片及EDS分析结果

Fig. 1 SEM and EDS microstructures of fibers with different interphases (a, b) As-received; (c, d) BN-coated; (e, f) BN/SiC-coated

图2 BN(a)和BN/SiC(b)界面层的XRD图谱

Fig. 2 XRD patterns of BN (a) and BN/SiC (b) interphase

图3 不同界面层的HRTEM照片

Fig. 3 HRTEM microstructures of different interphases (a) BN interphase; (b) SiC interphase

图4 不同种类界面层纤维的拉伸强度

Fig. 4 Tensile strength of SiC fibers with different interphases (a) Tested strength value; (b) Calculated strength value after deducting the thickness of interphases

图5 不同种类界面层纤维的弹性模量

Fig. 5 Elastic modulus of SiC fibers with different interphases

图6 VHPCS-1100 ℃热解产物的XRD图谱

Fig. 6 XRD pattern of the pyrolysis products from VHPCS at 1100 ℃

图7 不同界面层复合材料断口的SEM照片

Fig. 7 Cross-section morphologies of mini-SiCf/SiC composites with different interphases (a) No interphase, (b) BN interphase, (c) BN/SiC interphase

图8 Mini-SiCf/SiC复合材料载荷应变曲线

Fig. 8 The load-strain curves of Mini-SiCf/SiC composites

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