Al、O含量对SiAlCO纤维高温转化为Si(Al)C纤维过程的影响

doi:10.15541/jim20150402

摘要/Abstract

摘要：

采用不同Al含量的聚铝碳硅烷(PACS)为先驱体, 通过不同的PACS纤维不熔化方法调节O引入量, 制备了具有不同Al和O含量的连续SiAlCO纤维。研究了SiAlCO纤维经高温处理转变为Si(Al)C纤维过程中, Al、O含量对SiC_xO_y相分解、β-SiC结晶生长和微观形貌的影响。结果表明: 纤维中SiC_xO_y相的分解温度区间为1300~1700℃, 与Al、O含量基本无关; 提高Al含量可减少纤维在高温下表面形成粗大SiC结晶颗粒和相互连通的气孔, 并且对1700℃以上β-SiC结晶生长的抑制作用增强, 有利于烧结致密化; 利用纤维中O元素, 以放出CO或CO₂方式脱除富余C, 但O含量过高导致气体逸出时产生较大孔洞, 不利于烧结致密化。当Al和O含量分别约为0.6wt%和9wt%时, SiAlCO纤维经高温处理后能得到具有较大β-SiC晶粒尺寸的致密化Si(Al)C纤维。

关键词: SiAlCO纤维, SiCxOy相分解, β-SiC, 致密化, Si(Al)C纤维

Abstract:

Continuous SiAlCO fibers were prepared by polymer-derived method using polyaluminocarbosilane (PACS) with various Al contents as precursor. The O content of the fibers was controlled by different curing methods. The effects of the Al and O content on SiC_xO_y decomposition, β-SiC grain growth, and fiber morphological evolution in the heat-treatment process were investigated. The results reveal that SiC_xO_y decompostion initiates at 1300℃ and completes at 1700℃ for all kinds of fibers, which is irrelevant to Al and O contents. Al in the fibers is beneficial to reduction of both coarse SiC crystallites and interconnected pores on the surface, and increases suppressing effects on the growth of β-SiC under the tempertature above 1700℃, resulting in densification. Excessive carbon is eliminated as CO and CO₂ by oxygen from SiAlCO fibers during annealing process. However, excessive oxygen creates big pores in fibers, harmful to densification. A densified Si(Al)C fiber with a decently large crystallite size of β-SiC can be achieved with an optimal Al and O content of 0.6wt% and 9wt%, respectively.

Key words: SiAlCO fibers, SiCxOy decomposition, β-SiC, densification, Si(Al)C fibers

中图分类号:

TQ174

袁钦, 宋永才. Al、O含量对SiAlCO纤维高温转化为Si(Al)C纤维过程的影响[J]. 无机材料学报, 2016, 31(4): 393-400.

YUAN Qin, SONG Yong-Cai. Effects of Al and O Content on Transformation from SiAlCO to Si(Al)C Fibers after High Temperature Treatment[J]. Journal of Inorganic Materials, 2016, 31(4): 393-400.

图/表 11

表1 SiAlCO纤维的元素组成

Table1 Chemical compositions of SiAlCO fibers

Sample	Oxidation temperature before EB/℃	Si/wt%	C/wt%	Al/wt%	O/wt%	C/Si
SiAlCO2-6	-	57.27	36.71	0.24	5.78	1.496
SiAlCO2-9	160	55.88	35.08	0.20	8.84	1.465
SiAlCO2-13	190	54.16	32.21	0.22	13.41	1.388
SiAlCO3-6	-	55.20	36.93	0.33	7.54	1.561
SiAlCO3-9	160	54.77	35.42	0.33	9.48	1.509
SiAlCO3-13	190	53.63	33.02	0.36	12.94	1.437
SiAlCO6-6	-	55.77	36.27	0.62	7.36	1.517
SiAlCO6-9	160	54.69	35.03	0.57	9.71	1.495
SiAlCO6-13	190	54.10	32.69	0.53	12.68	1.410

图1 SiAlCO2-9纤维表面(a)和断面(b)的SEM照片

Fig. 1 Surface (a) and cross section (b) SEM images of SiAlCO2-9

图2 SiAlCO纤维的29Si-NMR图谱

Fig. 2 29Si-NMR spectra of SiAlCO fibers

图3 不同Al含量SiAlCO纤维中氧含量随热处理温度的变化

Fig. 3 Oxygen content of SiAlCO fibers with different Al contents vs heat-treatment temperature

表2 1700℃处理后SiAlCO纤维的元素组成

Table2 Chemical compositions of SiAlCO fibers after heat-treatment at 1700℃

Sample	Si/wt%	C/wt%	O/wt%	Al/wt%	C/Si
SiAlCO2-6	62.53	37.27	0.06	0.39	1.396
SiAlCO2-9	65.72	33.80	0.04	0.44	1.200
SiAlCO2-13	68.73	31.07	0.02	0.48	1.060
SiAlCO3-6	62.31	37.36	0.15	0.47	1.406
SiAlCO3-9	63.33	36.34	0.04	0.57	1.345
SiAlCO3-13	66.97	32.70	0.03	0.64	1.145
SiAlCO6-6	62.03	37.11	0.11	0.75	1.396
SiAlCO6-9	63.02	36.06	0.08	0.84	1.335
SiAlCO6-13	65.55	33.50	0.04	0.91	1.222
Tyranno SA(edge)^[12]	68.00	31.30	-	0.50	1.080
Tyranno SA(core)^[12]	62.90	36.10	0.40	0.60	1.340

图4 经不同温度热处理后SiAlCO6-9纤维的XRD谱图

Fig. 4 XRD patterns of the SiAlCO6-9 fiber after heat- treatment at different temperatures

图5 不同Al含量SiAlCO纤维中β-SiC晶粒尺寸随热处理温度的变化

Fig. 5 β-SiC crystallite size of SiAlCO fibers with different Al content vs heat-treatment temperature

图6 不同温度热处理后β-SiC晶粒尺寸随Al含量的变化

Fig. 6 β-SiC crystallite size varied with Al content for the SiAlCO fibers after heat-treatment at different temperatures

图7 1700℃处理后SiAlCO纤维表面SEM照片

Fig. 7 Surface morphologies of SiAlCO fibers after heat-treatment at 1700℃ (a)-(c) SiAlCO2-6~SiAlCO2-13, (d)-(f) SiAlCO3-6~SiAlCO3-13, (g)-(i) SiAlCO6-6~SiAlCO6-13

图8 1900℃烧结后SiAlCO3-13纤维的表面形貌

Fig. 8 Surface morphologies of SiAlCO3-13 fiber after sinterment at 1900℃

图9 1900℃处理后SiAlCO纤维的表面形貌

Fig. 9 Surface morphologies of SiAlCO fibers after heat-treatment at 1900℃ (a) SiAlCO6-6, (b) SiAlCO6-9, (b) SiAlCO6-13

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