SiCxOy相分解方式对SiCO(Al)纤维烧结致密化的影响

doi:10.15541/jim20160066

摘要/Abstract

摘要：

研究了SiCO(Al)纤维向SiC(Al)纤维的高温转化过程, 并研究了纤维中SiC_xO_y相的分解特征及不同高温处理方式对纤维结构和烧结致密化的影响。结果表明: 纤维中SiC_xO_y相分解的温度范围为1430~1850℃, 当采用连续处理方式处理, 即使在1800℃下, 纤维芯部SiC_xO_y相未能彻底分解, 且快速分解速率导致纤维中形成粗大结晶颗粒和气孔, 无法得到致密的高结晶结构。而在静态条件下处理, 可以提高SiC_xO_y相分解程度。1650℃下保温处理1 h后可以完全脱除SiC_xO_y相, 同时保持晶粒均匀。再经过1900℃烧结, 即可制得呈致密高结晶结构SiC(Al)纤维。

关键词: SiCO(Al)纤维, SiC(Al)纤维, SiCxOy相, β, -SiC, 致密化

Abstract:

The transformation from SiCO(Al) fiber to SiC(Al) fiber by high temperature heat-treatment was studied. The characteristics of SiC_xO_y decomposition and effects of different heating approaches on microstructure and densification processing of SiCO(Al) fibers were investigated. It was found that SiC_xO_y phase typically decomposed at temperature ranged from 1430℃ to 1850℃. The SiC_xO_yphase in the core area of fiber could not be eliminated completely by continuous heat-treatment, even at the temperature as high as 1800℃. Furthermore, large pore faults and grain coarsening tended to generate in the fibers due to over-high decomposition rate, which led to loose structure of fibers. By contrast, static heat-treatment could increase the degree of SiC_xO_y decomposition. The SiC_xO_y phase could be completely removed when the fibers were heat-treated at 1650℃ for 1 h, and big pores and heterogenous grains were suppressed. Finally, densified SiC(Al) fibers with large β-SiC grains could be achieved after sintering at 1900℃.

Key words: SiCO(Al) fibers, SiC(Al) fibers, SiCxOy phase, β, -SiC, densification

中图分类号:

TQ343

袁钦, 宋永才. SiC_xO_y相分解方式对SiCO(Al)纤维烧结致密化的影响[J]. 无机材料学报, 2016, 31(12): 1320-1326.

YUAN Qin, SONG Yong-Cai. Effect of SiC_xO_y Decomposition on Densification of SiCO(Al) Fibers during Sintering Process[J]. Journal of Inorganic Materials, 2016, 31(12): 1320-1326.

图/表 10

表1 SiCO(Al)纤维的元素组成

Table1 Chemical compositions of SiCO(Al) fibers

Sample	Si/wt%	C/wt%	Al/wt%	O/wt%
SiCO(Al)	54.69	35.03	0.57	9.71

图1 SiCO(Al)纤维的29Si-NMR(a)和XRD(b)图谱

Fig. 1 29Si-NMR spectrum (a) and XRD pattern (b) of SiCO (Al) fibers

图2 SiCO(Al)纤维中氧含量和β-SiC晶粒尺寸随温度的变化曲线

Fig. 2 Oxygen content and β-SiC crystallite size of SiCO(Al) fibers vs. heated temperature

图3 经1800℃连续热处理后SiCO(Al)纤维的SEM照片

Fig. 3 SEM micrographs of SiCO(Al) fibers after continuously heat-treatment at 1800℃^(a) Surface (×8000); (b) Cross-section; (c) Surface (×30000); (d) EDS pattern of coarse grains on fibers

图4 SiCO(Al)纤维的TG-DTA曲线

Fig. 4 TG-DTA curves of SiCO(Al) fibers

图5 不同温度热处理SiCO(Al)纤维中氧含量随热处理时间的变化

Fig. 5 Oxygen content of SiCO(Al) fibers vs. holding time at various temperatures

图6 在不同温度热处理1h后SiCO(Al)纤维表面形貌

Fig. 6 Surface morphologies of SiCO(Al) fibers after heat- treatment at different temperatures for 1 h^(a,b) 1450℃; (c,d) 1550℃; (e,f) 1650℃; (g,h) 1700℃

图7 SiCO(Al)纤维经1650℃处理1 h后29Si-NMR曲线

Fig. 7 29Si-NMR spectra of SiCO(Al) fibers after heat-treated at 1650℃ for 1 h

图8 SiCO(Al)纤维经不同条件处理后的XRD图谱

Fig. 8 XRD patterns of SiCO(Al) fibers after heat-treatment under different conditions^(a) 1650℃-1h; (b) 1700℃-1h; (c) 1800℃-continuously heat-treatment

图9 SiCO(Al)纤维经不同温度处理后再经1900℃烧结所得SiC(Al)纤维表面形貌

Fig. 9 Surface morphologies of SiC(Al) fibers prepared from SiCO(Al) fibers preheated at different temperature and then sintered at 1900℃^(a,b) Preheated at 1650℃; (c,d) Preheated at 1700℃

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